Intercalation and controlled release of pharmaceutically active compounds from a layered double hydroxide

Photochemical Consideration in the Interactions between Blood Proteins and Layered Inorganic Materials

Interactions between layered double hydroxide (LDH) nanomaterials and plasma proteins according to their particle size and surface charge were evaluated. The LDHs with different particle size (150, 350 and 2000 nm) were prepared by adjusting hydrothermal treatment and urea hydrolysis and subsequent organic coating with citrate, malite and serite was applied to control the surface charge (ζ-potential: −15, 6 and 36 mV). Adsorption isotherms and Stern–Volmer plots for fluorescence quenching indicated that the human blood plasma had weak interactions toward all the types of LDHs. The adsorption isotherms did not show significant differences in the size and surface charges, while the fluorescence quenching ratio increased with the increase in the surface charge, implying that electrostatic interaction played a major role in their interactions. The fluorescence quenching of three types of plasma proteins (human serum albumin, γ-globulin and fibrinogen) by the surface charge-controlled LDHs suggested that the proteins adsorbed on the LDHs with a single layer and additional proteins were weakly adsorbed to surround the LDHs with adsorbed proteins. It was concluded that the LDH nanomaterials are fairly compatible for blood components due to the protein corona while the electrostatic interaction can affect their interaction with the proteins.

Anti-Inflammatory and Analgesic Evaluation of a Phytochemical Intercalated into Layered Double Hydroxide

Coumaric acid (CouH), an antioxidant molecule assimilated by food consumption, was intercalated into layered double hydroxide (LDH) nanocarrier, having zinc and aluminium ions in the layers (LDH-Cou), to evaluate its pharmacological activity through in vitro and in vivo assays in mice. Therefore, the following tests were performed: coumarate delivery in saline solution, fibroblasts’ cell viability using neutral red, peritonitis induced by carrageenan, formalin test, acetic-acid-induced writhing, and tail-flick assay, for the non-intercalated CouH and the intercalated LDH-Cou system. Furthermore, different pharmacological pathways were also investigated to evaluate their possible anti-inflammatory and antinociceptive mechanisms of action, in comparison to traditionally used agents (morphine, naloxone, caffeine, and indomethacin). The LDH-Cou drug delivery system showed more pronounced anti-inflammatory effect than CouH but not more than that evoked by the classic non-steroidal anti-inflammatory drug (NSAID) indomethacin. For the analgesic effect, according to the tail-flick test, the treatment with LDH-Cou expressively increased the analgesia duration (p < 0.001) by approximately 1.7−1.8 times compared to CouH or indomethacin. Thus, the results pointed out that the LDH-Cou system induced in vivo analgesic and anti-inflammatory activities and possibly uses similar mechanisms to that observed for classic NSAIDs, such as indomethacin.

Periodic charge matching driven immobilization of gentamicin in nanoclays for stable and long-term antibacterial coating

Matching of charge periodicity between a guest and a host enabled effective immobilization of highly water-soluble antibiotic drug, gentamicin C, in a bentonite clay by cation exchange. X-ray diffraction, infrared spectroscopy and CHNS analysis revealed the immobilization manner of gentamicin C, which was immobilized between bentonite layers via periodic charge-charge interaction with tilted arrangement, as a trication. Both gentamicin alone and a gentamicin/bentonite hybrid were coated onto a polyurethane substrate using water-borne polyurethane binder. The antibiotic character of both films was investigated as prepared or after immersion in phosphate-buffered saline till 5 days against E. coli and B. subtilis bacteria. It was clearly shown that the gentamicin/bentonite hybrid-coated film showed sustained antibacterial efficacy even after exposure to phosphate-buffered saline, while gentamicin only-coated film gradually lost its performance under the same condition.

Synthesis and characterization of hybrid nanocarrier layered double hydroxide grafted by polyethylene glycol and gemcitabine

For the past few years, organic-inorganic hybrid nanocarriers have been widely explored for effective drug delivery and preferable disease treatments. In this article, hydrothermal method was utilized to prepare fine dispersed layered double hydroxide (Mg-Al LDH) suspension. Polyethylene glycol (PEG) was grafted on the surface of LDH lamella in order to improve the dispersibility of LDH. Besides, the anti-cancer drug gemcitabine was grafted on the surface of LDH lamellas through chemical grafting. Hence a novel new type of organic-inorganic hybrid drug delivery system LDH-mPEG-Gemcitabine was obtained. In addition, the siRNA was intercalated into the LDH interlamination by ion exchange method to realize drug and gene co-delivery. The loading capacity of LDH and LDH-mPEG-Gemcitabine was evaluated by agarose gel electrophoresis. The characterization by laser particle size analyzer, TEM, FT-IR, XRD, in vitro cell viability and in vitro drug release demonstrated that LDH-mPEG-Gemcitabine possessed fine dispersibility, uniform morphology and particle size, fine biocompatibility, ideal drug loading and releasing capacity and held great potential to be used as a desired co-delivery system for drug and gene.

