Immobilization of quantum dots in multiple responsive microgels for biomedical applications

A novel type of smart hybrid materials based on the in situ immobilization of quantum dots (QDs) on a responsive microgel template was prepared and investigated. Firstly, a temperature and pH dual responsive hybrid microgel was developed through the in-situ immobilization of CdS QDs in the interior of a copolymer microgel of poly(Nisopropylacrylamide- acrylamide-acrylic acid) [p(NIPAM-AAm-AA)]. The amino groups of the pAAm segments in the microgels are designed to sequester the precursor Cd2+ ions for in situ formation of CdS QDs in the interior of the microgels and stabilize the CdS QDs embedded in the microgels. We demonstrated that the carboxyl groups on the p(NIPAM-AAm-AA)-CdS hybrid microgels can be used for further coupling with 3-aminophenyl boronic acid for optical glucose sensing. The glucose concentration change can induce a reversible swelling/shrinkage of the hybrid microgels, which can further modify the physicochemical environment of the QDs immobilized inside the microgels, resulting in a reversible quenching/antiquenching in photoluminescence (PL). The method is extendable to other QDs with different emission wavelengths and other targeting ligands, thus it is possible to develop multifunctional hybrid micro-/nano-gels for additional important biomedical applications.