Fabrication and characterization of polyvinyl alcohol/metal (Ca, Mg, Ti) doped zirconium phosphate nanocomposite films for scaffold-guided tissue engineering application

A bioactive and anti-bacterial nano-sized zirconium phosphate/GO (nZrP/GO) composite: Potential use as a coating for dental implants?

OBJECTIVE

Dental implants fabricated from titanium have several limitations and therefore, alternative materials that fulfil the criteria of successful dental implant (bioactivity and anti-bacterial activity) need to be considered. Polyether ether ketone (PEEK) has been suggested to replace titanium implants. However, this material needs surface modification to meet the appropriate criteria. A nano-sized zirconium phosphate/GO (nZrP/GO) composite coating was prepared to improve PEEK's biological qualities.

METHODS

Polished and cleaned PEEK discs were coated with the composite of nZrP doped with 1.25 wt% GO by the soft-template method. To analyze the composite coating, X-ray, atomic force microscopy, and field emission scanning electron microscopy-energy dispersive spectroscopy were used. The adhesion of the coating to PEEK was measured by adhesive tape test. By measuring the optical contact angle, the coated and non-coated samples' differences in wettability were evaluated. Antimicrobial activity was evaluated against S. aureus and E. coli and cytotoxicity tested employing gingival fibroblasts and osteoblast-like cells.

RESULTS

The nZrP/GO composite coating was 23.45 µm thick, was irregular and attached strongly to the PEEK surface. Following coating, the water contact angle dropped to 34° and surface roughness to 13 nm. The coating reduced the count of bacteria two-fold and was non-cytotoxic to mammalian osteoblast-like cells and fibroblasts. A precipitation of nano-calcium-deficient apatite was observed on the surface of the nZrP/GO coating following a 28-day immersion in SBF.

SIGNIFICANCE

PEEK-coated with nZr/GO coating is a good candidate as dental implant.

Injectable extracellular matrix-mimetic hydrogel based on electrospun Janus fibers

To date, the reported injectable hydrogels have failed to mimic the fibrous architecture of the extracellular matrix (ECM), limiting their biological effects on cell growth and phenotype. Additionally, they lack the micro-sized pores present within the ECM, which is unfavorable for the facile transport of nutrients and waste. Herein, an injectable ECM-mimetic hydrogel (IEMH) was fabricated by shortening and dispersing Janus fibers capable of self-curling at body temperature into pH 7.4 phosphate buffer solution. The IEMH could be massively prepared through a side-by-side electrospinning process combined with ultraviolet irradiation. The IEMHs with only 5 wt% fibers could undergo sol-gel transition at body temperature to become solid gels with desirable stability, sturdiness, and elasticity and self-healing ability. In addition, they possessed notable pseudoplasticity, which is beneficial to injection at room temperature. The results obtained from characterization analysis via scanning electron microscopy, total internal reflection fluorescence microscopy, nuclear magnetic resonance spectroscopy, and Fourier-transform infrared spectroscopy indicate that their sol-gel transition under physiological conditions stems from the synergistic action of the tight entanglements between thermally-induced self-curling fibers and the hydrophobic interaction between the fibers. An MTT assay using C2C12 myoblast cells was performed to examine the in vitro cytotoxicity of IEMHs for biomedical applications, and the cell viability was found to be more than 95%.

Pioneering a paradigm shift in tissue engineering and regeneration with polysaccharides and proteins-based scaffolds: A comprehensive review

In the realm of modern medicine, tissue engineering and regeneration stands as a beacon of hope, offering the promise of restoring form and function to damaged or diseased organs and tissues. Central to this revolutionary field are biological macromolecules-nature's own blueprints for regeneration. The growing interest in bio-derived macromolecules and their composites is driven by their environmentally friendly qualities, renewable nature, minimal carbon footprint, and widespread availability in our ecosystem. Capitalizing on these unique attributes, specific composites can be tailored and enhanced for potential utilization in the realm of tissue engineering (TE). This review predominantly concentrates on the present research trends involving TE scaffolds constructed from polysaccharides, proteins and glycosaminoglycans. It provides an overview of the prerequisites, production methods, and TE applications associated with a range of biological macromolecules. Furthermore, it tackles the challenges and opportunities arising from the adoption of these biomaterials in the field of TE. This review also presents a novel perspective on the development of functional biomaterials with broad applicability across various biomedical applications.

