Microbial resistant nanocurcumin-gelatin-cellulose fibers for advanced medical applications

Abstract

Curcumin, a greatly potent, non-toxic and naturally existing bioactive material in turmeric is widely employed to develop biomedical functional materials due to its environmental friendly nature. In general, curcumin functional materials were prepared by administrating non-aqueous solvents as a dissolving medium for curcumin. These non-aqueous solvents cause adverse effects for the environment and humans. However, if the curcumin functional materials are developed based on aqueous solution then the adverse effects can be eliminated. In view of this, for the first time aqueous based nanocurcumin (nanoparticles of curcumin) impregnated gelatin cellulose fibers (NCGCFs) were developed by a green process. The required nanocurcumin was prepared by ultrasonication process. Transmission electron microscopy showed the sizes of nanocurcumin exist in the range ∼2 to 15 nm. Nuclear magnetic resonance spectra showed no structural modification of nanocurcumin to that of curcumin. The developed fibres were characterized by fourier transform infrared spectroscopy, scanning electron microscopy, thermal analysis and swelling studies. Cumulative releasing studies showed slow and sustained releasing patterns for NCGCFs. A comparative antimicrobial study was performed for nanocurcumin impregnated gelatin cellulose fibres (NCGCFs) and curcumin impregnated gelatin cellulose fibres (CGCFs) against E. coli and S. aureus. The results indicated the superior performance of NCGCFs over CGCFs. Hence, NCGCFs prepared completely from naturally available materials can be considered as a novel kind of functional materials for wound dressing and antimicrobial applications.

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1. Introduction

In the case of bulk loss of tissue or nonhealing wounds such as burns, trauma, diabetic, decubitus and venousstasis ulcers, a proper wound dressing is needed to cover the wound area, protect the damaged tissue and if possible to activate the cell proliferation and stimulate the healing process.¹ For this purpose, a natural, non-toxic and biocompatible material is highly preferable based on environmental reasons.

Curcumin, a natural hydrophobic polyphenolic compound derived from the rhizome of the herb curcuma longa, possesses a wide range of biological activity including wound healing, anti-bacterial, anti-oxidant, anti-inflammatory and anti-cancer properties.^2–5 Though curcumin possess significant biomedical properties, it is poorly soluble in aqueous solvents.^6,7 This limits its clinical application. Of late, many researchers administrated non-aqueous solvents or combination of organic and aqueous systems as solvents for curcumin.^8–10 However, these approaches cause some undesirable effects for the human and the environment.^11–14 Owing to this researchers explored newer approaches which involve: the use of adjuvant like piperine that interferes with glucuronidation; the use of liposomal curcumin; the use of curcumin phospholipid complex; the use of structural analogues of curcumin.^15–17 But these methods seem to be expensive or complicated or to have a low performance.¹⁸ In that aspect, recently Bhawana et al. prepared nanocurcumin (nanoparticles of curcumin),¹⁹ which showed improved aqueous solubility, thereby it can be used directly instead of curcumin. In this investigation, to enhance the curcumin applicability in biomedical sciences, nanocurcumin was synthesized and used along with suitable natural polymers, gelatin and cellulose.

Gelatin, a water soluble protein derived from unwired helices of natural collagen, is widely used in biomedical applications,^20–23 particularly in designing wound dressing materials,²⁴ haemostatic agents,²⁵ tissue engineering scaffolds and drug delivery matrices.²⁶ In addition, it is pro-angiogenic,²⁷ non-immunogenic,²⁸ biocompatible, biodegradable²⁹ and exhibits low inflammatory cell response without side effects in the host tissue.³⁰ Further, gelatin absorbs excess wound exudates because of its excellent ability to absorb water more than 5–10 times as weight as itself.³¹

In our recent study, natural polymer with silver nanoparticles impregnated cellulose fibres has confirmed significant antibacterial properties.³² In surgical zone, cellulose fibres gained medically more importance as designing material for scaffolds. Cellulose fibre contains cellulose, a homopolymer of β-D-glucopyranose units linked together by (1 → 4)-glycosideic bonds.³³ Cellulose fibres as a scaffold supports injured limb or wound, absorbs blood and secretions exudates and provide pain relief. It serves as the protective dressing for wound, thereby preventing wound contamination from outside environment. Hence, developing antimicrobial property for cellulose fibres is an advantageous step in improving medical standards in the area of surgical zone.

