Nanoparticles In Aqueous Media Research Articles

Supra-Fluorophores: Ultrabright Fluorescent Supramolecular Assemblies Derived from Conventional Fluorophores in Water.

Fluorescent organic nanoparticles (NPs) with exceptional brightness hold significant promise for demanding fluorescence bioimaging applications. Although considerable efforts are invested in developing novel organic dyes with enhanced performance, augmenting the brightness of conventional fluorophores is still one of the biggest challenges to overcome. This study presents a supramolecular strategy for constructing ultrabright fluorescent nanoparticles in aqueous media (referred to as "Supra-fluorophores") derived from conventional fluorophores. To achieve this, this course has employed a cylindrical nanoparticle with a hydrophobic microdomain, assembled by a cyclic peptide-diblock copolymer conjugate in water, as a supramolecular scaffold. The noncovalent dispersion of fluorophore moieties within the hydrophobic microdomain of the scaffold effectively mitigates the undesired aggregation-caused quenching and fluorescence quenching by water, resulting in fluorescent NPs with high brightness. This strategy is applicable to a broad spectrum of fluorophore families, covering polyaromatic hydrocarbons, coumarins, boron-dipyrromethenes, cyanines, xanthenes, and squaraines. The resulting fluorescent NPs demonstrate high fluorescence quantum yield (>30%) and brightness per volume (as high as 12060 m-1 cm-1 nm-3). Moreover, high-performance NPs with emission in the NIR region are constructed, showcasing up to 20-fold increase in both brightness and photostability. This Supra-fluorophore strategy offers a versatile and effective method for transforming existing fluorophores into ultrabright fluorescent NPs in aqueous environments, for applications such as bioimaging.

Sonochemical Analysis of Methylene Blue with Additives and ZnO Nanoparticles in Aqueous Medium

The use of ultrasound was found to be a very suitable and effective method for the degradation of hazardous dyestuffs. The degradation of dye molecules in aqueous media in the presence of various additives by ultrasonic irradiation was investigated in order to clarify the degradation mechanism. In this investigation, Methylene Blue (MB) has been used as a representative of azo dye and inorganic salts like NaCl and Na2SO4 were used as additives. Besides degradation in presence of CCl4 and H2O2 solutions were observed. ZnO nanoparticle was also used for the investigation of degradation. The volume of all solutions was 100ml containing 25mg/L of MB. The sonication of dye molecules were conducted for 0, 5, 15, 25 minutes. The degradation mechanism was discussed in details adopting UV- visible spectra. From the experiments it is clear that the acidic condition is favorable for dye degradation. Evaluating the results we have also found that all additives aided the degradation comparatively higher or lower the extent depending on their used amount in solution. So, it is a clear indication that azo dyes from waste water can be efficiently removed by using sonochemical irradiation method under acidic condition

Size and phase preservation of amorphous calcium carbonate nanoparticles in aqueous media using different types of lignin for contrast-enhanced ultrasound imaging

Hypothesis: Calcium carbonate (CaCO3) nanoparticles could have great potential for contrast-enhanced ultrasound imaging (CEUS) due to their gas-generating properties and sensitivity to physiological conditions. However, the use of nano CaCO3 for biomedical applications requires the assistance of stabilizers to control the size and avoid the fast dissolution/recrystallization of the particles when exposed to aqueous conditions.Experiments: Herein, we report the stabilization of nano CaCO3 using lignin, and synthesized core–shell amorphous CaCO3-lignin nanoparticles (LigCC NPs) with a diameter below 100 nm. We have then investigated the echogenicity of the LigCC NPs by monitoring the consequent generation of contrast in vitro for 90 min in linear and non-linear B-mode imaging.Findings: This research explores how lignin type and structure affect stabilization efficiency, lignin structuration around CaCO3 cores, and particle echogenicity. Interestingly, by employing lignin as the stabilizer, it becomes possible to maintain the echogenic properties of CaCO3, whereas the use of lipid coatings prevents the production of signal generation in ultrasound imaging. This work opens new avenue for CEUS imaging of the vascular and extravascular space using CaCO3, as it highlights the potential to generate contrast for extended durations at physiological pH by utilizing the amorphous phase of CaCO3.

