Journal of Environmental Treatment Techniques 2019, Volume 7, Issue 4, Pages: 802-807
802
Fabrication and Properties of Collagen and
Polyurethane Polymeric Nanofibers Using
Electrospinning Technique for Tissue Engineering
Applications
Nasrin Beheshtkhoo † a, Mohammad Amin Jadidi Kouhbanani
† a, Fatemeh sadat Dehghani
a,
Shahla abdollahiib, Mohsen Alishahi
a, Vahid Razban
c, Ali Mohammad Amani
a,d*
aDepartment of Medical Nanotechnology, School of Advanced Medical Sciences and Technologies, Shiraz University of Medical Sciences, Shiraz, Iran
bDepartment of Medical Nanotechnology, School of Advanced Medical Sciences and Technologies, Shahroud University of Medical Sciences, Shahroud, Iran
cDepartment of Molecular Medicine, School of Advanced Technologies in MedicineShiraz University of Medical Sciences dPharmaceutical Sciences Research Center, Shiraz University of Medical Sciences, Shiraz, Iran
Abstract
The present study introduces a nanofibers skin patch comprised of collagen and polyurethane polymers. Belonging to the family of
biodegradable polymers, they can be mixed with various drugs, degraded at the wounded area, whereby the drug is gradually released
into the wound. The characterization of nanofibers were identified using mechanisms such as SEM, FTIR, and tensile test. The results
of SEM analysis indicated that all the fabricated nanofibers have a proper and uniform morphology. FTIR spectrum for collagen and
TPU revealed various factor groups including N-H group with hydrogen bond, CH2 group, (C=O) carbonyl group, and carboxyl group
(COO) for collagen. Furthermore TPU spectrum demonstrated a broad peak for N-H group, the symmetric and asymmetric stretching
for CH2 group as well as carbonyl group (C=O) peak. In addition, a tensile test examined the mechanical properties of nanofibers with
and without loaded natural honey, indicating that the use of natural honey in the structure of nanofibers decreases the maximum stress
at break point.
Keywords: Nanofiber; Electrospinning; Scaffold; Tissue engineering; Chitosan; Polyurethane
1 Introduction1
Skin diseases have been an issue of considerable concern
to the World Health Organization (WHO) such that an
enormous number of studies thus far have been conducted to
find new treatment ways, one of which is to develop an
instrument to topically deliver the drug to the skin. The
advantages of this drug delivery patch over the injection drug
delivery include:
Topical drug delivery to the wound allows the drug to remain
in the injured area in large amounts, inducing less side effects
than injection drug delivery does.
Injection drug delivery has a regular daily basis, that is, the
patient is to receive injection every day, while the topical drug
delivery patch obviates the need for the patient’s presence to
receive injection, making it possible for the patient to replace
the patch after some days.
Corresponding author: Nasrin Beheshtkhoo, Department of
Medical Nanotechnology, School of Advanced Medical
Sciences and Technologies, Shiraz University of Medical
Sciences, Shiraz, Iran.
† These authors contributed equally to this work.
The costs of daily injection may surpass those of topical drug
delivery patch since in the former the drug should be
purchased and injected every day, whereas topical patches
incur less costs due to the continuity and control of drug
delivery process.
In comparison with topical drug delivery, injection drug
delivery is more painful and causes more infectious problems.
In recent years, the use of nanotechnology such as nanofibers
has gained substantial popularity. Nanofibers have enormous
applications in medical sciences including artificial organs,
tissue engineering, medical prostheses, wound dressing, and
drug delivery. Nanofibers are characterized by a unique
ability in loading biological molecules, drugs, and
nanoparticles.
Capable of being fabricated from various substances such
as ceramics and polymers, fibers are thin and long threads
which have high length to diameter ratios. Fibers with
diameters ranging from 1 to 1000 nanometers are called
nanofibers which have different properties including high
surface area to volume ratio, mechanical strength, and
versatility, making them an ideal scaffold for various medical
and engineering applications (1). With regard to medical uses,
nanofibers have special properties such as their similarity to
extracellular matrix (ECM) composed of 10 to over 100
nanometer diameter protein fibers such as collagen. The
Journal weblink: http://www.jett.dormaj.com
J. Environ. Treat. Tech.
ISSN: 2309-1185
Journal of Environmental Treatment Techniques 2019, Volume 7, Issue 4, Pages: 802-807
803
relationship between ECM and cells regulates various cell
behaviors including reproduction and gene expression. The
more the resemblance between the fabricated scaffold and
ECM, the better the scaffold can involve in cellular
interactions. Therefore, using nanometer diameter fibers
makes it possible to obtain an appropriate mimic of ECM.
