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Abstract

The functional effect of an essential oil (EOs) blend in the form of a microcapsule was studied and applied to woven linen fabric to meet the requirements of medical textile products. Four EOs (eucalyptus, lavender, aloe vera, and citronella) were blended at three levels to prepare the microcapsules. The Box & Behnken method was adopted for sampling. Eight microcapsules were chosen from 15 samples based on their antibacterial effect. These microcapsules were prepared through a complex coacervation method and then applied to woven linen fabric by the dip method, which can benefit uniformity, penetration, and suitability for delicate fabrics. The capsule size and presence were confirmed by scanning electron microscope (SEM) Optical Microscope (OM) images. Fourier Transform Infrared spectroscopy (FTIR) and energy-dispersive X-ray spectroscopy (EDX) were used to identify the elemental composition and functional groups. The fabric samples L1 and L5 show significant antibacterial inhibition ( 25 & 20 mm, respectively) against E. coli and S. aureus. Samples L7 and L12 exhibited exceptional antibacterial activity against Enterococcus, with inhibition zones of 30 and 27.8 mm. Sample L7 showed a significant effect on mosquito-repellent effect, maintaining approximately 90% efficacy both before and after washing, in comparison to the untreated sample. The antioxidant activity of the samples L1, and L7 are in the range of 70% to 80%. The drug release of samples L7 and L11 is high (80 to 90%) in an ethanol-water system derived from Higuchi’s model. Hence the approach may be recommended for medical textile products.

Graphical Abstract

Keywords

Chitosan gum Arabic microencapsulated linen fabric eucalyptus oil lavender oil and aloe vera

Introduction

As EOs are gaining popularity, a variety of applications: including aromatherapy, cosmetics, and therapeutic and medical applications are being researched. The significance of EOs has increased in various sectors, such as food production, medicines, and perfume manufacturing as these oils are extracted from the stems, leaves, flowers, resins, barks, and roots of various plants. EOs comprised of the following which all contribute to their distinct scents: various compounds such as phenols, alcohols, monoterpenes, sesquiterpenes, amines, linalool, heterocycles, and ketones, which all contribute to their distinct scents.^1,2 Owing to its complex chemical makeup, it has unique physicochemical properties, which provide antiviral, antibacterial, antifungal, and anti-inflammatory properties. EOs were generally volatile and could be easily affected by light and oxygen.^3,4 EOs are microcapsule-applied fabrics with polymers, chitosan and gum Arabic that modulate the rate of oil release and enhance the stability of the active ingredient during oxidation and storage.³ Among the EOs, eucalyptus oil was effective against the herpes simplex virus, adenovirus, and mumps to heal the respiratory systems due to 1,8-cineole and eucalyptol compounds.^4,5 Eucalyptus oil comprises of diverse blend of monoterpenes, sesquiterpenes, and various aromatic compounds, including phenols, oxides, ethers, alcohols, esters, aldehydes, and ketones. Its constituents include 1,8-cineole (eucalyptol), citronellal, citronellol, citronellyl acetate, p-cymene, eucamalol, limonene, linalool, α-pinene, γ-terpinene, α-terpineol, and aromadendrene. Eucalyptus oil has demonstrated various biological activities, including antioxidant, antimicrobial, insecticidal, antibacterial, and antifungal properties.^6,7

Aloe vera is a plant that contains various substances, including amino acid polysaccharides, vitamins, enzymes, minerals, sugars, lignin, and saponins. It has been traditionally utilized for treating various diseases.^8,9 Acemannan, a long-chain with immuno-modulat, antibacterial, antifungal, and anticancer properties, has been identified as an important functional component of Aleo-vera. This polymer is composed of linear D-mannopyranosyl units that have been randomly acetylated. Aloe vera was widely used for various applications in textiles such as wearable electronics, UV protection, medical textiles, tissue engineering, wound healing, and curative garments.^10,11 Lavender (Lavandula Augustifolia) is used in medical and cosmetic products owing to the presence of components such as linalool, terpineol-4-ol, lavender, alpha terpinene, 1,8-cineole, limonene, and, trans-β-ocimene. Linalool and linalyl acetate are the two major components that have antibacterial, antifungal and aromatherapy effects through massage and inhalation.^12,13 Citronella belongs to the family of (Cymbopogon nardus (L.) Rendle) and is a good mosquito repellent because of the presence of active compounds such as limonene, 1,8-cineole, geraniol, and citronellal.¹⁴ Owing to their therapeutic benefits, microcapsules loaded with EOs for various applications. The capsule cover design comprises a shell cover and a room for EO loading.

