mPEG-SH is widely used in bioconjugation and surface modification due to its ability to introduce a polyethylene glycol (PEG) chain via a thiol-reactive group. The thiol (SH) end selectively binds to gold surfaces, making it ideal for creating PEGylated layers on gold nanoparticles and biosensors, which helps reduce nonspecific binding and improves stability in biological environments. It is also used to modify proteins, peptides, and antibodies by attaching to cysteine residues, enhancing their solubility, reducing immunogenicity, and prolonging circulation time in therapeutic applications. In drug delivery systems, mPEG-SH stabilizes nanocarriers and prevents aggregation. Additionally, it plays a role in developing diagnostic platforms, such as biosensors and microarrays, where controlled surface chemistry is essential for accurate detection.