Bioderived Lipoic Acid-Based Dynamic Covalent Nanonetworks of Poly(disulfide)s: Enhanced Encapsulation Stability and Cancer Cell-Selective Delivery of Drugs

Dynamic covalent poly(disulfide)-based cross-linked nanoaggregates, termed nanonetworks (NNs), endowed with pH- and redox-responsive degradation features have been fabricated for stable noncovalent encapsulation and triggered cargo release in a controlled fashion. A bioderived lipoic acid-based Gemini surfactant-like amphiphilic molecule was synthesized for the preparation of nanoaggregates. It self-assembles by a entropy-driven self-assembly process in aqueous milieu. To further stabilize the self-assembled nanostructure, the core was cross-linked by ring-opening disulfide exchange polymerization (RODEP) of 1,2-dithiolane rings situated inside the core of the nanoaggregates. The cross-linked nanoaggregates, i.e., nanonetwork, are found to be stable in the presence of blood serum, and also, they maintain the self-assembled structure even below the critical aggregation concentration (CAC) as probed by dynamic light scattering (DLS) experiments. The nanonetwork showed almost 50% reduction in guest leakage compared to that of the nanoaggregates as shown by the release profile in the absence of stimuli, suggesting high encapsulation stability as evidenced by the fluorescence resonance energy transfer (FRET) experiment. The decross-linking of the nanonetwork occurs in response to redox and pH stimuli due to disulfide reduction and β-thioester hydrolysis, respectively, thus empowering disassembly-mediated controlled cargo release up to ∼87% for 55 h of incubation. The biological evaluation of the doxorubicin (DOX)-loaded nanonetwork revealed environment-specific surface charge modulation-mediated cancer cell-selective cellular uptake and cytotoxicity. The benign nature of the nanonetwork toward normal cells makes the system very promising in targeted drug delivery applications. Thus, the ease of synthesis, nanonetwork fabrication reproducibility, robust stability, triggered drug release in a controlled fashion, and cell-selective cytotoxicity behavior, we believe, will make the system a potential candidate in the development of robust materials for chemotherapeutic applications.