Effect of Drying on the Fabrication of MgAl Layered Double Hydroxides

This study aimed to evaluate the synthesis of MgAl/LDH from the drying process perspective, evaluating the influence of temperature (75-90 °C) and time (16-20 h) in the drying process. The synthesis was performed, maintaining a ratio of 2:1 of Mg/Al, and the drying was conducted according to a 2² experimental design: four axial points and three repetitions at the central point. The surface area and pore diameter ranged from 4.09 to 18.55 m²/g and 12.50 to 24.46 nm. Fourier transform infrared (FTIR) analysis indicated the drying-caused variation of the LDH typical bands intensities. Scanning electron microscopy (SEM) images showed the tendency of the increase of agglomeration with the temperature elevation. The drying parameters' influence was evident for X-ray diffraction (XRD) analysis observing the crystallite size increment, from 13.10 to 38.94 nm, and basal spacing variation, from 7.52 to 7.64 Å. The statistical models for growing crystal and reduction of the basal spacing were physically consistent but with low values of R ². The drying time and temperature had a considerable influence on the chemical, physical, structural, and morphological properties of LDH.

Preparation of ammonium polyphosphate and dye co-intercalated LDH/polypropylene composites with enhanced flame retardant and UV resistance properties

In this paper, ammonium polyphosphate (APP) with flame retardant performance and acid red 88 (AR88) with UV absorption property were intercalated into layered double hydroxide (LDH) interlayers together, aiming to improve the flame retardancy and UV resistance properties of polypropylene (PP) simultaneous in one system. The synthesized LDHs and PP/LDH composites were characterized systematically and the results showed that AR88 and APP were intercalated into LDH interlayers successfully, and the content of APP and AR88 in LDH interlayers can be controlled through the synthesis process. Both APP-LDHs and AR88/APP-LDHs can greatly improve the flame retardancy performance of PP, with 25 wt% LDH addition, the peak heat release rate (PHRR) decreased by 42-63%, respectively. Temperature at 50% mass loss (T₅₀) of PP also increased to some extent. In addition, the intercalation of AR88 in LDH also possessed good UV adsorption which can delay the ageing of PP during their use. Thus, a new approach to improve both flame retardant and UV resistance properties for polymers at the same time is achieved.

Engineering atorvastatin loaded Mg-Mn/LDH nanoparticles and their composite with PLGA for bone tissue applications

The impact of mixing method in conventional co-precipitation synthesis of layered double hydroxides (LDHs), on particle size, size distribution and drug loading capacity is reported. Synthesis of Mg (II)/Mn (III)-LDH nano-platelets was performed at constant pH using three different mixing systems, magnetic stirrer, mechanical mixer, and homogenizer at ambient temperature and a fixed Mg/Mn ratio of 3/1. The LDH characterization results showed that mechanical mixing and homogenization lead to production of very fine LDH nano-platelets (about 90-140 nm), with narrow particle size distribution. Amount of the intercalated drug was determined as about 60% and showed a significant increase in loading capacity of the LDH through homogenization and mechanical mixing compared to that of the magnetic stirring (about 35%). Our results also showed that in LDH preparation via co-precipitation, the mixing system plays a more influential role in particle size, size distribution, and drug loading control, than the mixing speed of each system. Drug loaded-LDH/PLGA composites were prepared via electrospinning to afford a bioactive/osteoinductive scaffold. A remarkable degree of cell viability on the scaffolds (drug-loaded-LDH/PLGA composite) was confirmed using MTT assay. Osteogenic differentiation of human ADMSCs, as shown by alkaline phosphatase activity and Alizarin Red staining assays, indicated that the scaffold with 5% drug loaded LDH(Mn-Mg-LDH/PLGA/AT5%) induced a remarkably higher level of the markers compared to the PLGA scaffold and therefore, it could be a valuable candidate for bone tissue engineering applications.

Eu3+-doped layered gadolinium hydroxides as drug carriers and their bactericidal behavior

Layered rare earth hydroxides (LRHs) due to outstanding photoluminescence (PL) properties and anion exchangeability are extensively reported in multiple fields. In this work, the drug-loaded and bactericidal behaviors of Eu³⁺-doped layered gadolinium hydroxides (LGdHs:Eu) as optical carriers were explored through intercalation and release of cephalexin (CE). In the intercalation state, the PL intensity of CE--LGdHs:Eu obviously decreased because of the quenching effect of CE-. And the PL intensity of LGdHs:Eu was restored with the release of CE- ions in phosphate buffer solutions (PBS). A significant functional relationship between the drug releasing amount and PL intensity ratio was found, providing a novel optical method to specify the drug dosage. And CE--LGdHs:Eu showed the excellent bactericidal properties in both in vivo and in vitro experiments.

