• CircRNAs are stable, conserved, and expressed in a cell- and tissue-specific manner, with functions as miRNA sponges, protein decoys, and modulators of transcription.
• A subset of circRNAs can be translated via cap-independent mechanisms, expanding their functional repertoire beyond noncoding roles.
• In vitro transcribed circRNAs exhibit high stability and low immunogenicity, making them promising platforms for biomedical applications such as vaccines and therapeutics.
• This review highlights synthesis methods, delivery strategies, and current advances in circRNA-based biomedical applications, underscoring their potential in clinical translation.