A study of collagen-hyaluronan interaction through swelling in polyacrylamide gels

The equilibrium swelling of biopolymer loaded polyacrylamide gels can yield information on polymer-polymer interactions. Using the temperature dependence of excess equilibrium swelling, equations were derived to yield homopolymer as well as heteropolymer interactions. Hyaluronan and collagen (Type I) encapsulated in polyacrylamide gels showed increasing isothermal swelling with increase in the bipolymer concentration. The pH dependence of isothermal swelling caused by hyaluronan indicated that the swelling was largely due to repulsion of the charges of the carboxylate groups. Temperature dependent studies showed a decrease in swelling with an increase in temperature for collagen. The opposite trend was found for hyaluronan. This indicates that the interactions among collagen monomers are largely hydrophobic, while the interactions among hyaluronan molecules are mainly hydrogen bonding and repulsive ionic forces. Combined hyaluronan and collagen in polyacrylamide gels demonstrated an increase in swelling with an increase in temperature albeit much reduced compared with hyaluronan alone. Collagen interacts with hyaluronan through ionic attraction.