The Preparation Of Fluorescent Hydrogel Microspheres And Its Application In Visual Detection Of Lactate

Lactate,a direct product of anaerobic metabolism,is an important health indicator.Glycogen in muscles is consumed to produce energy and lactate in the anaerobic metabolic process.The accumulation of lactate in the muscles squeezes blood vessels,restricts blood flow,and leads to soreness and muscle fatigue.The level of lactate in the bio-fluid is related to heart failure,circulatory failure,hypoxia,metabolic disorders,respiratory failure,renal failure and other diseases.In addition,lactate is the primary cause of acidification in a microenvironment of cancer cells,it also plays an imperative role in cancer diagnosis.However,most of the current methods for lactate detection have some drawbacks,such as time consuming,expensive instrumental and requiring trained personnel.Thus,it is in great need to develop a rapid,simple and low-cost analytical method to monitor lactate.As one of the fluorescent nanoparticles,semiconductor quantum dots(QDs)have been widely used in biosensing owing to its unique optical properties like tunable emission wavelength,high quantum yield,and long fluorescent lifetime.Visual detection has been generally associated with portability for on-site analysis,low cost,and simple instrumental.It can be readily observed and interpreted by naked eye,which has great potential for application in areas with limited resources.In this paper,combining the advantages of semiconductor quantum dots with visual detection,a new method for the detection of lactate was developed.The main research contents are as follows:(1)The green-emitting Cd Te QDs were synthesized through a one-step hydrothermal route according to our previous work.The alginate hydrogel microspheres(Alg@QDs-LOx MSs)embedded with Cd Te QDs and lactate oxidase(LOx)were prepared in situ after crosslinked by Ba²⁺.When lactate was present,LOx in the microspheres oxidized lactate to produce H₂O₂,which could quench the fluorescence of Cd Te QDs.Therefore,the fluorescence quench of microspheres could be observed by naked eye.The results revealed that Alg@QDs-LOx MSs could be employed to detect lactate within 15 min in the range from 50?M to 1500?M with a detection limit of 1.25?M.Furthermore,the unique structure of Alg@QDs-LOx MSs prevented interference from proteins in biological matrix,and improved the storage stability of lactate oxidase.More importantly,this method was employed to screen patients with hyperlactatemia successfully,and comparing with clinical results,the accuracy rate of this method was 87%.(2)It is difficult to differentiate two identical colors with only<15%variation in brightness by eye.The fluorescence sensor employed single fluorescent intensity as the only responsive signal in the above work,which was readily affected by experimental factors and caused eye fatigue.Accordingly,in this work,bicolor fluorescent hydrogel microspheres were prepared by introducing a fluorescent nanoparticle as reference signal.Meanwhile,relying on the image processing software of a smartphone,datas were collected and analyzed,and color cards for lactate detection were prepared.It showed a distinct color change to detect lactate using the bicolor fluorescent hydrogel microspheres,which could be distinguished easily by naked eye.The linear range of this method for lactate detection was 10?1500?M with a detection limit of 1.22?M.It was worth mentioning that accuracy rate of this method to screen patients with hyperlactatemia was 93%,which improved obviously comparing with the above work.