Most gums dissolve in water to varying extents, depending on their concentration, but Gum Arabic is unique in that it dissolves easily in both cold and hot water at concentrations of up to 50% W/W. Its extensive use is attributed to its exceptional solubility, lower viscosity compared to other polysaccharides, excellent emulsifying properties, and non-toxic nature.^15–17 It was reported that microcapsules used gum Arabic as the shell material and thyme essential oil as the core. They found that gum Arabic acts as an effective emulsifier, which leads to a slower initial release rate of the essential oils compared to microcapsules without gum Arabic. This slower release is attributed to the protective effect gum Arabic has on the essential oil, enhancing its stability and controlling the rate at which it is released¹⁸.

Chitosan is a positively charged biomolecule with antibacterial properties. Chitosan can be used in the preparation of microcapsules as a cover membrane to protect the loaded drugs effectively.¹⁹ Furthermore, gum Arabic and chitosan blends are renewable, biodegradable, biocompatible, and considered the most intriguing biopolymers. It was observed that the gum Arabic was used for preparing microcapsules loaded with limonene and vanillin oil, with the aid of chitosan. The gum Arabic formed an outer layer of microcapsule that protects and controls the release of essential oils.^20,21

The novelty may lie in investigating the combined functional effects of capsules loaded with a blend of three essential oils derived from unique species, applied at the fabric stage.

This research focuses on 100% linen woven fabric for microencapsulation and also analyzes its functional properties such as antibacterial, antivirus, antioxidant mosquito repellent, etc for developing medical textiles such as bed sheets.

Materials and methods

Materials

During this research, the following polymers have been purchased from SRL Pvt. Ltd (India): gum Arabic, low molecular weight chitosan (85% degree of deacetylation), acetic acid, ethanol, and surfactants (tween 20, tween 80, and sodium lauryl sulfate (SLS)).

EOs such as eucalyptus, lavender, and citronella oils were procured from TNEOEOD, Ooty. Aloe vera was purchased from Veda Oils, New Delhi (India). A 100% linen woven fabric (EPI = 64 and PPI = 55, warp count: 32s and weft count: 32s, plain weave, cover factor 17.3) with a weight of 137 g per square meter) was purchased locally.

Methods

Capsule preparation and encapsulation

Microcapsules were developed using at complex coacervation technique, which involves the interaction between oppositely charged polyelectrolytes in a water-based solution. This method is highly favoured owing to its numerous benefits, such as a high loading capacity, excellent encapsulation efficiency of up to 99%, and cost-effectiveness, making it suitable for a wide range of applications.²²

In this method, three solutions were prepared. The first solution was prepared by dissolving 2 g of chitosan in a mixture of 50 mL of water and 1 mL of acetic acid and then agitating the mixture with a magnetic stirrer for 15 hours.

The second solution comprises three different EOs eucalyptus, Lavandula Augustifolia, aloe barbadensis and citronella. This solution had three levels of prepared EO blends for analysing the functioning of linen fabric as shown in Table 1 and Table 2. Additionally, the surfactants: SLS, Tween 20, and Tween 80 were added to reduce the surface tension and to make the EOs non-volatile. The SLS is an anionic surfactant and emulsifier, it exhibits some antimicrobial activity. This helps to achieve higher loading efficiency during capsule formation than others.²³

Table 1.

Design of experiment (DOE).

Sl. No.	Variables		Level
Sl. No.	Variables		−1	0	1
1	X1	Eucalyptus	1 mL	2 mL	3 mL
2	X2	Aloe vera	1 mL	2 mL	3 mL
3	X3	Lavender	1 mL	2 mL	3 mL

Table 2.

Box-behnken design.

