Ascorbic Acid as an Adjuvant to Unbleached Cotton Promotes Antimicrobial Activity in Spunlace Nonwovens

Abstract

The development of affordable, effective, and environmentally friendly barrier fabrics is a current goal in antimicrobial textile development. The discovery of new routes to achieve non-toxic naturally occurring molecules with antimicrobial activity is of interest in the development of materials that promote wound healing, improve hygiene, and offer protection against nosocomial infection. Highly cleaned and sterile unbleached cotton has constituents that produce hydrogen peroxide at levels commensurate with those that favor cell signaling in wound healing. Here, we show the antimicrobial and antiviral properties of spunlaced griege cotton-containing nonwovens treated with ascorbic acid formulations. The mechanism of action occurs through the promotion of enhanced hydrogen peroxide activity. The levels of hydrogen peroxide activity afford antimicrobial activity against Gram-negative and Gram-positive bacteria and antiviral activity against MS2 bacteriophages. Spun-bond nonwoven unbleached cotton was treated with ascorbic acid using traditional pad-dry-cure methods. An assessment of antibacterial and antiviral activity against Staphylococcus aureus, Klebsiella pneumoniae, and MS2 bacteriophages with the AATCC 100 test method showed a 99.99% inhibitory activity. An approach to the covalent attachment of ascorbic to cellulose through citric acid crosslinking chemistry is also discussed. Thus, a simple, low-cost approach to antimicrobial and antiviral cotton-based nonwovens applicable to dressings, nosocomial barrier fabrics, and face masks can be adopted by combining ascorbic acid with spunlace greige cotton nonwoven fabrics.

Keywords: antimicrobial activity; ascorbic acid; cotton.

Figure 1

Comparison of hydrogen peroxide production. Fabrics (50 mg) were incubated overnight in 2 mL of H₂O at room temperature. Aliquots were removed and H₂O₂ content was determined using the ferrous oxidation-xylenol orange assay in quadruplicate, n = 4. Error bars represent Standard Error of Mean (SEM). Results were analyzed by ANOVA. Post-hoc (Tukey) test demonstrated significantly higher levels of H₂O₂ production by TACGauze (TGz) treated with citric acid and ascorbic acid or BIOGauze (BGz) versus either bleached cotton (B8-s2) or TGz alone. * p < 0.001 versus bleached cotton. ‡ p < 0.001 versus TGz.

Figure 2

Effects of the addition of copper and ascorbic acid on hydrogen peroxide production. Fabrics (50 mg) were incubated overnight in 2 mL of H₂O at room temperature. Aliquots were removed and H₂O₂ content was determined using the ferrous oxidation-xylenol orange assay in quadruplicate, n = 4. Error bars represent SEM. Results were analyzed by ANOVA. Post-hoc (Tukey) test demonstrated significantly higher levels of H₂O₂ production by 100% cotton woven fabric (bought commercially) treated with both copper and ascorbic acid (GCS2) (p < 0.001) or by cotton woven fabric treated with ascorbic acid only (GCS1) (p = 0.002) versus untreated bleached 100% cotton nonwoven (B8-s2) fabric.

Figure 3

Comparison of hydrogen peroxide accumulation over a three-day period. Fabrics (50 mg) were incubated in H₂O (2.5% weight/volume) at room temperature for 1, 2, and 3 days. Aliquots were removed and H₂O₂ content determined using the ferrous oxidation-xylenol assay, n = 4. Error bars represent SEM. ANOVA (Tukey) revealed that the levels of H₂O₂ generated by BIOGauze (BGz) were significantly higher on Day 2 compared to the those of the other two fabrics. Even though the peroxide levels generated with BGz declined significantly on Day 3, it was significantly higher than those of either the TGzX1, TACGauze acid-crosslinked treatment or the TGz, TACGauze untreated fabric, whose peroxide levels had fallen to essentially undetectable.

Figure 4

Schematic of the crosslinking reaction of ascorbic acid linked to cellulose. Ascorbic acid ((R)-5-[(S)-1,2,-dihydroxyethyl]-3,4-dihydroxyfuran-2(5H)-one) is reacted with citric acid under conventional pad-dry-cure conditions. The reaction is shown at the 1-hydroxy position of ascorbic acid to form the ester crosslinked analog of cellulose.

Figure 5

Fourier transform infrared spectra (1850–1500 cm⁻¹) of crosslinked bleached 100% cotton nonwoven fabric (B8-s2); black line shows no treatment; others show treatment with 9% citric acid (CA), 5% ascorbic acid (Asc A), and 3% sodium hypophosphite (SHP), and their various control combinations.

Figure 6

Fourier transform infrared spectra (1850–1500 cm⁻¹) of crosslinked TACGauze (TGz); black line shows no treatment; other lines show treatment with 9% citric acid (CA), 5% ascorbic acid (Asc A), and 3% sodium hypophosphite (SHP) with their various control combinations.

Figure 7

Scanning electron microscope(SEM) images of (a,b) TACGauze (TGz) untreated at magnifications of 500× and 1200×, respectively, and (c) BIOGauze (BGz) magnified 5000×.