Magnetic Microsphere Scaffold-Based Soft Microbots for Targeted Mesenchymal Stem Cell Delivery.

A soft microbot assembled from individual magnetic microsphere scaffold (MMS) beads carrying mesenchymal stem cells (MSC) is navigated under magnetic actuation, where an oscillating field induces mechanical flexion to propel the microbot toward the target site. A seven-bead microbot attained a top translational speed of 205.6 µm s-1 (0.068 body length s-1 ) under 10 mT and 2 Hz field oscillation. The shallow flexion angle (10-24.5°) allows precision movements required to navigate narrow spaces. Upon arrival at the target site, the MMS beads unload their MSC cargo following exposure to a phosphate-buffered saline (PBS) solution, mimicking the extracellular fluid's sodium concentration. The released stem cells have excellent viability and vitality, promoting rapid healing (i.e., 83.2% vs 49%) in a scratch-wound assay. When paired with minimally invasive surgical methods, such as laparoscopy and endoscopic surgery, the microbot can provide precise stem cell delivery to hard-to-reach injury sites in the body to promote healing. Moreover, the microbot is designed to be highly versatile, with individual MMS beads customizable for cargoes of live cells, biomolecules, bionanomaterials, and pharmaceutical compounds for various therapeutic requirements.

Hierarchically Branched Siloxane Brushes for Efficient Harvesting of Atmospheric Water.

Atmospheric water harvesting is considered a viable source of freshwater to alleviate water scarcity in an arid climate. Water condensation tends to be more efficient on superhydrophobic surfaces as the spontaneous coalescence-induced droplet jumping on superhydrophobic surfaces enables faster condensate removal. However, poor water nucleation on these surfaces leads to meager water harvest. A conventional approach to the problem is to fabricate micro- and nanoscale biphilic structures. Nonetheless, the process is complex, expensive, and difficult to scale. Here, the authors present an inexpensive and scalable method based on manipulating the water-repellent coatings of superhydrophobic surfaces. Flexible siloxane can facilitate water nucleation, while a branched structure promotes efficient droplet jumping. Moreover, ToF-SIMS analysis indicated that branched siloxane provides a better water-repellent coating coverage than linear siloxane and the siloxanes comprise hydrophilic and hydrophobic molecular segments. Thus, the as-prepared superhydrophobic surface, TiO2 nanorods coated with branched siloxanes harvested eight times more water than a typical fluoroalkylsilane (FAS)-coated surface under a low 30% relative humidity and performed better than most reported biphasic materials.

Modelling toluene sorption in ionic liquid/metal organic framework composite materials.

Toluene is a prevalent pollutant in indoor environments and its removal is essential to maintain a healthy environment. Adsorption is one of the best alternatives for organic vapours removal, specially at low indoor concentrations. Metal Organic Frameworks (MOFs) and Ionic Liquids (ILs) are potential materials for this mean. In this work, the synthesis and application of IL/MOF composite materials for toluene removal is reported. Loading [BMIM][CH3COO] ionic liquid into MIL101 porous structure improves parent materials affinity towards toluene capture by two orders of magnitude (as Henry's constants, attesting to their synergy). MIL101(Cr) and absorption in [BMIM][CH3COO] IL is best described by Henry's Law, while the Langmuir adsorption model predicts toluene adsorption on [BMIM][CH3COO]/MIL101(Cr) better than Freundlich and Toth equations. Diffusional and kinetics models revealed that toluene diffusion is the rate limiting step for pristine MIL101. Kinetic and diffusion rates were systematically improved upon the incorporation of the ionic liquid due to shorter toluene hops with the adsorbed IL and the increased hydrophobicity in the composites making the sorption more favourable. This study provides a systematic analysis and modelling of the toluene capture process in IL/MOF composites aiding a better understanding of the sorption process in these novel materials.

Functionalization of metal organic frameworks by [BMIM][CH3COO] ionic liquid for toluene capture.

Indoor exposure to volatile organic compounds (VOCs) is detrimental to the health of the occupants, and their removal is crucial in maintaining good air quality. Novel adsorbents prepared by modifying Metal-Organic Frameworks (MOFs), MIL101 (Cr), UiO-66, and UiO-66-NH2 with [BMIM][CH3COO] ionic liquid, were characterized and tested for toluene adsorption. [BMIM][CH3COO]/MIL101 performed best with a fast sorption rate, large sorption capacity, and good regenerability. It displays synergistic interactions between the IL and MOF. Adding one weight percent [BMIM][CH3COO] to UiO-66 and UiO-66-NH2 has a synergistic effect with respective 14% and 5% enhancements sorption over calculated values. The strong interactions between IL and UiO-66 and UiO-66-NH2, as observed in their thermogravimetric data, results in poor toluene sorption for 10 wt% [BMIM][CH3COO] loadings. This work provides a basis for IL modification of MOFs for enhanced sorption of VOCs for air treatment.

