In vitro study of the inflammatory cells response to biodegradable Mg-based alloy extract

<div><p>Biodegradable Mg-based alloys have shown great potential as bone fixation devices or vascular stents. As implant biomaterials, the foreign body reaction (FBR) is an important issue to be studied, where the inflammatory cells play a key role. Here, we used two inflammatory cell lines i.e. THP-1 cells and THP-1 macrophages, to evaluate the effect of Mg–Nd–Zn–Zr alloy (denoted as JDBM) extracts on cell viability, death modes, cell cycle, phagocytosis, differentiation, migration and inflammatory response. The results showed that high-concentration extract induced necrosis and complete damage of cell function. For middle-concentration extract, cell apoptosis and partially impaired cell function were observed. TNF-α expression of macrophages was up-regulated by co-culture with extract in 20% concentration, but was down-regulated in the same concentration in the presence of LPS stimulation. Interestingly, the production of TNF-α decreased when macrophages were cultured in middle and high concentration extracts independent of LPS. Cell viability was also negatively affected by magnesium ions in JDBM extracts, which was a potential factor affecting cell function. Our results provide new information about the impact of Mg alloy extracts on phenotype of immune cells and the potential mechanism, which should be taken into account prior to clinical applications.</p></div

The impact of JDBM extracts on the migration function of macrophages.

<p>(A) A representative result of scratch assay after treated with JDBM extracts or RPMI 1640 (ctr) at 0, 24, 48h, respectively. Scale bar = 100μm. (B) statistical results of scratch assay. ^#<i>P</i> < 0.05 vs 0hr related group*<i>P</i> < 0.05 vs 24hr related group.</p

The physicochemical characteristics of JDBM extract.

<p>The physicochemical characteristics of JDBM extract.</p

The impact JDBM extract on cell cycle of THP-1 cells.

<p>(A) A representative result of cell cycle after treatment of RPMI 1640 medium (Ctr) or JDBM extract for 72h. (B) Statistical results of cell cycle of THP-1 cells in extract culture for 72h. (C) The expression of cell cycle related genes of THP-1 cell treated with indicated for 24h *<i>P</i> < 0.05 vs ctr.</p

The impact of JDBM extracts on the phagocytic function of macrophages.

<p>(A) A representative result of cell phagocytic performance with beads for 4h after induced by JDBM extracts or RPMI 1640 (ctr) for 24h by FACS. (B) Statistical results of FACS. *<i>P</i> < 0.05 vs ctr.</p

The test on death modes of THP-1 cells and macrophages induced by JDBM extract with different concentration or RPMI 1640 medium (Ctr).

<p>(A) A representative result of cell performance in various extract assayed by FACS for 72h. (B and C) Percentage of THP-1 cells and macrophages in different death mode, respectively, which cultured in JDBM extract or ctr for 72h.(D and E) The expression of aptosis-related genes in THP-1 cells and macrophages treated with indicated *<i>P</i> < 0.05 vs ctr.</p

The impact of PMA and JDBM extracts on cell differentiation of THP-1 cells into macrophage.

<p>PMA treatment alone was pos-ctr, PRMI 1640 treatment alone was neg-ctr. (A-C) representative results of FACS test on CD14, CD54 and TLR-2, respectively, after induced by JDBM extract cell differentiation performance in various extract assayed. THP-1 cell without PMA was THP-1 and with PMA was ctr. (D) Statistical results of the expression change on CD14, CD54 and TLR-2 of cell under various extracts. *<i>P</i> < 0.05 vs ctr, ^▲<i>P</i> < 0.05 vs THP-1.</p

Facile Preparation of Poly(lactic acid)/Brushite Bilayer Coating on Biodegradable Magnesium Alloys with Multiple Functionalities for Orthopedic Application

Recently magnesium and its alloys have been proposed as a promising next generation orthopedic implant material, whereas the poor corrosion behavior, potential cytotoxicity, and the lack of efficient drug delivery system have limited its further clinical application, especially for the local treatment of infections or musculoskeletal disorders and diseases. In this study, we designed and developed a multifunctional bilayer composite coating of poly­(lactic acid)/brushite with high interfacial bonding strength on a Mg–Nd–Zn–Zr alloy, aiming to improve the biocorrosion resistance and biocompatibility of the magnesium-based substrate, as well as to further incorporate the biofunctionality of localized drug delivery. The composite coating consisted of an inner layer of poly­(lactic acid) serving as a drug carrier and an outer layer composed of brushite generated through chemical solution deposition, where a facile pretreatment of UV irradiation was applied to the poly­(lactic acid) coating to facilitate the heterogeneous nucleation of brushite. The in vitro degradation results of electrochemical measurements and immersion tests indicated a considerable reduction of magnesium degradation provided the composite coating. A systematic investigation of cellular response with cell viability, adhesion, and ALP assays confirmed the coated Mg alloy induced no toxicity to MC3T3-E1 osteoblastic cells but rather fostered cell attachment and proliferation and promoted osteogenic differentiation, revealing excellent biosafety and biocompatibility and enhanced osteoinductive potential. An in vitro drug release profile of paclitaxel from the composite coating was monitored with UV–vis spectroscopy, showing an alleviated initial burst release and a sustained and controlled release feature of the drug-loaded composite coating. These findings suggested that the bilayer poly­(lactic acid)/brushite coating provided effective protection for Mg alloy, greatly enhanced cytocompatibility and bioactivity, and, moreover, possessed local drug delivery capability; hence magnesium alloy with poly­(lactic acid)/brushite coating presents great potential in orthopedic clinical applications, especially for localized bone therapy

Enhanced Corrosion Resistance and Biocompatibility of Magnesium Alloy by Mg–Al-Layered Double Hydroxide

Magnesium (Mg) and its alloys have been suggested as revolutionary biodegradable materials. However, fast degradation hinders its clinic application. To improve the corrosion resistance and biocompatibility of Mg–Nd–Zn–Zr alloy (JDBM), magnesium–aluminum-layered double hydroxide (Mg–Al LDH) was successfully introduced into Mg­(OH)₂ coating by hydrothermal treatment. The anions in the interlayer of Mg–Al LDH can be replaced by chloride ions, resulting in a relatively low chloride ion concentration near the surface of the coating. The favorable corrosion resistance of the coating was proved by polarization curves and hydrogen collection test. The Mg–Al LDH significantly promoted cell adhesion, migration and proliferation in vitro. In addition, the coating almost fulfilled the request of the clinical application in the hemolysis ratio test. Finally, in vivo results indicated that the coating offered the greatest long-lasting protection from corrosion and triggered the mildest inflammation comparing to the pure Mg­(OH)₂ coatings and untreated magnesium alloy. Mg­(OH)₂ coating containing Mg–Al LDH in the present study shows a promising application in improving anticorrosion and biocompatibility of Mg alloys, and might act as a platform for a further modification of Mg alloys ascribed to its special layer structure