Thiol functionalized nanoparticles may be used in mucoadhesive drug delivery, synthesis of dithiol terminated amphiphilic diblock copolymer, Bidentate dithiol-poly(ethylene glycol)-poly(d,l-lactide) (SH2-PEG-PDLLA). Gold nanoparticles may be easily functionalized with PEG dithiols by simple ligand exchange.