Recent Advances in Metal-Based Antimicrobial Coatings for High-Touch Surfaces.

International interest in metal-based antimicrobial coatings to control the spread of bacteria, fungi, and viruses via high contact human touch surfaces are growing at an exponential rate. This interest recently reached an all-time high with the outbreak of the deadly COVID-19 disease, which has already claimed the lives of more than 5 million people worldwide. This global pandemic has highlighted the major role that antimicrobial coatings can play in controlling the spread of deadly viruses such as SARS-CoV-2 and scientists and engineers are now working harder than ever to develop the next generation of antimicrobial materials. This article begins with a review of three discrete microorganism-killing phenomena of contact-killing surfaces, nanoprotrusions, and superhydrophobic surfaces. The antimicrobial properties of metals such as copper (Cu), silver (Ag), and zinc (Zn) are reviewed along with the effects of combining them with titanium dioxide (TiO2) to create a binary or ternary contact-killing surface coatings. The self-cleaning and bacterial resistance of purely structural superhydrophobic surfaces and the potential of physical surface nanoprotrusions to damage microbial cells are then considered. The article then gives a detailed discussion on recent advances in attempting to combine these individual phenomena to create super-antimicrobial metal-based coatings with binary or ternary killing potential against a broad range of microorganisms, including SARS-CoV-2, for high-touch surface applications such as hand rails, door plates, and water fittings on public transport and in healthcare, care home and leisure settings as well as personal protective equipment commonly used in hospitals and in the current COVID-19 pandemic.

Chemically Engineered Porous Molecular Coatings as Reactive Oxygen Species Generators and Reservoirs for Long-Lasting Self-Cleaning Textiles.

Wearable personal protective equipment that is decorated with photoactive self-cleaning materials capable of actively neutralizing biological pathogens is in high demand. Here, we developed a series of solution-processable, crystalline porous materials capable of addressing this challenge. Textiles coated with these materials exhibit a broad range of functionalities, including spontaneous reactive oxygen species (ROS) generation upon absorption of daylight, and long-term ROS storage in dark conditions. The ROS generation and storage abilities of these materials can be further improved through chemical engineering of the precursors without altering the three-dimensional assembled superstructures. In comparison with traditional TiO2 or C3 N4 self-cleaning materials, the fluorinated molecular coating material HOF-101-F shows a 10- to 60-fold enhancement of ROS generation and 10- to 20-fold greater ROS storage ability. Our results pave the way for further developing self-cleaning textile coatings for the rapid deactivation of highly infectious pathogenic bacteria under both daylight and light-free conditions.

A peptide-based coating toolbox to enable click chemistry on polymers, metals, and silicon through sortagging.

A versatile peptide-based toolbox for surface functionalization was established by a combination of a universal material binding peptide (LCI-anchor peptide) and sortase-mediated bioconjugation (sortagging). This toolbox facilitates surface functionalization either as a one- or a two-step strategy. In the case of the one-step strategy, the desired functionality was directly introduced to LCI. For the two-step strategy, LCI was modified with a reactive group, which can be further functionalized (e.g., employing "click" chemistry). Sortagging of LCI, employing sortase A from Staphylococcus aureus, was achieved with six different amine compounds: dibenzocyclooctyne amine, biotin-polyethylene glycol amine, Cyanine-3 amine, kanamycin, methoxypolyethylene glycol amine (Mn = 5000 Da), and 2,2,3,3,4,4,4-Heptafluorobutylamine. The purification of LCI-amine sortagging products was performed by a negative purification using Strep-tag II affinity chromatography, resulting in LCI-amine conjugates with purities >90%. For the two-step strategy, the LCI-dibenzocyclooctyne sortagging product was purified and enabled, through copper-free azide-alkyne "click" chemistry, universal surface functionalization of material surfaces such as polypropylene, polyethylene terephthalate, stainless steel, gold, and silicon. The click reaction was performed before or after surface binding of LCI-dibenzocyclooctyne. Finally, in the case of the one-step strategy, polypropylene was directly functionalized with Cyanine-3 and biotin-polyethylene glycol amine.

In vivo biocompatibility of diamond-like carbon films containing TiO2 nanoparticles for biomedical applications.

