Antibacterial toxicity of mesoporous silica nanoparticles with functional decoration of specific organic moieties

Mesoporous silica nanoparticles (MSNs) are generally considered as biocompatible nanocarriers for biomedical applications; however, no study has provided conclusive evidence regarding the antimicrobial toxicity of MSNs. Here, we systematically evaluated the toxicity of MSNs against Escherichia coli (E. coli) by investigating not only the removal rate of cetyltrimethyl ammonium bromide (CTAB) from the MSNs, but also functional decorations of specific organic moieties such as polydopamine (PDA) and graphene oxide (GO). The mortality of E coli was strongly dependent on the residual CTAB that was not completely removed from the MSNs by acid etching process. On the other hand, for the removal of CTAB from the MSNs the reduced etching time and increased H2O content in the etchant increased the survival of E. coli, probably because of the reduction of bioactive H+ ions that inhibit bacterial growth. Notably, PDA-coated and GO-wrapped MSNs demonstrated the higher toxicity than the pristine MSNs, because of the strong interplay of antibacterial activity of functional decoration (PDA and GO). This study provides a useful guideline for the design of biocompatible MSNs for biomedical applications.