RNA aptamer-packaged virus-like particles for label-free, rapid, and on-site fluorescence detection of malachite green in aquatic products.

Malachite green (MG) is a banned antimicrobial dye widely used in aquaculture, whose persistence and toxicity pose serious risks to human health and the environment. Rapid, on-site detection of MG residues in aquatic products is essential for food safety surveillance. Here, we report a label-free fluorescence biosensor based on RNA aptamer-packaged virus-like particles (RNAptMG@VLPs) for rapid and sensitive MG detection. This platform uniquely utilizes a scalable E. coli-based bioproduction system to encapsulate MG-specific RNA aptamers within bacteriophage Qβ VLPs, providing substantial protection against RNase A degradation and thermal stress. The resulting RNAptMG@VLPs were deposited onto 3 MM blotting paper to fabricate portable sensing papers, which are compatible with standard 96-well plates for convenient on-site analysis. Under optimized conditions, the sensing paper exhibited a strong linear response to MG across 0.1 ppb to 10,000 ppb, with a limit of detection (LOD) of 0.087 ppb and a limit of quantification (LOQ) of 0.29 ppb, surpassing regulatory thresholds set by China (1 ppb) and the European Food Safety Authority (2 ppb). These results underscore the promise of RNAptMG@VLPs sensing paper as a practical tool for rapid, field-deployable MG screening in food safety monitoring.