Study On Wearable Bioelectrochemical Sensors Based On Silk Protein

With the increasing needs of personalized medical,the convenient and comfortable medical devices are increasingly needed to manage their physical conditions anytime and anywhere.Based on the current market demand,wearable sensors have become one of the most popular research topics.Wearable electrochemical sensors are the most fascinating research because they can be used to analyze various metabolites such as glucose,lactic acid,sodium ions and calcium ions,which convert the concentration of analytes into measurable electrical signals through chemical reactions.In these body fluids,sweat contains many biomarkers,such as glucose,uric acid and lactic acid,which can be analyzed in sweat instead of blood analysis.However,the sensitivity and service life of wearable sweat sensors currently limit their development.In view of the above problems,three kinds of sweat sensors are designed and prepared,and their performance and practicability are analyzed in detail.The main research contents include:1.Silk fibroin-enzymic hybrid biochemical sensors have been developed.Enzymes are built into SF nanofibrils networks via intermolecular-templated nucleation.The hybridization of SF and enzymes prevents the loss of enzymatic functions due to intermolecular crystallization that freezes the possible unfolding processes.This increases the life-spin of enzymes for approximately 300 times,thereby enhancing the sensitivity for about 3 times,and reducing the reliable quantitation limit towards glucose for more than 5 times.These are substantiated by rendering the continuous effective detection period up to 20 days without losing more than 6%of the sensitivity and enhancing the sensitivity of glucose and lactate sensors up to 35.25 μA mM-1 cm-2 and 0.87 μA cm-2[log10(mM)]-1,respectively.On-skin in-line sweat measurements show good correlation between glucose concentration variation and behavior of glucose in blood before and after a meal.As the sensors are highly sensitive,comfortable,and long-term operational,they are particularly suitable for real-time human biochemical monitoring.2.We have developed a biologically active porous enzyme nanofiber(PEN)film composed of silk fibroin nanofibers(SFNFs)and enzymes,which can effectively retain the enzyme in its own three-dimensional space.The three-dimensional scaffold formed after SFNFs cross-linking can immobilize enzymes,providing a large surface area for molecular/ion diffusion and biochemical reactions.The porous enzyme nanofiber membrane was then attached to the ultrathin PtNPs/graphene(Pt-G)nanocomposite membrane to facilitate the electron transport between the enzyme and the electrode to achieve efficient long-term stable detection of glucose and lactic acid in sweat.The assembled glucose and lactic acid sensors have high sensitivity and good cycle reproducibility,especially their long-term stability of 25 h and 23.6 h,respectively.The working life of the constructed glucose sensor is about 1.25 times longer than that of the best sensor reported so far.In addition,a wearable real-time detection platform based on sensors has been developed for real-time analysis of glucose and lactic acid content in sweat during outdoor exercise,and the signal is transmitted to the mobile phone for real-time data reading.The high sensitivity,comfort and long-term stability of the device are beneficial to the long-term real-time monitoring of physiological state.3.Wearable electronic devices are widely used in various fields due to their own advantages,especially for the analysis of skin sweat components.In this study,we introduced polydopamine onto the surface of reduced graphene oxide(RGO)as a reducing agent to reduce Pt nanoparticles,and finally obtained a three-dimensional RGO composite(PtPRGO)in which Pt nanoparticles are evenly interspersed between RGO sheets.This three-dimensional RGO composite can expose more specific surface area and channels that facilitate the diffusion of ion/molecules,permitting highly sensitivity of sensors.The as-assembled glucose sensors,Ca2+ sensor and Na+ sensor demonstrate highly sensitivity up-to 71.12 μA mM-1cm-2,91.98 mV[log10(mM)]-1,and 88.58 mV[log10(mM)]-1,respectively.Meanwhile,these sensors demonstrate long-term stability up-to 6.9 h,9.8 h and 13.2 h.More sensitive sensors could make it easier to monitor an individual’s physiology.