Operando Investigation of Toluene Oxidation over 1D Pt@CeO2 Derived from Pt Cluster-Containing MOF.

A unique 1D nanostructure of Pt@CeO2-BDC was prepared from Pt@CeBDC MOF. The Pt@CeO2-BDC was rich in oxygen vacancies (i.e., XPS Oß/(Oα + Oß) = 39.4%), and on the catalyst, the 2 nm Pt clusters were uniformly deposited on the 1D mesoporous polycrystalline CeO2. Toluene oxidation was conducted in a spectroscopic operando Raman-online FTIR reactor to elucidate the reaction mechanism and establish the structure-activity relationship. The reaction proceeds as follows: (I) adsorption of toluene as benzoate intermediates on Pt@CeO2-BDC at low temperature by reaction with surface peroxide species; (II) reaction activation and ring-opening involving lattice oxygen with a concomitant change in defect densities indicative of surface rearrangement; (III) complete oxidation to CO2 and H2O by lattice oxygen and reoxidation of the reduced ceria with consumption of adsorbed oxygen species. The Pt clusters, which mainly exist as Pt2+ with minor amounts of Pt0 and Pt4+ on the surface, facilitated the adsorption and reaction activation. The Pt-CeO2 interface generates reduced ceria sites forming nearby adsorbed peroxide at low temperature that oxidize toluene into benzoate species by a Langmuir-Hinshelwood mechanism. As the reaction temperature increases, the role of lattice oxygen becomes important, producing CO2 and H2O mainly by the Mars-van Krevelen mechanism.

A Novel Approach to High-Performance Aliovalent-Substituted Catalysts-2D Bimetallic MOF-Derived CeCuOx Microsheets.

Mixed transition metal oxides (MTMOs) have enormous potential applications in energy and environment. Their use as catalysts for the treatment of environmental pollution requires further enhancement in activity and stability. This work presents a new synthesis approach that is both convenient and effective in preparing binary metal oxide catalysts (CeCuOx ) with excellent activity by achieving molecular-level mixing to promote aliovalent substitution. It also allows a single, pure MTMO to be prepared for enhanced stability under reaction by using a bimetallic metal-organic framework (MOF) as the catalyst precursor. This approach also enables the direct manipulation of the shape and form of the MTMO catalyst by controlling the crystallization and growth of the MOF precursor. A 2D CeCuOx catalyst is investigated for the oxidation reactions of methanol, acetone, toluene, and o-xylene. The catalyst can catalyze the complete reactions of these molecules into CO2 at temperatures below 200 °C, representing a significant improvement in performance. Furthermore, the catalyst can tolerate high moisture content without deactivation.

Reactions of SO2 and NH3 with epoxy groups on the surface of graphite oxide powder.

Graphite oxide powder was obtained using the modified Hummers' method and characterized using X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The XPS results indicated that the epoxy groups were the main functional groups on the graphite oxide powder surface. The graphite oxide powder was then reacted with SO2 and NH3 gases, respectively, at 25 °C. The XPS and ToF-SIMS analyses of the surface of the reacted graphite oxide powder showed that the reactions mainly occurred in the epoxy groups. Bisulfate and amine groups were formed on the surface of the graphite oxide powder after the reactions between the graphite oxide powder and SO2 and NH3 gases. This work demonstrates a new method of removing SO2 and NH3 gases using graphite oxide powder.

Iron complex regulated synergistic effect between the current and peroxymonosulfate enhanced ultrafast oxidation of perfluorooctanoic acid via free radical dominant electrochemical reaction.

Iron complex regulated electrochemical reaction was triggered for revealing the reaction mechanism, degradation pathway, and applied potential of perfluorooctanoic acid (PFOA). The increased PMS concentrations, electrode spacing, and current density significantly enhanced PFOA elimination, with current density exhibiting a relatively strong interdependency to PFOA complete mineralization. The synergy between PMS and electrochemical reactions greatly accelerated PFOA decomposition by promoting the generation of key reaction sites, such as those for PMS activation and electrochemical processes, under various conditions. Furthermore, density functional theory calculations confirmed that the reciprocal transformation of Fe2+ and Fe3+ complexes was feasible under the electrochemical effect, further promoting the generation of active sites. The developed electrochemical oxidation with PMS reaction (EO/PMS) system can rapidly decompose and mineralize PFOA while maintaining strong tolerance to changing water matrices and organic and inorganic ions. Overall, it holds promise for use in treating and purifying wastewater containing PFOA.

