Construction And Application Of Biosensor System Based On Core-shell Composite Nanomaterials

Core@shell nanomaterials are a type of composite composed of a core(internal material)and a shell(outer layer).Usually the composition or structure of the core and the shell are different,and their shape,particle and pore size can be adjusted according to a specific environment(such as in vitro).Or in vivo,acidic or alkaline and purpose(such as small molecule or macromolecule capture)for design and selection,which endows core@shell nanomaterials with high specific surface area,excellent biocompatibility and targeting of detected molecules.Making it play a key role in the construction of photoelectric biosensors.With the development of interdisciplinary research on the integration of biomedicine and nanotechnology,many nano-optical and electrochemical biosensors have emerged.Among them,photoelectric biosensors combined with core@shell nanomaterials have been widely explored and successfully applied to the detection of biochemical molecules,especially the detection of small molecules related to human life and health,and the detection of disease metabolites has made remarkable progress.Based on this,we mainly designed and synthesized a series of core@shell nanomaterials,and successfully constructed fluorescence,colorimetric and electrochemical biosensing systems.The main results are summarized as follows:The excellent performance of a biosensor generally depends on the high signal-to-noise ratio,and the superquencher plays a dominant role in fluorescent sensors.Novel nanoquenchers exhibited high quenching efficiency in various fluorescent assays of biological/chemical molecules.Here,we developed a novel nano-biosensor using Fe₃O₄@C yolk-shell nanoparticles(YSNPs)and studied their quenching effect.We found Fe₃O₄@C YSNP was a superquencher and exhibited an ultrastrong quenching ability,up to almost 100%quenching efficiency,toward fluorophores.Also,Fe₃O₄@C YSNPs possessed the most superior fluorescence restoration efficiency,due to biomolecular recognition event,compared to the other nanoquenchers,including bare Fe₃O₄ NPs,graphene oxide(GO),and single-wall carbon nanotubes(SWCNTs).On the basis of that,a fluorescent sensing platform for potassium-ion(K⁺)analysis with guanine(G)-rich oligonucleotides was designed.As a result,Fe₃O₄@C YSNP-based fluorescent sensors demonstrated excellent performance,with an ultrahigh sensitivity of a detection limit as low as 1.3?M,as well as a wide dynamic range from 50?M to 10 m M.The proposed method is fast,simple,and cost-effective,suggesting the great potential for practical applications in biomedical detection and clinical diagnosis.we have developed a simple and facile method to synthesize core@shell nanostructured Fe₃O₄@C nanotubes(NTs)as a multifunctional biosensing platform for the label-free colorimetric detection of H₂O₂ and glucose.It was demonstrated that Fe₃O₄@C NTs retained the magnetic properties that can be used for separation and concentration.Importantly,the Fe₃O₄@C NTs exhibited dual activity of oxidase-like and peroxidase-like that could quickly catalyze the enzyme substrate in the presence of H₂O₂ and produce a blue color.Compared to other similar ferric oxide-based NPs with different structures,Fe₃O₄@C NTs exhibited greatly enhanced catalytic activities due to their unique structural features.Moreover,steady-state kinetics indicated the catalytic behaviors in agreement with the classic Michaelis–Menten models.Taking advantage of the high catalytic activity,Fe₃O₄@C NTs were employed as novel peroxidase mimetics for label-free,rapid,sensitive,and specific colorimetric sensing of H₂O₂ and glucose,suggesting that Fe₃O₄@C NTs have the potential for construction of portable sensors in the application of point-of-care(POC)diagnosis and on-site tests.In this work,WS₂@Au quantum dots(QDs)were prepared by a facile in situ reduction method and further used as an efficient substrate for studying the immobilization of the redox enzyme and their sensing performance.Using glucose oxidase(GOx)as a model,a novel direct electrochemistry analysis of glucose was successfully realized at WS₂@Au QDs nanocomposite modified glassy carbon electrode.The fabricated nanocomposite was characterized by transmission electron microscopy,energy-dispersive X-ray spectroscopy,and UV-vis spectroscopy.The direct electrochemistry and electrocatalysis of GOx on WS₂@Au QDs modified electrode were examined by cyclic voltammetry.The GOx showed a pair of well-defined and quasi-reversible redox peaks in p H 7.0 phosphate buffer solution,revealing that the high bioactivity of GOx was maintained due to the excellent biocompatibility of the nanocomposite.The heterogeneous electron transfer rate constant was calculated to be 2.25 s^-1,indicating a fast and direct electron transfer of GOx at the nanocomposite modified electrode.Studies on the response for glucose showed high stability,sensitivity,and selectivity,with a broad linear range from 5 to400?M and a low detection limit of 1.5?M.These results suggest that the WS₂@Au QDs nanocomposite has potential applications in the preparation of other biosensors.