A review on optical sensors based on layered double hydroxides nanoplatforms

In recent years, significant efforts have been devoted towards the fabrication and application of layered double hydroxides (LDHs) due to their tremendous features such as excellent biocompatibility with negligible toxicity, large surface area, high conductivity, excellent solubility, and ion exchange properties. Most impressive, LDHs offer a favorable environment to attach several substances such as quantum dots, fluorescein dyes, proteins, and enzymes, which leads to strengthening the catalytic properties or increasing the sensing selectivity and sensitivity of the resulted hybrids. With the extensive ongoing research on the application of nanomaterials, many studies have led to remarkable achievements in exploring LDHs as sensing nanoplatforms. In optical sensors, for instance, many sensing strategies were tailored based on the enzyme-mimicking properties of LDHs, including colorimetric and chemiluminescence procedures. Meanwhile, others were designed based on intercalating some fluorogenic substrates on the LDHs, whereby the sensing signal can be acquired by quenching or enhancing their fluorescence after the addition of analytes. In this review, we aim to summarize the recent advances in optical sensors that use layered double hydroxides as sensing platforms for the determination of various analytes. By outlining some representative examples, we accentuate the change of spectral absorbance, chemiluminescence, and photoluminescence phenomena triggered by the interaction of LDH or functionalized-LDH with the indicators and analytes in the system. And finally, current limitations and possible future orientation in designing further LDHs-based optical sensors are presented. It is hoped that this review will be helpful in assisting the establishment of more improved sensors based on LDHs features. Optical sensors based on layered double hydroxides (LDHs) nanoplatforms were reviewed. The sensing system and detection approaches were rationally reviewed. Possible future orientations were highlighted.

Synthesis of Layered Double Hydroxides Intercalated With Drugs for Controlled Release: Successful Intercalation of Ibuprofen and Failed Intercalation of Paracetamol

This work examines the effect of drug structure and ionization degree on the formation and properties of biocompatible layered double hydroxides (LDH) intercalated with ibuprofen and paracetamol. Ibuprofen (pKa = 5.3) is in its anionic form, whereas paracetamol (pKa 9.4) is only partially ionized at the synthesis pH (9.0), and thus intercalation is expected to be different in the two cases. Chemical analyses, X-ray diffraction, electron microscopy, infrared spectroscopy and thermal analyses were applied to characterize the materials. Dissolution kinetics and drug release kinetics were also investigated, in an ample range of pH (3.0-9.0) in NaCl solutions, and in physiological buffers (1.2, 4.5 and 6.8). All characterization techniques showed that an efficient intercalation of ibuprofen took place, resulting in a material with 30% of its weight corresponding to the drug. On the contrary, all techniques revealed a very poor intercalation of paracetamol (1.2%). The dissolution kinetics of LDHs was highly pH-dependent, being higher as pH decreased. The drug release kinetics, conversely, increased as pH increased. In physiological buffers the release rate depended not only on the pH but also on the type of buffer. This last behavior is useful to control the release in different parts of the digestive system.

Towards the Continuous Hydrothermal Synthesis of ZnO@Mg2Al-CO3 Core-Shell Composite Nanomaterials

Core-shell Zinc Oxide/Layered Double Hydroxide (ZnO@LDH) composite nanomaterials have been produced by a one-step continuous hydrothermal synthesis process, in an attempt to further enhance the application potential of layered double hydroxide (LDH) nanomaterials. The synthesis involves two hydrothermal reactors in series with the first producing a ZnO core and the second producing the Mg₂Al-CO₃ shell. Crystal domain length of single phase ZnO and composite ZnO was 25 nm and 42 nm, respectively. The ZnO@LDH composite had a specific surface area of 76 m² g⁻¹, which was larger than ZnO or Mg₂Al-CO₃ when produced separately (53 m² g⁻¹ and 58 m² g⁻¹, respectively). The increased specific surface area is attributed to the structural arrangement of the Mg₂Al-CO₃ in the composite. Platelets are envisaged to nucleate on the core and grow outwards, thus reducing the face–face stacking that occurs in conventional Mg₂Al-CO₃ synthesis. The Mg/Al ratio in the single phase LDH was close to the theoretical ratio of 2, but the Mg/Al ratio in the composite was 1.27 due to the formation of Zn₂Al-CO₃ LDH from residual Zn²⁺ ions. NaOH concentration was also found to influence Mg/Al ratio, with lower NaOH resulting in a lower Mg/Al ratio. NaOH concentration also affected morphology and specific surface area, with reduced NaOH content in the second reaction stage causing a dramatic increase in specific surface area (> 250 m² g⁻¹). The formation of a core-shell composite material was achieved through continuous synthesis; however, the final product was not entirely ZnO@Mg₂Al-CO₃. The product contained a mixture of ZnO, Mg₂Al-CO₃, Zn₂Al-CO₃, and the composite material. Whilst further optimisation is required in order to remove other crystalline impurities from the synthesis, this research acts as a stepping stone towards the formation of composite materials via a one-step continuous synthesis.

