Release Of Zn Ions Research Articles

Atomic scale investigation and cytocompatibility of copper and zinc-loaded phosphate-based glasses prepared by coacervation

Phosphate-based glasses (PBGs) are bioresorbable materials that find application in the field of controlled drug delivery and tissue engineering. The structural arrangements of the phosphate units in PBGs, along with the knowledge of how therapeutic metallic ions are embedded in the phosphate network are important in understanding the degradation and targeted release properties of these materials. Using a combination of Raman spectroscopy, high-energy X-ray diffraction and 31P and 23Na solid-state magic angle spinning nuclear magnetic resonance, the atomic structure of coacervate PBGs in the system P2O5-CaO-Na2O-MOx (M = Cu or Zn) with loadings of 2, 10 and 15 mol % of M2+ have been studied as functions of composition and calcination temperature. After drying at room temperature, the structures of the phosphate network in PBG-Cu and PBG-Zn are quite similar, with that of PBG-Zn exhibiting slightly higher connectivity. Heating at 300 °C causes degradation of the polyphosphate chains, even though Q2 species remain predominant. X-ray photoelectron spectroscopy demonstrates that Cu in calcined PBGs is present in both oxidation states +1 and +2, with a predominance of the +2 state. Cu and Zn ion release data after 24 h exposure of PBGs in deionized water and cell medium DMEM show that release is proportional to their loadings. Cytotoxicity MTT assays of dissolution products of PBG-Cu/ZnX calcined at 300 °C on human osteosarcoma cells (MG-63) and on human skin cells (HaCaTs) showed good cellular response for all compositions, indicating that PBGs have great potential for both hard and soft tissue regeneration.

Role of graphene in bactericidal activity and bioactivity of a Zn/graphene/chitosan coating

The antibacterial ability of an implant is governed by the interaction between the surface of the material and the cells. Nanosized features that promote bacterial killing were achieved through synthesizing a Zn/graphene/chitosan surface on a NiTi alloy. The surface morphology and microstructure of the Zn/graphene/chitosan surfaces were observed, and their antibacterial behavior was investigated. The Zn/graphene/chitosan surface exhibited 93 % antibacterial activity against Staphylococcus aureus (S. aureus), which was higher than the Zn/chitosan surface (67 %), and it inhibited bacterial adhesion. This was attributed to the fast release of Zn ions from the Zn/graphene/chitosan surfaces and the sharp morphology of graphene on the surface. In addition, the adhesion of the Zn/graphene/chitosan coating increased with the amount of graphene content. This finding suggests that the synergy of graphene improves the antibacterial ability, bioactivity, and adhesion of Zn-containing coatings.

Corrosion Resistance of Biodegradable Zinc Surfaces Enhanced by UV-Grafted Polydimethylsiloxane Coating.

Improved living conditions have led to an increase in life expectancy worldwide. However, as people age, the risk of vascular disease tends to increase due to the accumulation and buildup of plaque in arteries. Vascular stents are used to keep blood vessels open. Biodegradable stents are designed to provide a temporary support vessel that gradually degrades and is absorbed by the body, leaving behind healed blood vessels. However, biodegradable metals can suffer from reduced mechanical strength and/or inflammatory response, both of which can affect the rate of corrosion. Therefore, it is essential to achieve a controlled and predictable degradation rate. Here, we demonstrate that the corrosion resistance of biodegradable Zn surfaces is improved by electroless deposition of zinc hydroxystannate followed by UV-grafting with silicone oil (PDMS). Potentiodynamic polarization, electrochemical impedance spectroscopy, respiratory kinetic measurements, and long-term immersion in three simulated body fluids were applied. Although zinc hydroxystannate improves the corrosion resistance of Zn to some extent, it introduces a high surface area with hydroxyl units used to UV-graft PDMS molecules. Our results demonstrate that hydrophobic PDMS causes a 3-fold reduction in corrosion of Zn-based materials in biological environments and reduces cytotoxicity through the uncontrolled release of Zn ions.

