Theophylline-functionalized silver nanoparticles: A multifaceted approach to controlled drug release

Silver nanoparticles (AgNPs) have garnered significant attention in drug delivery research due to their unique physicochemical properties and biocompatibility. In this study, theophylline-loaded silver nanoparticles were synthesized via chemical reduction of silver nitrate using trisodium citrate, polyvinylpyrrolidone (PVP), and theophylline (TP) as stabilizing and capping agents. The resulting nanoparticles were extensively characterized to evaluate their structural, morphological, and release properties. Nuclear Magnetic Resonance (NMR) and Fourier Transform Infrared Spectroscopy–Attenuated Total Reflectance (FTIR-ATR) confirmed successful surface interaction and ligand binding, as evidenced by signal suppression and characteristic functional group shifts. Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) analyses revealed particle morphologies ranging from irregular granular to well-defined spherical structures, with the AGTH F5 (AGTH represents for Silver nanoparticles comprising theophylline) formulation exhibiting the most uniform morphology and minimal agglomeration. Zeta potential measurements ranging from +25.3 mV to +27.8 mV indicated moderate colloidal stability. Ultraviolet–visible (UV–Vis) spectroscopy confirmed nanoparticle formation through characteristic plasmonic absorption peaks. In vitro drug release studies demonstrated a sustained release profile of theophylline, best described by the Higuchi kinetic model (R 2 > 0.98), indicative of diffusion-controlled (Fickian) release with a release exponent (n) of 0.331. Among the tested formulations, AGTH F5 showed the most favorable balance of particle size, stability, and controlled drug release, highlighting its potential as a promising nanocarrier for sustained therapeutic delivery.