MINISTRY OF

EDUCATION AND TRAINING

VIETNAM ACADEMY OF

SCIENCE AND TECHNOLOGY

GRADATE UNIVERSIY OF SCIENCE AND TECHNOLOGY

LE THE TAM

STUDY ON THE FABRICATION OF MAGNETIC FLUIDS BASED ON

SUPERPARAMAGNETIC IRON OXIDE NANOPARTICLES (SPIONs)

APPLIED TO MAGENTIC RESONANCE IMAGING (MRI)

APPLICATION

Major: Inorganic chemistry

Code: 9.44.01.13

SUMMARY OF CHEMISTRY DOCTORAL THESIS

Ha Noi - 2019

This thesis was done at:

Laboratory of Biomedical Nanomaterials, Institute of Materials and Sciene,

Vietnam Academy of Science and Technology.

Laboratory of Electronic-Electrical Engineering, Institute for tropical

technology, Vietnam Academy of Science and Technology.

Centre for Pratices and Experimences, Vinh University.

Supervisor: Prof., Dr. Tran Dai Lam

Assoc.Prof., Dr. Nguyen Hoa Du

Reviewer 1: .....................................................

Reviewer 2: .....................................................

Reviewer 3: .....................................................

The dissertation will be defended at Graduate University of Science and Technology, 18

Hoang Quoc Viet street, Hanoi.

Time: .............,.............., 2019

This thesis could be found at National Library of Vietnam, Library of Graduate

University of Science and Technology, Library of Chemistry, Library of Vietnam

Academy of Science and Technology.

INTRODUCTION

Recent applications of magnetic nanoparticles in biomedical applications, especially in

imaging diagnostics using MRI Magnetic Resonance Imaging engineering have attracted the

attention of scientists around the world. Currently in imaging diagnostics using MRI magnetic

resonance imaging, Tl contrast agents have become a traditional commodity, which is a

complex of paramagnetic ions with a large torque value like Gd3+ (7 unpaired electrons).

These Gd3+ ions are combined with molecules such as DTPA (diethylentriamine penta acetic

acid) and create Gd-DTPA chelate round complex structures. During the recovery process,

the interaction between the magnetic moment of the proton and the magnetic moment of the

paramagnetic ions causes the T1 time to be reduced, so the recovery rate R1 increases. The

concentration of agents is different in each cell tissue region, thus providing an effective

contrasting on MRI images. For nearly 10 years now, along with the development of

nanotechnology iron oxide (IO) nanoparticle having been strongly researched and actual

many commercial products that increase MRI contrast levels using this iron oxide material,

proving that iron oxides-MRI can give better quality of contrast level than Gd-DTPA because

iron oxide particles have a higher magnetic induction coefficient. IO-MRI substances can

reduce both T1 and T2, increasing MRI recovery rates in both Tl and T2 MRI modes. The

important requirements for MRI contrast increasing products are that magnetic nanoparticles

must have a relatively uniform particle distribution and magnetic saturation enough large, and

the coating materials must have good biological compatibility. While some commercial

products in the world, such as Resovist, use dextran as a coating material, with a 65 nm core

particle created from saturation of about 65 emu/g. Products with particle sizes in the 20-

40nm region such as AMI-227: Sinerem/Combidex are suitable for lymph and bone. In the

last 10 years, people have been studying to create superparamagnetic nanoparticles with a

particle size smaller than 20 nm (also known as microscopic if the particle size is D<10 nm)

and especially iron oxide particles, marked with magnetic markers is intended for MRI

targeted imaging.

In Vietnam, up to now the fabrication of nanoparticles in general and magnetic

nanoparticles in particular has been focused to research in accordance with two aspects: basic

research and application-orientation research. The profound research results are published

mainly from large research institutions such as: Hanoi National University, Hanoi University

of Science and Technology and Vietnam Academy of Science and Technology. The synthesis

of magnetic nanomaterials is mostly carried out in water and by synthetic methods such as

co-precipitation methods, hydrothermal methods, microwave methods and ultrasonic

electrochemical synthesis methods. Due to the synthesis in the water environment, the

fabricated magnetic nanoparticles have not high quality, the particles are uneven in size and

heterogeneous in shape and therefore they are restricted for use in vivo printing applications

in biomedicine such as used as a contrast drug in imaging diagnosis by MRI magnetic

resonance imaging, magnetic induction heating, etc. in addition, the such unevenness even

affects the research results of their magnetic properties. Therefore, up to now, the selection

of conditions in the fabrication of Fe3O4 nano magnetic fluid to produce particles with small

particle size, uniform distribution, homogeneous shape and high durability, high magnetism

and high biocompatibility, thus making it possible to apply as contrast medicine in imaging

diagnostics using MRI magnetic resonance imaging, creating optimal values of impulses TR,

TE when taking with T1, T2 mode, and determining recovery coefficient r1, r2 to assess the

quality of magnetic fluids as contrast medicine in imaging diagnosis by MRI magnetic

resonance imaging is still asking for continuing and systematic research.

Derived from the research on nanomaterials in the world as well as in Vietnam, based

on the research and Doctor training potential of the Institute of Science and Technology,

Vietnam Academy of Science and Technology, under the guidance of a group of experienced

scientists, we select the topic "Study on the fabrication of magnetic fluids based on

superparamagnetic iron oxide nanoparticles (SPIONs) applied to magentic resonance

imaging (MRI) application" to make this thesis content.

Research object of the thesis:

Magnetic fluid system based on superparamagnetic iron oxide.

Research targets of the thesis:

The goad of the thesis is to build the manufacture process of nano-sized magnetic fluids

based on iron oxide (uniform particle size and high magnetic saturation) with stable

technology; Characteristic research of magnetic properties of magnetic nanoparticles;

assessment of toxicity and test of effects on cells, aiming to make contrast medicine in

imaging diagnosis by magnetic resonance imaging (MRI), application on accurately

identifying cancer.

Scientific and practical meaning of the thesis:

The implementation organization of the topic itself has important implications for

developing a multi-disciplinary science and technology direction as Nanotechnology for

Medicine. There will be academic exchange, mutual learning between research groups in the

industries deem as independent. Scientifically, the magnetization of magnetic particle systems

for biomedical applications is strongly influenced by many factors, but the mechanism of

these effects is still a problem that has not been studied fundamentally.

For the application of cancer diagnosis and treatment, nanotechnology in general is

creating a great expectation that is able to contribute to solve the problem of early disease

diagnosis and drugs to target or intervention areas localized at the destination. The subject has

a goal of using magnetic fluid improving the contrast of nuclear magnetic resonance imaging

(MRI), which can contribute to the analysis of early-stage cancer tissue.

