Biodegradable PMMA coated Zn-Mg alloy with bimodal grain structure for orthopedic applications - A promising alternative.

The study examines the impact of microstructure and polymethyl methacrylate (PMMA) grafting on the degradability of Zn-Mg alloys. The mechanical properties of a Zn alloy containing 0.68 wt% Mg and extruded at 200 °C are enhanced for degradable load-bearing applications, addressing a crucial need in the field. The material exhibits a bimodal grain size distribution that is random texture, consisting of secondary phases, grains, and sub-grains. With an elongation to failure of 16 %, the yield and ultimate tensile strengths are 325.9 and 414.5 MPa, respectively, and the compressive yield strength is 450.5 MPa. The "grafting-from" method was used to coat a few micrometers thick of PMMA on both bulk and scaffold Zn alloys to mitigate the corrosion rate. The last one is a porous structure, with a porosity of 65.8 %, considered as in the first approach of an orthopedic implant. After being immersed for 720 h, the PMMA-grafted bulk alloy's corrosion rate decreased from 0.43 to 0.25 mm/y. Similarly, the scaffold alloy's corrosion rate reduced from 1.24 to 0.49 mm/y. These results indicate that the method employed could be used for future orthopedic applications.

Effect of Mg Addition and PMMA Coating on the Biodegradation Behaviour of Extruded Zn Material.

Although zinc (Zn) is one of the elements with the greatest potential for biodegradable uses, pure Zn does not have the ideal mechanical or degrading properties for orthopaedic applications. The current research aims at studying the microstructure and corrosion behaviour of pure Zn (used as a reference material) and Zn alloyed with 1.89 wt.% magnesium (Mg), both in their extruded states as well as after being coated with polymethyl methacrylate (PMMA). The grafting-from approach was used to create a PMMA covering. The "grafting-from" method entails three steps: the alkali activation of the alloys, their functionalization with an initiator of polymerization through a phosphonate-attaching group, and the surface-initiated atom transfer radical polymerisation (SI-ATRP) to grow PMMA chains. Electrochemical and immersion corrosion tests were carried out in a simulated body fluid (SBF), and both confirmed the enhanced corrosion behaviour obtained after coating. The electrochemical test revealed a decrease in the degradation rate of the alloy from 0.37 ± 0.14 mm/y to 0.22 ± 0.01 mm/y. The immersion test showed the ability of complete protection for 240 h. After 720 h of immersion, the coated alloy displays minute crevice corrosion with very trivial pitting compared to the severe localized (galvanic and pitting) corrosion type that was detected in the bare alloy.

A novel HCV electrochemical biosensor based on a polyaniline@Ni-MOF nanocomposite.

Hepatitis-C virus ribonucleic acid (HCV-RNA) recognition and quantification based on real-time polymerase chain reaction (RT-PCR) is key to infection control, management, and response to treatment due to its specificity, sensitivity, and quantification capabilities. However, the high cost, time requirements, and need for sophisticated laboratory infrastructure have limited the use of this method in rapid screening, blood banks, and point-of-care testing (POCT). In this work, a novel label-free electrochemical biosensor constructed using a polyaniline@nickel metal-organic framework (Ni-MOF) nanocomposite was developed for direct detection of unamplified HCV nucleic acid. A robust biosensor was fabricated using smooth layer-by-layer deposition of the polyaniline@Ni-MOF nanocomposite, deoxyribonucleic acid (DNA) probe, and bovine serum albumin (BSA) onto a glassy carbon electrode (GCE) and was subsequently monitored real-time via cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The sensitivity and specificity of the newly developed biosensor were specifically examined using the EIS approach. The results revealed that the novel biosensor is highly efficient in quantitative sensing of the HCV target in the presence of nonspecific nucleic acids over the range of 1 fM-100 nM with a detection limit of 0.75 fM (at a S/N ratio of 3). To the best of the authors' knowledge, the proposed biosensor is superior to other MOF platforms. These research findings are expected to have a positive influence on the quantitative detection of HCV RNA and other nucleic acids by offering exceptional accuracy and cost effectiveness, especially in low resource countries. Moreover, this biosensor could be simply adopted for full automation and used in point-of-care testing.