Research On Chemical And Biosensors Based On Metal-organic Frameworks And DNA Nanoclusters

Metal-organic framework materials(MOFs)are new type of crystalline porous materials obtained by molecular assembly of metal ions or metal clusters and organic complexes.They have many excellent features such as super high surface area,adjustable pore size,easy to functionalized channel and highly ordered.Metal nanoclusters are composed of several to dozens of metal atoms with good fluorescence properties and catalytic properties like enzymes.In this paper,a series of chemical and biological sensors were prepared through synthesizing metal-organic frameworks and DNA-metal nanoclusters as signal probes.The targets were detected by direct determination of the reduction peak of metal ions in the metal organic framework and the peak current of the metal ions in the nanoclusters.(1)Nano-porous Pt materials was synthesized by reduction reaction,and was characterized by TEM.Nano-porous Pt materials,as a nano-mimic enzyme,has a good catalytic effect on the reaction of hydrogen peroxide with 3,3’,5,5’-four methyl diphenyl amine(TMB)to form blue oxidation products.Dopamine(DA)can adsorb on the pore of nanoporous Pt,which reduced the catalytic site and inhibited the catalytic effect of nanoporous Pt,resulting in the decrease of TMB oxidation products and the decrease of absorbance.In this study,inhibitory effect of dopamine to the catalysis of porous Pt NPs was used to realize the quantitative detection of dopamine using ultraviolet spectrophotometer(UV-Vis).Under the optimal experimental conditions,the detection range of the system is from 0.08 mmol/L to 1.0 mmol/L with a good linear correlation coefficient of 0.996 and the detection limit of 0.0085mmol/L.This system provides a new,simple as well rapid method on the detection of DA and can be used for the detection of DA in cell.(2)The metal organic frameworks(MOFs)Cd-MOF-74 was synthesized by hydrothermal synthesis,Cd-MOF-74 was modified on glassy carbon electrode to prepare electrochemical sensor.This sensor was used for the determination of clenbuterol hydrochloride.The results showed that the modified electrode had good electrocatalytic activity to the clenbuterol hydrochloride.Experimental conditions such as support medium and enrich potential were optimized.Under the optimal conditions,The oxidation peak current increased with the concentration of clenbuterol hydrochloride in the range of 1.6 to 800 ?mol/L,with a limit of detection 0.53 ?mol/L.This sensor has good stability,long lifetime and simple production procedure.It can be applied to the quantitative determination of clenbuterol hydrochloride in practical samples with satisfactory results.(3)A signal off-electrochemical aptasensor was prepared based on copper nanoclusters(Cu NCs)synthesized in situ using aptamer DNA of ochratoxin A(OTA)with extra 30 mer of thymine(T)at the terminal as template to realize fast and sensitive determination of OTA.In this study,3′ terminal thiolated DNA1,which was complementary with aptamer of OTA partially,was first immobilized onto the electrode surface.Then,the OTA aptamer was immobilized on the electrode surface by forming complementary hybridization duplexes.Moreover,30 mer of thymidine T at the terminal of aptamer DNA could be used as DNA template to synthesize Cu nanoclusters.In the existence of OTA,it can specific bind with its aptamer,which lead to the dissociation of aptamers from the complementary duplexes.The higher concentration of OTA in the solution is,the more the aptamer DNA dissociated from the hybridization duplexes,the less the copper nanoclusters were synthesized on the electrode.Therefore,quantitative determination of OTA can be achieved.Under the optimal experimental conditions,the detection range of the aptasensor is from 0.1ng/m L to 50 ng/m L with a good linear correlation coefficient of 0.993 and the detection limit of 0.033 ng/m L.This aptasensor provides a simple and rapid method for the detection of OTA and can be used for the detection of OTA in coffee samples.(4)A novel aptasensor for ultrasensitive and rapid detection of ochratoxin A(OTA)was developed using metal-organic frameworks(MOFs)as signal unit.In this work,MOFs were utilized as signal probe.And the signal probes differs from traditional probe,the signal of the cadmium ions(Cd2+)from MOFs can be directly detected without acid dissolution and preconcentration,greatly simplifying the detection steps and reducing the detection time.Moreover,MOFs contain large amounts of Cd2+ ions,which could provide high electrochemical signals.Our report is the first time using MOFs themselves as electrochemical signal probe for aptasensor application.Gold nanoparticles(Au NPs)-doped molybdenum disulfide(Mo S2)nanocomposite was employed as an immobilized matrix for the sensor because of the high electronic conductivity.Under the optimized experimental conditions,an ultrasensitive aptasensor for the detection of OTA exhibited a wide linear range of0.05-100 ng/m L,with a low detection limit(LOD)of 10 pg/m L OTA(at 3?).With these merits,this stable,simple,low-cost,sensitive and selective electrochemicalaptasensor shows promise for applications in environmental monitoring.(5)A sandwich-type aptasensor based on the metal-organic framework Fe-MIL-88NH2 for the rapid detection of thrombin was developed.In this study,amino-functionalized metal-organic framework(Fe-MOFs,Fe-MIL-88NH2)was used as signal probe,gold nanoparticle modified covalent organic frameworks(Au NPs@COF-LZU-8)with high electronic conductivity was employed as the substrate to immobilize thrombin aptamer Ⅰ(TBAⅠ).After thrombin binds specifically with TBAⅠ,it combines with thrombin aptamer Ⅱ which was covalently cross linked with Fe-MIL-88NH2 through glutaraldehyde.Then,iron ions(Fe3+)from Fe-MIL-88NH2 were directly detected without acid dissolution and preconcentration.Under the optimized experimental conditions,the current response of Fe3+in Fe-MOFs was directly proportional to the concentration of thrombin.The detection range of the aptasensor is from 0.5 ng/ml to 200 ng/ml,with a linear correlation coefficient of 0.987 and a detection limit of 0.167 ng/m L.In this strategy,the sensor signal probe is functionized with amino groups,which can be combined with aptamer modified with-NH2 through glutaraldehyde.Furthermore,the peak current of iron ion(Fe3+)in Fe-MOFs can be detected directly,which simplifies the experimental steps greatly.This article expands the application range of MOFs.