Solid-state Characterization Research Articles

Optimized freeze-dried solid-dispersions boost naringin solubility, antibacterial and in-vitro anticancer activity

Naringin (NRG) is a water insoluble glycoside having wide range of therapeutic efficacy. Its efficacy is limited due to its poor water solubility and bioavailability. In the current research, solid dispersions (SDs) were prepared by freeze drying method using different carriers KollidonVA64, KollidonVA30, Soluplus and Poloxamer188. The prepared binary SDs were characterized for solubility and dissolution study to select the optimized composition and further ternary SDs was prepared with carrier blend (KollidonVA64 and Soluplus). Finally, the ternary SDs (F6) was evaluated for solid state characterization (DSC, XRD, SEM), drug polymer interaction (IR), in vitro antioxidant, antimicrobial as well as cell viability study against neuroblastoma cell. The binary SDs developed with KollidonVA64 and Soluplus showed greater solubility than KollidonVA30 and Poloxamer188. The ternary SDs (F6), showed a significant enhancement in the saturation solubility and dissolution than binary SDs (F1-F4). The binary SDs (F1-F4) displayed the maximum release in 120 min (73.5±2.8 to 94.6±3.1%), whereas the ternary SDs (F6) showed the maximum release in 60 min (99.2±1.6%). The spectroscopy results confirm the formation of a stable dispersion and no drug polymer interaction was observed. The thermogram, diffractogram and microscopic image confirms the conversion of crystalline NRG to amorphous form. These findings support the results of saturation solubility and dissolution data. The in vitro antioxidant, antimicrobial and cytotoxicity assessment displayed a greater activity of developed NRG SDs than the free NRG. The enhancement in the results may be due to the enhanced solubility of NRG after formation of SDs using the KollidonVA64 and Soluplus carrier blend.

Cetuximab functionalized chitosan/hyaluronic acid-based nanoparticles loaded with cabazitaxel enhances anti-tumor efficacy in DMBA-induced breast cancer model in rats through spatial targeting

The article discusses the ionic gelation of cationic chitosan (CS) with anionic hyaluronic acid (HA) sodium salt to form nanoparticles in the range of 125 nm. The particles were further functionalized with cetuximab to endow it with the ability to spatially target the tumor over-expressing EGFR. Solid-state characterization of the particles using XRD, FTIR, and DSC revealed the formation of stable nanoparticles with Cabazitaxel loaded in the amorphous nanostructure. XPS study used to assess the surface characteristics indicated that the cetuximab was successfully anchored on the surface of the particle. The prepared CS-HA-Cmab-NP elicited a pH-responsive drug release behavior due to the presence of CS in the matrix. In vitro performance of the nanoparticles was evaluated on MDA-MB-231 breast cancer cell lines showed overall increase in efficacy. In vivo pharmacokinetic and anti-tumor effect evaluated in female Sprague Dawley rats indicated that the Cmab-conjugated nanoparticles improved half-life of cabazitaxel and tumor reduction capability with higher survival rate and lower reduction in body weight. The results indicate that CS/HA nanoparticles anchored with cetuximab show enhanced efficacy in reducing the breast cancer tumor in DMBA-induced breast tumor model through spatial targeting, consequently reducing the systemic toxicity.

Eutectic mixtures of nevirapine: Phase diagrams, solid-state characterization, and dissolution studies

