Study On The High Sensitivity Of Surface Acoustic Wave Biosensor

Among the clinical detection methods,the disadvantages such as high costs,long detection time,complex operation always exist in the traditional methods.Therefore,biosensors are getting more and more attention owing to characteristics of low costs,ease of mass production,label-free detection,short detection time and ease of operation.In recent years,SAW(surface acoustic wave,SH-SAW)-based biosensors stand out from the biosensors due to the advantages of high sensitivity,quick response and simple production process.To realize the detection of nucleic acid,polysaccharide and protein,the fabrication process,performances improvement and the preparation of the material in the sensitive area,the bio-functionalization on the surface of the sensitive layer of the SAW-based biosensor were proposed in this study,which could make the SAW-based biosensor have the ability of effective detection of the biological samples.①SH-SAW biosensor was applied for the detection of the Pseudomonas aeruginosa nucleic acid.The SH-SAW biosensor was fabricated by a typical MEMS(Micro-Electro-Mechanical System)process,which including lithography development,vacuum magnetron sputtering,and lift-off on a 36° Y-X black LiTaO3.In addition,high purity gold was selected as the material of the IDTs and the sensitive layer.Besides,to create the liquid environment for the biological reaction,a homemade detection cell was fabricated with PMMA.During the detection procedure,the ss-DNA probes were immobilized on the surface of the sensitive layer by Au-S bonds.Then,the complementary sequence at various concentrations were pumped into the reaction cell respectively.Finally,the real-time phase shifts owing to the mass-loading in the sensitive area were recorded by a monitoring software.The results in this study revealed that this type of SH-SAW biosensor could be used to detect the Pseudomonas aeruginosa nucleic acid,and the limit of detection was as low as 0.28 nmol/L.②The improvement of the sensitivity owing to the application of single-layered graphene film in the sensitive area of the SH-SAW biosensorThe SH-SAW biosensor was fabricated on a ST-90° X quartz substrate,CVD-grown single-layered graphene was chosen as the material of the sensitive layer.During the detection procedure,the aptamers of the endotoxin were immobilized on the surface of the graphene film,then endotoxin solution at various concentrations were pumped into the sensitive area by a detection cell.The results indicated that the detection limit was as low as 3.53 ng/mL.③The improvement of the sensitivity of the Love wave biosensor for detection of nucleic acid owing to the application of single-layered graphene/Au-nanoparticlesFirstly,SH-SAW biosensor was fabricated on a ST-90° X quartz substrate.To decrease the energy loss and improve the sensitivity of detection,SiO2 layer was deposited on the flat surface of the SH-SAW biosensor by PECVD as the waveguide layer.Then,CVD-grown single-layered graphene film was transferred onto the sensitive area of the waveguide layer as sensitive film.In addition,EBE was adopted to form Au NPs on the sensitive film,which was used to immobilize the probe by Au-S bonds.The results indicated that this type of Love wave biosensor could be applied for detecting Staphylococcus aureus nucleic acid and the limit of detection was as low as 12.4 pg/mL.