Development of Cellulose-Chitosan Silver Nanocomposites Films for Wound Dressing Applications

Abstract

Modern wound dressings keep the wound hydrated but they lack antimicrobial properties hence they cannot prevent infections. In this study, wound dressings were made from tempo oxidized cellulose chitosan nanocomposite embedded with silver nanoparticles (AgNPs). Cellulose was isolated from rice husks (Oryza sativa) followed by oxidation of its hydroxyl groups to carboxylic and carbonyl groups resulting in oxidized cellulose nanofibrils. Dispersion of the nanofibrils in silver nitrate-chitosan solution resulted in synthesis of AgNPs in the composite films obtained after solvent casting. The cellulose fibers had mean fiber lengths and diameters of between 23-45 µm and 8.55±7.35 µm as determined by MorFi analyzer. The IR spectra of cellulose had peaks at 3329, 2900, 1684 and 1070 cm-1 associated with OH, CH2, bound water and C-O-C functional groups respectively. Introduction of C=O at C2-C3 was confirmed by presence of a carbonyl peak at 1720 cm-1 and a single amorphous peak in the X-ray diffractogram. For the case of tempo oxidized cellulose, an IR peak at 1720 cm-1 was attributed to C=O groups of COOH group at C6. Morphology of the samples changed upon oxidation to highly porous surface as observed in the SEM micrographs. These treatments also resulted in changes in thermal stability, the degree of crystallinity and fiber lengths. Crosslinking of oxidized cellulose with chitosan was confirmed by the disappearance of the C=O Infra-red vibrational frequency at 1720 cm-1 and the absence of cellulose peaks normally observed at 2θ of 16, 22 and 33⁰ in the X-ray diffractograms. Presence of AgNPs in the films was confirmed by the sharp, distinct peaks in the X-ray diffractograms at 2θ = 28, 32, 38, 45, 55, and 59⁰ and spherical particles with diameters between 100 - 800 nm in the SEM micrographs. The release of AgNPs from the composite films was confirmed from the gradual increase of its plasmon resonance peak at 412 nm in a first order kinetics with the rate of release being 25 ppm/h. The tensile strength, swelling capacity, transmittance and biodegradability of the films were found to be dependent on the TOCNF, glycerin and AgNPs content of the films. The microbial inhibition of the composite film against E. coli, B. subtilis, C. albicans, S. aureus, P. mirabilis, P. aeruginosa was found to be 12±1, 10.7±0.6, 11±1, 12.7±0.6, 12.7±0.6, 10.3±0.6 mm attributed to release of AgNPs. As for the control, the inhibitions were found to be 13±1, 7.3±1, 23.3±0.6, 0, 24.7±0.5, 10±0.6 and 0 mm for E. coli, B. subtilis, C. albicans, S. aureus, P. mirabilis, P. aeruginosa, respectively. In-vivo studies revealed that the dressing could accelerate wound healing through release of AgNPs that inhibited the growth of microorganism. In conclusion, the developed nanocomposite films could be used as wound dressings to prevent the growth of microorganisms.