Confocal Raman Microscopy Research Articles

Enteric-coating film effect on the delayed drug release of pantoprazole gastro-resistant generic tablets.

Background: Enteric coating films in acidic labile tablets protect the drug molecule from the acidic environment of the stomach. However, variations in the excipients used in the coating formulation may affect their ability to provide adequate protection. This study is the first to investigate the potential effects of coating materials on the protective functionality of enteric coating films for pantoprazole (PNZ) generic tablets after their recall from the market. Methods: A comparative analysis was conducted between generic and branded PNZ products, using pure drug powder for identification. The in vitro release of the drug was evaluated in different pH media. The study also utilized various analytical and thermal techniques, including differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform infrared (FTIR), and confocal Raman microscopy. Results: The in vitro assessment results revealed significant variations in the release profile for the generic product in acidic media at 120 min. DSC and TGA thermal profile analyses showed slight variation between the two products. XRD analysis exhibited a noticeable difference in peak intensity for the generic sample, while SEM revealed smaller particle sizes in the generic product. The obtained spectra profile for the generic product displayed significant variation in peaks and band intensity, possibly due to impurities. These findings suggest that the excipients used in the enteric coating film of the generic product may have affected its protective functionality, leading to premature drug release in acidic media. Additionally, the presence of polysorbate 80 (P-80) in the brand product might improve the properties of the enteric coating film due to its multi-functionality. Conclusions: In conclusion, the excipients used in the brand product demonstrated superior functionality in effectively protecting the drug molecule from acidic media through the enteric coating film, as compared to the generic version.

Facile and Low-Cost Fabrication of SiO2-Covered Au Nanoislands for Combined Plasmonic Enhanced Fluorescence Microscopy and SERS.

An easy and low-cost way to fabricate monometallic Au nanoislands for plasmonic enhanced spectroscopy is presented. The method is based on direct thermal evaporation of Au on glass substrates to form nanoislands, with thicknesses between 2 and 15 nm, which are subsequently covered by a thin layer of silicon dioxide. We have used HR-SEM and AFM to characterize the nanoislands, and their optical transmission reveals strong plasmon resonances in the visible. The plasmonic performance of the fabricated substrates has been tested in fluorescence and Raman scattering measurements of two probe materials. Enhancement factors up to 1.8 and 9×104 are reported for confocal fluorescence and Raman microscopies, respectively, which are comparable to others obtained by more elaborated fabrication procedures.

Metallomics as an Essential Analytical Tool for the Development of Potential Metallodrugs

Metallomics as an Essential Analytical Tool for the Development of Potential Metallodrugs

Single-Walled Carbon Nanotube-Guided Topical Skin Delivery of Tyrosinase to Prevent Photoinduced Damage.

When the skin is exposed to ultraviolet radiation (UV), it leads to the degradation of the extracellular matrix (ECM) and results in inflammation. Subsequently, melanocytes are triggered to induce tyrosinase-mediated melanin synthesis, protecting the skin. Here, we introduce a proactive approach to protect the skin from photodamage via the topical delivery of Streptomyces avermitilis-derived tyrosinase (SaTy) using single-walled carbon nanotube (SWNT). Utilizing a reverse electrodialysis (RED) battery, we facilitated the delivery of SaTy-SWNT complexes up to depths of approximately 300 μm, as analyzed by using confocal Raman microscopy. When applied to ex vivo porcine skin and in vivo albino mouse skin, SaTy-SWNT synthesized melanin, resulting in 4-fold greater UV/vis absorption at 475 nm than in mice without SaTy-SWNT. The synthesized melanin efficiently absorbed UV light and alleviated skin inflammation. In addition, the densification of dermal collagen, achieved through SaTy-mediated cross-linking, reduced photoinduced wrinkles by 66.3% in the affected area. Our findings suggest that SWNT-mediated topical protein delivery holds promise in tissue engineering applications.