Solid-state modifications can improve drug performance. Studies have shown that multicomponent crystals, such as cocrystals and eutectic compositions, have successfully improved the performance of certain drugs, including their solubility. Nevirapine (NEV) is an antiretroviral drug with low aqueous solubility, impacting its bioavailability. This work aimed to study different nevirapine/co-former solid eutectic systems, define their phase diagrams and evaluate their dissolution properties. Caffeine (CAF), Theobromine (TEOB), and Theophylline (THEO) were chosen as co-formers due to their functional groups that can interact with NEV. Aiming to determine both temperature and eutectic composition, phase and Tamman diagrams were obtained using the differential scanning calorimetry (DSC) analysis of the mixtures indifferent NEV-co-former compositions (%w/w). Powder X-ray diffraction (PXRD) and DSC were used to characterize the eutectic materials. To assess the influence of eutectic systems on dissolution properties, we determined the powder dissolution profiles and intrinsic dissolution rates of anhydrous NEV and eutectic systems NEV-CAF and NEV-THEO using different dissolution media (pH 1.2 and pH 6.8). The eutectic compositions were calculated through the phase diagrams, interpolating the curves obtained by linear regression. Thus, the eutectic composition of the NEV-CAF system was determined to be 36.55 % NEV and eutectic temperature at 201.1 °C, while in the NEV-THEO system, the eutectic was obtained in a composition of 71.04 % NEV and eutectic temperature at 217.8 °C. Tamman diagrams were generated using the enthalpy values obtained from the DSC curves, and eutectic compositions were calculated using linear regression. The analysis revealed a eutectic composition of 36.51 % of NEV for the NEV-CAF system, and a eutectic composition of 70.94 % of NEV for the NEV-THEO system. It was not possible to determine the eutectic mass fraction of NEV-TEOB. A comparison of dissolution profiles and intrinsic dissolution rates in different dissolution media showed a significant improvement in the NEV dissolution rate in both eutectic systems. In an acidic medium, NEV dissolved 16 times faster in the NEV-CAF sample and 4 times faster in the NEV-THEO sample compared to pure anhydrous NEV. In a neutral medium, the dissolution profile of NEV was even more favorable in the same eutectic systems, showing that the increase in dissolution is relevant in a wide range of pH. In addition, the intrinsic dissolution rate in the two eutectic systems was higher than that of anhydrous NEV in all employed dissolution mediums. These eutectic systems improve the dissolution rate compared to pure NEV, offering the potential for enhancing the dissolution of poorly water-soluble drugs in the future.

Mechanisms of dissolution and crystallization of amorphous glibenclamide

Amorphous solid dispersions enhance the dissolution and oral bioavailability of poorly water-soluble drugs. However, the link between polymer properties and formulation performance has not been fully clarified yet. We studied the effect of hydroxypropyl cellulose (HPC) polymers molecular weight (Mw) on the storage stability, dissolution kinetics and supersaturation stability of spray-dried amorphous glibenclamide (GLB) formulations. The solid-state stability of amorphous GLB during storage was significantly enhanced by both the 40 kDa (HPC-SSL) and 84 kDa (HPC-L) polymers, regardless of Mw differences. In contrast, HPC-SSL maintained significantly higher aqueous drug concentrations during dissolution, compared to HPC-L (its higher Mw analogue). Dedicated dissolution experiments, in situ optical microscopy and solid-state characterization revealed that aqueous drug concentrations were determined by the interplay between crystallization inhibition, drug ionization, wetting and solubilization effects: (1) HPC prevents surface nucleation, hence inhibiting crystallization, (2) intestinal colloids (bile salts and phospholipids) increase supersaturated drug concentrations via wetting and solubilization effects and (3) pH and drug ionization severely impact the degree of supersaturation. The better performance of the lower Mw HPC-SSL was due to its superior inhibition of surface crystallization. These insights into the molecular mechanisms of dissolution and crystallization of amorphous solids provide foundation for rational formulation development.

Insights into the Theranostic Activity of Nonoxido VIV: Lysosome-Targeted Anticancer Metallodrugs.

Developing new anticancer agents can be useful, with the ability to diagnose and treat cancer worldwide. Previously, we focused on examining the effects of nonoxidovanadium(IV) complexes on insulin mimetic and cytotoxicity activity. In this study, in addition to the cytotoxic activity, we evaluated their bioimaging properties. This study investigates the synthesis of four stable nonoxido VIV complexes [VIV(L1-4)2] (1-4) using aroylhydrazone ligands (H2L1-4) and their full characterization in solid state and the solution phase stability using various physicochemical techniques. The biomolecular (DNA/HSA) interaction of the complexes was evaluated by using conventional methods. The in vitro cytotoxicity of 1-4 was studied against A549 and LN-229 cancer cell lines and found that drug 2 displayed the highest activity among the four. Since 1-4 are fluorescently active, live cell imaging was used to evaluate their cellular localization activity. Complexes specifically target the lysosome and damage lysosome integrity by producing an excessive amount (9.7-fold) of reactive oxygen species (ROS) compared to the control, which may cause cell apoptosis. Overall, this study indicates that 2 has the greatest potential for the development of multifunctional theranostic agents that combine imaging capabilities and anticancer properties of nonoxidovanadium(IV)-based metallodrugs.

Quality by Design (QbD) Approach to Develop Colon-Specific Ketoprofen Hot-Melt Extruded Pellets: Impact of Eudragit® S 100 Coating on the In Vitro Drug Release.