The dominance of co-circulating SARS-CoV-2 variants in wastewater.

SARS-CoV-2 remains one of the biggest global health problems, which has already reached our wastewater through fecal shedding by COVID-19 patients. While the development of vaccines has mitigated the threats of the COVID-19 pandemic, the evolutionary dynamics of SARS-CoV-2 in wastewater lack monitoring and understanding. In this study, SARS-CoV-2 variants in wastewater were identified by analyzing 8511 wastewater-derived genome sequences from 9 countries from March 2020 to May 2023. The dominance of co-circulating variants was observed, namely B.1 in 2020, Alpha and Delta in 2021, then superseded by Omicron lineages in 2022 with a three-times increase. Mutations were also profiled, revealing nearly 5031 unique amino acid substitutions occurring approximately 371,591 times, some of which were associated with enhanced viral transmission and fitness. This study provided the first long-term multi-country overview of the prevalence of co-circulating SARS-CoV-2 lineages and mutations in wastewater and showed its comparison with conventional epidemiological surveillance. The results highlight the ability of wastewater-based genome monitoring to supplement clinical surveillance efforts in rapidly detecting viruses up to the strain level to keep track of their potential transmission routes and evolutionary dynamics.

Dissolvable Topical Formulations for Burst and Constant Delivery of Vitamin C.

Healthy skin has a high vitamin C concentration that protects against ultraviolet (UV)-induced damage, promotes wound healing, and lowers cancer risk. The present contribution describes two drug delivery systems for topical administration of vitamin C. The electrospun poly(vinyl alcohol) (PVA) nanofiber carrier of vitamin C exhibits a burst release profile (66 mg/g/h followed by 6.3 mg/g/h). In comparison, a new composite PVA nanofiber-molecular capsule delivers vitamin C at a constant rate (8.2 mg/g/h) with a zeroth-order release profile for better therapeutic management. Both delivery systems protect vitamin C and afford increased heat stability. The molecular capsules of ß-cyclodextrin with the vitamin C inclusion complex are immobilized on cellulose acetate and electrosprayed onto an electrospun PVA nanofiber mat.

Gel transformation as a general strategy for fabrication of highly porous multiscale MOF architectures.

The structure and chemistry of metal-organic frameworks or MOFs dictate their properties and functionalities. However, their architecture and form are essential for facilitating the transport of molecules, the flow of electrons, the conduction of heat, the transmission of light, and the propagation of force, which are vital in many applications. This work explores the transformation of inorganic gels into MOFs as a general strategy to construct complex porous MOF architectures at nano, micro, and millimeter length scales. MOFs can be induced to form along three different pathways governed by gel dissolution, MOF nucleation, and crystallization kinetics. Slow gel dissolution, rapid nucleation, and moderate crystal growth result in a pseudomorphic transformation (pathway 1) that preserves the original network structure and pores, while a comparably faster crystallization displays significant localized structural changes but still preserves network interconnectivity (pathway 2). MOF exfoliates from the gel surface during rapid dissolution, thus inducing nucleation in the pore liquid leading to a dense assembly of percolated MOF particles (pathway 3). Thus, the prepared MOF 3D objects and architectures can be fabricated with superb mechanical strength (>98.7 MPa), excellent permeability (>3.4 × 10-10 m2), and large surface area (1100 m2 g-1) and mesopore volumes (1.1 cm3 g-1).

A new versatile x-y-z electrospinning equipment for nanofiber synthesis in both far and near field.

This work describes a versatile electrospinning equipment with rapid, independent, and precise x-y-z movements for large-area depositions of electrospun fibers, direct writing or assembly of fibers into sub-millimeter and micron-sized patterns, and printing of 3D micro- and nanostructures. Its versatility is demonstrated thought the preparation of multilayered functional nanofibers for wound healing, nanofiber mesh for particle filtration, high-aspect ratio printed lines, and freestanding aligned nanofibers.

Exploration of perfluorooctane sulfonate degradation properties and mechanism via electron-transfer dominated radical process.

