A Solar to Chemical Strategy: Green Hydrogen as a Means, Not an End.

Green hydrogen is the key to the chemical industry achieving net zero emissions. The chemical industry is responsible for almost 2% of all CO2 emissions, with half of it coming from the production of simple commodity chemicals, such as NH3, H2O2, methanol, and aniline. Despite electrolysis driven by renewable power sources emerging as the most promising way to supply all the green hydrogen required in the production chain of these chemicals, in this review, it is worth noting that the photocatalytic route may be underestimated and can hold a bright future for this topic. In fact, the production of H2 by photocatalysis still faces important challenges in terms of activity, engineering, and economic feasibility. However, photocatalytic systems can be tailored to directly convert sunlight and water (or other renewable proton sources) directly into chemicals, enabling a solar-to-chemical strategy. Here, a series of recent examples are presented, demonstrating that photocatalysis can be successfully employed to produce the most important commodity chemicals, especially on NH3, H2O2, and chemicals produced by reduction reactions. The replacement of fossil-derived H2 in the synthesis of these chemicals can be disruptive, essentially safeguarding the transition of the chemical industry to a low-carbon economy.

Single-Atoms on Crystalline Carbon Nitrides for Selective C─H Photooxidation: A Bridge to Achieve Homogeneous Pathways in Heterogeneous Materials.

Single-atom catalysis is a field of paramount importance in contemporary science due to its exceptional ability to combine the domains of homogeneous and heterogeneous catalysis. Iron and manganese metalloenzymes are known to be effective in C─H oxidation reactions in nature, inspiring scientists to mimic their active sites in artificial catalytic systems. Herein, a simple and versatile cation exchange method is successfully employed to stabilize low-cost iron and manganese single-atoms in poly(heptazine imides) (PHI). The resulting materials are employed as photocatalysts for toluene oxidation, demonstrating remarkable selectivity toward benzaldehyde. The protocol is then extended to the selective oxidation of different substrates, including (substituted) alkylaromatics, benzyl alcohols, and sulfides. Detailed mechanistic investigations revealed that iron- and manganese-containing photocatalysts work through a similar mechanism via the formation of high-valent M═O species. Operando X-ray absorption spectroscopy (XAS) is employed to confirm the formation of high-valent iron- and manganese-oxo species, typically found in metalloenzymes involved in highly selective C─H oxidations.

Carbon nitride based materials: more than just a support for single-atom catalysis.

Recently, the missing link between homogeneous and heterogeneous catalysis has been found and it was named single-atom catalysis (SAC). However, the SAC field still faces important challenges, one of which is controlling the bonding/coordination between the single atoms and the support in order to compensate for the increase in surface energy when the particle size is reduced due to atomic dispersion. Excellent candidates to meet this requirement are carbon nitride (CN)-based materials. Metal atoms can be firmly trapped in nitrogen-rich coordination sites in CN materials, which makes them a unique class of hosts for preparing single-atom catalysts (SACs). As one of the most promising two-dimensional supports to stabilize isolated metal atoms, CN materials have been increasingly employed for preparing SACs. Herein, we will cover the most recent advances in single-atoms supported by CN materials. In this review, the most important characterization techniques and the challenges faced in this topic will be discussed, and the commonly employed synthetic methods will be delineated for different CN materials. Finally, the catalytic performance of SACs based on carbon nitrides will be reviewed with a special focus on their photocatalytic applications. In particular, we will prove CN as a non-innocent support. The relationship between single-atoms and carbon nitride supports is two-way, where the single-atoms can change the electronic properties of the CN support, while the electronic features of the CN matrix can tune the catalytic activity of the single sites in photocatalytic reactions. Finally, we highlight the frontiers in the field, including analytical method development, truly controlled synthetic methods, allowing the fine control of loading and multi-element synthesis, and how understanding the two-way exchange behind single-atoms and CN supports can push this topic to the next level.

Species diversity and phylogeography of the Australoheros autrani group (Teleostei, Cichlidae) in eastern Brazil.

