Antimicrobial activity of a silver-microfibrillated cellulose biocomposite against susceptible and resistant bacteria

Antibiotic Microbial Resistance (AMR) is a major global challenge as it constitutes a severe threat to global public health if not addressed. To fight against AMR bacteria, new antimicrobial agents are continually needed, and their efficacy must be tested. Historically, many transition metals have been employed, but their cytotoxicity is an issue and hence must be reduced, typically by combination with organic polymers. Cellulose of natural origin, especially those derived from unavoidable residues in the food supply chain, appears to be a good capping agent for the green synthesis of silver nanoparticles. Herein, we describe a green synthesis method to produce a novel biocomposite, using ascorbic acid as reducing agent and microfibrillated cellulose as a capping agent and demonstrate this material to be an efficient antimicrobial agent. Silver nanoparticles were obtained in the cellulose matrix with an average size of 140 nm and with antimicrobial activity against both sensitive and resistant Gram positive (using 1500 ppm) as well as sensitive and resistant Gram negative (using 125 ppm) bacteria. Also, an inverted disk-diffusion methodology was applied to overcome the low-solubility of cellulose compounds. This novel silver nanoparticle-cellulose biocomposite synthesized by a green methodology shows the potential to be applied in the future development of biomedical instruments and therapeutics.