Selective ion doping core-shell bioceramic fiber-derived granules readily tuning biodegradation and initiating osteoporotic bone defect repair

Osteoporotic bone defect repair is one of the challenges in orthopedics because there are no preferable biomaterials to readily initiate new bone regeneration in critical-size pathological bone damage. Our previous studies revealed that core–shell Ca-phosphate/silicate microspheres can tune time-evolving biodegradation, which is beneficial for modulating bone repair. Herein, we expanded this strategy to develop core–shell-type 5 % Sr- and 8 % Zn-doped wollastonite fiber-derived granules with different porosities (0 %, 10 %, 20 %) in the shell layer. Physicochemical analyses indicated that granules with higher porosity in the shell layer exhibited more appreciable Sr and Zn ion release and biodissolution in vitro. Osteoporotic femoral bony defects in rabbits were used to verify the osteogenic efficacy of the core–shell granules. The granules with 10 % porosity could initiate more osteogenesis within 6 weeks, and the new bone tissue could grow into the defect region, while the new bone tissue only migrated into the periphery pores under the other granule conditions. Histological evaluation also revealed appreciable new bone ingrowth in the granules with 10 % porosity, whereas the other implant groups had limited new bone tissue. These findings demonstrate that bone repair initiation can be enhanced by finely designed local porosity in specific components of core–shell bioceramic fiber-tailoring granules to control bioactive ion release and osteo-stimulation in vivo; moreover, such bioceramic fabrication is promising for developing osteo-stimulative implants to resolve clinically challenging bone defect repair.

Osteogenerative and corrosion-decelerating teriparatide-mediated strontium–zinc phosphate hybrid coating on biodegradable zinc–copper alloy for orthopaedic applications

Zinc–copper (ZnCu) alloys recently showed great potential as biodegradable materials for bone implants thanks to their excellent mechanical strength, biosafety, and promising bioactivities. However, bare ZnCu alloys exhibited poor cytocompatibility and osteointegration. Moreover, the biological functions of ZnCu remain to be corroborated. Herein, the teriparatide (PTH)-mediated strontium–zinc phosphate (SrZnP) organic–inorganic hybrid coating was fabricated on the surface of ZnCu substrate via a chemical conversion method to contain the release of Zn ions and improve biofunctionality in osteogenesis. The characteristics of the hybrid coating were optimised by adjusting the amount of PTH molecules added. A dense and homogenous coating with micellar crystal micro-/nano-structure was obtained. The coated samples showed a significantly decreased corrosion rate and a more uniform corrosion mode, effectively suppressing the release of Zn2+. Additionally, the coated ZnCu enhanced the proliferation of bone marrow mesenchymal stem cells (BMSCs), promoted the expression of alkaline phosphatase and the formation of calcium nodules, and upregulated the levels of osteogenic-related genes. More important, the hybrid coating activated the classic osteogenic signalling pathway of BMP-2/Smad1/Runx2 and Sirt1/Runx2 to induce the osteogenic differentiation of BMSCs. These appealing features can be mainly attributed to the constituents of released Zn2+, Sr2+, and PTH molecules in the control, as well as the unique topographical characteristics of the coatings. Taken together, the PTH&SrZnP hybrid coating could be a promising option for surface modification of biodegradable metallic Zn for orthopaedic applications.

Dual antibacterial/antiviral performance of ZIFs for highly contaminated sanitary surfaces

Effective antimicrobial activity on highly contaminated surfaces, like in sanitary, requires the development of novel functional nanomaterials. In this work, we synthesized zeolitic imidazolate frameworks (ZIFs, 7 and 8) and validated their dual antibacterial/antiviral activity for real applications in sanitary. ZIF-7 and ZIF-8 presented the polygonal morphology associated with the organic ligand arrangement with a crystalline sodalite conformation, and significant surface area (SA) differences were found (38 vs. 1456 m2/g) and associated with particle agglomeration in ZIF-7. The in-vitro antibacterial performance indicated that the high SA of ZIF-8 enabled activity at early and late interaction stages promoted by the controlled Zn ion release in solution. Similarly, ZIF-8 induces the HSV1 virus inactivation during the host infection, demonstrating a high antiviral performance (ca. 96 %). This was also validated when depositing onto flush buttons and door handles in a sanitary.

