Interlayer expansion of octacalcium phosphate via forced oxidation of the intercalated molecules within its interlayers

Octacalcium phosphate (OCP), a precursor to apatite, has a layered structure that allows various molecules to be intercalated within its interlayers. Previous research on the phase conversion process of OCP to apatite indicated that the layered structures typically collapse due to the shrinking of the OCP layers. In contrast, this study presents a novel phenomenon involving OCP layer expansion during phase conversion. This expansion is based on a forced oxidation process of the intercalated molecules within the hydrous layers of OCP. By introducing NaClO to an OCP interlayer containing dithiodiglycolic acid (DSG), the OCP layers are expanded. This process involves DSG decomposition through its reaction with NaClO. Specifically, the process occurs when a DSG-substituted OCP (containing disulfide bonds (-S-S-)) is immersed in a NaClO solution. This is the first study to report the expansion phenomenon during the phase conversion process from OCP to apatite, providing a new perspective to the conventional understanding that these layers only shrink.

Microspheres with 2D rGO/Alginate Matrix for Unusual Prolonged Release of Cefotaxime

A synergistic interaction between reduced graphene oxide (rGO) and a biodegradable natural polymer, sodium alginate, was developed to create unique microspheres with protruding spiky features at the surface (spiky microspheres) that act as a super encapsulation and sustained release system for the highly effective antibiotic cefotaxime. Three forms of microspheres, namely alginate (Alg), alginate-cefotaxime (Alg-CTX), and alginate-cefotaxime-reduced graphene (Alg-CTX-rGO) composites, were prepared using calcium chloride as a cross-linking agent. The microspheres were characterized using field emission scanning electron microscopy (FESEM), Fourier-transform infrared (FT-IR) spectroscopy, and X-ray diffraction to investigate their pores, roughness, surface morphology, functional groups, phase formation, purity, and structural properties. The membrane diffusion method was employed to determine the release profile of Cefotaxime from the fabricated microspheres. The antibacterial activities of CTX solution, Alg microspheres, Alg-CTX microspheres, and Alg-CTX-rGO microspheres were investigated against gram-negative bacteria (Escherichia coli) using the agar diffusion method on Muller-Hinton agar. The prepared samples exhibited excellent results, suggesting their potential for enhanced antibiotic delivery. The results demonstrated the potential of the microsphere 2D rGO/alginate matrix for enhancing cefotaxime delivery with an unusual, prolonged release profile.

A pH-Controlled Solid Inhibitor Based on PAM Hydrogel for Steel Corrosion Protection in Wide Range pH NaCl Medium

To provide carbon steel a long-term corrosion protection effect in NaCl solutions with different pH values, based on poly-acrylamide (PAM) and oleate imidazoline (OIM), a solid corrosion inhibitor with the properties of pH-controlled release was synthesized. SEM, FTIR and TGA results indicated that the OIM inhibitors were successfully loaded into PAM hydrogel with a high OIM encapsulation content (39.64 wt.%). The OIM release behavior from the hydrogel structure has two stages, quick release and sustained release. The pH of solutions could affect the initial release kinetics of OIM inhibitors and the diffusion path in the hydrogel structure. Weight loss measurement of L80 steel in different pH solutions with OIM@PAM proved the inhibitor responsive release mechanism and anticorrosion performance. The inhibition efficiency of OIM@PAM can maintain over 80% after long-term immersion in a harsh corrosive environment (pH 3), which is much higher than the inhibition efficiency of OIM@PAM in a moderate corrosive solution.

Te-Cefotaxime Nanocomposites with Restored Antibiotic Susceptibility and LED Light Activated Photothermal Effect for Rapid MRSA Eradication

The ever-growing antibiotic-resistant bacteria pose a huge threat to public health. Restoring the susceptibility of ineffective antibiotics by inorganic nanomaterials and combining of photothermal and antibiotic synergistic therapy could be...

