A strategy of combining physical embedding and covalent crosslinking was developed to encapsulate cysteamine-capped quantum dots (QDs) into agarose hydrogel microbeads (AHM). Cysteamine-capped QDs were encapsulated into the pores of agarose hydrogel microbeads by virtue of hydrogen bonding between the amino groups of cysteamine and hydroxyl groups of agarose, resulting in more than 6.0 × 107 QDs per microbead. Polyethylenimine (PEI) and oxalaldehyde were then introduced to form a covalently crosslinked network to further stabilize the encapsulation. The resulting hybrid hydrogel microbeads exhibited high doping capacity and negligible QDs leakage, and enabled optical multicolor barcoding.
