Characterization Of Colloids Research Articles

Design and Engineering of "Green" Nanoemulsions for Enhanced Topical Delivery of Bakuchiol Achieved in a Sustainable Manner: A Novel Eco-Friendly Approach to Bioretinol.

In the present work, we establish novel “environmentally-friendly” oil-in-water nanoemulsions to enhance the transdermal delivery of bakuchiol, the so-called “bioretinol” obtained from powdered Psoralea corylifolia seeds via a sustainable process, i.e., using a supercritical fluid extraction approach with pure carbon dioxide (SC-CO2). According to Green Chemistry principles, five novel formulations were stabilized by “green” hybrid ionic surfactants such as coco-betaine—surfactin molecules obtained from coconut and fermented rapeseed meal. Preliminary optimization studies involving three dispersion stability tests, i.e., centrifugation, heating, and cooling cycles, indicated the most promising candidates for further physicochemical analysis. Finally, nanoemulsion colloidal characterization provided by scattering (dynamic and electrophoretic light scattering as well as backscattering), microscopic (transmission electron and confocal laser scanning microscopy), and spectroscopic (UV–Vis spectroscopy) methods revealed the most stable nanocarrier for transdermal biological investigation. In vitro, topical experiments provided on human skin cell line HaCaT keratinocytes and normal dermal NHDF fibroblasts indicated high cell viability upon treatment of the tested formulation with a final 0.02–0.2 mg/mL bakuchiol concentration. This excellent biocompatibility was confirmed by ex vivo and in vivo tests on animal and human skin tissue. The improved permeability and antiaging potential of the bakuchiol-encapsulated rich extract were observed, indicating that the obtained ecological nanoemulsions are competitive with commercial retinol formulations.

Interparticle Forces of a Native and Encapsulated Metal-Organic Framework and Their Effects on Colloidal Dispersion.

The colloidal properties of suspended metal-organic frameworks (MOFs) are critical for device fabrication and application. Herein, van der Waals attractive, electric double layer repulsive, and steric repulsive forces of a native and encapsulated MOF are quantified for the first time. The van der Waals attractive forces were investigated by conducting environmental ellipsometric porosimetry (EEP) and spectroscopic ellipsometry (SE) on submicron, optical-quality nanoparticle films. The repulsive forces were determined from colloid and material characterization measurements. These data were used to predict suspension properties via extended Derjaguin, Landau, Verwey, and Overbeek theory. The state of dispersion was quantified for comparison with theoretical predictions for nine solvents. The MOF encapsulated with a surface-selective modification showed superior suspension in hydrophobic solvents. These findings should expedite the formulation of MOF colloidal suspensions for future works.

Terahertz Absorption Characteristics of the Sodium Carboxymethyl Cellulose Colloid Based on Microfluidic Technology

Sodium carboxymethyl cellulose is a type of macromolecular chemical substance that is widely used in the industry for food thickening. In this study, terahertz and microfluidic technologies were combined, and a microfluidic chip with a channel depth of 50 μm was fabricated to carry samples. The terahertz characteristics of the sodium carboxymethyl cellulose colloid were studied at different concentrations and applied electric fields. The obtained results showed that different concentrations of sodium carboxymethyl cellulose have different time-domain spectra; with an increase in concentration, the terahertz transmittance of sodium carboxymethyl cellulose decreased. Under the applied electric field treatment, the longer the electric field acting time is, the higher the terahertz transmission intensity is. This approach is a safe and reliable new method for the determination of sodium carboxymethyl cellulose concentration, which provides technical support for the in-depth study of sodium carboxymethyl cellulose.

Colloid-mediated transport of tetracycline in saturated porous media: Comparison between ferrihydrite and montmorillonite

