Biohydrogels (BioHGs): Sources, Physicochemical Properties, Applications, Current Challenges - A Review

Since 1894, hydrogels (HGs) have advanced from simple water-swollen colloids to poly (2-hydroxyethyl methacrylate) (pHEMA)-based biomedical materials introduced in 1960. Further, the journey continued towards innovative, stimuli-responsive hybrid systems in 2025. Once limited to wound dressings and contact lenses, HGs have now formed a multi-billion-dollar market. Biohydrogels (BioHGs) are biomaterials with remarkable physicochemical properties, enabling their widespread applications. However, several challenges also restrict their translational potential, including poor mechanical robustness, limited long-term stability, variability in natural polymer sources, and difficulties in large-scale production. Although numerous reviews have summarized BioHGs and their applications, a clear understanding of how biomaterial properties relate to HG functionality and performance remains underexplored. This review article collates esteemed, interesting, and up-to-date information on sources, properties, applications, and challenges of BioHGs. Superlative BioHGs can be produced by precisely optimizing formulation and processing parameters (polymer concentration, pH, temperature, and mechanical strength) to ensure desirable features. It was found that biomaterials spanning an extensive molecular-weight range have been utilized for HGs fabrication, enabling the tailoring of physicochemical and biological properties for specific applications. It is pertinent to note that synthetic HGs demonstrate the highest mechanical strength, natural HGs excel in swelling behaviour and porosity. In contrast, hybrid HGs achieve the most favourable overall performance by effectively balancing all anticipated properties. Briefly, further information on future research directions toward sustainable, high-performance biomaterials has been provided. We highlight recent advances focused on the development of hybrid and composite BioHGs, the incorporation of bioactive agents, and the engineering of multifunctional systems to address these limitations. The integration of novel components, such as biosurfactants (BSs), chitosan, protein-based polymers, and nanoparticles, into nanocomposites offers new opportunities for designing advanced HGs with enhanced performance.