Fluorene and Tetraphenylsilane Based Conjugated Microporous Polymer Nanoparticles for Highly Efficient Nitroaromatics Detection in Aqueous Media

AbstractConjugated microporous polymers (CMPs) are considered promising sensing materials for the detection of nitroaromatics. Unfortunately, the photoluminescence (PL) sensing application in water media is limited, owing to the poor solubility/dispersion in aqueous media. Here, two novel CMPs named poly(dimethylfluorene‐co‐tetrakis(4‐phenyl)silane)s (P4SiF) and poly(dimethylfluorene‐co‐tetrakis(3‐phenyl)silane)s (P3SiF) nanoparticles based on fluorene group and tetraphenylsilane unit are prepared using Suzuki coupling in water/toluene miniemulsion. P4SiF and P3SiF possess spherical particle morphology with sizes of 45 and 60 nm, respectively, and porous structure with pore diameters of both 1.9 nm. PL sensing experiments based on P4SiF and P3SiF nanoparticles in aqueous media show a sensitive and selective detection toward 2,4,6‐trinitrophenol (TNP). It is worth noting that the PL quenching effect toward TNP is not significantly changed after the addition of other nitro compounds, proving the excellent anti‐interference characteristic and highly selective detection of the polymers in water. Moreover, the t‐test indicates that the PL sensing method using P4SiF and P3SiF nanoparticles as sensing materials realizes the reliable detection of TNP in actual water samples at a 95% confidence level. Finally, the PL sensing mechanism is investigated, showing that the inner filter effect is the main factor in the PL quenching process of TNP in aqueous media.

Geocolloidal interactions and relaxation dynamics under nanoconfinement: Effects of salinity and particle concentration

HypothesisEnergy-related contaminants are frequently associated with geocolloids that translocate in underground fissures with dimensions comparable with geocolloids. To assess the transport and impact of energy-related contaminants in geological systems, fundamental understandings of interfacial behaviors of nanoparticles under confinement is imperative. We hypothesize that the dynamic properties of geocolloids, as well as their dependence on aqueous medium conditions would deviate from bulk behaviors under nanoconfinement. ExperimentsForce profiles and rheological properties of 50 nm silica nanoparticles in aqueous media confined between mica surfaces as a function of surface separation, particle concentrations, and salinity were measured utilizing the surface forces apparatus. FindingsForce profiles revealed the critical surface separation for nonlinear rheological behaviors coincides with the onset of exponential repulsion between mica surfaces. When salts were absent, the normal forces and viscosity values of colloidal suspensions resembled pure water. In contrast, with salts, the force profiles and corresponding critical length scales were found to be highly sensitive to the particle concentration and the degree of confinement. A Newtonian to shear-thinning transition was captured with increasing degrees of confinement. Our results show that the interplay among confinement, particle, and ionic concentrations can alter the interparticle forces and rheological responses of true nanosized-colloidal suspensions and thus their transport behaviors under nanoconfinement for the first time.

Ag nanoparticles green-mediated by Scrophularia striata aqueous extract induce apoptosis via P53 and signal transducer and activator of transcription 3 signaling pathways in gastric cancer cells

In the present study, we tried to prepare and formulate an anticancer drug (Silver nanoparticles in aqueous medium using Scrophularia striata leaf extract) for the treatment of gastric cancer. The chemical characterization tests including UV–Visible Spectroscopy (UV-Vis), Fourier Transformed Infrared Spectroscopy (FT‐IR), and Field Emission Scanning Electron Microscopy (FE‐SEM) were used for the characterization of silver nanoparticles. In the FE-SEM images, the silver nanoparticles were in an average size of 36.19 nm with the spherical shape. For investigating the antioxidant properties of AgNO3, S. striata aqueous extract, and AgNPs, the DPPH test was used in the presence of butylated hydroxytoluene (BHT) as the positive control. IC50 of silver nanoparticles was 97 µg/mL against the DPPH molecules. To survey the cytotoxicity and anticancer effects of AgNO3, S. striata aqueous extract, and AgNPs, MTT assay was used on the gastric cancer cell lines. Silver nanoparticles removed GC1415, NCI-N87 and MKN45 cancer cell lines at the low concentrations. Nanoparticles induced cell apoptosis, accompanied by the upregulation of pro-apoptotic markers (Bax and cleaved caspase-8) and downregulation of the anti-apoptotic marker, Bcl-2. Moreover, AgNPs inhibited colony formation compared to their matched control. More significantly, the molecular pathway analysis of AgNPs-treated cells revealed that nanoparticles enhance p53 expression, while inhibiting the expression of total and phosphorylated Signal Transducer and Activator Of Transcription 3 (STAT3) in cell lines, suggesting p53 and STAT3 are the main key players behind the biological events provoked by the nanoparticles in human cancer cells. As mentioned, AgNPs had significant anticancer properties against the above cell lines.

