Monomodal Particle Size Distribution Research Articles

Nanogels Based on N,N-Dimethylacrylamide and β-Cyclodextrin Triacrylate for Enhanced Solubility and Therapeutic Efficacy of Aripiprazole.

Aripiprazole (ARZ) is a medication used for the treatment of various diseases such as schizophrenia, bipolar disorder, major depressive disorder, autism, and Tourette's syndrome. Despite its therapeutic benefits, ARZ is characterized by a poor water solubility which provoked the development of various delivery systems in order to enhance its solubility. In the present work, a nanoscale drug delivery system based on N,N-dimethylacrylamide (DMAA) and β-cyclodextrin triacrylate (β-CD-Ac3) as potential aripiprazole delivery vehicles was developed. The nanogels were synthesized by free radical polymerization of DMAA in the presence of β-CD-Ac3 as a crosslinking agent and then loaded with ARZ via host-guest inclusion complexation. The blank- and drug-loaded nanogels were evaluated using different methods. Fourier transform infrared (FTIR) spectroscopy was employed to confirm the incorporation of β-CD moieties into the polymer network. Dynamic light scattering (DLS) was used to study the size of the developed systems. The samples exhibited a monomodal particle size distribution and a relatively narrow dispersity index. The hydrodynamic diameter (Dh) of the gels varied between 107 and 129 nm, with a tendency for slightly larger particles as the β-CD-Ac3 fraction increased. Loading the drug into the nanocarrier resulted in slightly larger particles than the blank gels, but their size was still in the nanoscopic range (166 to 169 nm). The release profiles in PBS were studied and a sustained release pattern with no significant burst effect was observed. A cytotoxicity assessment was also conducted to demonstrate the non-toxicity and biocompatibility of the studied polymers.

Investigation of the Interaction between Mechanosynthesized ZnS Nanoparticles and Albumin Using Fluorescence Spectroscopy.

In this paper, ZnS nanoparticles were bioconjugated with bovine serum albumin and prepared in a form of nanosuspension using a wet circulation grinding. The stable nanosuspension with monomodal particle size distribution (d50 = 137 nm) and negative zeta potential (-18.3 mV) was obtained. The sorption kinetics and isotherm were determined. Interactions between ZnS and albumin were studied using the fluorescence techniques. The quenching mechanism, describing both static and dynamic interactions, was investigated. Various parameters were calculated, including the quenching rate constant, binding constant, stoichiometry of the binding process, and accessibility of fluorophore to the quencher. It has been found that tryptophan, in comparison to tyrosine, can be closer to the binding site established by analyzing the synchronous fluorescence spectra. The cellular mechanism in multiple myeloma cells treated with nanosuspension was evaluated by fluorescence assays for quantification of apoptosis, assessment of mitochondrial membrane potential and evaluation of cell cycle changes. The preliminary results confirm that the nontoxic nature of ZnS nanoparticles is potentially applicable in drug delivery systems. Additionally, slight changes in the secondary structure of albumin, accompanied by a decrease in α-helix content, were investigated using the FTIR method after analyzing the deconvoluted Amide I band spectra of ZnS nanoparticles conjugated with albumin. Thermogravimetric analysis and long-term stability studies were also performed to obtain a complete picture about the studied system.

Pre-filter analysis for retrieval of microphysical particle parameters: a quality-assurance method applied to 3 backscatter (β) +2 extinction (α) optical data taken with HSRL/Raman lidar.

We analyze the solution space of 3β+2α optical data inferred from lidar measurements, i.e., backscatter coefficients at three wavelengths and extinction coefficients at two wavelengths. These optical data are governed by microphysical parameters that can be expressed in terms of particle size distribution, effective radius, and complex refractive index (CRI). In our analysis, we consider two scenarios of the solution space. First, it can be expressed in terms of monomodal particle size distributions represented either by fine modes or by coarse modes. Secondly, the particle size distributions contain a fine mode as well as a coarse mode. Consideration of both scenarios and different values of the effective radius and CRI allows us to find synthetic 3β+2α optical data and corresponding intensive parameters (IPs) such as lidar ratios, backscatter- and extinction-related Ångström exponents at the available measurement wavelengths. Based on interdependencies between synthetic IPs and various microphysical properties, the qualitative and quantitative criteria for the optical data quality-assurance tool are developed. We derive the conditions of smoothness, closeness, convergence, and stability of the solution space for the quantitative criteria to test the quality of the 3β+2α optical data. Our novel methodology, to the best of our knowledge, can be used not only for particles of spherical shape, but also for cases in which particles are irregularly shaped. Another strength of our methodology is that it also works for the case of a size-dependent and wavelength-dependent CRI. We show the potential of this methodology for a measurement case from the ORACLES campaign. Data were taken with NASA Langley's airborne HSRL-2 instrument on September 24, 2016.

