Quartz crystal microbalance sensor targeting low molecular weight compounds using oligopeptide binder and peptide-immobilized latex beads Original Research Article

A high-sensitive sensor that uses an oligopeptide and a piezoelectric quartz crystal microbalance (QCM) was developed for detection of low molecular weight compounds under aqueous condition. Porphyrin 5,10,15,20-tetrakis(N-methylpyridinium-4-yl)-21H,23H-porphine (TMpyP) and a porphyrin binding peptide (HASYS) obtained from a phage library were used as the target compound and the target binding material, respectively. A self-assembled monolayer (SAM) of the peptide on the gold electrode surface of quartz crystal (9 MHz, AT-cut) was formed to capture the porphyrin. To achieve ng/ml level detection, we developed a novel sensitization technique using latex beads on which the same porphyrin binding peptide was immobilized. The detection sensitivity of the peptide-immobilized QCM sensor could be improved by addition of the peptide-immobilized latex beads to the detection system. The detection limit was 10 ng/ml of TMpyP. The mass sensitization was achieved by adsorption of the latex beads onto the QCM surface via sandwich binding of porphyrin. This technique would be applicable for any detection system that uses a peptide obtained by combinatorial screening.