| Electrochemical biosensor technology has attracted more and more attention of researchers in the field of biomedicine, environmental monitoring, food and pharmaceutical applications for its unique advantages, such as high sensitivity, simple equipment, inexpensive, fast response, and so forth. How to take advantage of the electrochemical biosensor technology to realize the fast and sensitive detection of disease markers and heavy metal ions in the environment is one of the popular research topics of current medical and environmental science. This paper combines the signal amplification technology to develop a series of new electrochemical biosensors to detect metal ions, nucleic acids and proteins with high sensitivity. The specific content of the study are as follows:Part1Dual signal amplification for highly sensitive electrochemical detection of uropathogens via enzyme-based catalytic target recyclingWe report an ultrasensitive electrochemical approach for the detection of uropathogen sequence-specific DNA target. The sensing strategy involves a dual signal amplification process, which combines the signal enhancement by the enzymatic target recycling technique with the sensitivity improvement by the quantum dot (QD) layer-by-layer (LBL) assembled labels. The enzyme-based catalytic target DNA recycling process results in the use of each target DNA sequence for multiple times and leads to direct amplification of the analytical signal. Moreover, the LBL assembled QD labels can further enhance the sensitivity of the sensing system. The coupling of these two effective signal amplification strategies thus leads to low femtomolar (5fmol/L) detection of the target DNA sequences. The proposed strategy also shows excellent discrimination between the target DNA and the single-base mismatch sequences. The advantageous intrinsic sequence-independent property of exonuclease III over other sequence-dependent enzymes makes our new dual signal amplification system a general sensing platform for monitoring ultralow level of various types of target DNA sequences. Part2Personal glucose sensor for point-of-care early cancer diagnosisThe commercially available personal glucose sensor (PGS) has been the most successful point-of-care (POC) sensor up to date. However, the PGS only responds to glucose rather than other species. Extending the use of the PGS for monitoring different types of targets would potentially revolutionize the applicability of the PGS. Early POC diagnosis of cancer is demonstrated by using multi-invertase conjugated microsphere labels and a PGS sensor transducer. The invertase, which catalyzes the hydrolysis of sucrose to glucose, enables the PGS to detect target analytes beyond glucose, and the numerous invertase labels involved in each antibody-antigen binding event lead to significantly amplified PGS readings for sensitive protein detection.Part3Sensitive detection of copper(II) by a personal glucose sensor usingclick chemistryHere we report a new sensing strategy for sensitive and selective detection of Cu2+based on multi-invertase conjugated magnetic bead signal amplification labels and a PGS transducer. The Cu2+is in situ reduced to Cu+by sodium ascorbate, which catalyzes the click linking between the alkynyl-DNA immobilized on a disposable screen printed carbon electrode and the azido-DNA attached to the invertase/magnetic bead conjugates. The numerous invertase on the magnetic bead labels through Cu+-catalyzed click chemistry reaction convert sucrose to glucose, which is monitored by the PGS and offers amplified digital readings for Cu2+detection. By employing the multi-invertase signal amplification, as low as10nmol/L Cu2+can be detected. Our method also shows high selectivity for Cu2+against other metal ions owing to the highly specific Cu+-catalyzed click chemistry reaction, and is applicable for monitoring Cu2+in real river samples. Our strategy can be easily expanded for the monitoring of a wide range of targets when coupled with various recognition events. |
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