Electrochemical surface engineering of magnesium metal by plasma electrolytic oxidation and calcium phosphate deposition: biocompatibility and in vitro degradation studies

In this study, the surface of magnesium metal was electrochemically engineered for enhanced biocompatibility and controlled degradation in body fluid. Firstly, a plasma electrolytic oxidation (PEO) coating was formed on magnesium, followed by electrochemical deposition of calcium phosphate (CaP) using an unconventional electrolyte. Cytocompatibility tests using L929 cells revealed that the PEO-CaP coating significantly improved the biocompatibility of magnesium. In vitro electrochemical degradation experiments in simulated body fluid (SBF) showed that the PEO-CaP coating improved the degradation resistance of magnesium significantly. The corrosion current density (i_corr) of the PEO-CaP coated magnesium was ∼99% and ∼97% lower than that of bare magnesium and the PEO-only coated magnesium, respectively. Similarly, electrochemical impedance spectroscopy (EIS) results showed that the polarisation resistance (R_P) of the PEO-CaP coated magnesium was one-order of magnitude higher as compared to the PEO-only coated magnesium and two-orders of magnitude higher than the bare magnesium, after 72 h immersion in SBF. Scanning electron microscopy (SEM) analysis revealed no localized degradation in the PEO-CaP coated magnesium. The study demonstrated that the PEO-CaP coating is a promising combination for enhancing the biocompatibility and reducing the degradation of magnesium for potential biodegradable implant applications.

The PEO-CaP coating produced on magnesium metal using an unconventional electrolyte enhanced the degradation resistance and provided excellent cytocompatibility.     

Biological behavior exploration of a paclitaxel-eluting poly-l-lactide-coated Mg–Zn–Y–Nd alloy intestinal stent in vivo

As a new type of intestinal stent, the MAO/PLLA/paclitaxel/Mg–Zn–Y–Nd alloy stent has shown good degradability, although its biocompatibility in vitro and in vivo has not been investigated in detail. In this study, its in vivo biocompatibility was evaluated by animal study. New Zealand white rabbits were implanted with degradable intestinal Mg–Zn–Y–Nd alloy stents that were exposed to different treatments. Stent degradation behavior was observed both macroscopically and using a scanning electron microscope (SEM). Energy dispersion spectrum (EDS) and histological observations were performed to investigate stent biological safety. Macroscopic analysis showed that the MAO/PLLA/paclitaxel/Mg–Zn–Y–Nd stents could not be located 12 days after implantation. SEM observations showed that corrosion degree of the MAO/PLLA/paclitaxel/Mg–Zn–Y–Nd stents implanted in rabbits was significantly lower than that in the PLLA/Mg–Zn–Y–Nd stent group. Both histopathological testing and serological analysis of in vivo biocompatibility demonstrated that the MAO/PLLA/paclitaxel/Mg–Zn–Y–Nd alloy stents could significantly inhibit intestinal tissue proliferation compared to the PLLA/Mg–Zn–Y–Nd alloy stents, thus providing the basis for designing excellent biodegradable drug stents.

Mg–Zn–Y–Nd alloy stents coated with MAO/PLLA/paclitaxel coating were implanted into the New Zealand rabbits intestine to investigate the biocompatibility and degradation behavior.     

Revisiting the role of durable polymers in cardiovascular devices

Introduction: Polymers are an essential component of drug-eluting stents (DES) used to control drug release but remain the most controversial component of DES technology. There are two types of polymers employed in DES: durable polymer based DES (DP-DES) and biodegradable polymer DES (BP-DES). First-generation DES were exclusively composed of DP and demonstrated increased rates of late stent failure due in part to poor polymer biocompatibility. Newer generations DES use more biocompatible durable polymers or biodegradable polymers.

