Development of enzyme-free immunosensor based on nanobrush and fluorescence dye for sensitive detection of procalcitonin

Accurate detection of the biological biomarkers can provide valuable information for early diagnosis and treatment of many diseases. In this work, an enzyme-free immunosensor based on nanobrushes and the fluorescent dye (Rhodamine-6G) for detection of the biomarker procalcitonin (PCT) in human serum albumin has been successfully developed. The immuno nanobrush has been prepared by conjugating the poly-glutamic acid (PGA) and the detection antibody of PCT on the surface of the polystyrene (PS) nanospheres sequentially. The abundant functional groups (-COO-) on the PGA chain of the nanobrushes have the potential ability to bind tightly with a lot of the fluorescent dye (Rhodamine-6G) by electrostatic interaction, which can significantly augment the fluorescence signal intensity of the dyed nanobrushes, and then acted as the signal amplification system of the immunosensor to improve the sensitivity for determination of the PCT. Meanwhile, the immunomagnetic beads can selectively capture the PCT from the samples. The results showed that the immunoassay exhibited high sensitivity and selectivity with satisfactory reproducibility and stability, and successfully applied to determine the PCT levels in real human serum samples. The enzyme-free immunoassay overcomes the defects of traditional Enzyme-linked immunosorbent assay and provides a novel approach to detect the biomarker PCT for clinical diagnosis of the inflammation.