Polyvinyl Alcohol/Nafion®-Zirconia Phosphate Nanocomposite Membranes for Polymer Electrolyte Membrane Fuel Cell Applications: Synthesis and Characterisation

PVA (polyvinyl alcohol)-ZrP (PVA/ZrP) and Nafion®/PVA-ZrP nanocomposite membranes were synthesised using the recasting method with glutaraldehyde (GA) as a crosslinking agent. The resulting nanocomposite membranes were characterised using a variety of techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). The results of SEM revealed well-distributed zirconia phosphate (ZrP) within the membrane matrix, and the SEM images showed a uniform and dense membrane structure. Because ZrP nanoparticles are hydrophilic, the Nafion®/PVA-ZrP nanocomposite membrane had a higher water uptake of 53% at 80 °C and higher 0.19 S/cm proton conductivity at room temperature than the commercial Nafion® 117 membrane, which had only 34% and 0.113 S/cm, respectively. In comparison to commercial Nafion® 117 membranes, PVA-ZrP and Nafion®/PVA-ZrP nanocomposite membranes had a higher thermal stability and mechanical strength and lower methanol crossover due to the hydrophilic effect of PVA crosslinked with GA, which can make strong hydrogen bonds and cause an intense intramolecular interaction.

Facet-Dependent Bactericidal Activity of Ag3PO4 Nanostructures against Gram-Positive/Negative Bacteria

Ag₃PO₄ nanostructures (APNs) containing silver (Ag metal; of the noble metal families) have the potential to exhibit enzyme-mimetic activity. A nanostructure shape, including its surface facets, can improve the bioactivity of enzyme mimicry, yet the molecular mechanisms remain unclear. Herein, we report facet-dependent peroxidase and oxidase-like activity of APNs with both antibacterial and biofilm degrading properties through the generation of reactive oxygen species. Cubic APNs had superior antibacterial effects than rhombic dodecahedral shapes when inhibiting Gram-positive and Gram-negative bacterial pathogen proliferation and biofilm degradation. A similar performance was observed for rhombic dodecahedral shapes, being greater than tetrahedral-shaped APNs. The extent of enzyme-mimetic activity is attributed to the facets {100} present in cubic APNs that led the peroxide radicals to inhibit the proliferation of bacteria and degrade biofilm. These facets were compared to rhombic dodecahedral APNs {110} and tetrahedral APNs {111}, respectively, to reveal a facet-dependent enhanced antibacterial activity, providing a plausible mechanism for shape-dependent APNs material enzyme-mimetic effects on bacteria. Thus, our research findings can provide a direction to optimize bactericidal materials using APNs in clinically relevant applications.

Microstructure Study and Linear/Nonlinear Optical Performance of Bi-Embedded PVP/PVA Films for Optoelectronic and Optical Cut-Off Applications

Hybrid polymer films of polyvinyl pyrrolidone (PVP)/polyvinyl alcohol (PVA) embedded with gradient levels of Bi-powder were prepared using a conventional solution casting process. XRD, FTIR, and SEM techniques have been used to examine the micro/molecular structure and morphology of the synthesized flexible films. The intensities of the diffraction peaks and transmission spectrum of the PVP/PVA gradually declined with the introduction of Bi-metal. In addition, filler changes the microstructure surface of the pure film. The modification in the microstructure leads to an enhancement in the optical absorption characteristic of the blend films. The indirect allowed transition energy was calculated via Tauc’s and ASF (Absorption Spectra Fitting) models. The decrease in the hybrid film’s bandgap returns to the localized states in the forbidden region, which led the present films to be suitable for photo-electric, solar cell, etc., applications. The relation between the transition energy and the refractive index was studied. The enhancement in the refractive index with Bi-metal concentrations led to use the as-prepared films in optical sensors. The rise of Bi-metal concentrations leads also to the improvement of the nonlinear susceptibility and refractive parameters. The optical limiting characteristics revealed that the higher concentration dopant films reduce the light transmission intensity which is appropriate for laser attenuation and optical limiting in photonic devices. The results suggest that hybrid films are promising materials in a wide range of opto-electronic applications.