Variables
Experiment no.	X1	X2	X3
1	1	1	2
2	3	1	2
3	1	3	2
4	3	3	2
5	1	2	1
6	3	2	1
7	1	2	3
8	3	2	3
9	2	1	1
10	2	3	1
11	2	1	3
12	2	3	3
13	0	0	3
14	0	3	0
15	3	0	0

To dissolve gum Arabic, a third solution was prepared by mixing 50 mL of water with 3 g of gum Arabic. The mixture was stirred at 500 r/min while maintaining a temperature of 45°C for 2 hours. In step four, the chitosan solution was mixed with a blend of three EOs to facilitate the formation of micelles. SLS, Tween 20, and Tween 80 were blended in equal proportion to form an emulsifier. Micelle formation helps EOs become non-volatile. A magnetic stirrer for 35 minutes at 600 r/min while maintaining 40°C temperature. Finally, microcapsules are created during agitation by adding gum Arabic and chitosan droplets to the solution.

In the final stage, complex coacervation was induced by adding 1 mL of Hcl to lower the pH and decrease the speed of the microcapsule’s solution from 600 to 400 r/min. Subsequently, an ice bath is used to progressively lower the temperature of the microcapsule solution from 40°C to 5°C. To harden the microcapsules, 7 mL of tannic acid is gradually added ensuring to maintain the same temperature and stirring speed. A flow chart of the microcapsules is shown in Figure 1.

Figure 1.

Procedure to produce microcapsule via complex coacervation.

Encapsulation efficiency

Among the 15 microcapsule-treated samples, encapsulation efficiencies varied between 65% −96%. Five samples with moderate to high efficiencies were selected for application to the linen fabric to evaluate various performances as shown in Table 3.

Table 3.

List of identified capsules.

Sample no.	Concentration as blend ratio	Encapsulation efficiency (%)
Linen 1	1:1:2	74
Linen 5	3:2:1	77
Linen 6	1:2:3	75
Linen 7	3:2:3	80
Linen 8	3:2:3	70
Linen 11	2:1:3	85
Linen 12	2:3:3	68
Linen 13	0:0:3	72

Grafting and microcapsule-application of linen fabric

Citric acid and monobasic sodium phosphate monohydrate are used as nontoxic cross-linkers to enhance the affinity of fabric towards microcapsules by ester bonds.²¹ The Raw linen fabric samples were treated in a solution containing 3% w/v citric acid and 2.5% w/v sodium phosphate monobasic monohydrate as a catalyst as shown in Figure 2. The process was initially performed for 20 minutes at 50°C. Then, washed twice with deionized water and for encapsulation detailed in Table 3, along with a constant 0.5 mL of citronella. The encapsulation process was performed in a chemical bath (prepared based on a 1:30 material-to-liquor ratio) for 45 minutes at 70°C. Then, followed by curing for 10 minutes at 80°C in an oven for fixation.

Figure 2.

SEM Image: (a) Raw fabric (b) Cross-linked fabric.

Characterization of the microcapsule-applied linen fabric

Microstructure analysis

The presence and microstructure of the capsules were analyzed by employing SEM (Model: Zeiss Evo 18) in secondary electron mode. The elemental composition and proportion of the capsules were observed through EDX. The presence of various functional groups in the microcapsules was observed using FTIR (Model: Thermos Scientific Nicolet apex) in the ATR mode. Thermogravimetric analysis (TGA - SDT-Q600) was used to examine the thermal behaviour associated with the mass loss of the microcapsules in a nitrogen atmosphere at a uniform heat rate of 20°C per minute.⁹ The size distribution of the microcapsules was observed through a particle size analyzer (Microtrac nanotrac wave II) and optical microscope (OM - Zeiss Axiocam Erc5s).

Functional properties

The antibacterial activity of the microcapsule-applied fabrics and raw linen fabric was assessed according to AATCC-147. The bacterial inhibition of the fabric is tested for both the gram-positive (Enterococcus and Staphylococcus aureus), and gram-negative (E. coli). The process of creating AATCC plates were created by filling sterile petri dishes with 15 mL and allowing them to set. Then, a sterile L-shaped rod was used to uniformly distribute 0.1% concentration of the cultivated inoculum throughout the Petri dishes. Next, the plates were allowed to air-dry.^24,25 The microcapsule-applied fabric with a diameter of 6 mm was placed on the AATCC medium and incubated for 18 to 24 hours at 37°C. After the entire incubation period, the zone of inhibition were analysed for all samples.

