Microcavity-based SERS Chip For Ultrasensitive Immune Detection Of Cardiac Biomarkers

A variety of acute diseases or chronic diseases seriously threaten human health,therefore,the development of rapid and accurate diagnosis of diseases are particularly significant.With the continuous innovation and development in the field of biochemistry and life science,the specific biomarkers have been widely used in life science research like disease diagnosis.Rapid qualitative and quantitative analysis of biomarkers is a major research direction in disease diagnosis,However,due to the shortcomings of low sensitivity,long time,low specificity and complex pretreatment steps,traditional analytical methods have been insufficient to meet the increasing requirements of detection.In recent years,the advancement of surface-enhanced Raman scattering technique and optical microcavity has provided a novel solution for rapid,accurate,highly sensitive and specific biological detection,showing great potential in application.In order to improve the detection sensitivity and simplify the detection process,in this paper,the concept of microcavity was integrated into the surface-enhanced Raman scattering technology to construct a microcavity biochip for the ultra-sensitive detection of two kinds of cardiac biomarkers simultaneously,providing a new method for disease diagnosis.The details are as follows:1.The Preparation of dye-doped PS microspheres and the study of microcavity effectAn organic dye was selected as gain medium,the dye-doped polystyrene（PS）microspheres were prepared by swelling method and the active microcavity was formed.The morphology characterization demonstrated that the microcavity had good sphericity and smooth surface,and there was no obvious size change before and after swelling.At the same time,the optical microscopic image shows that the dye was evenly doped.What’s more,the optical properties of the samples were tested by microspectral system and near-field optical microscope system.Under the excitation of femto-second laser,the microsphere cavity acted as a light trapping device.The good optical constraint ability of microcavity limited the light field,and the cyclic oscillation of photons allowing them interacted with dye molecules for tens of thousands of times,which makes the optical signal significantly enhanced.The photoluminescence spectra show that the dye-doped microcavity was stimulated,and the quality factor of 1813 was obtained by calculation,which indicated that the constructed active microcavity had excellent light field restriction effect.2.Microcavity-based SERS chip for ultrasensitive immune detection of cardiac biomarkersHighly sensitive detection of specific cardiac markers is exceedingly essential for the early diagnosis and warning of cardiovascular disease.We developed a microcavity-based sandwich immune chip to realize the ultrasensitive detection of cardiac troponin I（c Tn I）and creatine kinase isoenzyme MB（CK-MB）by surface-enhanced Raman spectroscopy（SERS）method.Herein,polystyrene microspheres modified with gold nanoparticles（Au NPs）were fixed on the substrate via polydopamine,which was used as an immune capture chip.5,5’-Dithio bis-（2-nitrobenzoic acid）（DTNB）and 4-mercaptobenzoic acid（4MBA）labelled Au NPs served as immune signal probes for c Tn I and CK-MB,respectively.Light confinement effect of PS microcavities and localized surface plasmon resonance（LSPR）near the Au NPs synergistically strengthened the electromagnetic field and promoted the interaction between light and matter,which enhanced SERS performance with an enhancement factor of 1.95×10¹²for SERS sensing.The immunoassay results demonstrated the sensitive quantitative detection with the limit of detection（LOD）of 3.16 pg/m L and 4.27 pg/m L for c Tn I and CK-MB,separately.The method also had good specificity,reproducibility and stability,which was an effective diagnostic tool for ultrasensitive detection of cardiac biomarkers.