RGD Nanoarrays with Nanospacing Gradient Selectively Induce Orientation and Directed Migration of Endothelial and Smooth Muscle Cells.

Directed migration of cells through cell-surface interactions is a paramount prerequisite in biomaterial-induced tissue regeneration. However, whether and how the nanoscale spatial gradient of adhesion molecules on a material surface can induce directed migration of cells is not sufficiently known. Herein, we employed block copolymer micelle nanolithography to prepare gold nanoarrays with a nanospacing gradient, which were prepared by continuously changing the dipping velocity. Then, a self-assembly monolayer technique was applied to graft arginine-glycine-aspartate (RGD) peptides on the nanodots and poly(ethylene glycol) (PEG) on the glass background. Since RGD can trigger specific cell adhesion via conjugating with integrin (its receptor in the cell membrane) and PEG can resist protein adsorption and nonspecific cell adhesion, a nanopattern with cell-adhesion contrast and a gradient of RGD nanospacing was eventually prepared. In vitro cell behaviors were examined using endothelial cells (ECs) and smooth muscle cells (SMCs) as a demonstration. We found that SMCs exhibited significant orientation and directed migration along the nanospacing gradient, while ECs exhibited only a weak spontaneously anisotropic migration. The gradient response was also dependent upon the RGD nanospacing ranges, namely, the start and end nanospacings under a given distance and gradient. The different responses of these two cell types to the RGD nanospacing gradient provide new insights for designing cell-selective nanomaterials potentially used in cell screening, wound healing, etc.

Enlargement, Reduction, and Even Reversal of Relative Migration Speeds of Endothelial and Smooth Muscle Cells on Biomaterials Simply by Adjusting RGD Nanospacing.

Although many tissue regeneration processes after biomaterial implantation are related to migrations of multiple cell types on material surfaces, available tools to adjust relative migration speeds are very limited. Herein, we put forward a nanomaterial strategy to employ surface modification with arginine-glycine-aspartate (RGD) nanoarrays to tune in vitro cell migration using endothelial cells (ECs) and smooth muscle cells (SMCs) as demonstrated cell types. We found that migrations of both cell types exhibited a nonmonotonic trend with the increase of RGD nanospacing, yet with different peaks-74 nm for SMCs but 95 nm for ECs. The varied sensitivities afford a facile way to regulate the relative migration speeds. Although ECs migrated at a speed similar to SMCs on a non-nano surface, the migration of ECs could be controlled to be significantly faster or slower than SMCs simply by adjusting the RGD nanospacing. This study suggests a potential application of surface modification of biomaterials on a nanoscale level.

Durable super-hydrophobic PDMS@SiO2@WS2 sponge for efficient oil/water separation in complex marine environment.

The robust and eco-friendly super-hydrophobic sponge with remarkable performances has been potential adsorption material for the treatment of offshore oil spills. In this work, the durable PDMS@SiO2@WS2 sponge was fabricated via a green and facile one-step dipping method. The mixed tungsten disulfide (WS2) microparticles and hydrophobic SiO2 nanoparticles were immobilized on the sponge by non-toxic polydimethylsiloxane (PDMS) glue tier, which featured the hierarchical structure and extreme water repellency with the water contact angle of 158.8 ± 1.4°. The obtained PDMS@SiO2@WS2 sponge exhibits high oil adsorption capacity with 12-112 times of its own weight, and oil/water selectivity with separation efficiency over 99.85%. Notably, when subjected to the complex marine environment including high temperature, corrosive condition, insolation, and strong wind and waves, the modified sponge can maintain sable super-hydrophobicity with water contact angle over 150°. Moreover, it possesses superior mechanical stability for sustainable reusability and oil recovery. The sponge fabricated by non-toxic modifiers along with its sable super-hydrophobicity in complex marine environment makes it a potential material for practical applications.

Preparation and characterization of ethyl cellulose film modified with capsaicin.

