New Biosensing Methods Based On Two-dimensional Sheet Nanomaterials And Fluorescent Polydopamine

As an innovative detection technique,biosensor technology is continuously promoting the development of various fields.As the product of multidisciplinary interdisciplinary,biosensing technology condenses the advantages of various disciplines such as physics,biology,chemistry,infor mation science and medicine.Compared with other detection technologies,biosensor technology has unique advantages in many aspects,and has been widely used in various fields such as food,environment and medical detection.Although there are many advanta ges of biosensor technology,the original biosensor technology still has technical shortcomings in some aspects and fields.With the advent of nanotechnology and a series of new nanomaterials,biosensing technology has been further developed,and nanoscien ce has provided a new direction for the development of biosensors.In this paper,a series of biosensors with good specificity,fast analysis speed and suitable for small molecule detection were constructed based on three nanomaterials.The d etails are as following:(1)In chapter 2,Glutathione(GSH)plays an important role in cells which is an essential endogenous antioxidant.Here,we developed a new detection platform to analyze GSH levels.In our system,fluorescent polydopamine(F-PDA),as signal indicators,was obtained by oxidation of cobalt oxyhydroxide(Co OOH)nanosheets.When Co OOH was present,Co OOH could fleetly oxidize dopamine to F-PDA particles.But once GSH was present,Co OOH nanosheets would be decomposed,and the oxidation between Co OOH and dopamine was prevented wih the weaker fluorescence occurring.Thus,we could realize the detection of GSH concentration according to the decreased fluorescence value of the fluorescent polydopamine.This method provided a fast,simple,high sensitivity and desirable selectivity platform for GSH monitoring.(2)In Chapter 3,silver ion(Ag⁺)is a common substance in nature.Once the amount of silver ion exceeds the normal range,it will not only cause environmental damage but also endanger human health.At the same time,as an important biologically active cation,it can be combined with many metabolites and t he accumulation of silver ions in the body can inactivate thiol ase and induce various diseases.Here,we developed a new method based on GSH-mediated Co OOH-TMB system for Ag⁺detection.Ag⁺could be specifically detected using the color reaction between Co OOH and TMB and the redox reaction between Co OOH and GSH.When Ag⁺was absent,GSH would firstly react with Co OOH and then reduced it to Co²⁺,causing Co OOH to lose its oxidizing ability and could not continue to oxidize TMB.When Ag⁺was present in the system,Ag⁺was closely bound to GSH,and Co OOH was not decomposed by GSH.It could continue to oxidize TMB to make it blue.Based on this,we could realize the detection of Ag⁺concentration through the changes of TMB absorbance value.(3)In chapter 4,GSH plays an important role in living cells.The decrease in GSH concentration in the human body is related to various diseases.Therefore,sensitive detection of glutathione concentration is very important.Here,we developed a new GSH detection method based on fluorescent polydopamine(F-PDA)nanoparticles.As a kind of polymer nano-fluorescent particles,F-PDA nanoparticles have good particle stability and biocompatibility.Based on this property of F-PDA,we constructed the F-PDA-Mn O₂ nanocomposite for rapid detection of GSH.Manganese dioxide(Mn O₂)could adsorb F-PDA.Due to the strong FRET effect between them,the fluorescence of F-PDA was quenched.When GSH was present in the system,GSH in the system react ed with Mn O₂ at first and then GSH could reduce it to Mn²⁺and made it lose its quenching ability.It could not continue to quench the fluorescence of F-PDA and the fluorescence of F-PDA was reserved.In the system we developed,the signal indicator was F-PDA,and changes in GSH concentration could be detected by observing the fluorescence change of the particles.This sensing method showed strong detection ability in GSH analysis.