Given the ubiquitous mineral (e.g., clays and iron oxides) playing critical roles in impacting the fate of antibiotics in the subsurface environment, the effects of two mineral colloids (i.e., ferrihydrite and montmorillonite) on tetracycline (TC, a representative of antibiotic) transport in sand columns were investigated in this study. Interestingly, the results clearly showed that ferrihydrite colloids inhibited TC transport, while montmorillonite colloids enhanced TC mobility under neutral conditions (pH 7.0). This phenomenon resulted from the positively charged ferrihydrite colloids with weak mobility, which assisted TC deposition; besides, providing additional deposition sites for TC by the deposited ferrihydrite colloids was another important mechanism. In contrast, the transport-enhancement effect of montmorillonite on TC was attributed to the strong binding affinity of TC to clay particles as well as the competition between colloids and TC for deposition sites on sand surfaces. Moreover, the transport-inhibition effect of ferrihydrite at pH 7.0 was greater than that at pH 5.0, mainly due to more colloid-associated TC under neutral conditions. Surprisingly, ferrihydrite colloids could act as carriers of antibiotics and enhanced TC transport at pH 9.0. Because the surface charge of colloids was altered to negative and could break through the column. Meanwhile, the transport-enhancement effect of montmorillonite decreased with increasing pH from 5.0 to 9.0, resulting from the decrease of colloid-adsorbed TC. Furthermore, colloid-mediated transport of TC was influenced by ionic strength, which affected the aggregation characteristics of colloids and the binding affinities of TC to minerals. These findings provide critical information for assessing the risks of antibiotics in aquatic ecosystems where abundant natural minerals are present.

Structure-Based Optimization of Quinazolines as Cruzain and TbrCATL Inhibitors.

The cysteine proteases, cruzain and TbrCATL (rhodesain), are therapeutic targets for Chagas disease and Human African Trypanosomiasis, respectively. Among the known inhibitors for these proteases, we have described N4-benzyl-N2-phenylquinazoline-2,4-diamine (compound 7 in the original publication, 1a in this study), as a competitive cruzain inhibitor (Ki = 1.4 μM). Here, we describe the synthesis and biological evaluation of 22 analogs of 1a, containing modifications in the quinazoline core, and in the substituents in positions 2 and 4 of this ring. The analogs demonstrate low micromolar inhibition of the target proteases and cidal activity against Trypanosoma cruzi with up to two log selectivity indices in counterscreens with myoblasts. Fourteen compounds were active against Trypanosoma brucei at low to mid micromolar concentrations. During the optimization of 1a, structure-based design and prediction of physicochemical properties were employed to maintain potency against the enzymes while removing colloidal aggregator characteristics observed for some molecules in this series.

Reproducibility and Scalability of Magnetic Nanoheater Synthesis.

The application of magnetic nanoparticles requires large amounts of materials of reproducible quality. This work explores the scaled-up synthesis of multi-core iron oxide nanoparticles through the use of thermal decomposition in organic media and kilograms of reagents. To this end, we check the effect of extending the high temperature step from minutes to hours. To address the intrinsic variability of the colloidal crystallization nucleation process, the experiments were repeated and analyzed statistically. Due to the simultaneity of the nuclei growth and agglomeration steps, the nanostructure of the samples produced was a combination of single- and multi-core nanoparticles. The main characteristics of the materials obtained, as well as the reaction yields, were analyzed and compared. As a general rule, yield, particle size, and reproducibility increase when the time at high temperature is prolonged. The samples obtained were ranked in terms of the reproducibility of different structural, colloidal, and magnetic features. The capability of the obtained materials to act as nanoheaters in magnetic hyperthermia was assessed, showing a strong dependence on the crystallite size (calculated by X-ray diffraction), reflecting the nanoparticle volume with a coherent magnetization reversal.

Reductive Methylation of Homogeneous Primary β-Lauryl/myristyl 7/3 Polyethyleneoxy n = 3-18 Ethylamines under Phase-Transfer Catalysis Conditions.