In view of above, a significant attempt was made to develop nanocurcumin-gelatin cellulose fibres (NCGCFs) for advanced antimicrobial applications by utilizing completely natural materials. A comparative antimicrobial study was performed for NCGCFs and curcumin impregnated gelatin cellulose fibres (CGCFs). The results indicated the superior performance of NCGCFs over CGCFs. So far, no work was reported on the nanocurcumin impregnated cellulose fibres. For the first time nanocurcumin impregnated gelatin cellulose fibers (NCGCFs) were developed by eco-friendly green process. The improved therapeutic potentialities of nanocurcumin fibres, obtained by following environmental friendly approach is a promising tool to curb micro-organisms and will open a new era in modern bio-medical applications.

2. Experimental Procedures

2.1. Materials

Curcumin (assay of 98%) supplied by Sigma Aldrich (Bengaluru, India). Cotton cellulose fibres (1 mm thickness) were purchased from SIMCO thread mills (Salem, Chennai, India). Gelatin (GT; product no. 54045) was obtained from S.D. Fine Chemicals (India). Dichloromethane (DCM) purchased from Merck specialities Pvt. Ltd (Mumbai, India). All the chemicals used in this work are of analytical grade. Double distilled water was used thorough out the experiments.

2.2. Synthesis of curcumin nanoparticles (nanocurcumin)

Curcumin nanoparticles were prepared by ultrasonication technique. In a typical synthesis, 1 mL of curcumin solution (0.5 w/v%) prepared from dichloromethane (DCM) was sprayed dropwise into 50 mL boiling water at a flow rate of 0.2 mL min⁻¹ under ultrasonic conditions, with an ultrasonic power of 100 W and a frequency of 30 kHz, similar to the method adopted by Bhawana et al.¹⁹ After 15 min sonication, the contents were stirred at 200–800 rpm at ambient temperature for about 20 min till all the dichloromethane was evaporated and a clear orange-colored solution was remained. The solution was ultracentrifuged for 20 minutes at 12 000 rpm and freeze-dried to obtain curcumin nanoparticles (nanocurcumin) and utilized for further studies.

2.3. Preparation of nanocurcumin-gelatin cellulose fibres (NCGCFs) and curcumin-gelatin cellulose fibres (CGCFs)

Finely aqueous dispersed nanocurcumin of various concentrations in water (10 mg per 5 mL, 15 mg per 5 mL and 20 mg per 5 mL) were prepared by sonicating the respective solutions for 15 min. To each of the solutions, 50 mL (1% w/v) gelatin solution was added. The contents were stirred over orbital shaking incubator at 250 rpm with an ambient temperature of 27 °C for 4 h, followed by 15 min sonication to obtain homogeneous nanocurcumin gelatin solutions. For the obtained homogeneous solutions, 500 mg of pre-weighed and washed cellulose fibres were immersed, stirred for 4 h at 250 rpm at an ambient temperature and sonicated for 15 min to acquire nanocurcumin impregnated gelatin cellulose fibres (NCGCFs). Finally, various formulations of NCGCFs (NCGCF-10, NCGCF-15 and NCGCF-20) were taken out, air dried and kept in dessicator for further characterizations.

Analogous to NCGCFs, similar formulations of curcumin impregnated gelatin cellulose fibres, CGCFs (CGCF-10, CGCF-15 and CGCF-20) were prepared directly by taking various concentrations of curcumin solution (DCM as solvent) instead aqueous nanocurcumin dispersion. The synthesis routes for NCGCFs and CGCFs were shown in Scheme 1.

