In recent years, biocompatible composite materials have been increasingly used in drug delivery for cancer therapy. Specifically, for this field of application, composite materials containing inorganic minerals, such as zeolites, would be helpful to solve the solubility problems of some drugs in physiological aqueous solutions. Among such drugs, curcumin, a water-insoluble compound extracted from the herb Curcuma longa, has attracted great attention due to its anti-inflammatory and potential anticancer effects. However, its poorly solubility in aqueous solutions is a crucial issue, which has led to the use of high dosage in oral formulations. Encapsulation of curcumin into a suitable water-compatible carrier would render the drug completely dispersible. Zeolites are inorganic crystalline aluminosilicates with uniform microporous structure and high surface area, which are commonly used as molecular sieve adsorbents. They can be used as pharmaceutical carrier systems to encapsulate drugs with intrinsic low aqueous solubility, thus improving their dissolution. In this work, zeolites will be integrated with a biocompatible polymer hydrogel in order to control the drug release rate within the body. In particular, poly(N-isopropylacrylamide) (PNIPAM) will be used because of its response to external stimuli, such as variations of temperature and pH. Zeolite/hydrogel composite materials will be developed in order to have an efficient controlled drug release system, as the zeolite structure has the capacity to encapsulate the drug (curcumin) and the hydrogel component can be used to tune the drug release behavior. The zeolite/hydrogel composites will be characterized in terms of materials properties and curcumin loading and release capability using different techniques, including scanning electron microscopy (SEM), powder X-ray diffraction (XRD), differential scanning calorimetry (DSC), and UV-spectroscopy (UV-vis).
In this research we propose to develop novel biocomposite materials for use in drug delivery applications, by integrating zeolite porous structures with a thermo-responsive polymer matrix made of PNIPAM. In the most common applications, zeolite particles are combined with polymers by chemical functionalization or physical incorporation. Among polymer systems, hydrogels have become popular carriers in drug delivery in recent years, especially those with pH- and temperature responsive behavior. The advantages of hydrogels in drug delivery are related to their simple preparation, continuous drug release behavior, lower toxicity (large water content in the swollen form) and potentially interesting behavior in response to external stimuli. Poly(N-isopropylacrylamide) (PNIPAM) is a water soluble thermo-responsive polymer with a lower critical solution temperature (LCST) around 32 °C, slightly below that of human body, thus enabling the possibility of releasing drugs from the polymer matrix after the collapse at temperatures above its LCST. Here, we propose to control the thermal sensitivity of the zeolite/PNIPAM drug delivery system by grafting the thermo-sensitive polymer on the zeolite structure, either the outer surface or/and the inner pore walls. Above the LCST, the water soluble extended chains of the polymer collapse and form a compact non-hydrophilic barrier. This mechanism can be used as an opening/closing switch of the zeolite pores, leading to a controlled and prolonged drug release profile. The combination of zeolites and thermo-responsive PNIPAM, with the pore switching mechanism, represents a novel approach that has not been used so far. Overall, the main research effort will be directed to the optimization of the properties of the zeolite/hydrogel biocomposite in order to reach a high loading capacity of bioactive molecules, a release profile that can be controlled by temperature, and low toxicity of the carrier system. These targets are still the subject of extensive research, and have not yet been achieved according to a preliminary literature survey.