Study of synergetic effect between BODIPY and ZnO on visible light-enhanced antibacterial activity

High incidence of bacterial infections and the growing of drug-resistant bacteria to conventional antibiotics have become great concerns. Developing new antibacterial agents and methods to inhibit bacterial-resistance have attracted great research interest. Due to their multiple antibacterial mechanisms, light-induced antibacterial materials are promising to combat antibiotic-resistant bacteria. In the present work, visible light response ZnO-based nanocomposite (BIN-ZnO) was prepared by nano-ZnO modified with a novel boron dipyrromethene photosensitizer (BIN) via simple coordination-driven self-assembly reaction. Compared with the individual BIN and ZnO, BIN-ZnO shows higher visible light-enhanced antibacterial activity against E. coli and S. aureus. This is attributed to the synergism between BIN and ZnO, which overcome high aggregation of BIN and insensitivity to visible light of ZnO. And The antibacterial mechanism study indicates that synergism between BIN and ZnO increases ROS yields and accelerates release of Zn ions, which is beneficial for higher antibacterial activity.

A novel biodegradable nanocrystalline Zn alloy with exceptional biocompatible and antibacterial properties

The development of biodegradable Zn alloys with comprehensive performance for biomedical applications is still challenging. Hence, the nanocrystalline Zn–Cu–Sr–Li alloys were prepared by alloying design and multi-pass high-speed hot rolling. The Zn–3Cu-0.2Sr-0.4Li alloy achieved nanoscale microstructures, resulting in high strength and an ideal corrosion rate that is more suitable for tissue repair cycles. Scanning Kelvin probe force microscopy analysis revealed the potential from high to low was ranked as: ε phase > SrZn13 phase > Zn grains > β phase. The nanoscale Zn grains and β particles formed numerous microcells, enhancing the microgalvanic corrosion effect. The Sr ions could be released more efficiently during the degradation in Li-containing alloys, which endowed the alloys with outstanding biocompatibility. Besides, the synergistic release of Zn ions and Cu ions during alloy degradation endowed the alloy with excellent antimicrobial ability against Staphylococcus aureus (inhibition zone diameter ≈ 7.5 mm). The antimicrobial ability of Zn–3Cu–0.2Sr–0.4Li alloy was superior among the reported biodegradable Zn alloys. These results demonstrated nanocrystalline Zn–Cu–Sr–Li alloys have comprehensive performance and broad application prospects in biodegradable bone implants, providing the experimental and theoretical basis for future research in the biomedical field.

Microstructure development of AM-fabricated pure Zn with heat-treatment and its mechanical properties, degradation behavior, and biocompatibility

The fabrication of zinc (Zn) parts devoid of inherent defects through Powder Bed Fusion-Laser Beam (PBF-LB) remains a formidable challenge. This study focuses on the optimization of process parameters and the implementation of tailored heat treatment to achieve high-performance PBF-LB fabricated (PBF-LBed) pure Zn bulk and scaffolds. Microstructural analysis, residual stress assessment, mechanical property testing, electrochemical experiments, immersion tests, in vitro and in vivo evaluations were conducted. The research results revealed that, under optimized process parameters and subsequent annealing, the yield strength, ultimate tensile strength, and ductility of PBF-LBed parts exhibit remarkable enhancements. Concurrently, the grain size was refined to 3 μm, accompanied by a notable improvement in biocompatibility. It could be roughly concluded that the microstructure refinement obtained through the heat treatment could significantly enhance their mechanical and electrochemical performances. Meanwhile, an appropriate Zn ion release rate achieved through grain refinement might created a more conducive microenvironment for new bone formation. Consequently, heat-treated PBF-LBed pure Zn scaffolds exhibits superior performance and application potential compared to untreated scaffolds.