Scheme 1 Schematically illustrating the synthesis routes for NCGCFs and CGCFs.

2.4. Characterizations

The morphology of obtained nanocurcumin was observed with transmission electron microscopy (JEM-1200EX, JEOL, Tokyo, Japan), performed by placing a drop of the aqueous nanocurcumin dispersion (10 μL; 2 mg mL⁻¹) on the 3 mm copper grid and allowed it to dry at ambient temperature. ¹H NMR spectra was obtained in CDCl₃ using Bruker DRX 300 MHz NMR spectrophotometer. Fourier transformed infrared spectroscopy (FTIR) was conducted to investigate the possible chemical interactions among cellulose fibres, gelatin and nanocurcumin by using a Perkin Elmer (Model Impact 410, Wisconsin, MI, USA) spectrophotometer over the scanning range 500–4000 cm⁻¹. Scanning electron microscopy (SEM) was utilized to observe the surface morphology (JEOL JEM 7500F, Tokyo, Japan) of the developed fibres at an accelerating voltage 3 kV. All samples were gold coated previous to examination with a filed SEM. The thermal analysis was conducted on SDT Q 600 thermal analyzer (T. A. Instruments-water LLC, Newcastle, DE, USA), at a heating rate of 20 °C min⁻¹ with 100 mL min⁻¹ nitrogen gas flow rate. Curcumin/nanocurcumin releasing patterns of the fibres were monitored by using UV-Vis spectrophotometer (Elico-SL 164, Hyderabad, India).

2.5. Cumulative releasing studies

Recent studies have indicated that it is important to know the antibacterial activity over a period of time. To provide efficient antibacterial activity over a period of time a stable and prolonged release of curcumin/nanocurcumin is necessary. In order to study the release of curcumin/nanocurcumin from the developed fibres, known weights of fibres were placed in a measured volume (5 mL) of 7.4 pH buffer at 37 °C and the released amount of curcumin was determined at different time intervals by recording the absorbance of release medium by UV-Vis spectrophotometer. The absorption of the solutions of curcumin was measured at λ_max 491.2 nm.²

2.6. Swelling properties

The swelling ratio or swelling capacity (S_g/g) of all the fibres developed was determined by swelling them in phosphate buffered saline (PBS), pH 7.4 for 24 h at 37 °C using eqn (1):

Swelling ratio (S_g/g) = [W_s − W_d]/W_d (1)

where, W_s and W_d denote the weight of the swollen cellulose fibre at equilibrium and the weight of the dry cellulose fibre, respectively. The data provided is an average value of 3 individual sample readings.

2.7. Antimicrobial activity

The antimicrobial activity of developed fibres was tested against Staphylococcus aureus (G+) MTCC-7443 and Escherichia coli (G −) MTCC-1668, obtained from the Institute of Microbial Technology, Chandigarh, India. The required nutrient agar medium was prepared by mixing peptone (5.0 g), beef extract (3.0 g), sodium chloride (5.0 g) and agar (15.0 g) in 1000 mL of distilled water and the pH was adjusted to 7.0.^34,35 The agar medium was sterilized in a conical flask at a pressure of 6.8 kg (15 lbs) for 30 min and transferred into sterilized petri dishes in a laminar air flow chamber (Microfilt Laminar Flow Ultra Clean Air Unit, Mumbai, India) for solidification. After solidification, 50 μL (10⁸ CFU mL⁻¹) of microbial culture was uniformly spread out. Over the petri dishes, fibres (NCGCFs/CGCFs) each of 5 mm length were distributed and incubated for 24 h at 37 °C to obtain inhibition zones. Finally, the formed inhibition zones were measured and photographed.