Cichlid fishes are an important model system in evolutionary biology, primarily because of their exceptional diversity. However, while some cichlid assemblages, such as the ones of the African Great Lakes, have received considerable attention, others are not well studied, including many riverine species. Here, we focus on the Australoheros autrani species group and first report a new record of Australoheros in the upper Paranaíba River drainage, extending the known distribution range of this genus. Through Bayesian inference and maximum likelihood phylogenetic analyses of the mitochondrial cytochrome b gene of these specimens as well as available sequences, we assigned the newly discovered population to Australoheros barbosae. We corroborate the monophyly of the A. autrani species group and the presence of three species in the upper/middle Paraíba do Sul River basin as well as molecular diagnostic characters for each. Finally, we provide evidence for a recent expansion of A. barbosae. Supplementary Information: The online version contains supplementary material available at 10.1007/s10228-022-00888-9.

Modified Poly(Heptazine Imides): Minimizing H2O2 Decomposition to Maximize Oxygen Reduction.

Photocatalysis provides a sustainable pathway to produce the consumer chemical H2O2 from atmospheric O2 via an oxygen reduction reaction (ORR). Such an alternative is attractive to replace the cumbersome traditional anthraquinone method for H2O2 synthesis on a large scale. Carbon nitrides have shown very interesting results as heterogeneous photocatalysts in ORR because their covalent two-dimensional (2D) structure is believed to increase selectivity toward the two-electron process. However, an efficient and scalable application of carbon nitrides for this reaction is far from being achieved. Poly(heptazine imides) (PHIs) are a more powerful subgroup of carbon nitrides whose structure provides high crystallinity and a scaffold to host transition-metal single atoms. Herein, we show that PHIs functionalized with sodium and the recently reported fully protonated PHI exhibit high activity in two-electron ORR under visible light. The latter converted O2 to up to 1556 mmol L-1 h-1 g-1 H2O2 under 410 nm irradiation using inexpensive but otherwise chemically demanding glycerin as a sacrificial electron donor. We also prove that functionalization with transition metals is not beneficial for H2O2 synthesis, as the metal also catalyzes its decomposition. Transient photoluminescence spectroscopy suggests that H-PHIs exhibit higher activity due to their longer excited-state lifetime. Overall, this work highlights the high photocatalytic activity of the rarely examined fully protonated PHI and represents a step forward in the application of inexpensive covalent materials for photocatalytic H2O2 synthesis.

Selective methane photooxidation into methanol under mild conditions promoted by highly dispersed Cu atoms on crystalline carbon nitrides.

Here we report a photocatalytic system based on crystalline carbon nitrides (PHI) and highly dispersed transition metals (Fe, Co and Cu) for controlled methane photooxidation to methanol under mild conditions. The Cu-PHI catalyst showed a remarkable methanol production (2900 µmol g-1) in 4 hours, with a turnover number of 51 moles of oxygenated liquid product per mole of Cu. To date, this result is the highest value for methane oxidation under mild conditions (1 bar, 25 °C).

Graphitic carbon nitrides as platforms for single-atom photocatalysis.

Herein we demonstrate that adding single atoms of selected transition metals to graphitic carbon nitrides allows the tailoring of the electronic and chemical properties of these 2D nanomaterials, directly impacting their usage in photocatalysis. These single-atom photocatalysts were successfully prepared with Ni2+, Pt2+ or Ru3+ by cation exchange, using poly(heptazine imides) (PHI) as the 2D layered platform. Differences in photocatalytic performance for these metals were assessed using rhodamine-B (RhB) and methyl orange (MO) as model compounds for degradation. We have demonstrated that single atoms may either improve or impair the degradation of RhB and MO, depending on the proper matching of the net charge of these molecules and the surface potential of the catalyst, which in turn is responsive to the metal incorporated into the PHI nanostructures. Computer simulations demonstrated that even one transition metal cation caused dramatic changes in the electronic structure of PHI, especially regarding light absorption, which was extended all along the visible up to the near IR region. Besides introducing new quantum states, the metal atoms strongly polarized the molecular orbitals across the PHI and electrostatic fields arising from the electronic transitions became at least tenfold stronger. This simple proof of concept demonstrates that these new materials hold promise as tools for many important photocatalytic reactions that are strongly dependent on our ability to control surface charge and its polarization under illumination, such as H2 evolution, CO2 reduction and photooxidation in general.