Novel fluoride rechargeable dental composites containing MgAl and CaAl layered double hydroxide (LDH)

OBJECTIVE

This study aims to incorporate 2:1 MgAl and 2:1 CaAl layered double hydroxides (LDHs) in experimental dental-composites to render them fluoride rechargeable. The effect of LDH on fluoride absorption and release, and their physico-mechanical properties are investigated.

METHODS

2:1 CaAl and 2:1 MgAl LDH-composite discs prepared with 0, 10 and 30wt% LDH were charged with fluoride (48h) and transferred to deionized water (DW)/artificial saliva (AS). Fluoride release/re-release was measured every 24h (ion-selective electrodes) with DW/AS replaced daily, and samples re-charged (5min) with fluoride every 2 days. Five absorption-release cycles were conducted over 10 days. CaAl and MgAl LDH rod-shaped specimens (dry and hydrated; 0, 10 and 30wt%) were studied for flexural strength and modulus. CaAl and MgAl LDH-composite discs (0, 10, 30 and 45wt% LDH) were prepared to study water uptake (over 7 weeks), water desorption (3 weeks), diffusion coefficients, solubility and cation release (ICP-OES).

RESULTS

CaAl LDH and MgAl LDH-composites significantly increased the amount of fluoride released in both media (P<0.05). In AS, the mean release after every recharge was greater for MgAl LDH-composites compared to CaAl LDH-composites (P<0.05). After every recharge, the fluoride release was greater than the previous release cycle (P<0.05) for all LDH-composites. Physico-mechanical properties of the LDH-composites demonstrated similar values to those reported in literature. The solubility and cation release showed a linear increase with LDH loading.

SIGNIFICANCE

LDH-composites repeatedly absorbed/released fluoride and maintained desired physico-mechanical properties. A sustained low-level fluoride release with LDH-composites could lead to a potential breakthrough in preventing early stage carious-lesions.

Active anti-corrosion of epoxy coating by nitrite ions intercalated MgAl LDH

Layered double hydroxide (LDH) with NO₂^- intercalation was successfully prepared via acidification oscillation and ion exchange. The nano-fillers were incorporated into the resin to prepare anti-corrosion coatings with the thickness of ca. 50 ± 5 μm. The electrochemical and self-repairing properties of the LDH-doped coatings were studied by EIS and LEIS. Results indicated that the addition of LDH loaded with nitrite induced obvious increased in the impedance of coating (from 4.64 × 10⁸ Ω cm² to 2.14 × 10¹⁰ Ω cm²) and improved the anticorrosion performance of the coating. In addition, the localized corrosion of coatings could be largely inhibited, and the released nitrite ions from LDH interlayers exhibited active anticorrosion functions. When LDH nanosheets were added to the coatings, the lamella structures improved the barrier performances of the coatings. At the same time, the excellent ion exchanges ability of LDH could be used as storage stations for chloride ions, and the release of nitrite ions could play an active anti-corrosion role. Both of them cooperated to synergistically improve the anti-corrosion performance of the coating.

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.

Hydrotalcite–PLGA composite nanoparticles for loading and delivery of danshensu

As one of the main pharmacodynamic components present in the water-soluble components of Salvia miltiorrhiza (Danshen), danshensu (DSS) is applicable to treating cardiovascular diseases.

