Tuning Barrier Properties of Biological Hydrogels.

A major function of biological hydrogels (biogels) is to serve as barriers against invading pathogens and foreign materials. This review focuses on methods to tune the steric and adhesive barrier properties of biogels at the nanoscale. Altering the biogel mesh spacings that lead to changes in steric obstruction allows for gross exclusion of larger particles but does not provide selectivity with molecular specificity. Enabling direct binding of specific entities to the biogel microstructure introduces specificity yet has very limited breadth, unable to block numerous diverse entities. In contrast, third party modulators that interact with the biogel matrix to enable cross-linking of specific entities to the biogel mesh, or facilitate agglutination of these entities, can robustly tune the barrier properties of biogels against multiple species with molecular specificity without direct chemical modification of the biogel or changes to its microstructure. We review here the design requirements for developing effective third party modulators. The ability to selectively enhance the barrier properties of biogels has important implications for numerous applications including prevention of infection and contraception.