A pelletizer paired with hot-melt extrusion technology (HME) was used to develop colon-targeted pellets for ketoprofen (KTP). Thermal stability and side effects in the upper gastrointestinal tract made ketoprofen more suitable for this work. The pellets were prepared using the enzyme-triggered polymer Pectin LM in the presence of HPMC HME 4M, followed by pH-dependent Eudragit® S 100 coating to accommodate the maximum drug release in the colon by minimizing drug release in the upper gastrointestinal tract (GIT). Box-Behnken Design (BBD) was used for response surface optimization of the proportion of different independent variables like Pectin LM (A), HPMC HME 4M (B), and Eudragit® S 100 (C) required to lower the early drug release in upper GIT and to extend the drug release in the colon. Solid-state characterization studies revealed that ketoprofen was present in a solid solution state in the hot-melt extruded polymer matrix. The desired responses of the prepared optimized KTP pellets obtained by considering the designed space showed 1.20% drug release in 2 h, 3.73% in the first 5 h of the lag period with the help of Eudragit® S 100 coating, and 93.96% in extended release up to 24 h in the colonic region. Hence, developing Eudragit-coated hot-melt extruded pellets could be a significant method for achieving the colon-specific release of ketoprofen.

Development of inhaled moxifloxacin-metformin formulation as an alternative for pulmonary tuberculosis treatment

Resistant M. tuberculosis strains threaten pulmonary tuberculosis (P-TB) control since they limit drug options. Drug repositioning and new development strategies are urgently required to overcome resistance. Studies have already shown the beneficial role of the oral antidiabetic metformin as an anti-tuberculosis adjuvant drug. This work aimed to develop an inhalatory dry powder co-formulation of metformin and moxifloxacin to figure out a future option for P-TB treatment. Pre-formulation evaluations indicated the physicochemical compatibility of constituents, demonstrating powder crystallinity and acceptable drug content. Eight moxifloxacin-metformin dry powder formulations were produced by spray drying, and solid-state characterizations showed partial amorphization, ascribed to moxifloxacin. Four formulations containing L-leucine exhibited micromeritic and in vitro deposition profiles indicating pulmonary delivery suitability, like spherical and corrugated particle surface, geometric diameters < 5 μm, high emitted doses (>85 %), and mass median aerodynamic diameters between 1–5 μm. The use of a second spray dryer model further optimized the aerodynamic properties and yield of the best formulation, demonstrating the influence of the equipment used on the product obtained. Moreover, the final formulation showed high in vitro cell tolerability and characteristics in permeability studies indicative of good drug retention in the lungs.

Polyvinyl alcohol-chitosan based oleanolic acid nanofibers against bacterial infection: In vitro studies and in vivo evaluation by optical and laser Doppler imaging modalities

The present work focuses on the fabrication of polyvinyl alcohol-chitosan-loaded oleanolic acid-nanofibers (PVA-CS-OLA-NFs) for bacterial infection. The prepared PVA-CS-OLA-NFs were characterized for contact angle, SEM, AFM, XRD, FTIR, and TGA. The solid-state characterization and in vitro performance evaluation of nanofibers reveal consistent interconnection and diameters ranging from 102 ± 9.5 to 386 ± 11.6 nm. The nanofibers have a flat surface topography and exhibit efficient drug entrapment. Moreover, the in vitro release profile of PVA-CS-OLA-NFs was found to be 51.82 ± 1.49 % at 24 h. Furthermore, the hemocompatibility study showed that the developed PVA-CS-OLA-NFs are non-hemolytic to human blood. The PVA-CS-OLA-NFs demonstrate remarkable antibacterial capabilities, as evidenced by their MBC and MIC values, which range from 128 and 32 μg/mL, against the strains of S. aureus. The in-vivo fluorescence optical imaging showed the sustained PVA-CS-OLA-NFs release at the wound site infected with S. aureus for a longer duration of time. Moreover, the PVA-CS-OLA-NFs showed superior wound healing performance against S. aureus infected wounds compared to the marketed formulation. Further, the laser Doppler imaging system improved oxygen saturation, blood supply, and wound healing by providing real-time blood flow and oxygen saturation information.

