Photo-crosslinked chitosan-gelatin xerogel-like coating onto "cold" plasma functionalized poly(lactic acid) film as cell culture support

This paper reports on biofunctionalisation of a poly(lactic acid) (PLA) film by surface activation through cold plasma treatment followed by coating with a chitosan-gelatin xerogel. The UV cross-linking of the xerogel precursor was simultaneously performed with the fixation onto the PLA support. This has a strong effect on surface properties, in terms of wettability, surface free energy, morphology and micromechanical features. The hydrophilic - hydrophobic character of the surface, determined by contact angle measurements, was tuned along the process, passing from moderate hydrophobic PLA to enhanced hydrophilic plasma activated surface, which favors coating adhesion, then to moderate hydrophobic chitosan-gelatin coating. The coating has a Lewis amphoteric surface, with a porous xerogel-like morphology, as revealed by scanning electron microscopy images. By riboflavin mediated UV cross-linking the chitosan-gelatin coating becomes high adhesive and with a more pronounced plasticity, as shown by AFM force-distance spectroscopy. Thus prepared surface-coated PLA supports were successfully tested for growth of dermal fibroblasts, which are known for their induction potential of chondrogenic cells, which is very important in cartilage tissue engineering.

Covalent Conjugation of Small Molecule Inhibitors and Growth Factors to a Silk Fibroin-Derived Bioink to Develop Phenotypically Stable 3D Bioprinted Cartilage

Implantation of a phenotypically stable cartilage graft could represent a viable approach for repairing osteoarthritic (OA) cartilage lesions. In the present study, we investigated the effects of modulating the bone morphogenetic protein (BMP), transforming growth factor beta (TGFβ), and interleukin-1 (IL-1) signaling cascades in human bone marrow stromal cell (hBMSC)-encapsulated silk fibroin gelatin (SF-G) bioink. The selected small molecules LDN193189, TGFβ3, and IL1 receptor antagonist (IL1Ra) are covalently conjugated to SF-G biomaterial to ensure sustained release, increased bioavailability, and printability, confirmed by ATR-FTIR, release kinetics, and rheological analyses. The 3D bioprinted constructs with chondrogenically differentiated hBMSCs were incubated in an OA-inducing medium for 14 days and assessed through a detailed qPCR, immunofluorescence, and biochemical analyses. Despite substantial heterogeneity in the observations among the donors, the IL1Ra molecule illustrated the maximum efficiency in enhancing the expression of articular cartilage components, reducing the expression of hypertrophic markers (re-validated by the GeneMANIA tool), as well as reducing the production of inflammatory molecules by the hBMSCs. Therefore, this study demonstrated a novel strategy to develop a chemically decorated, printable and biomimetic SF-G bioink to produce hyaline cartilage grafts resistant to acquiring OA traits that can be used for the treatment of degenerated cartilage lesions.

Significance of Zn Complex Concentration on Microstructure Evolution and Corrosion Behavior of Al/WS2

Corrosion is a harmful processes which by definition is a chemical or electrochemical reaction between a substance (usually a metal) and the environment which leads to a change in the properties of the substance and has destructive effects. In this study, new composites consisting of Al/WS2/ZnTerp-2TH with 5 and 10 wt.% ZnTerp-2TH were prepared and the results were fully compared. Al/WS2 played the role of matrix and ZnTerp-2TH played the role of reinforcement. In other words, as a novelty to prevent the corrosion of Al/WS2, ZnTerp-2TH is designed and synthesized and showed good results when the corrosion ratio was reduced by the existence of ZnTerp-2TH. Furthermore, the NMR and mass analysis of ZnTerp-2TH were carried out, and the thermal properties, X-ray diffraction, Fourier-transform infrared (FTIR) spectroscopy, morphology, energy-dispersive X-ray spectroscopy (EDX) analysis and corrosion behavior of the composites were also discussed in detail. The crystal size values of composites were calculated by the modified Scherrer method 34, 26 and 27 nm for Al/WS2, Al/WS2/5 wt.% ZnTerp-2TH and Al/WS2/10 wt.% ZnTerp-2TH, respectively. The microstructural examination of the specimens showed that the reinforcing phase (ZnTerp-2TH) has a favorable distribution on the surface of Al/WS2 when it covers the cracks and holes. In addition, the corrosion investigation results showed that the addition of ZnTerp-2TH to Al/WS2 can improve the corrosion resistance when the Ecorr and Icorr values of Al/WS2/10 wt.% ZnTerp-2TH were recorded in tandem -724 mV/decade and 5 uA cm-2.