Dietary xylanase and live yeast supplementation influence intestinal bacterial populations and growth performance of piglets fed a sorghum-based diet.

This study was to evaluate the effect of xylanase supplementation and the addition of live yeast, Saccharomyces cerevisiae, on growth performance and intestinal microbiota in piglets. One hundred and eighty commercial crossbred 23-d-old piglets (PIC 417) were sorted by initial BW and allocated to 3 treatments: control (CTR) diet, CTR diet supplemented with xylanase at 16,000 birch xylan units/kg (XYL) and XYL diet supplemented with live yeast (2 × 1010 CFU/g) at 1 kg/t (XYL + LY). Each treatment had 10 replicates, with 6 animals each. A sorghum-based diet and water were available ad libitum for 42 d of the study. Average daily gain (ADG) and average daily feed intake (ADFI) were measured from 0 to 42 d (23- to 65-d-old) and feed conversion ratio (FCR) calculated. At the end of the study, bacterial identification through 16S rRNA (V3 to V4) sequencing of the ileal and caecal digesta from one piglet per replicate was performed. No treatment effects were observed on ADFI. Pigs offered the live yeast in addition to the xylanase had increased ADG compared with those supplemented with xylanase alone (XYL + LY vs. XYL; P = 0.655). FCR was improved with XYL and XYL + LY compared with CTR (P = 0.018). Clostridiaceae counts in the ileum tended to reduce by 10% with XYL and 14% with XYL + LY compared to CTR (P = 0.07). XYL and XYL + LY increased the counts of Lactobacillaceae in the caecum compared with CTR (P < 0.0001). Dietary supplementation of live yeast combined with xylanase improved growth performance and microbial balance of piglets during the nursery phase.

Impact of Drug-Polymer Interaction in Amorphous Solid Dispersion Aiming for the Supersaturation of Poorly Soluble Drug in Biorelevant Medium.

The aim of this study was to investigate the influence of the production method and the polymeric carrier on the ability to generate and maintain the supersaturation of a poorly soluble drug in biorelevant medium. The amorphous solid dispersion of sulfamethoxazole, an antibacterial drug, was produced using two different polymers by spray-drying or hot melt extrusion methods. When Eudragit EPO was used, supersaturation was maintained up to 24 h for both techniques at all drug-polymer proportions. However, when Soluplus was employed in hot melt extrusion, a smaller amount of drug was dissolved when compared to the amorphous drug. The proportion of 3:7 drug-Eudragit EPO (w/w) produced by spray-drying presented a higher amount of drug dissolved in supersaturation studies and it was able to maintain the physical stability under different storage conditions throughout the 90-day evaluation. Supersaturation generation and system stability were found to be related to more effective chemical interaction between the polymer and the drug provided by the production method, as revealed by the 1D ROESY NMR experiment. Investigation of drug-polymer interaction is critical in supersaturating drug delivery systems to avoid crystallization of the drug and to predict the effectiveness of the system. Chemical compounds studied in this article: Sulfamethoxazole (PubChem CID: 4539) and Methacrylate copolymer - Eudragit EPO (PubChem CID: 65358).

Supersaturating drug delivery system of fixed drug combination: sulfamethoxazole and trimethoprim.