The mosquito repellence test was performed using an Excito chamber designed to meet the regulations of the World Health Organisation WHO (Reference No. WHO/CTD/WHO PES/IC/96.1). The chamber contained a sample holder for the test samples. A mosquito fly path was built to approach the fabric samples inside the chamber. Ten live female Anopheles stephensi mosquitoes were collected to starved for approximately 6 hours before testing. Then they are allowed to pass through the chamber inlet and the movement towards the raw and microcapsule-applied samples (L7) is observed.²⁶ The antioxidant properties of the raw and microcapsule-applied fabric were evaluated using 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals, as described previously²⁷.

Result and discussion

Capsule size distribution and microstructure

Optical microscope

As shown in Figure 3, the optical microscope conforms to the presence of the microcapsules with sizes ranging from 4 µm to 11 µm. The microcapsules were observed at image resolutions of 20 µm and 50 µm image resolution.

Figure 3.

OM images: (a) Capsules at 20 µm resolution & (b) Capsules at 50 µm resolution.

Particle size analyser

A particle size analyser was used to observe the microcapsules and understand the size distribution of the particles in the sample as shown in Figure 4. The size distribution of the microcapsules is presented in Table 4 and was found to have a range of 100 to 1000 µm. The homogeneity of the microcapsule size was evaluated using polydispersity (PDI) value. The PDI of the test sample was 0.2766, which was less than the value. The PDI value was in line with as investigated by.²⁸

Figure 4.

Distribution of capsule size.

Table 4.

Statistical analysis of capsule size distribution.

Diameter of capsules (µm)	PDI	Maximum (nm)	Median (nm)	Minimum (nm)	Standard deviation (SD)
10-1000	0.27	449	273	997	197

The Polydispersity Index (PDI) measures the uniformity of particles within an encapsulation system. A lower PDI value (close to 0) indicates a more uniform size distribution, which is ideal for the consistent and predictable release of encapsulated materials. Typically, a PDI value below 0.3 is optimal, ensuring reliable and controlled performance in applications such as drug delivery or functional textiles. Conversely, a higher PDI suggests variability in particle sizes, which can lead to uneven release patterns.^29,30

Microstructure microcapsule-applied fabric and raw fabric

The presence of microcapsules in the linen fabric was confirmed using SEM as shown in Figure 5(b) and (c). The longitudinal section shows the layers and globules of microcapsules in the microcapsule-coated fabric.

Figure 5.

SEM images: (a) Raw fabric, (b) & (c) microcapsule-applied fabrics.

Elemental analysis of microcapsule-applied fabrics

The EDS results confirmed the presence of elements in the tested sample. The presence of selenium confirms the presence of chitosan and gum Arabic.³¹ Potassium, carbon, and oxygen are also associated with gum Arabic.³² Carbon and oxygen conformed to the presence of EOs because of the presence of terpene compounds. Terpenes combined two thousand 5-carbon-base (C5) units (isoprene units) and also presented oxygen-containing function groups such as ketone, hydroxyl, aldehyde, and ether³³ (Figure 6 and Table 5).

Figure 6.

EDX spectrum of microcapsule-applied fabrics.

Table 5.

Elements identified.

Sl. No.	Element	Weight%	Atomic%
1	C	42.05	57.97
2	O	33.42	34.60
3	Ca	10.57	4.37
4	K	2.19	0.93
5	Se	1.57	0.24
6	Nb	10.62	1.89
	Total	100	100

Evaluation of microcapsule-applied linen fabric

Antibacterial activity

Five samples were tested for Enterococcus and three for Staphylococcus aureus. In addition, all eight samples were tested for gram-negative bacteria (E. coli) to analyse the inhibition zone for the three bacteria. The inhibition of the microcapsule applied linen fabric reached 30 mm against Enterococcus as shown in Figure 7, and all samples showed a slight increase in inhibition compared to the combination of lavender, thyme, and clove oils exhibited an inhibition zone of 23 mm against E. coli.³⁴ Similarly, microencapsulated vetiver oil exhibited inhibition zones of 7.4 mm against S. aureus and 6.5 mm against E. coli.³⁵ Limonene microcapsules demonstrated a consistent inhibition zone of 14.5 mm for both E. coli and S. aureus, whereas vanillin microcapsules showed inhibition zones of 12.5 mm against each of these bacteria.³⁶ Comparatively, the antibacterial inhibition is better than the earlier studies mentioned

Figure 7.