Physiomimetic biocompatibility evaluation of directly printed degradable porous iron implants using various cell types

Additively manufactured (AM) degradable porous metallic biomaterials offer unique opportunities for satisfying the design requirements of an ideal bone substitute. Among the currently available biodegradable metals, iron has the highest elastic modulus, meaning that it would benefit the most from porous design. Given the successful preclinical applications of such biomaterials for the treatment of cardiovascular diseases, the moderate compatibility of AM porous iron with osteoblast-like cells, reported in earlier studies, has been surprising. This may be because, as opposed to static in vitro conditions, the biodegradation products of iron in vivo are transported away and excreted. To better mimic the in situ situations of biodegradable biomaterials after implantation, we compared the biodegradation behavior and cytocompatibility of AM porous iron under static conditions to the conditions with dynamic in situ-like fluid flow perfusion in a bioreactor. Furthermore, the compatibility of these scaffolds with four different cell types was evaluated to better understand the implications of these implants for the complex process of natural wound healing. These included endothelial cells, L929 fibroblasts, RAW264.7 macrophage-like cells, and osteoblastic MG-63 cells. The biodegradation rate of the scaffolds was significantly increased in the perfusion bioreactor as compared to static immersion. Under either condition, the compatibility with L929 cells was the best. Moreover, the compatibility with all the cell types was much enhanced under physiomimetic dynamic flow conditions as compared to static biodegradation. Our study highlights the importance of physiomimetic culture conditions and cell type selection when evaluating the cytocompatibility of degradable biomaterials in vitro. STATEMENT OF SIGNIFICANCE: Additively manufactured (AM) degradable porous metals offer unique opportunities for the treatment of large bony defects. Despite the successful preclinical applications of biodegradable iron in the cardiovascular field, the moderate compatibility of AM porous iron with osteoblast-like cells was reported. To better mimic the in vivo condition, we compared the biodegradation behavior and cytocompatibility of AM porous iron under static condition to dynamic perfusion. Furthermore, the compatibility of these scaffolds with various cell types was evaluated to better simulate the process of natural wound healing. Our study suggests that AM porous iron holds great promise for orthopedic applications, while also highlighting the importance of physio-mimetic culture conditions and cell type selection when evaluating the cytocompatibility of degradable biomaterials in vitro.

Synthesis and Characterization of a Titanium-Based Functionally Graded Material-Structured Biocomposite using Powder Metallurgy

This investigation aims at synthesizing and characterizing a biocomposite of hydroxyapatite (HA) and titanium (Ti) as a functionally graded material (FGM) via an economical powder metallurgy route. Ti particles were produced through drilling and chipping, followed by compaction and sintering. Ti foams, so obtained, were then infused with varying volume fractions of HA. The pure Ti foam control sample and the FGM composite samples were then subjected to various characterizations to validate their biocompatibility, structural strength, and integrity. The interface development between the load-bearing Ti implant and living tissue was resolved through an FGM structure, where the base of the implant consisted of load-bearing Ti and the outer periphery changed to HA gradually. HA/Ti specimens of different volume fractions were tested for density measurements, microstructure, hardness, and bioactivity. The bioactive behavior was investigated using the potentiodynamic polarization technique to measure the corrosion rate of the pure Ti foam (0/100 HA/Ti) and the FGM composite (10/90 HA/Ti) samples in a simulated body fluid (SBF). The results showed that the hardness of FGM composites, despite being less than that of 0/100 HA/Ti, was still within safe limits. The corrosion rate, however, was found to be decreased by a significant value of almost 40% for the 10/90 HA/Ti FGM composite sample compared to the pure Ti foam control sample. It was concluded that the optimum composition 10/90 HA/Ti sample offers improved corrosion resistance while maintaining a sufficient allowable hardness level.

The synthesis of Tween80/calcium phosphate nanocomposite bioactive gelatine-based gels as a proof of concept for tooth sensitivity home-treatment

Dentine hypersensitivity interferes with the lifestyle owing to pain arising from exposed dentine surfaces in response to stimuli. One common way to treat this problem is to occlude the exposed tubules. In this work, we have proposed a home-based treatment gel for tooth sensitivity. The gel was prepared using the emulsion method and contained Tween80/calcium phosphate nanocomposite that could occlude the tubules after 10 h of application. In preparation, Tween80 was used as a surfactant, and oleic acid was used as an oil phase to form a water-in-oil nanoreactor for calcium phosphate synthesis. Finally, different concentrations of gelatine were used to transform the emulsion into a stable gel. The nanoparticles had a uniform spherical shape and a diameter of approximately 300 nm. The nanocomposite gel containing the lowest amount of gelatine (Gel-T80-5%GE) exhibited the best liquid-like property and the highest occlusion rate of 95%.

Dopamine-Assisted Modification of Polypropylene Film to Attain Hydrophilic Mineral-Rich Surfaces

The presented study focuses on the modification of polypropylene (PP) film with tetraethyl orthosilicate (TEOS) under heterogeneous conditions via polydopamine/polyethylene imine (PDA/PEI) chemistry using a facile dip-coating procedure to attain hydrophilic mineral-rich surfaces. Thus, the resulting PP-based films were further immersed in ion-rich simulated body fluid (SBF) to deposit Ca-based minerals onto the film's surfaces efficiently. In addition, the chemical reaction mechanism on PP film was proposed, and mineralisation potential inspected by determination of functional groups of deposits, zeta potential, hydrophilicity and surface morphology/topography using Fourier transform infrared (FTIR) spectroscopy, streaming potential, water contact angle (WCA), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The obtained results show the improved wettability of samples on account of PDA inclusion (WCA was reduced from 103° for pure PP film to 28° for PDA-modified film), as well as the presence of functional groups, due to the PDA/PEI/TEOS surface functionalisation, increased the ability of minerals to nucleate on the PP film's surface when it was exposed to an SBF medium. Moreover, the higher surface roughness due to the silica coatings influenced the enhanced anchoring and attachment of calcium phosphate (CaP), revealing the potential of such a facile approach to modify the chemically inert PP films, being of particular interest in different fields, including regenerative medicine.

