Quantum Dots And Enzymes Embedded In Sodium Alginate Hydrogel Microbeads For Point-of-care Testing Of Uric Acid/Glucose

As a novel type of fluorescent nanomaterial,quantum dots（QDs）possess excellent optical and chemical properties,such as high quantum yield,large Stokes shift,wide absorption range,adjustable emission spectrum,good photostability,easy functional modification,and good biocompatibility.Therefore,it is widely used in the fields of biosensing,fluorescent coding,cell imaging,and virus tracing.Fluorescence immunochromatography and loop-mediated isothermal amplification which employing QDs as fluorescent markers have attracted much attention in point-of-care testing（POCT）for a long time.In recent years,as the function of smartphones has become increasingly powerful,QDs start combining with them to build the POCT method.However,QDs are difficult to be applied for POCT of protein-rich samples（serum,urine,etc.）due to their weak anti-protein interference ability and difficulty in long-term preservation.Therefore,it is of great significance to construct a sensor that enables QDs to stably exist in the protein-rich environment.In this paper,sodium alginate hydrogel was employed as a carrier to embed with QDs and enzymes,and selectively regulated the mesh size on the surface of the hydrogel to obtain an optical sensor with no QDs leakage and no proteins pass through.By embedding urate oxidase（UOx）and glucose oxidase（GOx）respectively,the POCT method for the detection of uric acid（UA）and glucose（GLU）was established.The idiographic research contents were as follows:（1）The Cd Zn Te S QDs with an emission wavelength of 530 nm were prepared according to the existing methods of our research group.Sodium alginate hydrogel microspheres（Alg@QDs-UOx MSs）embedding with Cd Zn Te S QDs and UOx was synthesized in situ by using a high concentration of Ba Cl₂ solution as a cross-linking agent.The surface of Alg@QDs-UOx MSs was a dense multi-layer network structure,which could prevent QDs and protein molecules from entering and leaving.Therefore,Alg@QDs-UOx MSs had good anti-protein interference ability and could be directly analyzed in unpretreated biological samples.The stability of Alg@QDs-UOx MSs during the preservation process was researched.And it indicated that the Alg@QDs-UOx MSs could prevent the quenching of internal Cd Zn Te S QDS and the inactivation of UOx.In addition,the built-in camera of a smartphone was replaced the large laboratory equipment as a detector for achieving the quantitative determination of uric acid（the linear range of uric acid detection was 100-900μmol/L,the detection limit was 20.3μmol/L）.It also could be applied to POCT of UA in actual samples（urine and serum）.It was worth mentioning that this method was employed to screen patients with hyperuricemia with high accuracy and no false-positive results.（2）Based on the above work,we replaced the embedded substances with Cd Zn Te S QDs of 620 nm emission wavelength and GOx,and used the same method to obtain Alg@QDs-GOx MSs.Then,based on Alg@QDs-GOx MSs,a fluorescent color card of glucose concentration within 0.1-1.0 mmol/L was acquired by referring to the preparation method of the standard colorimetric card.It was employed to realize semi-quantitative determination of serum glucose and urine glucose.A large number of actual samples were analyzed,and the results displayed that this method had a good application prospect in the primary screening of diabetic patients.This method was universal.Different small molecules could be realized POCT by changing the embedded substances in sodium alginate hydrogel microspheres.In addition,comparing this method with the solution detection method,the simultaneous detection of different small molecules was easier to carry out due to the detection zone was limited to a single sodium alginate hydrogel microsphere.Combined with the work of chapter 2,a fluorescent color card with a concentration of 0.1-0.9 mmol/L uric acid was constructed,and the simultaneous detection of GLU and UA in human urine was came true.