Images of bacterial inhibition zone of linen fabric: (a) & (b) L1, L5, L6, L11, L13, (c) & (d) L12, L6, L7 with control sample.

L1 and L5 microcapsule-applied linen fabrics exhibit excellent antibacterial effects against E. coli compared to S. aureus. In contrast, L6, L7, and L12 samples show superior antibacterial effects against Enterococcus compared to E. coli.

The microencapsulated linen fabric L1 and L5 show an excellent antibacterial effect against E. coli compared to S. aureus as depicted in Figure 8. In contrast, samples L6, L7, and L12 have shown excellent bacterial effects against enterococcus as compared to E. coli. The antibacterial results in samples L8, L11, and L13 demonstrate higher efficiency against S. aureus than E. coli. The strong antibacterial effects observed in all samples were attributed to the presence of eucalyptol globules, cyclohexane, alpha-terpineol, and other phenolic compounds within the microcapsules.²¹

Figure 8.

Bacterial inhibition.

Eucalyptol can attract the cell walls of bacteria by gradually penetrating the membranes. Furthermore, the antibacterial effectiveness of chitosan is enhanced by its cationic characteristics. Membrane leakage can occur when chitosan is attached to the negative charges on bacteria cells. Combining chitosan with EOs contained in microcapsules resulted in potent antibacterial effects against various microorganisms.^7,37 Statistical analysis was performed to determine the antibacterial activity of the finished textile. The results showed that the antibacterial efficacy of E. coli is significantly higher than (p < .05) the other two strains irrespective of the fabric samples tested. ANOVA results also show the antibacterial effectiveness of various fabric samples (L1, L5, L6, L7, L8, L11 and L13) found insignificant (p > .05) with a given bacterial type.

Mosquito repellence test

The mosquito repellence of the microcapsule-applied linen fabric shows significant improvement before and after washing (90%), the results are comparatively better than the lavender (30%), eucalyptus-rosemary (37%) and citronella (33.8) microcapsules that are reported earlier.^38–40 The efficiency of the mosquito repellent was assessed using equation (1), based on data acquired from the excito chamber. The test was carried out for one microcapsule-applied sample (L7) which had a significant antibacterial effect. This is observed in Figure 9, the mosquitos flew away from the microcapsule-applied fabric samples and stayed on raw samples because of the following active compounds in the Eos: α-pinene, cineole, eugenol, limonene, terpinolene, citronellol, citronellal, and camphor. Generally, mosquito antennae are sensitive to temperature and moisture, and repellent molecules interact with the olfactory receptors of female mosquitoes impairing their sense of smell and hindering their ability to recognize hosts.^41,42 The efficiency of the mosquito repellency is calculated based on the data acquired from the excito chamber using equation (1). To assess the durability of the fabric material with microencapsulation, the test is performed before and after five five washes using the AATCC-61 washing method as shown in Table 6. The efficiency of mosquito repellence is calculated by the following formula, $M o s q u i t o r e p e l l e n c y % = \frac{N o . o f s p e c i m e n e s c a p e d + N o . o f s p e c i m e n d e a d}{N o . o f s p e c i f m e n e x p o s e d} * 100$ (1)

Figure 9.

Excito chamber.

Table 6.

Mosquito repellence of microcapsule-applied linen fabric.

