We report the design and synthesis of a tetraethylene glycol- (TEG-) based bidentate ligand functionalized with dihydrolipoic acid (DHLA) and biotin (DHLA-TEG-biotin) to promote biocompatibility of luminescent quantum dots (QD's). This new ligand readily binds to CdSe-ZnS core-shell QDs via surface ligand exchange. QDs capped with a mixture of DHLA and DHLA-TEG-biotin or polyethylene glycol- (PEG-) (molecular weight average approximately 600) modified DHLA (DHLA-PEG600) and DHLA-TEG-biotin are easily dispersed in aqueous buffer solutions. In particular, homogeneous buffer solutions of QDs capped with a mixture of DHLA-PEG600 and DHLA-TEG-biotin that are stable over broad pH range have been prepared. QDs coated with mixtures of DHLA/DHLA-TEG-biotin and with DHLA-PEG600/DHLA-TEG-biotin were tested in surface binding assays and the results indicate that biotin groups on the QD surface interact specifically with NeutrAvidin-functionalized microtiter well plates.