Progress of 3D Printing Techniques for Nasal Cartilage Regeneration

Once cartilage is damaged, its self-repair capacity is very limited. The strategy of tissue engineering has brought a new idea for repairing cartilage defect and cartilage regeneration. In particular, nasal cartilage regeneration is a challenge because of the steady increase in nasal reconstruction after oncologic resection, trauma, or rhinoplasty. From this perspective, three-dimensional (3D) printing has emerged as a promising technology to address the complexity of nasal cartilage regeneration, using patient's image data and computer-aided deposition of cells and biomaterials to precisely fabricate complex, personalized tissue-engineered constructs. In this review, we summarized the major progress of three prevalent 3D printing approaches, including inkjet-based printing, extrusion-based printing and laser-assisted printing. Examples are highlighted to illustrate 3D printing for nasal cartilage regeneration, with special focus on the selection of seeded cell, scaffolds and growth factors. The purpose of this paper is to systematically review recent research about the challenges and progress and look forward to the future of 3D printing techniques for nasal cartilage regeneration.Level of Evidence III This journal requires that authors assign a level of evidence to each submission to which Evidence-Based Medicine rankings are applicable. This excludes Review Articles, Book Reviews, and manuscripts that concern Basic Science, Animal Studies, Cadaver Studies, and Experimental Studies. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors https://www.springer.com/00266 .

Multiscale engineered artificial tooth enamel

Tooth enamel, renowned for its high stiffness, hardness, and viscoelasticity, is an ideal model for designing biomimetic materials, but accurate replication of complex hierarchical organization of high-performance biomaterials in scalable abiological composites is challenging. We engineered an enamel analog with the essential hierarchical structure at multiple scales through assembly of amorphous intergranular phase (AIP)-coated hydroxyapatite nanowires intertwined with polyvinyl alcohol. The nanocomposite simultaneously exhibited high stiffness, hardness, strength, viscoelasticity, and toughness, exceeding the properties of enamel and previously manufactured bulk enamel-inspired materials. The presence of AIP, polymer confinement, and strong interfacial adhesion are all needed for high mechanical performance. This multiscale design is suitable for scalable production of high-performance materials.

Preparation of Zirconium Hydrogen Phosphate Coatings on Sandblasted/Acid-Etched Titanium for Enhancing Its Osteoinductivity and Friction/Corrosion Resistance

Background

Sandblasted/acid-etched titanium (SLA-Ti) implants are widely used for dental implant restoration in edentulous patients. However, the poor osteoinductivity and the large amount of Ti particles/ions released due to friction or corrosion will affect its long-term success rate.

Purpose

Various zirconium hydrogen phosphate (ZrP) coatings were prepared on SLA-Ti surface to enhance its friction/corrosion resistance and osteoinduction.

Methods

The mixture of ZrCl₄ and H₃PO₄ was first coated on SLA-Ti and then calcined at 450°C for 5 min to form ZrP coatings. In addition to a series of physiochemical characterization such as morphology, roughness, wettability, and chemical composition, their capability of anti-friction and anti-corrosion were further evaluated by friction-wear test and by potential scanning. The viability and osteogenic differentiation of MC3T3-E1 cells on different substrates were investigated via MTT, mineralization and PCR assays.

