Controllable Preparation And Biosensing Study Of AuNP-PDMS Composite Films

With the development of science and technology,the fourth industrial revolution has arrived,and significantly improved the quality of human life.In the new era of technology,sensing technology has been greatly improved.Biosensing as a significant sensing technology has been rapidly developed in recent years,especially.Biomedicine,information science and life science have gradually realized intelligent connection.On the basis of the interdisciplinary,biomedical detection requires to upgrade biosensing technology.As the core component of biosensor,the sensitive element is expected higher sensitivity,reliability,accuracy and integration.Due to synergism and high biocompatibility,the composite materials of gold nanoparticles(AuNPs)and polydimethylsiloxane(PDMS)have been widely applied in the field of biosensors.Recently,surface stress biosensor has increasingly attracted attention owing to its easy integration and preparation.High-performance AuNP-PDMS composite film will play an important role in improving the performance of surface stress biosensors,exhibiting great application prospects in disease prevention,food safety,toxicity testing.However,the AuNP-PDMS composite film currently suffers from poor stability and specificity,limiting its application in biosensing.Based on the controllable preparation method,the stability of the AuNP-PDMS composite film was improved in this dissertation.The surface stress biosensor based on the AuNP-PDMS composite film was prepared and optimized to realize the detection of glucose,E.coli O157:H7,and BSA.The surface functional technology and signal amplification method of the biosensor were designed to improve the sensitivity,specificity and reliability of the biological detection.The detection limit of the biosensor was gradually reduced as well.The major research contents were as follows:1.The controllable preparation method and electrical properties of AuNP-PDMS composite films were studied.The results show that the growth of AuNPs in PDMS can be effectively controlled by adjusting the reduction time,thickness and mass ratio of PDMS.The 2.00-?m-thickness AuNPs layer containing gold quantum dots with a diameter of 2.01±0.51 nm is formed in the internal of PDMS,improving the stability of the composite film.The AuNPs layer have a shortest distance of 2.90±0.47?m from the PDMS surface,which is independent from reduction,a thickness and mass ratio of PDMS.The optimized preparation conditions of composite film are 18-h reduction time,26-?m thickness,and 10:1mass ratio of PDMS.Especially,the film exhibits the quantum tunneling effect,and is capable of sensing micro strain,and can be applied to surface stress biosensor due to its sensitivity to micro strain.2.Based on physical adsorption,the flexible film surface stress biosensors were designed and fabricated with the single-layer AuNP-PDMS composite film The biosensor was optimized structure and modified with 16-MHA to enhance its biological sensing performance.Based on the principle of surface stress generated by electrostatic adsorption and hydrophobic adsorption,the biosensors for glucose,E.coli O157:H7 and BSA were studied.With the surface stress generation principle by electrostatic adsorption and hydrophobic adsorption,the biosensing characteristics of AuNP-PDMS composite film for glucose,E.coli O157:H7 and BSA were studied.The results show that the circular through-hole with 4 mm diameter is the optimal structure of the biosensor.The biosensor exhibits linear responses to the glucose,the logarithm of E.coli concentration and BSA.The linear ranges are 0-30 mmol/L,10~3-10~7?CFU/mL and 15-100?g/mL,respectively.Correspondingly,the limits of detection(LOD)are 1.25 mmol/L,10~3 CFU/mL and 2.06?g/mL.3.Based on the specificity problem of the biosensor in the above work,the specificity and reliability of surface stress biosensor were improved by modifying the glucose oxidase(GOx),E.coli antibody and BSA antibody.The glucose,E.coli O157:H7 and BSA were specifically detected respectively.The results show that the relative resistance changes of the biosensor linearly increase with glucose concentration,the logarithm of E.coli concentration and BSA concentration.The LODs are reduced to 0.607 mmol/L,43 CFU/mL and 1.14?g/mL,respectively.Compared with the physical adsorption method,the detection limits is reduced by one time,one hundred times and one time.Furthermore,the biosensor shows high repeatability and stability for the three biomolecular detection.In addition,the sensing mechanism and principle of the conversion of biological signal,force signal and electrical signal are clarified,providing a theoretical basis for the application of the surface stress biosensor in medical detection.4.The sandwich-type composite film of AuNP-PDMS-AuNP was designed and fabricated to improve the anti-interference of surface stress biosensor.Based on modification of enzyme and antibody,the biosensing performance of sandwich-type composite membrane for glucose and BSA are studied with direct assay.The results show that the LODs of the biosensor to glucose and BSA are further reduced to 0.021 mmol/L and 0.261?g/mL.Compared with the specific detection methods of single-layer biosensor,the LODs are both reduced by an order of magnitude.Finally,the dissertation proposed sandwich assay for BSA detection to amplify the surface stress.The BSA secondary antibody was introduced to improve the sensitivity of the biosensor.Compared with the direct assay,the LOD is reduced to 0.035?g/mL.