TEMPERATURE-RESPONSIVE BIOCONJUGATES .2. MOLECULAR DESIGN FOR TEMPERATURE-MODULATED BIOSEPARATIONS

We have synthesized carboxyl semitelechelic oligo(N-isopropylacrylamid e) (OIPAAm) using radical telomerization with 3-mercaptopropionic acid . This telomerization is also effective for the synthesis of carboxyl semitelechelic co-oligomers of IPAAm with butyl methacrylate (BMA) as hydrophobic or N,N-dimethylacrylamide (DMAAm) as hydrophilic comonomer s. All co-oligomers are highly water-soluble at lower temperatures and exhibit phase separation with increasing temperature. Pure OIPAAm exh ibits a lower critical solution temperature (LCST) at 32-degrees-C, an d the LCST for co-oligomers can be controlled to increase over 32-degr ees-C with increasing DMAAm composition and to decrease below 32-degre es-C with increasing BMA composition. OIPAAm was grafted to bovine ser um albumin (BSA) and bovine plasma fibrinogen (BPF) by activated ester -amine coupling. These OIPAAm-biomolecule conjugates maintain their te mperature responses, are soluble in cold water, and precipitate over a range of temperatures related to oligomer content. Conjugates could b e selectively precipitated and independently separated from conjugate solution mixtures with increasing temperature. In this case, the numbe r of OIPAAm molecules attached to a conjugate affects the aggregate si zes of precipitated conjugates in mixtures. Both conjugate mixture rat ios and solution concentrations influence the contamination of oligo(I PAAm-co-DMAAm)-BSA conjugates in precipitated oligo(IPAAm-co-BMA)-BPF conjugates. Furthermore, precipitated conjugates separated using centr ifugation and filtration redissolve in water and maintain their biofun ctionality, indicating the potential of strategy in reversible bioreac tors and protein separations.