Hybrid diamond-like carbon (DLC) with incorporated titanium dioxide (TiO2) nanoparticle coatings have low friction coefficient, high wear resistance, high hardness, biocompatibility, and high chemical stability. They could be employed to modify biomedical alloys surfaces for numerous applications in biomedical engineering. Here we investigate for the first time the in vivo inflammatory process of DLC coatings with incorporated TiO2 nanoparticles. TiO2-DLC films were grown on AISI 316 stainless-steel substrates using plasma-enhanced chemical vapor deposition. The coated substrates were implanted in CF1 mice peritoneum. The in vivo cytotoxicity and biocompatibility of the samples were analyzed from macrophage lavage. Analysis in the first weeks after implantation could be helpful to evaluate the acute cytotoxicity generated after a possible inflammatory process. The in vivo results showed no inflammatory process. A significant increase in nitric oxide production on the uncoated substrates was confirmed through cytometry, and the coated substrates demonstrated biocompatibility. The presence of TiO2 nanoparticles enhanced the wound healing activity, due to their astringent and antimicrobial properties. DLC and TiO2-DLC coatings were considered biocompatible, and the presence of TiO2 nanoparticles reduced the inflammatory reactions, increasing DLC biocompatibility.

Enhanced model protein adsorption of nanoparticulate hydroxyapatite thin films on silk sericin and fibroin surfaces.

Hydroxyapatite coated metallic implants favorably combine the required biocompatibility with the mechanical properties. As an alternative to the industrial coating method of plasma spraying with inherently potential deleterious effects, sol-gel methods have attracted much attention. In this study, the effects of intermediate silk fibroin and silk sericin layers on the protein adsorption capacity of hydroxyapatite films formed by a particulate sol-gel method were determined experimentally. The preparation of the layered silk protein/hydroxyapatite structures on glass substrates, and the effects of the underlying silk proteins on the topography of the hydroxyapatite coatings were described. The topography of the hydroxyapatite layer fabricated on the silk sericin was such that the hydroxyapatite particles were oriented forming an oriented crystalline surface. The model protein (bovine serum albumin) adsorption increased to 2.62 µg/cm2 on the latter surface as compared to 1.37 µg/cm2 of hydroxyapatite on glass without an intermediate silk sericin layer. The BSA adsorption on glass (blank), glass/c-HAp, glass/m-HAp, glass/sericin/c-HAp, and glass/sericin/m-HAp substrates, reported as decrease in BSA concentration versus contact time.

Calcium hydroxyapatite nanoparticles as a reinforcement filler in dental resin nanocomposite.

The current study focuses on the fabrication of calcium hydroxyapatite (Ca10(PO4)6(OH)2) (HA) in a nanorange having whiskers- and cubic-shaped uniform particle morphology. The synthesized HA particles hold a promising feature as reinforcement fillers in dental acrylic resin composite. They increase the efficacy of reinforcement by length and aspect ratio, uniformity, and monodispersity. Therefore, the acrylic resin was reinforced with the as-synthesized monodispersed HA filler particles (0.2-1 Wt%). The presence of filler particles in the composite had a noticeable effect on the tribological and mechanical properties of the dental material. The morphological effect of HA particles on these properties was also investigated, revealing that cubic-shaped particles showed better results than whiskers. The as-fabricated composite (0.4 Wt%) of the cubic-shaped filler particles showed maximum hardness and improved antiwear/antifriction properties. Particle loading played its part in determining the optimum condition, whereas particle size also influenced the reinforcement efficiency. The current study revealed that particle morphology, particle size, uniformity, etc., of HA fillers, greatly influenced the tribological and mechanical properties of the acrylic resin-based nanocomposite. Improvement in the tribological properties of HA particle-reinforced acrylic resin composites (HA-acrylic resin) followed the trend as AR < CmC < WC < CC.

Bioactive glasses incorporating less-common ions to improve biological and physical properties.

