Enhanced stability of RPA-CRISPR–Cas12a system for respiratory pathogen detection using Trehalose–Carboxymethyl Chitosan Lyoprotectant

Purpose Acute respiratory infections caused by bacterial and viral pathogens pose a major global health burden. The recombinase polymerase amplification (RPA)-CRISPR-Cas12a system offers a promising point-of-care testing (POCT) platform, but its field deployment is limited by the instability of lyophilized reagents. This study aims to develop a composite lyoprotectant to enhance the stability of the RPA-CRISPR-Cas12a system for respiratory pathogen detection. Materials and methods A composite lyoprotectant composed of trehalose and carboxymethyl chitosan (Tre-CMC) was formulated at various mass ratios. The optimal ratio was identified by evaluating matrix microstructure, enzyme activity retention, and primer-dimer suppression. The lyophilized system was tested for sensitivity, specificity, and long-term stability against six respiratory pathogens (H1N1, IBV, Neisseria meningitidis , SARS-CoV-2, Streptococcus pneumoniae , and human adenovirus) using real-time fluorescence and gel electrophoresis. Results This study establishes a promising proof-of-concept framework for an integrated, lyophilized RPA-CRISPR–Cas12a diagnostic system. The optimal Tre: CMC ratio (2:1) produced a porous, non‑hygroscopic matrix that preserved reagent integrity. The lyophilized system achieved a detection limit of 10 copies/reaction within 30 min for all six pathogens, with 100% specificity. After six months of storage at 4°C, RPA enzyme activity remained above 89%, and Cas12a-crRNA complex functionality was fully retained. Tre-CMC significantly reduced primer-dimer formation and nonspecific background fluorescence. While clinical evaluation using 21 nasopharyngeal swab samples demonstrated 100% concordance with RT-qPCR—preliminarily supporting the system's potential diagnostic accuracy—we acknowledge that this initial methodological framework requires broader and more rigorous downstream validation with larger clinical cohorts to formally establish its robust diagnostic performance. Conclusion The Tre-CMC composite lyoprotectant effectively stabilizes the RPA-CRISPR-Cas12a system, enabling cold-chain-independent storage and reliable POCT for respiratory pathogens in resource-limited settings.