Functionalized Nanomaterials-based Electrochemiluminescent Systems And The Applications In Bioanalysis

Electrochemiluminescence?ECL?,which combined electrochemical technology and chemiluminescent technology,has been widely applied in the fields of clinical diagnosis,food safety supervision and environmental pollution monitoring due to its high controllability and sensitivity.It is well-known that an efficient coreactant could greatly enhance the ECL siganl of the emitter.Therefore,in order to improve the sensitivity of biosensors,one of the most important ways is to develop an efficient ECL system.Nanomaterials with high surface area and excellent surface activity could effectively increase the reactivity of electrochemical interface for further increasing the ECL performance.Moreover,ECL nanomaterials?e.g.,quantum dots and metal nanoclusters?with excellent ECL properties have been extensively applied in ECL bioassay.Herein,nanomaterials were employed to enhance reacted efficiency of coreactants and develop low-cost,biocompatible and high-performance ECL emitters to construct the sensitive ECL biosensors for the detection of proteins and small biomolecules.The detail contents are divided into the following aspects: 1.A highly sensitive electrochemiluminescence immunosensor based on gold nanoparticles functionalized magnetic graphene as nanocarriersCarbon nanomaterials?e.g.,graphene,fullerenes and carbon nanotubes?are widely used as nanocarriers in biosensors due to their large specific surface area,excellent conductivity and good biocompatibility.Commonly,carbon nanomaterials are functionalized to further increase the active sites on the surface.In this work,gold nanoparticles functionalized magnetic Fe₃O₄/reduced graphene?Au@Fe₃O₄-rGO?nanocomposites were synthesized via a one-pot method.Due to the advantages of larger specific surface area,more active sites and easier separation,the nanocomposites could notably enhance the loading of biological molecules.In addition,bi-Arg which acted as an efficient coreactant of ruthenium(Ru?bpy?₃²⁺)was introduced to improve the sensitivity of the biosensor.Based on the novel Ru?bpy?₃²⁺/bi-Arg ECL system and Au@Fe₃O₄-rGO nanocomposites,a highly sensitive immunosensor was proposed to quantitatively analyze the apurinic/apyrimidinic endonuclease 1?APE-1?.The developed biosensor showed a good linear response to APE-1 range from 1.0 fg m L-1 to 5.0 pg m L-1 with the limit of detection of 0.3 fg m L-1.2.Au nanoparticles decorated C60 nanoparticle-based label-free electrochemiluminesence aptasensor via a novel “on-off-on” switch systemIn this work,C60 nanoparticles?nano-C60?were synthesized via solvent exchange method.Then,the nano-C60 was decorated with bovine serum albumin?BSA?via hydrophobic interaction for the surface of nano-C60 with-NH₂ and –SH.Next,Au nanoparticles were in situ generated on the surface of BSA decorated nano-C60 via direct reduction of chlorauric acid.Interestingly,Au@nano-C60 nanocomposites act as not only an ideal material for electrode modification due to their the advantages of large surface area,large surface active sites and easy film formation,but also an effective enhancer of S₂O₈^2--O₂ ECL system.Based on the efficient enhancement of Au@nano-C60 with coreactant poly-histidine and gold nanoparticles,a label-free ECL aptasensor was constructed via a novel “on-off-on” switch system for sensitive detection of kanamycin.The prepared aptasensor showed a linear response to kanamycin range from 0.15 nmol L-1 to 170 mmol L-1 with the limit of detection low to 45 pmol L-1.3.Based on triple quenching of a novel self-enhanced Ru???complex by hemin/G-quadruplex DNAzymes for “on-off” ECL aptasenor constructionPerylene tetracarboxylic acid?PTCA?is a kind of organic semiconductor nanomaterials with unique electrical and optical properties.In this work,self-enhanced ruthenium???complex was prepared by covalently crosslinking polyethyleneimine?PEI?and tris?2,2'-bipyridine?ruthenium derivative with PTCA.Then,the working electrode was modified with the self-enhanced ruthenium???complex to obtain a strong initial ECL signal.Additionally,the nicotinamide adenine dinucleotide?NADH?was introduced to further enhance the ECL signal for the increase of the sensitivity of the biosensor.Based on the triple ECL quenching of the self-enhanced ruthenium???complexes by hemin/G-quadruplex DNAzymes,the highly sensitive “on-off” thrombin aptasensor was developed with a wide linear detection range from 1.0 × 10-14 mol L-1 to 1.0 × 10-10 mol L-1 with the limit of detection low to the femtomolar level.4.Cu nanoclusters: novel electrochemiluminescence emitters for bioanalysisCd-based semiconductor quantum dots?QDs?with size-tunable luminescence and high quantum yield have become the most promising ECL emitters.However,their unavoidable biotoxicity limited their applications in bioassays.Therefore,to maintain a benign environment,developing environmentally friendly and low-toxicity or nontoxic ECL emitters for bioassay has attracted explosive attention.Cu nanoclusters?CuNCs?,emerged as a kind of novel photoluminescent and catalytic nanomaterials,have gained growing popularity in various areas such as sensing,biolabeling and catalysis.However,the ECL behavior of CuNCs has never been reported in previous works.Here,anodic ECL emission of CuNCs was observed with the efficient coreactant of hydrazine?HZ?.Based on the effective quenching effect of the CuNCs/HZ ECL system by dopamine,a highly sensitive “signal-off” sensing platform was developed for the determination of dopamine.As a result,this proposed method possesses high selectivity,good stability,and excellent sensitivity for dopamine detection with the limit of detection down to 3.5 × 10-13 mol L-1.This indicated that CuNCs showed potential applications in ECL bioanalysis as a new type of low-cost and superior luminophore candidates.5.Molybdenum disulfide quantum dots-emerged electrochemiluminescence for highly sensitive aptasensor construction with target-cycling synchronized rolling circle amplification strategyThe emerging molybdenum disulfide quantum dots?MoS₂ QDs?,a class of unique graphene-analogous transition-metal dichalcogenide nanomaterial,not only possess the excellent properties of ?-VI QDs?e.g.,size-tunable luminescence and high quantum yield?,but also present preeminent biocompatibility due to their heavy-metal-free characteristics.Herein,the nontoxic and economical MoS₂ QDs prepared by chemical exfoliation from the bulk MoS₂ were first investigated as new ECL emitters,and then the possible luminescent mechanism of MoS₂ QDs was studied using ECL-potential curves and differential pulse voltammetry?DPV?methods in detail.With MoS₂ QDs as the ECL emitters and triethylamine?TEA?as the efficient coreactant,a practical and label-free aptasensor for lipopolysaccharide?LPS?detection was constructed based on aptamer recognition-driven target-cycling synchronized rolling circle amplification.The developed assay for LPS detection demonstrated a wide linear range of 0.1 fg m L-1 to 50 ng m L-1 with the limit of detection down to 0.07 fg m L-1.It is worth mentioning that MoS₂ QDs with stable ECL emission exhibited a great application potential in ECL bioanalysis and imaging as a new type of excellent emitter candidates.