Synthesis and characterization of cellulose functionalized zeolitic diatomite as an enhanced carrier of oxaliplatin drug; loading, release, and cytotoxicity

Natural diatomite frustules (D) were incorporated in zeolitization and cellulose functionalization processes to obtain zeolitized diatomite (ZD) and cellulose fibrous/zeolitized diatomite composite (CF/ZD). The modified products were assessed as potential carriers of oxaliplatin drug (OXPL) with enhanced properties. The prepared ZD (112.5 mg/g) and CF/ZD (268.3 mg/g) structures exhibit significantly enhanced encapsulation capacities as compared to raw diatomite (65.9 mg/g). The occurred encapsulation reactions follow the classic Pseudo-first order kinetic (R² > 0.93) and traditional Langmuir isotherm (R² = 0.99). The estimated effective encapsulation site density of CF/ZD is 104.8 mg/g which is a notably higher value than ZD (44.6 mg/g) and D (28.4 mg/g). Moreover, each effective site can be occupied with up to 3 molecules of OXPL molecules in vertical forms involving multi-molecular mechanisms. The encapsulation energy (<40 KJ/mol) suggested the predominant effects of the physical mechanisms during the encapsulation reactions. The release profiles of ZD as well as CF/ZD exhibit slow and controlled properties for about 100 h either at pH 5.5 or at pH 7.4. The release kinetic studies involving the obtained diffusion exponent values (>0.45) suggested non-Fickian transport and complex erosion/diffusion release mechanism. These structures exhibit enhanced cytotoxic effects on the HCT-116 cancer cell lines (D (18.78 % cell viability), ZD (9.76 % cell viability), and CF/ZD (3.16 % cell viability).