Specifically and Visually Detect Methyl-Mercury and Ethyl-Mercury in Fish Sample Based on DNA-Templated Alloy Ag-Au Nanoparticles.

Methyl-mercury (CH3Hg+) and ethyl-mercury (C2H5Hg+) have much higher toxicity than Hg2+ and can be more easily accumulated by organisms to form severe bioamplification. Hence, the specific and on-site detection of CH3Hg+ and C2H5Hg+ in seafood is of great significance and a hard challenge. We herein designed two T-rich aptamers (HT5 and HT7) for specifically recognizing CH3Hg+ and the total of CH3Hg+ and C2H5Hg+, respectively. In the presence of all Au3+, Ag+, and T-rich aptamer, CH3Hg+ and C2H5Hg+ specifically and preferentially bind with aptamer and thus induced the formation of alloy Ag-Au nanoparticles after reduction, which led to the color change in solution. This provided a sensing platform for the instrument-free visual discrimination and detection of CH3Hg+ and C2H5Hg+. By using HT5 as probe, the method can be used to detect as low as 5.0 µM (equivalent to 1.0 µg Hg/g) of CH3Hg+ by bare eye observation and 0.5 µM (equivalent to 100 ng Hg/g) of CH3Hg+ by UV-visible spectrometry. By using HT7 as probe, the method can be used to detect the total concentration of CH3Hg+ and C2H5Hg+ with a visual detection limit of 5.0 µM (equivalent to 1.0 µg Hg/g) and a UV-visible spectrometry detection limit of 0.6 µM (equivalent to 120 ng Hg/g). The proposed method has been successfully used to detect CH3Hg+ and C2H5Hg+ in fish muscle samples with a recovery of 101-109% and a RSD ( n = 6) < 8%. The success of this study provided a potential method for the specific and on-site detection of CH3Hg+ and C2H5Hg+ in seafood by only bare eye observation.

Electrophoretic Deposition of Gentamicin-Loaded Silk Fibroin Coatings on 3D-Printed Porous Cobalt-Chromium-Molybdenum Bone Substitutes to Prevent Orthopedic Implant Infections.

In addition to customizing shapes of metal bone substitutes for patients, the 3D printing technique can reduce the modulus of the substitutes through the design and manufacture of interconnected porous structures, achieving the modulus match between substitute and surrounding bone to improve implant longevity. However, the porous bone substitutes take more risks of postoperative infection due to its much larger surface area compared with the traditional casting solid bone substitute. Here, we prepared of gentamicin-loaded silk fibroin coatings on 3D-printed porous cobalt-chromium-molybdenum (CoCrMo) bone substitutes via electrophoretic deposition technique. Through optimization, relatively intact, continuous, homogeneous, and conformal coatings with a thickness of 2.30 ± 0.58 µm were deposited around the struts with few pore blocked. The porous metal structures exhibited no loss in mechanical properties after the anode galvanic corrosion in EPD process. The initial osteoblastic response on coatings was better than that on metal surface, including cell spreading, proliferation and cytotoxicity. Antibacterial efficacy experiments showed that the coatings had an antibacterial effect on both adherent and planktonic bacteria within 1 week. These results suggested that the beneficial properties of anode electrophoretic deposited silk fibroin coatings could be exploited to improve the biological functionality of porous structures made of medical metals.

Chemical Interactions of Polyethylene Glycols (PEGs) and Glycerol with Protein Functional Groups: Applications to Effects of PEG and Glycerol on Protein Processes.

In this work, we obtain the data needed to predict chemical interactions of polyethylene glycols (PEGs) and glycerol with proteins and related organic compounds and thereby interpret or predict chemical effects of PEGs on protein processes. To accomplish this, we determine interactions of glycerol and tetraEG with >30 model compounds displaying the major C, N, and O functional groups of proteins. Analysis of these data yields coefficients (α values) that quantify interactions of glycerol, tetraEG, and PEG end (-CH2OH) and interior (-CH2OCH2-) groups with these groups, relative to interactions with water. TetraEG (strongly) and glycerol (weakly) interact favorably with aromatic C, amide N, and cationic N, but unfavorably with amide O, carboxylate O, and salt ions. Strongly unfavorable O and salt anion interactions help make both small and large PEGs effective protein precipitants. Interactions of tetraEG and PEG interior groups with aliphatic C are quite favorable, while interactions of glycerol and PEG end groups with aliphatic C are not. Hence, tetraEG and PEG300 favor unfolding of the DNA-binding domain of lac repressor (lacDBD), while glycerol and di- and monoethylene glycol are stabilizers. Favorable interactions with aromatic and aliphatic C explain why PEG400 greatly increases the solubility of aromatic hydrocarbons and steroids. PEG400-steroid interactions are unusually favorable, presumably because of simultaneous interactions of multiple PEG interior groups with the fused ring system of the steroid. Using α values reported here, chemical contributions to PEG m-values can be predicted or interpreted in terms of changes in water-accessible surface area (ΔASA) and separated from excluded volume effects.

In-situ polymerization of phosphorus/nitrogen flame-retardant coating for polyester/cotton blend fabrics with superior durability.