Incorporation of Glycine max Merrill Extract into Layered Double Hydroxide through Ion-Exchange and Reconstruction

We incorporated extract of Glycine max Merrill (GM), which is generally known as soybean, into a layered double hydroxide (LDH) nanostructure through two different methods, ion-exchange and reconstruction. Through X-ray diffraction, field-emission scanning electron microscopy, and zeta-potential measurement, GM moiety seemed to be simply attached on the surface of LDH by ion-exchange process, while the extract could be incorporated in the inter-particle pore of LDHs by reconstruction reaction. The quantification exhibited that both incorporation method showed comparable extract loading capacity of 15.6 wt/wt% for GM-LDH hybrid prepared by ion-exchange (GML-I) and 18.6 wt/wt% for GM-LDH hybrid by reconstruction (GML-R). On the other hand, bioactive substance in both GM-LDH hybrids, revealed that GML-R has higher daidzein content (0.0286 wt/wt%) compared with GML-I (0.0108 wt/wt%). According to time-dependent daidzein release, we confirmed that GML-R showed pH dependent daidzein release; a higher amount of daidzein was released in pH 4.5 physiological condition than in pH 7.4, suggesting the drug delivery potential of GML-R. Furthermore, alkaline phosphatase activity and collagen fiber formation on human osteoblast-like MG-63 cells displayed that GML-R had superior possibility of osteoblast differentiation than GML-I. From these results, we concluded that reconstruction method was more effective for extract incorporation than ion-exchange reaction, due to its pH dependent release property and alkaline phosphatase activity.

Layered Double Hydroxide Fluoride Release in Dental Applications: A Systematic Review

This systematic review appraises studies conducted with layered double hydroxides (LDHs) for fluoride release in dentistry. LDH has been used as antacids, water purification in removing excess fluoride in drinking water and drug delivery. It has great potential for controlled fluoride release in dentistry, e.g., varnishes, fissure sealants and muco-adhesive strips, etc. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) Statement was followed with two reviewers performing a literature search using four databases: PubMed, Web of Science, Science Direct and Ovid Medline with no date restrictions. Studies including any LDH for ion/drug release in dentistry were included, while assessing the application of LDH and the value of the methodology, e.g., ion release protocol and the LDH production process. Results: A total of 258 articles were identified and four met the inclusion criteria. Based on two in vitro studies and one clinical study, LDH was previously studied in dental materials, such as dental composites and buccal muco-adhesive strips for fluoride release, with the latter studied in a clinical environment. The fourth study analysed LDH powder alone (without being incorporated into dental materials). It demonstrated fluoride release and the uptake of volatile sulphur compounds (VSC), which may reduce halitosis (malodour). Conclusion: LDHs incorporated in dental materials have been previously evaluated for fluoride release and proven to be clinically safe. LDHs have the potential to sustain a controlled release of fluoride (or other cariostatic ions) in the oral environment to prevent caries. However, further analyses of LDH compositions, and clinical research investigating any other cariostatic effects, are required.

Emerging switchable ultraviolet photoluminescence in dehydrated Zn/Al layered double hydroxide nanoplatelets

Layered double hydroxides show intriguing physical and chemical properties arising by their intrinsic self-assembled stacking of molecular-thick 2D nanosheets, enhanced active surface area, hosting of guest species by intercalation and anion exchanging capabilities. Here, we report on the unprecedented emerging intense ultraviolet photoluminescence in Zn/Al layered double hydroxide high-aspect-ratio nanoplatelets, which we discovered to be fully activated by drying under vacuum condition and thermal desorption as well. Photoluminescence and its quenching were reproducibly switched by a dehydration–hydration process. Photoluminescence properties were comprehensively evaluated, such as temperature dependence of photoluminescence features and lifetime measurements. The role of 2D morphology and arrangement of hydroxide layers was demonstrated by evaluating the photoluminescence before and after exfoliation of a bulk phase synthetized by a coprecipitation method.

Preparation of Layered Double Hydroxides toward Precisely Designed Hierarchical Organization

Layered double hydroxides (LDHs) are a class of materials with useful properties associated with their anion exchange abilities for a wide range of materials’ applications including adsorbent, catalyst and its support, ceramic precursor, and drug carrier. In order to satisfy the requirements for the detailed characterization and the practical application, the preparation of LDHs with varied composition and particle morphology has been examined extensively. The versatility of the preparation methods led LDHs with varied composition and micro/macroscopic morphology, which makes the application of LDHs more realistic. In the present review article, synthetic methods of LDHs are overviewed in order to highlight the present status of the LDHs for practical application.

One-step synthesis and growth mechanism of nitrate intercalated ZnAl LDH conversion coatings on zinc

An approach for the synthesis of ZnAl-NO3 LDH conversion coatings on zinc in an aqueous acidic Al(NO3)3/NaNO3 solution is demonstrated for the first time. The growth mechanism has been investigated using time resolved structural, microstructural and analytical methods. A LDH growth model involving both electrochemical and chemical processes is suggested.