Effects of glutathione on structural and digestibility properties of high-hydrostatic-pressure-gelatinized maize starch with different amylose/amylopectin ratios

The effect of glutathione (GSH) on the digestibility, physicochemical, and structural properties of maize starch under 600 MPa for 20 min of high hydrostatic pressure (HHP) treatment was determined by in vitro digestion, differential scanning calorimetry (DSC), scanning electronic microscopy (SEM), particle size distribution analysis, Fourier transforms infrared spectroscopy (FT-IR), and Laser Confocal Raman (LC-Raman) microscopy. The findings indicate that the waxy maize starch (WMS) underwent complete gelatinization, whereas the high amylose starches had partial gelatinization. GSH induced a significant increase (p ≤ 0.05) in the slowly digestible starch (SDS) content and a decrease in the rapidly digestible starch (RDS) after HHP treatment. Thermal analysis revealed that GSH increased starch gelatinization temperature. The gelatinization characteristics showed that GSH inhibited starch retrogradation but did not contribute much to starch crystallinity. FT-IR and LC-Raman analyses confirmed the interaction of GSH with starch molecules. The present result emphasizes the impact of GSH on the modelling of starch digestibility and structure properties and inspires the development of new functional foods prepared with HHP.

Characterization of rat vertebrae cortical bone microstructures using confocal Raman microscopy combined to tomography and electron microscopy

BackgroundThe rat vertebrae is a good model to study bone regeneration after implantation of biomaterials used to treat bone loss, a major problem in oral and dental surgery. However, the precise characterization of bone microstructures in the rat vertebrae has not been reported. Therefore, the aim of this study was to achieve the complete analysis of such bone, at different scales, in order to have a clear model of healthy bone for comparison with regenerated bone. MethodsIn order to image the cortical bone of rat caudal vertebra, confocal Raman microscopy was combined with high resolution X-ray micro computed tomography (micro-CT), with scanning electron microscopy (SEM) using backscatter electron imaging and with more conventional histology coloration techniques. SEM and Raman microscopy were done in various regions of the cortical bone corresponding to external, middle and internal areas. The spongy bone was imaged in parallel. Micro-CT was performed on the whole vertebra to monitor the network of haversian canals in the cortical bone. Osteonic canals characteristics, and relative chemical composition were analysed in several regions of interest, in cortical and spongy bone. Five rats were included in this study. ResultsOn micro-CT images, differences in intensity were observed in the cortical bone, substantiated by SEM. Chemical analysis with Raman spectra confirmed the difference in composition between the different regions of the cortical and spongy bone. PCA and k-mean cluster analysis separated these groups, except for the external and middle cortical bone. Peak intensity ratio confirmed these results with a CO3 to ν2 PO4 ratio significantly different for the internal cortical bone. Grayscale images stack extracted from micro-CT showed that global architecture of cortical bone was characterized by a dense and complex network of haversian osteonic canals, starting from the surface towards the vertebrae center. The mean diameter of the canals was 18.4 µm (SD 8.6 µm) and the mean length was 450 µm (SD 152 µm). Finally, Raman reconstructed images of the lamellar bone showed an enlargement of the lamellar layer width, both in circumferential lamellar bone and around haversian canals. ConclusionsMicro-CT and confocal Raman microscopy are good tools to complete classical analysis using optical and electron microscopy. The results and measurements presented in a rat model known for its small inter-individual differences provide the main characteristics of a mature bone. This study will allow the community working on this rat vertebrate model to have a set of characteristics, in particular on the structure of the haversian canals.

Best Practices to Quantify and Identify Particulate Matter on the Interior Surfaces of Single-Use Systems.

