NSP offers heterobifunctional Folate-PEG-Thiol (Folate-PEG-SH, Folic acid-PEG-Thiol) with high quality. Folic acid, or vitamin B9, can selectively bind to folate receptor, while thiol can react with thiol (SH) can be used to react with maleimide or thiol group. The PEG moiety in the heterofunctional PEG derivatives provides water solubility, biocompatibility, and flexibility. This reaction allows attachment of folic acid ligand to proteins, antibodies, peptides or particle surfaces. Folic acid functionalized substrates have been used for targeted drug delivery, imaging, and bioassay development.