Functional Nanomaterials-based High-Performance Biosensing Devices And Their Applications In Biomolecular Detections

With the significantly increasing number of deaths caused by late diagnosis of the patients worldwide,rapidly and sensitively early detection of fatal diseases has attracted more and more attentions.Biosensors show huge potential applications in clinical diagnosis and biomedical researches due to their advantages of high-throughput,fast,efficient,sensitive,miniaturized and easy to automation.Currently,in medical field,biosensors can be successfully used to monitor many important biomolecules such as the blood glucose levels of diabetic patients and uric acid for the gout arthritis.However,clinical diagnosis still relies on hospital diagnostic platform with large and expensive equipment.Therefore,the development of biosensors still has some limitations,especially for the local rapid point-of-care testing?POCT?.On the other hand,the biosensors for biomolecules detection are mostly based on enzyme,but the enzyme is expensive and its fixation is complex.In addition,its activity is susceptible to conditions such as pH and temperature,which result in a higher cost and poor stability of these biosensors.The emergence of nanotechnology provides a new direction for the development of high-performance biosensors.Due to their unique optical,electrochemical,catalytic and good biocompatible properties,nanomaterials have been used to develop various detection platforms with high sensitivity and selectivity.Nevertheless,most of the reported nanomaterials-based biosensors still remain at research or laboratory stage,and still experience many issues/problems to be solved for clinical diagnosis such as POCT applications.Therefore,development of novel,protable,and inexpensive functional nanomaterials-based biosensing devices are important,attractive but still very challenging.In this thesis work,by the use of the rapid developed advanced nanoscience and nanoengineering,new and universally applicable fabrication technology of biosensing devices are developed.More importantly,a number of functional nanomaterials-based biosensing devices are developed,and their sensing and enhancement mechanisms for high-performance including high selectivity and high sensitivity are also studied.The main research contents are as follows:1.Alkaline phosphatase?ALP?in human serum is mainly from the liver and bones,in which when the organ is sick or infected,the ALP activity in serum will significantly increase.Therefore,determination of the activity of ALP can be used as an adjunctive diagnostic indicator for some diseases.However,the ALP detection strips available on the market is few and its detection process is tedious and complicated.In this work,AuNPs@Cystine-tyrosine-P?AuNPs@Cys-tyr-p?were successfully synthesized by two-step coupling,and a disposable and portable ALP strip was developed based on AuNPs@Cys-tyr-p,which could selectively sense ALP in human serum with a linear dynamic range of 0.1-150 U/L within 10 min,and can be successfully used to detect ALP in human serum.The results prove that the main detection mechanism of the strip is based on the dephosphorylation of ALP,which is able to cut the phosphate groups of AuNPs@Cys-tyr-p against the aggregation of AuNPs@Cys-tyr-p,and thus ALP is indirectly detected.In more detail,the AuNPs@Cys-tyr-p can be specifically captured by the antiphosphate-tyrosine antibodies that immobilized in testing zone of the sensing strip.AuNPs@Cys-tyr-p is in fact bifunctional,which can be used as a carrier of O-PhosphoL-tyrosine to specifically react with ALP,while its aggregation in the test area can generate color change for signal acquisition.The study reveals that the specificity and sensitivity of the detection can be greatly improved by the unique reaction mechanism between the functionalized AuNPs and ALP,and thus a rapid and accurate determination of ALP activity can be realized.2.Abnormal uric acid?UA?concentration in human serum can lead to diseases like gout and hyperuricemia,and UA is an important clinical diagnostic marker.Currently,most of the UA sensors are based on uricase,but the use of enzymes limits their application in daily life.In this work,a serrated polyaniline?PANI?nanoarray was coated and carbonized on CNTs to obtain nitrogen doped carbon nanotubes?N-doped CNTs?.Further,Prussian Blue?PB?nanoparticles were embedded in the serrated structure of N-doped CNTs to form a PB/N-doped CNTs nanocomposite.The modified PB/N-doped CNTs on printed electrodes are used to construct a high-performance nonenzymatic UA sensing device,which is able to sense the UA in human serum.Analysis of experiment results and combined DFT calculation reveal that the molecular structure of UA can well match with PB lattice structure to enable UA molecules specifically adsorbed on the surface of PB leading to fast interfacial electron transfer from the electrochemical detection reaction for high specificity and high sensitivity of detection of UA,a negative potential?