Split intron-exon system for circular RNA synthesis.

Ribozyme-based approaches have been extensively employed for in vitro circular RNA (circRNA) synthesis. However, several critical challenges are impeding the progress in this field, including the relatively low ribozyme utilization efficiency, limited synthetic flexibility, and complicated downstream purification procedures. Here, we introduce a split intron-exon (SIE) system for circRNA synthesis by physically separating the ribozyme from its substrates. This design ensures efficient circRNA synthesis by overcoming the inherent limitations of current ribozyme-based techniques, in which each ribozyme can only catalyse the synthesis of at most one circRNA molecule. Moreover, the SIE system enables the efficient synthesis of both unmodified and chemically modified circRNAs. Furthermore, the recyclability and immobilization of the ribozyme within the SIE system reduce reaction impurities and improves circRNA enrichment and yield. Overall, the SIE system holds great potential to advance the diversification and large-scale development of circRNA therapeutics.