The Effect of the Corrosion Medium on Silane Coatings Deposited on Titanium Grade 2 and Titanium Alloy Ti13Nb13Zr

The present paper focuses on the fabrication of coatings based on vinyltrimethoxysilane and the influence of various corrosion media on the coatings produced. Coatings were deposited on two substrate materials, namely, titanium Grade 2 and titanium alloy Ti13Nb13Zr, by immersion in a solution containing vinyltrimethoxysilane, anhydrous ethyl alcohol, acetic acid and distilled water. The obtained coatings were characterized in terms of surface morphology, adhesion to the substrate and corrosion resistance. As corrosion solutions, four different simulated physiological fluids, which differed in the contents of individual ions, and a 1 mol dm⁻³ NaBr solution were used. The chloride ions contained in the simulated physiological fluids did not lead to pitting corrosion of titanium Grade 2 and titanium alloy Ti13Nb13Zr. This investigation shows that titanium undergoes pitting corrosion in a bromide ion medium. It is demonstrated that the investigated coatings slow down corrosion processes in all corrosion media examined.

Functionalization of Crosslinked Sodium Alginate/Gelatin Wet-Spun Porous Fibers with Nisin Z for the Inhibition of Staphylococcus aureus-Induced Infections

Nisin Z, an amphipathic peptide, with a significant antibacterial activity against Gram-positive bacteria and low toxicity in humans, has been studied for food preservation applications. Thus far, very little research has been done to explore its potential in biomedicine. Here, we report the modification of sodium alginate (SA) and gelatin (GN) blended microfibers, produced via the wet-spinning technique, with Nisin Z, with the purpose of eradicating Staphylococcus aureus-induced infections. Wet-spun SAGN microfibers were successfully produced at a 70/30% v/v of SA (2 wt%)/GN (1 wt%) polymer ratio by extrusion within a calcium chloride (CaCl₂) coagulation bath. Modifications to the biodegradable fibers' chemical stability and structure were then introduced via crosslinking with CaCl₂ and glutaraldehyde (SAGNCL). Regardless of the chemical modification employed, all microfibers were labelled as homogeneous both in size (≈246.79 µm) and shape (cylindrical and defect-free). SA-free microfibers, with an increased surface area for peptide immobilization, originated from the action of phosphate buffer saline solution on SAGN fibers, were also produced (GNCL). Their durability in physiological conditions (simulated body fluid) was, however, compromised very early in the experiment (day 1 and 3, with and without Nisin Z, respectively). Only the crosslinked SAGNCL fibers remained intact for the 28 day-testing period. Their thermal resilience in comparison with the unmodified and SA-free fibers was also demonstrated. Nisin Z was functionalized onto the unmodified and chemically altered fibers at an average concentration of 178 µg/mL. Nisin Z did not impact on the fiber's morphology nor on their chemical/thermal stability. However, the peptide improved the SA fibers (control) structural integrity, guaranteeing its stability for longer, in physiological conditions. Its main effect was detected on the time-kill kinetics of the bacteria S. aureus. SAGNCL and GNCL loaded with Nisin Z were capable of progressively eliminating the bacteria, reaching an inhibition superior to 99% after 24 h of culture. The peptide-modified SA and SAGN were not as effective, losing their antimicrobial action after 6 h of incubation. Bacteria elimination was consistent with the release kinetics of Nisin Z from the fibers. In general, data revealed the increased potential and durable effect of Nisin Z (significantly superior to its free, unloaded form) against S. aureus-induced infections, while loaded onto prospective biomedical wet-spun scaffolds.

Oxide thin films as bioactive coatings

Growth and survival of biological cells (eukaryotes and prokaryotes) on artificial environments often depend on their interactions with the specific surface. Various organic materials can be coated on substrates to assist cells' adhesion and other subsequent cellular processes. However, these coatings are expensive, degrade over short time period, and may even interfere with the cells' signaling processes. Therefore, the use of inorganic surfaces in order to control cellular interactions is of scientific importance from fundamental and application perspectives. Among inorganic materials, oxide thin films have received considerable attention. Thin films of oxides have the advantage of tailoring the surfaces for cellular interactions while using a negligible amount of the oxide material. Here, we review the lesser known application of inorganic oxide coatings as biocompatible and implantable platforms for different purposes, such as biofilm inhibition, cell culture and implant enhancements.