Research methodology:

The thesis is conducted by experimental method combined with numerical calculation

techniques. The research sample is fabricated by hydrothermal and thermal decomposition

methods. Study the structure of the sample by X-ray diffraction techniques (XRD), electron

microscopy (FESEM, TEM and HRTEM). The magnetic properties of the materials are

surveyed by magnetic measurements on the vibrating sample magnetometer (VSM) system.

Using Fourrier Transformation InfraRed (FTIR), Thermal gravimetric analysis (TGA) to

evaluate the presence of functional groups on the particle surface and the mass reduction of

polymer-coated magnetic particle layer. Dynamic Light Scattering (DLS) technique

determines the hydrodynamic size and durability of magnetic fluids. Experimental assessment

of toxicity through in-vitro test. MRI imaging method T1, T2 for studies of contrast

enhancement of material samples for manufacturing (on 1.5T MRI scanner, SIEMENS

MAGNETOM, Germany).

Research contents of the thesis:

1. Successful summary of Fe3O4 magnetic nanoparticles with uniform particle size and

high saturation magnetization by hydrothermal and thermal decomposition methods.

2. Successfully fabrication of high-strength magnetic fluids on Fe3O4 particles

synthesized by the above two methods.

3. Research on the toxicity and durability of magnetic fluids.

4. Study the applicability of image contrast enhancer in MRI magnetic resonance

imaging.

The layout of the thesis:

The thesis has 137 pages (not including references, appendices), including the

introduction, 5 chapters of content and conclusions.

The main results of the thesis are published in 09 published projects, including 01 article

published under SCI list, 01 article sent from SCI list submitted and reviewing, 05 articles on

National magazine, 01 article published in the Proceedings of the National Science

Conference, and registered 01 intellectual property (SC) has been published in the volume A

Industrial Ownership Gazette.

Main results of the thesis:

The influence and optimization of technological conditions on the structure and

magnetic properties of chitosan-coated Fe3O4 nanoparticles (CS) were investigated using

hydrothermal method.

Successfully fabricated magnetic fluids based on Fe3O4 particles by thermal

decomposition method by phase transformation and coating by polymer PMAO.

Fe3O4@PMAO liquid samples are highly durable in different conditions, single-dispersed,

uniform particles.

Evaluation of the toxicity of magnetic fluids on typical samples with different cell lines,

results are good IC50 index. Manufactured fluid Samples are not cytotoxic, which is the basis

for conducting subsequent experiments on animals.

Determined the relaxation rate of nuclear magnetic resonance imaging (MRI) of 2

systems Fe3O4@CS, Fe3O4@PMAO showed that the uniform fabrication systems have high

r2 values of over 150 mM-1s-1 for samples of Fe3O4@PMAO, higher than commercial products

Resovist. These substances, when given MRI imaging tests, show good potential for

applications to increase contrast.

In vitro, ex-vivo and in-vivo studies of MRI contrast enhancement showed that many of

the magnetic fluids of the manufacturing subject group exhibited good contrast enhancement.

Applying the Fe3O4@PMAO system to solid tumors under the skin and liver tumors, shows

the potential for observing the detailed shape and structure of the tumor, supporting diagnosis

and treatment.

CHAPTER 2. REVIEW OF SPINEL FERRITE MATERIAL AND MAGNETIC

RESONANCE IMAGING METHOD BY MRI SHOOTING ENGINEERING

1.1. The structure and magnetic properties of spinel ferrite materials

1.1.1. Structure of spinel ferrite

Ferrite spinel is the term used to refer to a material with a two-subnetwork structure of

which interactions are antiferromagnetic or magnetic ferrite. A basic cell unit of spinel ferrite

(with crystal lattice constant a ~ 8.4 nm) is formed by 32 atoms O2- and 24 cation (Fe2+, Zn2+,

Co2+, Mn2+, Ni2+, Mg2+, Fe3+ và Gd3+). In a base cell there are 96 positions for cations (64 in

octahedral position, 32 in tetrahedral position). The number of cations is more octahedral in

the tetrahedral position (A), in particular there are 16 cations occupied in the octahedral

position (B) while in the tetrahedral position there are only 8 cations (including valency cation

2+ or 3+).

1.1.2. Magnetic properties of spinel ferrite materials

According to molecular field theory, the magnetic origin in spinel ferrite materials is

due to the indirect exchange interaction between metal ions (magnetic ions) in two

subnetworks A and B through oxygen ions.

1.1.3. Magnetism of nanometer-sized particle magnetic materials

The superparamagnetic phenomenon (or status) occurs for ferromagnetic materials

composed of small crystalline particles. When the particle size is large, the system will be in

the multidomain state (i.e. each particle will be composed of many magnedomain particles).

When the particle size decreases, the substance will turn into a mono-state, which means that

each particle will be a dime. When the particle size decreases too small, the directional energy

(which predominantly dominates are that the crystal magnetic anisotropic energy is much

smaller than the thermal energy, then the thermal energy will break the parallel orientation of

magnetic moments) and then the magnetic moment of the particle system will orient

chaotically as in paramagnetic material.

1.2. The studying situation of nanomaterials in the domestic and abroad

In Vietnam, a number of research groups at the Institute of Materials Science,

International Training Institute for Materials Science - Hanoi University of Science and

Technology and Hanoi National University (VNU) have also announced their manufacture of

magnetic nanoparticles for biomedical applications and for basic research.

1.3 . Manufacture methods of magnetic fluids

1.3.1. Synthesizing methods of magnetic nanomaterials

For biomedical applications, the material is often made by a number of chemical

methods such as co-precipitation, solgel, microemulsion, hydrothermal, thermal

decomposition, microstorage, etc. Chemical methods can create nanoparticles with a quite

high uniformity and facilitate to be able to coat particles and transfer phase of the particles

from oil to water. Each of the above methods has different characteristics.

1.3.2. Particle coating technologies in water solvent

For nanoparticles synthesized by chemical methods in water solvents, the coating of

the particles or the functionalization of the nanoparticle surface after fabrication is a very

important factor to ensure both magnetic properties and biological compatibility. When

the surface is coated and functionalized, the nanoparticles easily disperse in a suitable

solvent and become homogeneous colloidal particles called magnetic fluids.

1.3.3. The process to transfer the phase from organic solvents to water solvents

In order to obtain high-quality magnetic nanoparticles, sample fabrication is usually

carried out in organic solvents at high boiling temperatures such as: benzyl ther, phenyl ether,

octadecene...Therefore, before being able to be used in Biomedical, these magnetic

nanoparticles need to be transferred from organic solvents to water solvents through phase

transfer processes.

