Monitoring
and early warning of spores germination is of great
significance in avoiding their potential pathogenicity. Thus, effective
monitoring of markers during spore germination is of great value.
A ratio-dependent fluorescent probe based on in situ incorporation
of fluorophores in a metal–organic framework (MOF) was designed
to monitor a main component of bacterial spores, 2,6-pyridinedicarboxylic
acid (DPA), with high sensitivity and specificity. The fluorescence
of CdS quantum dots loaded on zeolitic imidazolate framework-8 (ZIF-8)
nanocrystals is initially quenched by europium ions. The europium
ions, however, can be seized by DPA, leading to restoring the fluorescence
of quantum dots. Simultaneously, the fluorescence of another dye molecule,
rhodamine 6G, loaded on the ZIF-8 is not affected by DPA and can serve
as a stable internal fluorescence reference signal. On this basis,
a ratio-dependent fluorescence method for rapid detection of DPA was
established. The linear calibration ranged from 0.1 to 150 μM
with a detection limit of 67 nM, which is much lower than the amount
of DPA (60 μM) released by the contagious number of spores needed
to cause anthrax. This analysis platform exhibits good anti-interference
ability for monitoring spore germination. The practicable application
of the method was verified by monitoring and imaging the release of
DPA in the course of spore germination.
We have developed a new DNA self-assembly amplification technology that generates electric current for electrochemical biosensing. The new technology was used for detection of human epidermal growth factor receptor 2 (HER2). In our technology, an aptamer was utilized both as a ligand for recognition and as a signal generating reporter. The aptasensor is based on a sandwich format and a DNA primer on a HER2 aptamer initiates auxiliary DNA self-assembled on the electrode to form a long one-dimensional DNA. The resulting DNA is then reacted with molybdate to generate electrochemical current. The sensitivity of the aptasensor with DNA self-assembly was greater than that of the aptasensor without DNA self-assembly due to the extended length of the DNA strand. Aptasensor analysis of HER2 in serum of breast cancer patients and healthy individuals is highly correlated (R = 0.9924) with ELISA measurements, with a p value of 1.37 × 10. The analysis of HER2 in serum (confirmed by ELISA) suggests that HER2 levels in breast cancer patients are much higher than healthy individuals. For HER2 positive patients, the levels are higher than those of HER2 negative patients. After surgery, there is a drop of HER2 levels in serum, suggesting potential clinical applications of the new self-assembled DNA electric current generating biosensor. Unlike proteins, DNA is easily amplifiable. The DNA signal amplification method presented here enables effective current generation, which can find wide range of biomedical applications for protein detection.
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