This property turns nanofibers into a unique structure for
medical applications, particularly in tissue engineering (2).
There are various nanofibers fabrication techniques, the
main one being electrospinning method due to its versatility,
adaptability, simplicity and cost-efficiency. Another
advantage of electrospinning technique is its capability in
fabricating fibers from biomaterials such as biodegradable
polymers. When mixed with drugs, polymer solutions turn
into drug-incorporated nanofibers. With degradation of
polymer in the wounded area, the drug is slowly released and
penetrated into the wound (3). Nanofibers can be also utilized
to achieve optimal release rate by controlling various factors
effective on drug release in polymeric matrix structure. It
should be noted that selection of polymer for nanofiber
fabrication is one of the most significant factors (4) as the
polymer should be biocompatible, biodegradable, and have
appropriate physical properties. Depending on the kind of
drug delivery process, releasing drug can be performed in
various durations spanning from several hours to days. Thus,
polymer selection should be in such a way that polymer
degradation rate be proportional to the rate of drug release.
Electrospinning device is made up of four main parts:
1. A power supply which provides the voltage needed for
electromagnetic force between the needle tip and the
collector.
2. Syringe pump through which polymeric solution is
pumped
3. A needle tip connected to one voltage terminal.
4. A collector connected to other voltage terminal and where
fibers are fabricated
To start electrospinning process, polymeric solution or
melt should be prepared in advance. Then, the polymer
solution is filled in a syringe and placed over the syringe
pump such that a droplet of the polymer solution appears on
the tip of the needle connected to one voltage terminal
(usually negative pole) while the collector is connected to
other terminal (usually positive pole). Given the appropriate
distance between needle tip and the collector screen as well as
the proper applied voltage, the process of nanofiber
fabrication starts (5). After a voltage is applied by the power
supply to the needle tip, this will become highly charged and
the induced surface charges on the polymeric solution will be
evenly distributed over its surface, making the droplet
transform from a rounded (The reason for the rounded droplet
shape is the fact that in the absence of any voltage applied to
the droplet, it tends to form a shape with a less volume to
surface area ratio) to a conical shape (6) also known as
“Taylor cone”, shown in Fig. 1-1. When higher voltages are
applied, the solution is so electrified that it reaches the so
called critical voltage. Consequently, the electric force
overcomes the surface tension of the drop, leading to the
formation of a charged jet which is expelled from the tip of
Taylor cone towards the rotating collector surface where the
fibers are deposited. This cycle continues as the solution in
the syringe pump is charged to expel out more and more
droplets to be changed into fibers (7-8-9).
As the jet stretches out and turns into nanofibers on its
way towards the collector, the solvent evaporates. At the
beginning, the jet moves in a straight line towards the
collector, but as it approaches the collector, which is
connected to the other end of voltage terminal, the charged jet
whips across space between the needle tip and the collector in
a spiraling way. It is worth noting that the interaction between
various electrospinning parameters should be in a way that the
charged jet maintain a continuous and steady whipping
movement toward the collector.
Fig. 1-1: Taylor cone and tip of needle during electrospinning
Depending on the number of needles, electrospinning is
divided into two uniaxial (single needle) and multiaxial
(multiple needles) processes. In the former, polymeric
solution and the drug are contained in the syringe and are
expelled out toward the collector through a single needle,
whereas in the latter there are two needles as core and shell
and two syringe pumps are used to drive solutions into the
needles (10, 11, 12, 13, 14). Even though electrospinning is a
seemingly simple technique, all the parameters involved such
as the solution, environmental factors, and their interactions
make electrospinning a sensitive process. All in all, they
should interact in such a way that the charged jet steadily
moves toward the collector and that fiber diameters are
consistent and in the expected ranges (15, 16, 17, 18, 19, 20).
2 Materials and methods 2.1 Synthesis
To prepare the solution, various percentages and methods
were used and, in the end, the proper conditions for
fabricating nanofibers without beads were achieved. The
solution was prepared as follows: Thermoplastic polyurethane
(0.2 gr) was mixed with collagen (0.05 gr) and, then, they
were gradually added to 3.5 ml deionized water and 1.5 ml
hexafluoro-2-propanol (HFIP) while being stirred using a
magnetic mixer at room temperature. After 24 hours, they
were completely dissolved, turning into a colorless, viscous,
uniform and homogeneous solution (21).
