Particles that modify delivery characteristics are a focus of drug-loading research. Hydroxyapatite particles (HAPs) have excellent biocompatibility, shape controllability, and high adsorption, making them a potential candidate for drug-delivery carriers. However, there are still some defects in the current methods used to prepare HAPs. In order to avoid agglomeration and improve the drug-loading properties of HAPs, the present study provides a novel triethylamine (TEA)-capped coprecipitation template method to prepare HAPs at room temperature. In addition, pure water and anhydrous ethanol were used as solvents to investigate the capping effect of the small-molecule capping agent TEA during the synthesis of HAPs. The results showed that the HAPs prepared in the TEA ethanol system had a smaller particle size (150–250 nm), better dispersion and higher crystallinity. The results were significantly different from those of the conventional preparation methods without TEA. However, the hydroxyapatite crystal would agglomerate to a certain extent after being stored for a period of time, forming micro/nano-sized agglomerates of nanocrystals. FITR analysis and SEM observation showed that the capping effect of TEA promoted the formation of a smaller template and dispersed HAPs were quickly formed by dissolution and reprecipitation processes. The drug-loading experiments showed that the HAPs prepared in the TEA ethanol system had high drug-loading capacity (239.8 ± 13.4 mg·g⁻¹) as well as an improved drug-release profile demonstrated in the drug-release experiment. The larger specific surface area associated with the smaller particle size was beneficial to the adsorption of drugs. After drying at 60 °C, TEA was evaporated from the HAPs which agglomerated into larger micron particles with more drug encapsulated. Thus, the effect of a sustained release was achieved. In the present research, a novel approach was developed by using triethylamine as the capping agent to prepare micro/nano-sized agglomerates of HAP nanocrystals with improved drug loading, which is predicted to have potential application in drug delivery.

Polymer coatings are commonly used to protect carbon steels from corrosion but they are susceptible to weathering and many of them have environmental concerns. Therefore, we studied the possibility of an environmentally favorable inorganic magnesium phosphate cement (MPC) coating for protecting mild steel. A formulation suitable for coating steel was developed by compositional modification [i.e., incremental replacement of dead-burned magnesia (MgO) with magnesium hydroxide (Mg(OH)₂)] to a road-repair MPC. This modification yielded an acceptable working time and prevented pore formation at the coating-steel interface. Corrosion monitoring by linear polarization and electrochemical impedance spectroscopy for 14 days found that, the MPC coating substantially increased the linear polarization resistance (R_p) [e.g., day 1: (8.2 ± 1.7) × 10³ (nadir value) vs. 495 ± 55 Ω cm⁻²] and charge transfer resistance (R_ct) (e.g., day 1: 9.3 × 10³ vs. 3.8 × 10² Ω cm⁻²). The coated steel underwent neutral sodium chloride (NaCl) salt spray for 2400 h without visible rusting. Immersion for 24 h in liquids simulating the pore fluid indicated that, passivation by the excess MgO in the coating was a major contributor to its anti-corrosive property. Tafel polarization in the liquids found that, corrosion current density (I_corr) followed the rank: 3.5% NaCl solution (6.0 µA cm⁻²) > 3.5% NaCl solution containing MgO (3.6 µA cm⁻²) > 3.5% NaCl solution containing fragmented MPC (1.7 µA cm⁻²), suggesting that a physical barrier effect and dissolved phosphate ions improved its protection. This study shows that, MPC coating is a promising durable and environmentally favorable anti-corrosive material for protecting steel structures in some applications.

Implant-related infection (IRI) is a major problem in orthopedics. Copper (Cu) is an essential trace element with strong bactericidal activity and, thus, presents potential for reducing IRI. The present study explored a straightforward strategy for releasing Cu²⁺ from titanium (Ti) implants, and we conducted a preliminary study to assess the feasibility of this approach in clinical translation. Polylactic acid (PLA) coatings containing different concentrations of copper ions were prepared on Ti discs. The antibacterial activity and biocompatibility of the copper ion-incorporated Ti implants were evaluated using Staphylococcus aureus (S. aureus), bone marrow mesenchymal stem cells (BMSCs) and animal models. In vitro, the coatings produced burst release of Cu²⁺ in 12 h, and inhibited S. aureus growth in a dose-dependent manner. The coatings prepared from PLA solutions containing 0.5 or 1.0 mg/mL reduced the viability and osteogenic differentiation of BMSCs, but these effects were negated after the coatings were immersed in culture medium for 6 h. Four weeks after implantation, the Cu-free K-wires challenged with S. aureus had persistent infection and inferior fracture healing to the other three groups, while Cu-coated wires had no evidence of infection. Furthermore, the Cu-coated wires placed in rabbits without S. aureus challenge showed superior fracture healing to the other three groups. These results suggest that PLA coatings containing Cu²⁺ may be an effective design for reducing IRI without adversely affecting adjacent bone healing.

Titanium (Ti) dental implants face risks of early failure due to bacterial adhesion and biofilm formation. It is thus necessary to endow the implant surface with antibacterial ability. In this study, magnesium oxide (MgO) coatings were prepared on Ti by combining micro-arc oxidation (MAO) and electrophoretic deposition (EPD). The MgO nanoparticles homogeneously deposited on the microporous surface of MAO-treated Ti, yielding increasing coverage with the EPD time increased to 15 to 60 s. After co-culture with Porphyromonas gingivalis (P. gingivalis) for 24 h, 48 h, and 72 h, the coatings produced antibacterial rates of 4–53 %, 27–71 %, and 39–79 %, respectively, in a dose-dependent manner. Overall, EPD for 45 s offered satisfactory comprehensive performance, with an antibacterial rate 79 % at 72 h and a relative cell viability 85 % at 5 d. Electron and fluorescence microscopies revealed that, both the density of adherent bacterial adhesion on the surface and the proportion of viable bacteria decreased with the EPD time. The morphology of cells on the surface of each group was intact and there was no significant difference among the groups. These results show that, the MgO coating deposited on MAO-treated Ti by EPD had reasonably good in vitro antibacterial properties and cytocompatibility.

A Mg-incorporating Ta coating was deposited on a 3D-printed Ti6Al4V scaffold using a sol–gel method. The coating enhanced osteogenic differentiation of BMSCs and bone ingrowth in vivo.