Study Of Novel Nano-optical Sensing System For Detection Of Heavy Metal Ions In Biological Samples

In recent years,various environmental problems and diseases caused by the heavy metal ions have brought serious challenges and opportunities to the development of analytical chemistry,the development of new analytical testing strategies become one of the important ways to solve the current problems.The rapid development of nanotechnology strongly promotes the progress of analytical techniques and biotechnology,with the cross-integration of nanotechnology and biosensors,nano-biosensors have already become the international research frontier in the field of biotechnology.Due to its simple operation,rapid response,high sensitivity in bioanalytical applications,nanobiosensors have become a hot spot in the new detection technology.To date,many researchers at home and abroad have done a large number of theoretical and practical research for the applications of nanomaterials in the field of biosensors,and a breakthrough has been made,which provides a solid foundation for the vigorous development of nano-biosensors.With the emergence of new nanomaterials and the constant improvement of the structure and propertiies of the existing nanomaterials,it will create a more broad prospects for the application of biosensors.The main contents of this paper is to utilize small functional molecules to modify the surface of nanomaterials,combining with the optical biosensor,we developed a series of new nano-biosensors for the detection of heavy metal ions in biological samples.The full text is divided into five parts,as follows:Chapter 1.OverviewFirstly,a critical review with regard to the definition,classification,application and development of biosensor and nanotechnology is given.In addition,it focuses on the development of new methods and strategies based on the combination of new functionalized nanomaterials and biosensors,especially the application in biochemical analysis are highlighted.Chapter 2.Highly sensitive and selective fluorescent detection of lead???in cerebrospinal fluid based on graphene quantum dot conjugatesWe developed a novel turn-on fluorescent probe based on GQD-DMA/tryptophan compound system for the detection of Pb²⁺.A rigid structure can be formed between the GQD-DMA/tryptophan compound system and Pb²⁺,which can result in the fluorescence enhancement of the compound system.A selective and sensitive strategy towards Pb²⁺ was developed,with a linear detection range from 0.01 nM to 0.9 nM,and the detection limit is 9 pM.Combined with the microdialysis sampling technique,we have applied this method to the detection of Pb²⁺ ions in the cerebrospinal fluid of rats and achieved convinced results successfully,which shows a prosperous application in the complexity biological samples.This work provides new methods and ideas for graphene quantum dots in the application of biosensing.Chapter 3.The development of a novel ratiometric fluorescent probe for mercury???in biological tissues based on terbium???/gold nanocluster conjugatesIn this work,a novel ratiometric fluorescent probe was developed for rapid,highly accurate,sensitive and selective detection of mercury???(Hg²⁺)based on terbium???/gold nanoclusters conjugates(Tb³⁺/BSA-AuNCs),and the detection limit is as low as 1 nM.In addition,our proposed probe was effectively employed to detect Hg²⁺ in the biological samples from the artificial Hg²⁺-infected rats,an appealing paper-based visual sensor for Hg²⁺ was designed by the filter paper embedded with Tb³⁺/BSA-AuNCs conjugates,which can be readily observed with naked eyes for the Hg²⁺ concentrations by the change of the color.This work unveiled a facile approach for accurate,sensitive and selective measuring of Hg²⁺ with self-calibration,which widened the application of AuNCs in different fields.Chapter 4.The development of a novel ratiometric fluorescent probe for mercury???based on silica coated gold nanoclustersIn this work,a facile,rapid and label-free ratiometric fluorescent probe is proposed for the determination of mercury ion(Hg²⁺)based on the combination of Hoechst dye and AuNCs@SiO₂-DNA.Hg²⁺ can recognize thymine enriched with T base specifically and form the ligand structure of T-Hg²⁺-T,Hoechst can enhance its fluorescence significantly.Based on this principle,the unlabeled fluorescence analysis for Hg²⁺ is developed.In the presence of Hg²⁺,the fluorescence at around 488 nm was found to be strengthened and constant at 646 nm and the fluorescence intensity ratio?F488/F646?was sensitive to the concentration of Hg²⁺.And the selectivity of the fluorescent probe towards Hg²⁺ was also examined,the results showed that the probe has no response for other interfering ions,even if the concentration of interfering ions is ten times over Hg²⁺,indicating that the method has good specificity.Chapter 5.The development of a colorimetric assay for Mn²⁺ in brain tissues based on cysteic acid-capped silver nanoparticlesA new facil colorimetric assay is proposed for the determination of manganese ions(Mn²⁺)utilizing cysteic acid?CA?-capped silvernanoparticles?CA-AgNPs?.Mn²⁺can form a coordinated structure with CA capping on the AgNPs and induces the quick aggregation of CA-AgNPs,associated with notable changes of the CA-AgNPs solution color from yellow to dark green.We also used density functional theory?DFT?to disscuss the mechanism of the action,which shows that CA-AgNPs have high specificity for Mn²⁺,and the detection limit is as low as 5 nM,Furthermore,the proposed method was successfully applied in detecting Mn²⁺ in a rat model of focal ischemia and the results indicate that our proposed method has great potential for practical applications.