Enhanced antibacterial properties and magnetic removal of Fe3O4/fenugreek seed gum/silver nanocomposites for water treatment

This study reports the synthesis, characterization, and antibacterial activity of a novel Fe3O4 nanocomposite coated with fenugreek seed gums and silver nanoparticles (AgNPs). To enhance the antibacterial properties of AgNPs and overcome the limitations of conventional methods for the production of three-component nanocomposites, a layer of natural polymer was used. Fenugreek seed gums (FSG) were used to coat Fe3O4 NPs to prevent their decomposition and to facilitate the release of silver nanoparticles in aqueous media. The Fe3O4/FSG/Ag nanocomposites were characterized and then the antibacterial activity of the nanocomposites was evaluated against two gram-negative and two gram-positive bacteria and compared with Fe3O4, Fe3O4/FSG, FSG, and AgNO3. The results showed that the Fe3O4/FSG/Ag nanocomposites had higher antibacterial activity than the other samples and could be easily removed from treated water by a powerful magnet without causing pollution in the environment. Overall, these findings suggest that the Fe3O4/FSG/Ag nanocomposites have potential applications in water treatment for their improved antibacterial properties and ease of removal.

Novel Size-Tunable and Straightforward Ultra-Small Nanoparticle Synthesis in a Varying Concentration Range of Glycerol as a Green Reducing Solvent.

Despite all the possibilities available so far for the synthesis of nanoparticles (NPs), synthesizing ultra-small (<10 nm) monodispersed particles is still demanding. Getting a particular size with a straightforward method is a trial-and-error approach. To explore this prospective, in the current study, we have introduced a protocol which offers a varying concentration range of glycerol to successfully generate the NPs of repeatable and consistent particle size in each synthesis, thus giving an alternative from lengthy tentative preparations and/or testing protocols. Since synthesizing controlled sized nanoparticles in aqueous medium is somewhat difficult as the balance of particle growth and nucleation is challenging to control, herein, we used a polyol method with glycerol both as a solvent medium as well as reducing species for silver nitrate, as an example model ion source, to execute the nanoparticle synthesis. In order to maintain the stability of the synthesized NPs, polyvinylpyrolidone (PVP) was added as a stabilizer. The synthesis, monodispersity, and stability were confirmed using techniques such as UV-vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS), and X-ray powder diffraction (XRD), while morphological analysis and ultra-small size validation were conducted using TEM, SEM, and AFM. Interestingly, in the various concentrations of glycerol solution used (10-100%), we have observed a tunable linear size range to obtain ultra-small nanoparticles (<10 nm) up to 60% glycerol, while further increasing the glycerol component increased the size approximately to ∼160 nm, providing tunable properties in this synthesis procedure. Hence, this study provides a distinct possibility to obtain ultra-small nanoparticles with a tunable size feature for further applications in numerous fields.

Dimension-Dependent Magnetic Behavior of Manganese-Cysteine Inorganic Complex Nanoparticles.

A cysteine-based complex of Mn2+ led to the formation of nanoparticles in aqueous medium under ambient conditions. The formation and evolution of the nanoparticles in the medium were followed by ultraviolet-visible light (UV-vis) spectroscopy, circular dichroism, and electron spin resonance spectroscopy that also revealed a first-order process. The magnetic properties of the nanoparticles isolated as solid powders exhibited strong crystallite and particle size dependence. At low crystallite size, as well as particle size, the complex nanoparticles showed superparamagnetic behavior similar to other magnetic inorganic nanoparticles. The magnetic nanoparticles were found to undergo a superparamagnetic to ferromagnetic transition, and then to paramagnetic transition with a gradual increase in either their crystallite size or particle size. The discovery of dimension-dependent magnetic property of inorganic complex nanoparticles may usher in a superior option for tuning the magnetic behavior of nanocrystals, depending on the component ligands and metal ions.