Polyfluoroalkyl and perfluoroalkyl chemicals (PFCs) widely used in lubricants, surfactant, textiles, paper coatings, cosmetics, and fire-fighting foams can release a large deal of organics contaminants into wastewater and pose great risks to the health of humans and eco-environments. Although advanced oxidation processes can effectively deconstruct various organic contaminants via reactive radicals, the stable structure of PFCs makes it difficult to be degraded. Here, we confirm that electrochemical oxidation process coupled with peroxymonosulfate (PMS) reaction can efficiently destroy stable structure of PFCs via electron transfer and meanwhile completely degrade PFCs via generated active radicals. We further studies via capturing and scavenging radicals, and DFT calculations find that electron hydroxyl radials play a dominant role in degrading PFCs. Based on the calculations of adsorption energy and molecular orbital energy we further demonstrate that many active sites on the surface of Ti4O7 (1 0 4) plane can rapidly take part in electrochemical reaction for generating radials and removing organic contaminants. These results give a promising insight towards high-effective and deep degradation of PFCs via electrochemical reaction coupled with advanced oxidation processes, as well as providing guidance and technical support for the remove of multiple organic contaminants.

Exploring key reaction sites and deep degradation mechanism of perfluorooctane sulfonate via peroxymonosulfate activation under electrocoagulation process.

Perfluorooctane sulfonate (PFOS), normally present in groundwater and surface water, is an emerging environmental contaminants, but is extremely difficult to be degraded due to high energy of the C-F bond. Here, an electrocoagulation (EC) technique coupled with peroxymonosulfate (PMS) activation was used to deeply degrade PFOS. Results showed that approximately 100% PFOS was removed from the solution in the monopolar serial (MS) mode within 60 min and achieved a high kinetic rate of 0.074 min-1, which was significantly higher than those of reported studies (Table S3). Energy consumption (2.06 kWh/kg) in the MS mode was significantly lower than that of Al (52.30 kWh/kg) and Zn (213.50 kWh/kg) electrodes, which further confirmed the potential application prospects of EC technique. The quenching experiments, electron spin response (ESR) analysis, and DFT calculations can verify that ·OH was the main radical from the reaction of Fe2+-OH reaction site with PMS. In addition, results from fluorine balance and TOC removal also indicated the complete mineralization and degradation of PFOS in the EC process. Quantum chemical calculations can confirm the PFOS degradation mechanism and key active sites for direct electron transfer and radical attack. After five cycle operations of PFOS degradation, the EC process was still effective in degrading PFOS with a removal efficiency above 98%. Thus, this work provided a novel alternative for the high-effective treatment of PFOS from contaminated environmental water bodies.

A multilevel antimicrobial coating based on polymer-encapsulated ClO(2).

A multilevel antimicrobial coating with "release-killing", "contact-killing" and "anti-adhesion" properties was prepared from polymer-encapsulated chlorine dioxide (ClO(2)), water-in-oil-in-water (w/o/w) double emulsion. A slow sustained release of gaseous ClO(2) at a rate sufficient to inhibit bacterial growth (approximately 1300 microg of ClO(2).g(-1).day(-1)) was demonstrated for a prolonged period of time (i.e., 28 days). Touch and infectious droplets triggered an increased release of the biocides at the sites of contamination, resulting in rapid disinfection. Zinc chloride (i.e., 30 ppm) was added to provide "contact-killing" properties, while bacterial adhesion was prevented by the Pluronic polymer used to encapsulate ClO(2). The new antimicrobial coating is effective against Gram positive and Gram negative bacteria, including Bacillus subtilis , Staphylococcus aureus , and Escherichia coli. A greater than 5 log (i.e., >or= 99.999%) reduction of viable bacteria was obtained at a short contact time of 10 min.

Non-UV germicidal activity of fresh TiO2 and Ag/TiO2.

Fresh TiO2 was found to possess a strong germicidal activity even without UV irradiation. Live Yeast (Saccharomyces cerevisiae) cells in contact with fresh TiO2 were found deformed and dead after 15 min contact. The cause of germicidal activity was discussed from the observed cell deformation, lysis and increased absorption at 1680 cm(-1) in FT-IR spectra of the affected cells, which proved the oxidizing effect of fresh TiO2 to cells. The deformation caused by the stretching of cell wall and pressure built-up inside the cell, led to cell burst and release of intracellular materials. The degree of cell deformation was found positively related with the wetting property of TiO2. Cells are negatively charged, for Gram-negative cell (thinner cell wall), a higher germicidal effect was observed than Gram-positive cells. The germicidal effect of TiO2 gradually decreased after exposure to air at room temperature, as the wetting property decreased. This kind of germicidal activity was more effective compared to other germicidal process such as UVA/TiO2 or Ag+. This shed light on designing new germicidal material either maintained by visible light irradiation, or by oxidation effect generated by reactive oxygen species.

Synthesis of nanostructured Ag@SiO2-Penicillin from high purity Ag NPs prepared by electromagnetic levitation melting process.

