In-Seon Park

Thiolated Salmonella antibody immobilization onto the gold surface of piezoelectric quartz crystal

An improved antibody-coated sensor system based on quartz crystal microbalance analysis on Salmonella spp. was developed making use of thiolated antibody immobilization onto one gold electrode of the piezoelectric quartz crystal surface. The best results in sensitivity and stability were obtained with the thin layer of a thiol-cleavable, heterobifunctional cross-linker, sulfosuccinimidyl 6-[3-(2-pyridyldithio)propionamido]hexanoate (sulfo-LC-SPDP). The long bridge of this reagent could function as a spacer, facilitating antibody-Salmonella interaction on the gold electrode. After the addition of a S. typhimurium suspension into a reaction cell with 0.1 M sodium phosphate buffer, pH 7.2, the resonant frequency decreased conspicuously. The time required for maximum frequency shift was about 30-90 min. Sensor response was observed for the microbial suspensions ranging from 9.9 x 10(5) to 1.8 x 10(8) CFU/ml.

Operational characteristics of an antibody-immobilized QCM system detecting Salmonella spp.

A quartz crystal microbalance (QCM) system detecting Salmonella spp. was developed by an anti-Salmonella antibody immobilization onto one gold surface of a piezoelectric quartz crystal surface with sulfosuccinimidyl 6-[3-(2-pyridyldithio)propionamido]hexanoate (sulfo-LC-SPDP) thiolation. The optimum temperature and pH for the antibody-immobilized sensor were 35 degrees C and 7.2, respectively. The frequency shifts obtained were correlated with the Salmonella concentrations in the range 3.2 x 10(6)-4.8 x 10(8) CFU per ml. The system was quite specific to Salmonella spp. and applicable for repetitive use after a regeneration step employing 1.2 M NaOH. A model sample measurement was done for a market milk spiked with Salmonella typhimurium.

Application of a flow-type antibody sensor to the detection of Escherichia coli in various foods

A flow-type biosensor system which uses a broad-spectrum anti-Escherichia coli antibody and quartz crystal microbalance as biological component and transducer was developed. Biosensor responses were initiated by injecting viable E. coli suspensions through a flow cell and the sensor system was optimized for response time according to flow rate and injection time, followed by the measurement of responses for various E. coli strains. As expected, the sensor system showed a characteristic broad binding feature against E. coli strains. A linear sensor response in double-logarithmic scale was observed for the microbial suspensions ranging from 1.7 x 10(5) to 8.7 x 10(7) CFU/ml. Sample measurements could be done within 20-30 min after Stomacher treatment followed by spiking or enrichment.