Localized surface plasmon resonance based point-of-care system for sepsis diagnosis

Based on localized surface plasmon resonance (LSPR) enhanced quantum dot (QD) emission in a sandwich assay of “capture PCT antibody/PCT/detection PCT antibody labelled with QD” on a gold nanoarray chip, a fully automated point-of-care (POC) system for quick quantitative analysis of procalcitonin (PCT) for sepsis diagnostics was developed. The core technology of the system is to design and fabricate gold nanostructures that can generate plasmonics at resonant wavelength coincident with excitation wavelength of the fluorescent dyes. Gold nanopillar arrays at the size of 140 nm square and 320 nm pitch were found to be good candidates for the desired dye emission. Gold nanochip fabricated by e-beam lithography or nanoimprinting was integrated into a microfluidic chip, with analyte sampling and bioassay reagent flow controlled by LabVIEW program. To detect QD emission of the bioassay from the chip, a CCD camera and a laser source controlled by LabVIEW were incorporated to form a user-friendly and fully-automated POC system for on-site detection of PCT in clinics. Upon detection, the microfluidic chip is inserted into the POC system, where the processes of blood sample loading, detection antibody recognition, fluorescent dye labelling, fluorescent detection, and data analysis are conducted automatically in the device within 30 min at a test sensitivity of 0.5 ng/ml, which fulfills the clinical needs for diagnosis of sepsis through PCT biomarker.