1.4. Application of magnetic nanoparticle systems in biomedical

Magnetic nanoparticles have the potential to be applied in many different fields. In

biomedical, magnetic nanoparticles can be used to extract biological molecules using

magnetism, nano curcumin, and substances increasing contrast in magnetic resonance

imaging (MRI) and magnetic burning application for cancer treatment. However, this thesis

focuses on researching magnetic nanoparticle application orientation Fe3O4 to enhance

nuclear magnetic resonance imaging (MRI) affect.

CHAPTER 2. EXPERIMENTAL ENGINEERING

2.1. Summary of magnetic fluid system Fe3O4@CS by hydrothermal method

Magnetic nanoparticles Fe3O4@CS is synthesized by hydrothermal method according

to Figure 2.1 diagram.

Figure 2.1. Fabrication process of magnetic fluids Fe3O4@CS.

2.2. Summary of nanoparticle system Fe3O4@OA/OLA by thermal decomposition method

Nanoparticle system Fe3O4@OA/OLA is synthesized by thermal decomposition method

according to Figure 2.2 diagram.

Figure 2.2. Fabrication process of magnetic nanoparticles Fe3O4@OA/OLA.

2.3. Transfer the phase of nanoparticles slowly from organic solvents to water solvents

The phase transfer process of magnetic nanoparticles from organic solvent to water is

carried out according to the diagram of Figure 2.3.

F e 3 O 4

F e 3 O 4

F e 3 O 4

Figure 2.3. PMAO encapsulation process.

2.3. Typical methods

Study the structure of the sample by X-ray diffraction techniques, electron microscopy.

Magnetic properties are surveyed by magnetic measurements on vibrating sample

magnetometer system. Using infrared absorption spectra, weight analysis to assess the

presence of functional groups on the particle surface and the mass reduction of the magnetic

particle-coated polymer layer. Dynamic laser scattering technique determines the

hydrodynamic size and durability of magnetic fluids.

2.4. Experimental planning method

In experimental chemical and chemical technology studies, there are many experimental

problems described as extreme problems: determining the optimal conditions of the process,

the optimal composition of the mixture... Experimental planning allows to simultaneously

change all the factors that affect the process and allow quantitative evaluation of basic effects

and simultaneous interaction effects of the elements, thereby optimizing chemical

technologies.

2.5. Evaluate the toxicity of fluids from cancer cells

Evaluate potentially lethal the cancer cells and healthy cells and intact cells of fabricated

magnetic fluid.

2.6. Testing the ability to contrast agent in MRI imaging techniques

MRI imaging experiment in T1, T2 is used for the researches of image contrast

enhancement of images of manufacturing materials (on 1.5T MRI scanner, SIEMENS

MAGNETOM, Germany).

CHAPTER 3. RESEARCH MAGNETIC FLUID BASED ON MAGNETIC IRON

OXIDE SYTHETISED BY HYDROTHERMAL METHOD

3.1. Implement the optimal three-level quadratic experimental planning

Table 3.1. Levels of independent variables and experimental conditions

Run

Variable levels Temperature 0C

Time (h)

Concentration Fe3+ (M)

Ms (emu/g) A B C

1 + + - 180 4,00 0,1 34,73 2 + - + 180 2,00 0,25 53,22 3 - + + 120 4,00 0,25 61,89 4 - - - 120 2,00 0,10 57,26 5 -1,414 0 0 107,57 3,00 0,17 55,38 6 1,414 0 0 192,43 3,00 0,17 63,21 7 0 -1,414 0 150 1,59 0,17 61,4 8 0 1,414 0 150 4,41 0,17 60,07 9 0 0 -1,414 150 3,00 0,07 46,67 10 0 0 1,414 150 3,00 0,28 59,96 11 0 0 0 150 3,00 0,17 66,67 12 0 0 0 150 3,00 0,17 63,32 13 0 0 0 150 3,00 0,17 64,68

Factor Giá trị F p

-value prob > F

Model 35.75 0,0068a

A 10.64 0,0038a

B 7.31 0,0457b

C 30.64 0,0116b

AB 9.27 0,0308b

AC 76,96 0,0031a

BC 5,83 0,0346b

A2 33,46 0,0103b

B2 21,85 0,0185b

C2 107,69 0,0019a

R2=0,9908

Figure 3.2. Analysis of variance (ANOVA) for full quadratic model and Model coefficient

estimated by linear regression (asignificant at 1% level; bSignificant at 5% level).

Figure 3.3. Surface plot and contour plot of the combined effects of A and B (a); A and C

(b) on the yield of Ms at another coded level of zero

0

0.01

0.02

0.03

0.04

0.05

B

AC

AB

B2 C

A2 A BC

C2

p-v

alu

e

Variable

The suitability analysis of the model and the significance of the model assessed by

ANOVA analysis (Figure 3.2) and correlation indicators. The significance of the regression

coefficients is tested by standard F, with values p<0.05 indicating significant regression

coefficients. Thus, in Figure 3.2 found that the value of "Model F-value" is 35.75, the model

is completely statistically significant with 99.08% reliability. With all the factors of sample

incubation temperature, time, Fe3+ concentration and each pair of these factors have a value

of p<0.05, indicating that each of these factors also interact with each other and are

meaningful (Figure 3.2), this is illustrated more clearly when observing the response surface

in Figure 3.3.

Figure 3.4 describes the fit line according to the Langevin function of the samples at

optimal conditions M11 - M13 at the magnetism at the magnetism 10 kOe. Throught this

figure, the experimental data on the M(H) base line of all samples measured at 300K

temperature closely matched according to Langevin function with high accuracy (R2> 0.998).

Figure 3.4. Experimental and fitting hysteresis curves of the Fe3O4@CS nanoparticles (inset

is the enlarged hysteresis curve).

3.2. Structural and morphological characteristics of magnetic nanoparticles Fe3O4@CS

(a) (b) (c)

Figure 3.5. X-ray diffractions (a) and và FTIR spectrum (b) and TGA analysis (c) of Fe3O4,

CS and Fe3O4@CS samples.

Figure 3.5a shows all the diffraction lines of the samples coincide with the standard lines

of Fe3O4 with spinel structure. The combination with Chitosan makes the pics of the Fe3O4@CS

nano sample more noise than the pics of pure Fe3O4 samples but does not change the crystal

structure. Figure 3.5b (a) shows that, on the infrared spectrum of the sample Fe3O4@CS, there

are characteristic oscillations related to functional groups of Fe3O4 particles and CS cover. This

proves that Fe3O4 nanoparticles were covered by CS.

