Protein exerts a critical influence on the degradation behavior of absorbable magnesium (Mg)-based implants. However, the interaction mechanism between protein and a micro-arc oxidation (MAO) coating on Mg alloys remains unclear. Hereby, a MAO coating was fabricated on AZ31 Mg alloy. And its degradation behavior in phosphate buffer saline (PBS) containing bovine serum albumin (BSA) was investigated and compared with that of the uncoated alloy. Surface morphologies and chemical compositions were studied using Field-emission scanning electron microscope (FE-SEM), Fourier transform infrared spectrophotometer (FT-IR) and X-ray diffraction (XRD). The degradation behavior of the bare Mg alloy and its MAO coating was studied through electrochemical and hydrogen evolution tests. Cytotoxicity assay was applied to evaluate the biocompatibility of Mg alloy substrate and MAO coating. Results indicated that the presence of BSA decreased the degradation rate of Mg alloy substrate because BSA (RCH(NH2)COO‾) molecules combined with Mg2+ ions to form (RCH(NH2)COO)2Mg and thus inhibited the dissolution of Mg(OH)2 by impeding the attack of Cl‾ ions. In the case of MAO coated Mg alloy, the adsorption of BSA on MAO coating and the formation of (RCH(NH2)COO)2Mg exhibited a synergistic effect and enhanced the corrosion resistance of the coated alloy significantly. Furthermore, cell bioactive assay suggested that the MAO coating had good viability for MG63 cells due to its high surface area.

Magnesium (Mg) and its alloys, which have good mechanical properties and damping capacities, are considered as potential candidate materials in the industrial field. Nevertheless, fast corrosion is the main obstacle that seriously hinders its wide applications. Surface modification is an available method to avoid the contact between corrosive media and Mg substrates, thus extending the service life of Mg-based materials. Generally, manufacturing a dense and stable coating as physical barriers can effectively inhibit the corrosion of Mg substrates; however, in some complex service environments, physical barrier coating only may not satisfy the long-term service of Mg alloys. In this case, it is very important to endow the coating with suitable functional characteristics, such as superhydrophobic and self-healing properties. In this review, the various surface treatments reported are presented first, followed by the methods employed for developing superhydrophobic surfaces with micro/nanostructuring, and an overview of the various advanced self-healing coatings, devolved on Mg alloys in the past decade, is further summarized. The corresponding preparation strategies and protection mechanisms of functional coatings are further discussed. A potential research direction is also briefly proposed to help guide functional strategies and inspire further innovations. It is hoped that the summary of this paper will be helpful to the surface modification of Mg alloys and promote the further development of this emerging research field.

Synergistic combination therapy by integrating chemotherapeutics and chemosensitizers into nanoparticles has demonstrated great potential to reduce side effects, overcome multidrug resistance (MDR), and thus improve therapeutic efficacy. However, with regard to the nanocarriers for multidrug codelivery, it remains a strong challenge to maintain design simplicity, while incorporating the desirable multifunctionalities, such as coloaded high payloads, targeted delivery, hemodynamic stability, and also to ensure low drug leakage before reaching the tumor site, but simultaneously the corelease of drugs in the same cancer cell. Herein, we developed a facile modular coassembly approach to construct an all-in-one multifunctional multidrug delivery system for the synergistic codelivery of doxorubicin (DOX, chemotherapeutic agent) and curcumin (CUR, MDR modulator). The acid-cleavable PEGylated polymeric prodrug (DOX-h-PCEC), tumor cell-specific targeting peptide (CRGDK-PEG-PCL), and natural chemosensitizer (CUR) were ratiometrically assembled into in one single nanocarrier (CUR/DOX-h-PCEC@CRGDK NPs). The resulting CUR/DOX-h-PCEC@CRGDK NPs exhibited several desirable characteristics, such as efficient and ratiometric drug loading, high hemodynamic stability and low drug leakage, tumor intracellular acid-triggered cleavage, and subsequent intracellular simultaneous drug corelease, which are expected to maximize a synergistic effect of chemotherapy and chemosensitization. Collectively, the multifunctional nanocarrier is feasible for the creation of a robust nanoplatform for targeted multidrug codelivery and efficient MDR modulation.