Ultrathin hydroxyapatite coating on pure magnesium substrate prepared by pulsed electron ablation technique

Magnesium (Mg) as a potential material for biodegradable implants is attractive due to its mechanical similarity to the bone tissue and nontoxic corrosion products. However, the rapid corrosion rate of bare magnesium is associated with hydrogen release, which may complicate the healing process. The corrosion rate may be reduced by suitable alloying, but concurrently the biocompatibility of such alloy might be deteriorated. Another way of reduction of the corrosion rate is coating. Hydroxyapatite (HA)-based coating is considered to improve biocompatibility as well as decrease the corrosion rate by the barrier effect. In this study, ultrathin (150 nm) HA and HA containing Sr coatings are deposited via pulsed electron ablation technique on pure Mg. The microstructure of the coating was assessed by scanning electron microscopy. Electrochemical methods were used to investigate the corrosion properties of prepared coatings. The materials covered by this layer were characterized by superior corrosion behavior, with corrosion rates of coated samples up to five times lower as compared with the uncoated ones. Such coating is the thinnest coating found in the literature sources.     

Crosslinked,biodegradable polyurethanes for precision-porous biomaterials: Synthesis and properties

Crosslinked poly(ester urethane)s and their acrylate derivatives based on trifunctional polycaprolactone and trifunctional aliphatic isocyanates were synthesized. Biodegradable scaffolds with uniform, controlled micron-scale porosity were fabricated with these materials. Mechanical and swelling properties of monolithic and microporous materials were studied. Cytotoxicity, hydrolytic, and enzymatic degradation and their effects on mechanical properties of the biodegradable scaffolds were investigated. The polymer degradation products were found not to be cytotoxic at moderate concentrations and to permit cell attachment and spreading. Degradation rates and mechanical properties could be tuned to desired performance criteria for a given application by adjusting crosslink density and the ratio of hard segment to soft segment. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48943.     

Electrospun microporous gelatin–polycaprolactone blend tubular scaffold as a potential vascular biomaterial

The work reported involved the fabrication of an electrospun tubular conduit of a gelatin and polycaprolactone (PCL) blend as an adventitia‐equivalent construct. Gelatin was included as the matrix for increased biocompatibility with the addition of PCL for durability. This is contrary to most of the literature available for biomaterials based on blends of gelatin and PCL where PCL is the major matrix. The work includes the assiduous selection of key electrospinning parameters to obtain smooth bead‐free fibres with a narrow distribution of pore size and fibre diameter. Few reports elucidate the optimization of all electrospinning parameters to fabricate tubular conduits with a focus on obtaining homogeneous pores and fibres. This stepwise investigation would be unique for the fabrication of gelatin–PCL electrospun tubular constructs. The fabricated microfibrous gelatin–PCL constructs had pores of size ca 50–100 μm reportedly conducive for cell infiltration. The measured value of surface roughness of 57.99 ± 17.4 nm is reported to be favourable for protein adhesion and cell adhesion. The elastic modulus was observed to be similar to that of the tunica adventitia of the native artery. Preliminary in vitro and in vivo biocompatibility tests suggest safe applicability as a biomaterial. Minimal cytotoxicity was observed using MTT assay. Subcutaneous implantation of the scaffold demonstrated acute inflammation which decreased by day 15. The findings of this study could enable the fabrication of smooth bead‐free microfibrous gelatin–PCL tubular construct as viable biomaterial which can be included in a bilayer or a trilayer scaffold for vascular tissue engineering. © 2019 Society of Chemical Industry     

SiC和Al2O3颗粒对Ti-25Nb-3Mo-3Zr-2Sn合金微磨损行为的影响

本文研究了SiC和Al₂O₃颗粒对生物医用植入材料Ti-25Nb-3Mo-3Zr-2Sn合金的微磨损行为的影响。在文中研究了合金的比磨损率、摩擦系数、磨损机制以及微磨损与腐蚀之间的协同作用。研究结果显示,合金的比磨损率随磨粒尺寸的增加而增加。由于SiC磨粒的硬度和切削性均优于Al₂O₃磨粒,由此在同尺寸磨粒下SiC磨粒所造成的材料的损失比Al₂O₃磨粒造成的要大。摩擦系数的结果显示,在同一种磨粒作用下,Hank’s溶液中所获得的摩擦系数的平均值大于蒸馏水中所获得的摩擦系数平均值,且由于Hank’s溶液的腐蚀性所致在Hank’s溶液中获得的摩擦系数的稳定性要比在蒸馏水中的稳定性差;在同尺寸磨粒下,Al₂O₃磨粒所造成的摩擦系数要大于SiC磨粒所造成的。随磨粒尺寸的减小,磨损机制由三体磨损转变为混合磨损之后再转变为二体磨损。从磨损机制图中可以看出腐蚀对材料损失的贡献是不容小视的,磨损机制为以磨损为主的磨损腐蚀。     

Synthesis of hydroxyapatite fibers using electrospinning: A study of phase evolution based on polymer matrix

Hydroxyapatite (HA) is considered as the most promising biomaterial candidate to replace and regenerate hard tissues. A small amount of β-tricalcium phosphate (β-TCP) phase is advantageous for rapid bonding of the artificial bones to natural ones due to its high solubility compared to hydroxyapatite. Synthesizing HA nanofibers from electrospinning of sol-gel is considered as a widely researched topic. Motivation of the current work was to investigate the influence of polymeric binder in the final phase evolution after heat treatment of electrospun nanofibers. Calcium phosphate nanofibers were fabricated by electrospinning sols using gelatine and polyvinylpyrrolidone as carrier polymers and subjected to heat treatment. It was realized that carrier polymers facilitate preferential calcium phosphate phase formation by forming hydroxyapatite as major phase while PVP was used and β-TCP with HA as secondary phase while gelatine was employed. XRD and thermal analyses were performed to ascertain the reason behind this interesting behaviour.     

Synthesis and Characterization Superabsorbent Polymers Made of Starch,Acrylic Acid,Acrylamide, Poly(Vinyl Alcohol), 2-Hydroxyethyl Methacrylate, 2-Acrylamido-2-methylpropane Sulfonic Acid

Three polymers with excellent absorption properties were synthesized by graft polymerization: soluble starch-g-poly(acrylic acid-co-2-hydroxyethyl methacrylate), poly(vinyl alcohol)/potato starch-g-poly(acrylic acid-co-acrylamide), poly(vinyl alcohol)/potato starch-g-poly(acrylic acid-co-acrylamide-co-2-acrylamido-2-methylpropane sulfonic acid). Ammonium persulfate and potassium persulfate were used as initiators, while N,N′-methylenebisacrylamide was used as the crosslinking agent. The molecular structure of potato and soluble starch grafted by synthetic polymers was characterized by means of Fourier Transform Infrared Spectroscopy (FTIR). The morphology of the resulting materials was studied using a scanning electron microscope (SEM). Thermal stability was tested by thermogravimetric measurements. The absorption properties of the obtained biopolymers were tested in deionized water, sodium chroma solutions of various concentrations and in buffer solutions of various pH.