Analysis of Antibacterial and Antiviral Properties of ZnO and Cu Coatings Deposited by Magnetron Sputtering: Evaluation of Cell Viability and ROS Production

The development and testing of antimicrobial coatings continues to be a crucial approach, considering the ongoing emergence of antibiotic-resistant bacteria and the rapid transmission of highly pathogenic viruses. In this study, three types of coatings—pure metallic copper (Cu), zinc oxide (ZnO), and a three-layer zinc oxide and copper mixed coating (ZnO/Cu/ZnO)—were deposited by magnetron sputtering on polyethylene terephthalate substrates to evaluate their antimicrobial potential using various microorganisms, including viruses. Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli bacteria were used for the assessment of antibacterial properties. Antiviral testing was performed using MS2 bacteriophage and replication-deficient Semliki Forest virus, both representing single-stranded RNA-containing viruses. The samples’ ability to cause reactive oxygen species formation was measured, and the effect on bacterial metabolic activity was evaluated. Cu-coated samples showed high inhibitory activity (>95%) against E. coli and S. aureus bacteria, as well as against tested viruses (SFV and MS2). The antibacterial and antiviral properties of ZnO/Cu/ZnO and ZnO coatings were not significant. Although ZnO/Cu/ZnO and ZnO caused inhibition of the metabolic activity of the bacteria, it was insufficient for complete bacteria eradication. Furthermore, significant reactive oxygen species (ROS) production was detected only for single Cu-coated samples, correlating with the strong bacteria-killing ability. We suppose that the ZnO layer exhibited a low release of Zn ions and prevented contact of the Cu layer with bacteria and viruses in the ZnO/Cu/ZnO coating. We conclude that current ZnO and Cu-ZnO-layered coatings do not possess antibacterial and antiviral activity.

Trimetal-based nanomaterials induced toxicity to plants: Does it differ from the toxicity of mixed and single-element nanoparticles?

Advanced materials comprising multiple metal alloys have made their way into the market. Trimetal-based nanomaterials (TNMs) are an example of advanced materials which have gained significant traction and are now employed in a wide array of products. It is essential to raise the question if the toxicity of advanced nanomaterials like TNMs differs from the joint effects as manifested by exposure to the single component nanoparticles (NPs). To answer this question, a trimetal-based nanomaterial: bismuth cobalt zinc oxide (BiCoZnO) was tested. This TNM had a mass ratio of 90 % ZnO NPs, 7 % Bi2O3 NPs and 3 % Co3O4 NPs. Nanoparticle-exposed lettuce seedlings (Lactuca sativa L.) showed decreases in relative root elongation (RRE) and biomass production after 21 days of exposure. The 50 % of maximal effective concentration (EC50) value of the TNMs for biomass production was 1.2 mg L−1 when the exposure period was 240 h. This is of the same magnitude as the EC50 values found for ZnO NPs (EC50 = 1.5 mg L−1) and for the mixture of components NPs (MCNPs) which jointly form the TNMs (EC50 = 3.7 mg L−1) after 10 d of exposure. The inhibition of plant root elongation by the TNMs was partially (65 %) attributed to the release of Zn ions, with the actual concentration of released Zn ions being lower in TNMs compared to the actual concentration of Zn ions in case of ZnO NPs. It is therefore to be concluded that the concentration of Zn ions cannot be used as a direct measure to compare the toxicity between traditional and advanced Zn-related nanomaterials. The EC50 values could be assessed within a factor of two; which is helpful when developing advanced alloy nanomaterials and assessing prospective the effects of trimetal-based nanomaterials.

Surface Defect Mediated Interactions of Bacterial Growth Media on Microcrystalline ZnO

