Photo-Enhanced Chemo-Transistor Platform for Ultrasensitive Assay of Small Molecules.

Compared with traditional assay techniques, field-effect transistors (FETs) have advantages such as fast response, high sensitivity, being label-free, and point-of-care detection, while lacking generality to detect a wide range of small molecules since most of them are electrically neutral with a weak doping effect. Here, we demonstrate a photo-enhanced chemo-transistor platform based on a synergistic photo-chemical gating effect in order to overcome the aforementioned limitation. Under light irradiation, accumulated photoelectrons generated from covalent organic frameworks offer a photo-gating modulation, amplifying the response to small molecule adsorption including methylglyoxal, p-nitroaniline, nitrobenzene, aniline, and glyoxal when measuring the photocurrent. We perform testing in buffer, artificial urine, sweat, saliva, and diabetic mouse serum. The limit of detection is down to 10-19 M methylglyoxal, about 5 orders of magnitude lower than existing assay technologies. This work develops a photo-enhanced FET platform to detect small molecules or other neutral species with enhanced sensitivity for applications in fields such as biochemical research, health monitoring, and disease diagnosis.

Ultraprecise Antigen 10-in-1 Pool Testing by Multiantibodies Transistor Assay.

Effective screening of infectious diseases requires a fast, cheap, and population-scale testing. Antigen pool testing can increase the test rate and shorten the screening time, thus being a valuable approach for epidemic prevention and control. However, the overall percent agreement (OPA) with polymerase chain reaction (PCR) is one-half to three-quarters, hampering it from being a comprehensive method, especially pool testing, beyond the gold-standard PCR. Here, a multiantibodies transistor assay is developed for sensitive and highly precise antigen pool testing. The multiantibodies capture SARS-CoV-2 spike S1 proteins with different configurations, resulting in an antigen-binding affinity down to 0.34 fM. The limit of detection reaches 3.5 × 10-17 g mL-1SARS-CoV-2 spike S1 protein in artificial saliva, 4-5 orders of magnitude lower than existing transistor sensors. The testing of 60 nasopharyngeal swabs exhibits ∼100% OPA with PCR within an average diagnoses time of 38.9 s. Owing to its highly precise feature, a portable integrated platform is fabricated, which achieves 10-in-1 pooled screening for high testing throughput. This work solves the long-standing problem of antigen pool testing, enabling it to be a valuable tool in precise diagnoses and population-wide screening of COVID-19 or other epidemics in the future.

Structure and properties of PLLA/ß-TCP nanocomposite scaffolds for bone tissue engineering.

One of the key components of tissue engineering is a scaffold with suitable morphology, outstanding mechanical properties, and favorable biocompatibility. In this study, ß-tricalcium phosphate (ß-TCP) nanoparticles were synthesized and incorporated with poly(L-lactic acid) (PLLA) to fabricate nanocomposite scaffolds by the thermally induced phase separation method. The PLLA/ß-TCP nanocomposite scaffolds showed a continuous nanofibrous PLLA matrix with strut diameters of 100-750 nm, interconnected micropores with pore diameters in the range of 0.5-10 µm, and high porosity (>92 %). ß-TCP nanoparticles were homogeneously dispersed in the PLLA matrix, which significantly improved the compressive modulus and protein adsorption capacity. The prepared nanocomposite scaffolds provided a suitable microenvironment for osteoblast attachment and proliferation, demonstrating the potential of the PLLA/ß-TCP nanocomposite scaffolds in bone tissue engineering applications.

Ultra-fast supercritically solvothermal polymerization for large single-crystalline covalent organic frameworks.