2.2 Electrospinning setup and specification
The electrospinning setup utilized in the present study was
composed of: a power supply, syringe pump, uniaxial needle
tip, syringe, and a rotating collector To produce the electric
field, a high voltage direct current (DC) power supply was
used. The power supply device (High Voltage 35 OC,
Fanavaran Nano-Meghyas, Tehran, Iran) applied voltages
ranging from 0 to 18 KV. The positive terminal was
connected to the needle tip and the negative terminal to the
rotating collector. Moreover, the syringe pump (model
SP1000HOM, Fanavaran Nano-Meghyas, Tehran, Iran) was
designed to use various kinds of syringes. Given the
dimensions of the syringes, the pump syringe could expel out
a certain amount of solution with the lowest and the highest
Journal of Environmental Treatment Techniques 2019, Volume 7, Issue 4, Pages: 802-807
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speeds of 0.5 µl/h and 1000 ml/h, respectively. The internal
diameter of the syringe was entered into the system using a
keyword, according to which the device computed and
applied the precise amount of solution release. The memory
used in the device was of a permanent type and the last
configurations from syringe size, solution release speed to the
transformation time were recorded in the memory. Also, the
uniaxial needle tip utilized to produce droplets was 0.8192
mm in external diameter (Guage-21 specification). Moreover,
a 5 mm syringe with a 12.5 mm internal diameter was used to
pump the solution into the main syringe. With regard to the
collector, aluminum plates with the dimensions of 25×10 cm2
were employed on the roller as the collector and the distance
between the needle tip and the collector was measured
precisely before any trial.(22)
2.3 Analysis of Scanning Electron Microscope (SEM)
To examine the morphology and microscopic structure of
nanofibers as well as to determine their diameter, SEM
analysis was conducted on the fibers. To prepare the fibers
for SEM analysis, they were first sliced with dimensions of
1×1 cm2 and then mounted on an aluminum foil. In the
present study, we used TESCAN VEGA electron microscope
produced by the Czech Republic. Before imaging, the sliced
sample fibers were covered with gold in 900
angstrom thickness. During SEM analysis, we shine beams of
electrons on the surface of the sample fibers and then the
emissions are scanned while the image of the surface of
samples are shown on a monitor. To better analyze the
morphology of fibers, they were scanned in seven various
zooms
2.4 SEM analysis images
In order to determine the diameter of nanofibers, images
from SEM analysis of sample fibers were analyzed using
ImageJ software. To this end, of each sample, a total of 40
fibers were randomly selected and examined. To work by the
software, first certain specified sizes were entered into the
program so as to determine the zoom scale for the software.
Then, the diameter of a fiber was computed by measuring the
distance between the two ends of the fiber. The mean
diameter of measured fibers was reported as the sample fiber
diameter. (23)
2.5 Tensile test
In order to assess the mechanical properties of samples,
they were subjected to a tensile test in which sample fibers, in
rectangular form, were stretched out to the point where they
broke in half. In this tensile test, the ultimate plot was a stress-
strain one such that strain was considered sample length per
initial length and stress as force per sample cross section.
Analysis of stress-strain plot gave way to three parameters:
Elastic modulus or Young’s modulus (E), at the beginning of
which there was the slope of stress-strain curve; Tensile
strength also known as the maximum stress in stress-strain
curve; and Elongation-to-break or the degree of strain at the
end of stress-strain curve where the sample broke in halves.
As mentioned before, to perform this tensile test, the fiber
samples were sliced in the form of rectangles with dimensions
of 6×1 cm. They were also placed in a vacuum oven 94 hours
before trial at room temperature and humidity. For this test,
the use was made of Machine Testing Universal Santam
device as well as cell load with the weight of 1.4 kg and
tensile speed of 1 mm/m. The analysis of stress-strain plot
obtained from the device yielded Young’s modulus, tensile
strength and elongation-to-break (24).