Sl. No.	Samples	Time delay	Number of mosquitoes were released into the chamber	Number of mosquitoes on treated fabric	Number of mosquitoes on control fabric	Repellency %
12	Microcapsule-applied linen fabric (before washing)Microcapsule-applied linen fabric linen fabric (after 5 washing)	At the initial stage	10	01	09	90%
		After 30 minutes	10	01	09	90%
		At the initial stage	10	02	08	80%
		After 30 minutes	10	01	09	90%

Antioxidant efficiency

The linen fabric samples were treated with a methanol solution containing approximately 0.15 mM DPPH. Then the samples were incubated at 37°C in a dark room for 30 minutes. UV absorbance at 517 nm was recorded through a UV-visible spectrophotometer. The scavenging activity was determined using equation (2). $D P P H s c a v e n g i n g a c t i v i t y % = \frac{A b s o r b a n c e o f c o n t r o l s a m p l e - A b s o r b a n c e o f s a m p l e}{A b s o r b a n c e o f c o n t r o l s a m p l e} * 100$ (2)

Lower absorbance of solution is an indication of higher DPPH scavenging activity. An increase in antioxidant activity depended on the reduction in DPPH absorption.^27,5

The microcapsule-applied samples L1, L5, L6, and L7 had comparatively higher scavenging activity (range lies in 60% to 80%) than the samples L8, L11, L12, and L13 (range lies in 40% to 60%) as depicted in Figure 10. The scavenging activities of L1, L5, L6 and L7 achieved better performance but were slightly lower than the performance of microcapsules from thyme oil (96%).⁴³

Figure 10.

Antioxidant activity of microcapsule-applied linen fabrics with control sample.

The result of all samples is that sample L1 has a higher antioxidant effect and L13 has a comparatively lower antioxidant effect. The change in scavenging activity was due to the presence of flavonols, hydroxybenzoic acids, and hydrolysable tannins in eucalyptus; carotenoids of aloe vera; related compounds for aloe vera; linalool acetate, linalool and 1,8-cineole of lavender.^34–37 A comparison of functional tests of all the microencapsulated samples is shown in Table 7.

Table 7.

Functional properties of linen fabric.

Sl. No.	Sample	Antibacterial E.coli (mm)	Antioxidant (%)	Mosquito repellency (%)
Sl. No.	Sample	Antibacterial E.coli (mm)	Antioxidant (%)	Before wash	After Wash
1	Linen 1	23	80	-	-
2	Linen 5	20.07	76	-	-
3	Linen 6	23.8	72	-	-
4	Linen 7	30	68	90%	90%
5	Linen 8	23	59	-	-
6	Linen 11	23.1	49	-	-
7	Linen 12	27.8	40	-	-
8	Linen 13	20.8	37	-	-
9	Control sample	0.2	2	10%	10%

This table provides a summary of the results from the three functional testing methods applied to the fabrics.

Thermal analysis

Mass loss with respect to temperature was observed using TGA as shown in Figure 11. The thermograph revealed that there was a very minimum deviation in mass loss across the samples. The mass loss of sample L1 was comparatively high at the final degradation temperature of 383°C, whereas the mass loss of sample L13 was comparatively low at a final degradation temperature of 366°C. The deviation between the L13 and control samples was approximately 11%. The mass loss of the remaining samples was almost equal to the final degradation temperature as shown in Table 8. The thermal stability of the Microcapsule-applied linen fabric has a minor effect on the temperature. These results are in line with those of a previous study.⁴⁴

Figure 11.

Thermal behaviour of microcapsule-applied linen fabric.

Table 8.

TGA analysis.

Sl. No	Sample	T_onset	T_max	T_offset	Mass loss (%)
1	Control sample	233	348.14	388.44	96
2	L1	258.54	288.05	383.85	92.57
3	L5	249	330.39	363.06	88.07
4	L6	239	342.71	389.22	89.30
5	L7	237.79	365.10	434.94	87.74
6	L8	281.58	345.79	381.80	88.18
7	L11	260.23	352.16	393.44	89.23
8	L12	250.38	337.67	373.50	89.73
9	L13	257.39	339.57	366.86	86.36

where, major degradation temperature (Tmax), final degradation temperature (Tf), and initial degradation temperature (Ti).