Laser Generation of Colloidal Nanoparticles in Liquids: Key Processes of Laser Dispersion and Main Characteristics of Nanoparticles

The processes of laser dispersion of materials for high-performance generation of colloidal nanoparticles in liquids have been considered. Various laser and material parameters affecting this process have been studied. Efficiencies and ergonomics of the generation of colloidal nanoparticles with the help of laser systems having nano-, pico-, and femtosecond pulse durations have been compared using optical and mass criteria by the example of laser ablation of a chemically inert model material (gold) in distilled water without the use of chemical stabilizers. The main characteristics of gold and silver nanoparticles obtained by ablation in water using pulsed laser radiation of different durations have been comprehensively compared. The types of colloidal interactions between nanoparticles in aqueous media have been discussed, and the contributions of structural and ion-electrostatic interactions to the long-term stability of gold and silver nanoparticle dispersions have been analyzed.

Sulfur Polymer as Emerging Advanced Materials: Synthesis and Applications

AbstractAbundant availability of inexpensive sulfur coupled with its reactivity triggered the interest of scientific community to explore the unique chemistry of sulfur for developing advanced materials. The reactivity of sulfur diradicals is used for making copolymers with cross‐linker monomer dienes through inverse vulcanization principle which is later upgraded by conducting reactions in presence of catalysts so as to achieve functionalized sulfur copolymers at lower reaction temperatures and lower time. Multi‐component reactions provide an opportunity for the direct utilization of sulfur at mild conditions. The diverse processing methodologies have further expanded the applicability of sulfur polymeric materials. The dynamicity of the S−S bonds has potential to create avenue for making self‐healing materials and usher the generation of more functionalized segmented block co‐polymers with superior properties. Interfacial condensation polymerization has successfully been implemented for the generation of sulfur nanoparticles in aqueous medium. The recent emergence of sulfur quantum dots through various approaches generated more advanced sulfur based materials in terms of expanding sulfur applications. This review provides an account on advanced materials synthesized using sulfur as raw material and their respective applications.

Intricate Reaction Pathways on CH3NH3PbI3 Photocatalysts in Aqueous Solution Unraveled by Single-Particle Spectroscopy.

Organic-inorganic hybrid perovskites such as MAPbI3 (MA+ = CH3NH3+) have emerged as promising materials for solar cells and light-emitting devices. Despite their poor stability against moisture, perovskites work as hydrogen-producing photocatalysts or photosensitizers in perovskite-saturated aqueous solutions. However, the fundamental understanding of how chemical species or support materials in the solution affect the dynamics of the photogenerated charges in perovskites is still insufficient. In this study, we investigated the photoluminescence (PL) properties of MAPbI3 nanoparticles in aqueous media at the single-particle level. A remarkable PL blinking phenomenon, along with significant decreases in the PL intensity and lifetime compared to those in ambient air, suggested temporal fluctuations in the trapping rates of photogenerated holes by chemical species (I- and H3PO2) in the solution. Moreover, electron transfer from the excited MAPbI3 to Pt-modified TiO2 proceeds in a concerted fashion for photocatalytic hydrogen evolution under the dynamic solid-solution equilibrium condition.

Short-chain fatty acid-releasing nano-prodrugs for attenuating growth and metastasis of melanoma.

