The Detection Of Small Molecule Based On Metal-Organic Framework

Pyrophosphate anions?PPi?and copper ions(Cu²⁺)play a very important role in the fields of biology,environment and industry.Therefore,it is of great significance to establish rapid and simple methods for the detection of PPi and Cu²⁺.Metal-organic framework?MOF?is a new type of multifunctional material and has been considered to be one of the important sensing materials due to the unique structure and fascinating properties.Herein,two strategies for sensitive detection of PPi and one strategy for sensitive detection of Cu²⁺are proposed by fluorescent spectrometry and Uv-visible spectrophotometry based on MOF.The details are as follows:Firstly,a fluorescent spectrometry based on MOF for PPi assay is established used the fluorescein?FAM?-labeled single-stranded DNA?FAM-ssDNA?as a signal bridge.MOF can efficiently adsorb ss-DNA and quench the adsorbed fluorophores to a large extent.PPi can destroy MOF's structure by interacting with metal ions in MOF and weaken the adsorption capacity of MOF to single stranded DNA.In the absence of PPi,the FAM-ssDNA is adsorbed to the surface of MOF and then the fluorescence of FAM is quenched.In the presence of PPi,the fluorescence of FAM is restored due to desorption of FAM-ssDNA from MOF.As a result,PPi can be detected by recording the change of fluorescence intensity of the system.The results show that the linear range of this method for detecting PPi is 0.1?M to 10?M and the data of the selectivity and the applicability in real samples are generally satisfactory.The materials used in the strategy are easy to prepare and low cost while the PPi testing scheme can be completed in one step and about 20 minutes.Moreover,the sensitivity of this method is higher than or equal to the methods reported in the current literature.Consequently,the proposed strategy provides a simple and practical method for detecting PPi in environment and biological systems.Secondly,a spectrophotometric method for PPi assay is established based on the peroxidase activity of MOF and the strong coordination between MOF and PPi.3,3',5,5'-tetramethylbenzidine hydrochloride?TMB?is used as the catalytic substrate.Without the addition of MOF,the oxidation capacity of hydrogen peroxide?H₂O₂?to TMB is very weak.In the presence of MOF,due to the peroxidase activity of MOF,MOF first catalyzes H₂O₂ to generate hydroxyl radical,and then hydroxyl radical further oxidizes TMB to a blue oxidation state TMB?oxTMB?.As a result,the reaction solution changes from colorless to blue,and has a strong absorption at 652 nm.When PPi is added,the structure of MOF material is changed due to the coordination combination of PPi and metal ions of MOF,which results the MOF-catalyzed reaction is inhibited and the solution is still nearly colorless.The PPi is detected by measuring the absorbance of the reaction solution with spectrophotometer.The results show that the method can realize the quantitative analysis of PPi within the concentration range of 0.1?M to 5?M and and it is proved that the method has good selectivity and practicability.Compared with the fluorescence spectroscopic method established in this paper,this method is comparable in terms of sensitivity,analysis speed and the simplicity of the experimental scheme and then the instrument used in this method is more simpler and cheaper,which indicating that it is more conducive to the future popularization and application.Thirdly,a spectrophotometric method for Cu²⁺assay is established based on the peroxidase activity of MOF and the competitive combination between MOF,Cu²⁺and PPi.PPi inhibites the peroxidase activity of MOF,but after the introduction of Cu²⁺,the peroxidase activity of MOF is recovered because the complexing force between PPi and Cu²⁺is stronger than that between PPi and MOF.As a result,the color of the reaction solution turns blue and the absorbance of the system increases.The Cu²⁺is detected by measuring the absorbance of the reaction solution with spectrophotometer.The results show that the concentration of Cu²⁺in the range of 0.25?M to 25?M has a good linear relationship with the absorbance of reaction solution and the presence of other cations does not interfere with the determination of Cu²⁺.This method uses spectrophotometer which is cheap and easy to operate,and only needs 30 min to complete the detection.Therefore,this protocol shows great potential in low cost,simple and rapid detection of Cu²⁺.