Bioactive glasses (BGs) have been a focus of research for over five decades for several biomedical applications. Although their use in bone substitution and bone tissue regeneration has gained important attention, recent developments have also seen the expansion of BG applications to the field of soft tissue engineering. Hard and soft tissue repair therapies can benefit from the biological activity of metallic ions released from BGs. These metallic ions are incorporated in the BG network not only for their biological therapeutic effects but also in many cases for influencing the structure and processability of the glass and to impart extra functional properties. The "classical" elements in silicate BG compositions are silicon (Si), phosphorous (P), calcium (Ca), sodium (Na), and potassium (K). In addition, other well-recognized biologically active ions have been incorporated in BGs to provide osteogenic, angiogenic, anti-inflammatory, and antibacterial effects such as zinc (Zn), magnesium (Mg), silver (Ag), strontium (Sr), gallium (Ga), fluorine (F), iron (Fe), cobalt (Co), boron (B), lithium (Li), titanium (Ti), and copper (Cu). More recently, rare earth and other elements considered less common or, some of them, even "exotic" for biomedical applications, have found room as doping elements in BGs to enhance their biological and physical properties. For example, barium (Ba), bismuth (Bi), chlorine (Cl), chromium (Cr), dysprosium (Dy), europium (Eu), gadolinium (Gd), ytterbium (Yb), thulium (Tm), germanium (Ge), gold (Au), holmium (Ho), iodine (I), lanthanum (La), manganese (Mn), molybdenum (Mo), nickel (Ni), niobium (Nb), nitrogen (N), palladium (Pd), rubidium (Rb), samarium (Sm), selenium (Se), tantalum (Ta), tellurium (Te), terbium (Tb), erbium (Er), tin (Sn), tungsten (W), vanadium (V), yttrium (Y) as well as zirconium (Zr) have been included in BGs. These ions have been found to be particularly interesting for enhancing the biological performance of doped BGs in novel compositions for tissue repair (both hard and soft tissue) and for providing, in some cases, extra functionalities to the BG, for example fluorescence, luminescence, radiation shielding, anti-inflammatory, and antibacterial properties. This review summarizes the influence of incorporating such less-common elements in BGs with focus on tissue engineering applications, usually exploiting the bioactivity of the BG in combination with other functional properties imparted by the presence of the added elements.

Synthesis of silver nanoparticle-decorated hydroxyapatite nanocomposite with combined bioactivity and antibacterial properties.

Combination of bioactive material such as hydroxyapatite (HAp) with antibacterial agents would have great potential to be used as bone implant materials to avert possible bacterial infection that can lead to implant-associated diseases. The present study aimed to develop an antibacterial silver nanoparticle-decorated hydroxyapatite (HAp/AgNPs) nanocomposite using chemical reduction and thermal calcination approaches. In this work, natural HAp that was extracted from chicken bone wastes is used as support matrix for the deposition of silver nanoparticles (AgNPs) to produce HAp/AgNPs nanocomposite. XRD, FESEM-EDX, HRTEM, and XPS analyses confirmed that spherical AgNPs were successfully synthesized and deposited on the surface of HAp particles, and the amount of AgNPs adhered on the HAp surface increased with increasing AgNO3 concentration used. The synthesized HAp/AgNPs nanocomposites demonstrated strong antibacterial activity against Staphylococcus aureus bacteria, where the antibacterial efficiency is relied on the amount and size of deposited AgNPs. In addition, the in vitro bioactivity examination in Hank's balanced salt solution showed that more apatite were grown on the surface of HAp/AgNPs nanocomposite when AgNO3 concentration used >1 wt.%. Such nanocomposite with enhanced bioactivity and antibacterial properties emerged as a promising biomaterial to be applied for dentistry and orthopedic implantology.

Evaluation of Ti/Al alloy coated with biogenic hydroxyapatite as an implant device in dogs' femur bones.

The main target of the present research was a full assessment of the toxicity effects and biocompatibility of a Ti/Al-alloy device coated with biogenic hydroxyapatite (bHA) when implanted in dogs in comparison with those of an uncoated Ti/Al-alloy device. The coating of the alloy was carried out using controlled high-velocity suspension flame spray (HVSFS) technique. Both coated and uncoated devices were implanted in dogs' femur bones for different time periods (45 days and 90 days). Bone-formation ability and healing were followed up, and blood analysis was performed, at Time zero (immediately post surgery), and then at 3 days, 45 days, and 90 days post surgery. Bone mineral density checks, radiological scans of the femur bone, and histological analysis were also conducted. The in-vivo study results proved that implantation of a device made from bHA-coated Ti/Al alloy in dogs' femur bones is completely safe. This is due to the high osteoconductivity of the coated alloy, which enables the formation of new bone and a full connection between new and original bone material. At 90 days post surgery, the coated alloy had been completely digested within the original bone; thus, it appeared as a part of the femur bone and not as a foreign body. Both the scanning electron microscopy with energy-dispersive X-ray and histology analysis findings affirmed the results. Furthermore, the blood tests indicated no toxicity effects during the 90 days of implantation.

