Orthopyridyl Disulfide (OPSS) PEG

Orthopyridyl disulfide (OPSS) PEG is a polyethylene glycol derivative with an orthopyridyl disulfide functional group. Its structure consists of a polyethylene glycol backbone and an orthopyridyl disulfide functional group, which has the biocompatibility and water solubility of PEG, as well as the metal-liganding ability and surface modification of the OPSS functional group. The orthopyridyl disulfide can selectively bind to free thiols or sulfhydryl groups to form oxidatively and reductively reversible disulfide bonds.

OPSS-PEG-SVA as linker for the preparation of AuNC-PEG-MSHFig. 1. OPSS-PEG-SVA as linker for the preparation of AuNC-PEG-MSH (Molecular Imaging. 2018, 17: 1536012118775827).

Examples of OPSS PEG Derivatives


OPSS-PEG-NHS has an OPSS and an NHS ester at each end of the molecular chain and is a linear heterofunctional PEG reagent. It is a useful crosslinking reagent with a PEG spacer group. OPSS stands for o-pyridyl disulfide, which can react with thiols and sulfhydryl groups to form S-S bonds. Through the pyridyl disulfide functional group, OPSS-PEG-NHS can selectively react with sulfhydryl groups to form stable disulfide bonds while releasing the thiol pyridyl group.


OPSS-PEG-FITC are thiol (-SH) group reactive and fluorescent PEG derivatives that can be used to modify biomolecules or other materials via their available thiol groups. The o-pyridyl disulfide reacts with the thiol group to form a stable disulfide bond while releasing the thiol pyridine group. At the same time, fluorescein produces an intense green fluorescent signal that is easy to detect.


OPSS-PEG-SVA is a linear bifunctional modified PEG containing o-pyridyl disulfide on one end and a bifunctional polyethylene glycol and valeryl succinimide on the other. The N-hydroxysuccinimide (NHS) reactive ester is able to form physiologically stable amide bonds with the amine group of lysine under mild reaction conditions. The o-pyridyl disulfides selectively react with thiols or mercaptans to form redox reversible disulfide bonds.


OPSS-PEG-SCM is a linear heterobifunctional PEG reagent that can selectively react with sulfhydryl groups to form stable disulfide bonds while releasing sulfhydrpyridinyl groups. SCM is an NHS ester, commonly known as succinimidyl carboxymethyl ester, which is highly reactive with primary amines and forms stable amide bonds.

Sulfiding Reagents for OPSS-PEG Synthesis

Carbon disulfide (CS2): Carbon disulfide can react with appropriate orthopyridyl groups to form orthopyridyl disulfide compounds. CS2 is commonly used as a solvent and sulfur source in the reaction.

Disulfide diphenyl (PhSSPh): Disulfide diphenyl can be reacted with the appropriate orthopyridyl group to form the target compound.

Dioctyl Sulfide (DSS): DSS is a deprotection reagent that can be used to remove protective groups in OPSS-PEG synthesis. In the reaction, DSS can react with the sulfur atoms on the protecting groups to remove them while generating orthopyridyl disulfide functional groups.

Applications of OPSS-PEG in Drug Delivery

  • Targeted Drug Delivery. OPSS PEG enables selective targeting of specific cells or tissues by introducing targeting ligands into the PEG chain.
  • Enhanced Drug Stability. OPSS PEG can be used as a protective agent for drugs by reacting with specific functional groups in the drug molecule to form stable ether or thioether bonds.
  • Controlled Release Drug Delivery Systems. OPSS PEG can be combined with controlled release materials to form controlled release drug delivery systems.

BOC Sciences has strong manufacturing capabilities for OPSS PEG and related products. We offer a variety of OPSS PEG derivatives with different PEG chain lengths and linkage groups to meet specific customer needs.


  1. Zhao, Y. et al. Melanocortin 1 receptor targeted imaging of melanoma with gold nanocages and positron emission tomography. Molecular Imaging. 2018, 17: 1536012118775827.

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