The Formation of NaYF4:Er3+,Yb3+ Nanocrystals Studied by In Situ X-ray Scattering: Phase Transition and Size Focusing.

β-NaYF4 nanocrystals are a popular class of optical materials. They can be doped with optically active lanthanide ions and shaped into core-multi-shell geometries with controlled dopant distributions. Here, we follow the synthesis of β-NaYF4 nanocrystals from α-NaYF4 precursor particles using in situ small-angle and wide-angle X-ray scattering and ex-situ electron microscopy. We observe an evolution from a monomodal particle size distribution to bimodal, and eventually back to monomodal. The final size distribution is narrower in absolute numbers than the initial distribution. These peculiar growth dynamics happen in large part before the α-to-β phase transformation. We propose that the splitting of the size distribution is caused by variations in the reactivity of α-NaYF4 precursor particles, potentially due to inter-particle differences in stoichiometry. Rate equation modeling confirms that a continuous distribution of reactivities can result in the observed particle growth dynamics.

Improvement of suspension-assisted total reflection X-ray fluorescence analysis of ores using wet grinding and empirical calibrations

In this study, the suspension-assisted total-reflection X-ray fluorescence analysis of ores was improved using the wet grinding procedure to produce ultra-fine suspended powder mixed with internal standard solution in aqueous media. The advantages of the proposed technique were demonstrated by the example of the determination of S, Fe, Ni, and Cu in sulfide copper‑nickel ores containing various ratios of sulfide and silicate minerals. We showed that the powerful mixing of 100 mg of ore powder and 4 mL of ultra-pure water as a dispersing medium with 20 g of grinding balls of 1 mm in diameter leads to the preparation of homogeneous suspension with monomodal particle size distribution having 90% of the particle size <6 μm. The suspension after wet grinding was diluted up to 50 mL with ultra-pure water to obtain a final concentration of the suspended powder of 2 mg/mL. Relative precision of the described sample preparation technique calculated from duplicate pairs of suspensions was 16% for S, 9% for Fe, 15% for Ni and 10% for Cu. Three spectral data processing techniques were further compared with respect to the quantification accuracy of target elements: internal standard, univariate and multivariate regressions. It was shown that the two latter methods can be used to improve the trueness of the internal standard method, especially for Cu and Fe.

Use of seaweed powder (Undaria sp.) as a functional ingredient in low-fat pork burgers

Seaweeds are a valuable resource for food development due to their nutritional composition and technological properties. This work aimed to evaluate Undaria sp. powder (UP) properties and its performance as a functional ingredient in low-fat pork burgers. UP proximal composition, physicochemical, and functional properties were evaluated. UP showed a monomodal particle size distribution, low moisture, and low water activity. It showed both high mineral (26.5 g/100 g db) and total dietary fiber (40.685 g/100 g db) contents. UP lipid level was low (5.2 g/100 g db). The fatty acid profile presented high proportions of SFA and MUFA (48.8 % and 38.2 %, respectively), followed by PUFA (13 %), with palmitic (C16:0; 36.9 %) and oleic acids (C18:1n-9; 34.4 %) in the highest abundance. Concerning UP properties, it retained more water than lipids; its total phenolic content reached 15.50 mg GAE/g, and the antioxidant capacity was 29.42 and 34.50 μmol TE/g for DPPH and ABTS methods, respectively. Burgers were manufactured with UP or milk protein concentrate (MPC) as emulsifiers, packaged, and stored frozen. Formulation and storage time effects on the product's physicochemical and techno-functional properties were evaluated. The UP addition to burgers increased yields, hardness, and chewiness, while reduced shrinkages in comparison with control burgers with MPC. Although the color was adversely affected by the formulation, it was balanced with carmine addition. Even though the UP burgers showed higher antioxidant capacity, lipid oxidation increased during storage and with UP incorporation. UP addition did not affect the product's fatty acid profiles or fat contents. Therefore, UP could be an adequate strategy for developing meat products with improved techno-functional and antioxidant properties.

