An Electrochemiluminescence Detection Platform Based On A Nanomaterial Scale-up Strategy

Nanomaterials-based electrochemical chemiluminescence(ECL)biosensors are the detection systems that combine the specific recognition capabilities of biomolecules with the nanomaterials-based ECL test methods,which have attracted wide attention due to their strong sensitivity and low background signals.The introduction of nanomaterials improves the ECL performance and thus enhances the sensitivity of the sensor.The amplification strategy based on nanomaterials for ECL is crucial for improving the performance of the sensor.The following methods are the main ones:Improving the properties of nanomaterials or modifying them with functional groups,improving the luminous efficiency of the luminophor;Increasing the electric conductivity and the active surface area to accelerate the ECL electron transfer reaction,improving the yield of the excited state of ECL;Increasing the loading number of signal molecules by the connection of DNA and the enrichment of nanomaterial.In this thesis,the above nanomaterials-based amplification strategies of ECL sensors were constructed.Based on the regulation of co-reactants H2O2 and K2S2O8 and the construction of C-Ag+-C structure,the sensitive and selective ECL sensors were build to detect p53 gene,dopamine(DA)and silver ions(Ag+),respectively.1.In comparison with graphene quantum dots(GQDs),hydrazide-modified GQDs(HM-SGQDs)possess abundant luminol-like units,thus greatly enhancing the ECL intensity.On the other hand,luminol-involved ECL system typically need the participation of H2O2 as coreactant,while hemin/G-quadruplex(hGQ)DNAzyme could efficiently catalyze the decomposition of H2O2.Accordingly,taking p53 gene as a model,a novel ECL DNA biosensor was developed based on HM-SGQDs and hGQ DNAzyme.In the presence of target DNA,the guanine(G)-rich fragment that is"locked" in the probe DNA with the hairpin structure is released from the doublestranded structure.With the involvement of K+and hemin,the G-rich DNA sequences are assembled into hGQ DNAzyme,which cause the decomposition of H2O2,leading to the diminished ECL signals.As a result,target DNA was quantified in a "signal-off"manner sensitively and selectively.Meanwhile,discrimination of single-base mismatch was also achieved with the proposed ECL biosensor,suggesting potential in applications of nucleic acid-related clinical diagnosis.2.A simple and green method is employed to in situ growth gold nanoparticles on the surface of WS2 nanosheets.Besides hindering the stack of nanosheets,integration of Au NPs enhances electron transfer between nanosheets owing to their excellent electronic conductivity.The defects of prepared Au-WS2 nanocomposites may accelerate electron transfer and facilitate the concentration of dissolved oxygen.As a result,Au-WS2 nanocomposites-enhanced ECL is observed for the first time,and is further used to fabricate a non-destructive and label-free analytical interface.Au-WS2 nanocomposites significantly increase the ECL intensity of S2O82-and O2 system,while the coreactant S2O82-can be consumed by DA,which causes the quenching of ECL signals.Different from typical ECL sensor,in which nanomaterials are used to participate in ECL reactions,Au-WS2 in this work is not destructed during the DA detection.DA can be quantified continuously at least six times after one fabrication.In addition,the proposed ECL interface can accurately monitor the release of DA from PC 12 cells manipulated with K+and nifidipine,indicating great potential for surveying DA-related investigations.3.Based on the high charge transfer efficiency of the cytosine-Ag+-cytosine(CAg+-C)structure,an ECL biosensor for sensitive,simple and label-free detection of Ag+is constructed utilizing the gold nanoparticle-based signal amplification strategy.The probe DNA is attached to the surface of the gold electrode by means of an Au-S bond.The uniform-sized Au NPs are connected with the link DNA and then linked to the electrode surface by the hybridization of link DNA with probe DNA.If a certain concentration of Ag+is added during the hybridization process,due to the stable formation of the C-Ag+-C structure,a large number of Au NPs are introduced and the electron transfer efficiency is improved.C-Ag+-C exhibit the same significant charge transfer efficiency,the gathering Au NPs further promote the formation of C-Ag+-C and accelerate the electron transport in the ECL process.The ECL intensity of this designed biosensor increases with the addition of Ag+,and is linear with the logarithm of C(Ag+),showing good sensitivity and potential in practical application.