The manufacturing of a wide range of biopharmaceuticals, from antibodies and vaccines to cell-based therapies, increasingly takes place in single-use processing equipment. Manufactured in clean rooms and sealed and sterilized, single-use systems (SUSs) are ready-to-use and easily scalable. Controls in the "clean-build" manufacturing of SUSs reduce the probability of occurrence of particulate matter in SUSs. However, the size, complexity, and limited transparency of SUSs clearly limit the detectability of particulate matter on the interior (fluid-contacting) surfaces of a SUS during a visual inspection, as demonstrated in a recent study. In applications downstream of final filters or in aseptic processing, particulate matter on the surfaces of a SUS could detach and contaminate the final drug product. A realistic assessment of this risk requires reliable test methods that quantify and identify particulate matter present on the interior surfaces of SUSs. Clearly problematic is the common certification of the cleanliness of a SUS via a force-fit adaptation of the pharmacopeial standard USP <788> entitled "Particulate Matter in Injections". USP <788> does not describe a procedure for extraction of particulate matter from the interior surfaces of SUSs. In addition, application of Method 1 Light Obscuration significantly limits the probability of detection for particles in the visible size range (≥ 100 µm). In this article, we describe best practices for extracting, counting, sizing, and chemically identifying particulate matter on the interior surfaces of SUSs. Highly effective procedures for the extraction of particulate matter result from application of the qualification methodology described in a recently published ASTM standard. Filtration of the liquid extract concentrates particulate matter onto the surface of a membrane filter, allowing rapid particle counting and sizing using automated membrane microscopy, along with detailed chemical identification using infrared microscopy and/or automated confocal Raman microscopy.

Optimization of pre-processing and data fusion strategies for multi-block spectroscopic characterization of cellular growth phases in the chlorophyte, Tetraselmis suecica

In an era where phytoplankton-based technologies are expanding, optimization for rapid cellular growth detection and detailed biochemical characterization is key to enhancing productivity. Hence, the complex analysis and development of highly sensitive and rapid in-vivo methods for precise real-time molecular monitoring of phytoplankton cells is imperative. Herein, a multi-block spectroscopic based methodology for the identification and characterization of molecular changes occurring across different growth phases in the chlorophyte species, Tetraselmis suecica, is presented. Confocal Raman microscopy with near-infrared (NIR) excitation spectra and concurrent excitation-emission fluorescence matrix (EEM) measurements were taken at different intervals across a twenty-day cell growth cycle period encompassing three distinct growth phases (exponential, stationary and decline). Three different data fusion strategies were explored: low-level, mid-level and a mixed level with subsequent multi-block model building using the Common Components and Specific Weights Analysis (CCSWA) algorithm. Various pre-processing sequences in regard to the raw data and single-block exploratory methods were evaluated for all three strategies and selected based on the optimum computed salience contribution towards the multi-block global components within each model. A detailed characterization of the biochemical changes happening within cellular growth phases of the chlorophyte species was constructed. Additionally, the study establishes a novel paradigm for data manipulation within a multi-block framework for complex spectroscopic data of biological cells, such as phytoplankton.

Investigation of interdiffusion between compatible polymers under static and co‐extrusion processing conditions

AbstractWhen two compatible polymer melts are brought into contact, a diffuse interphase is formed that governs the adhesion between them. The degree of interdiffusion is defined mainly by the processing conditions and the physico‐chemical properties of the materials. Despite the great industrial relevance of co‐extrusion in manufacturing multilayer structures, little research has dealt with interdiffusion under these processing conditions, where polymer‐polymer interfaces are subject to shear load. In this work, procedures for investigating interdiffusion both under static and real co‐extrusion flow conditions were developed. Using various grades of poly(methyl methacrylate) and styrene‐co‐acrylonitrile copolymer, we studied both theoretically and experimentally the effects of interfacial contact time, temperature, material compatibility, and interfacial shear stress on interdiffusion. Spectroscopic analysis of the interfaces using confocal Raman microscopy showed that the general relationships between interdiffusion, time (Fick's law) and temperature (Arrhenius relationship) are identical under both static and co‐extrusion conditions. However, the interdiffusion rate is significantly higher under shear influence. Since the prediction of the interdiffusion process supports material selection and process design in multilayer manufacturing, a simple analytical model was developed to quantify the effects of aforementioned material properties and processing conditions on the apparent mutual interdiffusion coefficient.

Metabolome and Transcriptome Analysis of Sulfur-Induced Kiwifruit Stem Laccase Gene Involved in Syringyl Lignin Synthesis against Bacterial Canker.