-0.5 V?to mediate the detection reaction can avoid the interference coexisting in serum.The stability of the sensing stripe is greatly improved by the increased chemical and physical stability of the composite materials,which mainly due to the embedding growth of PB nanoparticles.The discovered molecularly match sensing mechanism vividly demonstrates the essential influence of the interfacial characteristics of the nanomaterial on the specific detection of biomolecules,which provides universal theoretical guidance for the future design and synthesis of highly efficient nanomaterials to construct high-performance biosensors.3.Abnormal dopamine?DA?level can lead to many diseases such as Parkinson's,Alzheimer's and schizophrenia.Therefore,detection of DA levels in the brain,blood,urine and tissues has important significance for physiological functions and clinical diagnosis.Most of the traditional DA sensors suffer from low sensitivity,poor selectivity and high expense.In this study,N-doped carbon nanorods?N-doped CNRs?were synthesized by coating a layer of PANI on the surface of Shewanella putrefaciens CN32followed by high-temperature carbonization.Then,a high performance DA sensor was developed by modifying printed electrodes with AuNPs/N-doped CNRs₉₀₀.Further,the study of the catalytic sensing mechanism of AuNPs/N-doped CNRs₉₀₀ toward DA is further investigated.The N-doped CNRs₉₀₀ is negatively charged in neutral aqueous solutions due to the presence of N atom,which can reject negatively charged ascorbic acid?AA?and UA and cause electrostatic interactions with the positively charged DA to greatly increase the selectivity for DA detection.The adsorption of N-doped CNRs₉₀₀toward DA is mainly due to?-?interaction between the N-doped CNRs₉₀₀ and benzene ring of DA,while the hydrogen bonds can form between the nitrogen atoms in N-doped CNRs₉₀₀ and hydroxyl or amine group in DA.The large surface area and pore volume of N-doped CNRs₉₀₀ is able to absorb a large amount of DA.In addition,the active center of AuNPs can make DA to lose electrons quickly,thus achieving highly sensitive detection of DA.This study demonstrates that nanomaterials can be effectively modified to offer unique chemistry for highly sensitive and selective detection of target molecules.4.Cell as a basic functional unit in human body could offer crucial biological and medical information by its based biochemical analysis.Currently,cell-based assays strongly rely on 2D cell culture systems,which can not real-time monitor biochemical and physiological functions of living cells during their growth.Microfabrication can construct complicated scaffolds for 3D cell cultures,but this approach usually requires large instruments.In this study,a paper-based electrochemical sensing device containing electrode and cell culture system was developed by combination of 3D paper fiber with a laminated film.The electrochemical sensor modified with?Fe,Mn?₃?PO₄?₂/N-doped CNRs has a wide linear detection range and a low detection limit.The cell directly grown on paper-based sensing strip greatly shortens the distance to access the active sites,thus delivering high sensitivity for in situ detection of hydrogen oxide?H₂O₂?released from the cells grown in 3D paper fiber.In this work,tailoring the components ratio of?Fe,Mn?₃?PO₄?₂ can significantly improve the detection sensitivity.Further,as a support of sensing materials,the N-doped CNRs renders a larger surface area and pore volume for loading a large amount of sensing active?Fe,Mn?₃?PO₄?₂ nanoparticles to deliver high catalytic performance toward H₂O₂ reduction.In brief,the modification of functional groups on nanomaterial can offer great sensitivity and high selectivity for biomolecular detections,which mainly due to the unique functions of the modified functional groups for the high selectivity and large porous inner surface area to be attached for the high sensitivity,thus demonstrating a universal detection scheme to design a highly sensitive and selective biosensor.