Therapeutic Applications of Halloysite

The Horizons of Medical Mineralogy: Structure-Bioactivity Relationship and Biomedical Applications of Halloysite Nanoclay

Medical mineralogy explores the interactions between natural minerals and living organisms such as cells, tissues, and organs and develops therapeutic and diagnostic applications in drug delivery, medical devices, and healthcare materials. Many minerals (especially clays) have been recognized for pharmacological activities and therapeutic potential. Halloysite clay (Chinese medicine name: Chishizhi), manifested as one-dimensional aluminum silicate nanotubes (halloysite nanotubes, HNTs), has gained applications in hemostasis, wound repair, gastrointestinal diseases, tissue engineering, detection and sensing, cosmetics, and daily chemicals formulations. Various biomedical applications of HNTs are derived from hollow tubular structures, high mechanical strength, good biocompatibility, bioactivity, and unique surface characteristics. This natural nanomaterial is safe, abundantly available, and may be processed with environmentally safe green chemistry methods. This review describes the structure and physicochemical properties of HNTs relative to bioactivity. We discuss surface area, porosity and surface defects, hydrophilicity, heterogeneity and charge of external and internal surfaces, as well as biosafety. The paper provides comprehensive guidance for the development of this tubule nanoclay and its advanced biomedical applications for clinical diagnosis and therapy.

Recent Developments of Nano Flame Retardants for Unsaturated Polyester Resin

For many years, efforts have been made to reduce the flammability of unsaturated polyester resins (UPRs), which are often used in the rail, shipbuilding, and construction industries. Without modification, they often fail to meet fire safety standards. Despite a rich history of flame retardants (FRs) applied to UPRs, researchers seek new solutions that will provide lower flammability and smoke density, as well as attaining a lower environmental impact from the composites. The objective of the study is to highlight the most important recent research on promising nano FRs in order to promote their further development. Mechanisms of action of several groups of nano FRs, such as clay-based, carbon-based, transition metal compounds, layered double hydroxides, polyhedral oligomeric silsesquioxanes, and others, including bio-based, have been studied. Particular emphasis has been laid on nano FRs applied to UPRs, and their influences on thermal stability, flammability, and mechanical properties. Moreover, the environmental impact and toxicity of nano FRs have been discussed. Results have proved that nano FRs applied at low loadings may significantly improve thermal stability, with a simultaneous increase or only a slight decrease in mechanical properties. However, attention on related environmental issues has highlighted the necessity of carefully selecting novel nano FRs.

Polyurethane-Based Nanocomposites for Regenerative Therapies of Cancer Skin Surgery with Low Inflammatory Potential to Healthy Fibroblasts and Keratinocytes In Vitro

Nanocomposites based on thermoplastic polyurethanes (TPUs) filled with halloysite nanotubes (HNTs) were studied for their physicochemical and biological properties. Nanocomposites containing halloysite nanotube filler contents of 1 and 2% (E+1 and E+2), respectively, were obtained by extrusion. The newly formed E+1 and E+2 nanomaterials exhibited better flexibility and similar thermal properties compared to neat polyurethane. The use of atomic force microscopy (AFM) and differential scanning calorimetry (DSC) thermogram analysis showed that the distribution of halloysite nanotubes in the polymer matrix is more evenly dispersed in the E+1 nanomaterial, where the grains in the E+2 nanomaterial have a greater tendency to form agglomerates. Mechanical tests have shown that nanocomposites with the addition of HNT are characterized by a higher stress at break and elongation at break compared to neat TPU. The results of cytotoxicity tests suggest that the nanocomposite materials express lower toxicity to normal HaCaT and NHDF than to cancer Me45 cells. Further studies showed that the tested materials induced the expression of proinflammatory interleukins IL6 and IL8 in normal cells, but their overexpression in the cancer cell line resulted in cytostatic effects and proliferation reduction. Such a conclusion suggests the possible application of tested materials for regenerative therapies in cancer surgeries.

