Fabrication and Characterization of Biodegradable pH-Responsive Halloysite Poly(lactic-co-glycolic acid) Micro-sphere for Controlled Released of Phenytoin Sodium

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 Advances of Halloysite Nanotubes in Biomedical Applications

Halloysite nanotubes (HNTs) have emerged as a highly regarded choice in biomedical research due to their exceptional attributes, including superior loading capacity, customizable surface characteristics, and excellent biocompatibility. HNTs feature tubular structures comprising alumina and silica layers, endowing them with a large surface area and versatile surface chemistries that facilitate selective modifications. Moreover, their substantial pore volume and wide range of pore sizes enable efficient entrapment of diverse functional molecules. This comprehensive review highlights the broad biomedical application spectrum of HNTs, shedding light on their potential as innovative and effective therapeutic agents across various diseases. It emphasizes the necessity of optimizing drug delivery techniques, developing targeted delivery systems, rigorously evaluating biocompatibility and safety through preclinical and clinical investigations, exploring combination therapies, and advancing scientific understanding. With further advancements, HNTs hold the promise to revolutionize the pharmaceutical industry, opening new avenues for the development of transformative treatments.

Fabrication of Bio-Nanocomposite Based on HNT-Methionine for Controlled Release of Phenytoin

In this study, a novel promising approach for the fabrication of Halloysite nanotube (HNT) nanocomposites, based on the amino acid named Methionine (Met), was investigated. For this purpose, Met layered on the outer silane functionalized surface of HNT for controlled release of Phenytoin sodium (PHT). The resulting nanocomposite (MNT-g-Met) was characterized by FTIR, XRD, Zeta potential, TGA, TEM and FE-SEM. The FT-IR results showed APTES and Met peaks, which proved the modification of the HNTs. The zeta-potential results showed the interaction between APTES (+53.30) and Met (+38.80) on the HNTs (-30.92). The FE-SEM micrographs have displayed the grafting of Met on the modified HNTs due to the nanotube conversion to a rough and indistinguishable form. The amount of encapsulation efficiency (EE) and loading efficiency (LE) of MNT-g-Met was 74.48% and 37.24%, while pure HNT was 57.5%, and 28.75%, respectively. In-vitro studies showed that HNT had a burst release (70% in 6 h) in phosphate buffer while MNT-g-Met has more controlled release profile (30.05 in 6 h) and it was found to be fitted with the Korsmeyer-Peppas model. Due to the loading efficiency and controlled release profile, the nanocomposite promote a good potential for drug delivery of PHT.

Solid-in-Oil-in-Water Emulsion: An Innovative Paradigm to Improve Drug Stability and Biological Activity

Abstract

An emulsion is a biphasic dosage form comprising of dispersed phase containing droplets that are uniformly distributed into a surrounding liquid which forms the continuous phase. An emulsifier is added at the interface of two immiscible liquids to stabilize the thermodynamically unstable emulsion. Various types of emulsions such as water-in-oil (w-o), oil-in-water (o-w), microemulsions, and multiple emulsions are used for delivering certain drugs in the body. Water (aqueous) phase is commonly used for encapsulating proteins and several other drugs in water-in-oil-in-water (w-o-w) emulsion technique. But this method has posed certain problems such as decreased stability, burst release, and low entrapment efficiency. Thus, a novel “solid-in-oil-in-water” (s-o-w) emulsion system was developed for formulating certain drugs, probiotics, proteins, antibodies, and tannins to overcome these issues. In this method, the active ingredient is encapsulated as a solid and added to an oil phase, which formed a solid-oil dispersion. This dispersion was then mixed with water to form a continuous phase for enhancing the drug absorption. This article focuses on the various studies done to investigate the effectiveness of formulations prepared as solid-oil-water emulsions in comparison to conventional water-oil-water emulsions. A summary of the results obtained in each study is presented in this article. The s-o-w emulsion technique may become beneficial in near future as it has shown to improve the stability and efficacy of the entrapped active ingredient.

