Application Of Fluorescent Silver Nanoclusters Molecular Beacon In Fluorescent Biosensors

In recent years,with the continuous development of science and technology,more and more people are paying attention to fluorescent biosensors.Fluorescent biosensors are application in various fields such as chemistry,physics,biology and optics.Due to the special optical properties of fluorescence and the change of the fluorescent signal,the fluorescent biosensors can detect the small molecule,nucleic acid,metal ion and so on.As a type of detection methods,fluorescent biosensors have high sensitivity,short time-consuming,simple operation,good selectivity,low cost and many other excellent performances.They have become hot topics,and the people have started in-depth research.Nanomaterials,especially metal nanoclusters with fluorescence,have been widely used in the field of fluorescent biosensors,which are due to their unique properties such as good selectivity,non-toxicity,low cost and high sensitivity.With the continuous advancement of science and the in-depth research on fluorescent biosensors,we need some fluorescent biosensors with better performance.Therefore,this paper focuses on high performance fluorescent biosensors.1.A brief introduction of fluorescent biosensors with the characteristics,preparation methods and practical applications.The properties,synthesis and application of gold,copper and silver nanoclusters in fluorescent metal nanoclusters are respectively described.At the same time,the main content and research significance of this methods are expounded.A method for the detection of adenosine triphosphate?ATP?based on high sensitivity and label-free silver nanocluster fluorescent molecular beacon?MB?was proposed.The sensor comprises a hairpin silver nanoclustered molecular beacon,two short single stranded DNA?ssDNA?sequences and a T4 DNA ligase.The molecular beacon consists of three parts:the 5'end is a DNA sequence of synthetic silver nanoclusters;the middle DNA sequence forms a hairpin-like structure;and the 3'end is a G-rich DNA sequence.When ATP is absent,the 5'end of the molecular beacon?MB?forms a silver nanocluster with a weak fluorescent signal.At this time,however,the intermediate sequence of the molecular beacon forms a hairpin-like structure,so that the G-rich sequence at the 3'end is close to the silver nanocluster at the 5'end,which will result in an enhancement of the fluorescent signal of the silver nanocluster.Therefore,when we use this probe to detect ATP,the two short DNA strands in the sensor form a long chain under the action of ATP and T4 DNA ligase,which can open the hairpin structure of the molecular beacon.Thereby,the 3'end and the 5'end of the molecular beacon are separated,so that the fluorescence of the system is lowered.The magnitude of the fluorescence drop is directly proportional to the amount of ATP to be detected,so we can detect the ATP content in the system by the decrease in system fluorescence.Compared with the traditional method,this sensor has the advantages of no mark,low cost and high sensitivity.3.Alkaline phosphatase?ALP?was detected using a highly sensitive,label-free silver nanoclone molecular beacon?MB?with a hairpin-like structure.Simultaneously,we selected a single-stranded DNA?ssDNA?containing a phosphate group?-PO₄?at the 5'end.When ALP is present,the-PO₄ at the 5'end of the short-chain ssDNA is removed from the 5'end of the ssDNA due to the enzymic catalytic reaction of ALP.The-PO₄ at the 5'end of the short strand of the ssDNA was converted into the-OH.At this time,due to the disappearance of-PO₄,T4 DNA ligase could not work,the hairpin structure of MB could not be opened,and the fluorescence of the system was strong.When there is no ALP,ssDNA and MB form a stable double helix under the action of T4 DNA ligase.In this double helix structure,the hairpin shape of MB is opened,and the 5'end and 3'end are separated.The fluorescence enhancement phenomenon of the silver nanocluster disappears and the fluorescence of the system is weak.The presence of ALP can be detected by changes in fluorescence intensity,and the ALP content is proportional to the fluorescence intensity of the system.The method is simple in operation,fast in response,and high in sensitivity.