Crystalline polymer materials, e.g., hyper-crosslinked polystyrene, conjugate microporous polymers and covalent organic frameworks, are used as catalyst carriers, organic electronic devices and molecular sieves. Their properties and applications are highly dependent on their crystallinity. An efficient polymerization strategy for the rapid preparation of highly or single-crystalline materials is beneficial not only to structure-property studies but also to practical applications. However, polymerization usually leads to the formation of amorphous or poorly crystalline products with small grain sizes. It has been a challenging task to efficiently and precisely assemble organic molecules into a single crystal through polymerization. To address this issue, we developed a supercritically solvothermal method that uses supercritical carbon dioxide (sc-CO2) as the reaction medium for polymerization. Sc-CO2 accelerates crystal growth due to its high diffusivity and low viscosity compared with traditional organic solvents. Six covalent organic frameworks with different topologies, linkages and crystal structures are synthesized by this method. The as-synthesized products feature polarized photoluminescence and second-harmonic generation, indicating their high-quality single-crystal nature. This method holds advantages such as rapid growth rate, high productivity, easy accessibility, industrial compatibility and environmental friendliness. In this protocol, we provide a step-by-step procedure including preparation of monomer dispersion, polymerization in sc-CO2, purification and characterization of the single crystals. By following this protocol, it takes 1-5 min to grow sub-mm-sized single crystals by polymerization. The procedure takes ~4 h from preparation of monomer dispersion and polymerization in sc-CO2 to purification and drying of the product.

Preparation of carboxymethyl cellulose/chitosan-CuO giant vesicles for the adsorption and catalytic degradation of dyes.

To effectively remove the dyes from wastewater, novel carboxymethyl cellulose/chitosan-CuO giant vesicles with dual function of adsorption and catalytic degradation were prepared. The vesicles were facilely obtained via blending chitosan solution and carboxymethyl cellulose/CuO mixed solution with sequent fast and slow stirring. The removal ratios of methyl orange (MO) and acid black-172 (AB) can reach 86.3% and 88.6% with the catalytic oxidation system of ammonium persulfate and vesicles. Compared with the CuO catalysis without the vesicles, the degradation rates of MO and AB increased by 1.3 and 3.1 times, respectively. The enhanced dye removal is ascribed to the excellent dye adsorption capacity of giant vesicles. Furthermore, the giant vesicles worked well in wide ranges of environmental pH and temperature, and exhibited excellent stability and reusability. This study provides a facile method to load catalyst onto polymeric giant vesicle with outstanding performance for the adsorption and catalytic degradation of dyes.

Electrospun molecularly imprinted sodium alginate/polyethylene oxide nanofibrous membranes for selective adsorption of methylene blue.

Molecular imprinting technique is an efficient method to improve the selective adsorption capacity for the target pollutant. In this study, sodium alginate/polyethylene oxide molecularly imprinted nanofibrous membrane (SA/PEO-MINM) with average diameter of 185 ± 20 nm was successfully synthesized by electrospinning for selective adsorption of methylene blue (MB). Benefiting from the molecular imprinted technology, the adsorption amount of SA/PEO-MINM for MB was increased by about 65%, significantly higher than the non-imprinted membrane. Results showed that the adsorption equilibrium could be well fitted with Langmuir isotherm model and the maximum adsorption capacity towards MB was 3186.7 mg/g. Kinetic experiments well complied with the Pseudo second order model. Reusability studies indicated that the removal efficiency of MB could maintain 93% of the original adsorption capacity after four consecutive adsorption/desorption cycles. More importantly, the SA/PEO-MINM with high surface area and specific adsorption recognition sites showed excellent selective adsorption capacity in the adsorption experiment of MB and methylene orange mixed dye solution. In general, the SA/PEO-MINM can be successfully applied for the selective removal of MB from dye wastewater.

Efficient electrotransformation of Rhodococcus ruber YYL with abundant extracellular polymeric substances via a cell wall-weakening strategy.