Background: The drug supersaturation in the intestinal lumen for few hours could result in high bioavailability. The goal of this study was the development of a supersaturating drug delivery system containing sulfamethoxazole and trimethoprim at fixed dose combination (sulfamethoxazole:trimethoprim 5:1 w/w). Methods: The amorphous solid dispersions were formed at three different proportions containing 30, 50 and 70% of Eudragit EPO in the formulation. Results: The supersaturation state is formed by the amorphous drugs produced by spray drying technique, and the maintenance of this state is due to the chemical interactions between the drugs and the polymer selected, which was observed in the fluorescence interaction studies realized between the drugs and the polymer. The Formulation containing 70% of the polymer was able to produce and maintain the supersaturated state of both drugs for 24 h. Solid state characterization demonstrated the amorphization of the drugs in the solid dispersion and indicated the hydrogen bond formation responsible for the improvement in the apparent solubility. This formulation presented an improved antibacterial activity when compared to the combination of the drugs. Conclusion: For the first time, a supersaturating drug delivery system was developed to the complementary antibacterial drugs. This ternary formulation is a powerful alternative to improve oral absorption of recognized safety drugs, reducing the dose and consequently the antibiotic resistance emergence.

Intestinal permeability determinants of norfloxacin in Ussing chamber model.

Recently, many efforts are taken to identify the intestinal uptake and efflux transporters since they are responsible for the absorption of many drugs as their interactions. Norfloxacin (NFX) is a fluoroquinolone that presents low solubility and low permeability, and as a consequence, low bioavailability. In this context, the aim of this study is evaluate for the first time the intestinal permeability mechanisms of NFX by Ussing chamber model. The low permeation of NFX at low temperature, where the efflux pumps are not active, reveals that NFX permeation is transporter-dependent. The permeation study at different level of intestine demonstrated that NFX passage is in the decrescent order: ileum > jejunum > duodenum > colon, probably attributed to transporters that are expressed differently along the intestinal tract. NFX intestinal flow was evaluated in the presence of many inhibitors and substrates to identify the uptake and efflux transporters implicate in NFX permeability mechanism. It could be observed that BCRP and MRPs are involved in the NFX efflux and PEPT1, PMAT and OCT in the NFX uptake transport. Furthermore, this work revealed that NFX has itself an affinity for OCTN and OATP, demonstrating that NFX could inhibit these transporters and influence the absorption of other drugs. The updated description of NFX intestinal permeability factors could contribute to the development of rational pharmaceutical formulations that could circumvent the efflux problems and consequently improve NFX biopharmaceutical properties and avoid drug-drug interactions.

Cyclodextrin based nanosponge of norfloxacin: Intestinal permeation enhancement and improved antibacterial activity.

Nanosponges are a novel class of hyperbranched cyclodextrin-based nanostructures that exhibits remarkable potential as a drug host system for the improvement in biopharmaceutical properties. This work aims the development of cyclodextrin-based nanosponge of norfloxacin to improve its physicochemical characteristics. ß-cyclodextrin was used as base and diphenyl carbonate as crosslinker agent at different proportions to produce nanosponges that were evaluated by in vitro and in vivo techniques. The proportion cyclodextrin:crosslinker 1:2 M/M was chosen due to its higher encapsulation efficiency (80%), revealing an average diameter size of 40 nm with zeta potential of -19 mV. Norfloxacin-loaded nanosponges exhibited higher passage of norfloxacin in comparison to norfloxacin drug alone by Ussing chamber method. The nanosponge formulation also revealed a mucoadhesive property that could increase norfloxacin absorption thus improving its antibiotic activity in an in vivo sepsis model. Therefore, nanosponges may be suitable carrier of norfloxacin to maximize and facilitate oral absorption.

γ-irradiation from radiotherapy improves the virulence potential of Candida tropicalis.

AIM: To evaluate if radiation used in radiotherapy can cause changes in the virulence potential of Candida tropicalis ATCC 750. MATERIALS & METHODS: C. tropicalis was exposed in vitro to identical dose and scheme of irradiation would be used in patients with head and neck cancer. Some virulence parameters were analyzed before and after irradiation. RESULTS: Colony morphologies were irreversibly affected by irradiation. Increase in growth rate, filamentation, adhesion on cell lines and phagocytosis process were also observed. Overall the irradiated C. tropicalis cells became more efficient at causing systemic infection in mice. CONCLUSION: γ-radiation induced important changes in C. tropicalis increasing its virulence profile, which could directly affect the relationship between yeasts and hosts.