2.6 Fourier-Transform Infrared Spectroscopy (FTIR)
In order to identify and analyze the bonds between fibers
and polymers utilized to fabricate nanofibers as well as to
compare their structure, FTIR analysis was employed. FTIR
analysis examines polymers existing in the sample material by
assessing the degree of emission and rotation in bonds of the
material. Given that any material has a certain infrared
spectrum, FTIR is a proper method of confirming the presence
of any bond and of identifying the kind of material being
used. Accordingly, the present study utilized FTIR
spectrometer model RX1 Spectrum manufactured by Elmer
Perkin. To prepare the fibers, they were sliced into small
parts, hence their being formed into tablets and ground along
with potassium bromide (KBr), a neutral salt powder, in front
of infrared radiation (25).
3 Results and discussion 3.1 Nanofiber fabrication results
The present study made an attempt to fabricate
thermoplastic polyurethane (TPU) nanofibers and collagen.
To do so, various electrospinning parameters were initially
evaluated and different concentrations of TPU were prepared
with various injection rates. Afterwards, fiber morphology
and diameter under different electrospinning conditions were
examined via SEM imaging. Such electrospinning parameters
should be regulated in a way that the diameter and
morphology as well as mechanical properties of fibers are
optimized. The parameters for fabricating the optimized
sample fibers were: needle gauge 21, electrospinning solution
with 4% and 3% concentrations of poly-ethylene-oxide (PEO)
and chitosan, respectively. Moreover, the optimal voltage and
the distance between the needle tip and the collector were 10
KV and 11 cm, respectively. The rotating speed of the
collector was also set on 600 rpm along with optimal injection
speed of 0.9 mm/m. Table 3-1- introduces samples fabricated
in various injection rates and chitosan percentages.
3.2 SEM analysis
To examine the morphology, microscopic structure and
diameter of fibers, SEM analysis was performed. To find the
optimal conditions for electrospinning, samples with various
injection rates were analyzed. Fig. 3-1 depicts SEM images
for all the four samples which were analyzed through ImageJ
software so as to compute their mean diameter summarized in
Table 3-2.
Table 3-1: Parameters and amounts used in nanofiber fabrication
Samples Parameters
TPU (%) Collagen (%) Injection Rate (ml/h) Voltage (KV) Distance to Collector (cm)
Sample 1 4 1 0.5 10 11
Sample 2 4 3 0.5 10 11
Sample 3 4 3 0.5 10 11
Sample 4 4 3 0.9 10 11
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Fig. 3-1: SEM images (from right to left: Sample 1 to Sample 4)
SEM analyses revealed that all the samples had an
appropriate and uniform morphology, according to which
Sample 4, selected as the optimal one, proved to be the most
useful for medical applications (26-27).
Table 3-2: Mean diameters from SEM images
Samples Mean Diameter
Sample 1 800
Sample 2 683
Sample 3 917
Sample 4 1003
3.3 FTIR results
In this section of the study, various FTIR spectra for
collagen, TPU and synthesized nanofibers were examined.
Regarding collagen FTIR spectrum in peaks 3426, 2940,
1660, and 1541, N-H group with hydrogen bond, CH2
asymmetric stretching, (C=O) carbonyl group stretching,
hydrogen bond coupled with carboxyl (COO), and finally N-
H bending vibration along with C-N stretching vibration were
witnessed. Furthermore, with regard to TPU spectrum, a
broad peak for N-H group was seen in peak 3333, the
symmetric and asymmetric stretching for CH2 group were
respectively witnessed in peaks 2861, and 2934. Also,
carbonyl group (C=O) was witness at peak 1726 with a strong
shoulder near 1700 which was associated with carbonyl
resonance stretching along with urethane-based hydrogen
bonds. Moreover, in areas 1528, and 1100, peaks for N-H
group stretching as well as COC group peak were seen.
According to the comparison of collagen infrared spectra and
TPU, shown by Fig. 3.2 , it was concluded that in the
synthesized nanofiber spectra, all the peaks for collagen and
TPU were witnessed although with a little replacement due to
interactions, suggesting that nanofibers were favorably
synthesized (28, 29, 30, 31) .
3.4 Tensile test
The present study performed a tensile test on sample
fibers so as to examine the effect of loaded drug on the
mechanical properties of fibers. The samples consisted of
optimally electrospun pure fibers composed of natural honey.
The conditions were as follows:
The applied voltage and the distance between needle tip and
the collector were 10 KV and 11 cm, respectively. The stress
plot of the fibers on the basis of samples deformation
percentage is shown by Figs. 3-3 and 3-4. Also, the stress and
elongation-to-break of samples are also depicted by Table 3-3.