Areas covered: We will cover issues identified with 1st-generation DP-DES, areas of success and failure in 2nd-generation DP-DES and examine the promise and shortcomings of BP-DES. Briefly, fluorinated polymers used in 2nd-generation DP-DES have excellent anti-thrombogenicity and better biocompatibility than 1st-generation DES polymers. However, these devices lead to persistent drug exposure to the endothelium which impairs endothelial function and predisposes towards neoatherosclerosis. Meanwhile, BP-DES has shortened the duration of drug exposure which might be beneficial for endothelial functional recovery leading to less neoatherosclerosis. However, it remains uncertain whether the long-term biocompatibility of bare metal surfaces is better than that of polymer-coated metals.

Expert commentary: Each technology has distinct advantages, which can be optimized depending upon the particular characteristics of the patient being treated.     

An antibacterial and biocompatible multilayer biomedical coating capable of healing damages

Besides the excellent biocompatibility and high antibacterial property, multifunctional biomedical coatings with a long service time is highly desirable for extended applications, which is still an ongoing challenge. The self-healing property enables new directions for effectively prolonging their service life and significantly improving their reliability. Herein, an efficient and simple method is used to facilely prepare antibacterial, biocompatibile multilayer polyelectrolyte coatings, which are capable of healing damages. The synthetic strategy involves the alternate deposition of Chitosan (CS) and sodium carboxymethyl cellulose (CMC) via the layer-by-layer (LBL) self-assembly technique. The CS/CMC multilayer polyelectrolyte coating features high antibacterial property, fast and efficient self-healing property, and excellent biocompatibility. These features allow the CS/CMC polyelectrolyte coating to have extended lifespan and to be highly promising for novel functional stent coating applications.

A CS/CMC multilayer polyelectrolyte coating was developed, which features fast and efficient self-healing property, high antibacterial property, and excellent biocompatibility.     

Effect of biodegradable magnesium-copper coatings on bone integration based on the porous structures in a rabbit model

Biodegradable magnesium (Mg)–copper (Cu) coatings are promising in orthopedic implants to enhance osteogenesis. The present study aimed to compare the osteogenic effect of Mg–Cu coating and non-coating implants using a rabbit model. Mg/Mg–Cu coating of porous Ti6Al4V alloys was performed by the arc ion plating method. Five porous implants (smooth, porous, Mg coated, Mg–0.1Cu coated, and Mg–0.7Cu coated) were implanted into the distal femurs of the rabbits. The rabbits were sacrificed after one and two months, respectively, and the distal femurs with the implants were analyzed via micro-computed tomography (CT), double fluorescent labeling, and hard tissue biopsy to evaluate their osteogenic effect. During the two months of observation, the Mg/Mg–Cu coatings exhibited no advantages when compared with the bare porous structures in terms of bone integration; however, the porous structures were more conducive for bone ingrowth than the smooth implants. The osteogenic application of Mg–Cu coated orthopedic implants is worth further investigation. Furthermore, due to its long-term antibacterial ability, the biodegradable Mg–Cu coatings are promising in orthopedic applications.

The results of the present study suggest that the application of Mg–Cu coating in orthopedic implants is mainly due to its long-term antibacterial ability rather than its osteogenesis ability.     

Silane coatings modified with hydroxyapatite nanoparticles to enhance the biocompatibility and corrosion resistance of a magnesium alloy

The fast corrosion rate of magnesium alloys has restricted their use as biodegradable implants. Hence developing a practical approach to retard the corrosion rate of the AZ31 magnesium alloy, as well as promoting cell adhesion and proliferation is of great importance. Silane coatings were applied through dip coating, on samples pretreated in hydrofluoric acid. Samples were immersed in simulated body fluid at 37 °C, and the coating performance was assessed by electrochemical impedance spectroscopy. The coating morphologies of samples were investigated through field emission scanning electron microscopy and a cell viability/proliferation (MTT) test was performed to evaluate cellular response. A 2.2 μm-thick coating was accomplished, which increased the corrosion resistance to three orders of magnitude higher than that of the bare sample. Hydroxyapatite nanoparticles were added to the silane coating to improve biocompatibility and facilitate bone formation. Changing the concentration of hydroxyapatite nanoparticles not only helped to optimize the barrier properties of the silane coating but also ameliorated MG-63 osteoblastic cell growth. The findings showed great promise to enhance and maintain the corrosion barrier property and induce high osteoblastic differentiation by employing 1000 mg L⁻¹ of hydroxyapatite nanoparticles.