3. Results and discussions

Ordinary wound dressings allow microorganisms to exhibit undesirable effects on wounds. This is one of the main factors for disease transmission and subsequent tissue damage.³⁶ This factor has stimulated to develop microbial resistant nanocurcumin impregnated gelatin cellulose fibers (NCGCFs) for wound dressing scaffolds. Further, employing curcumin as nanoparticles (nanocurcumin) has exhibited pronounced activity than administering directly as curcumin.¹⁹ The method adopted to develop NCGCFs was a green process, feasible at ambient conditions without the aid of any external chemical agent. The process of preparing antimicrobial fibres (NCGCFs) was systematically illustrated in Scheme 1: Step 1: preparation of nanocurcumin by a physical ultrasonication process. Step 2: preparation of aqueous nanocurcumin dispersion. Step 3: fabrication of antimicrobial NCGCFs from cellulose fibres.

To compare the enhanced results of NCGCFs, curcumin impregnated gelatin cellulose fibres (CGCFs) were also prepared by taking curcumin solution (DCM as solvent). The synthesis route for CGCFs was shown in Scheme 1. The key role of gelatin is to stabilize the nanocurcumin with cellulose fibres and also to release the nanocurcumin in sustained manner for longer duration. Gelatin was particularly chosen due to its wide applications in biomedical field, particularly in designing wound dressings materials. It also exhibits low inflammatory cell response without side effects in the host tissue.³⁰

Examination of nanocurcumin by TEM (Fig. 1A(a–c)) showed the nanoparticles were spherical in shape and exists in the size range of ∼2 to 15 nm. The quite interesting aspect of nanocurcumin was, though it was physically compacted to nanodimension, it was structurally not altered and showed NMR spectrum similar to that of the pure curcumin (Fig. 1B). In ¹H NMR spectra (Fig. 1B), the peaks at δ 3.951 and 5.802 ppm showed the presence of intact methoxy groups and the methine proton in enolic form. The peaks in the range of δ 6.841–7.138 ppm showed the presence of aromatic protons.¹⁹ Two doublets were assigned for olefinic protons at δ 6.504 and 7.618 ppm respectively and were coinciding with those many of previously reported literatures. Over all, NMR spectra suggested the chemical integrity of nanocurcumin was identical to that of curcumin. Structure of curcumin and the ¹H NMR spectra of nanocurcumin were presented in Fig. 1B.

Fig. 1 (A) TEM images of nanocurcumin (a–c) and (B) ¹H NMR spectra of nanocurcumin in CDCl₃ and structure of curcumin.

To understand the morphology of the fibres, SEM examination was carried out for NCGCF, CGCF, gelatin-cellulose fibre and pure cellulose fibre. SEM image of NCGCF (Fig. 2A) clearly depicts the uniform distribution of curcumin nanoparticles over gelatin bound cellulose fibre which were highly stabilized by hydrophilic groups of gelatin. In case of CGCFs (Fig. 2B), irregular distribution of bulky curcumin with less stabilized by hydrophilic groups of gelatin could be seen. Fig. 2E represents SEM image of pure cellulose fibre. The SEM image of gelatin-cellulose fibre (Fig. 2D) were prepared from 1% gelatin solution that was used in the synthesis of NCGCFs/CGCFs showed a smooth surface without any particle distribution. This indicates that the distributed particles in case of NCGCFs and CGCFs are only due to nanocurcumin/curcumin respectively. Also it could be clearly seen from Fig. 2A and B that due to size factor, curcumin in its nano form exists more in number and more in quantity over NCGCFs than in bulk form over CGCFs. Further, the presence of nanocurcumin/curcumin over gelatin bound cellulose fibres was technically confirmed through its bonding interactions by using FTIR spectral data and thermal data.

Fig. 2 SEM images of (A) NCGCFs fibre, (B) CGCFs fibre, (D) gelatin-cellulose fibre, (E) pure cellulose fibre, and (C) FTIR spectra of pure cellulose fibre, nanocurcumin, gelatin and NCGCFs fibre.

