Hydrogels are hydrophilic, crosslinked polymers that swell in water but cannot dissolve because of their network structure. They are fascinating materials with a wide variety of applications; everyday examples include gelatin and soft contact lenses. Hydrogels are key components of consumer products like diapers, biochemical separation techniques, pharmaceutical delivery systems and medical devices such as artificial organs. The utility of hydrogels lies in their ability to absorb large amounts of water and to influence the mass transfer of solutes.

This research involves the theoretical and experimental study of the thermodynamics, sorption and desorption kinetics, solute permeability and mechanical properties of various gels with important scientific and industrial uses. Novel gels with unique properties and applications are also synthesized and characterized; for example, gels that expand and contract with small changes in temperature and gels that can absorb solvent almost instantly have been developed in our lab. Applications of gels in pharmacy and biotechnology receive particular emphasis. Drug delivery applications are described below; gel-based techniques for protein purification examined include chromatography, gel electrophoresis, and aqueous two-phase extraction. Our research goals are to understand and improve these techniques as well as to develop novel techniques for protein isolation and purification using hydrogels.

Controlled Drug Delivery

As the patents on many established drugs expire and the costs of developing new drugs mount, pharmaceutical companies are taking a more careful look at how available drugs can be used more effectively. Most drugs work only within a rather narrow range of concentration; often, the goal of controlled drug delivery is to release a drug at a carefully controlled rate over an extended period of time (sustained release) to maintain a constant blood level. In other cases, the drug must be delivered to a specific site in the body to be effective (targeted delivery). The traditional training of chemical engineers in transport phenomena, reaction kinetics, and applied mathematics is ideal preparation for solving these nontraditional problems. Both fundamentals of mass transfer in drug delivery systems and the development of novel drug delivery devices and techniques are being investigated. Drug delivery systems based on hydrogels are emphasized. Recently, the use of hydrogel-coated catheters for the delivery of drugs directly to diseased tissues has been examined in detail, primarily in connection with balloon angioplasty catheters.

Protein-Based Biomaterials

Since the human body is composed primarily of proteins, proteins have special potential for use as bioresponsive and/or biodegradable drug delivery systems. They can also be used as cell encapsulating matrices for tissue engineering. An approach to making novel biomaterials with tremendous potential for the future is the genetically directed synthesis of new amino acid polymers or "artificial proteins." The concept is to use genetic engineering techniques to "program" cells to produce artificial proteins of a specified design. First, molecular modeling software and protein design heuristics are used to design an amino acid sequence of the desired function. Then genetic engineering techniques are used to create E. coli bacteria that will produce the artificial protein according to the design. Next, these engineered cells are grown in a fermentor; the artificial protein is then extracted from the fermentation broth. Once purified, the artificial protein is studied to understand structure-function relationships in protein-based biomaterials. These novel materials are also being examined for potential practical utility in tissue engineering, bioseparations, and pharmacy. Current research is focused on crosslinked gels made from artificial proteins based on elastin and on silk structures, and also on synthetic poly(amino acids) like poly(L-lysine). Projects on novel uses of plant proteins are under development.