Pure ethyl cellulose film cannot extend the shelf life of food, and adding capsaicin as an antibacterial agent can inhibit the activity of microorganisms on the surface of the film. The main purpose of this work is to study the properties and specific performance of the film formed by adding capsaicin to ethyl cellulose system. Importantly, the transparent, soft, and stretchable ethyl cellulose-capsaicin composite membrane (EC-Cap) is generally easy to produce and is environmentally friendly. It is the first successful preparation by a casting method. It is worth noting that the FTIR analysis of the film shows that there may be an interaction between the phenolic hydroxyl group in Cap and the hydroxyl group in EC, which means that Cap has successfully participated in the film formation system. Therefore, the cap-containing film not only exhibits a low water absorption, when the cap is appropriate, the elongation at break of the film reaches a maximum of 61.34 % ± 1.37 %. Compared with pure EC membrane, EC-Cap membrane has greater antibacterial activity than pure EC membrane. The practical application of EC-Cap films in the protection of bell peppers has shown positive results, which makes it possible to apply these films to food packaging.

Cell migration regulated by RGD nanospacing and enhanced under moderate cell adhesion on biomaterials.

While nanoscale modification of a biomaterial surface is known to influence various cell behaviors, it is unclear whether there is an optimal nanospacing of a bioactive ligand with respect to cell migration. Herein, we investigated the effects of nanospacing of arginine-glycine-aspartate (RGD) peptide on cell migration and its relation to cell adhesion. To this end, we prepared RGD nanopatterns with varied nanospacings (31-125 nm) against the nonfouling background of poly(ethylene glycol), and employed human umbilical vein endothelial cells (HUVECs) to examine cell behaviors on the nanopatterned surfaces. While HUVECs adhered well on surfaces of RGD nanospacing less than 70 nm and exhibited a monotonic decrease of adhesion with the increase of RGD nanospacing, cell migration exhibited a nonmonotonic change with the ligand nanospacing: the maximum migration velocity was observed around 90 nm of nanospacing, and slow or very slow migration occurred in the cases of small or large RGD nanospacings. Therefore, moderate cell adhesion is beneficial for fast cell migration. Further molecular biology studies revealed that attenuated cell adhesion and activated dynamic actin rearrangement accounted for the promotion of cell migration, and the genes of small G proteins such as Cdc42 were upregulated correspondingly. The present study sheds new light on cell migration and its relation to cell adhesion, and paves a way for designing biomaterials for applications in regenerative medicine.

Formate-assisted analytical pyrolysis of kraft lignin to phenols.

The effect of sodium formate (SF), calcium formate (CF) and nickel formate (NF) as additives on analytical pyrolysis performance of kraft lignin was conducted. The results showed that these formates promoted the releasing of volatiles, leading to the rapid degradation of kraft lignin. High relative content of monophenols (53.77%), especially of guaiacol (23.65%), were achieved from the pyrolysis of pure lignin. The relative content of guaiacol was dramatically decreased after the adding of formates in kraft lignin. The relative content of polyphenols such as 3-methylcatechol and 4-methylcatechol reached to 16.97%, 16.23% and 21.95% with the formates of SF, CF and NF, respectively. The NF showed the highest selectivity of polyphenols and hydrocarbons. The increase of polyphenols and hydrocarbons from NF was the synergetic effect of the hydrogen radical reaction from the formic functional groups under the catalysis of Ni and/or NiO produced from the NF pyrolysis process.

Optimization of polyhydroxybutyrate (PHB) production by excess activated sludge and microbial community analysis.

In this study, a high value-added and biodegradable thermoplastic, polyhydroxybutyrate (PHB), was produced by excess activated sludge. The effects of the nutritional condition, aeration mode, sodium acetate concentration and initial pH value on PHB accumulation in the activated sludge were investigated. The maximum PHB content and PHB yield of 67.0% (dry cell weight) and 0.740gCODgCOD(-1) (COD: chemical oxygen demand), respectively, were attained by the sludge in the presence of 6.0gL(-1) sodium acetate, with an initial pH value of 7.0 and intermittent aeration. The analysis of the polymerase chain reaction (PCR)-denaturing gradient-gel-electrophoresis (DGGE) sequencing indicated that the microbial community of the sludge was significantly different during the process of PHB accumulation. Three PHB-accumulating microorganisms, which were affiliated with the Thauera, Dechloromonas and Competibacter lineages, were found in the excess activated sludge under different operating conditions for PHB accumulation.