FTIR spectroscopy is an important tool that indicates the combined interaction of nanocurcumin, gelatin and pure cellulose fibre in NCGCFs fibres. The spectra of pure cellulose fibre, nanocurcumin, gelatin and NCGCF were shown in Fig. 2B. For pure cellulose fibre, characteristic peaks at around 3364 cm⁻¹, 2924 cm⁻¹ and at around 1311 cm⁻¹ corresponding to –OH stretching frequency, >CH₂ stretching vibration and C–H bending mode respectively; characteristic bands at 1150 and 1015 cm⁻¹ are assigned to the C–O–C from the glucosidic units or from β-(1 → 4)-glucosidic bonds.^37,38 For nanocurcumin, the bands observed at 3346 cm⁻¹, 1591 cm⁻¹, 1508 cm⁻¹, 1263 cm⁻¹, and 1142 cm⁻¹ are respectively attributed to the phenolic O–H stretching, stretching vibrations of the benzene ring, C=C vibrations, aromatic C–O stretching and C–O–C stretching modes.³⁹ Gelatin showed characteristic peaks at 3284 cm⁻¹ due to N–H stretching, at 1634 cm⁻¹ due to C=O stretching (amide I), at 1540 cm⁻¹ due to N–H bending (amide II) and at 1236 cm⁻¹ due to C–N (amide III).^40,41 The spectra of NCGCFs comprise a composite of the cellulose fibre, nanocurcumin and gelatin, displaying all the characteristic bands of cellulose fibre, nanocurcumin and gelatin. This clearly indicates their bonding interaction.

Thermal property of fibres is a valuable piece of evidence that provides the information on physical characteristics and the components present in the fibres as well. The primary thermogram of the fibres was shown in Fig. 3A. The results indicated that, in all the samples, an initial weight loss at a temperature below 100 °C was observed due to the loss of moisture present on the surface. The initial degradation of NCGCFs occurs at around 290.67 °C, higher than all of its individual components and the final degradation temperature occurs at around 398.48 °C. The thermal decomposition residue of NCGCFs at 600 °C was 25.04%, an intermediate value of the remaining thermal residues (cellulose fibre (15.45%), gelatin (23.97%) and nanocurcumin (28.94%)). The intermediate value indicates that all the components in NCGCF were well bound to give a normalized result. Based on the thermal data, it was evident that in NCGCFs all the components were well bind as a composite to exhibit good thermal stability.

Fig. 3 (A) TGA curves of pure cellulose fibre, gelatin, nanocurcumin and NCGCFs fibre, (B) % cumulative releasing studies of CGCF-20 and NCGCF-20.

3.1. Cumulative releasing studies

The cumulative releasing studies (Fig. 3B) demonstrated that the rate of curcumin/nanocurcumin release is different for NCGCFs and CGCFs. In comparison with both the fibres (NCGCFs and CGCFs), CGCFs release curcumin at a faster rate than NCGCFs. CGCFs released all the amount of curcumin that present in it at about 16 h where as NCGCFs showed at about 60 h. The observed slow and sustained release of nanocurcumin from NCGCFs was due to more stabilization of nanocurcumin by the hydrophilic groups of gelatin, owing to its size factor. The prolonged release of nanocurcumin from NCGCFs suggests the usefulness of the product towards wound care applications for a longer duration.

3.2. Swelling ratio

Swelling ratio plays a significant role in biomedical applications, particularly in antibacterial applications. In the present investigation, the swelling ratios of fibres were measured at an ambient temperature by using a gravimetric method.³⁵ Initially known weight of dried fibres was immersed in 50 mL phosphate buffered saline (PBS), pH 7.4 for 24 h at 37 °C. The fibres were then removed and their surfaces were blotted with filter paper and weighed. The swelling patterns of the fibres (NCGCFs/CGCFs) were illustrated in Fig. 4.

