Designing Biodegradable Dextran Hydrogels: A Breakthrough in Polymer Science

The development of biodegradable hydrogels has become a significant focus in polymer science, particularly for applications in biomedicine. A novel class of polymerizable dextrans designed with hydrolyzable groups has emerged as a promising solution. This innovative approach involves the careful grafting of L-lactide onto hydroxyethyl methacrylate (HEMA), leading to the synthesis of HEMA-lactate, which can then be coupled with dextran to form dex-lactateHEMA.

The process begins with the activation of HEMA-lactate using N,N'-carbonyldiimidazole (CDI), allowing for the production of a compound known as HEMA-lactate-CI. This compound is subsequently linked to dextran, showcasing a unique strategy to enhance the properties of dextran-based hydrogels. Importantly, the degree of substitution (DS) can be meticulously controlled by adjusting the molar ratio of HEMA-CI or HEMA-lactate-CI to dextran, achieving an incorporation efficiency of 60-80%.

The swelling behavior of these hydrogels reveals critical insights into their degradation under physiological conditions. When immersed in an aqueous buffer at 37 °C, different hydrogel formulations demonstrate distinct swelling characteristics. For instance, the dex-MA hydrogel reaches equilibrium swelling within three days, indicating no significant hydrolysis of ester groups. In contrast, dex-HEMA and dex-lactateHEMA hydrogels exhibit progressive swelling followed by a dissolution phase, attributed to the hydrolysis of ester linkages.

Degradation times for these hydrogels are influenced by both cross-link density and initial water content. As the DS increases, the network's cross-link density rises, necessitating more time for hydrolysis to occur, thereby prolonging degradation. Interestingly, a lower initial water content also correlates with longer degradation times, highlighting the intricate balance between network structure and hydrolysis rates.

To further refine the properties of these hydrogels, researchers have explored the use of macromers with fixed amounts of hydroxy acid groups. By employing preparative high-performance liquid chromatography (HPLC), specific compounds like 2-(methacryloyloxy)ethyl-lactate can be synthesized and coupled to dextran, creating new hydrogel variants. These hydrogels demonstrate varying degradation profiles based on their chemical composition, with the presence of more hydrolytically sensitive groups resulting in shorter degradation times.

The ongoing research in biodegradable dextran hydrogels not only enhances our understanding of polymer design but also paves the way for future applications in drug delivery systems and tissue engineering. As scientists continue to unravel the complexities of these materials, the potential for innovative solutions in the biomedical field expands significantly.