Preparation and evaluation of novel oral tacrolimus nanocochleates for organ transplantation to reduce individual differences and improve drug safety.

After organ transplantation, patients require treatment with immunosuppressive drugs to prevent immune rejection and transplantation failure. Tacrolimus (FK506) is a widely used immunosuppressant known for its potent immunosuppressive effect and narrow therapeutic range. Monitoring of FK506 blood concentrations is essential to avoid nephrotoxicity. In this study, a novel FK506 nanomedicine (FK506 cochleates) was developed using a microfluidic method to reduce variability among individuals and improve drug safety. The particle size of FK506 cochleates was (183.3 ± 1.4) nm, the zeta potential was -(39.28 ± 2.12) mV, and the encapsulation efficiency was more than 85 %. Particle size of FK506 cochleates could be maintained for up to 12 weeks in freeze-dried powder form. Small-angle X-ray scattering (SAXS) experiment confirmed the formation of cochleates by adding calcium solution. In vitro release studies demonstrated a sustained-release profile of FK506 from the cochleates carrier. Furthermore, the cochleates carrier could protect FK506 from the influence of stomach acid and slowly release the drug in the intestine. After oral administration, FK506 cochleates exhibited sustained-release properties in rats, accumulating in the spleen and lymph nodes - key anatomical sites for FK506's pharmacological action. Importantly, FK506 cochleates significantly prolonged the survival time in the rabbit heart transplantation model while maintaining good safety profiles. In conclusion, the FK506 cochleates showed promising potential for enhancing drug safety in therapeutic organ transplantation.