Chip architecture-enabled sensitivity enhancement of oblique-incidence reflectivity difference for label-free protein microarray detection

Abstract

Oblique-incidence reflectivity difference (OIRD) is a promising optical technique for detection of protein microarray chip with the compelling features of being label-free, real-time, high-throughput and nondestructive, but its sensitivity requires essential improvement for practical applications. In this work we report a simple yet highly efficient strategy to boost the sensitivity of OIRD by rationally engineering the biochip architecture via introducing a polymer film (polydopamine, PDA) to the glass surface. With anti-Zearalenone (ZEN) monoclonal antibody as a model target, up to 2 orders of magnitude sensitivity enhancement was demonstrated on this engineered chip compared to conventional silanized glass chip. Experimental investigation indicates that the OIRD sensitivity is positively correlated to the polymer thickness until reaching the maximal sensitivity at 90.2 nm thickness; a detection limit of as low as 5.0 ng mL−1 is achieved on this optimal chip. Theoretical calculation unveils that the polymer film serves as an interference layer to enhance the light-matter interaction for improved sensitivity, and the OIRD sensitivity possesses a periodic dependence on the film thickness. This work reports for the first time an interference-based versatile strategy to boost OIRD sensitivity and reveals the underlying mechanism, and thus paves a new way toward sensitive and label-free OIRD detection of protein microarrays.