Various parameters influence on electrospun herbs ...

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Various parameters influence on electrospun herbs incorporated cellulose acetate and its

suitability for drug delivery

Thilakam R* and Elakkiya Thangaraju

Department of Chemistry, Sri Sarada College for Women (Autonomous), Salem – 16,

Tamilnadu, India

[email protected]*, and [email protected]

Abstract

In the present work, electrospun cellulose acetate membrane suitability was analyzed for

nanocarrier in drug delivery systems. Electrospinning is one of the versatile techniques to

produce interconnected porous nanofibrous membrane. Of the electrospinning process, various

parameters namely solvent, collector and solution concentration would influence the nanofibrous

membrane. One of the hydrophilic biopolymer namely cellulose acetate was used to electrospun

and the smooth nanofibrous membrane was optimized. The electrospun cellulose acetate surface

morphology was deeply analyzed by Scanning electron microscopy. The curcumin was

incorporated into the optimized cellulose acetate solution and produced curcumin loaded

cellulose acetate nanofibrous membrane in one step process. The presence of curcumin in

curcumin loaded cellulose acetate nanofibrous membrane was studied by Scanning electron

microscopy and Transmission electron microscopy. The antioxidant activity and in-vitro

curcumin release from curcumin loaded cellulose acetate nanofibrous membrane was evaluated

for drug delivery.

Keywords: Electrospinning, Nanofibers, Cellulose acetate, Curcumin, Drug delivery

IAETSD JOURNAL FOR ADVANCED RESEARCH IN APPLIED SCIENCES

VOLUME VI, ISSUE III, MARCH/2019

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Introduction

Electrospinning is one of the efficient techniques to fabricate highly interconnected,

continuous non-woven nanofibers that do not require expensive purification protocols. Choosing

the solvent, concentration of the solution and collector plays a major role on the fiber diameter

during electrospinning process [1-3]. They can be effectively used as a biomedical applications

namely tissue engineering, drug delivery, wound healing and dental implants due to their

extraordinary properties such as high porosity and large surface area to volume ratio. In addition,

it has great ability to physically resemble natural extra cellular matrix (ECM) protein structure

which also allows higher drug encapsulation efficiency [4-5]. The good biocompatible and

biodegradable food and drug administration approved polymers like cellulose acetate has drawn

great attention because they can be used in many biomedical applications including implants [6-

7]. Cellulose acetate, a derivative of cellulose obtained from natural resources can be easily

fabricated into films, fibers and membranes due to its abundant availability and biodegradability.

Cellulose acetate produced by electrospinning process has been reported with diameters in the

range of tens of nanometers to micrometers with pore sizes in the range of submicron to microns

[8-10]. Cellulose acetate based polymer blend membranes have been used in biomedical

applications especially drug delivery and tissue engineering due to its good hydrolytic stability,

excellent biocompatibility in human body and relatively low cost [11]. The herbs like curcumin,

which is also known as turmeric exhibit highly immense anti–tumor, anti-oxidant, and anti-

inflammatory properties [11-15]. Curcumin is highly hydrophobic in nature with poor water

solubility.

The present study aims in evaluating the ability of cellulose acetate nanofibrous

membrane as a nanocarrier for hydrophobic drug like curcumin. In this study, the diameter and

alignment of the cellulose acetate fibrous membrane were optimized by the process of

electrospinning based on the solvent, concentration of the polymer solution and the collector.

The surface morphology of different types of electrospun cellulose acetate was studied by

scanning electron microscopy. The curcumin present in cellulose acetate nanofibrous membrane

was studied by scanning electron microscopy and transmission electron microscopy. The

antioxidant activity of curcumin loaded cellulose acetate nanofibrous membrane was

characterized using DPPH assay. The in-vitro curcumin release from curcumin loaded cellulose



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acetate nanofibrous membrane was studied by High performance liquid chromatography with

ultra-violet detector.

Experimental details

Materials

Cellulose acetate (CA; Mn ~ 50,000 by GPC) and curcumin from curcuma longa L. were

purchased from Sigma – aldrich, India. Acetic acid, 1, 2-dichloroethane and ethanol were

purchased from Sisco Research Laboratories Private Limited, India. All chemicals were used as

received without further treatment or purifications.

Electrospinning Process

A weighed amount of cellulose acetate powder was dissolved in different types of solvent

(acetic acid, dichloroethane and dichloroethane-ethanol (4:1 ratio)) in various solution

concentrations. The curcumin powder (0.5, 1 and 1.5 w/w %) and cellulose acetate powder were

co-dissolved in the mixture of dichloroethane-ethanol solvent and gently stirred continuously for

about 3 h at room temperature.