Results

The characterization results showed that there were no significant changes in the morphology, roughness and wettability of ZrP-modified samples (SLA-ZrP0.5 and SLA-ZrP0.7) compared with SLA group. The results of electrochemical corrosion displayed that both SLA-ZrP0.5 and SLA-ZrP0.7 (especially the latter) had better corrosion resistance than SLA in normal saline and serum-containing medium. SLA-ZrP0.7 also exhibited the best friction resistance and great potential to enhance the spreading, proliferation and osteogenic differentiation of MC3T3-E1 cells.

Conclusion

We determined that SLA-ZrP0.7 had excellent comprehensive properties including anti-corrosion, anti-friction and osteoinduction, which made it have a promising clinical application in dental implant restoration.

Water-stable zirconium-based metal-organic frameworks armed polyvinyl alcohol nanofibrous membrane with enhanced antibacterial therapy for wound healing

Inadequate water-stability and antibacterial activity limit the biomedical application of polyvinyl alcohol (PVA)-based membranes in moist environments. In this work, we propose a strategy to improve the water-stability of PVA membranes via metal complexation and heat treatment. We report a simple routine where the zirconium-based UiO-66-NH₂ metal-organic frameworks (MOFs) are nucleated as a layer on the surface of PVA nanofibrous membranes (UiO-66-NH₂@PVA NFMs). We find that the chemical modification of membranes increases their hydrophilicity and adds on mechanical support for the brittle UiO-66-NH₂ MOFs. Additionally, we demonstrate the application of UiO-66-NH₂ MOFs as drug carriers for antibacterial drug, levofloxacin (LV). The active drug component is preloaded during the one-step nucleation process. The obtained LV loaded UiO-66-NH₂@PVA NFMs (LV@UiO-66-NH₂@PVA) are shown to be bactericidal with the efficiency > 99.9% at 100 μg/mL against two bacterial species, Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Compared with the commercially available gauzes, the UiO-66-NH₂@PVA and LV@UiO-66-NH₂@PVA treatments will significantly improve the wound healing process. Animal studies show that the LV@UiO-66-NH₂@PVA will effectively offer a safe alternative solution for the patients to protect against bacterial infections, demonstrating the potential application of MOF-based NFMs as wound dressing agents.

Innovative Human Three-Dimensional Tissue-Engineered Models as an Alternative to Animal Testing

Animal testing has long been used in science to study complex biological phenomena that cannot be investigated using two-dimensional cell cultures in plastic dishes. With time, it appeared that more differences could exist between animal models and even more when translated to human patients. Innovative models became essential to develop more accurate knowledge. Tissue engineering provides some of those models, but it mostly relies on the use of prefabricated scaffolds on which cells are seeded. The self-assembly protocol has recently produced organ-specific human-derived three-dimensional models without the need for exogenous material. This strategy will help to achieve the 3R principles.

The Effect of Nanofillers on the Functional Properties of Biopolymer-based Films: A Review

Waste from non-degradable plastics is becoming an increasingly serious problem. Therefore, more and more research focuses on the development of materials with biodegradable properties. Bio-polymers are excellent raw materials for the production of such materials. Bio-based biopolymer films reinforced with nanostructures have become an interesting area of research. Nanocomposite films are a group of materials that mainly consist of bio-based natural (e.g., chitosan, starch) and synthetic (e.g., poly(lactic acid)) polymers and nanofillers (clay, organic, inorganic, or carbon nanostructures), with different properties. The interaction between environmentally friendly biopolymers and nanofillers leads to the improved functionality of nanocomposite materials. Depending on the properties of nanofillers, new or improved properties of nanocomposites can be obtained such as: barrier properties, improved mechanical strength, antimicrobial, and antioxidant properties or thermal stability. This review compiles information about biopolymers used as the matrix for the films with nanofillers as the active agents. Particular emphasis has been placed on the influence of nanofillers on functional properties of biopolymer films and their possible use within the food industry and food packaging systems. The possible applications of those nanocomposite films within other industries (medicine, drug and chemical industry, tissue engineering) is also briefly summarized.