Construction of Magnesium Phosphate Chemical Conversion Coatings with Different Microstructures on Titanium to Enhance Osteogenesis and Angiogenesis.

Titanium (Ti) and its alloys are widely used as hard tissue substitutes in dentistry and orthopedics, but their low bioactivity leads to undesirable osseointegration defects in the early osteogenic phase. Surface modification is an important approach to overcome these problems. In the present study, novel magnesium phosphate (MgP) coatings with controllable structures were fabricated on the surface of Ti using the phosphate chemical conversion (PCC) method. The effects of the microstructure on the physicochemical and biological properties of the coatings on Ti were researched. The results indicated that accelerators in PCC solution were important factors affecting the microstructure and properties of the MgP coatings. In addition, the coated Ti exhibited excellent hydrophilicity, high bonding strength, and good corrosion resistance. Moreover, the biological results showed that the MgP coatings could improve the spread, proliferation, and osteogenic differentiation of mouse osteoblast cells (MC3T3-E1) and vascular differentiation of human umbilical vein endothelial cells (HUVECs), indicating that the coated Ti samples had a great effect on promoting osteogenesis and angiogenesis. Overall, this study provided a new research idea for the surface modification of conventional Ti to enhance osteogenesis and angiogenesis in different bone types for potential biomedical applications.

Effect of surfactants on the transport of polyethylene and polypropylene microplastics in porous media.

The transport of microplastics in porous media is attracting increasing attention. However, to date, research is limited to polystyrene microplastics. Meanwhile, surfactants can promote solid dispersion to form a stable suspension, possibly allowing microplastics to migrate when attached to a surfactant, which would increase the scope and degree of microplastic pollution, further endangering human health and the stability of the ecological environment. Therefore, in this study, the transport behavior of microplastics in porous media was explored in the presence of surfactants. Herein, polyethylene (PE) and polypropylene (PP) were evaluated while dispersed by two ionic surfactants: cationic surfactant-cetyltrimethylammonium bromide (CTAB) and anionic surfactant-sodium dodecylbenzenesulfonate (SDBS). The influence of different factors (surfactant concentration, ionic strength, pH, flow rate, and multivalent cations) on the transport of microplastics in porous media was explored via quartz sand packed-column experiments. Our experimental results show that the transport abilities of PE and PP increased with increasing surfactant concentration when the surfactant concentration was less than the critical micelle concentration (CMC). In the presence of CTAB and SDBS, physicochemical factors had different effects on the transport of microplastics mainly by controlling Zeta potential, advection diffusion and CMC. The mobility of PE and PP decreased with increasing ionic strength, cation valence and pH, and decreasing flow rate. However, the mobility of PE and PP under CTAB is much greater than that of PE and PP under SDBS, because quartz sand can absorb more CTAB molecules through electrostatic attraction to weaken the collision between microplastics and quartz sand. Further, the transport ability of PP was greater than that of PE under all conditions considered. Notably, the Extended-Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory formed by adding osmotic, elastic, and hydrophobic force could well described the migration behavior of microplastics in CTAB and SDBS well. This research highlights that surfactant has a significant impact on the transport ability of microplastics, and provides a comprehensive understanding of the migration and fate behaviors of microplastics affected by surfactants, which is necessary to prevent and reduce the environmental hazards of microplastics.

The transport of graphitic carbon nitride in saturated porous media: Effect of hydrodynamic and solution chemistry.

Understanding transport behavior of graphitic carbon nitride (g-C3N4) in porous media plays an important role in preventing its possible causing the underground environmental problems. The transport behavior of g-C3N4 in porous media were investigated by packed column experiments at different flow rates, ionic strengths (ISs), pHs and multivalent cations. The experimental results showed that the transport ability of g-C3N4 decreased with the IS increasing, and most of the g-C3N4 was retained in the sand column for the IS greater than 0.0001 M. The flow rate had little effect on the transport behavior of g-C3N4, and the recovery of g-C3N4 increased slightly with increasing flow rate. In addition, the migration ability of g-C3N4 under acidic conditions was drastically reduced compared with neutral alkaline conditions. Moreover, it was found that 1.51%, 30.33%, 34.91%, and 60.54% of g-C3N4 was retained in the column when g-C3N4 was leached through the quartz sand column at Al3+, Ca2+, Mg2+, and K+, which was consistent with the Schulze-Hardy rule. Finally, FTIR spectrum showed that the infrared absorption peak of the g-C3N4 mixed quartz sand were shifted to certain degrees under different conditions, which confirmed that hydrogen bond was formed in the transport of carbon nitride with the quartz sand surface. This study provides a new perspective on the role of hydrogen bond in the transport and fate of nanomaterials.

Co-transport of Pb(II) and oxygen-content-controllable graphene oxide from electron-beam-irradiated graphite in saturated porous media.

It is essential to investigate the role of the surface oxygen content of graphene oxide (GO) in transport processes. In this study, GO was prepared using flake graphite with different radiation doses. The effects of the flow rate and ionic strength (IS) on the migration and co-transport of GO and Pb(II) ions were investigated via laboratory packed-column experiments. The experimental results showed that the mobility of GO in saturated porous media decreased with increasing flow rate. Further, the mobility of GO with a radiation dose of 18 kGy was lower than that of GOs with other radiation doses for an IS below 0.01 M. Regarding the co-transport of irradiated GO and Pb(II) in porous media, the greater the radiation dose, the stronger was the ability of GO to promote Pb(II) transport. The surface oxygen content promoted the ability of GO to remove Pb(II). However, radiation doses exceeding a certain range inhibited the release of Pb(II). The transport of GO in saturated porous media was successfully simulated with the advection-dispersion-reaction (ADR) equation. This study is expected to provide a new perspective on the potential risks of GO due to surface changes during its transport in the environment.