Nano- and microscale ZnO exhibits significant potential in biomedical applications as an antibacterial agent. This is attributed to the selective toxicity and growth inhibition for a wide range of both Gram-positive and Gram-negative bacteria as well as for microbial strains resistant to traditional antibiotics. Pursuit of novel bactericidal applications, however, is inhibited by uncertainty surrounding the underlying mechanisms of the observed antimicrobial action. The most common suggested mechanisms include generation of various reactive oxygen species, release of Zn ions and surface-surface interactions between the bacterial cell wall and free crystalline surface of ZnO. Recent work has placed an emphasis on the role of the free crystalline surface in bacterial growth inhibition. Additionally, the cytotoxicity of ZnO particles has long been known to be heavily dependent on environmental conditions, yet detailed descriptions of these phenomena are lacking. Herein we investigate the effects of interactions with both bacteria and the bacterial environments on the physicochemical and optoelectronic properties of the free crystalline surface of ZnO microparticles (MPs). This is done to gain insight into the nature of interactions with the bacterial growth media and the influence such interactions have on bacterial growth inhibition. Hereby, we expose hydrothermally grown ZnO MPs to phosphate-buffered saline (PBS) media both with and without the presence of Newman strain S. aureus bacteria. The surface electronic structure and charge dynamics are probed via both time and energy dependent surface photovoltage (SPV) conducted prior to and following minimum inhibitory concentration assays. We demonstrate significant changes in the characteristic timescales of long-lived processes in the SPV transients after exposure to phosphate-rich environments. We also note that the presence of bacteria has an impact on shorter lived processes and suppresses the effect of media at longer timescales. The SPV spectra point to a significant adsorption of phosphate compounds on the crystalline surface. We also demonstrate changes in the electronic structure as a result of exposure to PBS.

Review of Zinc Oxide Nanoparticles: Toxicokinetics, Tissue Distribution for Various Exposure Routes, Toxicological Effects, Toxicity Mechanism in Mammals, and an Approach for Toxicity Reduction.

Zinc oxide (ZnO) nanoparticles (NPs) are widely used as a sunscreen, antibacterial agent, dietary supplement, food additive, and semiconductor material. This review summarizes the biological fate following various exposure routes, toxicological effects, and toxicity mechanism of ZnO NPs in mammals. Furthermore, an approach to reduce the toxicity and biomedical applications of ZnO NPs are discussed. ZnO NPs are mainly absorbed as Zn2+ and partially as particles. Regardless of exposure route, elevated Zn concentration in the liver, kidney, lungs, and spleen are observed following ZnO NP exposure, and these are the target organs for ZnO NPs. The liver is the main organ responsible for ZnO NP metabolism and the NPs are mainly excreted in feces and partly in urine. ZnO NPs induce liver damage (oral, intraperitoneal, intravenous, and intratracheal exposure), kidney damage (oral, intraperitoneal, and intravenous exposure) and lung injury (airway exposure). Reactive oxygen species (ROS) generation and induction of oxidative stress may be a major toxicological mechanism for ZnO NPs. ROS are generated by both excess Zn ion release and the particulate effect resulting from the semiconductor or electronic properties of ZnO NPs. ZnO NP toxicity can be reduced by coating their surface with silica, which prevents Zn2+ release and ROS generation. Due to their superior characteristics, ZnO NPs are expected to be used for biomedical applications, such as bioimaging, drug delivery, and anticancer agents, and surface coatings and modification will expand the biomedical applications of ZnO NPs further.

Fabrication of a New Hyaluronic Acid/Gelatin Nanocomposite Hydrogel Coating on Titanium-Based Implants for Treating Biofilm Infection and Excessive Inflammatory Response

Persistent inflammation caused by implant-associated biofilm infections has emerged as a significant clinical issue. While many methods have been developed to give implants great anti-biofilm benefits, the post-inflammatory microenvironment is frequently disregarded. Oxidative stress (OS) due to excessive reactive oxygen species (ROS) is considered to be one of the specific physiological signals of the inflammation microenvironment. Herein, ZIF-90-Bi-CeO2 nanoparticles (NPs) were incorporated into a Schiff-base chemically crosslinked hydrogel composed of aldehyde-based hyaluronic acid and gelatin. Through chemical crosslinking between polydopamine and gelatin, the hydrogel coating adhered to the Ti substrate. The modified Ti substrate gained multimodal antibacterial and anti-biofilm functions, which were attributed to the photothermal effect of Bi NPs, and the release of Zn ions and CeO2 NPs. Notably, CeO2 NPs endowed the system with dual-enzyme (SOD- and CAT-like) catalytic activities. In a rat implant-associated infection (IAI) model, the dual-functional hydrogel had a biofilm-removal ability and regulated OS and inflammatory responses to facilitate osseointegration. The photothermal therapy combined with a host inflammation-microenvironment regulation strategy might provide a novel treatment for biofilm infection and the accompanying excessive inflammation.

