Regulating the alky chain length of fatty acid-didanosine prodrugs and evaluating its role in albumin binding.

Rational design of prodrugs for efficient albumin binding shows distinct advantages in drug delivery in terms of drug availability, systemic circulation, and potential targeting effect. And fatty acids are good candidates due to their high affinity to albumin. However, how the alkyl chain length of fatty acids affects the binding dynamics between prodrugs and albumin, despite its importance, is still unclear. In the present study, three prodrugs of didanosine (DDI) and fatty acids were designed and synthesized to evaluate the effect of the alkyl chain length on prodrug-albumin binding process, including capric acid-didanosine (CA-DDI), myristic acid-didanosine (MA-DDI), and stearic acid-didanosine (SA-DDI). The binding dynamics between these prodrugs with bovine serum albumin (BSA) were studied by fluorometry, circular dichroism (CD), UV analysis, and molecular docking. It turned out that DDI itself showed poor binding affinity to BSA. In contrast, CA-DDI, MA-DDI, and SA-DDI demonstrated significantly improved binding affinity. Interestingly, the binding affinity between DDI prodrugs and BSA was correlated with the alkyl chain length of fatty acids, and the binding constant significantly increased with the extension of alkyl chain length (KCA-DDI = 5.86 × 103 M-1, KMA-DDI = 8.57 × 103 M-1, and KSA-DDI = 11.42 × 103 M-1 at 298 K).