In Situ Synthesised Silver Nanoparticle- Infused L-Lysine-Based Injectable Hydrogel: Development of a Biocompatible, Antibacterial, Soft Nanocomposite

The synthesis of L-lysine-based amphiphilic hydrogelator consisting of a naphthalene moiety at the Ntermini and an ethyleneoxy unit with free primary amine at the Cterminus is reported. The amphiphile showed good gelation ability with minimum gelation concentration 0.6%w/v in binary mixtures of dimethyl sulfoxide/phosphate buffer (1:4v/v, pH7.4). The hydrogel was characterised by spectroscopic and microscopic studies to delineate the role of non-covalent interactions in self-assembly gelation. Subsequently, Ag nanoparticles were synthesised within the hydrogel by insitu photo-reduction of AgNO3 under sunlight, in which the gelators act as reducing/stabilising agents. The nanocomposites were characterised by transmission electron microscopy, UV/Vis and X-ray diffraction spectroscopy and thermogravimetric analysis. Rheology of the soft nanocomposite showed significant mechanical strength and thixotropic self-recovery properties, which made the composite suitable for use as a syringe-injectable hydrogel. These soft nanocomposites exhibited excellent antibacterial activity against both Gram-positive and Gram-negative bacteria. They showed low haemolytic activity and high biocompatibility to mammalian (Chinese hamster ovarian) cells. In addition, agar-gelatin film infused with these nanocomposites allowed normal growth of mammalian cells on its surface while being lethal towards bacteria.