Cerium-doped β-Ni(OH)2 hexagon nanosheets: an effective photocatalyst for the degradation of the emerging water pollutant, naproxen

Nickel hydroxide β-Ni(OH)₂ hexagonal nanosheets were synthetized via a hydrothermal exfoliation process. The practical microwave-assisted hydrothermal method facilitated obtaining layered nickel 3D nanoplates with cerium functionalization in 5 h. The as-produced nanostructures were characterized by XRD, XPS, FESEM, FTIR, PL, UV-vis, and BET techniques. The hydroxilated structures are nano-thick hexagonal plates with sides 28 nm in length and an average thickness of 5 nm. UV and PL irradiation was used to study the photoactive properties in the degradation of a pharmaceutical emerging pollutant, naproxen. UV-vis spectroscopy and high-performance liquid chromatography monitoring indicated that the Ni(OH)₂-Ce nanostructures are an effective photocatalyst for naproxen degradation, including 40% mineralization of this highly recalcitrant drug. The photocatalyst showed stability for two consecutive cycles, preserving its photoactive and structural characteristics. Ce³⁺-doped nanoplates and surface functionalized Ce⁴⁺ act as charge separators and scavenging agents for the enhanced photodegradation of naproxen.

Influences of Cation Ratio, Anion Type, and Water Content on Polytypism of Layered Double Hydroxides

Layered double hydroxides (LDHs) are a significant sink of anions (CO₃^2-, SO₄^2-, NO₃^-, Cl^-, etc.) and divalent transition-metal cations in soil. The anion exchange capacity gives rise to functional materials. The stability of LDHs is determined by the interaction between cation-bearing layers and intercalated water and anions, which is correlated with polytypism and coordination structure. A systematic investigation is performed to show the influence of cation ratio, anion type, and water content on polytypism, swelling behavior, and interlayer structure of Mg-Al-LDHs using molecular dynamics simulations. LDHs intercalated with NO₃^- ions exhibit a polytype transition from 3 R₁ (three-layer rhombohedral polytype) to 1 T (one-layer trigonal polytype) with increasing water content. NO₃^- ions exhibit a D_{3 h} point group symmetry at low water contents. The polytype transition coincides with the complete transformation into tilted NO₃^- ion with a C_{2 v} point group symmetry. The transition appears at a lower water content when the Mg/Al ratio is lower. LDHs with SO₄^2- ions exhibit a three-stage polytypism. The first and last stages are 3 R₁. The intermediate stage could be 1 T or a mixture of different O(octahedra)-type interlayers, which depends on the cation ratio. The relative popularity of SO₄^2- ions with a C _s point group symmetry is characteristic for the intermediate stage, while mostly SO₄^2- ions exhibit a C_{3 v} symmetry. There is no clear relevance between cation ratio and water content at which a polytype transition happens. The configurational adjustments of NO₃^- and SO₄^2- ions facilitate the swelling behavior of LDHs. LDHs with CO₃^2- or Cl^- ions always maintain a 3 R₁ polytype irrespective of water content and hardly swell. The configurations of anions and water reflect local coordination structure due to hydrogen bonds. The layer-stacking way influences long-ranged Coulombic interactions. Hydrogen-bonding structure and long-ranged Coulombic interactions collectively determine polytypism and stability of LDHs.

Optimization of Formulations Consisting of Layered Double Hydroxide Nanoparticles and Small Interfering RNA for Efficient Knockdown of the Target Gene

Layered double hydroxide (LDH) nanoparticles (NPs) are safe and effective vectors for small interfering RNA (siRNA) delivery. However, it is unclear whether there are optimal parameters for the efficient delivery of functional siRNA using LDH NPs. In this research, we comprehensively examined the effect of parameters, such as the mixing method and LDH/siRNA mass ratio on siRNA silencing capability. We first noted that the best way for loading gene segments (25 bp dsDNA and siRNA) is to add gene molecules to 100 nm LDH and then diluting in Dulbecco's modified Eagle's medium. Very interestingly, the optimal LDH/gene mass ratio is around 20:1 in terms of cellular uptake amount of gene segments, whereas this ratio is shifted to around 5:1 in terms of target gene silencing efficacy, which has been reasonably explained. The optimization for LDH NP-based gene delivery system may provide the guidance for more efficient in vitro and in vivo siRNA delivery using the optimal parameters.

Layered Double Hydroxide-Based Functional Nanohybrids as Controlled Release Carriers of Pharmaceutically Active Ingredients

The chemical stability, degradation and penetration ability of pharmaceutically active ingredients in topical formulations are the greatest challenges because of problems with the protection of actives for long times and with delivery. Therefore, the development of unique and efficient substrate material is vital for their protection and controlled drug release. Layered double hydroxides (LDHs) known as hydrotalcite like compounds possess positive charges due to isomorphic substitutions, which are counterbalanced by hydrated exchangeable anions located in the interlayer region. Some of the active ingredient molecules can be intercalated into the inner region of the LDHs through ionic bonding, hydrogen bonding or van der Waals interaction to form nanohybrids, which are more potent for their protection and controlled-release. This account focuses on our recent research efforts and key scientific and technical challenges in the development of LDH based nanohybrids for commercial use in advanced controlled release carriers of active ingredients in topical formulations.