Modified release, enriched biocompatibility, and enhanced oral bioavailability as precious features of nitrofurantoin-loaded polymeric nanoparticles

Nitrofurantoin (NTF) is a first-line therapy for treating urinary tract infections. However, gastric upset, short half-life, and poor bioavailability of NTF are major challenges for clinical use. Hence, the current work incorporated NTF in polymeric nanoparticles (NPs).NTF-loaded NPs (NTF-NPs) were prepared using Eudragit RS100 (RS100), DL-lactide/glycolide copolymer (PLGA), and their mixture at a ratio of 1:1 w/w (RS100/PLGA) as polymers. Pluronic F68, Tween 80, and polyvinyl alcohol (PVA) were applied as stabilizers. The particle size (PS), polydispersity index (PDI), zeta potential (ZP), and entrapment efficiency were determined. Three optimized formulations of NPs; F3, F13, and F29 were selected for further coating with Eudragit L100 (L100) and Eudragit S100 (S100). The optimized NPs and the corresponding coated ones were evaluated for solid-state characterization, morphology, and in vitro release. L100-coated F13 (LCF13) was further investigated for biocompatibility with normal oral epithelial cell (OEC) and Vero cell lines. A pharmacokinetic study using a rat model was also conducted.The results revealed that Tween 80 and PVA-stabilized NPs accomplished a nano-sized range with polymer- and stabilizer-dependent PDI and ZP. Optimized formulations: F3, F13, and F29 were selected for further coating where PS and PDI values not exceeding 260 nm and 0.502, respectively. The coated NPs had negative ZP ranging from −11.00 ± 2.70 to −40.20 ± 1.40 mV, attributable to the L100 or S100 coating. The solid-state characterization confirmed a transition of NTF to amorphousness. The spherical shape with the distinctive halo-like appearance of the coated NPs was proved. Additionally, the coating warranted a prolonged release of NTF especially for LCF13 avoiding the burst effect. Allowing enriched biocompatibility, LCF13 showed an IC50 value of 224.00 ± 9.20 μM for the OEC cell line, whereas a greater IC50 exceeding 300 μM was recognized for the LCF13-treated Vero cell line. After a single oral dose, LCF13 could provide a discernible increase in the extent of absorption (Du∞ = 863.31 ± 73.71 μg) with a significant extension of the absorption rate (tmax and t1/2 of 3 and 2.51 ± 0.317 h, respectively).LCF13 could be considered a controlled and safe nanocarrier that delivered significantly higher levels of NTF for a longer duration than NTF dispersion.

Formulation and optimization of olanzapine-carboxylic acid cocrystals orodispersible tablets: In-vitro/ In-vivo study

Oromucosal delivery of olanzapine (OLZ) is an optimal strategy to overcome low oral bioavailability as well as improve medication adherence. However, its poor aqueous solubility may hinder its absorption through the buccal mucosa. The aim of the study is to enhance OLZ solubility and dissolution via cocrystal formation, followed by incorporation into an orodispersible tablet (ODT) based on an effervescent mixture and crospovidone as a superdisintegrant mixture. OLZ was cocrystallized with different carboxylic acids using slow solvent evaporation, and the optimal cocrystal formula was subjected to solid state characterization. Central composite design (CCD) was used in the modeling and optimization of the ODT independent variables (amounts of crospovidone and effervescent mixture). The optimized OLZ cocrystal ODTs were subjected to microenvironmental pH, stability, and in-vivo studies. The results revealed that the OLZ:itaconic acid at 1:1 M ratio showed a 7.86 fold increase in OLZ solubility and 86.71 ± 1.07 % dissolution efficiency (DE60 %) with FTIR, XRPD, and DSC diffractograms that confirmed the cocrystal formation. The optimized OLZ cocrystal ODTs exhibited hardness of 3.6 ± 0.1 kg/cm2, disintegration time of 11.66 ± 1.52 s, wetting time of 36.33 ± 2.51 s, and 94.26 ± 2.77 % OLZ released within 15 min with a DE60 % of 91.65 ± 0.98 %. Finally, the optimized OLZ cocrystal ODTs showed a significant (p < 0.01) higher Cmax and AUC with a relative bioavailability of 139.08 % compared to the Schisolazine©10 mg ODTs. These results suggest that OLZ:itaconic acid cocrystal incorporated into an ODT containing a superdisintegrant mixture of effervescence mixture and crospovidone is a potential approach for enhancement of oromucosal delivery of OLZ.

