Development of Copper Nanoparticle Conjugated Chitosan Microparticle as a Stable Source of 2nm Copper Nanoparticle Effective against Methicillin- resistant .

Background: Copper nanoparticle (CuNP) has well-established antimicrobial activity. Instability in an aqueous medium due to aggregation into larger particles, conversion into metal ions, and oxidation into metal oxides are the major limitations of its practical use against bacterial infections.

Objective: Development of CuNP Conjugated Chitosan Microparticles as a reservoir that will release CuNP effective against notorious bacteria like Methicillin-resistant Staphylococcus aureus.

Methods: CuNP conjugated chitosan microparticles (CNCCM) were synthesized using a simple twostep process. In the first step, a solution of chitosan in 2% (w/v) ascorbic acid was added dropwise in copper sulphate solution to prepare Cu ion conjugated chitosan beads. In the second step, these beads were soaked in sodium hydroxide solution to get the CNCCM. The dried CNCCM were characterized thoroughly for surface conjugation of CuNP, and the release of CuNP in a suitable medium. The physicochemical properties of release CuNP were further verified with the in silico modelled CuNP. The Antimicrobial and antibiofilm activities of released CuNp were evaluated against methicillin-resistant Staphylococcus aureus (MRSA).

Results: 2% (w/v) ascorbic acid solution (pH 3.5) was the optimum medium for the release of ~2 nm CuNP from CNCCM. The CuNP had an optical band gap of ~ 2 eV. It inhibited the cell wall synthesis of MRSA. The minimum inhibitory concentration was 200 nM. At 100 nM dose, the CuNP caused ~73% reduction in biofilm development after 24 h of growth. The cytotoxic effect of CuNP on the human cell line (HEK 293) was significantly less than that on MRSA. The 48 h IC value against HEK 293 was 3.45-fold higher than the MIC value against MRSA after 24 h treatment.

Conclusion: CuNP Conjugated Chitosan Microparticle has been developed. It works as a stable reservoir of ~2 nm CuNP. The CuNP is released in an aqueous medium containing 2% (w/v) ascorbic acid (pH 3.5). The released CuNP has a bacteriostatic effect against MRSA at a concentration safe for human cells.