FTIR analysis

The FTIR spectra showed the presence of functional groups in the raw and microcapsule-applied linen fabrics as shown in Figure 12. It is observed that the C = O stretching occurs among all the microcapsule-applied samples in the peak range of 1730 cm⁻¹ to 1745 cm⁻¹. This is evidence for the presence of chitosan. The peak at 1633 cm⁻¹ confirmed the presence of the amide-I group of chitosan through the occurrence of a Schiff base. The bands 2922 cm⁻¹ and 3328 cm⁻¹ indicate the stretching vibration of the O-H and N-H bonds of the microcapsule-applied samples. Such peaks may be caused by interactions between molecules of chitosan and EOs without the formation of covalent bonds, such as electrostatic interactions, hydrogen bonds, and hydrophobic forces. The peak at 1519 cm⁻¹ confirmed the presence of chitosan in amide-II (N-H bending) groups. The peak appears in the range of 1036 cm⁻¹ to 1151 cm⁻¹ confirming the presence of gum Arabic and chitosan through C-O bonds. The peak with a wide stretch that appears at 749 cm⁻¹ is evidence of aromatic C-H bonding, and indicates the presence of EOs.^45,21

Figure 12.

FTIR spectrum of the Microcapsule-applied linen fabrics and raw linen Fabric.

Release of EOs

The Higuchi model provides a framework for understanding how active compounds are released from a uniform matrix when subjected to diffusion. Initially developed to address the dissolution behaviour of lipophilic, planar matrices, the model defines a mathematical relationship governing the release kinetics of the dispersed substance.⁴⁶

Therefore, the kinetic release behaviour of microcapsules in the linen fabric was analysed using employing the Higuchi model in which the test data acquired from the UV/Vis spectrophotometer were interpreted.

The test samples were prepared using two sq. cm piece of treated fabric which was placed in a beaker containing 20 mL of deionized water with 1 mL of ethanol at a constant temperature of 37°C ± 0.50°C for 6 hours, taking measurements were taken at equal time intervals. The amount of active principle released into the bath was determined using UV/Vis spectrophotometer at different times.

To understand and follow the release of drugs from fabric material different models have been adopted. Investigations have revealed that drug release follows first-order kinetics (Eq. (3)). The relevant data are compiled in Table 10 and the plots are shown in Figure 13. Furthermore, the Higuchi model (Eq. (4)) which employs Fickian diffusion was adopted to evaluate the diffusion coefficients and the relevant data are given in Table 10. The diffusion coefficient was calculated from the slope of the respective plots in Figure 14.

Figure 13.

First-order kinetics for the drug released.

Figure 14.

Higuchi plot: Plot of % drug released versus the square root of time.

Thus, the release behavior of the microcapsule-applied linen material is slow and consistent. This makes them particularly suitable for hospital bedsheets and pillow covers. For example, when the fabric is washed, it releases a pleasant fragrance that, enhances the surrounding environment. The product remained effective for up to 10 washes. Additionally, can help prevent nosocomial infections, offering added benefits to patients during their hospital stay. $\log C = \log Co - kt$ (3) $Q = A D {((2 C - Cs) Cst)}^{1 / 2}$ (4)

The data in Table 9 revealed that the observed burst phase in the ethanol-water system was very high in the case of L7 and L11 and the lowest one was observed for L6 (38.0 %), while the diffusion coefficient in Table 10 revealed that the value decreased with time. In the case of L11 the diffusion coefficient was very low (∼10⁻³).

Table 9.

Parameters as evaluated from the first-order rate equation.

	L1	L5	L6	L7	L8	L11	L12	L13
logC₀	1.68	1.81	1.58	2.06	1.78	2.24	1.89	1.65
	47.9	64.6	38.0	-	60.3	-	77.6	44.7
k	0.55	0.32	0.11	0.32	0.16	0.76	0.09	0.08

Table 10.

Diffusion coefficients as evaluated by Higuchi’s model.