On TEM image (Figure 3.6), the spherical shaped particles with small size from 12-18 nm

and relatively uniform, the particles after covering Fe3O4@CS are larger than those of Fe3O4

before covering. However, the particles when dispersed in water have not been dispersed simple

shape, the groups have shinking phenomenon with the organic chitosan shell about 21.5%

(Figure 3.5c).

Figure 3.6. TEM images of the magnetic fluids Fe3O4@CS prepared by optimization

3.3. Characteristics of Fe3O4@CS magnetic fluid system durability

Figure 3.7. Hydrodynamic size distribution of Fe3O4@CS magnetic fluid at a) different pH of 2,

4.5, 7.4, 11.5 and 12 and b) different NaCl concentrations of 0, 50, 100, 200, and 300 mM.

By determining the strength of a sample of Fe3O4@CS fluid in a physiological field,

the fluid sample has a high durability in a wide pH range, long time and high strength when

the salt content is up to 300 mM. This shows that the samples of Fe3O4@CS fluid have suitable

properties in biomedical conditions.

3.4. Test and evaluation of the toxicity of chitosan-coated Fe3O4 magnetic fluid system

Figure 3.8. Sarcoma 180 cell’s viability after incubating with different concentration of

Fe3O4@CS MNPs after 48h: (C1): 500 µg/ml, (C2): 250 µg/ml, (C3): 125 µg/ml, (C4): 62,5

µg/ml, (C5): 30,25 µg/ml and (C6): 15,125 µg/ml. All presented values were expressed as

mean±standard deviation (SD) (a) and Observation of Sar.180 cells morphology under the

different concentrations of Fe3O4@CS using inverted microscope. CA: control with culture

medium. CB: control with DMSO. Objective lens: 20X, zoom: 5.6.

The results of MTT testing are shown in Figure 3.8, whereby Fe3O4@CS nanomagnetic

fluids are not toxic to Sarcoma 180 cells with 83% - 106% of survival cells after 48 hours of

incubation with nanomagnetic fluids with concentrations of 15.125 µg/ml and 30.25 µg/ml.

When increasing the concentration of nanoparticles up to 62.5 µg/ml, 125 µg/ml, 250 and 500

µg/ml, the rate of survival cells decreased respectively to 66.1%, 38.4%, 17.8% and 2.8135%.

Accordingly, the toxicity of the Fe3O4@CS nanomagnetic product is linear with concentration

when the increase in magnetic fluid concentration leads the reduction of cell growth. From

the in vitro test results and comparing with recent publications, it can be concluded that

chitosan- coated magnetic nanomaterial Fe3O4@CS are not toxic to Sarcoma 180 mouse

cancer cell line.

CHAPTER 4: STUDYING THE MAGNETIC FLUID SYSTEM BASED ON IRON

OXITE SYNTHETIZED BY THE THERMAL DECOMPOSITION METHOD

4.1. Effect of solvent and temperature on properties of Fe3O4 particle

Figure 4.1. TEM images of Fe3O4 synthesized at different reactions solvent and temperature

of 1 hours.

By surveying the effect of temperature, it was found that the sample was made at a

temperature lower than the solvent temperature for particles of small, uneven, and grainy size.

Dibenzyl ether solvents give heterogeneous particles in shape, uneven size compared to

octadecene solvents. Particles of uniform size with grain boundaries are more clear when the

reaction temperature is increased to 300 to 310 oC and 320 oC. This indicates that the

temperature and nature of the solvents are important factors in the formation and development

of particles.

Figure 4.1. The M(H) curves of Fe3O4 synthesized at different reactions solvent (inset is the

enlarged hysteresis curve)

The value from Ms saturation increased from 51 emu/g (OIO-DIO1) to 59 emu/g (OIO-

DIO2) and 62 emu/g (OIO-DIO3) when changing the reaction temperature from 270oC đến

310oC (Figure 4.1c).

4.2. Effect of reaction time on magnetic structure and properties

Figure 4.2. TEM images of Fe3O4 synthesized at different reaction times

Figure 4.2 shows that all models are composed of cubic and spherical particles with

relatively uniform dimensions. The average particle size (DXRD) of samples increased from

5.2 nm to 11.2 nm corresponding to reaction time increased from: 0.5 hours to 2 hours.

Looking at TEM images, we find that grain boundaries become more pronounced when

reaction time increases.

Figure 4.3 shows the magnetization curves of fabricated Fe3O4 samples with different

reaction times. Thus, by changing the reaction time, the single-phase Fe3O4 nanoparticles

samples have the size from 7.52 nm to 13.15 nm correspond to the price magnetic values

increased from 53 emu/g to 65 emu/g. However, prolonged time can lead to large particle size

so that the value of magnetic coercivity is large and may not reach superparamagnetic state.

Figure 4.3. The M(H) curves of Fe3O4 synthesized at different reactions times (inset is the

enlarged hysteresis curve) (a) and HRTEM images of OIO-DIO5 samples (b).

4.3. Manufacturing magnetic fluids containing Fe3O4 magnetic nanoparticles coated

with PMAO

(a) (b)

Figure 4.4. Fe3O4 nanoparticle before and after encapsulating PMAO in hexane and water

(a); HRTEM images of Fe3O4 nanoparticles before and after encapsulating PMAO (b)

F e 3 O 4

F e 3 O 4

F e 3 O 4

Figure 4.4a is a photograph of the sample before and after the phase transfer with PMAO

in n-hexane and water solvent. It can be seen that the sample before coating PMAO is

dispersed very well in hexane and completely not dispersed in water. After coating PMAO,

the surface of Fe3O4 particles becomes hydrophilic and disperses well in water, not dispersed

in hexane. Thus, it can be determined that the polymer layer has covered the surface of the

particles and helps them stabilize and disperse well in water.

Hình 4.5. TEM images of Fe3O4 nanoparticles encapsulating PMAO after dilution solvent.

Observation of TEM and HR-TEM images in Figure 4.4 and Figure 4.5 showed that the

coated samples still have spherical shape, with uniform- distributed particle size. The particle

size of the coated samples is larger than the particle size of the original sample, corresponding

to the average size of 9.6 nm and 12.1 nm.

Figure 4.6. The M(H) curves of Fe3O4, Fe3O4@PMAO samples (a); FTIR spectrum of

Fe3O4, Fe3O4@OA, OLA and Fe3O4@PMAO (b)

From Figure 4.6, it can be seen that the experimental data on the M(H) base line of the

uncoated sample (Fe3O4) and the fluid sample contains of Fe3O4@PMAO particles

completely follow Langevin function, it can be assumed that these magnetic fluid samples is

superparamagnetic at room temperature.

Figure 4.7. The zeta potential scanning of the nanoparticles dispersed in fluids at different

times: for 0 day (a), 3 months (b), 6 months (c) of the Fe3O4@PMAO MNPs.

