Functional lightweight polystyrene@polydopamine nanoparticle for high-performance ELISA.

Nanoparticles are usually used as carrier to load more antibody and enzyme to improve the sensitivity of enzyme-linked immunosorbent assay (ELISA). However, limited by high density and complicated modification procedure, the traditional nanoparticles such as Au nanoparticles (AuNPs) usually induce large background signal and poor reproducibility in ELISA. In this work, functional lightweigh nanoparticle polystyrene@polydopamine (PS@PDA) was prepared and induced as the carrier of detection antibody and horseradish peroxidase (HRP) to form PS@PDA@Ab/HRP biojungates. The appropriate density (close to water) and good hydropilicity ensure the good dispersion of PS@PDA@Ab/HRP in solution, preventing the physical sedimention and decreasing the background signal even though the bioconjugate's size is close to 200 nm. The large surface area and abundant active group from PDA facilitate the loading of detection antibody and HRP, improving the loading efficiency and stability of biojungates. Based on it, taking interleukin-17A (IL-17A, a biomarker of psoriasis) as the detection target, we developed a PS@PDA-based sandwich ELISA, achieving a sensitive dynamic range from 0.3 to 80 pg/mL and a detection limit of 0.2 pg/mL. Furthermore, the contents of IL-17A were assayed successfully in 10-fold diluted serum samples from psoriasis patients. Compared with those commercial or AuNP-based ELISA, our PS@PDA-based ELISA method exhibits higher sensitivity, lower background interference, and higher stability, which will significantly improve the application of ELISA in the low-abundant biomolecule assays.