A comprehensive study on the synergistic drug loading/releasing activity of a modified chitosan: A RSM optimization study

• Good ability of Clinoptilolite/chitosan/histidine in DF loading. • Study of simultaneous effects of experimental variables on loading/releasing process via RSM. Synthesis of new biodegradable and environmentally friendly materials is a research field for drug loading and release. Thus, the clinoptilolite surface was modified by chitosan and then by the amino acid histidine. XRD, FTIR, SEM-EDX, and X-ray map characterized bare and modified clinoptilolites. XRD data showed a crystallite size of 37 nm for NC-Chit-His. This sample was used to load and release diclofenac sodium via a response surface methodology (RSM) approach to investigate the simultaneous effect of influencing factors. The results showed that, at constant pH, drug loading increases with increasing drug concentration and the contact time elongation. At a fixed drug concentration, the drug loading decreases with increasing adsorbent dosage or elongated contact time; at a fixed adsorbent dosage, it increases with increasing contact time. Optimum conditions for the loading process were obtained in the contact time of 19 min, pH 3, drug concentration 28 ppm, and adsorbent dosage of 0.4 g/L. The results of investigating the simultaneous effect of factors in the drug release process showed that during the fixed contact time, the drug release increases with the increase in pH. At constant pH, drug release rate decreases with increasing adsorbent dosage. The drug release decreases with increasing adsorbent dosage in a fixed contact time. Optimum conditions for the release process were obtained in the contact time of 6.70 min, pH 8, and adsorbent dosage of 0.4 g/L. The overall results showed that, according to the correlation coefficient (R 2 ) in the process of loading and releasing the drug, the design of the experiment is very suitable for predicting the experimental data.