Layer like porous materials with hierarchical structure

Many chemical compositions produce layered solids consisting of extended sheets with thickness not greater than a few nanometers. The layers are weakly bonded together in a crystal and can be modified into various nanoarchitectures including porous hierarchical structures. Several classes of 2-dimensional (2D) materials have been extensively studied and developed because of their potential usefulness as catalysts and sorbents. They are discussed in this review with focus on clays, layered transition metal oxides, silicates, layered double hydroxides, metal(iv) phosphates and phosphonates, especially zirconium, and zeolites. Pillaring and delamination are the primary methods for structural modification and pore tailoring. The reported approaches are described and compared for the different classes of materials. The methods of characterization include identification by X-ray diffraction and microscopy, pore size analysis and activity assessment by IR spectroscopy and catalytic testing. The discovery of layered zeolites was a fundamental breakthrough that created unprecedented opportunities because of (i) inherent strong acid sites that make them very active catalytically, (ii) porosity through the layers and (iii) bridging of 2D and 3D structures. Approximately 16 different types of layered zeolite structures and modifications have been identified as distinct forms. It is also expected that many among the over 200 recognized zeolite frameworks can produce layered precursors. Additional advances enabled by 2D zeolites include synthesis of layered materials by design, hierarchical structures obtained by direct synthesis and top-down preparation of layered materials from 3D frameworks.

NIR absorbing Au nanoparticle decorated layered double hydroxide nanohybrids for photothermal therapy and fluorescence imaging of cancer cells

Among inorganic nanomaterials, layered double hydroxides (LDHs) and gold nanoparticles (Au NPs) have received great attention in nanobiomedicine due to their unique properties. In this work, we have designed a nanohybrid of an LDH with Au NPs (LDH-Au) in order to use it for photothermal therapy, and optical and fluorescence imaging of cancer cells. The structural characteristics of the nanohybrid are investigated using X-ray diffraction, infrared spectroscopy, electron microscopy and elemental analyses. The extinction spectra of the nanohybrid exhibits broad absorption ranging from the visible to near infrared (NIR) region (500-1000 nm). The photothermal activity of the nanohybrid is explored using NIR laser irradiation. The electric field enhancement in the nanohybrid due to the interaction of Au NPs on the LDH is speculated through finite-difference time-domain (FDTD) calculations. The LDH-Au nanohybrid is found to be biocompatible with normal murine fibroblast (L929), human breast cancer (MCF-7) and cervical cancer (HeLa) cell lines up to a concentration of 1 mg mL^-1. The nanohybrid is explored for in vitro photothermal therapy of MCF-7 and HeLa cell lines. As a photothermal agent, the nanohybrid shows that 10 min exposure to an 808 nm laser (500 mW) is adequate to inhibit about 70% of cancer cells. Further, the nanohybrid is tagged with FITC to study both optical and fluorescence imaging with MCF-7 cell lines. The results demonstrate that the LDH-Au nanohybrid provides an innovative approach to photothermal therapy, and optical and fluorescence imaging of cancer cells.

Electrospun organic–inorganic nanohybrids as sustained release drug delivery systems

Novel organic–inorganic nanohybrids have been prepared, and are found to provide long-term extended drug release.

Two-Dimensional Materials Beyond Graphene: Emerging Opportunities for Biomedicine

With the rise of graphene, there is growing attention on two-dimensional (2D) materials in the physical science community during the last decade. Most studies to date focus on the rich set of their superior electrical, optical, catalytic and electrochemical properties and highlight the encouraging opportunities for developing next generation electronics, optoelectronics, catalysis, and energy storage technologies. On the contrary, the biomedicine community has barely recognized the potential of these materials other than graphene. There are very limited published studies on these materials’ biological effects and biomedical applications. Here, we present a brief overview of 2D materials and discuss their potential for biomedical applications in hope of raising biomedical researchers’ awareness of the great opportunities associated with these materials. We first discuss the emergence of 2D materials and review two most important prerequisites for 2D materials’ biomedical applications, synthesis and biocompatibility. We then categorize the existing studies on 2D materials’ biomedical applications into biosensing, drug/gene delivery, antimicrobial, bioimaging and multimode therapeutic applications. We would put special emphasis on the great flexibility of various rational combinations of 2D material superior properties for the design and construction of assorted forms of reagents or devices with highly effective simultaneous diagnostic and therapeutic functions (or theranostics functions). At last, the newly emerging 2D black phosphorous with very rare and interesting properties is introduced as the next promising and important 2D materials to study in the upcoming years.

