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. Author manuscript; available in PMC: 2010 Sep 30.
Published in final edited form as: Adv Drug Deliv Rev. 2009 Jul 20;61(11):940–952. doi: 10.1016/j.addr.2009.07.002

Figure 4.

Figure 4

Strategy for redox-mediated peptide targeting. These approaches target the intratumoral ratio of GSH to GSSG. The disulphide bond confers redox sensitivity peptide carriers. (A) The extracellular concentration of GSH is very low but cleavage of disulfide bonds can be facilitated by the presence of membrane protein disulfide isomerase (PDI) which can lead to extracellular release of drug [142]. (B) The disulfide bond is cleaved by intracellular reductive activity after cellular uptake. A limitation of this approach is the stability of the disulfide linkage during circulation in the bloodstream [143].