Comparative analysis of stability and biological activities of violacein and starch capped silver nanoparticles

Violacein is a bacterial quorum-sensing chromophore, also referred to as ‘purple treasure' for its versatile utility in the pharmaceutical, food, cosmetic and textile industries. Moreover, it provides broad spectrum biological activity that is the subject of expansive scientific research. The major limitation in the drug delivery of violacein is its hydrophobic nature that results in poor bioavailability. Nanoparticles (NPs) coupled with these drugs tend to enhance their delivery, efficacy and safety profiles. In this study, we established that violacein capped silver NPs (vAgNPs) have shown enhanced stability with 3 to 10 times higher therapeutic effect against multidrug resistant bacteria, fungi and algae compared to starch capped silver NPs (cAgNPs). The surface plasmon resonance, size, shape, crystalline nature and capping agent of these NPs were studied with UV-Vis spectroscopy, Scanning Transmission Electron Microscopy, Atomic Force Microscopy, X-ray Diffraction and Fourier Transform Infrared Spectroscopy, respectively. This comparative study examines the efficacy of vAgNPs against cAgNPs and establishes that surface capping of AgNPs with violacein yields conjugative benefits, i.e., strengthening each other's therapeutic effect, increased bioavailability of violacein, higher stability and maneuvering the therapeutic effect of vAgNPs towards Gram positive bacteria.