Alkylsuccinylated Bentonite-GelMA Hybrid Hydrogels for Enhanced Mechanics and Osteogenic Drug Delivery

Bentonite is an attractive inorganic material for biomedical applications owing to its biocompatibility and large surface area. Here, we report a straightforward yet effective alkylsuccinylation strategy to tailor the bentonite surface with hydrophobic functionalities. Successful organic modification was confirmed by Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA). The alkylsuccinylated bentonite was incorporated into gelatin methacryloyl (GelMA)-based hydrogels to construct inorganic-organic hybrid systems. In particular, GelMA hydrogels containing octadecylsuccinylated bentonite (O-bent) exhibited 1.3-, 1.7-, and 2.8-fold increases in storage modulus (G') compared to pristine GelMA hydrogels, as measured by rheometry. The GelMA/O-bent composite hydrogels showed no detectable cytotoxicity at O-bent contents of 0.1%. In addition, the hydrophobically modified bentonite exhibited sustained release behavior for hydrophobic molecules, indicating its potential as a drug reservoir. Moreover, the GelMA/O-bent composites effectively adsorbed the hydrophobic osteogenic agent phenamil through a simple adsorption-washing process, achieving a loading efficiency of 65%. Phenamil-loaded GelMA/O-bent hydrogels further demonstrated enhanced osteogenic activity in vitro, with a 1.8-fold increase in alkaline phosphatase (ALP) activity in MC3T3-E1 preosteoblasts compared to drug-free hydrogels. Overall, this work establishes alkylsuccinylation as a straightforward surface modification strategy to prepare bentonite derivatives that interact with polymer chains in hydrogel networks, thereby forming organic-inorganic hybrid hydrogels with improved mechanical properties and serving as reservoirs for hydrophobic drugs in biomedical and tissue engineering applications.