The responsiveness on durability in body physiology environment is also one of the

requirements for magnetic nanoparticles for biomedical applications. As we know, the salt

concentration in the body remains in the range of 165 ÷ 180 mM, pH ~ 7.5. Therefore, we

investigated the strength of the phase-transferred samples in physiological salt medium with

concentrations of 100 mM, 200 mM, 250 mM and 300 mM, respectively, with a pH of 7.5.

The survey results show that synthetic PMAO coated particles completely meet the durability

requirements for biomedical purposes.

Figure 4.8. The Zeta potential of PMAO coated Fe3O4 NPs dispersed in fluids at different

NaCl concentrations.

4.4. Test and evaluation of the toxicity of Fe3O4 phase-transferred and PMAO coated

fluid system

Figure 4.9. The toxicity of Fe3O4 phase-transferred and PMAO coated fluid system to cells line

Hep-G2, MCF-7 and RD. The cells incubated with Fe3O4 25 µg/ml. Objective lens: 40X.

Cellular toxicity of the PMAO magnetic nanomaterials system is assessed on three

human cancer cell lines Hep-G2, MCF-7, RD and a healthy cell line from Vero using the

Sulforhodamine B (SRB) method. Results of SRB analysis on the four cell lines shown in

Figure 4.9 showed that DMSO at the test concentration did not have a toxic effect on the cell

with 100% of proliferating cells while the standard matter in the positive check sample is

nearly exterminated all cancer cells rightly after 72 hours and inhibit strong overgrowth for

healthy cells. Compared with the results of incubation disc and Fe3O4@PMAO magnetic

nanoparticles, the values were almost unchanged against solvent control with the rate of

overgrowth cells on the cell lines Hep-G2, MCF-7, RD and Vero are 95.45%, 99.64%,

99.63% respectively in 100%. Thereby, it was concluded that the Fe3O4@PMAO system has

absolutely no toxic effect on these four cell lines. This shows that Fe3O4@PMAO materials

have great potential in image diagnosis and cancer treatment applications.

CHAPTER 5: REHABILITATION CHARACTERISTICS R1, R2, TOXIC TEST

AND EVALUATION OF IMAGE CONTRAST WITH MRI MAGNETIC

RESONANCE IMAGING

5.1. Evaluation of the recovery rate r1, r2 of the magnetic fluid system

Figure 5.1 and Figure 5.2 are magnetic resonance images of Fe3O4@PMAO fluid

samples at concentrations of 2.5 µg/ml, 5.0 µg/ml, 10 µg/ml, 15 µg/ml, 25 µg/ml and 30

µg/ml in T1, T2 mode in different shooting conditions of TR and TE values.

TE = 12; TR = 100 TE = 12; TR = 200 TE = 12; TR = 400

Figure 5.1. MRI images of the magnetic fluids samples by different concentrations taken by

the T1W status, TR= 100 ms (a), TR =200 ms (b), TR =400 ms (c), TE =12 ms with (A)

Fe3O4@PMAO, (B) Fe3O4@CS. The sample magnetic fluids prepared by different

concentrations of (1) 2,5 µg/ml, (2) 5,0 µg/ml, (3) 10,0 µg/ml, (4) 15,0 µg/ml, (5) 25,0 µg/ml

and (6) 30,0 µg/ml.

TE = 11; TR = 3970 TE = 23; TR = 3970 TE = 34; TR = 3970

TE = 57; TR = 3970 TE = 91; TR = 3970 TE=113; TR=3970

TE = 91; TR = 3970

Figure 5.2. MRI images of the magnetic fluids samples by different concentrations taken by

the T2W status, TE =11 ms (a), TE =23 ms (b), TE = 34 ms (c), TE= 57 ms (d), TE =91 ms

(e), TE =113 ms (f), TR =4000 ms with (A) Fe3O4@PMAO, (B) Fe3O4@CS in agarose

media 2%%. The sample magnetic fluids prepared by different concentrations of (1) 2,5

µg/ml, (2) 5,0 µg/ml, (3) 10,0 µg/ml, (4) 15,0 µg/ml, (5) 25,0 µg/ml and (6) 30,0 µg/ml.

From Figure 5.1 and Figure 5.2, we see that agar 2% check sample with white image

has a concentration of C = 0 µg/ml (there is no concentration of the fluid sample

Fe3O4@PMAO). Six white to black order images placed in the wells from left to right are

samples with corresponding concentrations: 2.5; 5; 10; 15; 25; and 30 µg/ml. The contrast

changes very clearly when changing a small amount of concentration of the sample

Fe3O4@PMAO. MRI image contrast agents have the same effect increasing the signal value

of T1 imaging mode (increasing the recovery speed along R1) and reducing the T2 signal

imaging mode (reducing the horizontal relaxation rate R2). The inverse of the recovery times

T1 and T2 is the recovery rate R1, R2. However, the increase or decrease ability of this signal

depends on the reversibility of ri (i = 1,2, corresponding to vertical recovery and horizontal

recovery) of each specific magnetic fluid. The reversibility of ri of magnetic fluids can be

determined from a linear relationship between Rx relaxation rate:

R1,2 = 1/T1,2 = Ro1.2 + r1.2.C (5.1)

Figure 5.3. Exponential decay curve for T2 signal intensity with increasing

concentration of Fe3O4@PMAO (a) Fe3O4@CS (b)

(a) (b)

Figure 5.4. The plot of T2 relaxation rate (1/T2) (a); (b) T1 relaxation rate of Fe3O4@CS

nanoparticles at 1.5 T for different Fe concentration.

Figure 5.1. Matching the dependent function of R1 and R2 to the fluid sample

concentration according to the expression (5.1) shows that this dependence is linear. From

Figure 5.1, we see that our phase-transferring magnetic fluid samples, coated with PMAO and

CS give a horizontal recovery much higher than the value of Resovist and some commercial

products. Thus, as expected, the fluid from superparamagnetic particles based on our Fe3O4

can be used as a MRI imaging contrast enhancer under a good T2 regime.

5.2. Evaluation of the in vitro magnetic resonance imaging contrast ability in different

environments

5.2.1. Evaluate the contrast ability in the water environment of magnetic fluids and Resovist

commercial products.

(a) (b)

Figure 5.5. MRI images of the magnetic fluids samples by different concentrations taken by

the T2W status, TE= 62 ms (a), TE =75 ms (b), TR =4000 ms with (A) Fe3O4@PMAO in

water, (B) Fe3O4@Dextran (Resovist) in water, (C) Fe3O4@CS, (D) control with water

(with the concentration C=0 µg/mL). The sample magnetic fluids prepared by different

concentrations of (1) 5,0 µg/ml, (2) 10,0 µg/ml, (3) 15,0 µg/ml, (4) 30,0 µg/ml, (5) 45,0

µg/ml.