Figure.1 Electrospun polymer nanofibrous scaffolds (a) Drum collector

wrapped with aluminium foil, (b) Fibrous membrane deposited on

aluminium foil, and (c) peeling of fibrous membrane from aluminium

foil



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The prepared homogeneous solution was taken in a 2 ml syringe to which a needle tip of

0.56 mm inner diameter was attached. The electrospinning set-up used here has been described

earlier [6, 16]. The electric voltage, flow rate, the tip to collector distance was optimized at 22

kV, 1ml/h and 11 cm in all solutions for electrospinning process. The electrospun nanofibrous

membrane deposited on the aluminium foil in the drum collector and after peeling from the

collector is shown in Figure 1.

Characterization

The surface morphology of the prepared nanofibrous membrane was investigated using

FEI Quanta FEG 200 – HRSEM at 15 kV and TF 20: Tecnai at 200 kV. The average diameters

were determined by analyzing the scanning electron microscopic images with UTHSCSCSA

image tool software. The 1,1 diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity of

curcumin loaded cellulose acetate nanofibrous membrane was determined by the method of

Brand-Williams, Guelier & Berset, 1995 with some modifications [17]. The in-vitro curcumin

release from curcumin loaded cellulose acetate nanofibrous membrane was analyzed by High

performance liquid chromatography with ultra-violet detector at 450 nm.

Results and Discussion

Surface morphology

Figure. 2 shows the scanning electron microscopy images of the electrospun cellulose

acetate with different solvents (acetic acid, dichloroethane and dichloroethane-ethanol mixture in

the ratio 4:1) and 1 wt % curcumin loaded cellulose acetate. Electrospun cellulose acetate in

acetic acid solution produced large amount of beads with fibers due to high boiling point of

acetic acid (117.9 °C). High boiling point of the solvent makes it difficult to evaporate during

drafting process. However, dichloroethane in cellulose acetate when electrospun also resulted in

the formation of fibers with beads. A mixture of dichloroethane and ethanol (4:1) solvent was

used to dissolve cellulose acetate and electrospun which resulted in smooth continuous beadless

nanofibrous membrane. The cellulose acetate in dichloroethane and ethanol solution at 8 wt %

was electrospun into fibers which contained a few beads and these disappeared on increasing the

cellulose acetate concentration to 10 wt %. The average diameter of these fibers was found to be

120±30 nm. However, on further increasing the concentration of cellulose acetate solution to 12

wt %, the resultant average diameter of the fibers increased to 210±30 nm respectively. To



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obtain smooth fine nanofibers from beaded to non beaded morphology solution, cellulose acetate

concentration was fixed as 10 wt %. The use of suitable collector is also very important as it also

affects the fiber morphology of the electrospun cellulose acetate.

Figure. 2 Scanning electron microscopic images of the electrospun cellulose

acetate with different solvents (acetic acid, dichloroethane and dichloroethane-

ethanol) and different weight percentages (8, 10 and 12 wt %) and 1 wt % of

curcumin loaded cellulose acetate (10 wt %) using a flat collector

In the present work, two types of collectors (flat and drum) were used. On using flat

collector, electrospun cellulose acetate produced uniform porous nanofibers with rod like



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structure while on using a drum collector, the electrospun nanofibers were aligned, continuous

and uniform (Figure 3). Although, both aligned and non-aligned nanofibrous membrane are

suitable for drug delivery applications, since the nanofibrous membrane produced using drum

collector (110±40 nm) had a smaller diameter than the nanofibrous membrane produced using

flat collector (120±30 nm), the drum collector was used and optimized for electrospun curcumin

loaded cellulose acetate nanofibrous membrane.1 wt % of curcumin loaded cellulose acetate was

electrospun to form beadless, smooth nanofibrous membrane and the diameter range was

increased to 210±30 nm compared to cellulose acetate nanofibers 120±30 nm. The curcumin was

well dispersed in the cellulose acetate nanofibrous membrane and the average fiber diameter was

found to be 160±30 nm as seen in Figure 2. The transmission electron microscopic image of

electrospun curcumin loaded cellulose acetate nanofibers were seen in Figure 4. The

transmission electron microscopic image also confirms the dispersion of curcumin in curcumin

loaded cellulose acetate nanofibrous membrane.