A luminescent ultrathin film with reversible sensing toward pressure

A flexible ultrathin film based on alternate assembly of a sodium polyacrylate (PAA) modified styrylbiphenyl derivative (BTBS) and layered double hydroxide nanosheets is fabricated, which exhibits pressure-responsive photoluminescence with a high sensitivity and good reversibility.

Accessing the biocompatibility of layered double hydroxide by intramuscular implantation: histological and microcirculation evaluation

Biocompatibility of layered double hydroxides (LDHs), also known as hydrotalcite-like materials or double metal hydroxides, was investigated by in vivo assays via intramuscular tablets implantation in rat abdominal wall. The tablets were composed by chloride ions intercalated into LDH of magnesium/aluminum (Mg2Al-Cl) and zinc/aluminum (Zn2Al-Cl). The antigenicity and tissue integration capacity of LDHs were assessed histologically after 7 and 28 days post-implantation. No fibrous capsule nearby the LDH was noticed for both materials as well any sign of inflammatory reactions. Sidestream Dark Field imaging, used to monitor in real time the microcirculation in tissues, revealed overall integrity of the microcirculatory network neighboring the tablets, with no blood flow obstruction, bleeding and/or increasing of leukocyte endothelial adhesion. After 28 days Mg2Al-Cl promoted multiple collagen invaginations (mostly collagen type-I) among its fragments while Zn2Al-Cl induced predominantly collagen type-III. This work supports previous results in the literature about LDHs compatibility with living matter, endorsing them as functional materials for biomedical applications.

Toxicity and Biomedical Imaging of Layered Nanohybrids in the Mouse

Layered nanohybrids (LNH) are a promising nonviral system allowing controlled drug and DNA delivery. In order to test the toxicity of LNH consisting of a magnesium/aluminum core, mice were subjected to subcutaneous, intraperitoneal, and intravenous injections of these nanoparticles at three doses. Intravenous injections resulted in 8% (1 out of 12) lethality at doses 100 μl and 200 μl of 6.96 × 10−4 M solution, while all mice survived after LNH administration by any other routes. Histopathological alterations were limited to mild localized inflammatory lesions in the lungs and the dermis after intravenous and subcutaneous administration, respectively. LNH labeled with Lucifer Yellow were readily detectable in both locations by fluorescent microscopy. To test their potential for intravital imaging, LNH-Lucifer Yellow were injected into the ovarian bursa and successfully visualized by multiphoton microscopy within the ovarian surface epithelial cells. In similar experiments, the ovary and the ovarian bursa were readily detectable by magnetic resonance imaging after administration of modified LNH, where aluminum was substituted for gadolinium. Taken together, these results demonstrate minimal in vivo toxicity of LNH and illuminate their potential as multifunctional nanoscale particles suitable for combination of intravital biomedical imaging with controlled drug release.

A novel platform designed by Au core/inorganic shell structure conjugated onto MTX/LDH for chemo-photothermal therapy

A novel platform making up of methotrexate intercalated layered double hydroxide (MTX/LDH) hybrid doped with gold nanoparticles (NPs) may have great potential both in chemo-photothermal therapy and the simultaneous drug delivery. In this paper, a promising platform of Au@PDDA-MTX/LDH was developed for anti-tumor drug delivery and synergistic therapy. Firstly, Au NPs were coated using Layer-by-Layer (LbL) technology by alternate deposition of poly (diallyldimethylammonium chloride) (PDDA) and MTX molecules, and then the resulting core-shell structures (named as Au@PDDA-MTX) were directly conjugated onto the surface of MTX/LDH hybrid by electrostatic attraction to afford Au@PDDA-MTX/LDH NPs. Here MTX was used as both the agent for surface modification and the anti-tumor drug for chemotherapy. The platform of Au@PDDA-MTX/LDH NPs not only had a high drug-loading capacity, but also showed excellent colloidal stability and interesting pH-responsive release profile. In vitro drug release studies demonstrated that MTX released from Au@PDDA-MTX/LDH was relatively slow under normal physiological pH, but it was enhanced significantly at a weak acidic pH value. Furthermore, the combined treatment of cancer cells by using Au@PDDA-MTX/LDH for synergistic hyperthermia ablation and chemotherapy was demonstrated to exhibit higher therapeutic efficacy than either single treatment alone, underscoring the great potential of the platform for cancer therapy.