In vitro Effects of Lemongrass Extract on Candida albicans Biofilms, Human Cells Viability, and Denture Surface.

The purpose of this study was to investigate whether immersion of a denture surface in lemongrass extract (LGE) has effects on C. albicans biofilms, human cell viability and denture surface. Minimal inhibitory concentration (MIC) and minimal fungicidal concentration (MFC) were performed for LGE against C. albicans. For biofilm analysis, discs were fabricated using a denture acrylic resin with surface roughness standardization. C. albicans biofilms were developed on saliva-coated discs, and the effects of LGE at MIC, 5XMIC, and 10XMIC were investigated during biofilm formation and after biofilm maturation. Biofilms were investigated for cell counting, metabolic activity, and microscopic analysis. The cytotoxicity of different concentrations of LGE to peripheral blood mononuclear cells (PBMC) was analyzed using MTT. The effects of LGE on acrylic resin were verified by measuring changes in roughness, color and flexural strength after 28 days of immersion. Data were analyzed by ANOVA, followed by a Tukey test at a 5% significance level. The minimal concentration of LGE required to inhibit C. albicans growth was 0.625 mg/mL, while MFC was 2.5 mg/mL. The presence of LGE during biofilm development resulted in a reduction of cell counting (p < 0.05), which made the MIC sufficient to reduce approximately 90% of cells (p < 0.0001). The exposure of LGE after biofilm maturation also had a significant antifungal effect at all concentrations (p < 0.05). When compared to the control group, the exposure of PBMC to LGE at MIC resulted in similar viability (p > 0.05). There were no verified differences in color perception, roughness, or flexural strength after immersion in LGE at MIC compared to the control (p > 0.05). It could be concluded that immersion of the denture surface in LGE was effective in reducing C. albicans biofilms with no deleterious effects on acrylic properties at MIC. MIC was also an effective and safe concentration for use.

NIK1-mediated translation suppression functions as a plant antiviral immunity mechanism.

Plants and plant pathogens are subject to continuous co-evolutionary pressure for dominance, and the outcomes of these interactions can substantially impact agriculture and food security. In virus-plant interactions, one of the major mechanisms for plant antiviral immunity relies on RNA silencing, which is often suppressed by co-evolving virus suppressors, thus enhancing viral pathogenicity in susceptible hosts. In addition, plants use the nucleotide-binding and leucine-rich repeat (NB-LRR) domain-containing resistance proteins, which recognize viral effectors to activate effector-triggered immunity in a defence mechanism similar to that employed in non-viral infections. Unlike most eukaryotic organisms, plants are not known to activate mechanisms of host global translation suppression to fight viruses. Here we demonstrate in Arabidopsis that the constitutive activation of NIK1, a leucine-rich repeat receptor-like kinase (LRR-RLK) identified as a virulence target of the begomovirus nuclear shuttle protein (NSP), leads to global translation suppression and translocation of the downstream component RPL10 to the nucleus, where it interacts with a newly identified MYB-like protein, L10-INTERACTING MYB DOMAIN-CONTAINING PROTEIN (LIMYB), to downregulate translational machinery genes fully. LIMYB overexpression represses ribosomal protein genes at the transcriptional level, resulting in protein synthesis inhibition, decreased viral messenger RNA association with polysome fractions and enhanced tolerance to begomovirus. By contrast, the loss of LIMYB function releases the repression of translation-related genes and increases susceptibility to virus infection. Therefore, LIMYB links immune receptor LRR-RLK activation to global translation suppression as an antiviral immunity strategy in plants.

The effect of a minor constituent of essential oil from Citrus aurantium: the role of ß-myrcene in preventing peptic ulcer disease.