Fig. 4 Swelling behavior of (A) cellulose fibre and various formulations of CGCFs (CGCF-10, CGCF-15 and CGCF-20) and (B) cellulose fibre and various formulations of NCGCFs (NCGCF-10, NCGCF-15 and NCGCF-20).

It was noticed primarily that the swelling ratios of the developed fibres (NCGCFs/CGCFs) were higher than that of pure cellulose fibre. The significant result was due to the hydrophilic nature of gelatin that bound to the developed fibres of NCGCFs/CGCFs, which could able to absorb water more than 5–10 times as weight as itself.³¹ Secondly, from Fig. 4A and B, it was clear that the swelling ratio of the fibres (both NCGCFs and CGCFs) increases with increase in concentration of curcumin/nanocurcumin. It was predicted that the existed voids between the particles (curcumin/nanocurcumin) act as both facilitating and trapping network for incoming water molecules to interact further with gelatin and to accumulate over the fibre. The phenomenon can be comparable with various hydrophilic hydrogel systems.²⁴ The proportionately increase in number of voids with increase in concentration of curcumin/nanocurcumin provides scope for much more water molecules to retain in the voids and accumulate over the fibre, resulting increased swelling ratio values for both NCGCFs and CGCFs with increase in concentration. Further, for the same concentration, the swelling ratio values of NCGCFs (Fig. 4B) are higher than CGCFs (Fig. 4A). This was due to ‘size factor’ and ‘aqueous–nanocurcumin interaction’. Due to size factor, for the same quantity of material, stoichiometrically nanocurcumin exists more in number than bulk curcumin, thereby stoichiometrically more number of voids will exist to retain more number of water molecules in case of NCGCFs. Apart from this, size factor allows smaller nanocurcumin to distribute more uniformly with well defined voids over NCGCFs, whereas, these well defined voids were absent in case of CGCFs. Owing to these reasons, comparatively large amount of water molecules will be retained and accumulated in the more and well defined voids of NCGCFs than lesser irregular voids of CGCFs, resulting higher swelling for NCGCFs. The other factor that contributes for higher swelling of NCGCFs is ‘aqueous–nanocurcumin interaction’. Compared to bulk curcumin, nanocurcumin possesses higher aqueous interaction which also enhances the swelling of NCGCFs.¹⁹ Hence, it was concluded that when all the relative components in NCGCFs and CGCFs were being equal, the enhanced swelling ratio of NCGCFs was due to ‘size factor’ and ‘aqueous–nanocurcumin interaction’. Overall, swelling data significantly confirms that the developed fibres were good absorbents for blood and secretions exudates, which is very essential for wound dressing applications.