Nanostructured Ag@SiO2-Penicillin was synthesized from high-purity Ag0 NPs with a mean particle size of about 10 nm produced by electromagnetic levitation gas condensation (ELGC) method. The silver and penicillin contents of the synthesized nano-antibiotic were about 34 wt% and 2.5 wt% respectively, as determined by ICP-OES and TGA analyses. The antibacterial properties and synergistic effects of nanostructured Ag@SiO2 and Ag@SiO2-Penicillin on killing the Methicillin-susceptible S. aureus (MSSA) and Methicillin-resistant S. aureus (MRSA) bacteria were also examined. The nanoparticles were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Ag@SiO2-Penicillin NPs showed an outstanding antibacterial activity compared to Penicillin and Ag@SiO2 NPs. The Fractional inhibitory concentration (FIC) indexes were 0.54 and 0.52 against MSSA and MRSA bacteria respectively, illustrating the synergistic effects of Ag@SiO2-Penicillin NPs. In addition, Ag@SiO2-Penicillin NPs showed promising dose-dependent cytotoxicity effects indicating the protective effects emanating from anti-inflammatory properties of penicillin.

Selective mesoporous adsorbents for Ag+/Cu2+ separation.

Three different approaches, including (1) manipulating the site chemistry, (2) controlling the spacing between neighbouring sites and (3) altering the adsorbates by the use of chelates, were successfully used to prepare MCM-41 adsorbents with excellent selectivity for silver adsorption from solutions containing copper.

Non-UV based germicidal activity of metal-doped TiO2 coating on solid surfaces.

A stain-based screening method was developed to screen different catalyst coatings for their germicidal activity. A Baclight dead/live bacteria viability kit (invitrogen, molecular probes) was used for staining the cell. The screening was carried out following a standard procedure. This included loading cell suspension to solid surface and maintaining contact for 30 min, then staining with a mixture containing dyes. The stained cells were observed using an epifluorescent microscope and photographed with a CCD camera under UV. Metal-doped TiO2 coatings on Al plates were prepared and tested for non-UV germicidal activity without using UV. It was tested using model microorganisms such as Bakers Yeast (Saccharomyces cerevisiae), Bacillus subtilis, Pseudomonas putida, and Escherichia coli. On the basis of the germicidal activity of catalyst and the degree of damage caused to the cells, the stained cells may appear green (viable), green with red or yellow nuclei and yellow (compromised) or red (nonviable). According to their stained color, cells were counted to calculate the percentage of dead, live, and compromised cells. Compromised cells are cells that grow very slowly after reculturing indicating a degree of reversible cell damage. Screening the germicidal activity using this staining method is accurate and efficient, and requires less time than the culture-based method. A modification to the procedure for measuring germicidal activity of rough surfaces or fibrous coatings was developed. Both TiO2 and metal-doped TiO2 (Ag, Pt, Au, Cu) possess non-UV based germicidal activity. The germicidal activity of TiO2 was found to be related with its wetting property and can be improved by UV irradiation before testing. It is not greatly affected by contact time, indicating a fast acting germicidal activity.

An investigation of gold adsorption from a binary mixture with selective mesoporous silica adsorbents.

Gold-selective adsorbents were prepared from mesoporous MCM-41 silica by grafting organic amine groups (i.e., RNH2, R2NH, and R3N; R=propyl). NH2-MCM-41, NRH-MCM-41, and NR2-MCM-41 displayed strong affinity for gold and at 1 mmol/g loading adsorbed 0.40, 0.33, and 0.20 mmol/g of gold. Copper and nickel were not adsorbed on these adsorbents. Grafting surface chemical moieties introduces heterogeneity on an otherwise uniform MCM-41 pore surface and metal adsorption is best described by the Freundlich adsorption model. A series of binary adsorption equilibrium studies with NH2-MCM-41 containing 2.2 mmol RNH2/g shows that NH2-MCM-41 adsorbs only gold from solutions containing copper and nickel with an adsorption capacity of 0.6 mol of Au/mol of RNH2 (1.1 mmol of Au/g of NH2-MCM-41). Copper and nickel were not adsorbed by NH2-MCM-41 regardless of the solution concentration, composition, and pH (i.e., 2 to 4) in the presence of gold. The LeVan and Vermeulen adsorption model based on a single component Freundlich isotherm and corrected for the anion effect accurately predicted the binary adsorptions. The adsorbed gold was completely recovered by a simple acid wash and the recovered gold solution is 99% pure. The regenerated NH2-MCM-41 remained 100% selective for gold removal and exhibited the same adsorption capacity even after several uses.