Design and Synthesis of Water-Soluble Multifunctionalizable Thiol-Reactive Polymeric Supports for Cellular Targeting.

Design and synthesis of novel water-soluble polymers bearing reactive side chains are actively pursued due to their increasing demand in areas such as bioconjugation and drug delivery. This study reports the fabrication of poly(ethylene glycol) methacrylate based thiol-reactive water-soluble polymeric supports that can serve as targeted drug delivery vehicles. Thiol-reactive maleimide units were incorporated into polymers as side chains by use of a furan-protected maleimide containing monomer. Atom transfer radical polymerization (ATRP) was employed to obtain a family of well-defined copolymers with narrow molecular weight distributions. After the polymerization, the maleimide groups were activated to their reactive form, ready for conjugation with thiol-containing molecules. Efficient functionalization of the maleimide moieties was demonstrated by conjugation of a tripeptide glutathione under mild and reagent-free aqueous conditions. Additionally, hydrophobic thiol-containing dye (Bodipy-SH) and a cyclic peptide-based targeting group (cRGDfC) were sequentially appended onto the maleimide bearing polymers to demonstrate their efficient multifunctionalization. The conjugates were utilized for in vitro experiments over both cancerous and healthy breast cell lines. Obtained results demonstrate that the conjugates were nontoxic, and displayed efficient cellular uptake. The presence of the peptide based targeting group had a clear effect on increasing the uptake of the dye-conjugated polymers into cells when compared to the construct devoid of the peptide. Overall, the facile synthesis and highly efficient multifunctionalization of maleimide-containing thiol-reactive copolymers offer a novel and attractive class of polyethylene glycol-based water-soluble supports for drug delivery.

Redox-responsive degradable PEG cryogels as potential cell scaffolds in tissue engineering.

A Michael addition strategy involving the reaction between a maleimide double bond and amine groups is investigated for the synthesis of cryogels at subzero temperature. Low-molecular-weight PEG-based building blocks with amine end groups and disulfide-containing building blocks with maleimide end groups are combined to synthesize redox-responsive PEG cryogels. The cryogels exhibit an interconnected macroporous morphology, a high compressive modulus and gelation yields of around 95%. While the cryogels are stable under physiological conditions, complete dissolution of the cryogels into water-soluble products is obtained in the presence of a reducing agent (glutathione) in the medium. Cell seeding experiments and toxicologic analysis demonstrate their potential as scaffolds in tissue engineering.

'Click' functionalization of cryogels conveniently verified and quantified using high-resolution MAS NMR spectroscopy.

Chemical modification reactions of alkyne containing polyHEMA-based macroporous network structures (cryogels) by Cu(I) catalyzed azide-alkyne 'click' cycloaddition reactions and their monitoring and quantification with high-resolution magic angle spinning (hr-MAS) NMR spectroscopy are reported. Complete conversion is obtained when benzylazide is reacted with the grafted alkyne function, but only partial conversion is observed when using azide-modified poly(ethylene glycol) (PEG-N(3) ). Subsequent addition of benzylazide consumes all remaining alkyne groups. All chemical modifications are easily monitored at each stage using hr-MAS NMR spectroscopy. The alkyne functionality and the resulting triazole ring provide well resolved (1) H resonances to monitor and quantify the progress of such 'click' reactions in general.