Reduction-sensitive spacers

Reduction-sensitive spacers. Shen and Ryser coupled methotrexate via a disulphide-containing spacer with poly(D-lysine). " The conjugate was able to enter methotrexate-resistant cell lines cultured in vitro. There was evidence for a reductive cleavage of tlje spacer in the cytosol compartment. This example indicates another possibility for achieving intracellular release of drugs from polymeric conjugates by proper selection of the spacer. 

Surface modifications of polymers is brought about by the introduction of alcohol functionality, e.g., poly(tetrafluoroethylene-co-hexafluoropropylene) on reduction with sodium naphthalide in THF results in an unsaturated modified surface layer, the thickness of which is controlled with reaction time and temperature. The air sensitive surface contains alcohols, ketones, aliphatic C-H bonds in addition to C=C and C C. The more alcoholic groups are introduced by hydroboration-oxidation, but the esterification leads to the formation of ester in lower yield. This reveals that the reactivity of OH group is similar to hindered alcohols. The reactivity of the surface can be enhanced by chain extension of secondary surface alcohols with ethylene oxide to form a surface containing primary alcohols groups separated from the polymer backbone by C-2 spacer. On the other hand, primary alcohols are directly introduced to the surface by reaction of the reduced layer with 9-BBN, followed by carbonylation and reduction [5]. 

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