The characterization and plasma protein compatibility of high density and highly crosslinked hydrogels
Description
Poly (hydroxylalkyl methacrylate) hydrogels are used for a variety of applications in the biomedical field. Certain physical properties and surface characteristics of these hydrogels have been identified as necessary for good compatibility with biological fluids. However, increased use of these hydrogels has been hampered by their lack of strength under shearing forces. But, crosslinking, which is used in other types of polymers to induce strength, has been linked to an increase in adverse biological response, such as plasma-protein binding. The objective of this thesis was to synthesize poly (hydroxylalkyl methacrylate) hydrogels with a range of crosslink densities and hydrophilicities and to determine if these parameters effect plasma protein binding Highly crosslinked, (1,3,5 and 7 percent volume by weight), high molecular weight optical hydrogels of poly (hydroxylalkyl methacrylate) and poly (dihydroxypropyl methacrylate) were polymized using a 2-methoxethane/water solvent system. After polymerization was completed, the solvent system in the gel was slowly and sequentially replaced until a pure water hydration system was reached. This method of polymerization and hydration was necessary to produce high density gels that have not been previously synthesized After equilibration in water, each of 87 hydrogel types was completely characterized by measurement of its equilibrium water content, surface polar work of adhesion (I$\sb{\rm sw}$), tensile strength, percent elongation and effective network density. Additionally, plasma-protein binding studies were performed using six hydrogel types, representing a range of surface properties of the gels synthesized The results of this study indicate that increasing the crosslinking in hydrogels does not increase their physical and mechanical properties. Nor does an increase in hydroxyl ratio within a hydrogel necessarily increase the gel's surface hydrophilicity or decrease its plasma protein binding. Generally, the plasma-protein binding increased as the crosslink density of the gels did. Moreover, the lower-contact-angle gels in each monomer series bound the least amount of protein. The plasma-protein elution experiments show that no single gel characteristic can prevent protein adsorption onto a gel. Rather, it is the interrelation between several of the characteristics that determines the least adsorbing gel. The key factors appear to be surface hydrophilicity, pore size and crosslink density of the gel