Design of molecularly imprinted alginate microgels for topical release of insulin

Abstract

In this work, pH-sensitive molecularly imprinted (MIP) microgels are developed based on alginate for topical insulin delivery and ocular disease treatment. MIP microgels were synthesized via the emulsification-gelation method with uniform size distribution (9–11 µm) and rough surface structure. Moreover, the impact of insulin concentration, adsorption time, and pH of the drug solution on the adsorption capacity of MIP microgels was studied. Increasing the initial insulin concentration showed enhanced MIP microgel adsorption capacity at pH 5.4, while kinetic analysis revealed insulin binding after 1 h. The kinetics of insulin release at pH 6.4 (normal eye) and 7.4 (dry eye) demonstrated a good fit with the Korsmeyer–Peppas model, indicating controlled drug release. The pH-sensitive MIPs resulted in slower insulin release at pH 6.4 with ∼60% of the drug released within 1 h and reaching 80% after 8 h. In contrast, a higher insulin release rate was observed at pH 7.4 (∼ 80% after 8 h). MIP microgels showed selective adsorption toward the template molecule measured by imprinting factors about 0.60 ± 0.03 and 1.44 ± 0.21 for bovine serum albumin (BSA) and insulin, respectively. The mucoadhesive strength of MIP and NIP microgels, assessed by adsorbing them onto cow mucin, exhibited excellent performance, with values of 82±3% and 91±2%, respectively. In summary, the MIP microgels show sustained, and controlled drug delivery and are good candidates for ocular tissue drug delivery.