3.3. Antimicrobial activity

The main objective of this study is to develop aqueous based environmental friendly microbial resistant fibres by effective utilization of curcumin. Keeping this in view, novel nanocurcumin fibres were developed as effective antimicrobial agents against E. coli and S. aureus. Fig. 5 illustrates the antimicrobial efficiency of the developed fibres (NCGCFs/CGCFs). The inhibition zones exhibited by all the fibres (NCGCFs/CGCFs) were found to be in the range 2.5–6 mm. According to the Standard Antibacterial test “SNV 195920-1992”, specimens showing more than 1 mm microbial zone inhibition can be considered as good antibacterial agents.⁴² Hence, the fibres developed were considered as good antibacterial agents, effective in killing the bacteria. From Fig. 5, it was noticed that NCGCFs, developed based on aqueous solution showed better inhibition zones than CGCFs, developed based on non-aqueous solvent (DCM). This clearly indicates the superior performance of nanocurcumin impregnated gelatin cellulose fibres (NCGCFs). The superior performance was due to presence of quantitatively and stoichiometrically more nanocurcumin molecules over NCGCFs than CGCFs that involved in bacterial devastation process. Due to increase in quantity and nanocurcumin number, more number of curcumin nanoparticles will be released from NCGCFs and act on relatively more number of bacterial colonies and destroy, resulting higher bacterial inhibition zone for NCGCFs than CGCFs. Also, as the antibacterial activity was performed over a period of 24 h, the amount of curcumin that act against the bacteria is the amount of curcumin that released from fibres at 24 h. The amount of curcumin release (%) can be calculated from the % cumulative release curves (Fig. 3B). It was clearly evident from Fig. 3B that by the time 24 h, CGCFs releases all its impregnated curcumin, where as NCGCFs releases only 80.24% of curcumin. This indicates that though the antibacterial activity of CGCFs was due to 100% release of curcumin, the concerned inhibition zones exhibited by CGCFs were less than the inhibition zones exhibited by NCGCFs where the curcumin release was only 80.24%. This indicates the higher efficiency of the NCGCFs fibres than CGCFs. Further, to confirm the higher efficiency of NCGCFs than CGCFs in curbing the bacteria, antibacterial test was performed for the similar concentrations of homogeneous curcumin and nanocurcumin gelatin solutions, which were used during synthesis of NCGCFs and CGCFs. The test was carried out by maintaining the conditions similar to the conditions that were maintained for antibacterial test for fibres. The results undoubtedly reached the predicted expectations and showed higher inhibition zones for nanocurcumin gelatin solutions than curcumin gelatin solutions, suggesting the higher efficiency of nanocurcumin and thereby nanocurcumin impregnated NCGCFs. With these results, it was concluded that the higher inhibition zones exhibited by NCGCFs were not duly as a result of quantitative and stoichiometric parameters but impact of nanocurcumin was also played. Based on above experimental findings, NCGCFs exhibited enhanced antimicrobial efficiency seems to be appropriate.

Fig. 5 Antibacterial activity against (A) E. coli and (B) S. aureus exhibited by (o) pure cellulose fibre, (a) CGCF-10, (b) CGCF-20, (c) NCGCF-10 and (d) NCGCF-20.

It was reported that antimicrobial action of phenolic compounds was related to the inactivation of cellular enzymes, which depended on the rate of penetration of the substance into the cell or caused by membrane permeability changes.⁴³ Higher surface area of curcumin nanonanoparticles provides comparatively more interaction surface for nanocurcumin to interact with bacteria and smaller size of it facilitates to penetrate more effectively inside the cell wall, causing bacterial death. In over all, the mechanism of antibacterial activity was believed to be anchoring of nanocurcumin to the cell wall of the bacterial cell, breaking it, and then penetrating inside the cell. The penetrated nanocurcumin disrupt the cell organelles and kill the cell through lysis.¹⁹ The antibacterial activity was more pronounced against S. aureus (G+) than E. coli (G−) due to which inhibition zones were formed higher for S. aureus (G+) than E. coli (G−) (Fig. 5). This variation in antibacterial activity is due to the difference in their cell membrane constituents and structure.¹⁹ It is known that S. aureus (G+) contain an outer peptidoglycan layer, while E. coli (G−) contain an outer phospholipidic membrane, both of which undergo different types of interaction when encountered by curcumin.¹⁹

4. Conclusion

From the present investigation, aqueous based nanocurcumin impregnated gelatin cellulose fibers (NCGCFs) were developed as effective antimicrobial agents. The process adopted was a green process and the materials employed were of natural origin. The developed NCGCFs showed more pronounced antibacterial activity than CGCFs. Hence, NCGCFs have great potential for their utilization in wound/burn dressings as well as in the fabrication of antibacterial finishings and textiles.

Acknowledgements

The author (IF 110192) wish to acknowledge the Department of Science & Technology (DST, INIDA) and Ministry of Science & Technology for providing financial assistance through Innovation In Science Pursuit for Inspired Research (INSPIRE) programme. The authors (KVP) thank the Fondecyt Proyecto no.: 3130748 Chile (South America).

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