The monoterpene ß-myrcene has been widely used in cosmetics, food and beverages, and it is normally found in essential oil from citrus fruit. The aim of this study was to investigate the anti-ulcer effects of ß-myrcene on experimental models of ulcers that are induced by ethanol, NSAIDs (non-steroidal anti-inflammatory drugs), stress, Helicobacter pylori, ischaemia-reperfusion injury (I/R) and cysteamine in order to compare with the essential oil of Citrus aurantium and its major compound limonene. The results indicate that the oral administration of ß-myrcene at a dose of 7.50mg/kg has important anti-ulcer activity with significantly decreased gastric and duodenal lesions as well as increased gastric mucus production. The results showed treatment with ß-myrcene caused a significant increase in mucosal malondialdehyde level (MDA), an important index of oxidative tissue damage. The ß-myrcene was also endowed with marked enhancement of antioxidant enzyme activity from GR system as evidenced by the decreased activity of superoxide dismutase (SOD) and increased levels of glutathione peroxidase (GPx), glutathione reductase (GR), and total glutathione in gastric tissue. Our results also shown that treatment with ß-myrcene is not involved with thioredoxin reductase (TrxR) activity. Our results reveal, for the first time, the importance of ß-myrcene as an inhibitor of gastric and duodenal ulcers and demonstrate that an increase in the levels of gastric mucosa defence factors is involved in the anti-ulcer activity of ß-myrcene.

Efeito da aplicação de adesivos de 2 passos e autocondicionantes fotoativados por luz halógena ou LED na microinfiltração marginal: estudo in vitro. / Effect of 2-step/self-each bond system and halogen light or LED on the microleakage: in vitro study.

O objetivo desse estudo foi analisar a efetividade de sistemas adesivos convencionais e autocondicionantes, e de diferentes métodos de fotoativação para redução da microinfiltração marginal. Foram utilizados 48 dentes incisivos bovinos nesse estudo. Os dentes foram divididos em quatro grupos de 12 amostras de acordo com o tipo de adesivo ou método de fotoativação utilizado: Grupo 1- Sistema adesivo de passos fotoativadas por luz halógena com intensidade de 700 mW/cm2 Grupo 2 - Sistema adesivo de dois passos fotoativados pelo LED com intensidade de 470 mW/cm2; Grupo 3 - sistema adesivo autocondicionante fotoativados por luz halógena; Grupo 4 - Sistema adesivo autocondicionante fotoativados por LED. Uma resina composta nanoparticulada foi utilizada para restaurar todas as cavidades. Em seguida, os grupos foram submetidos ao tratamento de ciclagem térmica e foram colocados por 24 horas em solução de azul de metileno. A microinfiltração foi avaliada de acordo com o grau de penetração do corante na interface dente-restauração. Para análise estatística, foi utilizado o teste não paramétrico de Kruskal Wallis complementado pelo teste de Mann-Whitney, no nível de 5% de significância. O grupo 1 apresentou estatisticamente menores índices de microinfiltração marginal que o grupo 2 na parece oclusal (p<0.05) e os grupos 1 e 4 apresentaram menores graus de microinfiltração marginal que o grupo 2 na parede cervical(p<0.05). A aplicação do sistema adesivo de dois passos associado a polimerização com luz halógena promoveram os menores graus de microinfiltração marginal.

The aim of this research was to analyze the effectiveness of conventional and self-etching bonding systems and different curing methods for reduction of marginal microleakage. 48 bovine incisor teeth were used in this study. The teeth were divided into four groups of 12 samples according to the type of adhesive system or curing method used: Group 1- Two-step bonding system photoactivated by halogen light with intensity of 700 mW/cm2; Group 2- Two-step bonding system photoactivated by LED with 470 mW/ cm2 of intensity; Group 3 - Self etch bonding system photoactivated by halogen light; Group 4- Self etch bonding system photoactivated by LED. A nanofilled composite resin was used to restore all the cavities. Then the groups were subjected to thermal cycling treatment and were placed for 24 hours in a methylene blue solution. The microleakage was assessed according to the degree ofpenetration of the colorant in tooth-restoration interface. For statistical analysis, the non-parametric Kruskal Wallis test complemented by Mann-Whitney were used with 5 % level of significance. The Group 1 showed lower marginal microleakage than Group 2 on occlusal wall (p<0.05). Adittionally, appears and the groups 1 and 4 had smaller degrees of marginal microleakage that the cervical wall 2 Group (p<0.05). The application of two-step bonding system associated with the polymerization by halogen light promoted the lowest degrees of marginal microleakage.