Given the results of stress plot on the basis of deformation
percentage as well as the effect of the honey loaded on fibers,
it was concluded that increase in the amounts of honey
decreased maximum stress at break point.
Fig. 3-2: FTIR Plot for Synthesized nanofibers
Fig. 3-3: Plot of stress on the basis of nanofiber elongation change
80
82
84
86
88
90
92
450950145019502450295034503950
00.5
11.5
22.5
33.5
44.5
5
0 10 20 30 40 50 60 70 80 90 100110120130140150
St
En
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Fig. 3-4: Plot of stress on the basis of honey-loaded nanofiber
elongation change
4 Conclusion Sseveral studies have been carried out on syntheses of
nanoparticles (41–50). The present study was carried out with
the aim of examining the fabrication and properties of
collagen and polyurethane polymeric nanofibers using
electrospinning technique. SEM technique was employed to
investigate the morphology, microscopic structure as well as
diameter of nanofibers, as a result of which the best nanofiber
for medical applications was selected. Afterwards, the optimal
nanofiber was chosen using FTIR analysis. To do so, a
comparison of IR spectrum of raw material and the product
helped us come to the conclusion that the nanofiber was
favorably synthesized. In the end, we used tensile test to
examine mechanical properties of the selected nanofiber
loaded with natural honey as the delivered drug, suggesting
that the nanofiber had optimal tensile properties. Also, it was
found that using natural honey in the structure of nanofiber
decreased the maximum stress at break point.
Table 3-3: Mechanical properties of nanofibers with various concentrations of loaded drug
Sample Stress at break point Elongation-to-break
Nanofibers without natural honey 4.70 142.04
Nanofibers with natural honey 3.01 153.07
References 1. Sencadas V, Correia DM, Areias A, Botelho G, Fonseca AM,
Neves IC, et al. Determination of the parameters affecting
electrospun chitosan fiber size distribution and morphology.
Carbohydr Polym. 2012;87(2):1295–301.
2. Teo W, He W, Ramakrishna S. Electrospun scaffold tailored
for tissue‐specific extracellular matrix. Biotechnol J Healthc
Nutr Technol. 2006;1(9):918–29.
3. Goyal R, Macri LK, Kaplan HM, Kohn J. Nanoparticles and
nanofibers for topical drug delivery. J Control Release.
2016;240:77–92.
4. Neo YP, Ray S, Easteal AJ, Nikolaidis MG, Quek SY.
Influence of solution and processing parameters towards the
fabrication of electrospun zein fibers with sub-micron
diameter. J Food Eng. 2012;109(4):645–51.
5. Beachley V, Wen X. Polymer nanofibrous structures:
Fabrication, biofunctionalization, and cell interactions. Prog
Polym Sci. 2010;35(7):868–92.
6. Carlson BM. Stem Cell Anthology: From Stem Cell Biology,
Tissue Engineering, Cloning, Regenerative Medicine and
Biology. Academic Press; 2009.
7. Dasdemir, Mehmet, Mehmet Topalbekiroglu, and Ali Demir.
"Electrospinning of thermoplastic polyurethane microfibers
and nanofibers from polymer solution and melt." Journal of
Applied Polymer Science 127.3 (2013): 1901-1908.
8. Zakeri, Abbas, et al. "Polyethylenimine-based nanocarriers in
co-delivery of drug and gene: a developing horizon." Nano
reviews & experiments 9.1 (2018): 1488497.
9. Frenot, Audrey, and Ioannis S. Chronakis. "Polymer nanofibers
assembled by electrospinning." Current opinion in colloid &
interface science 8.1 (2003): 64-75.
10. Zong, Xinhua, et al. "Structure and process relationship of
electrospun bioabsorbable nanofiber membranes." Polymer
.4403-4412 :(2002) 43.16
11. Fong, Hao, Iksoo Chun, and Darrel H. Reneker. "Beaded
nanofibers formed during electrospinning." Polymer 40.16
.4585-4592 :(1999)
12. Teo, Wee E., and Seeram Ramakrishna. "A review on
electrospinning design and nanofibre assemblies."
Nanotechnology 17.14 (2006): R89.
13. Ding, Bin, and Jianyong Yu, eds. Electrospun nanofibers for
energy and environmental applications. Springer Berlin
Heidelberg, 2014.