Casein-dextran complexes subjected to microfiltration: Colloidal properties and their corresponding processing behaviors

In this work, protein-polysaccharide complexes were subjected to microfiltration, a typical multi-force process. Particle and flow properties of casein-dextran complexes were analyzed in various solution conditions, and their processing behaviors of microfiltration, elucidated by resistance, fouling propensity and interaction with porous polymer surface, were also investigated. Results suggested that the medium pH and the casein/dextran ratio had significant influences on particle and rheological properties of such complexes, and then led to notable different processing behaviors of microfiltration. Being subjected to the process of microfiltration, casein-dextran complexes of monomodal particle size distribution formed a compact and smooth cake layer on the membrane surface, which was resistant, and later-coming particles were easy to deposit on previously settled ones. Therefore, the growth rate of fouling was high and the transition of complex/membrane interaction regime was quite fast from complete pore blocking to cake formation mechanism. On the contrary, the complex of multimodal particle size distribution may easily form a loose and rough layer on the membrane surface while partially blocked the membrane pore entrance, which was less resistant. Consequently, the growth of such fouling layer was hindered, which then resulted in the slow-down of the transition from one regime to another (from complete pore blocking to standard pore blocking then to intermediate pore blocking mechanism). This work provides generalized and pertinent guidance for microfiltration of protein-polysaccharide complexes.

Nanocomposite powder for powder-bed-based additive manufacturing obtained by dry particle coating

Several dry processing techniques are assessed to elaborate metallic nanocomposite powders dedicated to powder-bed-based (PBB) additive manufacturing as laser-powder bed fusion (L-PBF) and Binder Jetting (BJ). Electrostatic assembly of nanosized silicon carbide (35 nm) particles at the surface of gas atomized aluminium powders (15-53 μm) is performed using mixers covering a range of mixing energy from rotative drum mixer to high energy mixers such as high shear paddle and acoustic mixers. Analyses of particle size distribution (PSD) of powders mixtures show that only high-energy mixers bring to a monomodal PSD describing a complete electrostatic assembly of nanoparticles. Statistic image analysis confirms the absence of plastic deformation of aluminium particles during mixing. The coating leads to a drastic increase of starting host powder flowability and apparent density, while reducing the host powder optical reflectivity. Finally, a surface oxidation of SiC nanoparticles affects the coating efficiency.

Evaluation of Rare-earth Sesquioxides Nanoparticles as a Bottom-up Strategy Toward the Formation of Functional Structures

Background: The strategy to form functional structures based on powder technology relies on the concept of nanoparticles characteristics. Rare-earth sesquioxides (RE2O3; RE as Y, Tm, Eu) exhibit remarkable properties, and their fields of application include energy, astronomy, environmental, medical, information technology, industry, and materials science. The purpose of this paper is to evaluate the characteristics of RE2O3 nanoparticles as a bottom-up strategy to form functional materials for radiation dosimetry. Methods: The RE2O3 nanoparticles were characterized by the following techniques: XRD, SEM, PCS, FTIR, ICP, EPR, and zeta potential. Results: All RE2O3 samples exhibited cubic C-type structure in accordance with the sesquioxide diagram, chemical composition over 99.9 %, monomodal mean particle size distribution, in which d50 value was inferior to 130 nm. Among all samples, only yttrium oxide exhibited an EPR signal, in which the most intense peak was recorded at 358mT and g 1.9701. Conclusion: Evaluating nanoparticle characteristics is extremely important by considering a bottom-up strategy to form functional materials. The RE2O3 nanoparticles exhibit promising characteristics for application in radiation dosimetry.

Acidic cesium salts of phosphotungstic acid: Morphology, water content and ionic conductivity

In this work, the effect of synthesis conditions (ratio and concentration of reagents) on the composition, morphology, water content and ion-conducting properties of CsxH3-xPW12O40 salts were studied. The morphology of the salts is mainly determined by the concentrations of the reagents during the synthesis. At a higher concentration of reagents, the obtained salts have a relatively narrow, monomodal particle size distribution and a large specific surface area. The composition of the salts depends both on the concentration of the reagents and on their ratio. Higher concentrations of reagents make it possible to obtain more acidic salts. Apparently, salts contain both adsorption and crystalline water. It is also assumed that the main charge carriers in these salts are protons, and their transport is carried out mainly through the network of adsorption water on the surface of the salts. The most promising for catalysis of the obtained salts has 1.2 ± 0.3 protons in its composition, a specific surface area of 136 ± 14 m2/g and an ionic conductivity of 0.05 S cm−1 at room temperature and 75% RH.

