The Application Of Fluorescent Nano-probes In Biochemical Detection

Some biomolecules of biological, such as amino acid, protein, reactive oxygen species, cation, anion and neutral molecules et al., plays vital roles in metabolic processes of biological activity. Abnormal concentrations of these biomolecules was warning about some diseases and even resulted in serious issues, such as malignant tumor, Alzheimer’s disease and Parkinson’s disease. Now, enzymes or substrates, chemical or biological luminescence systems and fluorescence materials were commonly used in biological analysis. Radioactive isotopes were expensive used in early phase, which was used rarely now because it would damage the human body and environment. Although the enzyme immunoassay had no radioactive pollution problem, the enzyme itself will lose its activity easily. The sensitivity of chemical and biological luminescence analytical method was sufficient, but it was influenced easily by the environment and its stability was relatively poor, and after the moment of chemical reaction, the light-emitting of samples couldn’t reproduce, the result wasn’t reproduced. Optical biosensors based on fluorescent nanomaterials have developed rapidly and made remarkable achievements in recent years. They are used widely in the fields of disease diagnosis and analysis. Compared with the traditional optical biosensors, these biosensors possess higher sensitivity and wide dynamic range and they could be used for real-time monitoring.As the core of the biosensors, the fluorescent nanomaterials are widely used in the fabrication of biosensors due to their excellent fluorescent properties such as symmetric and narrow fluorescence, excellent robustness against photobleaching. Fluorescent nano-probes were showing more and more attractive application prospect in molecular biology, immune biology, clinical medicine et al. biomedical fields. Because most biomolecules have no fluorescence or weak fluorescence, the sensitivity of detection was relatively poor in clinical diagnosis, so the determinand need be marked by the strong fluorescence probe leading the detection limit to reduce greatly. In medical imaging, the fluorescent nano-probes were used to mark the living organism in vivo to monitor the cells and have the tissues imaging. In military medicine, the fluorescent nano-probes could detect the biological toxin timely and rapidly, the ability is an effective measure for defensing against biological weapons. Fluorescent nano-probes had been applied to detect a variety of bacteria, viruses, and toxins, which also could be used to measure the acetic acid, lactic acid, lactose, uric acid, urea, antibiotics, glutamic acid and other special amino acids and a variety of carcinogenic and cancerous material.In this study, three kinds of fluorescent nano-probes are synthesized and they are adopted to fabricate the biosensor. The experiment conditions and mechanism are well discussed. The main results are outlined as follows:1, Highly fluorescent core/shell SiO2@CdTe nanoparticles （NPs） were synthesized conveniently and efficiently via a hydrothermal method. The as-prepared SiO2@CdTe NPs were uniform with good fluorescence preservation. The SiO2@CdTe NPs could be used for the rapid detection of H2O2 with good sensitivity within several minutes. Excellent linear relationships existed between the quenching degrees of the SiO2@CdTe NPs and the concentration of H2O2 in the range of 0.005 mM to 0.1 mM. The limit of detection （LOD） for H2O2 was 10 nM. Furthermore, it was proved that SiO2@CdTe NPs could be used repeatedly for H2O2 detection due to their easy separation, which is an important feature. The excellent performance of SiO2@CdTe NPs should facilitate their applications in chemistry or biology for detection of H2O2.2, A convenient ratiometric fluorescent method for determination of ROS were developed based on a nontoxic nanohybrid system which was constructed by carbon dots （CDs） and gold nanoclusters （Au NCs）. The combination were prepared easily based on self-assembly without any complex process and have achieved maximum reservation of the two fluorescent properties. The fluorescent ratio probe have many advantages, such as decreasing interference, low toxic, high sensitivity and accuracy. We had successfully built a novel ratio fluorescent system for the detection of H2O2 and ClO-, and the limit of detection （LOD） for hydrogen peroxide （H2O2） and hypochlorite （ClO-） could as low as 0.1 μM after the experimental conditions are optimized. Additionally, the test paper provided a convenient visual detection method with double fluorescence CDs/Au NCs which were built to response H₂O₂. Furthermore, the biosensor was proven to be suitable for the detection of H2O2 and glucose （Glu） in human serum examples. The proportion of CDs and Au NCs could be adjusted optionally to different color with high physiological stability and excellent biocompatibility. The excellent performance of this ratiometric biosensor will facilitate future development of rapid and high-throughput detection of ROS.3, A simple, fast, convenient, sensitive detection method for the dopamine （DA） was built using the fluorescence of the carbon dots （CDs）. The sensitive determination of DA was studied primarily on the basic of the principle. DA would be transformed into DA quinone under alkaline conditions, which resulted in fluorescence quenching of the CDs. The fluorescence exhibited a good linear range with a detection limit of 1 nM. Moreover, the quenching function of quinone structure on the fluorescence of CDs was confirmed by a series of characterization means. Remarkably, CDs were firstly applied to detect the quinone drugs quantitatively which contained typical quinone structure based on the quenching mechanism. More than this, the sensing platform was demonstrated could provide credible anti-interference ability. Hence, our practical application and mechanism have showed great potential for diagnostic purposes.