Functionalized vertical GaN micro pillar arrays with high signal-to-background ratio for detection and analysis of proteins secreted from breast tumor cells

Abstract

The detection of cancer biomarkers has recently attracted significant attention as a means of determining the correct course of treatment with targeted therapeutics. However, because the concentration of these biomarkers in blood is usually relatively low, highly sensitive biosensors for fluorescence imaging and precise detection are needed. In this study, we have successfully developed vertical GaN micropillar (MP) based biosensors for fluorescence sensing and quantitative measurement of CA15-3 antigens. The highly ordered vertical GaN MP arrays result in the successful immobilization of CA15-3 antigens on each feature of the arrays, thereby allowing the detection of an individual fluorescence signal from the top surface of the arrays owing to the high regularity of fluorophore-tagged MP spots and relatively low background signal. Therefore, our fluorescence-labeled and CA15-3 functionalized vertical GaN-MP-based biosensor is suitable for the selective quantitative analysis of secreted CA15-3 antigens from MCF-7 cell lines, and helps in the early diagnosis and prognosis of serious diseases as well as the monitoring of the therapeutic response of breast cancer patients.

Extended-Gate FET Biosensor Based on GaN Micropillar Array and Polycrystalline Layer: Application to Hg2+ Detection in Human Urine

“…For EGFET biosensor, extended-gate electrode materials with large surface area and low impedance are beneficial to improve the sensing performance, e.g., detection sensitivity and limit of detection (LOD). − , To our best knowledge, materials of Si, SnO 2 , ITO, ZnO, and Ga 2 O 3 with nanorod structure has been used as extended-gate to enhance the sensing performance. ,,,− However, these materials have poor electrical conductivity and require to combine with conductive materials (e.g., Al layer, FTO, Ag wire layer, or corresponding seed layer), this would complicate the preparation, reduce repeatability and lead to reduced practicality. ,,,− In contrast, GaN material can achieve not only high surface area by growing nanowire or nanowire array structures but also high electrical conductivity by using low temperature MOCVD growth. − Furthermore, GaN exhibits excellent chemical stability for biosensor application, and the maturity of GaN based electronic devices (e.g., transistor, LED, solar cell) ensure the integration of GaN-based biosensor with GaN electronic devices, which would bring out multifunctional chip. , For EGFET biosensor, compared with the crawling nanowire, vertically grown nanowires (e.g., micropillar array, nanorod array) are independent of each other and can expose more side surfaces, making the nanowire array more sensitive to external charge. , Currently, GaN micropillar array (GMPA) are mainly applied as fluorescence/electrochemical biosensors, only two reports employed crawling GaN nanowires as extended-gate of EGFET biosensor. , But in fact, the detection sensitivity is poor even with high surface area, because the impedance of GaN nanowires grown by conventional processes is large. Thus, preparing GMPA with high electrical conductivity can further improve the detection sensitivity and LOD, but this is still a challenge.…”