Polymer Hydrogels: Unique Material for Bioseparations, Biosensing and Drug Delivery

Polymer Hydrogels: Unique Material for Bioseparations, Biosensing and Drug Delivery

Abstract

Hydrogels are hydrophilic polymers that can swell in the presence of water, absorbing many times their weight of water while still retaining the solid state. They are extremely versatile materials that have found a variety of consumer and medical applications, with new ones continuing to emerge. In our research group we are modifying these materials and developing new uses for them. Of particular interest are environmentally sensitive hydrogels which are a class of gels with swelling triggered by an external parameter, such as temperature or pH, which provides further applications for these materials. One potential application is in microfluidic devices to achieve small scale separations and for the sensing biological and organic compounds, by combining the properties of affinity gels with those of environmentally sensitive hydrogels. Unfortunately, these hydrogels easily lose their environmentally sensitive phase transformation properties when modified which makes this a significant challenge. In this presentation we report on two separate efforts to overcome this problem by combining thermally sensitive hydrogels made from N-isopropyl acrylamide (NIPAAm) and metal affinity chromatographic media. In both cases we attempted to retain the original phase transformation behavior of the hydrogels by carefully maintaining their hydrophilic/hydrophobic balance. In the first approach the NIPAAm monomers were first copolymerized with acrylamide (AAm) monomers. The AAm groups in the resulting hydrogels were then functionalized with metal affinity groups. In the second approach the co-monomer was molecularly designed and synthesized with the affinity groups attached to them. The hydrogel was then synthesized through copolymerization with NIPAAm. While the former approach did produce affinity hydrogels, they lacked a sharp phase transition and had non-uniform distributions of affinity groups. The latter approach produced hydrogels that retained sharp phase transitions with highly uniform distribution of affinity groups. This clearly demonstrates that it is possible to produce hybrid affinity hydrogels without loss of critical properties through careful design and synthesis.