Low-molecular-weight (LMW) short-chain fatty acids (SCFAs), such as propionic and butyric acids, have been reported to possess anti-neoplastic effects; however, rapid renal clearance and high dose-based side effects limit their clinical translation. Hence, in this study, we have designed a new self-assembling nano-prodrugs that can effectively supply SCFAs: endogenous enzyme-metabolizable block copolymer poly(ethylene glycol)block-poly(vinyl ester) possessing several units of SCFAs conjugated as side chains via ester linkages. These amphiphilic polymers spontaneously self-assemble into nanostructures under aqueous conditions to form orally administrable nano-prodrugs (butyric acid: NanoBA and propionic acid: NanoPA). Herein, we show the therapeutic efficacy of SCFA nanoparticles (NanoSCFA) in a mouse model of metastasis (melanoma). Ad libitum intake of our NanoSCFA markedly demonstrated a decrease in the metastatic tumor nodules in the lungs compared with the effect observed after LMW SCFA administration with no discernible toxicity to the GI tract. In contrast, LMW SCFAs, even at a lower concentration than that of the NanoSCFA, facilitated villus atrophy. Taken together, our work suggests that the use of NanoSCFA as a therapeutic intervention for metastatic cancer is preferable over typical LMW SCFAs. STATEMENT OF SIGNIFICANCE: Low-molecular-weight (LMW) short-chain fatty acids (SCFAs) have shown versatile therapeutic effects on various diseases, including anti-tumorigenesis effects. However, their clinical translation is limited due to their poor pharmacokinetic profile and adverse effects. To overcome these limitations, we have developed new amphiphilic block copolymer-based SCFA-prodrugs, which self-assemble into nanoparticles in aqueous media (NanoSCFA). SCFAs are covalently conjugated to the hydrophobic polymer segment via ester linkage, which can be enzymatically metabolized after oral administration. In the present study, we confirmed that ad libitum intake of NanoSCFAs retarded the growth and metastatic potential of B16-F10 tumors compared to the LMW SCFAs with negligible discernible toxicity, reflecting NanoSCFA as a preferable therapeutic intervention to LMW SCFA counterparts.

Nanometer-Thick Carbon Coatings with Covalent Chemical Functionalization of Metal Oxide Nanoparticles for Environmental and Biological Applications

Metal oxide nanoparticles have many useful applications in environmental studies, as tracking agents in life sciences, and in nutrient delivery for nano-enhanced agriculture. A key challenge in controlling the behavior of metal oxide nanoparticles in aqueous media is that molecular ligands are unstable with respect to hydrolytic cleavage from the surfaces. This instability limits the practical application of metal oxide nanoparticles in aqueous media. We have developed a method for producing nanometer-thin carbon shells on the surface of Al2O3, Cr3+:Al2O3 (nanoruby), ZnO, and Fe3O4 (magnetite) metal oxides that provides a scaffold for subsequent covalent chemical functionalization. Fluorescence measurements using carbonized Cr3+:Al2O3 (nanoruby) confirm that these thin carbon coatings have relatively little impact on the optical properties, allowing bright emission with less than 50% decrease in fluorescence intensity compared to an identical nanoruby without carbon coating. We demonstrate the utility for functionalization by modifying C-coated Al2O3 with molecular ligands bearing positive and negative charges. This approach provides a pathway for functionalization of a broad range of metal oxide nanoparticles with molecular ligands that can confer specific molecular properties to the nanoparticle surfaces in aqueous media while taking advantage of the high strength and stability of C–C interfacial bonds between surface ligands and the carbon shell.

Dissolution control and stability improvement of silica nanoparticles in aqueous media

Silica nanoparticles have become an important tool in material sciences, nanomedicine, biotechnology, and pharmaceutics, with recent suggested applications also in environmental sciences. In life and environmental sciences, the application field is usually aqueous media; however, the crucial issue of silica nanoparticle dissolution behavior and rate in the target medium is often neglected, overlooked, or taken for granted. Silica nanoparticles are not stable in aqueous solutions until equilibrium silica concentrations are reached. While for life science applications, the degradability of silica nanoparticles is prerequisite for biocompatibility, this characteristic impedes the successful application of silica nanoparticles as environmental tracer, where long-term stability is needed. In this study, the impact of external (temperature, pH values, salinity, availability of silica) and internal (degree of condensation, size, porosity) parameters on the stability of ~ 45-nm-sized silica nanoparticles is characterized. Results show that external factors such as elevated temperature and alkaline pH-values accelerate the dissolution, acidic pH, high salinities, and high initial silica concentrations exhibit a contrary effect. Consequently, in applications, where external parameters cannot be controlled (e.g., in vivo, subsurface reservoirs), dissolution control and stability improvement of silica nanoparticles can be achieved by various means, such as adding a protective layer or by condensation of the silanol bonds through calcination.Graphical abstract