Graphical abstract

PLGA-based biodegradable microspheres in drug delivery: recent advances in research and application

Biodegradable microspheres have been widely used in the field of medicine due to their ability to deliver drug molecules of various properties through multiple pathways and their advantages of low dose and low side effects. Poly (lactic-co-glycolic acid) copolymer (PLGA) is one of the most widely used biodegradable material currently and has good biocompatibility. In application, PLGA with a specific monomer ratio (lactic acid and glycolic acid) can be selected according to the properties of drug molecules and the requirements of the drug release rate. PLGA-based biodegradable microspheres have been studied in the field of drug delivery, including the delivery of various anticancer drugs, protein or peptide drugs, bacterial or viral DNA, etc. This review describes the basic knowledge and current situation of PLGA biodegradable microspheres and discusses the selection of PLGA polymer materials. Then, the preparation methods of PLGA microspheres are introduced, including emulsification, microfluidic technology, electrospray, and spray drying. Finally, this review summarizes the application of PLGA microspheres in drug delivery and the treatment of pulmonary and ocular-related diseases.

Antimicrobial dressing of silver sulfadiazine-loaded halloysite/cassava starch-based (bio)nanocomposites

(Bio)nanocomposites have been studied for biomedical applications, including the treatment of wounds. However, wound infection is one of the main problems of wound care management, and the use of wound dressings with antibacterial agents is essential. This work focused on developing and characterizing silver sulfadiazine-loaded halloysite/cassava starch-based (bio)nanocomposites potentially suitable as antimicrobial dressing. Silver sulfadiazine was complexed inside the halloysite nanotubes lumen, and the drug-loaded nanotubes were incorporated in thermoplastic starch dispersion, forming the (bio)nanocomposites. The silver sulfadiazine-loaded halloysite and the (bio)nanocomposite were characterized by zeta potential, scanning electron microscopy, X-ray diffraction, and infrared spectroscopy. The dressing properties of (bio)nanocomposites (water vapor permeability and mechanical stability) and their antimicrobial efficacy by Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus were also evaluated. Physicochemical studies suggested the silver sulfadiazine-loaded halloysite complexation (zeta potential of -38.9 mV) and its interactions with the starch forming the nanocomposites. The silver sulfadiazine-loaded halloysite/starch-based (bio)nanocomposites possessed a homogeneous and organized structure. Also, they had mechanical properties to be used as a dressing (13.73 ± 3.09 MPa and 3.17 ± 1.28% of elongation at break), and its permeability (6.18 ± 0.43 (10^-13) g.Pa^-1.s^-1.m^-1) could be able to maintain the environmental moisture at the wound surface. Besides that, the (bio)nanocomposites acted against the studied bacteria, being a potential contact antimicrobial and biodegradable wound dressing. Finally, the developed (bio)nanocomposites are semi-occlusive and good candidates for dry wounds to be widely in vitro and in vivo tested as controlled silver sulfadiazine delivery dressing.

Layered biocompatible pH-responsive antibacterial composite film based on HNT/PLGA/chitosan for controlled release of minocycline as burn wound dressing

In the present study, a promising pH-responsive wound dressing was prepared. Halloysite nanotube (HNT) composites were modified with different concentration of both poly (lactic-co-glycolic acid) (PLGA) and chitosan (CS) through the Layer-by-Layer (LbL) strategy for targeted and controlled drug delivery of minocycline (MC). The resulting composites were characterized by FT-IR, XRD, zeta-potential, TGA, FE-SEM and TEM studies. Studying the biodegradability, water uptake, photostability, and water vapor transmission of resulting composites revealed that the composite film absorbed wound secretions, did not degrade, and penetrated properly to wound during the treatment. The results of protein adsorption showed that the optimized composite (C₄₀P₆₀MNT) was blood-compatible. Studying the release profile of the drug showed pH-responsive behavior that was fitted with Korsmeyer-Peppas kinetic model. In-vitro antibacterial testing showed that the C₄₀P₆₀MNT sample had an acceptable effect on the inhibition of gram-positive and gram-negative bacteria. In wound healing test (in-vivo studies), this MC loaded composite film showed faster healing of the burn wound in rat compare to the control sample. Due to the characteristics of the optimized sample, it can be considered as a promising candidate for pH-responsive drug delivery in the treatment of chronic burn wounds.