Kiwifruit canker is caused by Pseudomonas syringae pv. actinidiae and is one of the most destructive diseases of kiwifruit worldwide. Sulfur can improve the deposit of lignin in kiwifruit stems and induce disease resistance, but the action mechanism at the molecular level remains unclear. This omics-based study revealed that sulfur-induced S lignin synthesis contributes to disease resistance. Histological staining verified sulfur-enhanced total lignin deposition in kiwifruit stems. High-performance liquid chromatography and confocal Raman microscopy showed that sulfur-activated S lignin was mainly deposited in the cell corner. Metabolome and transcriptome analysis revealed that the levels of phenylpropanoid pathway S lignin precursors sinapic acid and sinapyl alcohol were significantly increased and 16 laccase genes were upregulated. Sulfur-induced resistance defense promoted elevated laccase activity by activating the laccase genes, participating in sinapic acid and sinapyl alcohol substance synthesis, and ultimately polymerizing S lignin at cell corner against kiwifruit canker disease.

In situ synthesis of gold nanoparticles on layered double hydroxide nanoparticles for multiplexing molecular imaging of single cells

Quasi-spherical gold nanoparticles (AuNPs) are the most widely used surface-enhanced Raman scattering (SERS) nanotags. However, their surface plasmon resonance properties are significantly restricted by their poor colloidal stability in biological media. Herein, we developed a new strategy for in situ synthesis of AuNPs on layered double hydroxide (LDH) nanoparticles to improve the colloidal stability of AuNPs for SERS imaging with multiplexing capability using single laser excitation. The hybridized LDH-AuNPs were constructed via in situ growth of AuNPs on lactic acid-LDH nanoparticles. The size of AuNPs was tuned by changing the concentration of LDH. The LDH-AuNPs were further functionalized with Raman reporter molecules (Ra) to obtain LDH-AuNPs-Ra as SERS nanotags, which were examined in terms of the colloidal stability and photostability in biological media as well as cellular uptake in J774A.1 macrophage cell culture by single cell mapping via confocal Raman microscopy. The cellular uptake of multiple LDH-AuNPs-Ra functionalized with different Raman reporter molecules were further investigated, where the multiplexing capability of SERS assay endows simultaneous detection of multiple LDH-AuNPs-Ra distribution after cellular uptake for cell imaging. In summary, the LDH-supported in situ synthesis of AuNPs have shown the merits of stabilizing AuNPs by using LDH for SERS imaging, as well as demonstrating the multiplexing molecular imaging of single cells. This work thus provides a promising strategy and a new bioimaging nanoplatform for various biomedical studies in the near future.

Li-Ion and Na-Ion Intercalation in Layered MnO2 Cathodes Enabled by Using Bismuth as a Cation Pillar

Rechargeability of low-cost MnO2 cathodes in aqueous cells has the potential to be an enabling technology for low-cost (<$50/kWh) grid-scale batteries. This rechargeability is imparted by modifying the MnO2 with Bi. In this talk we detail using Bi doping for structural stabilization of MnO2 cathodes for Li-ion and Na-ion batteries in dry, non-aqueous electrolyte. We do this by preparing a series of Bi-doped layered MnO2 compounds, which also contain K ions and crystal water. These phyllomanganates or birnessite-type compounds have the general formula KxBiy-MnO2 • nH2O. The materials are structurally characterized by synchrotron X-ray powder diffraction (XPD) and confocal Raman microscopy. It is found that incorporation of Bi in the structure increases the crystallinity of the material by ordering the interlayer cations. This ordering results in the emergence of a structural superlattice in the material, which has been reported previously for birnessite inserted with other heavy, multivalent cations such as as Sr2+, Ba2+, and Ca2+.We selected three Bi doping levels to study in Li-ion and Na-ion batteries: undoped (y = 0), low-doping (y = 0.013 or 1.3%), and high doping (y = 0.043 or 4.3%). Both doped materials had capacity over 200 mAh/g and allowed for far more stable cell cycling than the undoped Kx-MnO2. The cells made with 4.3% doping of Bi were by far more stable. These cycled at 175-190 mAh/g specific capacity through 100 cycles with a nominal voltage of 2.9 V. Operando XRD experiments to characterize the cathodes within sealed coin cells showed that high-level doping (4.3%) promoted dehydration of the KxBiy-MnO2 interlayer, which had a distance of 6.4 Å. This showed that loss of the crystal water from the interlayer was key to achieving maximum stability during cycling. Lower Bi doping (1.3%) did not cause loss of the crystal water once the cathode was wetted with electrolyte. Previous reports have suggested that Bi doping of 20% results in stabilized Li-ion cycling in layered MnO2. However, these reports involved largely amorphous active material. Our results showed that Bi doping of only 1.3% still provided a large stability benefit, and the high crystallinity of our material allowed it to be structurally characterized, both in the as-prepared state and operando during battery cycling. Results from Na-ion cells will also be presented.Stabilized MnO2-based cathodes that cycle with good capacity and somewhat lower cell voltage than traditional Li-ion cells are a promising strategy for low-cost batteries for the grid. The possibility of using Na as the working ion is also useful for large-scale deployment of batteries to balance renewable power. Acknowledgments This work was supported by the U.S. Department of Energy (DOE) Office of Electricity Delivery and Energy Reliability, Dr. Imre Gyuk, Energy Storage Program Manager. This research used resources of the Advanced Photon Source beamline 6-BM, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. This research also used resources at beamlines 7-BM (QAS) and 28-ID-2 (XPD) of the National Synchrotron Light Source II, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory under Contract No. DE-SC0012704.