Nanostructured Lipid Carriers (NLC) for Biologically Active Green Tea and Fennel Natural Oils Delivery: Larvicidal and Adulticidal Activities against Culex pipiens.

(1) Background: The control of mosquitoes with essential oils is a growing demand. (2) Methods: This study evaluated the novel larvicidal and adulticidal activity of fennel and green tea oils and their nanostructured lipid carriers (NLC) against Culex pipiens (C. pipiens) in the laboratory, field conditions and evaluated their effect against non-target organisms. SLN type II nanoformulations were synthesized and characterized using dynamic light scattering (DLS), zeta potential and transmission electron microscope. (3) Results: The synthesized NLCs showed spherical shaped, homogenous, narrow, and monomodal particle size distribution. The mortality percent (MO%) post-treatment (PT) with 2000 ppm for 24 h with fennel oil and NLC fennel (NLC-F) reached 85% (LC50 = 643.81 ppm) and 100% (LC50 = 251.71), whereas MO% for green tea oil and NLC green tea (NLC-GT) were 80% (LC50 = 746.52 ppm) and 100% (LC50 = 278.63 ppm), respectively. Field trial data showed that the larval reduction percent of fennel oil and NLC-F reached 89.8% and 97.4%, 24 h PT and the reduction percent of green tea oil and NLC-GT reached 89% and 93%, 24 h PT with persistence reached 8 and 7 days, for NLC-F and NLC-GT, respectively. The adulticidal effects showed that NLC-F and NLC-GT (100% mortality) were more effective than fennel and green tea oils (90.0% and 83.33%), with 24 h PT, respectively. Moreover, their reduction of adult density after spraying with LC95 X2 for 15 min, with fennel oil, NLC-F, and green tea oil, NLC-GT were 83.6%, 100%, 79.1%, and 100%, respectively, with persistence (>50%) lasting for three days. The predation rate of the mosquitofish, Gambusia affinis, and the bug, Sphaerodema urinator, was not affected in both oil and its NLC, while the predation rate of the beetle, Cybister tripunctatus increased (66% and 68.3%) by green tea oil and NLC-GT, respectively. (4) Conclusions: NLCs nanoformulation encapsulated essential oils was prepared successfully with unique properties of size, morphology, and stability. In vitro larvicidal and adulticidal effects against C. pipiens supported with field evaluations have been performed using essential oils and their nanoformulations. The biological evaluation of nanoformulations manifested potential results toward both larvicidal and adulticidal compared to the essential oils themselves, especially NLC encapsulated fennel oil which had promising larvicidal and adulticidal activity.

Synthesis of Ti–Al Bimodal Powder for High Flowability Feedstock by Electrical Explosion of Wires

In this research, Ti–Al bimodal powders were produced by simultaneous electrical explosion of titanium and aluminum wires. The resulting powders were used to prepare powder–polymer feedstocks. Material characterization involving X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and melt flow index (MFI) determination were carried out to characterize bimodal powders obtained and evaluate the influence of the powder composition on the feedstock flowability. The bimodal distribution of particles in powders has been found to be achieved at a current density of 1.2 × 107 A/cm2 (the rate of energy input is 56.5 J/μs). An increase in the current density to 1.6 × 107 A/cm2 leads to a decrease in the content of micron particles and turning into a monomodal particle size distribution. The use of bimodal powders for powder–polymer feedstocks allows to achieve higher MFI values compared with monomodal powders. In addition, the use of electroexplosive synthesis of bimodal powders makes it possible to achieve a homogeneous distribution of micro- and nanoparticles in the feedstock.