Three-Dimensional Printing of Poly-L-Lactic Acid Composite Scaffolds with Enhanced Bioactivity and Controllable Zn Ion Release Capability by Coupling with Carbon-ZnO

Poly-L-lactic acid (PLLA) has gained great popularity with researchers in regenerative medicine owing to its superior biocompatibility and biodegradability, although its inadequate bioactivity inhibits the further use of PLLA in the field of bone regeneration. Zinc oxide (ZnO) has been utilized to improve the biological performance of biopolymers because of its renowned osteogenic activity. However, ZnO nanoparticles tend to agglomerate in the polymer matrix due to high surface energy, which would lead to the burst release of the Zn ion and, thus, cytotoxicity. In this study, to address this problem, carbon-ZnO (C-ZnO) was first synthesized through the carbonization of ZIF-8. Then, C-ZnO was introduced to PLLA powder before it was manufactured as scaffolds (PLLA/C-ZnO) by a selective laser sintering 3D printing technique. The results showed that the PLLA/C-ZnO scaffold was able to continuously release Zn ions in a reasonable range, which can be attributed to the interaction of Zn-N bonding and the shielding action of the PLLA scaffold. The controlled release of Zn ions from the scaffold further facilitated cell adhesion and proliferation and improved the osteogenic differentiation ability at the same time. In addition, C-ZnO endowed the scaffold with favorable photodynamic antibacterial ability, which was manifested by an efficient antibacterial rate of over 95%.

Creation of Bioactive Ceramic Composite Coatings on Zn–Mn–Mg Alloy via Micro-arc Oxidation and Hydrothermal Treatment for Orthopedic Implant Applications

Zinc alloys have emerged as promising biodegradable metals thanks to their critical physiological roles and encouraging degradation behavior. In this study, calcium phosphate (CaP) coatings were made on micro-arc oxidized Zn alloy using hydrothermal treatment (HT), which was motivated by the CaP-based minerals in natural bone tissue. The coating morphology was optimized by controlling the HT time, resulting in a homogeneous micro-CaP coating structure. The CaP coating significantly increased the cell viability and adhesion of MC3T3-E1 preosteoblasts and L-929 cells. Compared with the control group, the cell toxicity of the samples after MAO-HT was less, the number of cells was more, and the morphology was complete. Cell adhesion showed that the distribution of cells increased with the increase of HT time. In addition, the CaP coating significantly reduced the Zn ion release from the bulk material during the degradation process, resulting in a much lower Zn concentration and pH change in the surrounding environment. The micro-CaP coating structure and the regulated release of zinc ions are primarily responsible for the enhanced cytocompatibility and biomineralization of CaP-coated Zn biomaterials. In summary, the CaP coating on Zn-based biomaterial appears to be a viable approach to enhance its biocompatibility and to control its degradation rate. After that, the biocompatibility of the material can be improved by controlling the surface morphology of the material to adapt to the complex human environment.

Calcium-Zinc Phosphate Chemical Conversion Coating Facilitates the Osteointegration of Biodegradable Zinc Alloy Implants by Orchestrating Macrophage Phenotype.

Zinc (Zn) alloys provide a new generation for orthopedic applications due to their essential physiological effects and promising degradation properties. However, excessive release of Zn ions (Zn2+ ) during degradation and the severe inflammatory microenvironment are not conducive to osseointegration, which is determined by the characteristics of the implant surface. Therefore, it is essential to modulate the release rate of Zn alloys by surface modification technology and endow them with anti-inflammatory and osteogenic effects. In this study, two kinds of phosphate chemical conversion (PCC) coatings with different compositions and morphological structures are prepared, namely Zn-P (with disk-like crystals) and Ca-Zn-P (with lamellar crystals). Although all the PCC-coated Zn implants have low cytotoxicity, Ca-Zn-P show better osteoimmunomodulation effects in several aspects: the induction of the M2-phenotype macrophage polarization and thus promotion of osteogenesis in vitro; the regulation of the bone immune microenvironment which is conducive to tissue regeneration and osseointegration in vivo; and the release of ions (through PI3K/AKT and Wnt signaling pathways) and the morphological structures (through RhoGTPase signaling pathways) act as possible mechanisms of M2 polarization. The Ca-Zn-P coating can be considered to provide new insights into bone immunomodulation and osseointegration.