Rhodococcus spp. have broad potential applications related to the degradation of organic contaminants and the transformation or synthesis of useful compounds. However, some Gram-positive bacteria are difficult to manipulate genetically due to low transformation efficiency. In this study, we investigated the effects of chemicals including glycine, isonicotinic acid hydrazide (INH), Tween 80 and penicillin G, as well as cell growth status, competent cell concentration, electroporation field strength, electroporation time and heat shock time, on the electrotransformation efficiency of the tetrahydrofuran-degrading bacterium Rhodococcus ruber YYL with low transformation efficiency. The highest electrotransformation efficiency was 1.60 × 106 CFU/µg DNA after parameter optimization. GmhD (D-glycero-D-manno-heptose 1-phosphate guanosyltransferase) gene, which is important in the biosynthesis of lipopolysaccharide, was deleted via the optimized electrotransformation method. Compared with wild-type strain, YYL ΔgmhD showed extremely high electrotransformation efficiency because the surface of it had no mushroom-like extracellular polymeric substances (EPS). In addition, the results showed that cell wall-weakening reagents might cause some translucent substances like EPS, to detach from the cells, increasing the electrotransformation efficiency of strain YYL. We propose that these results could provide a new strategy for unique bacteria that are rich in EPS, for which genetic manipulation systems are difficult to establish.

Fabrication and characterization of nano composite scaffold of poly(L-lactic acid)/hydroxyapatite.

To mimic the nano-fibrous structure of the natural extracellular matrix, a nano composite scaffold of poly(L-lactic acid)/hydroxyapatite(PLLA/HAP) was fabricated by a thermally induced phase separation method. The characterization of the composite scaffold showed that the scaffold had a nano-fibrous PLLA network (fiber size 100-750 nm), an interconnective microporous structure (1-10 microm) and high porosity (>90%). HAP was homogeneously distributed in the scaffold, as a result, the compressive modulus of PLLA/HAP (80:20, w/w) increased to 3.15-fold compared with that of a pure PLLA scaffold. Incorporating HAP into PLLA network also buffered the pH decline in vitro degradation and enhanced the protein adsorption of the composite scaffold significantly. The new nano composite scaffold is potentially a very promising scaffold for tissue engineering.

Microwave assisted copolymerization of sodium alginate and dimethyl diallyl ammonium chloride as flocculant for dye removal.

Flocculant made from natural polymers has the advantages of abundant source, affordable cost and environmental friendliness. In this work, a binary flocculant (sodium alginate-dimethyl diallyl ammonium chloride, SAD) was successfully prepared using microwave assisted free radical copolymerization technique. Based on the flocculation properties of yellow 7GL dye, the synthetic process was optimized with the amount of initiator was 0.8 wt% (equal molar ratio of ammonium peroxydisulfate and sodium bisulfite as complex initiator), sodium alginate: dimethyl diallyl ammonium chloride = 1:1 (molar ratio), and the microwave irradiation time was 18 min at the power of 280 W. The experimental results show that the color removal ratio was 73.5% at the SAD dosage of 425 mg/L for the 100 mg/L yellow 7GL simulated wastewater. The SAD also maintained excellent decolorization ratios under a wide range of flocculant dosage and environmental pH. The flocculation mechanism might be the combination of charge neutralization and bridging effect. The prepared SAD flocculant has the virtues of simple synthesis process, ecofriendliness and high decolorization ratio, which make it broad application prospect in the treatment of dye wastewater.

Red-blood-cell-membrane-enveloped magnetic nanoclusters as a biomimetic theranostic nanoplatform for bimodal imaging-guided cancer photothermal therapy.

The use of red blood cell (RBC) membrane coatings has recently been found to be a biomimetic strategy to confer inner core nanomaterials with improved pharmacokinetic profiles by utilizing the intrinsic long blood circulation time of RBCs. Here, we envelope superparamagnetic nanoclusters (MNCs) with RBC membrane ghosts to obtain MNC@RBCs with significantly improved physiological stability compared to that of bare MNCs. After being loaded with near-infrared (NIR) cypate molecules, the as-prepared Cyp-MNC@RBCs show remarkably increased NIR absorbance and resultant efficient photothermal conversion efficacy. By tracking the NIR fluorescence of cypate in an in vivo fluorescence imaging system, we uncover that such Cyp-MNC@RBCs upon intravenous injection show significantly improved tumor-homing capacity as compared to bare cypate-loaded MNCs. A similar result is further evidenced by recording the T2-weighted magnetic resonance imaging (MRI) signal of MNCs. Furthermore, upon exposure to 808 nm laser irradiation, the tumors grown on the mice with the intravenous injection of Cyp-MNC@RBCs show a higher temperature increase than the tumors grown on the mice injected with plain MNC@RBCs and thus are significantly suppressed via photothermal ablation. This study presents the preparation of biomimetic Cyp-MNC@RBCs with greatly improved tumor-homing capacity as multifunctional nanotheranostic agents for fluorescence and MRI bimodal imaging-guided cancer photothermal therapy.