Incorporation of hydroxyapatite nanoparticles in silane coatings improves both corrosion resistance and cell viability on magnesium AZ31 implants.     

Unveiling the effect of 11-MUA coating on biocompatibility and catalytic activity of a gold-core cerium oxide-shell-based nanozyme

The biocompatibility and catalytic activity of nanomaterials exhibiting biological enzyme-like functions (nanozymes) are controlled by shape, size, composition, and surface capping molecules. Although synthesis of multifunctional nanozymes for multiple applications has shown tremendous attraction among researchers worldwide, often their biocompatibility is compromised. In this work, we report the replacement of CTAB by 11-MUA from the surface of a Au-core CeO₂-shell NP-based nanozyme studied for exhibiting multiple enzyme-like activities such as peroxidase, catalase, and superoxide dismutase. We compared the biocompatibility and enzyme-like activities of CTAB coated Au-core CeO₂-shell NPs (CSNPs) before and after 11-MUA coating. The catalytic reaction mechanism of peroxidase-like activity of CTAB coated CSNPs was found to be the “Random Bi–Bi”, which also remained unaltered after removal of surface CTAB with 11-MUA. The other kinetic parameters, K_m and V_max values, of 11-MUA coated CSNPs were found to be comparable to the CTAB coated NPs.

Replacement of CTAB and CeO₂ nanoparticle layer by 11-MUA from the surface of Au core-CeO₂ shell nanoparticle.     

The corrosion resistance,cytotoxicity, and antibacterial properties of lysozyme coatings on orthodontic composite arch wires

Objective: The corrosion resistance of new orthodontic composite arch wires (CAWs), which have excellent mechanical properties in a simulated oral environment, must be improved. This study explored the susceptibility to corrosion, in vitro cytotoxicity, and antibacterial properties of lysozyme-coated CAWs. Methods: Lysozyme coating of laser-welded CAW surfaces was prepared by liquid phase deposition. Four groups of CAW specimens were prepared: uncoated CAWs and CAWs coated with 20, 40, and 60 g L⁻¹ lysozyme. The surface morphology of the lysozyme coatings was characterized by atomic force microscopy. The samples were immersed in artificial saliva (AS) for 2 weeks, and corrosion morphology was then observed by scanning electron microscopy. Corrosion behavior was characterized according to weight loss and electrochemical properties. The cytotoxicity and antibacterial properties of lysozyme-coated CAWs were assessed by cell counting kit-8 assay and a live/dead bacterial test, respectively. Results: Surfaces in the three lysozyme coating groups exhibited film-like deposition, the thickness of which increased with the lysozyme concentration. Surface pitting and copper ion precipitation decreased with increasing lysozyme concentration in coatings. The corrosion tendency declined as the corrosion and pitting potentials decreased. The corrosion morphology and electrochemical parameters together indicated that lysozyme coatings increased corrosion resistance. The coatings also reduced cytotoxicity to L-929 cells and increased anti-Staphylococcus aureus ability. Conclusions: Lysozyme coating of CAW surfaces by liquid phase deposition improved the corrosion resistance of CAWs. The protective coatings improved biocompatibility and endowed the CAW surfaces with certain degrees of anti-Staphylococcus aureus activity. Different lysozyme concentrations had different protective effects, with 40 g L⁻¹ maybe being the ideal lysozyme concentration for CAW coatings.

