Miniaturization And Performance Evaluation Of Glucose Sensor With Embeddability

With the increasing number of diabetic patients,more and more people pay attention to the corresponding detection and diagnosis methods.Traditional blood glucose measurement method requires frequent finger blood collection,which brings pain and inconvenience to patients,but also increases the risk of infection.Therefore,the development of non-invasive continuous blood sugar detection technology has become an urgent problem to be solved.The emergence of flexible wearable devices opens up a new research direction for the realization of non-invasive continuous blood glucose detection.By identifying the glucose content in readily available body fluids(tears,sweat,saliva),and by means of the quantitative relationship between the glucose concentration in body fluids and blood sugar,the blood sugar level can be indirectly reflected.Therefore,non-invasive continuous blood glucose detection based on flexible wearable equipment has become a hot topic of current research.In the construction of flexible wearable devices,the key issue is the miniaturization of biosensors.In the process of miniaturization,there are some problems to be solved.Firstly,the immobilization of enzyme on biosensor surface must be non-toxic,harmless and non-irritating to human body.Secondly,the reference electrode is designed and manufactured,which needs further oxidation to form Ag Cl/Ag reference electrode.Finally,the design and fabrication of micro-sensors need to have a certain degree of embeddability,when embedded in the appropriate substrate,it can achieve direct contact with easily accessible body fluids.Based on the above background,this paper focuses on the construction of embeddable glucose sensor and its performance evaluation.Firstly,based on the requirement of wearable devices for enzyme immobilization,several methods of enzyme immobilization on electrode surface are discussed,and the detection performance of corresponding sensors is evaluated.On this basis,the screen-printed electrodes are used to simulate the glucose detection of microelectrodes.Finally,flexible microelectrodes are designed and fabricated,and the reference microelectrode is fabricated by constant current oxidation technology.Then microelectrodes are embedded into contact lenses to detect the concentration of glucose in tears.The details are as follows:1.Screening of GOx Immobilization Method Based on Wearable Equipment ConstructionIn this chapter,four kinds of GOx immobilization methods based on wearable devices are discussed,and the best immobilization method is selected by comparing the detection performance of the corresponding sensors.The tentative results show that:(1)In the four methods of sol-gel,polymer PMEH immobilization,Au nanoparticle adsorption and cross-linking,the glucose sensor constructed by high polymer PMEH fixed GOx has the fastest response speed,and the current response balance can be achieved within 25 s.In the concentration range of 0-0.6 m M,the response current has a good linear relationship with the concentration of glucose,and the minimum detection limit is 0.05 m M.(2)The glucose sensor constructed by polymer PMEH immobilized GOx has excellent repeatability and stability.After three days of placement,the sensor can still maintain its initial detection performance.It can eliminate the influence of interfering substances in tears and meet the performance requirements of sensors in practical application.2.Detection of Glucose by Simulated Microelectrodes with Screen Printed ElectrodesIn this chapter,silver wire is used to simulate the oxidation of Ag electrode in microelectrodes,and the detection performance of Ag wire as a reference electrode is explored.Considering the difference between macro-electrodes and micro-electrodes and the high cost of microelectrodes processing,we attempt to simulate the detection of glucose by screen-printed electrodes,and explore the effect of enzyme immobilization on the detection performance of micro-electrodes.The tentative results show that:(1)The open-circuit potential difference between the oxidized silver wire and the conventional macro-reference electrode is between 1 and 1.8 m V.As a reference electrode for glucose detection,good results have been achieved.(2)Consistent with the conventional macro-electrodes,the screen-printed electrodes modified by PMEH curing enzyme have the best detection effect and the fastest response speed.The response current balance can be achieved within 20 s,and the minimum detection limit is 0.039 m M.(3)The sensor obtained by surface modification of GOx on screen-printed electrodes by polymer PMEH curing method has excellent repeatability,stability and anti-interference.3.Preliminary Study on Detecting Glucose Based on Embedded MicroelectrodesOn the basis of the first two chapters,the flexible microelectrodes are designed and fabricated.Then the quasi-reference electrode Ag is oxidized to Ag Cl.After the oxidation,the pre-embedding glucose detection experiment is carried out.Finally,microelectrodes are embedded into contact lenses for glucose detection.Preliminary experimental results show that:(1)After constant current oxidation treatment,the potential difference between the reference electrode and the macro-reference electrode decreases significantly,and the potential is stable.(2)Before embed into the contact lens,the microelectrodes have a good linear response to the glucose solution in the concentration range of 0-0.6 m M.When the glucose solution is added,the microelectrodes could reach the response current balance within 10 s,and the minimum detection limit is 0.02 m M.(3)The designed and fabricated microelectrodes can be well embedded in contact lenses.After embedding,the microelectrodes still have current response to the addition of glucose,but the detection performance needs to be improved.