Zinc-Intercalated Halloysite Nanotubes as Potential Nanocomposite Fertilizers with Targeted Delivery of Micronutrients

This study reports on the development of nanocomposites utilizing a mineral inhibitor and a micronutrient filler. The objective was to produce a slow release fertilizer, with zinc sulfate as the filler and halloysite nanotubes as the inhibitor. The study seeks to chemically activate the intercalation of zinc into the macro-, meso-, and micropores of the halloysite nanotubes to enhance their performance. As a result, we obtained three nanocomposites in zinc sulfate solution with concentrations of 2%, 20%, and 40%, respectively, which we named Hly-7Å-Zn2, Hly-7Å-Zn20, and Hly-7Å-Zn40. We investigated the encapsulation of zinc sulfate in halloysite nanotubes using X-ray diffraction analysis, transmission electron spectroscopy, infrared spectroscopy (FTIR), and scanning electron microscopy with an energy-dispersive spectrometer. No significant changes were observed in the initial mineral parameters when exposed to a zinc solution with a concentration of 2 mol%. It was proven that zinc was weakly intercalated in the micropore space of the halloysite through the increase in its interlayer distance from 7.2 to 7.4. With an increase in the concentration of the reacted solution, the average diameter of the nanotubes increased from 96 nm to 129 nm, indicating that the macropore space of the nanotubes, also known as the "site", was filled. The activated nanocomposites exhibit a maximum fixed content of adsorbed zinc on the nanotube surface of 1.4 wt%. The TEM images reveal an opaque appearance in the middle section of the nanotubes. S SEM images revealed strong adhesion of halloysite nanotubes to plant tissues. This property guarantees prolonged retention of the fertilizer on the plant surface and its resistance to leaching through irrigation or rainwater. Surface spraying of halloysite nanotubes offers accurate delivery of zinc to plants and prevents soil and groundwater contamination, rendering this fertilizer ecologically sound. The suggested approach of activating halloysite with a zinc solution appears to be a possible route forward, with potential for the production of tailored fertilizers in the days ahead.

Characterization and Molecular Modelling of Non-Antibiotic Nanohybrids for Wound Healing Purposes

The healing process of chronic wounds continues to be a current clinical challenge, worsened by the risk of microbial infections and bacterial resistance to the most frequent antibiotics. In this work, non-antibiotic nanohybrids based on chlorhexidine dihydrochloride and clay minerals have been developed in order to design advanced therapeutic systems aimed to enhance wound healing in chronic lesions. To prepare the nanohybrids, two methodologies have been compared: the intercalation solution procedure and the spray-drying technique, the latter as a one-step process able to reduce preparation times. Nanohybrids were then fully studied by solid state characterization techniques. Computational calculations were also performed to assess the interactions between the drug and the clays at the molecular level. In vitro human fibroblast biocompatibility and antimicrobial activity against Staphylococcus aureus and Pseudomonas aeruginosa were assessed to check biocompatibility and potential microbicidal effects of the obtained nanomaterials. The results demonstrated the effective organic/inorganic character of the nanohybrids with homogeneous drug distribution into the clayey structures, which had been confirmed by classical mechanics calculations. Good biocompatibility and microbicidal effects were also observed, especially for the spray-dried nanohybrids. It was suggested that it could be due to a greater contact area with target cells and bacterial suspensions.

Novel carboxymethyl cellulose-halloysite-polyethylene glycol nanocomposite for improved 5-FU delivery

Drug nano-carriers are crucial for achieving targeted treatment against cancer disorders with minimal side effects. In this study, a pH-responsive nanocomposite based on halloysite nanotube (HNT) coated with carboxymethyl cellulose (CMC)/polyethylene glycol (PEG) hydrogel for controlled delivery of 5-Fluorouracil (5-FU), a hydrophobic chemotherapy drug prescribed for different types of cancers was synthesized for the first time using the water-in-oil-in-water (W/O/W) technique. The developed CMC/PEG/HNT/5-FU nanocomposite was characterized by dynamic light scattering (DLS), zeta potential, Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and Field emission scanning electron microscope (FE-SEM) to get information about the particle size, surface charge, interactions between functional groups, crystalline structure and morphology, respectively. High efficiencies in terms of drug entrapment and loading (46 % and 87 %, respectively) were attained. In-vitro drug release results revealed an improved and sustained 5-FU delivery in an acid environment compared to the physiological medium, corroborating the pH-sensitivity of the developed nano-carrier. Flow cytometry and MTT assays demonstrated that the 5-FU loaded nanocomposite had considerable cytotoxicity on MCF-7 breast cancer cells while it is not toxic against L929 fibroblast cells. The nanocomposite synthesized herein could serve as a platform for the pH-sensitive release of anti-cancer drugs.