Chitosan coated polyacrylonitrile nanofibrous mat for dye adsorption.

Chitosan is a promising natural-derived polymer for dye adsorption owing to its rich source, good biodegradablity and high adsorption capacity. However, electrospinning of pure chitosan nanofiber needs high concentration of acid solution and the electrospinning productivity is very low due to its high degree of hydrogen bonding and polycationic nature. To solve the problem, the chitosan coated polyacrylonitrile nanofibrous mat (CPNM) was successfully prepared via a two-step fabrication process of polyacrylonitrile electrospinning and a subsequent chitosan coating. The chitosan was homogeneously adhered onto the PAN nanofibers, which improved the hydrophilicity and adsorption capacity of Acid Blue-113 significantly. The adsorption of Acid Blue-113 on CPNM fitted the pseudo-second-order kinetics model well, and the maximum adsorption capacity of CPNM calculated from the Langmuir isotherm model was 1708 mg/g with the average fiber diameter of 189 nm. The CPNM demonstrate the virtue of simple fabrication process, high adsorption capacity and good reusability, which is a promising adsorbent for dye removal.

Size Dependency of Circulation and Biodistribution of Biomimetic Nanoparticles: Red Blood Cell Membrane-Coated Nanoparticles.

Recently, biomimetic nanoparticles, especially cell membrane-cloaked nanoparticles, have attracted increasing attention in biomedical applications, including antitumor therapy, detoxification, and immune modulation, by imitating the structure and the function of biological systems such as long circulation life in the blood. However, the circulation time of cell membrane-cloaked nanoparticles is far less than that of the original cells, greatly limiting their biomedical applications, while the underlying reasons are seldom demonstrated. In this study, the influence of particle size on the circulation and the biodistribution of red blood cell membrane-coated nanoparticles (RBC-NPs) as model biomimetic nanoparticles were investigated. Differently sized RBC-NPs (80, 120, 160, and 200 nm) were prepared by fusing RBC membranes on poly(lactic-co-glycolic acid) nanoparticles. It was shown that the particle size did not change the cellular uptake of these biomimetic nanoparticles by macrophage cells in vitro and their immunogenic responses in vivo. However, their circulation life in vivo decreased with the particle size, while their accumulation in the liver increased with the particle size, which might be related to their size-dependent filtration through hepatic sinusoids. These findings will provide experimental evidence for the design and the optimization of biomimetic nanoparticles.

Sources and transport of methylmercury in the Yangtze River and the impact of the Three Gorges Dam.

The magnitude of environmental change due to anthropogenic impacts might greatly exceed that of natural disturbances. In this work, we quantitatively examine the impacts of river damming, soil erosion, and point-source release on the transport of methylmercury (MeHg) throughout the Yangtze River, the third longest river in the world. Based on seasonal observations and the subsequent material flow analysis, we found that in 2016, the Yangtze River discharged 470 ±â€¯200 kg MeHg to the coastal and shelf areas, a value at least ten-fold larger than existing observations in other large rivers around the world. The construction of the Three Gorges Dam (TGD), the world's largest hydropower dam, induced a substantial amount of MeHg (at least 250 ±â€¯220 kg) accumulation in the reservoir and a relatively small amount of MeHg (150 ±â€¯37 kg) discharge to the downstream region in 2016. The reservoir itself is not expected to be more contaminated by MeHg than the downstream areas of the river after the TGD, and the TGD has an additive effect on downstream MeHg transport. The riverine MeHg flux in the river mouth was 3-fold that discharged from the TGD mainly due to TGD-induced resuspension of MeHg from the downstream riverbed, as well as MeHg imports to the downstream area from tributaries, soil erosion, municipal wastewater, and in situ production. Our analysis offers new evidence that in future decades, the increase in estuarine MeHg contamination resulting from the increasing construction of large dams might pose a challenge for global coastal fisheries.

