Synthetic Methods of Disulfide Bonds Applied in Drug Delivery Systems

Disulfide bond plays an important role in various fields, for example, biochemical processes, industrial and pharmaceutical chemistry, bioconjugates, peptidomimetics and selfassembled monolayers (SAMs) etc. In the past decades, drug delivery systems (DDS) have been widely investigated, and disulfide-based oxidation-reduction responsive DDS is the most promising one. Disulfide bonds have no physiological toxicity and remain stable in human body, and can be broken into a reduced form of glutathione (GSH) via the thiol-disulfide exchange reaction. Moreover, the GSH level in tumor tissues has been known to be at least 4-fold higher than that in normal tissues. Therefore, this specific redox potential in cells stimulates people to design oxidation-reduction responsive DDS for specifically releasing drugs in tumor cells and develop the new methods for the preparation of organic disulfanes. The present review has attempted to comprehensively summarize recent advances on the synthetic methods of disulfide bond in drug delivery systems.