Controlled released of protein and herbicide by biocompatible alginate kappa carrageenan hydrogel

Protein adsorption plays a significant role in natural processes. For that reason, it can be applied in pharmaceutical sicience, biotechnology and tissue engineering. Controlled release systems have been developed for encapsulation and protection of bioactive agent in drug, food industry and agricultural area. Protein adsorption on biocompatible alginate-kappa carrageenan hydrogels and encapsulation of protein and herbicide molecules into hydrogels were investigated. Alginate-kappa carrageenan hydrogel beads, which were synthesized by dropping alginate-kappa carrageenan mixture in calcium chloride solution, were characterized by using SEM and FT-IR. Bovine Serum Albumin (BSA) adsorption on hydrogels was investigated at different temperature (25; 32.5 ve 40 ᵒC), pHs (2.8; 4.8 ve 6.8) and contact time. BSA adsorption was not achieved at pH 2.8 due to electrostatic repulsion between BSA and hydrogel. Hydrogel beads disrupted at higher pHs. The highest adsorption capacity (240mg/g) was found at pH 4.8. In addition, adsorption kinetics were evaluated by using theoretical kinetic models; pseudo-first-order, pseudo-second-order, and intraparticle diffusion model. As a result, BSA adsorption kinetic on hydrogel beads followed an intraparticle diffusion model. At different pHs (4.2; 4.8 ve 7.5) and salt concentration (CaCl2/KCl, 2/0; 2/2; 4/4), BSA molecules were encapsulated in alginate-kappa carrageenan hydrogel beads and controlled release of BSA from hydrogel beads was carried out in simulated gastric (pH 1.2) and intestinal fluids (pH 7.4) at 37ᵒC. The highest encapsulation efficiency (88.69%) was obtained at lower pH and higher salt concentration and the lowest encapsulation efficiency (28.50%) was obtained at pH 4.8 and lower salt concentration. The release of BSA in simulated gastric medium was negligible because of its low release amount. The amount of released BSA in simulated intestinal fluid from hydrogel prepared at pH 4.2 was found 13.3mg/g. However, the lowest amount of released BSA in simulated intestinal fluid from hydrogel prepared at pH 7.5 was found 2.9mg/g. BSA release kinetic data were fitted to Ritger-Peppas model. According to Ritger-Peppas model, release mechanism was demonstrated non-Fickian behaviour. To conclude, BSA release from hydrogel matrix occurred both BSA diffusion and relaxation of chain. 2, 4-dichlorophenoxyacetic acid (2,4-D) and isoproturon herbicides were encapsulated into hydrogel beads. In order to increase the herbicide encapsulation and decrease the herbicide release, Ca-bentonite, activated carbon, perlite and ferryhydrite composite hydrogel beads were synthesized. Addition of adsorbent into hydrogel beads was effective to obtain higher encapsulation efficiency.