Fabrication of pure chitosan nanofibrous membranes as effective absorbent for dye removal.

The pure chitosan nanofibrous membranes with average fiber diameter of 86±18, 114±17,164±28nm were successfully prepared by electrospinning. Batch adsorption experiments of using chitosan nanofibrous membranes as adsorbent to remove acid blue-113 were conducted. The adsorption capacity of 1377mg/g was achieved by the chitosan nanofibrous membrane with average fiber diameter of 86nm, which was superior to the chitosan microscale sample with the adsorption capacity of 412mg/g. The average fiber diameter and the corresponding equilibrium adsorption capacity of pure chitosan nanofibrous membranes fitted well with linear relationship in our test range. The results also showed that the adsorption followed with pseudo second-order kinetics model, and the adsorption behavior was accordance with the Langmuir isotherm model. The pure chitosan nanofibrous membrane showed promise and feasibility as an effective adsorbent for dye removal.

Enhanced photothermal therapy of biomimetic polypyrrole nanoparticles through improving blood flow perfusion.

In this study, we reported a strategy to improve delivery efficiency of a long-circulation biomimetic photothermal nanoagent for enhanced photothermal therapy through selectively dilating tumor vasculature. By using a simply nanocoating technology, a biomimetic layer of natural red blood cell (RBC) membranes was camouflaged on the surface of photothermal polypyrrole nanoparticles (PPy@RBC NPs). The erythrocyte-mimicking PPy NPs inherited the immune evasion ability from natural RBC resulting in superior prolonged blood retention time. Additionally, excellent photothermal and photoacoustic imaging functionalities were all retained attributing to PPy NPs cores. To further improve the photothermal outcome, the endothelin A (ETA) receptor antagonist BQ123 was jointly employed to regulate tumor microenvironment. The BQ123 could induce tumor vascular relaxation and increase blood flow perfusion through modulating an ET-1/ETA transduction pathway and blocking the ETA receptor, whereas the vessel perfusion of normal tissues was not altered. Through our well-designed tactic, the concentration of biomimetic PPy NPs in tumor site was significantly improved when administered systematically. The study documented that the antitumor efficiency of biomimetic PPy NPs combined with specific antagonist BQ123 was particularly prominent and was superior to biomimetic PPy NPs (P < 0.05) and PEGylated PPy NPs with BQ123 (P < 0.01), showing that the greatly enhanced photothermal treatment could be achieved with low-dose administration of photothermal agents. Our findings would provide a promising procedure for other similar enhanced photothermal treatment by blocking ETA receptor to dramatically increase the delivery of biomimetic photothermal nanomaterials.

Numerical simulation of PAHs sorption/desorption on soil with the influence of Tween80.

In this paper, the influences of inionic surfactant Tween80 on polycyclic aromatic hydrocarbons (PAHs) sorption/desorption on artificially contaminated soil were studied, and gamma model was applied to simulate the influences. Results showed that, with the use of Tween 80, the sorption behaviors of PAHs on soil altered significantly. Adsorbed Tween 80 increased the sorption amount of PAHs while the dissolved Tween80 increased the apparent solubility of PAHs. These two processes exert influences on the sorption coefficient of PAHs in soil-water system, which can be depicted by apparent sorption coefficient. The partition coefficients (the soil/water partition coefficient of PAHs and surfactants obtained from sorption experiments) and statistical parameters used in the amended gamma model were obtained in independent experiments. With these parameters, the gamma model could provide a satisfactory independent prediction of PAHs release from soil to aqueous phase at two surfactant concentrations.

The effect of fiber size and pore size on cell proliferation and infiltration in PLLA scaffolds on bone tissue engineering.