Nanocomposite coating of albumin/Li-containing bioactive glass nanospheres promotes osteogenic activity of PEEK.

Polyetheretherketone (PEEK) is an important material applied in orthopedic applications, as it posses favorable properties for orthopedic implants, e.g., radiolucency and suitable elastic modulus. However, PEEK exhibits insufficient osteogenesis and osteointegration that limits its clinical applications. In this study, we aimed to enhance the osteogenisis of PEEK by using a surface coating approach. Nanocomposite coating composed of albumin/lithium containing bioactive glass nanospheres was fabricated on PEEK through dip-coating method. The presence of nanocomposite coating on PEEK was confirmed by SEM, FTIR, and XRD techniques. Nanocomposite coatings significantly enhanced hydrophilicity and roughness of PEEK. The nanocomposite coatings also enhanced adhesion, proliferation, and osteogenic differentiation of bone mesenchymal stem cells due to the presence of bioactive glass nanospheres and the BSA substrate film. The results indicate the great potential of the nanocomposite coating in enhancing osteogenesis and osteointegration of PEEK implants.

Biological evaluation of the modified nano-amorphous phosphate calcium doped with citrate/poly-amino acid composite as a potential candidate for bone repair and reconstruction.

Large numbers of research works related to fabricating organic-inorganic composite materials have been carried out to mimic the natural structure of bone. In this study, a new modified n-ACP doped with citrate (n-ACP-cit)/poly (amino acids) (PAA) composite (n-ACP-cit/PAA) was synthesized by employing high bioactive n-ACP-cit and the biodegradable and biocompatible PAA copolymer. Its basic structure was characterized by X-ray diffraction spectroscopy, Fourier transformed infrared spectroscopy, and X-ray photoelectron spectroscopy. Moreover, the degradability, bioactivity, biocompatibility, and osteoconductivity of n-ACP-cit/PAA composite were evaluated in vitro and in vivo, using simulated body fluid (SBF) solution soaking test, mouse bone marrow mesenchymal stem cells proliferation and differentiation, morphological observation test, expression of genes associated with osteogenesis, and bone defect model repair test, respectively. The modified n-ACP-cit/PAA composite exhibited a much higher weight loss rate (36.01 wt.%) than that of PAA (23.99 wt.%) after immersing in SBF solution for 16 weeks and the pH values of local environment restored to neutral condition. Moreover, cells co-culturing with composites exhibited higher alkaline phosphatase activity, more calcium nodule-formation, and higher expression levels of osteogenic differentiation-related genes (Bmp-2, Colla I, OCN, OPN, and Runx-2) than that of PAA. Furthermore, the bone defect model repair test revealed that the composite could be intimately incorporated with the surrounding bone without causing any deleterious reaction and capable of guiding new bone formation. Together, these results indicated that the new modified bone repair n-ACP-cit/PAA composite material with specific characteristics may be designed for meeting diverse requirements from biomedical applications.

The Synthesis Methodology of PEGylated Fe3O4@Ag Nanoparticles Supported by Their Physicochemical Evaluation.

