Lithocholic based stimuli-responsive polymer capped silver nanoparticles: Assessment on bio interface driven colloidal stability, antimicrobial activity and ROS-mediated oral cancer therapy.

Stimuli-responsive polymeric micelles (PMs) provide promising plat forms for improving the stability and therapeutic efficacy of metal nanoparticles (MNPs) in biomedical applications. Herein, we report the synthesis of a cysteamine-functionalized poly (N-isopropylacrylamide-co-lithocholic acid) based amphiphilic copolymer, (poly(NIPAM-co-MELCA-Cys)), with thermo- and pH-responsive behavior and its stabilized silver nanoparticles (AgNPs). The copolymer exhibits primary and secondary critical aggregation concentration (CAC) at 3.84 x10-4 and 1.51x10-3 wt%, respectively, in aqueous media, together with tunable lower critical solution temperature (LCST) behavior. Under optimized alkaline conditions, poly(NIPAM- co- MELCA- Cys) facilitates the formation of spherical AgNPs with nearly uniform distribution and exhibit stability for more than a year. The colloidal stability of capped AgNPs was assessed in physiological media (NaCl, PBS, and FBS) using UV-Visible spectroscopy, DLS, and zeta potential measurements. Optical and morphological properties were analyzed by UV-visible spectroscopy, HR-TEM, DLS, XPS, and zeta potential techniques. MTT assay revealed dose-dependent cytotoxicity in KB cells, while 3T3-L1 cells showed lower sensitivity. ROS generation induced apoptosis, and flow cytometry confirmed G0/G1 arrest with increased apoptosis. These findings highlight the potential of poly(NIPAM-co-MELCA-Cys) for antimicrobial and ROS-mediated oral cancer therapy.