Serum albumin–protamine conjugate for biocompatible platform for targeted delivery of therapeutic macromolecules

摘要

A well‐defined, one‐to‐one conjugate between human serum albumin (HSA) and protamine was synthesized and characterized as a biocompatible carrier for macromolecules. In circulation, the conjugate will camouflage drug molecules upon complex formation, while liberating free drug at the desired location using a triggering mechanism. The N‐terminus of protamine was thiolated and conjugated with the unpaired Cysteine‐34 of HSA, and was purified by ion‐exchange chromatography. The molecular weight of the conjugate was 70.8 kDa, confirming one‐to‐one conjugation between HSA (66.6 KDa) and protamine (4200 Da). Superimposed fluorescence spectra of native HSA and HSA–protamine conjugate indicated no conformational change around the Trp‐214. The conjugate had marked reduction in hemolytic and cytotoxic properties compared to protamine. When therapeutic potential was tested using tissue plasminogen activator as a model drug, HSA–protamine conjugate suppressed the enzymatic activity by 65%, which was fully recovered by a triggering agent, heparin. The construct showed binding characteristics with activated platelets upon conjugation with a targeting peptide, demonstrating flexibility to introduce suitable homing moiety on the surface. The camouflaged construct retained triggered release property in human plasma condition. Overall, the conjugate has a good potential to serve as a biocompatible platform for macromolecular drugs. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 102A: 2481–2490, 2014.