Many investigations are currently being performed to develop the effective synthesis methodology of magnetic nanoparticles with appropriately functionalized surfaces. Here, the novelty of the presented work involves the preparation of nano-sized PEGylated Fe3O4@Ag particles, i.e., the main purpose was the synthesis of magnetic nanoparticles with a functionalized surface. Firstly, Fe3O4 particles were prepared via the Massart process. Next, Ag+ reduction was conducted in the presence of Fe3O4 particles to form a nanosilver coating. The reaction was performed with arabic gum as a stabilizing agent. Sound energy-using sonication was applied to disintegrate the particles' agglomerates. Next, the PEGylation process aimed at the formation of a coating on the particles' surface using PEG (poly(ethylene glycol)) has been performed. It was proved that the arabic gum limited the agglomeration of nanoparticles, which was probably caused by the steric effect caused by the branched compounds from the stabilizer that adsorbed on the surface of nanoparticles. This effect was also enhanced by the electrostatic repulsions. The process of sonication caused the disintegration of aggregates. Formation of iron (II, III) oxide with a cubic structure was proved by diffraction peaks. Formation of a nanosilver coating on the Fe3O4 nanoparticles was confirmed by diffraction peaks with 2θ values 38.15° and 44.35°. PEG coating on the particles' surface was proven via FT-IR (Fourier Transform Infrared Spectroscopy) analysis. Obtained PEG-nanosilver-coated Fe3O4 nanoparticles may find applications as carriers for targeted drug delivery using an external magnetic field.

Hydrothermal synthesis and characterization of magnetic Fe3O4 and APTS coated Fe3O4 nanoparticles: physicochemical investigations of interaction with DNA.

Magnetic nanoparticles (MNPs) especially iron oxide (Fe3O4) NPs have quite extensively been used for in vivo delivery of biomolecules and drugs because of their high bioconjugation efficiency. In this study, Fe3O4 NPs and (3-Aminopropyl) triethoxysilane (APTS) coated Fe3O4 NPs were synthesized and their interaction with Calf thymus (Ct) DNA has been studied in order to understand their usage in biomedical applications. Hydrothermal method was used for the NPs synthesis. Characterization of NPs was done using techniques like UV-Visible spectroscopy, FTIR spectroscopy, FE-SEM, EDAX, Zeta Sizer and powder XRD. Further, interaction studies of NPs with Ct-DNA were investigated using various physicochemical techniques. In UV-Visible studies, hypochromicity with binding constant 3.2 × 105 M-1 was observed. Binding constants calculated using fluorescence studies were found to be k = 3.2 × 104 M-1, 2.9 × 104 M-1 at 293 and 323 K respectively. Results of UV-Visible and fluorescence studies were in correlation with other techniques like UV-TM and CD. All studies suggested alteration in DNA conformation on interaction with surface engineered Fe3O4 NPs, stabilizing DNA-NPs conjugate via partial intercalation and electrostatic interactions. This study may facilitate our understanding regarding the physicochemical properties and DNA-binding ability of APTS-Fe3O4 NPs for their further application in magnetosensitive biosensing and drug delivery. Iron oxide based magnetic nanoparticles are well known for their excellent bio-conjugation efficiency and therefore APTS-Fe3O4 NPs were synthesized via very simple and benign hydrothermal method. Further, the interaction of APTS-Fe3O4 NPs with calf thymus DNA was studied using various physicochemical techniques to explore their potential in biomedical applications.

Preparation and characterization of human keratinocyte-fibroblast cell sheets constructed using PNIAM-co-AM grafted surfaces for burn wound healing.

Autologous skin grafting, the standard treatment for severe burns, is sometimes not possible due to the limited available skin surfaces for the procedure. With advances in tissue engineering, various cell-based skin substitutes have been developed to serve as skin replacements and to promote tissue regeneration and healing. In this work, we propose the use of cell sheet technology to fabricate keratinocyte-fibroblast tissue constructs from the temperature-responsive poly(N-isoproprylacrylamide-co-acrylamide) (PNIAM-co-AM) grafted surfaces for the treatment of burn wounds. The characteristics of the human keratinocyte and fibroblast cell sheets harvested using PNIAM-co-AM grafted surfaces were similar to those cell sheets detached from the commercially-available UpCellTM plates. Upon lowering the incubation temperature, confluent keratinocytes and fibroblasts could be detached as intact sheets, consisting of biologically active cells, as indicated by their high cell viability and their reattachment, migratory, and proliferative activities. A histological analysis of the stratified keratinocyte-fibroblast cell sheets revealed the evidence of cell migration and tissue reorganization to form two distinct epidermal and dermal layers, quite similar to the skin tissue's structure. In addition, the keratinocyte-fibroblast sheets could synthesize and release significant amounts of essential cytokines and growth factors involved in regulating the wound healing process, including IL-1α, IL-6, TNF-α, VEGF, and bFGF, implying the therapeutic effect of these cell sheets, which could be beneficial to accelerate tissue repair and regeneration, leading to faster wound healing.

