An effective modified method to prepare highly luminescent, highly stable water-soluble quantum dots and its preliminary application in immunoassay

In this paper, a biocompatible poly(γ-glutamic acid) (PGA)-based polymer with numerous thiol groups grafted onto the backbone was self-synthesized. It has been successfully used to prepare water-soluble quantum dots (QDs) with high luminescence and high stability. FTIR spectroscopy, transmission electron microscopy, dynamic light scattering, spectrofluoro-photometry, fluorescence microscopy and flow cytometer were used to characterize QDs@poly(γ-glutamic acid)-grafted cysteamine (PGA-g-MEA). The results indicated that QDs@PGA-g-MEA with an identical small size were highly luminescent with a well maintained, even increased, photoluminescence (PL) intensity when compared with the tributylphosphine oxide (TOPO) coated QDs. Meanwhile, they were highly stable in aqueous solution under a wide range of pH from 2 to 12, as well as under different temperatures. The QDs@PGA-g-MEA were then applied as fluorescent probes to detect human IgGs and the results demonstrated that QDs@PGA-g-MEA had great potential for application in immunofluorescence.