14. Sambaer, Wannes, Martin Zatloukal, and Dusan Kimmer. "3D
modeling of filtration process via polyurethane nanofiber
based nonwoven filters prepared by electrospinning process."
Chemical Engineering Science 66.4 (2011): 613-623.
15. Thompson, C. J., et al. "Effects of parameters on nanofiber
diameter determined from electrospinning model." Polymer
.6913-6922 :(2007) 48.23
16. Tan, See-Han, et al. "Systematic parameter study for ultra-fine
fiber fabrication via electrospinning process." Polymer 46.16
.6128-6134 :(2005)
17. Jalili, Rouhollah, Mohammad Morshed, and Seyed
Abdolkarim Hosseini Ravandi. "Fundamental parameters
affecting electrospinning of PAN nanofibers as uniaxially
aligned fibers." Journal of applied polymer science 101.6
.4350-4357 :(2006)
Beachley, Vince, and Xuejun Wen. "Effect of electrospinning .18
parameters on the nanofiber diameter and length." Materials
Science and Engineering: C 29.3 (2009): 663-668.
19. Theron, S. A., E. Zussman, and A. L. Yarin. "Experimental
investigation of the governing parameters in the
electrospinning of polymer solutions." Polymer 45.6 (2004):
.2017-2030
20. Okutan, Nagihan, Pınar Terzi, and Filiz Altay. "Affecting
parameters on electrospinning process and characterization of
electrospun gelatin nanofibers." Food Hydrocolloids 39
.19-26 :(2014)
21. Xu, Cancan, et al. "Triggerable degradation of polyurethanes
for tissue engineering applications." ACS applied materials &
interfaces 7.36 (2015): 20377-20388.
22. Uecker, Jan. "The Production and Filtration Efficiency
Testing of Nonwoven Electrospun Fiber Mats." (2009).
23. Frenot, Audrey, Maria Walenius Henriksson, and Pernilla
Walkenström. "Electrospinning of cellulose‐based
nanofibers." Journal of applied polymer science 103.3 (2007):
.1473-1482
0
0.5
1
1.5
2
2.5
3
3.5
0 10 20 30 40 50 60 70 80 90100110120130140150160
St
En
Journal of Environmental Treatment Techniques 2019, Volume 7, Issue 4, Pages: 802-807
807
24. Tan, E. P. S., et al. "Tensile test of a single nanofiber using an
atomic force microscope tip." Applied Physics Letters 86.7
.073115 :(2005)
25. Baudot, Charles, Cher Ming Tan, and Jeng Chien Kong.
"FTIR spectroscopy as a tool for nano-material
characterization." Infrared Physics & Technology 53.6 (2010):
.434-438
26. Huang, Chen, et al. "Electrospun collagen–chitosan–TPU
nanofibrous scaffolds for tissue engineered tubular grafts B
Biointerfaces." (2011).
27. Chen, Rui, et al. "Preparation and characterization of coaxial
electrospun thermoplastic polyurethane/collagen compound
nanofibers for tissue engineering applications." Colloids and
Surfaces B: Biointerfaces 79.2 (2010): 315-325.
28. Huang, Chen, et al. "Electrospun collagen–chitosan–TPU
nanofibrous scaffolds for tissue engineered tubular grafts B
Biointerfaces." (2011).
29. Samimi Gharaie, Sadaf, Sima Habibi, and Hosein Nazockdast.
"Fabrication and characterization of
chitosan/gelatin/thermoplastic polyurethane blend
nanofibers." Journal of Textiles and Fibrous Materials 1
.2515221118769324 :(2018)
30. Chen, Rui, et al. "Preparation and characterization of coaxial
electrospun thermoplastic polyurethane/collagen compound
nanofibers for tissue engineering applications." Colloids and
Surfaces B: Biointerfaces 79.2 (2010): 315-325.
31. Chen, Rui, K. E. Ke, and Xiumei Mo. "Preparation and Study
of TPU/Collagen Complex Nanofiber via Electrospinning."
AATCC review 10.2 (2010).
32. Mi, Hao‐Yang, et al. "Thermoplastic
polyurethane/hydroxyapatite electrospun scaffolds for bone
tissue engineering: effects of polymer properties and particle
size." Journal of Biomedical Materials Research Part B:
Applied Biomaterials 102.7 (2014): 1434-1444.
