Collagen Type I-Gelatin Methacryloyl Composites: Mimicking the Tumor Microenvironment.

Therapeutic drugs can penetrate tissues by diffusion and advection. In a healthy tissue, the interstitial fluid is composed of an influx of nutrients and oxygen from blood vessels. In the case of cancerous tissue, the interstitial fluid is poorly drained because of the lack of lymphatic vasculature, resulting in an increase in interstitial pressure. Furthermore, cancer cells invade healthy tissue by pressing and pushing the surrounding environment, creating an increase in pressure inside the tumor area. This results in a large differential pressure between the tumor and the healthy tissue, leading to an increase in extracellular matrix (ECM) stiffness. Because of high interstitial pressure in addition to matrix stiffening, penetration and distribution of systemic therapies are limited to diffusion, decreasing the efficacy of cancer treatment. This work reports on the development of a microfluidic system that mimics in vitro healthy and cancerous microenvironments using collagen I and gelatin methacryloyl (GelMA) composite hydrogels. The microfluidic device developed here contains a simplistic design with a central chamber and two lateral channels. In the central chamber, hydrogel composites were used to mimic the ECM, whereas lateral channels simulated capillary vessels. The transport of fluorescein sodium salt and fluorescently labeled gold nanoparticles from capillary-mimicking channels through the ECM-mimicking hydrogel was explored by tracking fluorescence. By tuning the hydrogel composition and concentration, the impact of the tumor microenvironment properties on the transport of those species was evaluated. In addition, breast cancer MCF-7 cells were embedded in the hydrogel composites, displaying the formation of 3D clusters with high viability and, consequently, the development of an in vitro tumor model.

Electrochemical oxidation of 4-chlorophenol for wastewater treatment using highly active UV treated TiO2 nanotubes.

In the present work, we report on a facile UV treatment approach for enhancing the electrocatalytic activity of TiO2 nanotubes. The TiO2 nanotubes were prepared using an anodization oxidation method by applying a voltage of 40 V for 8 h in a DMSO + 2% HF solution, and further treated under UV light irradiation. Compared with Pt and untreated TiO2 nanotubes, the UV treated electrode exhibited a superior electrocatalytic activity toward the oxidation of 4-chlorophenol (4-ClPh). The effects of current density and temperature on the electrochemical oxidation of the 4-ClPh were also systematically investigated. The high electrocatalytic activity of the UV treated TiO2 nanotubes was further confirmed by the electrochemical oxidation of other persistent organic pollutants including phenol, 2-, 3-, 4-nitrophenol, and 4-aminophenol. The total organic carbon (TOC) analysis revealed that over 90% 4-ClPh was removed when the UV treated TiO2 electrode was employed and the rate constant was 16 times faster than that of the untreated TiO2 electrode; whereas only 60% 4-ClPh was eliminated at the Pt electrode under the same conditions. This dramatically improved electrocatalytic activity might be attributed to the enhanced donor density, conductivity, and high overpotential for oxygen evolution. Our results demonstrated that the application of the UV treatment to the TiO2 nanotubes enhanced their electrochemical activity and energy consumption efficiency significantly, which is highly desirable for the abatement of persistent organic pollutants.

Efficient bacterial disinfection based on an integrated nanoporous titanium dioxide and ruthenium oxide bifunctional approach.

The increasing lack of drinking water around the globe is of great concern. Although UV irradiation, photocatalysis, and electrocatalysis for bacterial disinfection have been widely explored, the synergistic kinetics involved in these strategies have not been reported to date. Herein, we report on an efficient and cost-effective strategy for the remediation of a model bacterium (E. coli), through the integration of photochemistry and electrochemistry based on a bifunctional electrode, which utilizes titanium (Ti) as the substrate, nanoporous titanium dioxide (TiO2) as a photocatalyst, and ruthenium oxide (RuO2) nanoparticles as an electrocatalyst. The nanoporous TiO2 was grown directly onto a Ti substrate via a three-step anodization process, and its photocatalytic activity was significantly enhanced by a facile electrochemical treatment. A high disinfection rate at 0.62 min-1, with >99.999% bacterial removal within 20 min was achieved using the novel TiO2/Ti/RuO2 bifunctional electrode. Complete bacterial disinfection was attained within 30 min as assessed by a spread plate method. Bacterial survival strategies, including a viable but non-culturable state of the bacteria, were also investigated during the bifunctional treatment process. The novel strategy demonstrated in this study has strong potential to be utilized for water purification and wastewater treatment as an advanced environmentally compatible technology.

Significant enhancement in the photocatalytic activity of N, W co-doped TiO2 nanomaterials for promising environmental applications.

In this work, a mesoporous N, W co-doped TiO(2) photocatalyst was synthesized via a one-step solution combustion method, which utilized urea as the nitrogen source and sodium tungstate as the tungsten source. The photocatalytic activity of the N, W co-doped TiO(2) photocatalyst was significantly enhanced by a facile UV pretreatment approach and was evaluated by measuring the rate of photodegradation of Rhodamine B under both UV and visible (λ > 420) light. Following the UV pretreatment, the UV photocatalytic activity of the N, W co-doped TiO(2) was doubled. In terms of visible light activity, the UV pretreatment resulted in an extraordinary >12 fold improvement. In order to gain insight into this substantial enhancement, the N, W co-doped TiO(2) photocatalysts were studied using x-ray diffraction, transmission electron microscopy, N(2) physisorption, UV-vis absorbance spectroscopy and x-ray photoelectron spectroscopy prior to and following the UV pretreatment. Our experimental results have revealed that this significant augmentation of photocatalytic activity may be attributed to several synergetic factors, including increase of the specific surface area, reduction of the band gap energy and the removal of carbon impurities.

Quantitative structure-reactivity study of electrochemical oxidation of phenolic compounds at the SnO2-based electrode.

In the present study, the electrochemical oxidation of 22 phenolic compounds was systemically examined at the RuO(2)-SnO(2)-Sb(2)O(5) electrode to elucidate the inherent structure-reactivity correlation. The oxidation process was monitored in situ by UV-vis spectroscopy. A variety of substituents (e.g., -CH(3), -NH(2), -Cl, -OH, -COOH, -NO(2), -CHO) were employed in order to cover various possible electronic effects. Our experimental results revealed that the relationship between the Hammett constant and rate constant for the electrochemical oxidation of phenolic compounds at the RuO(2)-SnO(2)-Sb(2)O(5) electrode was different from the results obtained at a platinum electrode. The substituted phenols with electron-withdrawing groups were electrochemically oxidized more rapidly than those with electron-donating groups. To decipher the effects of physiochemical properties on the electrochemical reactivity of phenolic compounds, 140 molecular descriptors were calculated and assessed for each phenolic compound; a quantitative structure property relationship (QSPR) model was developed. Correlations between the rate constants and quantum properties of the phenolic compounds were achieved using partial least-squares (PLS) analysis. The most crucial quantum descriptors responsible for the electrochemical reactivity of phenolic compounds were determined to be E(HOMO), chemical potential, total dipole, quadrupoles, subgraph counts, relative positive charged surface area, and pK(a). The proposed QSPR model was based on the quantum descriptors derived from the whole molecule, providing lucid explanation and effective prediction of the electrochemical reactivity of various phenolic compounds.