Nano-Clays for Cancer Therapy: State-of-the Art and Future Perspectives

To date, cancer continues to be one of the deadliest diseases. Current therapies are often ineffective, leading to the urgency to develop new therapeutic strategies to improve treatments. Conventional chemotherapeutics are characterized by a reduced therapeutic efficacy, as well as them being responsible for important undesirable side effects linked to their non-specific toxicity. In this context, natural nanomaterials such as clayey mineral nanostructures of various shapes (flat, tubular, spherical and fibrous) with adjustable physico-chemical and morphological characteristics are emerging as systems with extraordinary potential for the delivery of different therapeutic agents to tumor sites. Thanks to their submicron size, high specific surface area, high adsorption capacity, chemical inertia and multilayer organization of 0.7 to 1 nm-thick sheets, they have aroused considerable interest among the scientific community as nano systems that are highly biocompatible in cancer therapy. In oncology, the nano-clays usually studied are halloysite, bentonite, laponite, kaolinite, montmorillonite and sepiolite. These are multilayered minerals that can act as nanocarriers (with a drug load generally between 1 and 10% by weight) for improved stabilization, efficient transport and the sustained and controlled release of a wide variety of anticancer agents. In particular, halloysite, montmorillonite and kaolinite are used to improve the dissolution of therapeutic agents and to delay and/or direct their release. In this review, we will examine and expose to the scientific community the extraordinary potential of nano-clays as unique crystalline systems in the treatment of cancer.

Recent advancement in polymer/halloysite nanotube nanocomposites for biomedical applications

Halloysite nanotubes (HNTs) have recently been the subject of extensive research as a reinforcing filler. HNT is a natural nanoclay, non-toxic and biocompatible, hence, applicable in biomedical fields. This review focuses on the mechanical, thermal, and functional properties of polymer nanocomposites with HNT as a reinforcing agent from an experimental and theoretical perspective. In addition, this review also highlights the recent applications of polymer/HNT nanocomposites in the biomedical fields.

Influence of halloysite nanotubes on the efficiency of Asparaginase against mice Ehrlich solid carcinoma

Herein, the impact of the halloysite nanotubes to suppress the side effects of Asparaginase (ANase) cellular proliferation was investigated. Methods: A total of 100 adult male mice was employed. These mice were divided into four equal groups; Group 1 (control), Group 2 (ESC group) of a single dose of 0.15 ml Ehrlich cells (2 × 106) intraperitoneal infusion(IP), Group 3 (ESC + ANase group) received six doses equal treatments of Intratumoral (IT) 0.07 ml Aspragnase (7 mg/kg) over two weeks. For two weeks, Group 4 (ESC + ASNase + HNTs) received an IT administration of 0.07 ml Asparaginase stocked on Halloysite nanotubes (HNTs) (30 mg/kg) three times per week. A blood specimen was collected, and the liver was removed to be investigated histologically. Results: TEM measurements for the Halloysite nanoclay showed their tubular cylindrical shape with a mean diameter of 50 nm and an average length of 1 μm, whereas The X-ray diffraction pattern of the Halloysite nanoclay showed their characteristic peaks. ESC increases the serum levels of aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, and bilirubin than control and other groups, even as albumin and total protein were decreasing. After using Halloysite Nanotube, the rates of these variables were enhanced up to 75%. The hepatocytes histological studies showed protection against Ehrlich Solid carcinoma-induced degenerative, necrotic, and inflammatory changes up to 70%. In conclusion, halloysite nanotubes have demonstrated effective removal of Ehrlich solid carcinoma in mice using an ASNase delivery system. It promoted the ASNase to inhibit the adverse effect of ANase's on the liver and remove the tumour cells.

Special Issue “Celebrating Applied Sciences Reaches 20,000 Articles Milestone: Feature Papers in Applied Biosciences and Bioengineering Section”

This Special Issue celebrates the publication of 20,000 articles in Applied Sciences [...]