The scaffold microstructure has a great impact on cell functions in tissue engineering. Herein, the PLLA scaffolds with hierarchical fiber size and pore size were successfully fabricated by thermal-induced phase separation or combined thermal-induced phase separation and salt leaching methods. The PLLA scaffolds were fabricated as microfibrous scaffolds, microfibrous scaffolds with macropores (50-350 µm), nanofibrous scaffolds with micropores (100 nm to 10 µm), and nanofibrous scaffolds with both macropores and micropores by tailoring selective solvents for forming different fiber size and pre-sieved salts for creating controlled pore size. Among the four kinds of PLLA scaffolds, the nanofibrous scaffolds with both macropores and micropores provided a favorable microenvironment for protein adsorption, cell proliferation, and cell infiltration. The results further confirmed the significance of fiber size and pore size on the biological properties, and a scaffold with both micropores and macropores, and a nanofibrous matrix might have promising applications in bone tissue engineering.

Fabrication and biocompatibility of poly(l-lactic acid) and chitosan composite scaffolds with hierarchical microstructures.

The scaffold microstructure is crucial to reconstruct tissue normal functions. In this article, poly(l-lactic acid) and chitosan fiber (PLLA/CTSF) composite scaffolds with hierarchical microstructures both in fiber and pore sizes were successfully fabricated by combining thermal induced phase separation and salt leaching techniques. The composite scaffolds consisted of a nanofibrous PLLA matrix with diameter of 50-500nm, and chitosan fibers with diameter of about 20µm were homogenously distributed in the PLLA matrix as a microsized reinforcer. The composite scaffolds also had high porosity (>94%) and hierarchical pore size, which were consisted of both micropores (50nm-10µm) and macropores (50-300µm). By tailoring the microstructure and chemical composition, the mechanical property, pH buffer and protein adsorption capacity of the composite scaffold were improved significantly compared with those of PLLA scaffold. Cell culture results also revealed that the PLLA/CTSF composite scaffolds supported MG-63 osteoblast proliferation and penetration.

Preparation of lignosulfonate-acrylamide-chitosan ternary graft copolymer and its flocculation performance.

As flocculant plays an important role in wastewater treatment, searching for high efficient and cost-effective flocculants has always become the challenge in chemical industry. In the current work, lignosulfonate-acrylamide-chitosan ternary copolymer was designed and prepared as a new kind of flocculant. The elemental analysis and structure characterization of FTIR and XRD showed that acrylamide successfully grafted onto the two natural polymers and amorphous macromolecules were formed. The natural polymers-based flocculant was water soluble and pH independent. As it had multiple functional groups from the raw materials, the amphoteric flocculant showed high color removal efficiency to anionic (acid blue 113, >95%), neutral (reactive black 5, >95%) and cationic dyes (methyl orange, >50%) in a wide range of flocculant dosage and pH windows. The ternary flocculant, based on lignosulfonate, chitosan, and acrylamide, might be a promising material in practical applications from the perspective of cost, source and performance.

Fabrication of PLLA/ß-TCP nanocomposite scaffolds with hierarchical porosity for bone tissue engineering.

Polymer and ceramic composite scaffolds play a crucial role in bone tissue engineering. In an attempt to mimic the architecture of natural extracellular matrix (ECM), poly(l-lactic acid)/ß-tricalcium phosphate (PLLA/ß-TCP) nanocomposite scaffolds with a hierarchical pore structure were fabricated by combining thermal induced phase separation and salt leaching techniques. The nanocomposite scaffold consisted of a nanofibrous PLLA matrix with a highly interconnected, high porosity (>93%) hierarchical pore structure with pore diameters ranging from 500nm to 300µm and a homogeneously distributed ß-TCP nanoparticle phase. The nanofibrous PLLA matrix had a fiber diameter of 70-300nm. The nanocomposite scaffolds possess three levels of hierarchical structure: (1) porosity; (2) nanofibrous PLLA struts comprising the pore walls; and (3) ß-TCP nanoparticle phase. The ß-TCP nanoparticle phase improved the mechanical properties and bioactivity of the PLLA matrix. The nanocomposite scaffolds supported MG-63 osteoblast proliferation, penetration, and ECM deposition, indicating the potential of PLLA/ß-TCP nanocomposite scaffolds with hierarchical porosity for bone tissue engineering applications.