In the present study, a novel pH-sensitive hydrogel composite of pectin-grafted-poly (acrylic acid-co-itaconic acid)/MWCNTs- COOH was prepared by using graft copolymerization of acrylic acid and itaconic acid on pectin backbone with incorporation of MWCNTS- COOH. The prepared hydrogel composite has been employed for the adsorption and controlled release of the diclofenac sodium (DS) drug. The hydrogel composite was characterized by the analysis methods: FTIR, XRD, SEM, and TGA to analyze structural characteristics before and after DS drug adsorption. The swelling ratio of the hydrogel composite was investigated at different pH values from pH 1.2 to 10. According to the results, the swelling ratio of the hydrogel composite was found 4195% at pH 7.4. Adsorption process parameters such as pH, contact time, adsorbent dose, and temperature were investigated and found to have a significant influence on DS drug adsorption. The maximum DS drug loading through adsorption of 91% was obtained at pH 3, adsorbent dose of 0.05 g, contact time of 150 min, and temperature of 15 °C. The adsorption isotherm and kinetic results were well-fitted to Freundlich and second-order models. Thermodynamic parameters including changes in Gibb’s free energy, enthalpy, and entropy suggested that the adsorption of DS drug onto hydrogel composite was a spontaneous and exothermic process. The in vitro drug release experiment showed that the cumulative release of DS drug from hydrogel composite after 35 h was significantly higher in simulated intestinal fluid at pH 7.4 than in simulated gastric fluid at pH 1.2.

A semi-natural composite of κ-carrageenan and bentonite, two natural biopolymers, was synthesized through free radical polymerization. This synthesis aimed to obtain a biodegradable, biocompatible, and swellable composite that is environmentally friendly. The components used in this synthesis are readily available, making it economically feasible and promising for potential biomedical applications. The composite is pH-responsive and intended for oral delivery of metformin hydrochloride and aminophylline, which have low bioavailability and undesirable side effects, respectively. The organic composite exhibits the advantage of reducing drug release in the acidic gastric medium. This composite is a stimuli-responsive polymeric material that has garnered significant attention in recent years for its application in oral drug delivery systems. These materials enable site-specific and controlled drug release while minimizing toxicity. The carrageenan-g-poly(acrylamide-co-acrylic acid)/bentonite composite was characterized using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), and field emission scanning electron microscopy (FE-SEM), which confirmed the successful synthesis of the composite. The swelling behaviour and point of zero charge of the composite were studied at different pH values, which showed a strong influence on the swelling properties of the composite. The drug loading capacity of the composite was measured at pH 5.3, and it was 70.60 mg/g for metformin and 95.66 mg/g for aminophylline at pH(3). The in vitro release profile of both drugs from the composite was also affected by the ionic strength, and it exhibited a lower release rate with higher salt concentration. The maximum release percentage of the drugs from carrageenan-g-poly(acrylic acid-acrylamide)/bentonite in simulated gastric, intestinal, and colon fluids was achieved within 40 h. The maximum release was 80% for metformin in simulated intestinal fluid (SIF) and 75% for aminophylline after 40 h.

The alginate-based hydrogel was prepared as a pH-sensitive drug delivery system. To enhance the drug loading capacity, activated carbon was introduced as a drug absorbent. The iron oxide was incorporated into the alginate matrix for the magnetic transferring to the target organ. The activated carbon and iron-oxide were dispersed uniformly in the alginate hydrogel. The drug release from the alginate/activated carbon composite hydrogel was carried out in various pH conditions with vitamin B12 and Lactobacillus lamnosers as model drugs. The fast and sustainable release of drug was observed in the basic condition due to the pH-sensitive solubility of alginate. The novel drug delivery system having pH-sensitive release property and magnetic movement to target place was developed by using the alginate/activated carbon composite magnetic hydrogels.