Nanofluid formulation based on the combined effect of silica nanoparticles and low salinity water for Enhanced Oil Recovery in sandstones

Recent studies have indicated that nanofluids that combine silica nanoparticles and low salinity water have a promising character as Enhanced Oil Recovery agents for application in sandstones. In view of that, this work aimed to investigate the stabilization mechanism of silica nanoparticles in aqueous medium and the effects that low-salinity silica nanofluids induce on fluid/fluid and rock/fluid interactions in order to generate contributions to the understanding of the oil recovery mechanisms of this potential injection fluid. Therefore, experiments were carried out with nanofluids containing silica nanoparticles at concentrations between 0.01 and 0.2 wt% dispersed both in deionized water (DW) and in a low salinity water (LSW) containing a Total Dissolved Solids of 1343.4 mg/L. The results showed that the dynamic viscosity of the nanofluids exceeds that of DW by, at most, only about 4.23%. The size of the silica nanoparticles in the nanofluids did not increase over 200 nm and was not consistently affected by factors such as nanoparticle concentration, dispersing fluid or time elapsed after sonication of the nanofluids. In general, the interfacial tension between the crude oil and DW was not substantially changed when the aqueous phase was replaced by the nanofluids. On the other hand, the zeta potential of silica nanoparticles was significantly decreased when they were dispersed in LSW in comparison to DW. The contact angle analyzes evidenced the ability of the nanofluids in altering the wettability of crude-oil aged sandstone surfaces towards more water-wet conditions, notably the nanofluids with higher concentrations of silica nanoparticles and prepared with LSW.

Chemical and Colloidal Stability of Polymer-Coated NaYF4:Yb,Er Nanoparticles in Aqueous Media and Viability of Cells: The Effect of a Protective Coating.

Upconverting nanoparticles (UCNPs) are of particular interest in nanomedicine for in vivo deep-tissue optical cancer bioimaging due to their efficient cellular uptake dependent on polymer coating. In this study, particles, ca. 25 nm in diameter, were prepared by a high-temperature coprecipitation of lanthanide chlorides. To ensure optimal dispersion of UCNPs in aqueous milieu, they were coated with three different polymers containing reactive groups, i.e., poly(ethylene glycol)-alendronate (PEG-Ale), poly(N,N-dimethylacrylamide-co-2-aminoethylacrylamide)-alendronate (PDMA-Ale), and poly(methyl vinyl ether-co-maleic acid) (PMVEMA). All the particles were characterized by TEM, DLS, FTIR, and spectrofluorometer to determine the morphology, hydrodynamic size and ξ-potential, composition, and upconversion luminescence. The degradability/dissolution of UCNPs in water, PBS, DMEM, or artificial lysosomal fluid (ALF) was evaluated using an ion-selective electrochemical method and UV-Vis spectroscopy. The dissolution that was more pronounced in PBS at elevated temperatures was decelerated by polymer coatings. The dissolution in DMEM was relatively small, but much more pronounced in ALF. PMVEMA with multiple anchoring groups provided better protection against particle dissolution in PBS than PEG-Ale and PDMA-Ale polymers containing only one reactive group. However, the cytotoxicity of the particles depended not only on their ability to rapidly degrade, but also on the type of coating. According to MTT, neat UCNPs and UCNP@PMVEMA were toxic for both rat cells (C6) and rat mesenchymal stem cells (rMSCs), which was in contrast to the UCNP@Ale-PDMA particles that were biocompatible. On the other hand, both the cytotoxicity and uptake of the UCNP@Ale-PEG particles by C6 and rMSCs were low, according to MTT assay and ICP-MS, respectively. This was confirmed by a confocal microscopy, where the neat UCNPs were preferentially internalized by both cell types, followed by the UCNP@PMVEMA, UCNP@Ale-PDMA, and UCNP@Ale-PEG particles. This study provides guidance for the selection of a suitable nanoparticle coating with respect to future biomedical applications where specific behaviors (extracellular deposition vs. cell internalization) are expected.

Polymyxin B Conjugates with Bio-Inspired Synthetic Polymers of Different Nature.