Processing and characterization of Inconel 718/Al2O3 nanocomposite powder fabricated by different techniques

Inconel 718/Al2O3 nanocomposite powders produced by sonication-assisted high-energy ball milling (HEBM) and mechanofusion processes are presented and compared. Powders were pre-mixed via sonication in ethanol. Two pre-mixed batches were processed by HEBM using two different cooling temperatures and milling times. To investigate the influence of Al2O3 on the mechanical milling stages, Inconel 718 powder without alumina was also mechanically milled. Results show that the tested methods are able to produce Inconel 718/Al2O3 composite with suitable characteristics for further manufacturing or functionalization. A homogeneous dispersion of nanosized alumina throughout the metal matrix was only achieved by milling, showing a monomodal particle size distribution, with controlled both morphology and composition. Low cooling milling temperatures reduce Inconel 718/Al2O3 composite production time using less mechanical energy during milling. Sonication-assisted HEBM is an adequate method for the fabrication of non-commercial nanocomposites to be used as raw material in different manufacturing techniques.

Arrowroot starch ( Maranta arundinacea ) as a bread ingredient for product development

The goal of this study was to characterize the technological-functional, physical and thermal properties of arrowroot starch in order to better determine its role and effectiveness in the food industry, and then to evaluate its effect on bread properties. Arrowroot starch was characterized in relation to microstructure, x-ray diffraction, infrared spectroscopy, thermogravimetric, and technological-functional properties. Thereafter, breads with different wheat-arrowroot concentrations were produced, and characterized. Results evidenced that arrowroot starch presented monomodal particle size distribution, and circular, ellipsoid, and oval granules. Technological-functional properties showed increase in swelling power, solubility and water absorption index with the increase of temperature. Wheat-arrowroot bread were homogeneous and visually similar to control breads. Crumb hardness and volume were not significantly affected by arrowroot starch concentration when up to 30% of wheat flour was substituted. Therefore, it could be concluded that arrowroot starch represents a promising raw material to be explored in different food applications. Practical applications This study investigated the potential properties of arrowroot starch and its use in bread formulation, which finally provides to be a useful strategy to food industries in order to meet the suitable use of “new” materials for developing product. The results demonstrated that arrowroot starch presented interesting technological-functional and thermal properties in order to be used in bread development. Wheat-arrowroot breads were well produced, homogeneous, and visually similar to control breads, and bread produced with 30% of arrowroot starch presented crumb hardness and volume similar to control bread.

Colloidal stability of oil-in-water emulsions prepared from hen egg white submitted to dry and/or wet heating to induce amyloid-like fibril formation

Hen egg white (HEW) proteins are components of some foods and improvement of their techno-functional properties has been widely studied. During food processing, they are commonly subjected to heating. Here, both the impact of dry, wet, and combined dry and wet heat treatment was investigated. Heating (1 h at 80 °C) dried HEW (still containing 12% water) resulted in formation of glycated Maillard compounds such as protein-glucose conjugates, but only in limited amyloid-like fibril (ALF) formation. Wet heating (0.5 h at 80 °C, in excess water) clearly resulted in increased relative Thioflavin T (ThT) fluorescence, indicating the formation of ALFs. When dry heating (0.5 h at 80 °C) was followed by wet heating (24 h at 80 °C), the slightly lower relative ThT fluorescence than obtained when wet heating HEW suggested that ALF formation was limited due to protein glycation. When control (i.e. unheated) HEW dispersions and dispersions containing different heated HEW samples were used as continuous phase for oil-in-water emulsions, control HEW resulted in a multimodal particle size distribution and high creaming rate. In contrast, emulsions stabilized by dry and wet heated HEW showed an overall reduced volume-weighted average droplet diameter (D43) and increased creaming stability. HEW subjected to 4 h dry heat treatment at 80 °C and 24 h wet heat treatment at 80 °C resulted in emulsions with a monomodal particle size distribution with the smallest D43 (0.47 ± 0.01 μm), as well as the lowest creaming rate (68.4 ± 9.77 mm/day). Comparison of the relative ThT fluorescence, D43 and creaming rate by principal component analysis revealed that mainly the emulsions with dispersions having high relative ThT fluorescence had lower average particle sizes and consequently a higher creaming stability. Thus, formation of ALFs by wet heating of HEW seems to be the better heat treatment for improving their techno-functional properties.

