Precisely designed growth of dual-color quantum dots bilayer nanobeads for ratiometric fluorescent immunoassay.

Colloidal quantum dots (QDs) have been widely used as fluorescent labeling materials in the field of in vitro diagnostics (IVD). In spite of the significant development of direct single-signal response fluorescent immunosensors, it is still a challenge to obtain the high accuracy and sensitivity of quantitative results of these sensors due to the influence of several factors unrelated to the analysis. Herein, we present a delicate design and synthesis of dual-color QDs bilayer nanobeads (red and green QDs nanobeads, R&G-QD nanobeads), achieving the precisely control of growth of the silicon layer with different proportions of ammonia, and inhibiting fluorescence resonance energy transfer (FRET) successfully. The dual-color QDs bilayer nanobeads have realized dual-channel detection (the acquisition of two emission wavelengths) of the target, and avoided the problems of low analytical accuracy and imprecise sensitivity of single-signal response. A proof-of-concept demonstration of a fluorescence-linked immunosorbent assay (FLISA) platform is conducted for the quantitative detection of prostate-specific antigen (PSA) with a sensitivity of 49 pg/mL and a linear range of 0.2–800 ng/mL. The dual-color QDs bilayer nanobeads FLISA platform with high sensitivity and accuracy holds great potential for early diagnosis of cancer or other diseases and provides a new approach for IVD. [Display omitted] • Dual-color QDs bilayer nanobeads were designed to synthesize by layer-by-layer assembly method. • Controlled growth of alternate red and green QD layers on pre-synthesized SiO 2 beads can suppress energy transfer. • Such dual-color QDs nanobeads deliver dual single calibration and can avoid errors caused from the single signal response. • A proof-of-concept demonstration of a FLISA platform is conducted for detecting PSA with high sensitivity and accuracy. [ABSTRACT FROM AUTHOR]