Figure. 3 Scanning electron microscopic images of electrospun cellulose acetate

(10 wt %) using a drum collector



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Figure. 4 Transmission electron microscopic images of electrospun curcumin loaded

cellulose acetate nanofibrous membrane

Antioxidant activity

The anti-oxidant activities of the electrospun curcumin loaded cellulose acetate

nanofibrous membrane are shown in Figure 5. The DPPH assay was used to analyze the anti-

oxidant activity of the curcumin loaded cellulose acetate nanofibrous membrane.

Figure. 5 Antioxidant activity of curcumin loaded cellulose acetate nanofibrous

membrane a) Cellulose acetate nanofibrous membrane b) Curcumin loaded cellulose

acetate nanofibrous membrane



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Curcumin reacts with the electrophilic radicals initially, to form an ionized keto-enol

moiety, and the resulting neutral radicals lose a phenolic proton, thus yielding the phenoxyl

radical. In general, the presence of phenolic or β-diketone functional groups causes greater anti-

oxidant activity. Jovanovic et al (1999) reported that curcumin acts as an excellent hydrogen

atom donor, by donating the hydrogen atom from the central methylenic group than from the

phenolic group [18]. Barclay et al (2000) explained that curcumin has a good donating hydrogen

atom from the phenolic group, and also phenolic chain-breaking anti-oxidant activity [19].

Hence, the central methylenic hydrogen or the phenolic groups (heptadienone moiety) are

accountable for their anti-oxidant activity. The DPPH assay has been broadly used to evaluate

the radical-scavenging activity of the phenolic groups and their abilities to move hydrogen atoms

to radicals.

In-vitro curcumin release

In-vitro curcumin release was carried out, using the curcumin loaded cellulose acetate

nanofibrous membrane in phosphate buffer solution at pH 4 as shown in Figure 4. Three

different weight percentages of curcumin loaded cellulose acetate nanofibrous membrane were

studied (i.e. 0.5, 1 and 1.5 wt %). It was found that the in-vitro release pattern for the three

different weight percentages of curcumin loading did not provide any significant changes. Figure

6 shows that there was a burst release in the first 5 h, followed by a controlled release of

curcumin over a period of 120 h, and about 73 % of the curcumin was released. The presence of

small amounts of loosely bound curcumin on the surface of nanofibers might be the reason for

the initial burst release. Moreover, as the dissolution rate of the cellulose acetate near the surface

is high, the amount of curcumin release was also found to be high at the surface. In addition,

nanofibrous scaffold degradation and drug diffusion also influences the drug release behaviour

[20]. The hydrophilic nature of cellulose acetate enhanced the release rate of curcumin. The

percentage cumulative releases of 0.5, 1 and 1.5 wt % curcumin from the curcumin loaded

cellulose acetate nanofibrous scaffolds were found to be 72, 73 and 70 % respectively. Hence,

these results suggest that the hydrophilic electrospun cellulose acetate nanofibrous scaffold could

be used as an ideal nanocarrier, to deliver hydrophobic poor water soluble drug molecules, like

curcumin.



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Figure. 6 In-vitro curcumin release studies from different weight percentages of curcumin

loaded cellulose acetate nanofibrous membrane

Conclusions

The influence of solution concentration, solvents and collectors plays a major role

during electrospinning process of cellulose acetate. The fabrication of cellulose acetate

nanofibrous membrane for curcumin delivery was carried out by using an optimized

concentration of 10 wt % of cellulose acetate using a mixture of dichloroethane and ethanol (4:1)

as the solvent and flat collector. About 1 wt % of curcumin was loaded into the cellulose acetate

solution, and electrospun to produce uniformly distributed curcumin in the cellulose acetate

nanofibrous membrane, as confirmed by Transmission electron microscopy. Smooth, continuous

and beadless curcumin loaded cellulose acetate nanofibrous membrane was obtained in the range

of 160±30 nm which is suitable for drug delivery application was confirmed by Scanning

electron microscopy. The excellent anti-oxidant activity of the curcumin loaded cellulose acetate

nanofibrous membrane was confirmed by the DPPH assay. The percentage cumulative release of

curcumin showed slow, controlled and sustained release of curcumin over a period of 120 hours,



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and the curcumin release percentage were found to be 72, 73 and 70 % for 0.5, 1 and 1.5 wt % of

curcumin in the curcumin loaded cellulose acetate nanofibrous membrane.

Acknowledgement

We acknowledge UGC for the autonomy grant 2017-18 under which we have purchased

ESPIN NANO Electrospinning apparatus. Model : V1VHC, Sr. No. 20012018 in the Department

of Chemistry, Sri Sarada College for Women (Salem – 16).

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