The effect of macrophages on an atmospheric pressure plasma-treated titanium membrane with bone marrow stem cells in a model of guided bone regeneration.

Guided bone regeneration (GBR) is an established treatment. However, the mechanisms of GBR are not fully understood. Recently, a GBR membrane was identified that acts as a passive barrier to regenerate bone via activation and migration of macrophages (Mps) and bone marrow stem cells (BMSCs). Atmospheric pressure plasma treatment of the titanium membrane (APP-Ti) activated macrophages. The purpose of this study was to analyze whether macrophages attached to an APP-Ti membrane affected differentiation of BMSCs in a GBR model. Human THP-1 macrophages (hMps) were cultured on non-treated Ti (N-Ti) and APP-Ti membrane. Macrophage polarization was analyzed by RT-PCR and immunocytochemistry. Secreted proteins from hMps on N-Ti and APP-Ti were detected by LC/MS/MS. hBMSCs were co-cultured with hMps on N-Ti or APP-Ti and analyzed by osteogenic differentiation, Alizarin red S staining, and alkaline phosphatase (ALP) activity. N-Ti and APP-Ti membrane were also implanted into bone defects of rat calvaria. hMps on APP-Ti were polarized M2-like macrophages. hMps on N-Ti secreted plasminogen activator inhibitor-1 and syndecan-2, but hMps on APP-Ti did not. hBMSCs co-cultured with hMps on APP-Ti increased cell migration and gene expression of osteogenic markers, but suppressed mineralization, while ALP activity was similar to that of hMps on N-Ti in vitro. The volume of newly formed bone was not significantly different between N-Ti and APP-Ti membrane in vivo. M2 polarized hMps on APP-Ti suppressed osteogenic induction of hBMSCs in vitro. The indirect role of hMps on APP-Ti in newly formed bone was limited.

3D printing of an integrated triphasic MBG-alginate scaffold with enhanced interface bonding for hard tissue applications.

Osteochondral defects affect both of cartilage and subchondral areas, thus it poses a significant challenge to simultaneously regenerate two parts in orthopedics. Tissue engineering strategy is currently regarded as the most promising way to repair osteochondral defects. This study focuses on developing a multilayered scaffold with enhanced interface bonding through 3D printing. One-shot printing process enables control over material composition, pore structure, and size in each region of the scaffold, while realizes seamlessly integrated construct as well. The scaffold was designed to be triphasic: a porous bone layer composed of alginate sodium (SA) and mesoporous bioactive glasses (MBG), an intermediate dense layer also composed of SA and MBG and a cartilaginous layer composed of SA. The mechanical strength including the interface adhesion strength between layers were characterized. The results indicated that SA crosslinking after 3D printing anchored different materials together and integrated all regions. Additional scaffold soaking in simulated body fluid (SBF) and cell culture medium induced apatite deposition and had weakened the compressive and tensile strengths, while no layer dislocation or delamination occurred.

Rotary-jet spun polycaprolactone/nano-hydroxyapatite scaffolds modified by simulated body fluid influenced the flexural mode of the neoformed bone.

Polycaprolactone (PCL) is a biocompatible, biodegradable synthetic polymer which in combination with nanohydroxyapatite (nHAp) can give rise to a low cost, nontoxic bioactive product with excellent mechanical properties and slow degradation. Here we produced, characterized and evaluated in vivo the bone formation of PCL/nHAp scaffolds produced by the rotary jet spinning technique. The scaffolds produced were firstly soaked into simulated body fluid for 21 days to also obtain nHAp onto PCL/nHAp scaffolds. Afterwards, the scaffolds were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy and Raman spectroscopy. For in vivo experiments, 20 male Wistar rats were used and randomly divided in 4 experimental groups (n = 5). A critical defect of 3 mm in diameter was made in the tibia of the animals, which were filled with G1 control (clot); G2-PCL scaffold; G3-PCL/nHAp (5%) scaffold; G4-PCL/nHAp (20%) scaffold. All animals were euthanized 60 days after surgery, and the bone repair in the right tibiae were evaluated by radiographic analysis, histological analysis and histomorphometric analysis. While in the left tibias, the areas of bone repair were submitted to the flexural strength test. Radiographic and histomorphometric analyses no showed statistical difference in new bone formation between the groups, but in the three-point flexural tests, the PCL/nHAp (20%) scaffold positively influenced the flexural mode of the neoformed bone. These findings indicate that PCL/nHAp (20%) scaffold improve biomechanical properties of neoformed bone and could be used for bone medicine regenerative.