The corrosion resistance of new orthodontic composite arch wires (CAWs), which have excellent mechanical properties in a simulated oral environment, must be improved.     

Novel waterborne UV-curable coatings based on hyperbranched polymers via electrophoretic deposition

Two modified types of hyperbranched polymer were successfully prepared using hyperbranched polyether (HBPE) as a matrix, cis-5-norbornene-endo-2,3-dicarboxylic anhydride (CDA) or o-phthalic anhydride (PA) as a modifier and by grafting an NCO-terminated compound (IPDI-HEA). The modified hyperbranched polymers were incorporated into a typical water-soluble polyacrylate (WPA) as crosslinkers to develop high-performance waterborne UV-curable coatings via electrophoretic deposition (EPD). Although the particle size of the electrophoretic dispersion increased from 43.8 nm to 164 nm, no microphase separation occurred, and the smooth SEM images of the coatings confirmed their uniformity. The rate of photopolymerization (R_p) and percentage conversion of the double bonds increased with increasing active unsaturated double bond content, and were partially affected by steric effects. Thermal gravity analysis and tensile tests indicated that the UV-curable EPD coating films exhibited better thermal stability due to their hyperbranched structure, soft and hard segment content and crosslinking density. The coated tin plate could resist chemical corrosion after immersion in NaCl solution. The coatings demonstrated strong adhesion to extremely bent tin plates and outstanding tolerance to knife-scratches and impact. This is a promising method for the design of desirable coatings in the EPD industry.

Two modified types of polymer were based on hyperbranched polyether (HBPE) and used for UV-curable EPD coatings. The properties of the coatings were analyzed from the perspective of hyperbranched structures.     

Structural heterogeneity in polymeric nitric oxide donor nanoblended coatings for controlled release behaviors

Nitric oxide (NO) gas delivery has attracted extensive interest due to its endogenous therapeutic functions and potential biomedical applications for the treatment of various diseases. The important thing about NO delivery is the emission control due to the fast diffusion rate of gas molecules. To develop NO delivery platforms using macromolecules and to comprehend the chemical NO donor generation and release mechanisms, we studied branched polyethyleneimine/alginate (BPEI/ALG) nanoblended coatings fabricated by giving structural heterogeneity to the structure through a self-assembly process for the controlled release of gas molecules. NO release could be remarkably expected via the well-organized coating structures and explained by quantification of the NO donors. Taking advantage of these polymeric coatings, this process could be applied to the treatment of various diseases based on the biocompatibility of materials and the fine control of NO release rate and its amount.

Controlled nitric oxide (NO) delivery based on the heterogeneity of polymeric coating structures for local NO treatment.     

Sustainable smart anti-corrosion coating materials derived from vegetable oil derivatives: a review

Sustainable development is a critical concern in this fast-paced technological world. Therefore, it is essential to employ renewable resources to move towards sustainable development goals (SDGs). The polyols attained from renewable resources, including lignin, chitosan, vegetable oils, cellulose, etc. and the polymers derived from them have attracted the attention of the majority of researchers, both in academia and industry. The development of bio-based polymers from vegetable oils start emerging with different properties to generate a value-added system. This review will give an impression to readers about how coatings generated from vegetable oils can find a way towards better protective properties against corrosion either by using fillers or by using molecular structure modifications in the system, thus covering a range of vegetable oil-based self-healing polymers and their application in anti-corrosion coatings.

The article covers coating materials using bio-chemical derived molecules (vegetable oils) and their properties including mechanical, self-healing and anti-corrosion properties.     