Homogeneous tertiary N,N-dimethyl-N-β-lauryl/myristyl 7/3 polyethyleneoxy n = 3–18 ethylamines, LM(EO)nAT, are niche intermediates in the synthesis of homogeneous N-alkyl (C1–C18)-N,N-dimethyl-N-β-lauryl/myristyl 7/3 polyethyleneoxy n = 3–18 ethylammonium chlorides (unitary degree of oligomerization of ethylene oxide in the polyoxyethylene chain). This paper synthetically presents the dependence of the reductive methylation yields of homogeneous primary β-lauryl/myristyl 7/3 polyethyleneoxy n = 3–18 ethylamines, LM(EO)nAP, on the reaction time (10–90 min), the temperature (70 °C), the molar ratio formic aldehyde /LM(EO)nAP (1.1/1–2.5/1), the molar ratio HCOOH/LM(EO)nAP (5/1), the degree of oligomerization of ethylene oxide in the homogeneous polyoxyethylene chain in the 3,6,9,12,18 series, and the structure of the phase-transfer catalysts. The steric effects of hydrophobic groups CH3 and C18H37 grafted onto the ammonium function, and the micellar phenomena in the vicinity of their critical micellar concentration, directly proportional to the homogeneous degree of oligomerization, were highlighted. In all cases, a steady increase in reductive methylation yields was observed, with even quantitative values obtained. The high purity of the homologous series LM(EO)nAT will allow their personalization as reference structures for the study of the evolution of basic colloidal characteristics useful in forecasting technological applications. LM(EO)nAP were obtained either by direct amidoethylation (nucleophilic addition under basic catalysis of homogeneous lauryl/myristyl 7/3 polyethoxylated n = 3, 6, 9, 12, 18 alcohols, LM(EO)nOH, to acrylamide monomer) or by cyanoethylation of LM(EO)nOH under basic catalysis at 25–50 °C, in the presence of Fe2+ cations as oligomerization/polymerization inhibitor, followed by partial acid hydrolysis of homogeneous β-alkyl (C12H25/C14H29) 7/3 polyethyleneoxy n = 3, 6, 9, 12, 18 propionitriles, LM(EO)nPN, to β-alkyl (C12H25/C14H29) 7/3 polyethyleneoxy n = 3, 6, 9, 12, 18 propionamides, LM(EO)nPD, which led to LM(EO)nAP by Hoffmann degradation. Homogeneous higher tertiary polyetheramines LM(EO)nAT were structurally characterized.

Field-scale investigation of nanoscale zero-valent iron (NZVI) injection parameters for enhanced delivery of NZVI particles to groundwater

The effects of the injection parameters on delivery of nanoscale zero-valent iron (NZVI) to contaminated groundwater were investigated. The first two NZVI injections (gravity injection at low flow rates) resulted in NZVI being poorly mobile and gave total cumulative mass recoveries at the monitoring wells of 1.07%–2.43%. NZVI reached some wells (KDMW-3, MW-2, MW-4, and MW-7) earlier than the bromide tracer. The dominant travel directions for NZVI and the bromide tracer were very different. The NZVI transport characteristics suggested that targeted NZVI delivery requires preferential groundwater flow paths and local heterogeneity to be considered. In the gravity injection tests, the maximum NZVI concentrations and cumulative NZVI mass recoveries in the wells decreased markedly as the injected NZVI concentration and dose increased. In the third and fourth tests, in which NZVI was injected under pressure at high flow rates, NZVI was effectively delivered to the wells despite the injected NZVI concentration and dose being high. Relatively high cumulative mass recoveries of 26.0% and 74.5% were found for the third and fourth injections, respectively. Controlling the flow rate (pressure) and NZVI concentration and dose simply and effectively controlled NZVI mobility in the groundwater. The colloidal and electrostatic characteristics of the NZVI particles were monitored and modeled, and the results indicated that NZVI particles without Derjaguin–Landau–Verwey–Overbeek energy barriers were successfully delivered to the target zone and that decreased magnetic attractive forces between NZVI particles caused by iron corrosion probably decreased the degree of NZVI particle aggregation and therefore contributed to NZVI being delivered to the target zone.

Fully photodegradable block copolymer nanoparticles for dual release of cargo and radicals

When exposed to radiation, photo-responsive block copolymer nanoparticles disassemble to liberate a possible carried guest. However, the particle disruption is rarely accompanied by a polymer chain disintegration into molecular fragments, that would facilitate clearance from the body. We describe herein a novel class of fully photodegradable all-acrylic poly(hydroxyethyl acrylate)-b-poly(o-nitrobenzyl acrylate) (PHEA-PNBA) nanoparticles. Their synthesis proceeds by dispersion polymerization-induced self-assembly (PISA) based on a reversible addition–fragmentation chain transfer mechanism. The self-immolation mechanism is initiated via a dual H-abstraction by the electronically excited o-nitrobenzyl pendant group, first, from the adjacent CH2, second, from CH of the polyacrylate chains. The former results in the release of the protecting group, while the latter initiates a cascade of reactions that fragment the whole polymer backbone. Simultaneous chain scission and cleavage of o-nitrobenzyl group combine in turn to induce a fast and complete degradation of the copolymer particles. Synthesis, structural and colloidal characterization of the diblock copolymer nanoparticles, photochemical mechanism governing self-immolation are described. Emphasis is placed on understanding the reaction parameters which are important in controlling degradation rates, in particular nature of continuous phase and degree of polymerization of the PNBA block. UV exposure is exploited to release a model guest (Nile red) from the particles. Additionally, the burst release of free radicals accompanying the chain degradation can serve to decompose a target molecule (methylene blue).