Time (min)	L1	L5	L6	L7	L8	L11	L12	L13
60	0.4057	0.4128	0.3806	0.4410	0.4090	8.97e-3	0.4485	0.3807
120	0.3944	0.3943	0.3773	0.4298	0.4000	7.65e-3	0.3919	0.3775
180	0.3730	0.3750	0.3636	0.3597	0.3728	6.58e-3	0.3836	0.3637
240	0.3632	0.3552	0.3572	0.3071	0.3586	6.38e-3	0.3435	0.3573
300	0.3417	0.3361	0.3013	0.2739	0.3401	5.88e-3	0.3377	0.3013

Conclusion

➢ The microcapsules were created using a combination of EOs, as described in the abstract. This innovative method involved selecting specific species of eucalyptus, aloe vera, and lavender, which are rich in compounds that inhibit bacterial growth (Refer to the abstract for details). A total of 15 different types of microcapsules were produced, using gum Arabic and chitosan as the membrane shell to encapsulate the EOs.

➢ Eight different microcapsules were randomly selected and applied to 100% woven linen fabric using the dip method with grafting. The shell and core compounds of the microcapsules were verified using SEM, OM, a particle size analyser, and an oil release test. The presence of microcapsules was confirmed by FTIR peaks.

➢ The particle size distribution indicated that the microcapsules ranged from 100 to 1000 nm, with only a small percentage exceeding this range. The spherical morphology of the microcapsules was confirmed using an optical microscope.

➢ The bacterial inhibition of all fabric samples was significant and was confirmed through bacterial tests. Fabric sample L7 inhibited very high for Enterococcus (gram-positive) bacteria because of the concentration (6 mL) of aloe vera, lavender and eucalyptus. Fabric L13 was inhibited very high for s. aureus (gram-positive) bacteria because of the high concentration (3 mL) of all EOs.

➢ Fabric L1 sample inhibited very high for Escherichia Coli (gram-negative) bacteria owing to the concentration (4 mL) of all EOs.

➢ Similarly, the antioxidant activities of the L1 and L7 samples were significantly enhanced, ranging between 70% and 80%. This improvement was attributed to the higher free radical scavenging activity resulting from the concentration of the oil blend.

➢ The thermal stabilities of all the fabric samples were consistent and exhibited minimal deviation from the control samples.

➢ The release of EOs from the Microcapsule-applied fabrics was high in the L7 and L11 samples, according to Higuchi’s model diffusion coefficient.

➢ The mosquito repellence of the treated fabric samples was 90% that of the untreated samples.

➢ Based on the test results, this study demonstrates the potential to develop a multifunctional material with antibacterial properties, mosquito repellence and scavenging activity, which is crucial for any medical textile product, particularly bed sheets, pillow covers and scrubs in hospitals.

Future scope

Future scope could involve applying this finish to all home furnishing products in hospitals, protecting against both mosquito bites and bacterial growth. This product has the potential for broader applications beyond home furnishings, such as incorporating finishes into nursing uniforms. Not only would this protect against bacteria and mosquitoes, would also impart a pleasant, natural fragrance to the fabric.

Investigating the creation of wound-healing textiles by incorporating advanced functional microcapsules offers a highly promising avenue of research. Transitioning from microencapsulation to nanoencapsulation of active compounds could serve as a valuable area of exploration, potentially reducing the likelihood of capsule rupture during textile applications and enhancing the overall durability and functionality of the product.

Footnotes

Acknowledgments

The authors thank the Vellore Institute of Technology,Chennai,for carrying out this work.

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research,authorship,and/or publication of this article.

Funding

The author(s) received no financial support for the research,authorship,and/or publication of this article.

ORCID iD

Selvakumar Andiappan

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Characterization of various essential oil-loaded microcapsules on linen woven fabric for medical textiles

Abstract

Keywords

Introduction

Materials and methods

Materials

Methods

Capsule preparation and encapsulation

Encapsulation efficiency

Grafting and microcapsule-application of linen fabric

Characterization of the microcapsule-applied linen fabric

Microstructure analysis

Functional properties

Result and discussion

Capsule size distribution and microstructure

Optical microscope

Particle size analyser

Microstructure microcapsule-applied fabric and raw fabric

Elemental analysis of microcapsule-applied fabrics

Evaluation of microcapsule-applied linen fabric

Antibacterial activity

Mosquito repellence test

Antioxidant efficiency

Thermal analysis

FTIR analysis

Release of EOs

Conclusion

Future scope

Footnotes

Acknowledgments

Declaration of conflicting interests

Funding

ORCID iD

References