Utilization of APTES-functionalized coconut waste-based cellulose microfiber/zeolitic-imidazolate framework-8 composite for curcumin delivery

Abstract

With more than 7 million tons of coconut husk generated annually, this study proposes to fabricate the composite of coconut waste-based cellulose microfibers and zeolitic imidazolate framework-8 functionalized with (3-aminopropyl)-triethoxysilane (APTES-CMF/ZIF-8), which is used for curcumin uptake/release. The surface area and pore volume of APTES-CMF/ZIF-8 are found, respectively, at 247.6 m2/g and 0.21 m3/g. The morphology study also shows that the waste-based CMF possesses a uniform width at 5–10 μm, and a length of up to several tens of microns, while the impregnated ZIF-8 has a rhombic dodecahedron shape with a particle diameter of 300–400 nm. The behavior of the curcumin uptake using APTES-CMF/ZIF-8 is elucidated via kinetics, isotherm, and thermodynamic studies. The maximum curcumin adsorption reaches 626.4 mg/g at the following condition: APTES-CMF/ZIF-8 loading (mc) = 0.1% (w/w), uptake duration (t) = 1440 min, temperature (T) = 30 °C, and initial curcumin concentration of 1000 mg/L. This uptake follows the pseudo-second-order law and monolayer mechanism, with the fast migration of curcumin from the bulk solution to the surface of APTES-CMF/ZIF-8 as the rate-governing step. The curcumin and APTES-CMF/ZIF-8 interaction is driven by the electron exchange between both molecules. The release study of curcumin from Cur@APTES-CMF/ZIF-8 complies with the slow-first-order model. Moreover, the cumulative release is monitored at 74.2% at pH 5.5 and 47.9% at pH 7.4, signifying the pH-responsiveness of APTES-CMF/ZIF-8.