Effect of extraction methods on mobilizable colloids and associated phosphorus from reservoir sediment

Mobilizable colloids from reservoir sediment contain nutrients and contaminants, thus may affect water quality once being released. A major obstacle to evaluate the quantity and quality of mobilizable colloids in natural system is the using of appropriate method for colloid extraction from sediment and their separation from dissolved and particulate phases. This work evaluates the role of different extraction methods (agitation, sonication at sediment pH, and sonication at alkaline pH) on the characteristics (mass, size, shape and composition) of water-mobilizable colloids from sediment of Champsanglard dam reservoir (France). Attention has been paid to phosphorus (P), an important element in controlling eutrophication. Recovered colloids were highly affected on both quantity and quality according to the different applied protocols. The less aggressive agitation liberated low-energy water-dispersible colloids without physical damage and with less modification in colloidal chemical composition and shape, whereas sonication released 10–20 times higher colloid quantity but in lower size, due to physically disruption of fragile sediment structure or aggregated/chained colloids. In contrast, alkaline pH intensified colloid release by fortified repulsive forces between colloids and dissolution of organic coat. Concerning phosphorus, competition with hydroxide ions for sorption site or dissolution of phosphate minerals in alkaline pH caused release of dissolved P to solution and decrease of P content in recovered colloids. A special care should be paid to method selection according to the aim of the study and when comparing data from experiments conducted with different colloid extraction methods.

Colloidal Analysis of Particles Extracted from Microalloyed Steels

AbstractDifferent colloidal particle characterization methods are examined for their suitability to determine the particle size distribution of particles extracted from steels. Microalloyed steels are dissolved to extract niobium and titanium carbonitride particles that are important for the mechanical properties of these steels. Such particles have sizes ranging from several nanometers to hundreds of nanometers depending on the precipitation stage during the thermomechanically controlled rolling process. The size distribution of the particles is analyzed by dynamic light scattering (DLS), analytical ultracentrifugation (AUC), and hollow fiber flow field‐flow fractionation (HF5) and compared to data obtained for reference particles as well as data from electron microscopy, the standard sizing technique used in metallurgy today. AUC and HF5 provide high‐quality size distributions, average over large particle numbers that enables statistical analysis, and yield useful insights for alloy design; however, DLS fails due to a lack of resolution. Important aspects in the conversion and comparison of size distributions obtained for broadly distributed particle systems with different measurement principles and the role of surfactants used in sample preparation are discussed.

Role of nonspherical DLVO and capillary forces in the transport of 2D delaminated Ti3C2Tx MXene in saturated and unsaturated porous media

The transport and retention of two-dimensional (2D) nanomaterials, such as graphene oxide, in porous media have attracted lots of attention. However, previous studies often simplified these 2D colloids as equivalent spheres for numerical simulations, which ignored the influence of particle shape on colloid retention at multiple interfaces. In this study, a novel 2D nanomaterial delaminated Ti3C2Tx (d-Ti3C2Tx) was adopted to fill this knowledge gap. Comprehensive analyses of the 2D colloid retention mechanisms were conducted based on colloid characterization, saturated and unsaturated column experiments, reactive transport modeling, 2D-based DLVO and nonspherical capillary energy simulations. Results show that d-Ti3C2Tx mobility in both saturated and unsaturated conditions enhanced with the increase in pH and decrease in ionic strength. The DLVO interaction energy of d-Ti3C2Tx at the sand-water-interface (SWI) decreased with the orientation angle of the colloidal major axis to the sand surface from 0° to 90°. The primary mechanism under saturated flow conditions was the irreversible attachment in the deep secondary minimum at the SWI with the major axis of d-Ti3C2Tx parallel to the sand surface. The attachment in the primary minimum at 0° was impossible due to the extremely high energy barrier, and the attachment in the primary and secondary minimum at other orientation angles were negligible. d-Ti3C2Tx only experienced repulsive electrostatic force when approaching the air-water-interface (AWI) no matter the particle orientation. The detaching capillary potential energy was 3 orders of magnitude larger than the attractive DLVO interaction energy of the SWI in the secondary minimum at 0°, suggesting that the capillary force-induced irreversible attachment at the AWI was the primary mechanism under unsaturated flow conditions. This study shows that the DLVO and capillary potential energies were significantly dependent on the particle-interface orientation and colloidal shape. A simplification of 2D colloids as spheres is not recommended.