Understanding the physicochemical properties of Zn-Fe LDH nanostructure as sorbent material for removing of anionic and cationic dyes mixture

In our work, the removal of cationic and anionic dyes from water was estimated both experimentally and computationally. We check the selectivity of the adsorbent, Zn-Fe layered double hydroxide (LDH) toward three dyes. The physical and chemical properties of the synthesis adsorbent before and after the adsorption process were investigated using X-ray photoelectron spectroscopy, energy dispersive X-ray, X-ray diffraction, FT-IR, HRTEM, and FESEM analysis, particle size, zeta potential, optical and electric properties were estimated. The effect of pH on the adsorption process was estimated. The chemical stability was investigated at pH 4. Monte Carlo simulations were achieved to understand the mechanism of the adsorption process and calculate the adsorption energies. Single dye adsorption tests revealed that Zn-Fe LDH effectively takes up anionic methyl orange (MO) more than the cationic dyes methylene blue (MB) and malachite green (MG). From MO/MB/MG mixture experiments, LDH selectively adsorbed in the following order: MO > MB > MG. The adsorption capacity of a single dye solution was 230.68, 133.29, and 57.34 mg/g for MO, MB, and MG, respectively; for the ternary solution, the adsorption capacity was 217.97, 93.122, and 49.57 mg/g for MO, MB, and MG, respectively. Zn-Fe LDH was also used as a photocatalyst, giving 92.2% and 84.7% degradation at concentrations of 10 and 20 mg/L, respectively. For visible radiation, the Zn-Fe LDH showed no activity.

Layered Double Hydroxides as Promising Excipients for Drug Delivery Purposes

Layered Double Hydroxides (LDH) have received great attention in the development of drug carrier systems. LDHs have become intelligent excipients of high technological potential for the pharmaceutical industry due to their ability to intercalate biomaterials in the interlayer region, adsorb substances on its vast surface area, have flexible structure, swelling properties, high chemical and thermal stability, modulate drug release, have high biocompatibility and be easily synthesized. This article, using typical examples, mainly addresses the systems formed between LDHs and antimicrobial, antineoplastic and anti-inflammatory agents, which constitute the main pharmacological classes of wide interest due to the problems encountered with low solubility, control in administration, stability in body fluids and toxicity, among others. Additionally, the article also reports on the recent development of ternary or quaternary (multicomponent systems) compounds based on LDH, bringing the advantages of targeted therapy, improving the aqueous stability of nanohybrids and the performance of these inorganic carriers.

Chemisorption and sustained release of cefotaxime between a layered double hydroxide and polyvinyl alcohol nanofibers for enhanced efficacy against second degree burn wound infection

Zn–Al layered double hydroxides (LDHs) were synthesized by a chemical method, while polyvinyl alcohol (PVA) nanofibers were fabricated by an electrospinning approach; we also synthesized Zn–Al LDH/cefotaxime (cefotax), Zn–Al LDH@PVA, and Zn–Al LDH/cefotax@PVA (LCP). Characterizations were performed by X-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, high-resolution transmission electron microscopy, energy dispersive X-ray spectroscopy, Brunauer–Emmett–Teller analysis, thermogravimetric-differential thermal analysis techniques, dynamic light scattering, X ray-florescence, and carbon, hydrogen, and nitrogen (CHN) analyses. The adsorption isotherm of cefotax and its entrapment percentage, release, and kinetics were also investigated. The results confirmed the elemental constituents of the mentioned formulas, which exhibited different degrees of crystallinity and different morphologies. Besides, these formulas were tested in vitro as antimicrobial agents and applied in vivo against second-degree wound burns induced in rats' skin. The adsorption of cefotax occurred chemically, and the experimental data were fitted with different isotherm models, where the Freundlich and Toth models gave the best fits. The entrapment percentage in LDH/cefotax was 77.41% and in LDH/cefotax@PVA, it was 67.83%. The sustained release of cefotax from LDH and LCP was attainable; the release percentages were 89.31% and 81.55% in up to 12 h, respectively. The release kinetics of cefotax from LDH fitted well with first-order kinetics, while that for LCP was parabolic. The formulas showed uneven antimicrobial effects against Gram-positive and Gram-negative bacteria; the best effect was exhibited by Zn–Al LDH/cefotax@PVA due to its sustained release. Finally, investigating the possibility of using these formulas in the clinical setting should be considered.

