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 and 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 functionality in the solution state, react at lower temperatures, and be easily removed from the system with small temperature increases.

[1]  M. Heskins,et al.  Solution Properties of Poly(N-isopropylacrylamide) , 1968 .

[2]  A S Hoffman,et al.  Polymer-protein conjugates. II. Affinity precipitation separation of human immunogammaglobulin by a poly(N-isopropylacrylamide)-protein A conjugate. , 1990, Biomaterials.

[3]  H. Kitano,et al.  Gel permeation chromatography using porous glass beads modified with temperature-responsive polymers , 1992 .

[4]  T. Okano,et al.  The influence of hydrophilic and hydrophobic domains on water wettability of 2-hydroxyethyl methacrylate-styrene copolymers , 1978 .

[5]  J. L. Kice.  Inhibition of polymerization. II. Methyl acrylate , 1956 .

[6]  F. Davis,et al.  Alteration of immunological properties of bovine serum albumin by covalent attachment of polyethylene glycol. , 1977, The Journal of biological chemistry.

[7]  Teruo Okano,et al.  Temperature dependence of swelling of crosslinked poly(N,N′-alkyl substituted acrylamides) in water , 1990 .

[8]  R. Yoshida,et al.  Surface-modulated skin layers of thermal responsive hydrogels as on-off switches: I. Drug release. , 1991, Journal of biomaterials science. Polymer edition.

[9]  Teruo Okano,et al.  Thermally on-off switching polymers for drug permeation and release , 1990 .

[10]  G. Johansson,et al.  Functionalization of poly(ethylene glycol) and monomethoxy‐poly(ethylene glycol) , 1981 .

[11]  A. Hoffman,et al.  Polymer-protein conjugates. I. Effect of protein conjugation on the cloud point of poly (N-isopropylacrylamide). , 1990, Biomaterials.

[12]  M. Wilchek,et al.  A spectrophotometric assay for soluble and immobilized N-hydroxysuccinimide esters. , 1982, Analytical biochemistry.

[13]  K. Kubota,et al.  Phase transition of aqueous solutions of poly(N-isopropylacrylamide) and poly(N-isopropylmethacrylamide) , 1989 .

[14]  Cheves Walling,et al.  Copolymerization. VIII. The Relation Between Structure and Reactivity of Monomers in Copolymerization1 , 1948 .