Detection Of Drugs And Target DNA Based On A Multi-functional Sensing Platform Based On Fluorescent Silver Nanoclusters

Noble metal nanoclusters are a kind of semiconductor nanoparticles that are developed in recent years.Due to the unique nature of optics/electricity,biocompatibility,water solubility,and low cytotoxicity,they are widely used in chemical sensing,biomarker,disease diagnosis and so on.In this paper,polyethyleneimine-capped silver nanoclusters(PEI-Ag NCs)are utilized as a fluorescence probe for detection of quinolones,vitamin B12,target DNA and adenosine triphosphate(ATP).The main contents of dissertation are summarized as follows:(1)In this chapter,Ag NCs capped by PEI with different molecular weights(Mw=600,1300,1800,2000,10,000,25,000,70,000,750,000)were developed as a novel fluorescence probe for the detection of quinolones.The fluorescence intensity of Ag NCs could be quenched efficiently by Cu2+,while with the addition of quinolones,including nalidixic acid,cinoxacin,ciprofloxacin/ofloxacin and moxifloxacin,the fluorescence of this system recovered rapidly.The Ag NCs-Cu2+ system showed good linear ranges and low detection limits of quinolones.Benefiting from the high sensitivity,the satisfactory recoveries were obtained for trace detection of quinolones in real samples,such as tablets,human urine and plasma.(2)In this chapter,Ag NCs templated by PEI with different molecular weights(Mw 600,10000 and 70000)and terminal groups called as ethylenediamine and ethoxylated were developed as a new fluorescent platform for the sensitive and selective recognition of Vitamin B12(VB12).These Ag NCs exhibited strong fluorescence emission,while the addition of VB12 could quench the fluorescence of Ag NCs based on the inner filter effect(IFE)between Ag NCs and VB12.The proposed sensing system also exhibited high selectivity and sensitivity to VB12,showing a wider linear range and lower limit of detection.Moreover,the proposed method was successfully applied for determining VB12 in real samples with satisfactory recoveries.(3)In this chapter,the fluorescent Ag NCs templated by PEI were utilized as a versatile biosensing probe through the photoinduced electron transfer(PET)between PEI-Ag NCs and G-quadruplex-hemin complexes.In the presence of hemin and target molecule,the specific conjugation with its aptamer induced the conformational change of the DNA sequence,releasing the G-quadruplex sequence part.Once the G-quadruplex-hemin complexes were introduced,the electron transfer from the PEI-Ag NCs to G-quadruplex-hemin complexes occurred resulting in the fluorescence quenching.With just a little change in the sensing sequence,this novel PET system enabled the specific detection of target DNA and ATP with the wide linear range.In addition,based on this quenching mode,using target molecules and hemin as inputs and the fluorescence signal of PEI-Ag NCs as an output,a logic gate was fabricated.