Split-type Biosensors Constructed By Superparamagnetic Nanomaterials For Cancer Biomarkers

Cancer has always been a major threat to human health.It is a type of disease with a very high fatality rate.Real-time monitoring of cancer disease biomarkers has always been of great significance in the early diagnosis of cancer,drug efficacy monitoring,postoperative judgment,and prevention of recurrence.However,the almost all cancer markers are low-abundance,and its detection in real samples will be interfered by other biological molecules.Some traditional detection methods are costly and unfriendly to the environment.Also,the sensitivity and selectivity of the new biosensing strategies developed in recent years for detecting cancer disease markers need to be improved.In this work,superparamagnetic Fe₃O₄@SiO₂core-shell structures,Cd Te quantum dots,and gold nanobipyramids were prepared and used to construct robust cancer disease marker split-type sensors that can meet the requirements of detectionfor mi R-122,adenosine,and CEA.The main tasks are as follows:(1)First,Fe₃O₄@SiO₂core-shell structure nanomaterials and Cd Te quantum dots were prepared.Following the amidation reaction of EDC/NHS was selected to modify the certain DNA on the surface of nanomaterials.Meanwhile,scaffold,output and by-product DNAs were assembled to form a three-strand complex structure.With the initiation of mi R-122,fuel DNA interacts with the three-strand complex to release output DNA.At this time,the magnetic beads modified with probe DNA were introduced into the system to capture output DNA,resulting in the formation of Fe₃O₄@SiO₂-probe DNA-output DNA structures.With magnetic extraction of the composite structure,and it was scattered into another system to specifically capture Cd Te QDs-signal DNA structure,then theresulting Fe₃O₄@SiO₂-probe DNA-output DNA-signal DNA-Cd Te QDs composite structure was separated by magnetic force.The more output DNA released,the more Cd Te QDs-signal DNA structure will be captured,and the photoelectrochemical signal will decrease gradually.The stability and sensitivity of the biosensor were improved due to the utilization of the entropy-driven signal amplification system with the multi-chain composite structure.The application of the superparamagnetic Fe₃O₄@SiO₂core-shell structures allows the sensor to eliminate the lengthy steps of electrode layer-by-layer assembly.The photoelectrochemical signal readout only by Cd Te QDs-signal DNAs effectively eliminates the interference of other substances in the real samples,and remarkably improves the stability of the sensor.(2)First,Fe₃O₄@SiO₂core-shell nanostructures and gold nanobipyramid nanomaterials were prepared.Following,Au-S bonds and EDC/NHS coupling reaction strategies were chosen to modify the certain DNAs on the surface of nanomaterials.The DNA walking machine was constructed by the SiO₂shell modified the specific DNAs.When adenosine is present,the walker DNA will be triggered.Driven by fuel DNA,the DNA walking machine on the surface of SiO₂will continuously release the Au-NBPs-c DNA composite structure.The more adenosine in the system,the more Au-NBPs-c DNA composite structure will be released.And the photothermal effect of the solution will be stronger after the magnetic extraction.The temperature of the solution will increase under the irradiation of the 808 nm laser light source.The higher the photothermal effect will be achieved with the concentration of target increasing.Therefore,the adenosine photothermal sensor was constructed based on this working mechanism.The DNA walking machine coupled with entropy-driven signal amplification technology effectively improves the sensitivity of the photothermal biosensor.Additionally,this sensing strategy eliminates the complicated electrode layer-by-layer assembly process of the traditional photoelectrochemical sensing strategy,and directly reads out the change of temperature signal from the solution,it simplifies the operation steps of the sensor and shortens the detection time.(3)First,Fe₃O₄@SiO₂core-shell nanostructures and gold nanobipyramid nanomaterials were prepared.Then,Au-S bonds strategy was utilized to modify small rhodanine molecules on the surface of gold nanobipyramid.Meanwhile,the surface of SiO₂was modified with the capture DNA using EDC/NHS coupling reaction.The introduction of the target CEA into the entropy-driven DNA system leads to the release a large amount of output DNA.At this time,the Fe₃O₄@SiO₂-capture DNA composite structure was introduced into the biological signal amplification system to specifically capture output DNA with a large amount of thymine structures.The generated Fe₃O₄@SiO₂-capture DNA-output DNA structures were separated from the signal amplification system by magnetic attraction,and then,they were introduced into a certain concentration of mercury ion solution.Thanks to the formation of“T-Hg²⁺-T”structures,the resulting Fe₃O₄@SiO₂-Capture DNA-Output DNA structures combined with Hg²⁺ions were extracted with magnetic force.Then the gold nanobipyramids modified with rhodanine were dispersed into the remaining mercury ion solution.Rhodanine can effectively fix mercury ions,making the LSPR peak of the gold nanobipyramids red shift,and then the color change of the solution.At the same time,the absorbance of the gold nanobipyramid at 808 nm decreases,resulting in the temperature decrease therefore.This strategy is based on the combination ofentropy-driven signal amplification technology and split-type sensing strategy,which ensures the sensitivity and selectivity of the dual-mode sensor.This unique signal readout of the two modes can make the detection result reliable.In addition,this dual-mode sensor has low dependence on the instrument.The photothermal signal sensor only relies on the light source and the infrared temperature camera,and the colorimetric sensing strategy does not require any instruments.It is convenient to operate and easy to carry.