TEMPERATURE-RESPONSIVE BIOCONJUGATES .1. SYNTHESIS OF TEMPERATURE-RESPONSIVE OLIGOMERS WITH REACTIVE END GROUPS AND THEIR COUPLING TO BIOMOLECULES

Using 3-mercaptopropionic acid (MPA) as a chain-transfer agent, the radical oligomerization of N-isopropylacrylamie (IPAAm) was carried out with varying molar ratios of MPA to IPAAm in DMF. The molecular weight of oligo-IPAAm (OIPAAm) could be controlled by the ratio of MPA to IPAAm. The OIPAAm was confirmed to average one carboxyl end group per chain. All OIPAAms samples were highly water-soluble at lower temperatures and exhibited phase separation near 32-degrees-C. The optical transmittance of the OIPAAms aqueous solutions changed drastically at 32-degrees-C which was independent of OIPAAms molecular weight. In aqueous solutions of OIPAAm having concentrations higher than 1 wt % and molecular weight of 6100, the oligomers were precipitated and recovered in 85 wt % yield of their original content. Further, OIPAAm was grafted to atelo collagen by activated ester-amine coupling. The OIPAAm-collagen conjugates were able to dissolved in cold water and precipitated at 34-degrees-C. Temperature-responsive OIPAAm-collagen conjugates are expected to maintain native collagen funtionality in the solution state, react at lower temperatures, and be easily removed from the system with small temperature increases.