Bi-functional titanium-polydopamine-zinc coatings for infection inhibition and enhanced osseointegration

The ideal orthopedic implant coating is expected to both inhibit microbial infection and promote osseointegration. In this study, Zn ions were immobilized on a Ti substrate via a polydopamine (PDA) chemical surface modification to prepare Ti-PDA-Zn coatings. Scanning electron microscopy (SEM), atomic force microscopy (AFM), energy-dispersive X-ray spectroscope (EDS), X-ray photoelectron spectroscopy (XPS), contact analysis system, and inductively coupled plasma atomic emission spectrometry (ICP-AES) were used to analyze the morphology, composition, wettability, and zinc ions release of the coatings. The Ti-PDA-Zn coatings demonstrated excellent antibacterial activities in vitro against both Staphylococcus aureus and Escherichia coli. The coatings additionally displayed good biocompatibility, as confirmed by cytoskeletal observations and cell viability assays. Furthermore, the in vivo results confirmed the excellent antibacterial properties and improved osseointegration capability of the Ti-PDA-Zn coating in the presence of S. aureus. The present findings indicate that the Ti-PDA-Zn coatings prepared herein have potential application in orthopedic implantation.

The ideal orthopedic implant coating is expected to both inhibit microbial infection and promote osseointegration.     

The effect of the surface coating of a strontium mono-aluminate europium dysprosium-based (SrAl2O4:Eu2+,Dy3+) phosphor by polyethylene (PE), polystyrene (PS) and their dual system on the photoluminescence properties of the pigment

SrAl₂O₄:Eu²⁺,Dy³⁺ as a known strontium mono-aluminate europium dysprosium-based phosphor is widely used in paints and coating formulations as a photoluminescence pigment. It has two major drawbacks: improper dispersion in organic-based paints and weak water and moisture resistance. To address the above-mentioned drawbacks, the surface coating of phosphors with polyethylene and polystyrene individually and in combination using a solution technique was performed. The FT-IR spectra showed that the used polymers were coated on the phosphor properly. Also, the EDS spectra showed the presence of elemental carbon for the treated phosphors with different amounts. No regular trend was observed for element ratios when the polyethylene content in the coating layer was reduced from 100 to 0%. Based on the XRD patterns, the crystalline structure of the coated phosphors was not affected by the polymeric coated layer. In the SEM micrographs, the sharp and rough edges of the uncoated phosphor changed to a smooth and soft state for the coated phosphors. The brightness of most of the coated phosphors was independent of time and did not change over a period of 5 minutes after UV irradiation. This property makes the polymeric coated phosphors suitable as photoluminescence pigments in all kinds of paints and coatings.

SrAl₂O₄:Eu²⁺,Dy³⁺ as a known strontium mono-aluminate europium dysprosium-based phosphor is widely used in paints and coating formulations as a photoluminescence pigment.     

Preparation of antistatic epoxy resin coatings based on double comb-like quaternary ammonium salt polymers

Two kinds of double comb-like quaternary ammonium salt polymers P(DPA-EPI) and P(DBA-EPI) with lower polarity were designed and synthesized using epichlorohydrin (EPI), di-n-propylamine (DPA) and di-n-butylamine (DBA) as raw materials. The transparent antistatic epoxy resin coatings were obtained using the two polymers as antistatic agents, respectively. Because P(DPA-EPI) and P(DBA-EPI) with good hygroscopic performance are easily dissolved in epoxy resin paints and are nearly linearly arranged in the epoxy resin paints, the obtained transparent antistatic epoxy resin coatings achieve good antistatic properties. The values of ρ_s of the coatings reach 5.13 × 10⁸ Ω sq⁻¹ and 2.69 × 10⁸ Ω sq⁻¹, respectively, with a lower addition amount of polymers of only 1.0 wt%. The two antistatic epoxy resin coatings also have good durability. Compared to the epoxy resin coating, with the introduction of P(DPA-EPI) and P(DBA-EPI), the thermal stability and adhesion of the antistatic epoxy resin coatings do not change obviously, but the Rockwell hardness values slightly reduce.

The antistatic epoxy resin coatings using double comb-like quaternary ammonium salt polymers as antistatic agents reach good antistatic property with lower addition amount because polymers can dissolve and nearly linearly arrange in the coatings.     