When removing affect of factors such as protein and lipid from the cells, MRI image

in the water shows PMAO polymer coating Fe3O4 gives better contrast than T2, resovist give

better contrast than T1.

TE=15; TR=100 (a) TE=15; TR=400 (b)

Figure 5.6. MRI images of the magnetic fluids samples by different concentrations taken by

the T1W status, TR= 100 ms (a), TR =400 ms (b), TE =15 ms with (A) Fe3O4@PMAO in

water, (B) Fe3O4@Dextran (Resovist in water, (C) Fe3O4@CS; (D) control with water (with

the concentration C=0 µg/mL). The sample magnetic fluids prepared by different

concentrations of (1) 5,0 µg/ml, (2) 10,0 µg/ml, (3) 15,0 µg/ml, (4) 30,0 µg/ml, (5) 45,0

µg/ml.

From Figure 5.5, we see that the distilled water check sample in the final well series

(vertical column) with a white image has concentration of C = 0 µg/mL (no concentration of

fluid samples Fe3O4@CS, Fe3O4@PMAO, Resovist). Three ranges of top-down horizontal

wells were prepared in accordance with the concentrations of Fe3O4@PMAO, Resovist and

Fe3O4@CS hydrothermal samples with respective concentrations: 5, 10, 15, 30 and 45 µg/ml.

The contrast changes very clearly when changing a small amount of concentrations of

Fe3O4@CS, Fe3O4@PMAO as well as Resovist commercial products.

The difference in contrast in the T2W shooting mode (Figure 5.5) is very clear. It is

shown that the dark signal gradually increases with the concentration of nanomaterials in the

wells compared to biological control (well 6) as well as comparison between different

samples. At high concentrations such as 30 µg/ml of the Fe3O4@PMAO fluid sample, the

dark signal almost occupies the entire well, even if there is no bright signal (well No. 4) when

shooting in TE, TR mode appropriately, it shows that the Fe3O4@PMAO magnetic fluid

system has a higher saturation value, which gives better image contrast. Between two samples

Fe3O4@CS fabricated by hydrothermal and Resovist method, when shooting in T2W mode,

the contrast is compared to the check sample, the contrast image is similar.

5.2.2. Evaluation of contrast ability in changed pH environment of manetic fluid system

and Resovist commercial product.

TE=34; TR=3970 (c) TE=57; TR=3970 (d)

Figure 5.7. MRI images of the magnetic fluids samples by different concentrations taken by

the T2W status, TE= 11 ms (a), TE = 23 ms (b), TE =34 ms (c), TE =57 ms (d) with (A)

Fe3O4@PMAO in water, (B) Fe3O4@Dextran (Resovist in water. The sample magnetic

fluids prepared by the concentration incubated with Fe3O4 45.0 µg/ml of (1) pH =2, (2) pH

=3, (3) pH =7, (4) pH =9, (5) pH =12.

MRI images on different pH environments showed polymer-coated Fe3O4 gave better

contrast at T2 and the signal strength decreased sharply at pH = 7, resovist samples gave good

contrast at T2, lower signal strength (well No. 3).

TE=12; TR=100 (a) TE=12; TR=200 (b) TE=12; TR=400 (c)

Hình 5.8. MRI images of the magnetic fluids samples by different concentrations taken by

the T1W status, TR= 100 ms (a), TR = 200 ms (b), TR =400 ms (c), TE =12 ms (d) with (A)

Fe3O4@PMAO in water, (B) Fe3O4@Dextran (Resovist in water. The sample magnetic

fluids prepared by the concentration incubated with Fe3O4 45.0 µg/ml of (1) pH =2, (2) pH

=3, (3) pH =7, (4) pH =9, (5) pH =12.

The difference in image contrast in the T2W shooting mode (Figure 5.7) is shown more

clearly than in T1 mode (T1W) (Figure 5.8). It can be clearly seen that the signal the is almost

unchanged when increasing the pH value of the environment from 2 to 12. In the physiological

environment of the Fe3O4@PMAO fluid sample, the dark signal almost occupies the entire

well, even not also see a light color signal (well No. 3) when shooting in the appropriate TE,

TR mode, which shows that the Fe3O4@PMAO magnetic fluid system provides good image

contrast, equivalent to the suitable Resovist commercial product according to MRI

application.

5.2.3. Evaluation of contrast ability in environment with changing salt concentration of

magnetic fluid system and Resovist commercial product.

TE=57; TR=3970 (a) TE=75; TR=3970 (b) TE=87; TR=3970 (c)

Figure 5.9. MRI images of the magnetic fluids samples by different NaCl concentrations.

taken by the T2W status, TE =57 ms (a), TE =75 ms (b), TE 87 ms (c), TR =3970 ms with

(A) Fe3O4@Dextran (Resovist in water), (B) Fe3O4@PMAO in water, (C) control with

water. The sample magnetic fluids prepared by the concentration incubated with Fe3O4 45.0

µg/ml of (1) 50 mM, (2) 100 mM, (3) 150 mM, (4) 200 mM.

MRI images on the environment with different concentrations of salt showed that

polymer-coated Fe3O4 and resovist samples gave better contrast at T2 and good signal strength

even at high salt concentration environment (200 Mm). This shows that Fe3O4@PMAO fluid

samples have suitable properties in biomedical conditions.

TE=12; TR=100 (a) TE=12; TR=400 (b)

Figure 5.10. MRI images of the magnetic fluids samples by different NaCl concentrations.

taken by the T1W status, TR= 100 ms (a), TR =400 ms (b), TE =12 ms with (A)

Fe3O4@Dextran (Resovist in water), (B) Fe3O4@PMAO in water, (C) control with water.

The sample magnetic fluids prepared by the concentration incubated with Fe3O4 45.0 µg/ml

of (1) 50 mM, (2) 100 mM, (3) 150 mM, (4) 200 mM.

5.3. Survey of applicability of magnetic fluids on laboratory animals

5.3.1. In-vivo test assesses the applicability of nanomagnetic Fe3O4 fluid system as a

contrast drug in MRI magnetic resonance imaging technique in animals

MRI images on rabbits before and after injecting magnetic fluids were taken in different

types of shooting (SAGITAL and CORONAL), taken in T1 mode (vertical recovery) and

taken in T2 mode (horizontal recovery) shown in Figure 5.11 to Figure 5.12.

