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Clay minerals are historically among the most used materials with a wide variety of applications. In pharmaceutical and biomedical fields, their healing properties have always been known and used in pelotherapy and therefore attractive for their potential. In recent decades, the research has therefore focused on the systematic investigation of these properties. This review aims to describe the most relevant and recent uses of clays in the pharmaceutical and biomedical field, especially for drug delivery and tissue engineering purposes. Clay minerals, which are biocompatible and non-toxic materials, can act as carriers for active ingredients while controlling their release and increasing their bioavailability. Moreover, the combination of clays and polymers is useful as it can improve the mechanical and thermal properties of polymers, as well as induce cell adhesion and proliferation. Different types of clays, both of natural (such as montmorillonite and halloysite) and synthetic origin (layered double hydroxides and zeolites), were considered in order to compare them and to assess their advantages and different uses.

The increase in life expectancy and the increasing prevalence of diabetic disease and venous insufficiency lead to the increase of chronic wounds. The prevalence of ulcers ranges from 1% in the adult population to 3−5% in the over 65 years population, with 3−5.5% of the total healthcare expenditure, as recently estimated. The aim of this work was the design and the development of electrospun scaffolds, entirely based on biopolymers, loaded with montmorillonite (MMT) or halloysite (HNT) and intended for skin reparation and regeneration, as a 3D substrate mimicking the dermal ECM. The scaffolds were manufactured by means of electrospinning and were characterized for their chemico-physical and preclinical properties. The scaffolds proved to possess the capability to enhance fibroblast cells attachment and proliferation with negligible proinflammatory activity. The capability to facilitate the cell adhesion is probably due to their unique 3D structure which are assisting cell homing and would facilitate wound healing in vivo.

Background/Objectives: The development of therapies targeting unregulated Src signaling through selective kinase inhibition using small-molecule inhibitors presents a significant challenge for the scientific community. Among these inhibitors, pyrazolo[3,4-d]pyrimidine heterocycles have emerged as potent agents; however, their clinical application is hindered by low solubility in water. To overcome this limitation, some carrier systems, such as halloysite nanotubes (HNTs), can be used. Methods: Herein, we report the development of HNT-based nanomaterials as carriers for pyrazolo[3,4-d]pyrimidine molecules. To achieve this objective, the clay was modified by two different approaches: supramolecular loading into the HNT lumen and covalent grafting onto the HNT external surface. The resulting nanomaterials were extensively characterized, and their morphology was imaged by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). In addition, the kinetic release of the molecules supramolecularly loaded into the HNTs was also evaluated. QSAR studies were conducted to elucidate the physicochemical and pharmacokinetic properties of these inhibitors, and structure-based virtual screening (SBVS) was performed to analyze their binding poses in protein kinases implicated in cancer. Results: The characterization methods demonstrate successful encapsulation of the drugs and the release properties under physiological conditions. Furthermore, QSAR studies and SBVS provide valuable insights into the physicochemical, pharmacokinetic, and binding properties of these inhibitors, reinforcing their potential efficacy. Conclusions: The cytotoxicity of these halloysite-based nanomaterials, and of pure molecules for comparison, was tested on RT112, UMUC3, and PC3 cancer cell lines, demonstrating their potential as effective agents for prostate and bladder cancer treatment.

The adsorption of retinol, niacinamide and glycolic acid active ingredients on the internal surface of halloysite in an aqueous environment was explored at the molecular level by means of calculations based on quantum mechanics and force fields from empirical interatomic potentials. These active ingredients are stably adsorbed on the internal surface of halloysite forming hydrogen bonds between the hydrogen, oxygen and nitrogen atoms with the hydroxyl groups of the inner surface of the halloysite. In addition, electrostatic interaction between these active ingredients with the water molecules was observed. Therefore, the theoretical results indicate that the adsorption of these active principles is favourable in the halloysite nanotube, which allows directing future experimental investigations for the development and design of retinol, niacinamide and glycolic acid with halloysite nanotubes systems, which may be topical formulations for skincare.

Recently, mineral healing clays have gained much attention for wound-dressing applications. Here, we selected halloysite (HAL) clay as a biocompatible, non-toxic material that is useful as a drug delivery system to enhance the healing properties of water-soluble terpenoids 1-3 (T1-3). Terpenoids-loaded HAL clay (TH1-3) was prepared and characterized by adsorption equilibrium studies, X-ray powder diffraction (XRPD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), Fourier-transform infrared (FTIR) spectroscopy, and release studies. The results reveal that T1-3 were adsorbed at the HAL surface with good efficiency. The prevalent mechanism of drug retention is due to the adsorption via electrostatic interactions between the cationic groups of the T1-3 and the HAL’s external surface. Release studies demonstrated that T3 was released in a higher percentage (>60%) compared to T1-2 (≈50%). Additionally, TH1-3 were assessed for their antimicrobial activity and capability to promote the re-epithelialization of scratched HaCat monolayers, through the time-kill test and the wound-healing assays, respectively. The results reveal that all the tested formulations were able to reduce the microbial growth after 1 h of incubation and that they ensured complete wound closure after 48 h. Furthermore, at the concentration of 1 µg/mL, TH3 exhibited 45% wound closure at 24 h, compared to TH1 (27%) and TH2 (30%), proving to be the best candidate in making the tissue-repair process easier and faster.