Exploring novel anticorrosive applications: Solid-state synthesis and characterization of Li2CuP2O7 and Na2CuP2O7 pyrophosphates

This work shows the importance of inorganic materials Li2CuP2O7 and Na2CuP2O7, especially the effect of Li and Na atoms, in their use as inhibitors that preserve Mild steel in 1.0 M HCl solution. Lithium and Sodium copper (II) pyrophosphate crystals were synthesized through solid-state reaction and characterized using Infrared Spectroscopy technique (IR), as well as X-ray diffraction (XRD). The infrared spectrum of compounds Li2CuP2O7 and Na2CuP2O7 was captured and interpreted, revealing a bent POP bridging angle within these compounds. Furthermore, the inhibitory effect of these pyrophosphates on Mild steel corrosion in a 1.0 M HCl solution was studied. During this investigation, electrochemical techniques alongside surface examination through SEM and EDX. The experimental findings demonstrated that Li2CuP2O7 and Na2CuP2O7 act as effective inhibitors, with inhibition efficiency (ηPP%) rising as the inhibitor concentration increases. At a concentration of 10−3 M, Li2CuP2O7 exhibited a remarkable inhibition efficiency of 93 %, which appears to be mixed-type inhibitors.

Electrically Conductive Peptide Fibers as Direct Electron Transfer Scaffolds for Enzymatic Electrocatalysis

Biology provides many sources of inspiration for synthetic and multi-functional nanomaterials. Naturally evolved proteins possess a range of unique functions and self-assembly behavior. Some of these have electron transport functions as part of metabolic processes. Their flexible design and potential for stimuli responsiveness make proteins ideal building blocks of bioelectronic interfaces. In biosensor and electrocatalysis applications, bioelectronic materials are designed to interconvert biological signals or processes into electronic signals and vice versa. In this work, we designed a peptide fiber structure that exhibits stimuli-responsive self-assembly and the capacity to transport electrical current over micrometer long distances. Hierarchically ordered nanofibers of α-helical coiled-coil peptides were assembled using a pH responsive structure ordering motif comprising of two neighboring lysine residues. Cryo-EM structures of these assemblies reveal a novel organization of α-helical peptides in a cross coiled coil arrangement that exhibits electrical conductivity. Both solid-state and solution-based electrochemical characterization show that these fibers are conductive. Single-fiber conductive AFM determined that the solid-state electrical conductivity is on a similar order of magnitude with conductive cytochrome filaments from bacteria. Solution deposited fiber films approximately doubled the electroactive surface area of the electrode, confirming their conductivity in aqueous environments. Furthermore, these fibers can be used as scaffolds for redox enzyme immobilization for electrochemical biosensing. Progress towards immobilized enzymatic devices will be discussed as well. This work further expands the field of stimuli-responsive and multifunctional nanomaterials by using peptide assemblies as structural supports for future implementation in bioelectronic and bioelectrochemical systems.

Exploring Salts of Memantine with Inorganic Anions: From Polymorphism and Solid-State Transitions to Potential for Drug Formulations.

This study examines pharmaceutically acceptable inorganic salts of memantine, specifically focusing on hydrogen sulfate, sulfate, and dihydrogen phosphate salts, with the aim of finding alternatives to the commonly used chloride salt in the treatment of Alzheimer's disease. Through comprehensive solid-state characterization, including powder X-ray diffraction, thermal analysis, and solubility testing, we unveil complex polymorphic behaviors, reversible solid-state transitions, and significant differences in solubility and stability among the salts. Notably, the hydrogen sulfate salt emerges as a promising candidate for drug formulations, offering improved solubility, nonhygroscopic nature, and favorable morphological characteristics compared to the existing chloride salt. This work establishes a foundation for further investigation into memantine salts as potential therapeutics with improved efficacy.

Solid-state NMR of active sites in TiO2 photocatalysis: a critical review

Titanium dioxide (TiO2) is one of the optimal semiconductor metal oxide photocatalysts with a wide range of application fields, such as heterogeneous catalysis, energy science, and environmental science. Solid-state nuclear magnetic resonance (NMR) spectroscopy is a powerful tool for characterizing both structure and dynamics at an atomic-molecular level in heterogeneous catalysts. In this review, we first provide a brief discussion on the progress in investigating the structures of titanium and oxygen in bulk and on the surface of TiO2 by using various solid-state NMR techniques. Advances in the understanding of electronic structure and properties of TiO2 with distinct surface features, including various crystal facets and heteroatomic adsorption by chemical probe-assisted NMR techniques, are secondly presented. The solid-state NMR characterization of heteroatom active sites (such as 13C, 15N, 11B, 27Al) and their function in TiO2 photocatalysts is described in detail. Finally, a critical discourse assesses the current limitations and prospects of solid-state NMR in its application to the optimization and design of advanced TiO2 photocatalysts.

