Mixed-Charged, but Overall Neutral Hydrogels As Nonfouling, Mechanically Strong Materials

A crucial predicament in the field of biomaterials is the often-undesirable, but immediate coating of implants with nonspecific proteins, which adsorb to the implant upon contact with bodily fluids.  Nonfouling materials are defined as materials to which no proteins adsorb.  Prior research has shown that overall-neutral materials containing a homologous arrangement of mixed-charges exhibit nonfouling properties.  This has been shown for materials formed by either the creation of a hydrogel containing a cross-linked, equimolar mixture of positively and negatively charged monomers, or by use of zwitterionic compounds.  The goal of this research is to develop a greater level of control over mixed-charge hydrogels through the selective choice of the individually charged monomers.  In particular, hydrogels were formed from mixtures of [2-(methacryloyloxy)ethyl]trimethylammonium chloride (TM) and 3-sulfopropylmethacrylatepotassium salt (SA), using a triethyleneglycoldimethacrylate (TEGDMA) crosslinker.  Enzyme Linked Immunosorbant Assay (ELISA) experiments were completed to study the impact of the crosslinker density on the nonfouling characteristics of the hydrogels.  The results have shown promise, indicating that a variety of hydrogels with ultra-low to no quantifiable adsorption of negatively-charged fibrinogen or positively-charged lysozyme were developed.  Swelling characterization and hydration studies were completed to gain insight into mechanical properties of the resulting hydrogels in order to quantitatively study the effects of the concentration of the crosslinker on the mechanical strength of the TM/SA hydrogel.  Ongoing research efforts are focused on tailoring these properties based on the concentration of the TEGDMA crosslinker.  The hydrogels being investigated in this work will be an important component of future research efforts to develop functionalizable hydrogel implant materials.