Quantification of skin penetration of caffeine and propylene glycol applied topically in a mixture by tailored multivariate curve resolution-alternating least squares of depth-resolved Raman spectra.

The quantitative determination of topically applied substances in the skin is severely limited and represents a challenging task. The porcine skin ex vivo was topically treated with a gel containing caffeine (CF) and propylene glycol (PG), and depth-resolved Raman spectra were recorded with two confocal Raman microscopes. We applied a novel tailored multivariate curve resolution-alternating least squares method to the selected spectral regions (512-604 and 778-1148 cm-1 ) of gel-treated skin and quantitatively determined the concentrations of CF and PG in the stratum corneum (SC). The highest concentration of CF (181 mg/cm3 ) was found at the surface, while PG (384 mg/cm3 ) was found at 10% SC depth, indicating the formation of a reservoir at the superficial SC. The concentrations of CF and PG decreased monotonically and reached the detection limit at ≈60% and ≈80% SC depth, respectively, indicating that neither permeate the SC.

Fundamental mechanistic insights into the catalytic reactions of Li─S redox by Co single-atom electrocatalysts via operando methods.

Lithium-sulfur batteries represent an attractive option for energy storage applications. A deeper understanding of the multistep lithium-sulfur reactions and the electrocatalytic mechanisms are required to develop advanced, high-performance batteries. We have systematically investigated the lithium-sulfur redox processes catalyzed by a cobalt single-atom electrocatalyst (Co-SAs/NC) via operando confocal Raman microscopy and x-ray absorption spectroscopy (XAS). The real-time observations, based on potentiostatic measurements, indicate that Co-SAs/NC efficiently accelerates the lithium-sulfur reduction/oxidation reactions, which display zero-order kinetics. Under galvanostatic discharge conditions, the typical stepwise mechanism of long-chain and intermediate-chain polysulfides is transformed to a concurrent pathway under electrocatalysis. In addition, operando cobalt K-edge XAS studies elucidate the potential-dependent evolution of cobalt's oxidation state and the formation of cobalt-sulfur bonds. Our work provides fundamental insights into the mechanisms of catalyzed lithium-sulfur reactions via operando methods, enabling a deeper understanding of electrocatalysis and interfacial dynamics in electrical energy storage systems.

Highly Sensitive Sensor for the Determination of Riboflavin Using Thionine Coated Cadmium Selenide Quantum Dots Modified Graphite Electrode

In this paper, the electrochemical non-enzymatic detection of Riboflavin (RF) was proposed based on its catalytic reduction in a Thionine-coated Cadmium Selenide Quantum dots (TH@CdSe QDs)-modified paraffin wax-impregnated graphite electrode (PIGE) that was prepared using a novel approach. The synthesized TH@CdSe QDs were confirmed by UV-Vis spectroscopy, Confocal Raman Microscopy and High Resolution Transmission Electron Microscopy (HRTEM) studies. The electrochemical response of the TH@CdSe QDs-modified PIGE was studied by cyclic voltammetry. The voltammetric response of RF at the TH@CdSe QDs-modified PIGE showed higher current than the bare PIGE. Under optimum conditions, the electrocatalytic reduction currents of RF was found to be linearly related to its concentration over the range of 1.6 × 10−7 M to 1.4 × 10−4 M with a detection limit of 53 × 10−9 M (S/N = 3). The TH@CdSe QDs-modified PIGE was utilized as an amperometric sensor for the detection of RF in flow systems was performed by carrying out hydrodynamic and chronoamperometric experiments. The TH@CdSe QDs-modified PIGE showed very good stability and a longer shelf life. The applicability of the fabricated electrode was justified by the quantification of RF in commercial tablets.