Fabrication of hydroxyapatite coatings on AZ31 Mg alloy by micro-arc oxidation coupled with sol–gel treatment

Magnesium (Mg) alloys, can potentially be used as biodegradable orthopedic implants because of their biodegradability and good mechanical properties. However, a quick degradation rate and low bioactivity have prevented their clinical application. In order to enhance the corrosion resistance and the in vitro bioactivity of Mg alloys, protective composite coatings were prepared on AZ31 magnesium alloy followed by sol–gel sealing treatment under low-pressure conditions. The morphologies, crystalline structure and the composition of the samples were characterized by SEM, XRD, and XPS. Electrochemical corrosion test and the in vitro bioactivity were also studied. The results indicated that the composite coatings not only improved the corrosion resistance, but also enhanced the in vitro bioactivity of AZ31 Mg alloy. Therefore, Mg alloy treated with micro-arc oxidation and sol–gel offers a promising approach for biodegradable bone implants.

Magnesium (Mg) alloys, can potentially be used as biodegradable orthopedic implants because of their biodegradability and good mechanical properties.     

Charged ultrafiltration membranes based on TEMPO-oxidized cellulose nanofibrils/poly(vinyl alcohol) antifouling coating

This study reports the potential of TEMPO-oxidized cellulose nanofibrils (T-CNF)/poly(vinyl alcohol) (PVA) coatings to develop functionalized membranes in the ultrafiltration regime with outstanding antifouling performance and dimensional/pH stability. PVA acts as an anchoring phase interacting with the polyethersulfone (PES) substrate and stabilizing for the hygroscopic T-CNF via crosslinking. The T-CNF/PVA coated PES membranes showed a nano-textured surface, a change in the surface charge, and improved mechanical properties compared to the original PES substrate. A low reduction (4%) in permeance was observed for the coated membranes, attributable to the nanometric coating thickness, surface charge, and hydrophilic nature of the coated layer. The coated membranes exhibited charge specific adsorption driven by electrostatic interaction combined with rejection due to size exclusion (MWCO 530 kDa that correspond to a size of ∼35–40 nm). Furthermore, a significant reduction in organic fouling and biofouling was found for T-CNF/PVA coated membranes when exposed to BSA and E. coli. The results demonstrate the potential of simple modifications using nanocellulose to manipulate the pore structure and surface chemistry of commercially available membranes without compromising on permeability and mechanical stability.

Crosslinked cellulose nanofiber-polyvinyl alcohol antifouling membrane.     

Fly ash geopolymer as a coating material for controlled-release fertilizer based on granulated urea

Nitrogen loss from urea fertiliser due to its high solubility characteristics has led to the invention of controlled release urea (CRU). Majority of existing CRU coatings are produced from a non-biodegradable, toxic and expensive synthetic polymers. This study determines the feasibility of fly ash-based geopolymer as a coating material for urea fertilizer. The effects of fly ash particle size (15.2 μm, 12.0 μm, and 8.6 μm) and solid to liquid (S : L) ratio (3 : 1, 2.8 : 1, 2.6 : 1, 2.4 : 1 and 2.2 : 1) on the geopolymer coating, the characterization such as FTIR analysis, XRD analysis, surface area and pore size analysis, setting time analysis, coating thickness, and crushing strength, and the release kinetics of geopolymer coated urea in water and soil were determined. Lower S : L ratio was beneficial in terms of workability, but it had an adverse impact on geopolymer properties where it increased porosity and decreased mechanical strength to an undesirable level for the CRU application. Geopolymer coated urea prepared from the finest fly ash fraction and lowest S : L ratio demonstrated high mechanical strength and slower urea release profile. Complete urea release was obtained in 132 minutes in water and 15 days in soil from geopolymer-coated urea whereas for uncoated urea it took only 20 minutes in water and 3 days in soil. Thus, geopolymer can potentially be used as a coating material for urea fertilizer to replace commonly used expensive and biodegradable polymer-based coatings.