Environmental impact of industrial sludge stabilization/solidification products: chemical or ecotoxicological hazard evaluation?

Nowadays, the classification of industrial solid wastes is not based on risk analysis, thus the aim of this study was to compare the toxicity classifications based on the chemical and ecotoxicological characterization of four industrial sludges submitted to a two-step stabilization/solidification (S/S) processes. To classify S/S products as hazardous or non-hazardous, values cited in Brazilian chemical waste regulations were adopted and compared to the results obtained with a battery of biotests (bacteria, alga and daphnids) which were carried out with soluble and leaching fractions. In some cases the hazardous potential of industrial sludge was underestimated, since the S/S products obtained from the metal-mechanics and automotive sludges were chemically classified as non-hazardous (but non-inert) when the ecotoxicity tests showed toxicity values for leaching and soluble fractions. In other cases, the environmental impact was overestimated, since the S/S products of the textile sludges were chemically classified as non-inert (but non-hazardous) while ecotoxicity tests did not reveal any effects on bacteria, daphnids and algae. From the results of the chemical and ecotoxicological analyses we concluded that: (i) current regulations related to solid waste classification based on leachability and solubility tests do not ensure reliable results with respect to environmental protection; (ii) the two-step process was very effective in terms of metal immobilization, even at higher metal-concentrations. Considering that S/S products will be subject to environmental conditions, it is of great interest to test the ecotoxicity potential of the contaminants release from these products with a view to avoiding environmental impact given the unreliability of ecotoxicological estimations originating from chemical analysis.

Assembled modules technology for site-specific prolonged delivery of norfloxacin.

The aim of this research was to design and study norfloxacin (NFX) release in floating conditions from compressed hydrophilic matrices of hydroxypropylmethylcellulose (HPMC) or poly(ethylene oxide) (PEO). Module assembling technology for drug delivery system manufacturing was used. Two differently cylindrical base curved matrix/modules, identified as female and male, were assembled in void configuration by friction interlocking their concave bases obtaining a floating release system. Drug release and floatation behavior of this assembly was investigated. Due to the higher surface area exposed to the release medium, faster release was observed for individual modules compared to their assembled configuration, independently on the polymer used and concentration. The release curves analyzed using the Korsmeyer exponential equation and Peppas & Sahlin binomial equation showed that the drug release was controlled both by drug diffusion and polymer relaxation or erosion mechanisms. However, convective transport was predominant with PEO and at low content of polymers. NFX release from PEO polymeric matrix was more erosion dependent than HPMC. The assembled systems were able to float in vitro for up to 240min, indicating that this drug delivery system of norfloxacin could provide gastro-retentive site-specific release for increasing norfloxacin bioavailability.

Liquid chromatographic determination of lumiracoxib in pharmaceutical formulations.

A stability-indicating reversed-phase liquid chromatography (LC) method was developed and validated for the determination of lumiracoxib in pharmaceutical formulations. The LC method was carried out on a Synergi fusion C(18) column (150 mmx4.6mm), maintained at 30 degrees C. The mobile phase was composed of phosphoric acid (25 mM; pH 3.0)/acetonitrile (40:60, v/v), run at a flow rate of 1.0mL/min, and detection at 272nm. The chromatographic separation was obtained within 10 min and it was linear in the concentration range of 10-100 microg/mL (r(2)=0.9999). Validation parameters such as the specificity, linearity, precision, accuracy, and robustness were evaluated, giving results within the acceptable range. Stress studies were carried out and no interference of the degradation products was detected. Moreover, the proposed method was successfully applied for the assay of lumiracoxib in pharmaceutical formulations.