| Biosensor is a kind of sensor which combines modern biotechnology and advanced physics technology. After the definition of the biosensor was first proposed, it has developed from enzyme sensor to enzyme-free sensor and other else. Combining with modern new immobilization technology and new biomolecule materials, biosensor has increased not only in number but also in the quality and the applications. Because of its easy-going, high-sensitivity, high-selectivity, fast, miniaturized and low-cost, the widely application of biosensors in environmental monitoring, food production, disease tracking, medical examination and others.This thesis comprises four parts, as follows:1. The working principles, types, applications and developments of biosensor were summarized:from glucose oxidase-based biosensors to non-enzymatic glucose sensors. We described the characteristics and applications in biosensors of gold nanoparticles. Formaldehyde and its origins, applications, toxicology were reviewed in detail. The target and content of the dissertation were discussed.2. A simple and environmental-friendly colorimetric method for fast formaldehyde detection was developed. It is based on the improved-acetylacetone (improved-AC AC) method. Colorless solution with glycine and2,4-pentanedione turned to yellow (observed with the naked eyes) when formaldehyde was present. UV-visible spectrophotometry was used to get the absorbance signals. Various experimental parameters affecting formaldehyde detection were optimized. The improved-ACAC method exhibited an excellent linear range (0.3-0.75mg/mL with R2=0.999). It was successfully used to detect formaldehyde in a real sample. In the linear range,1mL the extract of the sample was spiked to a0.45mg/mL formaldehyde standard solution. The increased absorbance was due to the spiked formaldehyde from sample, and the concentration was determined to be1.2mg/kg in the sample.3. According to the preliminary work, a formaldehyde sensor was established. The chromogenic agent was fixed on a kind of acrylic resin. The sensor was placed in formaldehyde of different concentrations, and the time when the sensor changed its color was recorded. At the same time, the concentration of the formaldehyde was displayed by a portable gas analyzer. The final detection limit was6ppb. Compared to conventional formaldehyde detection technology, the sensor is simple, the results were reliable, so it is very suitable for the detection of gaseous formaldehyde.4. Developing non-invasive, sensitive and specific sensing strategies for cancerous cell detection with simple and low cost instrumentations provide great advantages in cancer research and early diagnosis of diseases. In the present work, gold nanoparticles (Au NPs) functionalized with recognition components (folic acid) and signal indicator (ferrocene) was designed to fabricate electrochemical cytosensor. The Au NPs can not only accelerate electron transfer between signal indicator and the underlying electrode but also accumulate more ferrocene on the cytosensor surface to magnify signal for improving detection sensitivity. A wide detection range from10to106cells/mL with a detection limit as low as10cells/mL for cancerous cells was reached in the presence of a large amount of normal ones with fast differential pulse voltammetry measurement. Detection of the captured cells can be finished within1min. The developed strategy provides a new way for operationally simple, rapid, sensitive and specific detection of cancerous cells. |
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