The effect of fly ash particle size and solid to liquid ratio on the performance of geopolymer as a coating material for controlled release urea was investigated. Geopolymer coated urea completely released in 132 minutes in water and 15 days in soil.     

Anticorrosive behavior of a zinc-rich epoxy coating containing sulfonated polyaniline in 3.5% NaCl solution

An epoxy zinc-rich composite coating containing self-doped conducting sulfonated polyaniline (SPANi) nanofiber was prepared and the corrosion resistance of as-prepared coatings on Q235 substrate studied by open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and scanning vibrating electrode technique (SVET). Results suggested that a zinc-rich coating with addition of 1.0 wt% SPANi could enhance the cathodic protection time and barrier performance. To study corrosion diffusion, artificial scratch and adhesion strength were investigated via the salt spray test and pull-off test, respectively. Finally, the passivating action of coatings was demonstrated by analyses of corrosion products via X-ray diffraction spectroscopy.

An epoxy zinc-rich composite coating containing self-doped conducting sulfonated polyaniline nanofiber was prepared and the corrosion resistances of as-prepared coatings on Q235 substrate was studied by OCP, EIS and SVET.     

Degradation and biocompatibility of a series of strontium substituted hydroxyapatite coatings on magnesium alloys

There has been a surge in the research on magnesium (Mg) alloys as a promising selection for biomaterials application. However, as a foremost drawback, the fast degradation of Mg alloys limits its clinical use. In this study, a series of Sr-HA coatings with the Sr content ranging between 10–100% were prepared on Mg alloys, in order to control the degradation and enhance the osteoblast response. Microstructure analysis indicated the formation of Ca_10−xSr_x(PO₄)₆(OH)₂ coatings with the thickness ranging between 28–35 μm. The degradation results suggested that an increase in the Sr content in the coatings led to the decreasing degradation rate of the Sr-HA coated Mg. 100% Sr-HA coatings provided the best corrosion protective effect with nearly no hydrogen evolution during 10 days'' immersion in Hank''s solution. The in vitro cell biocompatibility was evaluated with MC3T3-E1 osteoblasts using the extract assay. In each case the released Sr affected the osteoblast proliferation and the expression of osteogenesis markers including, ALP, Col-I and RUNX2, in a Sr concentration-dependent manner. These results suggest that Sr-HA coating is a promising combination for controlling the degradation and enhancing the cytocompatibility of Mg alloys. The degradation and osteoblast response could be simply controlled through the adjustment of Sr content in the coatings.

Sr-HA coatings could simply improve the degradation and osteoblast response of Mg in a Sr-dose dependent manner.     

Functionalized aliphatic polyketones with germicide activity

The COVID-19 pandemic has further confirmed to the community that direct contact with contaminated surfaces and objects represents an important source of pathogen spreading among humans. Therefore, it is of paramount importance to design effective germicidal paints to ensure a rapid and potent disinfectant action of surfaces. In this work, we design novel germicide polymeric coatings by inserting quaternary ammonium and sugar groups on the macromolecular backbone, thus respectively endowing the polymer with germicide features and hydrophilicity to interact with the surfaces. An aliphatic polyketone was selected as a starting polymer matrix that was functionalized with primary amine derivatives via the Paal–Knorr reaction. The resulting polymers were deposited on cellulose filter papers and checkboard charts with excellent coating yield and substrate coverage as determined by scanning electron microscopy for cellulose. Remarkably, the substrates coated by the functional polymers bearing quaternary ammonium compounds showed excellent bactericide properties with antibacterial rate of 99% and logarithmic reduction of >3. Notably, the polymers with higher hydrophobicity showed better retention on the substrate after being treated with water at neutral pH.

Surfaces coated by polyketones bearing quaternary ammonium compounds showed excellent bactericidal properties with antibacterial rate of 99%.