Fabricating Four-Element Doped Carbon Dots-Based Fluorescent Ratiometric Reporter Platform for CRISPR/Cas-Driven Precise Sensing of Nucleic Acids

Conventional CRISPR/Cas sensing platforms exhibit poor efficiency concerning reporter-based demerits, including their interference-labile nature, photobleaching, low robustness due to a single output signal, and probe-concentration dependence. Herein, a carbon dots (CDs)-based dual-emissive fluorescent ratiometric CRISPR/Cas reporter platform was fabricated for biosensing and other analytical applications to bottleneck the demerits of conventional reporters, integrating the benefits of a ratiometric strategy and four-element doped carbon dots (4D CDs) as a transducer. Briefly, doping enhances the optical and physicochemical traits of CDs and minimizes the effect of the interfering species. A series of state-of-the-art N, P, S, and Cu codoped CDs (4D CDs) were synthesized using the hydrothermal approach and statistical tools, such as Box-Behnken design, analysis of variance, and others, enhancing photophysical traits, surface features, and sensitivity of CDs. The red-emissive CDs were prepared by using the same procedure but different precursors. The optimum 4D CDs (blue-emissive) and red-emissive CDs were used to unleash the principle of the fluorescent ratiometric CRISPR/Cas reporter system for diverse applications. Finally, the designed 4D CDs-based CRISPR/Cas biosensor was applied for nucleic acid monitoring, such as the COVID-19 nucleic acid. This project disclosed the controlled-doping principle to synthesize 4D CDs and unleashed the mechanism of ratiometric dual-emissive CRISPR/Cas-powered reporters for precise sensing applications. We anticipate the implementation of this technology in commercial analytical, biosensing, point-of-care, and other applications.