Nano-encapsulation of epigallocatechin gallate (EGCG) within zeolitic imidazolate framework-8 (ZIF-8) and controlled release of EGCG

Abstract

Epigallocatechin Gallate loaded Zeolitic Imidazolate Framework-8 (E-ZIF-8) nanoparticles were synthesized utilizing a synchronized nano-encapsulation method. The structural and characteristics of these nanoparticles were analyzed using SEM, UV–Vis, EDX, TEM, DLS, FTIR, TGA, and XRD. E-ZIF-8 was synthesized through the coordination of zinc nitrate and 2-methylimidazole in the presence of the bioactive EGCG molecules. The structure analysis results show that E-ZIF-8 presents a uniform and regular dodecahedral morphology with particle sizes below 200 nm. The zeta potential indicates that E-ZIF-8 nanoparticles exhibit a surface charge ranging from 30 to 50 mV, and TGA results show that the degradation temperature has increased, confirming a dramatic improvement in physicochemical stability. The EGCG loading capacity of E-ZIF-8 was quantified at 193±1 mg/g, showcasing substantial radical scavenging activity against both ABTS and DPPH radicals. Furthermore, E-ZIF-8 nanoparticles displayed pH-dependent drug release profiles. EGCG reached equilibrium of release within 1 hour, with cumulative release rates exceeding 90 % at both pH 6.8 and pH 2.0. In contrast, the release rates under the protective ZIF-8 delivery system were significantly reduced, with release percentages of 32.86±1.12 % and 57.82±1.66 % at the same time point. After 5 h, the cumulative release rates were only 62.56±2.10 % and 77.75±1.06 %, respectively. The synchronized nanoscale encapsulation technique effectively facilitates the encapsulation and sustained release of EGCG, demonstrating superior therapeutic efficacy compared to free EGCG. These findings suggest that the concurrent nano-encapsulation strategy of E-ZIF-8 enhances the stability and bioavailability of EGCG, positioning E-ZIF-8 as a promising pH-responsive nanoplatform for drug delivery applications.