The durable flame-retardant functional coating of polyester/cotton (T/C) blend fabrics is both interesting and challenging. In this study, a novel in-situ polymerization strategy for phosphorus/nitrogen-based flame-retardant on T/C blend samples was developed through the polycondensation of tetramethylolphosphonium sulfate, dicyandiamide, and anionic cyclic phosphate ester. The chemical structure of the polycondensation compounds, as well as the surface morphology, combustion behavior, flame-retardant capacity, washing durability and flame-retardant mechanism of the coated T/C blend fabrics, were investigated. The coated T/C blend fabrics demonstrated excellent self-extinguishing performance, with the damaged length decreasing to as low as 8.0 cm and the LOI reaching 28 %. Moreover, the peak heat release rate of the coated T/C blend fabrics decreased by 39.7 %. The superior flame retardancy can be attributed to the enhanced dehydration and carbonization by phosphate groups in the condensed phase, as well as the quenching effect and diluting effect in the gas phase. Additionally, the coated T/C blend fabrics exhibited remarkable washing durability and still achieved self-extinguishing after 65 washing cycles, and the in-situ deposition of insoluble three-dimensional polycondensation compounds onto the T/C blend fabrics was beneficial. The flame-retardant coating had a minor impact on the whiteness, tensile strength and breathability of the T/C blend fabrics.

Porous (K0.5Na0.5)0.94Li0.06NbO3-polydimethylsiloxane piezoelectric composites harvesting mechanical energy for efficient decomposition of dye wastewater.

Piezoelectricity as a physical property has received great attention due to its excellently functional applications, especially in piezoelectric catalysis and mechanical energy harvesting. To take full advantage of the functions of piezoelectric materials, (K0.5Na0.5)0.94Li0.06NbO3 (KNN6L) piezoelectric powders were compounded with polydimethylsiloxane (PDMS) in this work. The developed KNN6L-PDMS porous piezoelectric composites with flexible and recyclable characteristics could achieve âˆ¼ 91% degradation rate of Rhodamine B (RhB) dye wastewater under mechanical vibration, and the outstanding piezocatalytic activity was still maintained after repeated decomposition multiple times. Besides, the relationship between piezoelectric potential and piezocatalysis was validated by COMSOL simulations. The content of piezoelectric powders played a positive effect on the magnitude of piezoelectric potential generated by the KNN6L-PDMS porous composites. Moreover, the catalytic mechanism was found to be originated by generation of various reactive oxygen species (mainly •O2- and •OH) in water environment as a result of strong piezoelectric effect by the porous composites. The porous piezoelectric composites with flexible and recyclable characteristics exhibited excellent performance in piezoelectric catalysis which has promising applications in the field of environmental remediation.

The antigenicity of silk-based biomaterials: sources, influential factors and applications.

Silk is an ancient material with essential roles in numerous biomedical applications, such as tissue regeneration and drug delivery, because of its excellent tunable mechanical properties and diverse physical structures. In addition to the necessary functionalities for biomedical applications, another critical factor for materials applied in biology is the appropriate immune interactions with the body. This review focuses on the immune responses of silk-based materials applied in biomedical applications, specifically antigenicity. The factors affecting the antigenicity of silk-based materials are complicated and are related to the composition and structural characteristics of the materials. At the same time, the composition of silk-based materials varies with its species sources, such as silkworms, spiders, honey bees, or engineered recombinant silk. Additionally, different processing methods are used to fabricate different material formats, such as films, hydrogels, scaffolds, particles, and fibers, resulting in different structural characteristics. Furthermore, the resulting body reactions are also different with different degrees of the immune response. Silk protein typically induces a mild immune response, and immunogenicity can play active roles in osteogenesis, angiogenesis, and protection from inflammation. However, there are some rare reports of severe immune responses caused by silk, which can result in an allergic response or tissue necrosis. The source of allergenicity in silk-based materials is currently under-studied and how to regulate and eliminate the overreaction of the immune system is essential for further applications. Overall, the diverse characteristics of silk-based materials mostly show beneficial bioresponses with mild immunogenicity, and the tunable properties make it applicable in immune-related biomedical applications.

Micro-arc oxidation-assisted sol-gel preparation of calcium metaphosphate coatings on magnesium alloys for bone repair.

Calcium phosphate coating is an attractive surface modification strategy for magnesium alloys, since it can increase their corrosion resistance and endow them with osteogenic function simultaneously. Herein, a calcium metaphosphate (CMP) coating was fabricated on magnesium alloy by using sol-gel approach assisted with micro-arc oxidation pre-treatment. Scanning electron microscopy showed that the micro-pores and cracks in micro-arc oxidation inner layer generated during the pre-treatment process were sealed by the grainy sol-gel outer layer. Energy dispersive spectrometry and X-ray diffraction results demonstrated the identity of the coating as CMP. The cross-cut test showed that the adhesion of CMP coating was strong. Applying bare magnesium alloy substrate as a control, the CMP coating surface was rougher and more hydrophilic. The potentiodynamic polarization test demonstrated that the corrosion resistance was significantly improved by using CMP coating. Hydrogen evolution in immersion test further confirmed that the degradation rate was decelerated within 14 days. Moreover, CMP coating facilitated the adhesion speed, spreading area, and focal adhesion formation of bone marrow stem cells. The number of cells in the active proliferating state and proliferated cells present on the CMP coating also increased. Additionally, CMP coating upregulated alkaline phosphatase activity and osteogenic gene expression in cells. In summary, the micro-arc oxidation assisted sol-gel CMP coatings increased the corrosion resistance and promoted the interfacial cell behavior for magnesium alloy implants, which might inform the further development of surface modifications on magnesium alloys for bone related applications.