The emergence and growth of bacterial resistance to antibiotics poses an enormous threat to humanity in the future. In this regard, the discovery of new antibiotics and the improvement of existing ones is a priority task. In this study, we proposed the synthesis of new polymeric conjugates of polymyxin B, which is a clinically approved but limited-use peptide antibiotic. In particular, three carboxylate-bearing polymers and one synthetic glycopolymer were selected for conjugation with polymyxin B (PMX B), namely, poly(α,L-glutamic acid) (PGlu), copolymer of L-glutamic acid and L-phenylalanine (P(Glu-co-Phe)), copolymer of N-vinyl succinamic acid and N-vinylsuccinimide (P(VSAA-co-VSI)), and poly(2-deoxy-2-methacrylamido-D-glucose) (PMAG). Unlike PGlu and PMAG, P(Glu-co-Phe) and P(VSAA-co-VSI) are amphiphilic and form nanoparticles in aqueous media. A number of conjugates with different polymyxin B loading were synthesized and characterized. In addition, the complex conjugates of PGLu or PMAG with polymyxin B and deferoxamine (siderophore) were obtained. A release of PMX B from Schiff base and amide-linked polymer conjugates was studied in model buffer media with pH 7.4 and 5.8. In both cases, a more pronounced release was observed under slightly acidic conditions. The cytotoxicity of free polymers and PMX B as well as their conjugates was examined in human embryonic kidney cells (HEK 293T cell line). All conjugates demonstrated reduced cytotoxicity compared to the free antibiotic. Finally, the antimicrobial efficacy of the conjugates against Pseudomonas aeruginosa was determined and compared. The lowest values of minimum inhibitory concentrations (MIC) were observed for polymyxin B and polymyxin B/deferoxamine conjugated with PMAG. Among the polymers tested, PMAG appears to be the most promising carrier for delivery of PMX B in conjugated form due to the good preservation of the antimicrobial properties of PMX B and the ability of controlled drug release.

Size Control and Improved Aqueous Colloidal Stability of Surface-Functionalized ZnGa2O4:Cr3+ Bright Persistent Luminescent Nanoparticles

Near-infrared (NIR)-emitting ZnGa2O4:Cr3+ (ZGO) persistent luminescent nanoparticles (PLNPs) have recently attracted considerable attention for diverse optical applications. The widespread use and promising potential of ZGO material in different applications arise from its prolonged post-excitation emission (several minutes to hours) that eliminates the need for continuous in situ excitation and the possibility of its excitation in different spectral regions (X-rays and UV-vis). However, the lack of precise control over particle size/distribution and its poor water dispersibility and/or limited colloidal stability required for certain biological applications are the major bottlenecks that limit its practical applications. To address these fundamental limitations, herein, we have prepared oleic acid (OA)-stabilized ZGO PLNPs with controlled size (7-12 nm, depending on the type of alcohol used in synthesis) and monodispersity. A further increase in size (8-21 nm), with a concomitant increase in persistent luminescence, could be achieved using a seed-mediated approach, employing the as-prepared ZGO PLNPs from the first synthesis as the seed and growing layers of the same material by adding fresh precursors. To remove their surface oleate groups and make the nanoparticles hydrophilic, two surface modification strategies were evaluated: modification with only poly(acrylic acid) (PAA) as the hydrophilic capping agent and modification with either PAA or cysteamine (Cys) as the hydrophilic capping agent in conjunction with BF4- as the intermediate surface modifier. The latter surface modifications involving BF4- conferred long-term (60 days and longer) colloidal stability to the nanoparticles in aqueous media, which is related to their favorable ζ potential values. The proposed generalized strategy could be used to prepare different kinds of surface-functionalized PLNPs with control of size, hydrophilicity, and colloidal stability and enhanced/prolonged persistent luminescence for diverse potential applications.

Liquid metal-mediated fabrication of metalloid nanoarchitectures.

By overcoming all conventional limitations associated with the synthesis of metalloid micro- and nanoparticles in aqueous media, we present a new one-step approach to the synthesis of highly crystalline metalloid hollow architectures. The liquid metal-mediated synthesis of Ge- and Sb-based hollow structures with satisfactory reaction kinetics at room temperature and normal pressure is presented.