-Poly-L-lysine conjugated gold nanorod probe to monitor antimicrobial activity and mechanism of action by surface-enhanced Raman spectroscopy

Antimicrobial peptides have been demonstrated to display an immediate response to a large set of pathogenic activity against viruses, bacteria, and fungi by virtue of their local binding with phospholipid phosphatidylserines to exert cytotoxic effect. Plasmonic nanostructures are particularly appealing in medical diagnostics and therapeutics owing to their biocompatibility and ease of surface modification. The current article reports a development of epsilon-poly-L-lysine modified gold nanorod (PLL-AuNR) Raman-active system that can be used to target pathogenic bacteria along with rapid monitoring of antimicrobial action from environmental samples. Result indicates a remarkable change in Raman enhancement factor from 1.49 x 10(4) to 2.17 x 10(7) after addition of Salmonella, Bacillus subtilis, and Escherichia coli bacteria in PLL-AuNR colloid, enabling a large optical window to monitor the process of pathogenic action. Antimicrobial assay with PLL-AuNR reveals significantly high cytotoxic values of similar to 92% in E. coli, similar to 90% in B. subtilis, and similar to 87% in Salmonella compared with their respective responses in bare PLL, which shows similar to 37% in E. coli, similar to 32% in B. subtilis, and similar to 27% in Salmonella, which proportionally collaborates with change in surface-enhanced Raman spectroscopy (SERS) intensity beyond 10 min of incubation time. Major experimental design parameters and possible mechanism that relates unusual plasmonic enhancement and antimicrobial action of PLL-AuNR system have also been discussed.