Temperature-sensitive microcapsules with variable optical signatures based on incorporation of quantum dots into a highly biocompatible hydrogel

Biocompatible fluorescent microcapsules were constructed by incorporating CdSe quantum dots into an ionotropic hydrogel. The hydrogel formulation used has been shown to be highly resistant to chelators present in biological media, and the resulting composite shows no leakage of entrained quantum dots over test periods of up to 4 months. The optical signature of the microcapsules is controlled by incorporating mixtures of quantum dots having different sizes into the composite, such that microcapsule composites exhibit Forster resonance energy transfer (average estimated Forster radius of 77 angstrom). The resulting microcapsules also display so-called smart behavior, as the optical signature displays a linear dependence on temperature over the 20-45 degrees C range of interest to biological experiments.