Surface modification of biodegradable magnesium alloy with poly (L-lactic acid) and sulfonated hyaluronic acid nanoparticles for cardiovascular application.

Magnesium (Mg) and its alloys have attracted extensive attention of researchers in the field of cardiovascular implants due to their good mechanical properties and biosafety. Constructing a multifunctional hybrid coating seems to be an effective strategy to address the insufficient endothelialization and poor corrosion resistance of Mg alloy vascular stents. In this study, a dense layer of magnesium fluoride (MgF2) was prepared on the surface of Mg alloy aiming at better corrosion resistance; Thereafter, sulfonated hyaluronic acid (S-HA) was made into small sized nanoparticles (NP) which were deposited on the MgF2 surface by self-assembly method, followed with poly-L-lactic acid (PLLA) coating preparation by one-step pulling method. The blood and cell tests showed that the composite coating had good blood compatibility, pro-endothelial, anti-hyperplasia and anti-inflammatory functions. Compared to current clinical PLLA@ Rapamycin coating, our PLLA/NP@S-HA coating showed better functions of promoting endothelial cells growth. These results strongly furnished a promising and feasible strategy for the surface modification of Mg-based degradable cardiovascular stents.

Preparation of Fluorescent Carbon Dots Composites and Their Potential Applications in Biomedicine and Drug Delivery-A Review.

Carbon dots (CDs), a new member of carbon nanostructures, rely on surface modification and functionalization for their good fluorescence phosphorescence and excellent physical and chemical properties, including small size (<10 nm), high chemical stability, biocompatibility, non-toxicity, low cost, and easy synthesis. In the field of medical research on cancer (IARC), CDs, a new material with unique optical properties as a photosensitizer, are being applied to heating local apoptosis induction of cancer cells. In addition, imaging tools can also be combined with a drug to form the nanometer complex compound, the imaging guidance for multi-function dosage, so as to improve the efficiency of drug delivery, which also plays a big role in genetic diagnosis. This paper mainly includes three parts: The first part briefly introduces the synthesis and preparation of carbon dots, and summarizes the advantages and disadvantages of different preparation methods; The second part introduces the preparation methods of carbon dot composites. Finally, the application status of carbon dot composites in biomedicine, cancer theranostics, drug delivery, electrochemistry, and photocatalysis is summarized.

Application of 3D Printing Technology in Bone Tissue Engineering: A Review.

Clinically, the treatment of bone defects remains a significant challenge, as it requires autogenous bone grafts or bone graft substitutes. However, the existing biomaterials often fail to meet the clinical requirements in terms of structural support, bone induction, and controllable biodegradability. In the treatment of bone defects, 3D porous scaffolds have attracted much attention in the orthopedic field. In terms of appearance and microstructure, complex bone scaffolds created by 3D printing technology are similar to human bone. On this basis, the combination of active substances, including cells and growth factors, is more conducive to bone tissue reconstruction, which is of great significance for the personalized treatment of bone defects. With the continuous development of 3D printing technology, it has been widely used in bone defect repair as well as diagnosis and rehabilitation, creating an emerging industry with excellent market potential. Meanwhile, the diverse combination of 3D printing technology with multi-disciplinary fields, such as tissue engineering, digital medicine, and materials science, has made 3D printing products with good biocompatibility, excellent osteoinductive capacity, and stable mechanical properties. In the clinical application of the repair of bone defects, various biological materials and 3D printing methods have emerged to make patient-specific bioactive scaffolds. The microstructure of 3D printed scaffolds can meet the complex needs of bone defect repair and support the personalized treatment of patients. Some of the new materials and technologies that emerged from the 3D printing industry's advent in the past decade successfully translated into clinical practice. In this article, we first introduced the development and application of different types of materials that were used in 3D bioprinting, including metal, ceramic materials, polymer materials, composite materials, and cell tissue. The combined application of 3D bioprinting and other manufacturing methods used for bone tissue engineering are also discussed in this article. Finally, we discussed the bottleneck of 3D bioprinting technique and forecasted its research orientation and prospect.

Fabrication and characterization of biodegradable Mg-Zn-Y-Nd-Ag alloy: Microstructure, mechanical properties, corrosion behavior and antibacterial activities.

Magnesium (Mg), a potential biodegradable material, has drawn wide attention in the bone reconstruction field. However, Mg alloys, served as the bone graft substitution, remain a clinical challenge, the antibacterial activity of which is required to be enhanced. Here, we prepared biodegradable magnesium Mg-Zn-Y-Nd-Ag and then had it been further densified by extruding. The microstructure evolution of the as-cast and as-extruded Mg- Zn-Y-Nd-Ag was characterized using optical microscope and X-ray diffraction analyses (XRD). The results showed that the microstructure of the as-cast alloys was mainly dendrites, between which, the second phase was mainly distributed; with the increase of Ag additions, grain structure was further refined as well as the increase of amount of the second phase. After the extrusion, the grains were further refined. Microhardness tests indicated that both of the increase of Ag content and the extrusion process improved the microhardness of the alloys, specially the later. A systematic investigation of the in vivo antibacterial capability of Staphylococcus aurous and Escherichia coli was performed, and the results of which indicated that all Mg-Zn-Y-N-xAg (x = 0.2, 0.4, 0.6, 0.8) alloys exhibited certain antibacterial property, which would increased with the increase of Ag content. Taken all together, the antimicrobial property of the as-extruded alloy containing 0.4 wt% Ag exhibited the relatively better antimicrobial properties and mechanical property with the relatively small loss in corrosion resistance, which suggested the potential utility of as-extruded Mg-Zn-Y-N-0.4Ag in treating orthopedic infections.

Characterization and corrosion property of nano-rod-like HA on fluoride coating supported on Mg-Zn-Ca alloy.

The poor corrosion resistance of biodegradable magnesium alloys is the dominant factor that limits their clinical application. In this study, to deal with this challenge, fluoride coating was prepared on Mg-Zn-Ca alloy as the inner coating and then hydroxyapatite (HA) coating as the outer coating was deposited on fluoride coating by pulse reverse current electrodeposition (PRC-HA/MgF2). As a comparative study, the microstructure and corrosion properties of the composite coating with the outer coating fabricated by traditional constant current electrodeposition (TED-HA/MgF2) were also investigated. Scanning electron microscopy (SEM) images of the coatings show that the morphology of PRC-HA/MgF2 coating is dense and uniform, and presents nano-rod-like structure. Compared with that of TED-HA/MgF2, the corrosion current density of Mg alloy coated with PRC-HA/MgF2 coatings decreases from 5.72 × 10-5 A/cm2 to 4.32 × 10-7 A/cm2, and the corrosion resistance increases by almost two orders of magnitude. In immersion tests, samples coated with PRC-HA/MgF2 coating always show the lowest hydrogen evolution amount, and could induce deposition of the hexagonal structure-apatite on the surface rapidly. The results show that the corrosion resistance and the bioactivity of the coatings have been improved by adopting double-pulse current mode in the process of preparing HA on fluoride coating, and the PRC-HA/MgF2 coating is worth of further investigation.