Zinc Ion-crosslinked polycarbonate/heparin composite coatings for biodegradable Zn-alloy stent applications

Zinc and its alloys are the best candidates for biodegradable cardiovascular stents due to their good corrosion rate and biocompatibility in vasculature. However, the cytotoxicity caused by the rapid release of zinc ions during the initial degradation stage and the lack of an anticoagulant function are huge challenges for their practical clinical applications. In this work, we developed a zinc ion-crosslinked polycarbonate/heparin composite coating via electrophoretic deposition (EPD) to improve the biocompatibility and provide anticoagulant functions for Zn-alloy stents. Both electrochemical tests and in vitro immersion tests demonstrated an enhanced corrosion resistance and lower Zn ion release rate of the coated Zn alloys. Enhanced adhesion and proliferation of endothelial cells on coated Zn alloys were also observed, indicating faster reendothelialization than that on bare Zn alloys. Moreover, the surface erosion of the composite coating led to the uniform and long-term release of heparin, which remarkably inhibited the adhesion and activation of platelets, and may have endowed the coated Zn-alloy stents with long-term anticoagulant functions.

Effect of reaction time on the microstructure and properties of in-situ hopeite chemical conversion coatings formed by self-corrosion on zinc alloy

Zinc (Zn) and its alloys are considered as promising biodegradable metals due to its suitable degradability and important physiological functions. However, in the process of degradation, excessive release of Zn ions (Zn2+) will significantly affect the cytocompatibility and antibacterial properties. Surface modification technology can not only control the corrosion behavior of biodegradable metals but also improve its biocompatibility and antibacterial properties according to clinical requirements. In this study, an in-situ hopeite (HP, Zn3(PO4)2·4H2O) coating was prepared on Zn alloy by phosphate chemical conversion (PCC) method using Zn2+ provided by self-corrosion of the substrates. And the effect of phosphating time on the microstructure, phase composition, corrosion resistance, and wettability of HP coatings was investigated. The results showed that a complete HP coating was formed on the Zn alloy after reaction for 1 min, even if Zn2+ were supplied by self-corrosion without an additional Zn source. It also revealed that the reaction time had a marked impact on the morphologies and microstructures of the HP coating. The electrochemical test results proved that the prepared HP coatings had obvious protection on the Zn alloy and could regulate the corrosion rate of the substrate. Meanwhile, the Zn alloy modified by the PCC method also possessed excellent hydrophilicity. These primary findings might support new opportunities in the exploration of controllable coatings on biomedical Zn alloys.

Hazard profiling of a combinatorial library of zinc oxide nanoparticles: Ameliorating light and dark toxicity through surface passivation

Zinc oxide (ZnO) is one of the high-volume production nanoparticles (NPs) currently used in a wide range of consumer and industrial goods. The inevitable seepage into environmental matrices and the photoactive nature of ZnO NPs warrants hazard profiling under environmentally related conditions. In this paper, the influence of simulated solar light (SSL) on dissolution behaviour and phototoxicity of ZnO NPs was studied using a combinatorial library of ZnO NPs with different sizes, surface coatings, dopant chemistry, and aspect ratios in a fish cell line (BF2) and zebrafish embryos. Generally, the cytotoxicity and embryo mortality increased when exposed concomitantly to SSL and ZnO NPs. The increase in toxic potential of ZnO NPs during SSL exposure concurred with release of Zn ions and ROS generation. Surface modification of NPs with poly(methacrylic acid) (PMAA), silica or serum coating decreased toxicity and ZnO with serum coating was the only NP that had no significant effect on any of the cytotoxicity parameters when tested under both dark and SSL conditions. Results from our study show that exposure to light could increase the toxic potential of ZnO NPs to environmental lifeforms and mitigation of ZnO NP toxicity is possible through modifying the surface chemistry.