Colloidal processing and characterization of TiO2–MnO‐doped alumina/alumina slurries and tapes

AbstractAqueous slurries of alumina doped with manganese and titanium oxides were developed. The powders and tapes were investigated by scanning electron (SEM) microscopy, X‐ray diffractometry (XRD), and thermal analyses (TG/DSC). The stability and rheology of colloidal suspensions of undoped and doped alumina suspensions were investigated. At neutral pH of 7, pure alumina and MnO–TiO2 dopant particles present positive and negative surface charges and are prone to heterocoagulation. Optimized colloidal processing through proper adjustment of parameters was achieved to reach particle stabilization. The surface charge of the oxide particles was negative, and the suspensions did not agglomerate at a pH of 7 and higher. Tapes were cast, dried, and burned out. The thermal analyses revealed the release of residual water and decomposition of short‐chain organics at temperatures under 215°C and of long‐chain additives over 300°C.

Oleic Acid Vesicles as a new Approach for Transdermal Delivery of Econazole Nitrate: Development, Characterization, and In-vivo Evaluation in Wistar rats.

Cutaneous candidiasis is a deep-seated skin fungal infection that is most commonly observed in immunocompromised patients. This fungal infection is conventionally treated with various formulations like gels and creams which are having different side effects and least therapeutic efficacy. Hence, it becomes necessary to develop a novel carrier system for the treatment of this deep-seated skin fungal infection. Econazole nitrate is the most widely used antifungal for the treatment of cutaneous candidiasis, therefore, in present research work we developed and evaluated econazole nitrate loaded oleic acid vesicles for treatment of cutaneous candidiasis through transdermal route. Econazole nitrate loaded oleic acid vesicles were prepared by thin-film hydration and characterized for drug entrapment, vesicle size, zeta potential, polydispersity index (PDI), Fourier Transform-infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), X-ray diffraction (XRD) analysis. Furthermore, the oleic acid vesicular gel was evaluated for ex-vivo skin permeation/retention and in-vitro and in-vivo antifungal activity in Wistar rats. Econazole nitrate loaded oleic acid vesicles showed high encapsulation of drug (74.76 ± 3.0%), acceptable size (373.4 ± 2.9 nm), and colloidal characteristics (PDI = 0.231 ± 0.078, zeta potential = -13.27 ± 0.80 mV). The oleic acid vesicular gel showed high skin permeation (Transdermal flux = 61.98 ± 2.45 μg/cm2/h), skin retention (35.90 ± 2.06%), in-vitro, and in-vivo antifungal activity compared to marketed cream (EcodermR) of econazole nitrate for a prolonged period of time (4 days). Developed econazole nitrate loaded oleic acid vesicles could be used effectively in the treatment of cutaneous candidiasis with minimization of side effects of econazole nitrate with increased therapeutic efficacy.

Microfabric characteristics of kaolinite flocculates and aggregates — Insights from large-scale molecular dynamics simulations

Clay particles are usually associated in flocculates or aggregates with different microfabric manners, which will govern the macroscale mechanical behaviors of clayey soils. In this study, the characteristics of different microfabric manners of defect-free kaolinite were explored applying large-scale full-atomistic molecular dynamics simulations. Due to the special crystal structure, kaolinite particles were more likely to flocculate in Edge-to-Face (EF) and Edge-to-Edge (EE) manners than aggregate in Face-to-Face (FF) manner when analyzed from the system energy point of view. For EF and EE manners, the 1st layer of adsorbed water of every single kaolinite particle was complete while the 2nd and the 3rd layers of adsorbed water arranged in T-, L-/inverted L- or cross-shape according to the wettability performance of surrounding kaolinite particles' surfaces. A series of new schematic diagrams of different microfabric manners with adsorbed water structures were developed according to the corresponding equilibrium topologies and physicochemical characteristics. The conceptual hypothesis of the kaolinite sedimentary process was verified and improved based on the simulation results analysis. The research results enhanced the comprehension of microfabric characteristics of clay colloids. The simulation method applied in this work would foster future investigations into clay colloids in various physicochemical environments.

