Abstract—A simple optical chemosensor from phycocyanin (L1), a protein-pigment complex extracted from cyanobacterium Spirulina platensis, has been developed. The L1 shows high selectivity toward Cu2+ by exhibiting spectral shift and quenching of fluorescence intensity. This L1-Cu2+ complex, so called ensemble probe, can be used to detect mercapto biomolecules, and has superior affinity toward homocysteine (Hcy). Upon binding to mercapto biomolecules, the color change from colorless-to-blue and the fluorescence emission change from colorless to pink were observed. This chemosensor could detect Hcy at concentration as low as 4.71 μM (S/N = 3) with a linear range of 10-100 μM (R2 = 0.9903). This sensing approach may have found applications in clinical diagnostics.

Biochemical Engineering and Pilot Plant Research and Development Unit, National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency at King Mongkut’s University of Technology Thonburi, Bangkhuntien, Bangkok 10150, Thailand.