Microfabrication of a biomimetic arcade-like electrospun scaffold for cartilage tissue engineering applications.

In recent years, the engineering of biomimetic cellular microenvironments has emerged as a top priority for regenerative medicine, being the in vitro recreation of the arcade-like cartilaginous tissue one of the most critical challenges due to the notorious absence of cost- and time-efficient microfabrication techniques capable of building 3D fibrous scaffolds with precise anisotropic properties. Taking this into account, we suggest a feasible and accurate methodology that uses a sequential adaptation of an electrospinning-electrospraying set up to construct a hierarchical system comprising both polycaprolactone (PCL) fibres and polyethylene glycol sacrificial microparticles. After porogen leaching, the bi-layered PCL scaffold was capable of presenting not only a depth-dependent fibre orientation similar to natural cartilage, but also mechanical features and porosity proficient to encourage an enhanced cell response. In fact, cell viability studies confirmed the biocompatibility of the scaffold and its ability to guarantee suitable cell adhesion, proliferation and migration throughout the 3D anisotropic fibrous network during 21 days of culture. Additionally, likewise the hierarchical relationship between chondrocytes and their extracellular matrix, the reported PCL scaffold was able to induce depth-dependent cell-material interactions responsible for promoting a spatial modulation of the morphology, alignment and density of the cells in vitro.

Light-Addressable Electrodes for Dynamic and Flexible Addressing of Biological Systems and Electrochemical Reactions.

In this review article, we are going to present an overview on possible applications of light-addressable electrodes (LAE) as actuator/manipulation devices besides classical electrode structures. For LAEs, the electrode material consists of a semiconductor. Illumination with a light source with the appropiate wavelength leads to the generation of electron-hole pairs which can be utilized for further photoelectrochemical reaction. Due to recent progress in light-projection technologies, highly dynamic and flexible illumination patterns can be generated, opening new possibilities for light-addressable electrodes. A short introduction on semiconductor-electrolyte interfaces with light stimulation is given together with electrode-design approaches. Towards applications, the stimulation of cells with different electrode materials and fabrication designs is explained, followed by analyte-manipulation strategies and spatially resolved photoelectrochemical deposition of different material types.

Synthesis and Characterization of Citrate-Stabilized Gold-Coated Superparamagnetic Iron Oxide Nanoparticles for Biomedical Applications.

Surface-functionalized gold-coated superparamagnetic iron oxide nanoparticles (Au-SPIONs) may be a useful tool in various biomedical applications. To obtain Au-SPIONs, gold salt was precipitated onto citrate-stabilized SPIONs (Cit-SPIONs) using a simple, aqueous one-pot technique inspired by the Turkevich method of gold nanoparticle synthesis. By the further stabilization of the Au-SPION surface with additional citrate (Cit-Au-SPIONs), controllable and reproducible Z-averages enhanced long-term dispersion stability and moderate dispersion pH values were achieved. The citrate concentration of the reaction solution and the gold/iron ratio was found to have a major influence on the particle characteristics. While the gold-coating reduced the saturation magnetization to 40.7% in comparison to pure Cit-SPIONs, the superparamagnetic behavior of Cit-Au-SPIONs was maintained. The formation of nanosized gold on the SPION surface was confirmed by X-ray diffraction measurements. Cit-Au-SPION concentrations of up to 100 µg Fe/mL for 48 h had no cytotoxic effect on Jurkat cells. At a particle concentration of 100 µg Fe/mL, Jurkat cells were found to take up Cit-Au-SPIONs after 24 h of incubation. A significantly higher attachment of thiol-containing L-cysteine to the particle surface was observed for Cit-Au-SPIONs (53%) in comparison to pure Cit-SPIONs (7%).