Correlation between structure and mechanical properties in α-quartz single crystal by nanoindentation, AFM and confocal Raman microscopy

Quartz constitutes a very useful material due to its variety of applications, highlighting solid-state physics for material science with applications for devices and sensors, as piezoelectric for microbalances or oscillators for watches, computers, etc. These applications are very sensible to local pressures and stresses, however, there is not much information in the literature about the effect of high local pressures on the structure and their correlation with mechanical properties. In order to provide more information and clarity on this type of stress-structure-mechanical properties correlation, in this work, nanoindentation combined with Raman Confocal microscopy was carried out since it offers a powerful method to obtain information about the structural deformation and mechanical properties produced by high local pressures in α-quartz single crystal. The information obtained by nanoindentation (pile-up, pop-out, hardness and Υoung modulus) has been correlated with the structural data extracted from Raman spectroscopy, concluding that a permanent plastic deformation occurs under the indentation footprint, sharply appearing a new denser phase, which contribution increases with the applied load.

In-situ grafting of dextran on oil body associated proteins at the oil–water interface through maillard glycosylation: Effect of dextran molecular weight

Oil bodies, which are lipid-storage organelles in plant seeds, are stabilized by monolayer of phospholipids and oil body associated proteins (OBAPs). OBAPs have unique interfacial characteristics but poor water-solubility because they contain long hydrophobic segments. In this paper, dextran with different molecular weights (5, 10, and 20 kDa) was grafted onto the C- and N-terminal ends of OBAPs through in situ Maillard reaction on the surface of oil bodies. Grafting of dextran increases the length of the hydrophilic region of OBAPs, which improves their solubility and function as interfacial stabilizers. Changes in chemical bonds after grafting were observed via confocal-Raman microscopy. After de-lipidization, the physicochemical properties of OBAPs–dextran conjugates were analyzed using solubility and infrared spectroscopy. The interfacial behavior was evaluated using critical micelle concentration and interfacial rheology. The results showed that grafting of dextran improved the solubility of the OBAPs by 20-fold. The contents of α-helix and β-sheet in the OBAPs–dextran conjugates decreased, when compared with OBAPs. The critical micelle concentration of OBAPs–dextran conjugates ranged from 1.20 to 4.92 μg/mL. Grafting of dextran, especially high molecular weight, improved the capacity of the OBAPs to increase the interfacial pressure. Our results provide an efficient and eco-friend method for modification of membrane proteins.

Biochemical characterization and mercury methylation capacity of Geobacter sulfurreducens biofilms grown in media containing iron hydroxide or fumarate

Geobacter species are common in iron-rich environments and can contribute to formation of methylmercury (MeHg), a neurotoxic compound with high bioaccumulation potential formed as a result of bacterial and archaeal physiological activity. Geobacter sulfurreducens can utilize various electron acceptors for growth including iron hydroxides or fumarate. However, it remains poorly understood how the growth on these compounds affects physiological properties of bacterial cells in biofilms, including the capacity to produce MeHg. The purpose of this study was to determine changes in the biochemical composition of G. sulfurreducens during biofilm cultivation in media containing iron hydroxide or fumarate, and to quantify mercury (Hg) methylation capacity of the formed biofilms. Biofilms were characterized by Fourier-transform infrared spectroscopy in the attenuated total reflection mode (ATR-FTIR), Resonance Raman spectroscopy and confocal laser scanning microscopy. MeHg formation was quantified by mass spectrometry after incubation of biofilms with 100 nM Hg. The results of ATR-FTIR experiments showed that in presence of fumarate, G. sulfurreducens biofilm formation was accompanied by variation in content of the energy-reserve polymer glycogen over time, which could be cancelled by the addition of supplementary nutrients (yeast extract). In contrast, biofilms cultivated on Fe(III) hydroxide did not accumulate glycogen. The ATR-FTIR results further suggested that Fe(III) hydroxide surfaces bind cells via phosphate and carboxylate groups of bacteria that form complexes with iron. Furthermore, biofilms grown on Fe(III) hydroxide had higher fraction of oxidized cytochromes and produced two to three times less biomass compared to conditions with fumarate. Normalized to biofilm volume, the content of MeHg was similar in assays with biofilms grown on Fe(III) hydroxide and on fumarate (with yeast extract and without). These results suggest that G. sulfurreducens biofilms produce MeHg irrespectively from glycogen content and cytochrome redox state in the cells, and warrant further investigation of the mechanisms controlling this process.