Hình 5.11. T1 weighted (Sagital) MR images showing rabbit liver (A) before injection of

contrast agent (B) after injection of contrast agent with TE= 9,2 ms, TR =659

Figure 5.11 and Figure 5.12 show that the image of rabbit parts before injection almost

are gray, not clearly distinguish the boundary of the internal organs of Rabbit. After injecting

Fe3O4@PMAO magnetic fluid, it shows that image in T1 ode has a slight change in contrast

intensity.

Figure 5.12. T2 weighted (Sagital) MR images showing rabbit liver (A) before injection of

contrast agent (B) after injection of contrast agent with TE= 94 ms, TR =3571 ms

The results showed that after 10 minutes of injection (the Fe3O4@PMAO magnetic fluid

sample) the internal organs of rabbits on MRI images showed more clearly than the MRI

images before injecting drugs. Compared to MRI images taken in T1 mode, MRI images taken

in T2 mode give much clearer contrast. At liver tissue position, when taking T1 mode with TR

= 659 ms, TE = 9.2 ms with spin-echo impulse, the brightness and darkness of images in liver

tissue are almost unchanged with the intensity ratio signal before injection Ia = 325 and signal

strength after injection Ib = 369. While taking image under T2 mode (TR = 3571 ms, TE = 94

ms with turbo spin echo - TSE impulse sequence), the brightness and darkness of the image

at the liver tissue changes with the decreased ratio of signal strength Ia/Ib = 2.3 times.

Hình 5.13. T2 weighted (Coronal) MR images showing rabbit (A) before injection of

contrast agent (B) after injection of contrast agent (a) for 0 minute (b)for 30 minutes (c) for

60 minutes with TE= 112 ms, TR =7500 ms

From Figure 5.13 shows that, after 30 minutes of injection (Fe3O4@PMAO magnetic

fluid sample) image (B), the rabbit's internal organs on MRI images have been shown more

clearly than MRI images before injection (Figure A) Specifically when taking an area in liver

tissue before and after the injection is 1.6 -1.8 cm2 respectively, the signal strength decreases

from 88.1 to 35.8 (corresponding to decrease 2.46 times compared with before injection. This

shows that magnetic fluids have the ability to change the contrast very strongly. With MRI

images taken at 60 minutes (C), the images are as clear as MRI images at time of 30 minutes

(B).

5.3.2. In-vivo test assesses the applicability of nanomagnetic fluid system Fe3O4 as a

contrast drug in cancer diagnosis using MRI magnetic resonance technique in animals

Solid tumor under the skin 15 days old in the thighs of mouse. The tumor is thick, not

necrotic and has a relatively homogeneous structure. We performed an MRI scan and obtained

images at the time immediately after direct injection of Fe3O4@PMAO magnetic fluid system

into mouse tumors and injecting intravenously (Figure 5.14 and Figure 5.15). To assess the

distribution of the Fe3O4@PMAO nano system in solid tumors under mouse skin, the tumor

after injection of the magnetic nanoparticle will be monitored over time under a 90° imaging

angle under Axial and Coronal style.

In Figure 3.9, the tumor of mouse C, F, G. The tumor of mouse C, E, F, and G show a

much higher contrast (darker) than the tumor of mouse B. Signal strength in the tumor varies

from 284.6 to 249, corresponding to mouse F and G. This indicates that the magnetic fluid

began to spread evenly throughout the tumor and changed the signal strength. While for mouse

C, although the intravenous fluids also had a signal change in the tumor clearly, specifically the

signal strength in mouse treated with cancer B was 296.5 downed 226.8.

Figure 5.14. T2 weighted (Coronal)MR images showing solid tumor mice with TE= 91 ms, TR

=3970 ms

With an average bidirectional size of about 15x10 mm, under normal conditions, there is

almost no observation of the tumor on the mousebody. However, after injecting the

nanomagnetic system of Fe3O4@PMAO, it can be seen that a dark area with a shape similar to

the tumor appears on the image (Figure 3.9). Thus, the presence of magnetic nanoparticles

supported 1.5T magnetic resonance imaging system to detect tumors at low material

concentrations (magnetic particles 0.18 mg). (Figure 3.10). Thus, the amount of 0.18 mg of

magnetic particles allows to detect the tumor in the image but not enough for the nano-system

can be spread to the entire tumor within 15 minutes, the shooting signal shows that

nanomaterials are almost covered the entire tumor at 30 minutes after injecting and maintaining

continuously for nearly 1 hour afterwards (Figure 3.10).

Figure 5.15. T2 weighted (Axial) MR images showing solid tumor mice (a) before injection

of contrast agent; (b) after injection of contrast agent; (c) for 15 minutes; (d) for 30 minutes

with TE= 91 ms, TR =3970 ms.

With the amount of magnetic nanoparticles injected into the tumor, the image shows a

spread of the material over time (Figure 5.15). The results obtained on MRI images showed

that after the direct injection of the fluid into the tumor, there was a clear dark area, different

from the non-injected cancer checking mouse, and clearly saw the contrast of the tumor area.

after 30 minutes of injection. To demonstrate the concentration of magnetic particles at tumors,

Figure 3.9 and Figure 5.15 in the form of color figure shown the occurrence of purple

corresponding to reduced signal strength that allows the use of magnetic fluid system applied

in diagnostic of cancer and support of treatment. After 30 minutes of injection of magnetic

particles into the tumor, the black area in the tumor of mouse D and F is much wider than the

time immediately after injection (Figure 5.15). The magnetic nanoparticles after being injected

into the tumor tend to spread to the whole tumor.

When taking magnetic fluid in the tumor of mouse through the intravenous injection

of mouse.

Figure 5.16. T2 weighted (Axial) MR images showing solid tumor mice (a) before injection

of contrast agent; (b) after injection under the tail vein of contrast agent for 2 hours; (c) for

12 hours; (d) for 24 hours with TE= 91 ms, TR =3970 ms.

In Figure 5.16, we see that the contrast of images when taking MRI of tumors in mouse

has not much difference. The results obtained on MRI images showed that after 2 hours of

injecting magnetic fluids in the mouse under the tail vein, clear dark areas were not observed,

which showed that the amount of nanoparticles is to the solid tumor very less after vein injection

after a short time. This can be explained by the intravenous injection, the magnetic nanoparticles

will follow the circulatory system to organs considered as the target of iron in the body like

liver, kidney, spleen and lymph, specifically at these tissues show a marked signal reduction

after injection of magnetic fluids (Figure 5.16), while other tissues and organs such as tumors

without targeted molecules will require a longer time for magnetic fluids to circulate from the

blood.