Application of Casein Micelles for Targeting Huntington's Disease in Experimental Zebrafish Model.

Huntington's disease (HD) is an incorrigible neuropsychiatric disorder with reduced cognition and motor abnormalities. Piperine (PIP) is an alkaloid with antioxidant, anti-inflammatory, and neuroprotective activities; however, poor therapeutic efficacy limits its further use. The current study focuses on the enhanced therapeutic potential of PIP@CM against an experimental zebrafish model of HD. PIP@CM was fabricated using spray drying technology, followed by solid-state investigations. We performed in vitro release and in vitro antioxidant activity (DPPH assay) of PIP and PIP@CMs. In addition, in vivo studies were conducted on zebrafish using 3-nitropropionic acid (3-NPA) (60mg/kg) as a neurotoxin and treated with PIP (5mg/kg) and PIP@CM (25mg/kg equivalent to 5mg/kg PIP). After dosing, various in vivo studies (behavioral, biochemical, and histological) were conducted. The solid-state characterization techniques revealed the loss of crystallinity after micelles formation. In vitro release and antioxidant assays showed higher release and enhanced activity of PIP@CM. In vivo studies revealed that 3-NPA administration causes HD, as evidenced by the results of open field test (OFT) and novel tank diving test (NTD) tests. Moreover, 3-NPA causes an increase in oxidative stress, as confirmed by biochemical and histopathological studies. PIP@CM treatment significantly improved behavioral performance in OFT and NTD tests and reduced oxidative stress markers as compared to pure PIP and untreated HD model.

Computational-Based Polyphenol Therapy for Nonsmall Cell Lung Cancer: Naringin Coamorphous Systems for Solubility and Bioavailability Enhancement.

In this research, we utilized molecular simulations to create co-amorphous materials (CAMs) of ceritinib (CRT) with the objective of improving its solubility and bioavailability. We identified naringin (NRG) as a suitable co-former for CRT CAMs based on binding energy and intermolecular interactions through computational modeling. We used the solvent evaporation method to produce CAMs of CRT and NRG, expecting to enhance both solubility and bioavailability simultaneously. The solid-state characterization using techniques like differential scanning calorimeter, X-ray powder diffraction, and Fourier-transform infrared spectroscopy affirmed the formation of a single amorphous phase and the presence of intermolecular interactions between CRT and NRG in the CAMs. These materials remained physically stable for up to six months under dry conditions at 40 °C. Moreover, the CAMs demonstrated significant improvements in the solubility and dissolution of CRT (specifically in the ratio CRT:NRG 1:2). This, in turn, led to an increase in cytotoxicity, apoptotic cells, and G0/G1 phase inhibition in A549 cells compared to CRT alone. Furthermore, CRT permeability is also improved twofold, as estimated by the everted gut sac method. The enhanced solubility of CAMs also positively affected the pharmacokinetic parameters. When compared to the physical mixture, the CAMs of CRT:NRG 2:1 exhibited a 2.1-fold increase in CRT exposure (AUC0-t) and a 2.4-fold increase in plasma concentration (Cmax).

Proton-Coupled Electron Transfer at the Pu5+/4+ Couple.

The synthesis and solution and solid-state characterization of [Pu4+(NPC)4], 1-Pu, (NPC = [NPtBu(pyrr)2]-; tBu = C(CH3)3; pyrr = pyrrolidinyl) and [Pu3+(NPC)4][K(2.2.2.-cryptand)], 2-Pu, is described. Cyclic voltammetry studies of 1-Pu reveal a quasi-reversible Pu4+/3+ couple, an irreversible Pu5+/4+ couple, and a third couple evincing a rapid proton-coupled electron transfer (PCET) reaction occurring after the electrochemical formation of Pu5+. The chemical identity of the product of the PCET reaction was confirmed by independent chemical synthesis to be [Pu4+(NPC)3(HNPC)][B(ArF5)4], 3-Pu, (B(ArF5)4 = tetrakis(2,3,4,5,6-pentafluourophenyl)borate) via two mechanistically distinct transformations of 1-Pu: protonation and oxidation. The kinetics and thermodynamics of this PCET reaction are determined via electrochemical analysis, simulation, and density functional theory. The computational studies demonstrate a direct correlation between the changing nature of 5f and 6d orbital participation in metal-ligand bonding and the electron density on the Nim atom with the thermodynamics of the PCET reaction from Np to Pu, and an indirect correlation with the roughly 5-orders of magnitude faster Pu PCET compared to Np for the An5+ species.

