Study On Novel Electrochemiluminescence Biosensor Based On Photonic Crystals

Electrochemiluminescence（ECL）is a chemiluminescence excited by electricity,which has the advantages of low detection limit and controllable voltage.Although the Roche immunoanalyzer with ECL technology as the core has been applied in various hospitals,there are still many problems in ECL biosensors.For example:（1）The detection target of ECL biosensor is single.At present,bipolar electrode wireless technology is often introduced into ECL,and a bipolar electrode-electrochemiluminescence（BPE-ECL）solid-phase biochip based on position coding is constructed to detect various targets.However,BPE-ECL solid-phase biochip can’t be used in micro/nano field because it needs at least several thousand volts to induce electrochemical reaction on micro/nano bipolar electrode.Compared with solid biochip,liquid biochip has higher reaction efficiency and better reproducibility.And the structure color encoding of photonic crystals is a common code in liquid biochip.Therefore,the liquid phase biochip based on the combination of photonic crystal structure color coding and BPE-ECL can detect a variety of targets more quickly and accurately by introducing the photonic crystal structure into BPE-ECL.（2）The sensitivity of ECL biosensor is low.Photonic crystal structure not only has excellent structural color coding characteristics,but also has good light enhancement effect.Solid-state electrodes modified by photonic crystal nanofilms can effectively amplify ECL signals and improve the sensitivity of ECL biosensors.（3）The driving potential of ECL biosensor is high.The design of ECL electrode with delicate structure is a common strategy to realize low triggering potential ECL.The low trigger potential ECL sensor designed on the photonic crystal modified solid electrode can not only reduce the electrochemical excitation potential,but also amplify the electrochemical luminescence signal.In view of the above problems and ideas,the specific research contents of this paper are as follows:（1）A microchannel was set up in an ordinary bipolar electrode electrochemical cell to explore the influence of the size of the microchannel on the driving voltage of the bipolar electrode.Firstly,carbon nanotube（CNTs）microspheres with good conductivity,uniform particle size and stable structure were prepared by droplet microfluidic technology.Then,taking CNTs microspheres as bipolar electrodes,the effects of the width and length of microchannel on the driving voltage of bipolar electrodes were investigated by simulation and BPE-ECL experiments.By setting up a microchannel in a bipolar electrode electrochemical cell,the electrochemical reactions on micro/nano bipolar electrodes can be excited with low driving voltage.（2）Using conductive SiO2/CNTs amorphous photonic beads as encoding microcarriers and bipolar electrodes,a multi-biosensor combined with structural color coding and BPE-ECL imaging was constructed to detect three biomarkers of ovarian cancer（CA125,CEA,AFP）.Firstly,SiO2/CNTs amorphous photonic beads with good conductivity and stable structural color were prepared by droplet microfluidic technology.Then,the structural color of SiO2/CNTs photonic beads was used to distinguish and identify three biomarkers of ovarian cancer,and Cd Te QDs was used as the ECL marker signal of ovarian cancer antibodies.After modifying different ovarian cancer primary antibodies with SiO2/CNTs photonic beads,ovarian cancer antigens in solution were captured by specific immune response,and then combined with Cd Te QDs labeled ovarian cancer secondary antibodies to form conductive composite microspheres;Subsequently,the conductive composite microspheres were placed in a bipolar electrode electrochemical cell with microchannels,and the BPE-ECL reaction on the conductive composite microspheres was remotely induced by an applied electric field to achieve multivariate detection of cancer markers.In this work,structural color coding is combined with BPE-ECL imaging for the first time,which lays the foundation for electrochemiluminescence coding technology.（3）ITO electrode modified with SiO2 photonic crystal nanofilms was used as the working electrode of ECL system to construct an enhanced near-infrared ECL biosensor for highly sensitive detection of fever with thrombocytopenia syndrome virus（SFTSV）.SiO2 photonic crystal structure has excellent light scattering effect,which significantly increases the photon flux in luminescent molecules and enhances the excitation of ECL molecules by re-radiation dipole electromagnetic field.Using Cd Te@Cd S QDs as ECL emitter,ECL emitter was coupled to photonic crystal through immune reaction.The ECL intensity of the constructed SiO2photonic crystal can be improved by about 7 times.The detection limit of SFTSV with the near infrared ECL sensor was 0.0014fg/m L.The successful construction of photonic crystal-based ECL sensor provides an effective,universal and inexpensive signal amplification strategy for ECL technology.（4）Single-layer polystyrene photonic crystal structure was self-assembled on ITO electrode,and gold nanoparticles were electrodeposited in the photonic crystal gap to prepare GPCs electrode.The ECL biosensor based on GPCs electrode can not only amplify the ECL signal,but also stimulate the electrochemical reaction at low oxidation potential.With GPCs electrode as the platform for anchoring antigen,self-made Ru（bpy）3²⁺-COOH was the ECL signal to label antibody.The antibody labeled with Ru（bpy）3²⁺-COOH was bound to the antigen on polystyrene through specific immune reaction,so that Ru（bpy）3²⁺was far away from the surface of gold nanoparticles and cannot be directly oxidized.Thus,ECL emission can only be initiated by electrochemical oxidation of tripropylamine（TPr A）.The ECL emission potential caused by TPr A oxidation（0.95V vs.SCE）was about 300 m V lower than that caused by Ru（bpy）3²⁺oxidation（1.25V vs.SCE）.In addition,the structure of polystyrene-like photonic crystal has light enhancement effect,and the enhancement amplitude of ECL signal with low trigger potential is about 5 times.Subsequently,a biosensor with a detection limit of 0.075pg/m L was successfully constructed on the GPCs electrode with tetracycline antibiotics as the model.The special structure of GPCs electrode makes it possible to enhance the light signal and reduce the trigger potential at the same time,which expands the application of ECL in the analysis field.