Magnesium (Mg)-based alloys have become an important category of materials that is attracting more and more attention due to their high potential use as orthopedic temporary implants. These alloys are a viable alternative to nondegradable metals implants in orthopedics. In this paper, a detailed overview covering alloy development and manufacturing techniques is described. Further, important attributes for Mg-based alloys involved in orthopedic implants fabrication, physiological and toxicological effects of each alloying element, mechanical properties, osteogenesis, and angiogenesis of Mg are presented. A section detailing the main biocompatible Mg-based alloys, with examples of mechanical properties, degradation behavior, and cytotoxicity tests related to in vitro experiments, is also provided. Special attention is given to animal testing, and the clinical translation is also reviewed, focusing on the main clinical cases that were conducted under human use approval.

Fluoride conversion coatings on Mg present many advantages, among which one can find the reduction of the corrosion rate under “in vivo” or “in vitro” conditions and the promotion of the calcium phosphate deposition. Moreover, the fluoride ions released from MgF2 do not present cytotoxic effects and inhibit the biofilm formation, and thus these treated alloys are very suitable for cardiovascular stents and biodegradable orthopedic implants. In this paper, the biodegradation behavior of four new magnesium biodegradable alloys that have been developed in the laboratory conditions, before and after surface modifications by fluoride conversion (and sandblasting) coatings, are analyzed. We performed structural and surface analysis (XRD, SEM, contact angle) before and after applying different surface treatments. Furthermore, we studied the electrochemical behavior and biodegradation of all experimental samples after immersion test performed in NaCl solution. For a better evaluation, we also used LM and SEM for evaluation of the corroded samples after immersion test. The results showed an improved corrosion resistance for HF treated alloy in the NaCl solution. The chemical composition, uniformity, thickness and stability of the layers generated on the surface of the alloys significantly influence their corrosion behavior. Our study reveals that HF treatment is a beneficial way to improve the biofunctional properties required for the studied magnesium alloys to be used as biomaterials for manufacturing the orthopedic implants.

The theory of differential equations has been widely known and developed in recent years. One of the issues that many authors give their undivided attention to is the stability boundary of nonlinear dynamical systems. In this work, we first review several properties of equilibrium points on the stability boundary. We next extend the characteristics of the stability boundary for a fairly large class of nonlinear dynamical systems. These characteristics are the key to completely determine the stability boundary of nonlinear dynamical systems.

Biodegradability of magnesium alloys in physiological media is important for material use in implant manufacture industry. Two industrial Mg alloys ZQ71 and ZQ63 were investigated. Optical microscopy was used to put in evidence microstructure. The conclusions are correlated with obtained results after scanning electron microscopy investigations coupled with energy dispersive X-ray spectroscopy. The evaluation of the hydrogen released rate was analyzed in laboratory made simulated body fluid (SBF) and Hanks’ solution at 37°C for 10 days. Different degradation rates are obtained, and it can be concluded that they depend on chemical composition of the alloys and on immersion time of the samples in different physiological solutions.

In 2015, a novel circovirus (Porcine circovirus 3, PCV3) was detected for the first time from pigs suffered from porcine dermatitis and nephropathy syndrome and reproductive failure. Since then, PCV3 has been reported in several pig producing countries. This study was carried out in order to investigate the presence and further genetic characterization of PCV3 in the pig populations in northern Vietnam. The screening PCR detected the presence of PCV3 in 6 out of 135 samples (4.44%) which were collected from seven northern provinces in 2011 and 2016-2017. The capsid-coding gene (ORF2, 645 nucleotides in length) was successfully sequenced from 5 out of 6 field strains. Compared to a highly diverse PCV3 strain (GD2016-1, KY421347) 5 Vietnamese PCV3 strains contained 39 point nucleotide mutations and 9 of those were non-synonymous. The Bayesian phylogenetic analysis on the basic of ORF2 revealed that PCV3 evolved at a comparable evolutionary rate of the pathogenic PCV2 (2.284 × 10 -3 and 1.440 × 10 -3 , respectively). Besides, this analysis suggested PCV3 could be separated into PCV3a and PCV3b groups, of which the majority of Vietnamese PCV3 strains belong to PCV3a (sub-cluster a1).