Functional Nanostructured Lipid Carrier-Enriched Hydrogels Tailored to Repair Damaged Epidermal Barrier.

In this study, a functional nanostructured lipid carriers (NLCs)-based hydrogel was developed to repair the damaged epidermal skin barrier. NLCs were prepared via a high-energy approach, using argan oil and beeswax as liquid and solid lipids, respectively, and were loaded with ceramides and cholesterol at a physiologically relevant ratio, acting as structural and functional compounds. Employing a series of surfactants and optimizing the preparation conditions, NLCs of 215.5 ± 0.9 nm in size and a negative zeta potential of -42.7 ± 0.9 were obtained, showing acceptable physical and microbial stability. Solid state characterization by differential scanning calorimetry and X-ray powder diffraction revealed the formation of imperfect crystal NLC-type. The optimized NLC dispersion was loaded into the gel based on sodium hyaluronate and xanthan gum. The gels obtained presented a shear thinning and thixotropic behavior, which is suitable for dermal application. Incorporating NLCs enhanced the rheological, viscoelastic, and textural properties of the gel formed while retaining the suitable spreadability required for comfortable application and patient compliance. The NLC-loaded gel presented a noticeable occlusion effect in vitro. It provided 2.8-fold higher skin hydration levels on the ex vivo porcine ear model than the NLC-free gel, showing a potential to repair the damaged epidermal barrier and nourish the skin actively.

Structural and Electrochemical Insights into Five Coordinate Cobalt bis(dithiolene) N-heterocyclic Carbene Complexes

Two new cobalt-bis(dithiolene)-IMes (IMes = 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene) complexes have been isolated, and a systematic solid-state structural characterization using single crystal X-ray diffraction studies was undertaken to confirm the identity of the complexes. (IMes)Co(S2C2Ph2)2 (1) crystallizes in a monoclinic space group I2/a, while (IMes)Co(S2C2(C6H4-p-OCH3)2)2 (2) crystallizes in a triclinic space group P1¯. A detailed solid-state structural analysis of 1 and 2 revealed that the extended structure is stabilized by a series of CH…S interactions. As validated using electrochemical studies, the binding of IMes to the cobalt atom may be electrochemically controlled by applying a suitable redox potential. These studies indicate that compounds 1 and 2 are expected to act as an effective electrochemical host, enabling them to be used as precursors to release IMes under environmentally benign conditions.

Solid-State NMR Characterization of Mefloquine Resinate Complexes Designed for Taste-Masking Pediatric Formulations.

Mefloquine (MQ) is an antimalarial medication prescribed to treat or malaria prevention.. When taken by children, vomiting usually occurs, and new doses of medication frequently need to be taken. So, developing pediatric medicines using taste-masked antimalarial drug complexes is mandatory for the success of mefloquine administration. The hypothesis that binding mefloquine to an ion-exchange resin (R) could circumvent the drug's bitter taste problem was proposed, and solid-state 13C cross-polarization magic angle spinning (CPMAS) NMR was able to follow MQ-R mixtures through chemical shift and relaxation measurements. The nature of MQ-R complex formation could then be determined. Impedimetric electronic tongue equipment also verified the resinate taste-masking efficiency in vitro. Variations in chemical shifts and structure dynamics measured by proton relaxation properties (e.g., T1ρH) were used as probes to follow the extension of mixing and specific interactions that would be present in MQ-R. A significant decrease in T1ρH values was observed for MQ carbons in MQ-R complexes, compared to the ones in MQ (from 100-200 ms in MQ to 20-50 ms in an MQ-R complex). The results evidenced that the cationic resin interacts strongly with mefloquine molecules in the formulation of a 1:1 ratio complex. Thus, 13C CPMAS NMR allowed the confirmation of the presence of a binding between mefloquine and polacrilin in the MQ-R formulation studied.