Reducing burst release and enhancing sustained release in SAIB-based implants: The role of polyphenol-modification

Sucrose acetate isobutyrate (SAIB)-based in situ forming implants (SADS) are promising for long-acting drug delivery but suffer from undesirable burst release. Here, we propose a molecular-level strategy to mitigate burst release by covalently modifying the antipsychotic drug aripiprazole (ARP) with polyphenols-specifically 4-hydroxybenzoic acid (HBA), protocatechuic acid (PCA), and gallic acid (GA). These moieties form strong hydrogen bonds with SAIB, enhancing drug-matrix interactions. Among them, ARP-GA exhibited the best performance, showing a significant reduction in burst release (8.99 ± 2.10 %) compared to unmodified ARP (22.84 ± 1.03 %) and sustained release over 30 days in vitro. In vivo pharmacokinetics in rats confirmed prolonged circulation with a 2.5-fold increase in AUC (1466.59 ± 139.35 vs. 592.66 ± 157.68 ng/mL•d), extended T_max (6.40 ± 2.97 vs. 0.29 ± 0.42 days), and lower C_max/C_S (2.32 vs. 3.41), indicating improved release control. Rheological and porosity analysis supported the enhanced drug retention mechanism via hydrogen bonding. This approach also proved effective for six additional drugs, suggesting broad applicability. These findings demonstrate that polyphenol modification of APIs offers a carrier-compatible, drug-centric solution for burst release regulation. Overall, this strategy significantly enhances the safety and efficacy of SAIB-based long-acting injectable systems.