Electrodeposited Assembly of Additive-Free Silk Fibroin Coating from Pre-Assembled Nanospheres for Drug Delivery.

Electrophoretically deposited (EPD) polymer-based coatings have been extensively reported as reservoirs in medical devices for delivery of therapeutic agents, but control over drug release remains a challenge. Here, a simple but uncommon assembly strategy for EPD polymer coatings was proposed to improve drug release without introducing any additives except the EPD matrix polymer precursor. The added value of the proposed strategy was demonstrated by developing a novel EPD silk fibroin (SF) coating assembled from pre-assembled SF nanospheres for an application model, that is, preventing infections around percutaneous orthopedic implants via local delivery of antibiotics. The EPD mechanism of this nanosphere coating involved oxidation of water near the substrate to neutralize SF nanospheres, resulting in irreversible deposition. The deposition process and mass could be easily controlled using the applied EPD parameters. In comparison with the EPD SF coating assembled in a conventional way (directly obtained from SF molecule solutions), this novel coating had a similar adhesion strength but exhibited a more hydrophobic nanotopography to induce better fibroblastic response. Moreover, the use of nanospheres as building blocks enabled 1.38 and 21 times enhancement on the antibiotic release amount and time (of 95% maximum dug release), respectively, while retaining drug effectiveness and showing undetectable cytotoxicity. This unexpected release kinetics was found attributable to the electrostatic and hydrophobic interactions between the drug and nanospheres and a negligible initial dissolution effect on the nanosphere coating. These results illustrate the promising potential of the pre-assembled strategy on EPD polymer coatings for superior control over drug delivery.

Titanium surfaces characteristics modulate macrophage polarization.

Monocytes/macrophages are one of the first cell types that interact with dental and orthopedic metallic implants, after which these interactions result in a cascade of events that further determine the bone healing performance around implants. This process was recently indicated to be closely dependent on M1/M2 macrophage phenotypes. However, how clinically related physical and chemical implant surface parameters affect macrophage phenotype is incompletely understood. Here, we created and characterized a series of titanium disks with different surface roughness from the submicron to micron level and provided with or without a hydroxyapatite (HA) coating. Human THP-1 derived macrophages were cultured on these different surfaces along with conventional M1 and M2 macrophage controls on glass slides. Macrophage adhesion and polarization were assessed by DNA content, specific cytokine secretion and gene expression profiling, and immunostaining. The data demonstrated that an HA coating rather than roughness remarkably affected macrophage adhesion. Compared to M1 and M2 macrophage controls, different roughness or an HA-coating led to macrophage polarization into a specific surface-associated state. Interestingly, only a narrow range of roughness (Ra = 0.51-1.36 µm; Sa = 0.66-2.91 µm) tended to polarize adherent macrophages toward M2 phenotype by downregulating pro-inflammatory and upregulating anti-inflammatory cytokine secretion, gene expression and surface marker expression. In contrast, the presence of an HA-coating resulted in a hybrid macrophage subtype with both M1 and M2 characteristics. In conclusion, our data demonstrated that physical and chemical surface properties elicit material-activated macrophage polarization and indicate the potential of using physicochemical surface modifications to steer macrophage response and behavior in support of the success of metallic implants.

Porous niobium coatings fabricated with selective laser melting on titanium substrates: Preparation, characterization, and cell behavior.

Nb, an expensive and refractory element with good wear resistance and biocompatibility, is gaining more attention as a new metallic biomaterial. However, the high price of the raw material, as well as the high manufacturing costs because of Nb's strong oxygen affinity and high melting point have limited the widespread use of Nb and its compounds. To overcome these disadvantages, porous Nb coatings of various thicknesses were fabricated on Ti substrate via selective laser melting (SLM), which is a 3D printing technique that uses computer-controlled high-power laser to melt the metal. The morphology and microstructure of the porous Nb coatings, which had pores ranging from 15 to 50 µm in size, were characterized with scanning electron microscopy (SEM). The average hardness of the coating, which was measured with the linear intercept method, was 392±37 HV. In vitro tests of the porous Nb coating which was monitored with SEM, immunofluorescence, and CCK-8 counts of cells, exhibited excellent cell morphology, attachment, and growth. The simulated body fluid test also proved the bioactivity of the Nb coating. Therefore, these new porous Nb coatings could potentially be used for enhanced early biological fixation to bone tissue. In addition, this study has shown that SLM technique could be used to fabricate coatings with individually tailored shapes and/or porosities from group IVB and VB biomedical metals and their alloys on stainless steel, Co-Cr, and other traditional biomedical materials without wasting raw materials.