The concentration and size distribution of iron‐rich colloids in pore waters are related to soil organic matter content and pore water calcium concentration

AbstractIron (Fe)‐rich colloids in the environment have a high surface reactivity and facilitate transport of oxyanions and trace metal cations in soil. This study was set up to help identify the soil properties that might affect the concentrations of colloidal Fe and its size distribution in pore waters of soils. The pore water was isolated by centrifugation from a collection of 97 topsoils with contrasting properties and land use. The total Fe concentration in the pore waters ranged between 0.2 and 26 μM (10th–90th percentile) and was largest at low soil solution calcium (Ca) and high dissolved organic carbon (DOC), indicating that enhanced colloidal stability determines total Fe in solution. The colloidal size distribution (<100 nm) of Fe in the pore waters of 11 soils was determined with flow field flow fractionation (FlFFF‐UV‐ICP‐MS), which yielded three different fractions that varied strikingly among soils. The smallest fraction (<5 nm) of Fe co‐eluted with high DOC and copper (Cu), suggesting mononuclear Fe‐organic carbon (OC) complexes. This fraction increased with an increasing DOC/Fe ratio in pore waters. The 5–50‐nm fraction of Fe prevailed in soils with >3.5% organic carbon (%OC), whereas the 50–100‐nm fraction was dominant in soils with low %OC content. This suggests that natural organic matter inhibits crystallization and growth of mineral Fe particles. The elemental ratios of mineral colloids (>5 nm) indicated the presence of clay minerals and Fe oxyhydroxides, which was confirmed by scanning electron microscopy (SEM) analysis. This study thus identified soil %OC and Ca in soil solution as the dominant factors predicting both the concentration and size of pore water Fe colloids, with the smallest and, potentially, most mobile Fe colloids occurring in OC‐rich soils.Highlights Pore water iron concentrations in topsoils are governed by colloid stability Flow field flow fractionation analysis allows characterization of iron colloids in the low nanometre range Iron colloid size and composition vary strikingly among soils Small iron colloids prevail in organic carbon‐rich soils due to colloid growth inhibition

Co-transport of ball‐milled biochar and Cd2+ in saturated porous media

The combination of ball milling technology and biochar materials provides new prospects for environmentally friendly and sustainable environmental pollution control technologies, but comes with opportunities and risks. In this study, column experiments were used to evaluate the environmental behavior of ball‑milled biochar (BMBC). The results of the column experiments showed that BMBC transport increased with a high flow velocity, large medium size, high pH, and low ionic strength. Owing to the strong adsorption of Cd2+ by BMBC, the presence of BMBC in the medium led to a decrease in effluent Cd2+. The presence of Cd2+ in the solution slightly inhibited the transport of BMBC. The transport of Cd2+ was facilitated by BMBC due to the high affinity. Therefore, attention should be paid to favorable conditions for BMBC transport. This study provides a perspective to assess the behavior of BMBC in the environment and whether its interaction with Cd2+ will introduce new environmental hazards.

Colloidal Nanostructures of Transition-Metal Dichalcogenides.