However, 12 hours after the injection, there were black points in the tumor area of mouse

D, and is almost dark in tumor area of mouse E after 24 hours. This suggests that there is a very

small amount of magnetic particles reaching the mouse tumor position after briefly injecting

the magnetic particles through the mouse vein. The black area of the tumor obtained after 12

hours or more allows to clearly define the tumor area, the rim of the tumor and the depth

structure of the tumor → this allows the use of magnetic fluid system applied in diagnostic of

cancer and support in treatment. However, when the magnetic fluid is directly inserted into the

tumor, the contrast of the tumor in the MRI images is higher than that of taking the magnetic

fluid into the vein in a short time.

GENERAL CONCLUSIONS

Through the detailed research results and appropriate discussions, some key

conclusions are drawn as follows:

1. Successfully fabricated magnetic fluids based on Fe3O4 particles by hydrothermal

method coated by chitosan natural polymer (CS). Optimized factors affecting magnetic

properties. Fe3O4@CS fluid sample has high durability in physiological environment.

2. Successfully fabricated magnetic fluids based on Fe3O4 particles by thermal

decomposition method by transferring phase and coating with PMAO polymer.

Fe3O4@PMAO fluid samples are highly durable in different conditions, single-dispersed,

uniform particles.

3. Examination of toxicity found that the Fe3O4@CS, Fe3O4@PMAO systems gave

good IC50 index. The fabricated fluid sample are not capable of cytotoxicity.

4. Determined the nuclear magnetic resonance imaging relaxation rate of 2 systems

Fe3O4@CS, Fe3O4@PMAO found that the fabrication systems have high r2 values of over

150 mM-1s-1 for samples of Fe3O4@PMAO, higher than the Resovist commodity. These

substances, when given MRI imaging tests, they appear good potential for applications

increasing contrast.

5. In-vitro, ex-vivo and in-vivo studies of MRI contrast enhancement showed that

many of the magnetic fluids of the manufacturing topic group showed good contrast

enhancement. Applying Fe3O4@PMAO system to solid tumors under the skin and liver

tumors, found the potential for observing the shape and structure of tumor details in stages,

support for diagnosis and treatment.

6. The research results have been presented and published in 09 scientific articles (02

articles in ISI magazine, in which 01 article has been published and 01 article is being

submitted for criticism, 08 in specialized journals and National Conferences). An intellectual

property license was registered (accepted for application, published in Intellectual Property

Gazette Episode A No. 365) on the manufacturing and testing technology of magnetic fluids

in MRI.

PUBLISHED REPORTS USED IN THIS THESIS

1. Vu Thi Thu, An Ngoc Mai, Le The Tam, Hoang Van Trung, Phung Thi Thu, Bui Quang

Tien, Nguyen Tran Thuat, Tran Dai Lam. Fabrication of PDMS-Based microfluidic devices:

Appliaction for synthesis of magnetic nanoparticles. Journal of electronic materials (SCI),

Q2, IF2017 1.579. Vol 45, Issue 5, 2016, pp 2576-2581. DOI 10.1007/s11664-016-4424-6.

2. Le The Tam, Nguyen Hoa Du, Le Trong Lu, Phan Thi Hong Tuyet, Nguyen Quoc Thang,

Nguyen Thi Ngoc Linh, Nguyen Thi Hai Hoa, Tran Dai Lam. Magnetic Fe3O4 nanoparticle

imaging T2 contrast agent synthesized by optimized hydrothermal method. Submited to

Royal Society of Chemistry Advances (SCI), 2019, Q1, IF2017 2.936 (Under Review).

3. Trần Đại Lâm, Lê Thế Tâm, Lê Trọng Lư, Vương Thị Kim Oanh, Đỗ Hùng Mạnh, Nguyễn

Xuân Phúc, Phạm Hồng Nam, Trần Đại Lâm. Quy trình chế tạo hệ chất lỏng từ tính nano

Fe3O4 để làm thuốc tương phản trong chẩn đoán hình ảnh bằng kỹ thuật cộng hưởng từ MRI.

Sở hữu trí tuệ (Sáng chế). Số đơn SC 1-2018-01215. Đã chấp nhận đơn hợp lệ và đã công

bố trên công báo sở hữu công nghiệp số 365/T8, tập A: 58762

4. Le The Tam, Nguyen Hoa Du, Tran Dai Lam, Le Thi Nhan, Nguyen Van Toan. Study on

some factor of magnetic fluid chitosan-coated Fe3O4 nanoparticles fabrication via

hydrothermal method for Biomedicine, 2016. Viet Nam Journal of science and technology,

Vol 54, 2C, 2016, pp 341-347.

5. Le The Tam, Vuong Thi Kim Oanh, Nguyen Hoa Du, Tran Dai Lam. Optimization of co-

precipitation reaction involving main experimental factors on crystallite size of chitosan-

coated magnetic nanoparticles Fe3O4 by response surface method with central composite

designs. Vietnam Journal of Chemistry, No 5e1,2 (54), 2016, 207-211.

6. Nguyen Hoa Du, Le The Tam, Tran Dai Lam, Phan Thi Hong Tuyet, Tran Thi Huong.

Optimization factors affected saturation Magnetic fluid Chitosan-coated Fe3O4 in co-

precipitation reaction by Response surface method with central composite designs, 2016. Viet

Nam Journal of science and technology, Vol 54, 2B, 2016, pp 142-148.

7. Le The Tam, Vuong Thi Kim Oanh, Nguyen Hoa Du, Le Trong Lu, Le Hai Dang, Nguyen

Thi Hai Hoa, Le Ngoc Tu, Tran Dai Lam. Magnetic resonance imaging (MRI) application of

Fe3O4 based ferrofluid synthesized by thermal decomposition using poly (maleic anhydride -

alt-1-octadecene) (PMAO). Viet Nam Journal of Science and Technology, Vol 56, 1A,

2018, pp 174-182.

8. Le The Tam, Tran Dai Lam, Nguyen Hoa Du, Phan Thi Hong Tuyet, Nguyen Quoc Thang.

Synthesis, characterization and MRI application of Fe3O4 liquid was synthesized by

hydrothermal with using Sodium Alginate. Proceedings of the the Scientific Conference

Chemical, Material and Environmental Engineering for Sustainable Development

(CME2018), in Quy Nhon City Vietnam, pp 49-56.

9. Lê Thế Tâm, Nguyễn Hoa Du, Nguyễn Quốc Thắng, Phan Thị Hồng Tuyết, Lê Trọng Lư,

Nguyễn Thị Ngọc Linh, Võ Kiều Anh, Phạm Hồng Nam, Trần Đại Lâm. Chế tạo chất lỏng

từ tính chứa Fe3O4@PMAO cho ứng dụng MRI điều chế bằng phương pháp phân hủy nhiệt.

Tạp chí Hóa học, Viện Hàn lâm KHCN Việt Nam (2018). Vol 56(6e2), pp 63-69.