Calcium biosensing with a sol-gel immobilized photoprotein

Aequorin, the bioluminescent protein found in the jellyfish Aequorea sp., has been immobilized in a porous sol-gel glass environment. The luminescence from this protein is specifically triggered by the presence of calcium ions, thus offering exciting possibilities for the development of an optical biosensor for this cationic species. The luminescence emission spectrum has been measured from the aequorin protein after interaction with calcium ions. The intensity of the luminescence, measured at the peak maximum of 470 nm, for the encapsulated protein has been calibrated against calcium ion concentration. The characterization of the protein within the sol-gel matrix has been reported together with biosensing experiments using human sera and milk samples. The results suggest that the sol-gel encapsulated aequorin protein offers potential as a one shot bioluminescence based biosensor for the determination of calcium ions in such complex matrices.