Nano-silver-modified PQC/DNA biosensor for detecting E. coli in environmental water

• Published in: Biosensors & bioelectronics 2009, Vol.24 (5), p.1405-1410
• Main Authors: Sun, H., Choy, T.S., Zhu, D.R., Yam, W.C., Fung, Y.S.
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Biosensing Techniques - instrumentation; Biosensing Techniques - methods; Biosensor; Biosensors; Biotechnology; DNA, Bacterial - isolation & purification; E. coli; Environmental Monitoring - instrumentation; Equipment Design; Equipment Failure Analysis; Escherichia coli; Escherichia coli - genetics; Escherichia coli - isolation & purification; Fundamental and applied biological sciences. Psychology; Methods. Procedures. Technologies; Micro-Electrical-Mechanical Systems - instrumentation; Oligonucleotide Array Sequence Analysis - instrumentation; PCR; Piezoelectric quartz crystal; Reproducibility of Results; Sensitivity and Specificity; TiO 2; Various methods and equipments; Water Microbiology; Water Pollutants - analysis
• ISSN: 0956-5663; 1873-4235
• DOI: 10.1016/j.bios.2008.08.008

To meet the requirement of World Health Organization for zero tolerance of E. coli cell in 100 mL drinking water, a new procedure based on photodeposition of nano-Ag at TiO 2-coated piezoelectric quartz crystal (PQC) electrode was developed to fabricate a highly sensitive PQC/DNA biosensor. Enhancement of 3.3 times for binding of complementary DNA has been shown and attributed to the following effects arising from the nano-Ag coating. First, a large increase in the active surface area and packing density of neutravidin enhances the maximum neutravidin load to 1.8 times of a normal electrode. Second, the functional activity of neutravidin is enhanced by chemical interaction with nano-Ag to give rise to an increase in the binding ratio between neutravidin and biotinylated DNA probe from 1.00:1.76 to 1.00:3.01. Third, the stronger binding leads to a higher stability of the biotinylated DNA probes bound and increase in hybridization with the complementary DNA. Under the optimized conditions for flow analysis with online PCR product denaturing and hybridization, a detection limit of eight E. coli cells are obtained which require sampling at least 800 mL water to detect a single E. coli cell in 100 mL water.