ConspectusLayered transition-metal dichalcogenides (TMDs) are intriguing two-dimensional (2D) compounds where metal and chalcogen atoms are covalently bonded in each monolayer, and the monolayers are held together by weak van der Waals forces. Distinct from graphene, which is chemically inert, layered TMDs exhibit a wide range of electronic, optical, catalytic, and magnetic properties dependent upon their compositions, crystal structures, and thicknesses, which make them fundamentally and technologically important. TMD nanostructures are traditionally synthesized using gas-phase chemical deposition methods, which are typically limited to small-scale samples of substrate-bound planar materials. Colloidal synthesis has emerged as an alternative synthesis approach to enable the scalable synthesis of free-standing TMDs. The judicious selection of precursors, solvents, and capping ligands together with the optimization of synthesis parameters such as concentrations and temperatures leads to the fabrication of colloidal TMD nanostructures exhibiting tunable properties. In addition, understanding the formation and transformation of TMD nanostructures in solution contributes to the discovery of important structure-function relationships, which may be extendable to other anisotropic systems.In this Account, we summarize recent progress in the colloidal synthesis, characterization, and applications of TMD nanostructures with tunable compositions, structures, and thicknesses. On the basis of the preparation of Mo- and W-based disulfide, diselenide, and ditelluride nanostructures, we discuss examples of phase engineering where various metastable TMD compounds can be directly accessed at low temperatures in solution. We also analyze the chemistry involved in broadly tuning the composition across the MoSe2-WSe2, WS2-WSe2, and MoTe2-WTe2 solid solutions as well as atomic-level microscopic characterization and the resulting composition-tunable properties. We then highlight how the high densities of defects in the colloidally synthesized TMD nanostructures enable unique catalytic properties, including their ability to facilitate the selective hydrogenation of substituted nitroarenes using molecular hydrogen. Finally, using this library of colloidal TMD nanostructures as substrates, we discuss the pathways by which noble metals deposit onto them in solution. We highlight the importance of the relative strengths of the interfacial metal-chalcogen bonds in determining the sizes and morphologies of the deposited noble metal components. These synthesis capabilities for colloidal TMD nanostructures, which have been generalized to a library of composition-tunable phases, enable new systematic studies of structure-property relationships and chemical reactivity in this important class of 2D materials.

Superficial Characteristics and Functionalization Effectiveness of Non-Toxic Glutathione-Capped Magnetic, Fluorescent, Metallic and Hybrid Nanoparticles for Biomedical Applications

An optimal design of nanoparticles suitable for biomedical applications requires proper functionalization, a key step in the synthesis of such nanoparticles, not only for subsequent crosslinking to biological targets and to avoid cytotoxicity, but also to endow these materials with colloidal stability. In this sense, a reliable characterization of the effectiveness of the functionalization process would, therefore, be crucial for subsequent bioconjugations. In this work, we have analyzed glutathione as a means to functionalize four of the most widely used nanoparticles in biomedicine, one of which is a hybrid gold-magnetic-iron-oxide nanoparticle synthetized by a simple and novel method that we propose in this article. We have analyzed the colloidal characteristics that the glutathione capping provides to the different nanoparticles and, using information on the Z-potential, we have deduced the chemical group used by glutathione to link to the nanoparticle core. We have used electron microscopy for further structural and chemical characterization of the nanoparticles. Finally, we have evaluated nanoparticle cytotoxicity, studying cell viability after incubation with different concentrations of nanoparticles, showing their suitability for biomedical applications.

Enhanced efficacy against bacterial biofilms via host:guest cyclodextrin‐doxycycline inclusion complexes

Periodontal disease is characterized by a microbial infection and it is one of the major causes of teeth loss. The growth of pathogenic bacteria in oral cavity, such as Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans), provides a favorable enviromment for the biofilm formation, which result in periodontal diseases. The development of new technologies to potentiate existing drugs, avoiding bacterial biofilms resistance and improving chemical stability is highly desirable. Here, we report the use of host–guest chemistry to enhance the activity of antibacterial doxycycline (DOX) in A. actinomycetemcomitans bacterial strain suspension and biofilm in vitro through complexation with hydroxypropyl-β-cyclodextrin (HPβCD) using different molar ratios of DOX/HPβCD. 2D 1H NMR confirmed the host–guest complexation of DOX and HPβCD. We assessed the colloidal characteristics of the complex DOX/HPβCD via Dynamic Light Scattering (DLS) and Zeta Potential (PZ). The mixing ratio 1:2 DOX/HPβCD significantly decreased the minimum inhibitory concentration (MIC) and improved efficacy against A. actinomycetemcomitans suspensions and biofilms, respectively, when compared to free DOX and other DOX/HPβCD complexes. Further, the interaction of different molar ratio proportions of DOX/HPβCD complex with bacterial membrane was demonstrated via Isothermal Titration Calorimetry (ITC). Thus, we suggested the enhanced efficacy of the DOX/HPβCD complexes, at molar ratio 1:2, is due the higher cyclodextrin ratio, which potentiate the interaction between drug and bacterial membrane through nonionic interactions, such as hydrogen bonding or other van der Waals interactions. Collectively, the development of these complexes enables increased efficacy against bacterial biofilms, which hold promise for the treatment of aggressive and non-responsive forms of periodontitis.