33. Rogina, Anamarija. "Electrospinning process: Versatile
preparation method for biodegradable and natural polymers
and biocomposite systems applied in tissue engineering and
drug delivery." Applied Surface Science 296 (2014): 221-230.
34. Electrospun aligned poly(propylene carbonate) microfibers
with chitosan nanofibers as tissue engineering scaffolds
35. Liu, L‐Q., et al. "Tensile mechanics of electrospun
multiwalled nanotube/poly (methyl methacrylate) nanofibers."
Advanced Materials 19.9 (2007): 1228-1233.
36. Shin, Ho Joon, et al. "Electrospun PLGA nanofiber scaffolds
for articular cartilage reconstruction: mechanical stability,
degradation and cellular responses under mechanical
stimulation in vitro." Journal of Biomaterials Science,
Polymer Edition 17.1-2 (2006): 103-119.
37. Gong, Guan, et al. "Tensile behavior, morphology and
viscoelastic analysis of cellulose nanofiber-reinforced (CNF)
polyvinyl acetate (PVAc)." Composites Part A: Applied
Science and Manufacturing 42.9 (2011): 1275-1282.
38. Lee, Seung-Hwan, et al. "Mechanical properties and creep
behavior of lyocell fibers by nanoindentation and nano-tensile
testing." Holzforschung 61.3 (2007): 254-260.
39. Jonoobi, Mehdi, Aji P. Mathew, and Kristiina Oksman.
"Producing low-cost cellulose nanofiber from sludge as new
source of raw materials." Industrial Crops and Products 40
.232-238 :(2012)
40. Choi, Sung-Seen, et al. "Formation of interfiber bonding in
electrospun poly (etherimide) nanofiber web." Journal of
materials science 39.4 (2004): 1511-1513.
41. Lohrasbi, Sajedeh, et al. "Green Synthesis of Iron
Nanoparticles Using Plantago major Leaf Extract and Their
Application as a Catalyst for the Decolorization of Azo Dye."
BioNanoScience 9.2 (2019): 317-322.
42. Beheshtkhoo, Nasrin, et al. "Green synthesis of iron oxide
nanoparticles by aqueous leaf extract of Daphne mezereum as
a novel dye removing material." Applied Physics A 124.5
.363 :(2018)
43. Kouhbanani, Mohammad Amin Jadidi, et al. "One-step green
synthesis and characterization of iron oxide nanoparticles
using aqueous leaf extract of Teucrium polium and their
catalytic application in dye degradation." Advances in Natural
Sciences: Nanoscience and Nanotechnology 10.1 (2019):
.015007
44. Kouhbanani, Mohammad Amin Jadidi, et al. "Green synthesis
of iron oxide nanoparticles using Artemisia vulgaris leaf
extract and their application as a heterogeneous Fenton-like
catalyst for the degradation of methyl orange." Materials
Research Express 5.11 (2018): 115013.
45. Kouhbanani, Mohammad Amin Jadidi, et al. "Green Synthesis
and Characterization of Spherical Structure Silver
Nanoparticles Using Wheatgrass Extract." Journal of
Environmental Treatment Techniques 7.1 (2019): 142-149.
46. Rostamizadeh, Shahnaz, et al. "Aqueous NaHSO 4 catalyzed
regioselective and versatile synthesis of 2-thiazolamines."
Monatshefte für Chemie/Chemical Monthly 139.10 (2008):
1241-1245.
47. Rostamizadeh, Shahnaz, et al. "An efficient one‐pot procedure
for the preparation of 1, 3, 4‐thiadiazoles in ionic liquid
[bmim] BF4 as dual solvent and catalyst." Heteroatom
Chemistry: An International Journal of Main Group Elements
19.3 (2008): 320-324.
48. Amani, A. M. "Synthesis and biological activity of piperazine
derivatives of phenothiazine." Drug research 65.01 (2015): 5-
8.
49. Rostamizadeh, Shahnaz, et al. "MCM-41-SO 3 H: a novel
reusable nanocatalyst for synthesis of amidoalkyl naphthols
under solvent-free conditions." Monatshefte für Chemie-
Chemical Monthly 144.8 (2013): 1191-1196.
50. Hashemi, Seyyed Alireza, et al. "Lead oxide-decorated
graphene oxide/epoxy composite towards X-Ray radiation
shielding." Radiation Physics and Chemistry 146 (2018): 77-
85.46.
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