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.

Novel pH-sensitive of organic composite (kc-g-poly(AAc-co-AAm)bentonite), synthesis and characterization candidate as a carrier for controlled release system in vitro to some drugs
    Abstract
    1 Introduction
    2 Materials and methods
        2.1 Materials
        2.2 Synthesis of organic composite hydrogel and composite of carrageenan-g-poly(acrylamide-acrylic acid)bentonite
        2.3 Characterization techniques
        2.4 Study of swelling
        2.5 Determination of point of zero charge (pHpzc)
        2.6 Experiments of (drug loading and release)
    3 Results and discussion
        3.1 FTIR analysis
        3.2 Morphology studies (FE-SEM)
        3.3 Transmission electron microscopy
        3.4 The X-ray diffraction (XRD) analysis
        3.5 Swelling study
        3.6 The point of zero charge (PZC)
        3.7 In vitro drug loading and release studies in different pH
        3.8 Effect of salinity in vitro drug release
    4 Conclusion
    Acknowledgements 
    References

• Asawer A. Mhammed Alzayd(Department of Physiology, Biochemistry and Pharmacology Branch, University of Kerbala, Kerbala, Iraq) Corresponding author
• Nadher D. Radia(Department of Chemistry, College of Education, University of Al-Qadisiyah, Al‑Qadisiyah, Iraq) Corresponding author