Influence of the particle size distribution of monomodal 316L powder on its flowability and processability in powder bed fusion

Powder bed fusion (PBF) is the most commonly adopted additive manufacturing process for fabricating complex metal parts via the layer-wise melting of a powder bed using a laser beam. However, the qualification of PBF-manufactured parts remains challenging and expensive, thereby limiting the broader industrialization of the technology. Powder characteristics significantly influence part properties, and understanding the influencing factors contributes to effective quality standards for PBF. In this study, the influence of the particle size distribution (PSD) median and width on powder flowability and part properties is investigated. Seven gas-atomized SS316L powders with monomodal PSDs, a median particle size ranging from 10 μm to 60 μm, and a distribution width of 15 μm and 30 μm were analyzed and subsequently processed. The PBF-manufactured parts were analyzed in terms of density and melt pool dimensions. Although powder flowability was inversely related to the median particle size, it was unrelated to the distribution width. An inverse relationship between the median particle size and the part density was observed; however, no link was found to the distribution width. Likely, the melt pool depth and width fluctuation significantly influence the part density. The melt pool depth decreases and the width fluctuation increases with an increasing median particle size.

Enhanced stability and bioaccessibility of nobiletin in whey protein/cinnamaldehyde-stabilized microcapsules and application in yogurt

The stability of nobiletin was enhanced by converting emulsions into microcapsules. Nobiletin had much higher loading amount and bioaccessibility in microcapsules. CA addition modulated the crystal formation and bioaccessibility of nobiletin. Finally, nobiletin-fortified yogurt was produced by incorporating microcapsules. • Encapsulation by microcapsules increased the stability of nobiletin. • Nobiletin had much higher bioaccessibility in microcapsules than in emulsions. • CA addition modulated crystal formation and bioaccessibility of nobiletin. • Nobiletin-fortified yogurt was produced by incorporating microcapsules. Polymethoxylated flavones (nobiletin, tangeretin, etc) have excellent bioactivity, but low water-solubility and high crystallization. We developed the cinnamaldehyde (CA)-modified whey protein (WPC)-stabilized microcapsules (WPC/CA microcapsules) to encapsulate nobiletin. Microcapsules showed spherical structure and mono-modal particle size distribution after dispersing in water regardless of CA concentration. The presence of CA increased the stability of nobiletin in emulsions and microcapsules, and inhibited the formation of nobiletin crystals. in vitro digestion results demonstrated that nobiletin in microcapsules had much higher bioaccessibility (82 %–94 %) than that in emulsions (68 %–83 %). The presence of CA maintained or increased the bioaccessiiblity of nobiletin both in emulsions as well as microcapsules. The formation of nobiletin crystals in stomach decreased in WPC/CA microcapsules. The results suggested that nobiletin-fortified yogurts could be produced by adding WPC/CA microcapsules, rather than WPC/CA emulsions. Also, microcapsules-incorporated yogurt would have better physical stability, if the amount of WPC/CA microcapsules and nobiletin was carefully designed. The optimized amount of CA-loaded microcapsules was 2 %–4 % in yogurt and the nobiletin content was 13−26 mg/100 g yogurt. This knowledge can be of great significance for the development of delivery systems of polymethoxylated flavones and their functional foods.

Comparing Direct and Pulsed-Direct Current Electrophoretic Deposition on Neural Electrodes: Deposition Mechanism and Functional Influence.

Electrophoretic deposition (EPD) of platinum nanoparticles (PtNPs) on platinum-iridium (Pt-Ir) neural electrode surfaces is a promising strategy to tune the impedance of electrodes implanted for deep brain stimulation in various neurological disorders such as advanced Parkinson's disease and dystonia. However, previous results are contradicting as impedance reduction was observed on flat samples while in three-dimensional (3D) structures, an increase in impedance was observed. Hence, defined correlations between coating properties and impedance are to date not fully understood. In this work, the influence of direct current (DC) and pulsed-DC electric fields on NP deposition is systematically compared and clear correlations between surface coating homogeneity and in vitro impedance are established. The ligand-free NPs were synthesized via pulsed laser processing in liquid, yielding monomodal particle size distributions, verified by analytical disk centrifugation (ADC). Deposits formed were quantified by UV-vis supernatant analysis and further characterized by scanning electron microscopy (SEM) with semiautomated interparticle distance analyses. Our findings reveal that pulsed-DC electric fields yield more ordered surface coatings with a lower abundance of particle assemblates, while DC fields produce coatings with more pronounced aggregation. Impedance measurements further highlight that impedance of the corresponding electrodes is significantly reduced in the case of more ordered coatings realized by pulsed-DC depositions. We attribute this phenomenon to the higher active surface area of the adsorbed NPs in homogeneous coatings and the reduced particle-electrode electrical contact in NP assemblates. These results provide insight for the efficient EPD of bare metal NPs on micron-sized surfaces for biomedical applications in neuroscience and correlate coating homogeneity with in vitro functionality.

