Design, Fabrication, and Application of Mini-Scaffolds for Cell Component in Tissue Engineering

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Commercial articulated collaborative in situ 3D bioprinter for skin wound healing

In situ bioprinting is one of the most clinically relevant techniques in the emerging bioprinting technology because it could be performed directly on the human body in the operating room and it does not require bioreactors for post-printing tissue maturation. However, commercial in situ bioprinters are still not available on the market. In this study, we demonstrated the benefit of the originally developed first commercial articulated collaborative in situ bioprinter for the treatment of full-thickness wounds in rat and porcine models. We used an articulated and collaborative robotic arm from company KUKA and developed original printhead and correspondence software enabling in situ bioprinting on curve and moving surfaces. The results of in vitro and in vivo experiments show that in situ bioprinting of bioink induces a strong hydrogel adhesion and enables printing on curved surfaces of wet tissues with a high level of fidelity. The in situ bioprinter was convenient to use in the operating room. Additional in vitro experiments (in vitro collagen contraction assay and in vitro 3D angiogenesis assay) and histological analyses demonstrated that in situ bioprinting improves the quality of wound healing in rat and porcine skin wounds. The absence of interference with the normal process of wound healing and even certain improvement in the dynamics of this process strongly suggests that in situ bioprinting could be used as a novel therapeutic modality in wound healing.publishersversionPeer reviewe

Bulk Oriented UHMWPE/FMWCNT Films for Tribological Applications

Bulk oriented films based on ultrahigh molecular weight polyethylene (UHMWPE) with a drawing ratio of 35 were prepared by using a low solvent concentration. Bulk oriented films were filled with fluorinated multi-walled carbon nanotubes (FMWCNTs). The structure of bulk oriented films on UHMWPE, which were manufactured at different stages of orientation, was investigated by scanning electron microscope (SEM) and differential scanning calorimetry (DSC). The addition of FMWCNTs at a concentration of 0.05 wt % in bulk oriented UHMWPE films led to an increase in the tensile strength by 10% (up to 1020 ± 23 MPa) compared to unfilled oriented films. However, the addition of FMWCNTs at a concentration of more than 0.5 wt % led to a decrease in tensile strength due to excessive accumulation of nanotubes and hindering of self-diffusion of UHMWPE macromolecules. The multiple increase in tensile strength, doubling the hardness, the formation of fibrillar structure, and the presence of carbon nanotubes led to a significant increase in tribological properties in bulk oriented films. Bulk oriented UHMWPE/1% FMWCNT films can be operated at a maximum contact pressure that is 18 times higher and exhibit a specific wear rate more than an order of magnitude and less than the traditional UHMWPE of isotropic structure. Bulk oriented UHMWPE/1% FMWCNT films have an extremely low dry coefficient of friction (COF) of 0.075 at a contact pressure of 31 MPa. The developed bulk oriented films can be used for manufacturing frictional surfaces for sliding bearings, or for acetabular cups for knee and hip endoprostheses

Formation of ethylene-vinyl acetate composites filled with Al–Cu–Fe and Al–Cu–Cr quasicrystallline particles

Icosahedral Al65Cu23Fe12 and decagonal Al73Cu11Cr16 quasicrystalline powders were synthesized by the mechanical alloying and subsequent annealing. Morphology evolution at mechanical alloying of Al-based powders was found to be determined by competition between cold welding and fracture mechanisms. Mechanical alloying results in formation of coarse agglomerates consisting of fine particles. The chemical binding between the polymer matrix and quasicrystals, destruction of agglomerated at extrusion, and the uniform distribution of quasicrystals over the polymer melt were provided by surface treatment of quasicrystalline particles with silanes. The highly filled (up to 60 wt%) ethylene-vinyl acetate/quasicrystals composites were obtained, and their rheological characteristics were studied. It was shown that the fluidity of the melt is retained at a high level providing uniform distribution of quasicrystalline particles over the polymer. Keywords: Quasicrystals, Ethylene-vinyl acetate, Silanes, Mechanical alloying, Extrusio

Auxetic Metamaterials for Biomedical Devices: Current Situation, Main Challenges, and Research Trends

Auxetic metamaterials are characterized by a negative Poisson ratio (NPR) and display an unexpected property of lateral expansion when stretched and densification when compressed. Auxetic properties can be achieved by designing special microstructures, hence their classification as metamaterials, and can be manufactured with varied raw materials and methods. Since work in this field began, auxetics have been considered for different biomedical applications, as some biological tissues have auxetic-like behaviour due to their lightweight structure and morphing properties, which makes auxetics ideal for interacting with the human body. This research study is developed with the aim of presenting an updated overview of auxetic metamaterials for biomedical devices. It stands out for providing a comprehensive view of medical applications for auxetics, including a focus on prosthetics, orthotics, ergonomic appliances, performance enhancement devices, in vitro medical devices for interacting with cells, and advanced medicinal clinical products, especially tissue engineering scaffolds with living cells. Innovative design and simulation approaches for the engineering of auxetic-based products are covered, and the relevant manufacturing technologies for prototyping and producing auxetics are analysed, taking into consideration those capable of processing biomaterials and enabling multi-scale and multi-material auxetics. An engineering design rational for auxetics-based medical devices is presented with integrative purposes. Finally, key research, development and expected technological breakthroughs are discussed

Design, Fabrication, and Application of Mini-Scaffolds for Cell Components in Tissue Engineering

The concept of “lockyballs” or interlockable mini-scaffolds fabricated by two-photon polymerization from biodegradable polymers for the encagement of tissue spheroids and their delivery into the desired location in the human body has been recently introduced. In order to improve control of delivery, positioning, and assembly of mini-scaffolds with tissue spheroids inside, they must be functionalized. This review describes the design, fabrication, and functionalization of mini-scaffolds as well as perspectives on their application in tissue engineering for precisely controlled cell and mini-tissue delivery and patterning. The development of functionalized mini-scaffolds advances the original concept of “lockyballs” and opens exciting new prospectives for mini-scaffolds’ applications in tissue engineering and regenerative medicine and their eventual clinical translation

Hydrogel-Inducing Graphene-Oxide-Derived Core–Shell Fiber Composite for Antibacterial Wound Dressing

The study reveals the polymer–crosslinker interactions and functionality of hydrophilic nanofibers for antibacterial wound coatings. Coaxial electrospinning leverages a drug encapsulation protocol for a core–shell fiber composite with a core derived from polyvinyl alcohol and polyethylene glycol with amorphous silica (PVA-PEG-SiO2), and a shell originating from polyvinyl alcohol and graphene oxide (PVA-GO). Crosslinking with GO and SiO2 initiates the hydrogel transition for the fiber composite upon contact with moisture, which aims to optimize the drug release. The effect of hydrogel-inducing additives on the drug kinetics is evaluated in the case of chlorhexidine digluconate (CHX) encapsulation in the core of core–shell fiber composite PVA-PEG-SiO2-1x-CHX@PVA-GO. The release rate is assessed with the zero, first-order, Higuchi, and Korsmeyer–Peppas kinetic models, where the inclusion of crosslinking silica provides a longer degradation and release rate. CHX medicated core–shell composite provides sustainable antibacterial activity against Staphylococcus aureus