Non-penetrant nitric oxide-loaded graphene oxide-mesoporous silica nanosandwich composite for antibacterial application

Abstract

Development of novel antimicrobial agents is a crucial step towards tackling antibiotic resistance in bacteria. In this work, a novel nitric oxide-releasing sandwich-type nanocomposite for antimicrobial application (GOSINO) was synthesized and characterized. The nanocomposites were synthesized by conjugating thiol-modified mesoporous silica onto graphene oxide nanosheets through an innovative surfactant-mediated co-condensation sol–gel process. The obtained nanocomposite carried a large surface area (674 m^2/g), high aspect ratio, open pore structure with uniform pore size (about 3 nm), high density of thiol groups for subsequent nitric oxide (NO) loading, and stable dispersion in water. Highest NO loading achieved for GOSINO was 0.40 μmol/mg, subsequently exhibiting high antibacterial efficacy against Staphylococcus aureus, Escherichia coli and multi-drug resistant Escherichia coli (minimum inhibitory concentration: 250 μg/ml at which 50% of bacterial growth was inhibited), with an equivalent effective NO concentration of 12-18 μM. The antibacterial activity stems from the formation of bacterial-material aggregates with the help of the platelet-like shape of the nanocomposite, followed by the release of high concentration of NO in the proximity. The nanocomposite was proven to be non-toxic to human keratinocytes and human dermal fibroblasts below 250 μg/ml through an in-vitro cytotoxicity assay.