This study succeeded to formulate, characterize, and investigate cefotax release and kinetics, and to compare cetofax with other known antibacterial agents.

Sustainable waste management and recycling of Zn–Al layered double hydroxide after adsorption of levofloxacin as a safe anti-inflammatory nanomaterial

Inorganic nano-layered double hydroxide (LDH) materials are used in the catalytic field, and have demonstrated great applicability in the pharmacological fields. In the current study, we report Zn–Al LDH as an adsorbent for levofloxacin (levo). The physical and chemical properties of the prepared material before and after adsorption were monitored using X-ray diffraction, Fourier-transform infrared (FT-IR) spectroscopic analysis, energy dispersive X-ray spectroscopy (EDX), Brunauer–Emmett–Teller (BET) surface area measurements, high-resolution transmission electron microscopy (HRTEM), and field emission scanning electron microscopy (FESEM). Density functional theory (DFT) calculations for levo and its protonated species were studied at the B3LYP/6-311G (d,p) level of theory. The removal percentage of levo was 73.5%. The adsorption isotherm was investigated using nine different models at pH 9, where the obtained correlation coefficients (R²) using the Redlich–Peterson and Toth models were 0.977. The thermodynamic parameters ΔS°, ΔG° and ΔH° were estimated and discussed in detail. Also, to support the adsorption research field, the applicability of the formed waste after the adsorption of levo onto Zn–Al LDH was investigated for medical purposes. The toxicity of levo in both normal and nanocomposite form was studied. Neither toxicological symptoms nor harmless effects were exhibited throughout the in vivo study. The oral anti-inflammatory activity, tested using 6% formalin to produce edema in the footpad, was manifested as a significant increase of 37% in the anti-inflammatory effect of the Zn–Al LDH/levo nanocomposite compared to levo in its normal form.

Zn-Al LDH was synthesized using the co-precipitation method, characterized and used as an efficient adsorbent for the removal of levofloxacin. The safety and toxicity of the administered Zn-AL LDH/levo as a safe anti-inflammatory material.

High and long-term antibacterial activity against Escherichia coli via synergy between the antibiotic penicillin G and its carrier ZnAl layered double hydroxide

Antibiotic-resistant bacterial infections are a global health problem. A commonly-used antibiotic Penicillin G was incorporated into ZnAl-layered double hydroxides (PNG/LDH) with a varied amount of PNG. PNG/LDH nanocomposites were well characterized in structure and composition using elemental analysis, X-ray diffraction pattern, Fourier transform infrared spectroscopy and TEM images, revealing that PNG were mostly adsorbed on the LDH surfaces at a lower PNG loading but some were intercalated into LDH interlayers at a higher PNG loading. The typical release profile of PNG and Zn²⁺ from PNG/LDH was a quick release, followed by a sustainable slow release. The antibacterial tests against Escherichia coli demonstrated that PNG/LDH with a suitable composition synergistically improved bacterial inhibition compared with free PNG and pristine LDHs. In specific, PNG/LDH with much higher cost-effectiveness showed a potent antimicrobial activity and maintained the activity for up to 10 days, significantly elongating the antibacterial effect compared with just 1 day for free PNG in the same conditions. Our results suggest suitable composition of nanoparticle carriers and antibiotics could significantly enhance antibacterial activity of antibiotics for a long period via the synergistic effect between carrier and antibiotics, a potential approach to overcome the bacterial resistance to antibiotics.

Structural and morphological aspects of (fluoro)quinolone delivery by layered double hydroxide nanoparticles

Synthesis conditions affect the composition and morphology of LDH-based delivery systems loaded with nalidixic acid and, consequently, their biopharmaceutical behavior.