Circular RNA: From non-coding regulators to functional protein encoders.

Circular RNAs (circRNAs), a distinct class of non-coding RNAs characterized by a covalently closed circular structure, have gained prominence as a promising research field due to their unique biological properties and functional roles relative to linear RNAs. This review summarizes recent progress in circRNA research, emphasizing fundamental mechanisms and translational potential. We first outline the discovery, biological features, synthesis, and purification of circRNAs. Next, their delivery systems, biological functions, and applications are reviewed. Finally, we discuss challenges and future prospects for clinical translation, with a focus on advancing precision medicine, gene therapy, and personalized vaccines. This review uniquely integrates recent advances in circRNA biology with their translational applications, offering a comprehensive perspective from molecular mechanisms to clinical potential.