Preparation and Characterization of Cellulose and Microcrystalline Cellulose from Sugarcane Bagasse and Assessment of the Microcrystalline Cellulose as a Directly Compressible Excipient

Cellulose, the most abundant biomass material in nature finds wide applications in the pharmaceutical industry. Sugarcane bagasse (SCB) is one of the main agricultural lignocellulose byproducts. The objective of this study was to prepare and characterize native and microcrystalline cellulose (MCC) from SCB and evaluate the MCC as a directly compressible pharmaceutical excipient. Cellulose was extracted from SCB by chlorine-free methods with or without dewaxing. MCC was prepared from the cellulose by hydrolysis using hydrochloric acid, and subsequently oven-dried (OD) or spray-dried (SD). The as-obtained cellulose and MCC were characterized in terms of yield, degree of polymerization (DP), chemical functionality, crystallinity, morphology and thermal stability. The chemical composition, particle size, densities and direct compressibility of MCCs were also determined. Cellulose yields on a dry weight basis were found to be 42.8 ± 1.10% and 43.5 ± 0.5% from non-dewaxed and dewaxed SCB, respectively. Dewaxed SCB cellulose (DSCBC) provided higher yield of MCC (DSCB-MCCOD, 83 ± 0.74%) than non-dewaxed SCB cellulose (SCBC) (SCB-MCCOD; 78 ± 1.07%). The DP of SCBC and DSCBC were 580.56 and 592.75, respectively, while the DP of MCC ranged from 230.10 - 251.40. The FTIR spectra of both cellulose and MCC were similar with that of Avicel PH-101. The degree of crystallinity of the dewaxed cellulose (77.34%) and MCCOD (79.56%) and MCC-SD (81.87%) were higher than non-dewaxed cellulose (74.50%) and MCC-OD (78.11%) and MCC-SD (79.62%). Scanning electron micrographs (SEM) showed a fibrous structure for DSCBC and rod-shaped for DSCB-MCC. Thermogravimetric analysis (TGA) revealed dewaxed products exhibited better thermal stability than non-dewaxed products. All MCC samples exhibited monomodal normal particle size distributions. The Hausner ratio and Carr’s index of DSCB-MCCOD and Avicel PH-101 were not significantly different (p &lt; 0.05) indicating similar flow property and compressibility of the materials, respectively. Also, plain tablets prepared from SCB-MCC showed reasonably high crushing strengths (MCC-SD &gt; MCC-OD), although tablets of Avicel PH-101 showed the highest crushing strengths. Thus, SCB could be an alternative source of cellulose and MCC for pharmaceutical applications.

Photoluminescence of Fully Inorganic Colloidal Gold Nanocluster and Their Manipulation Using Surface Charge Effects.

Fully inorganic, colloidal gold nanoclusters (NCs) constitute a new class of nanomaterials that are clearly distinguishable from their commonly studied metal-organic ligand-capped counterparts. As their synthesis by chemical methods is challenging, details about their optical properties remain widely unknown. In this work, laser fragmentation in liquids is performed to produce fully inorganic and size-controlled colloidal gold NCs with monomodal particle size distributions and an fcc-like structure. Results reveal that these NCs exhibit highly pronounced photoluminescence with quantum yields of 2%. The emission behavior of small (2-2.5nm) and ultrasmall (<1nm) NCs is significantly different and dominated by either core- or surface-based emission states. It is further verified that emission intensities are a function of the surface charge density, which is easily controllable by the pH of the surrounding medium. This experimentally observed correlation between surface charge and photoluminescence emission intensity is confirmed by density functional theoretical simulations, demonstrating that fully inorganic NCs provide an appropriate material to bridge the gap between experimental and computational studies of NCs. The presented study deepens the understanding of electronic structures in fully inorganic colloidal gold NCs and how to systematically tune their optical properties via surface charge density and particle size.