Tailoring the release of drugs having different water solubility by hybrid polymer-lipid microparticles with a biphasic structure

The aim of this study is to investigate the potential of hybrid polymer-lipid microparticles with a biphasic structure (b-MPs) as drug delivery system. Hybrid b-MPs of Compritol®888 ATO as main lipid constituent of the shell and polyethylene glycol 400 as core material were produced by an innovative solvent-free approach based on spray congealing. To assess the suitability of hybrid b-MPs to encapsulate various types of APIs, three model drugs (fluconazole, tolbutamide and nimesulide) with extremely different water solubility were loaded into the polymeric core. The hybrid systems were characterized in terms of particle size, morphology and physical state. Various techniques (e.g. optical, Confocal Raman and Scanning Electron Microscopy) were used to investigate the influence of the drugs on different aspects of the b-MPs, including external and internal morphology, properties at the lipid/polymer interface and drug distribution. Hybrid b-MPs were suitable for the encapsulation of all drugs (encapsulation efficiency > 90 %) regardless the drug hydrophobic/hydrophilic properties. Finally, the drug release behaviors from hybrid b-MPs were studied and compared with traditional solid lipid MPs (consisting of only the lipid carrier). Due to the combination of lipid and polymeric materials, hybrid b-MPs showed a wide array of release profiles that depends on their composition, the type of loaded drug, the drug loading amount and location, providing a versatile platform and allowing the formulators to finely balance the release performance of drugs intended for oral administration. Overall, the study demonstrates that hybrid, solvent-free b-MPs produced by spray congealing are an extremely versatile delivery platform able to efficiently encapsulate and release very different types of drug compounds.

Unveiling Structural Insights into Nanocrystal-Doped Optical Fibers via Confocal Raman Microscopy.

An in-depth characterization of nanoparticle-doped optical fibers is crucial to understand the potential new functionalities of the engineered glass and thus their applicability fields. The high temperatures of the manufacturing process strongly affect the nanoparticle features, and therefore, their analysis is necessary after fiber drawing. However, the difficulties associated with the use of atomic resolution microscopies to analyze the nanoparticle features in the fiber core, mainly related to sample preparation and expensive costs, usually prevent their study. In this work, we overcome some of those limitations and demonstrate, for the first time, the suitability of structurally and microstructurally studying in detail nanocrystals contained in a fiber core of ∼10 μm by combining confocal Raman microscopy, Rayleigh light-scattering microscopy, and scanning electron microscopy (SEM). A thorough study of cubic-shaped and rod-shaped YPO4 nanocrystals contained in optical fibers reveals their crystallization in tetragonal (t) and monoclinic (m) structures, respectively. The symmetric (ν1) and asymmetric stretching (ν3) Raman modes display a different and remarkable red shift as particle size decreases in both types of nanocrystals, which in the case of the cubic-shaped nanocrystals is fitted to an exponential function along with a Raman peak broadening. Moreover, their Raman dependence vs temperature is evaluated up to 600 °C, observing a phonon softening that follows a linear behavior, which is discussed in detail. These findings add new insights to pure m-YPO4, which was unknown to date, and the REPO4 family and open up new avenues that can be extrapolated to other nanostructures incorporated into optical fiber cores, which will advance progress in the field of nanoparticle-doped optical fibers.