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Tissue Engineering
... In recent years, biodegradable scaffolds have been widely used in tissue engineering (TE) applications [1][2][3][4]. An ideal TE scaffold is defined as a porous structure, which is biocompatible, bioactive and possesses adequate mechanical and physical properties, convergent to the tissues in place of implantation [5][6][7]. Mimicking the complex architecture and mechanical properties of the native tissue is one of the most important paradigms in tissue engineering. 3D printing can be implemented to fulfill this criterion. ...
Biodegradable 3D-printed polycaprolactone scaffolds for bone tissue engineering applications have been extensively studied as they can provide an attractive porous architecture mimicking natural bone, with tunable physical and mechanical properties enhancing positive cellular response. The main drawbacks of polycaprolactone-based scaffolds, limiting their applications in tissue engineering are: their hydrophobic nature, low bioactivity and poor mechanical properties compared to native bone tissue. To overcome these issues, the surface of scaffolds is usually modified and covered with a ceramic layer. However, a detailed description of the adhesion forces of ceramic particles to the polymer surface of the scaffolds is still lacking. Our present work is focused on obtaining PCL-based composite scaffolds to strengthen the architecture of the final product. In this manuscript, we report qualitative and quantitative evaluation of low temperature plasma modification followed by detailed studies of the adhesion forces between chemically attached ceramic layer and the surface of polycaprolactone-nanohydroxyapatite composite 3D-printed scaffolds. The results suggest modification-dependent alteration of the internal structure and morphology, as well as mechanical and physical scaffold properties recorded with atomic force microscopy. Moreover, changes in the material surface were followed by enhanced adhesion forces binding the ceramic layer to polymer-based scaffolds.
Composite materials in hydrogels state based on collagen and metal-organic frameworks (MOFs) have recently gained attention in tissue engineering due to the enhancement of their mechanical and bactericidal properties. In this work, composite hydrogels based on collagen crosslinked with polyurethane (derived from HDI or IPDI) and MOFs with aluminium as metallic center (MIL53-Al and BHET-Al MOFs) were synthesized by the microemulsion method. The physicochemical properties of these materials were characterized by WAXS, ATR-FTIR, TGA, reticulation by ninhydrin assay, degradation profiles varying pH and using a proteolytic medium, scanning electron microscopy and elemental mapping. At the same time, their in-vitro biocompatibility was tested by the hemolysis test, metabolic activity of fibroblasts by MTT assay, and the inhibition growth of pathogens like E. coli. It was found that the entanglement of collagen, polyurethane and MOFs was made by hydrogen and coordination bonds promoted by the chemical structure of the MOF, leading to a semi-crystalline rough surface with interconnected porosity and aggregates of round-shape, enhancing the mechanical, resistance to thermal degradation and biocompatibility. Interestingly, the better dispersion of MIL53-Al in the collagenic matrix with crosslinker based on HDI leads to a hemolytic capacity of 1.2%, a fibroblast viability of 169.4%, and an E. coli inhibition growth of 96.7%, a potential biomaterial to be used as a wound dressing for chronic wounds in the skin.
In the quest to improve both aesthetic and functional outcomes for patients, the clinical care of full-thickness cutaneous wounds has undergone significant development over the past decade. A shift from replacement to regeneration has prompted the development of skin substitute products, however, inaccurate replication of host tissue properties continues to stand in the way of realising the ultimate goal of scar-free healing. Advances in three-dimensional (3D) bioprinting and biomaterials used for tissue engineering have converged in recent years to present opportunities to progress this field. However, many of the proposed bioprinting strategies for wound healing involve lengthy in-vitro cell culture and construct maturation periods, employ complex deposition technologies, and lack credible point of care (POC) delivery protocols. In-situ bioprinting is an alternative strategy which can combat these challenges. In order to survive the journey to bedside, printing protocols must be curated, and biomaterials/cells selected which facilitate intraoperative delivery. In this review, the current status of in-situ 3D bioprinting systems for wound healing applications is discussed, highlighting the delivery methods employed, biomaterials/cellular components utilised and anticipated translational challenges. We believe that with the growth of collaborative networks between researchers, clinicians, commercial, ethical, and regulatory experts, in-situ 3D bioprinting has the potential to transform POC wound care treatment.
Efforts to heal damaged pulp tissue through tissue engineering have produced positive results in pilot trials. However, the differentiation between real regeneration and mere repair is not possible through clinical measures. Therefore, preclinical study models are still of great importance, both to gain insights into treatment outcomes on tissue and cell levels and to develop further concepts for dental pulp regeneration. This review aims at compiling information about different in vitro and in vivo ectopic, semiorthotopic, and orthotopic models. In this context, the differences between monolayer and three-dimensional cell cultures are discussed, a semiorthotopic transplantation model is introduced as an in vivo model for dental pulp regeneration, and finally, different animal models used for in vivo orthotopic investigations are presented.
The increasing population of patients with heart disease and the limited availability of organs for transplantation have encouraged multiple strategies to fabricate healthy implantable cardiac tissues. One of the main challenges in cardiac tissue engineering is to direct cell behaviors to form functional three-dimensional (3D) biomimetic constructs. This article provides a brief review on various cell sources used in cardiac tissue engineering and highlights the effect of scaffold-based signals such as topographical and biochemical cues and stiffness. Then, conventional and novel micro-engineered bioreactors for the development of functional cardiac tissues will be explained. Bioreactor-based signals including mechanical and electrical cues to control cardiac cell behavior will also be elaborated in detail. Finally, the application of computational fluid dynamics to design suitable bioreactors will be discussed. This review presents the current state-of-the-art, emerging directions and future trends that critically appraise the concepts involved in various approaches to direct cells for building functional hearts and heart parts.
A series of diamond-like carbon thin films was applied on AISI 316L stainless steel substrates through a pulsed-direct current plasma-enhanced chemical vapor deposition technique to study the effects of working parameters (bias voltage and deposition pressure) on the microstructure and biocorrosion resistance of films. Raman spectra indicated that under low bias voltage and higher deposition pressure, the films possess a higher amount of sp² structure, lower internal stress and an improved biocorrosion resistance due to a smooth and defect-free morphology. The lamellar sp² structure blocked a penetration of corrosive entities. The oxygen content of locally corroded areas (∼11·9 wt.%) was much higher than that of non-corroded areas (2·6 wt.%) corroborating galvanic corrosion between carbide and nitride phases. Moreover, by increasing the deposition pressure from 20 to 40 Pa, the internal stress decreased from 1·03 to 0·82 GPa. The results confirmed that it is possible to tailor the properties of the coatings such as structural composition and particularly biocorrosion resistance by the control over the working parameters. Such anticorrosive diamond-like coatings could benefit biomedical implants used for tissue regeneration.
A multichannel three-dimensional chip of a microfluidic cell culture which enables the simulation of organs is called an “organ on a chip” (OC). With the integration of many other technologies, OCs have been mimicking organs, substituting animal models, and diminishing the time and cost of experiments which is better than the preceding conventional in vitro models, which make them imperative tools for finding functional properties, pathological states, and developmental studies of organs. In this review, recent progress regarding microfluidic devices and their applications in cell cultures is discussed to explain the advantages and limitations of these systems. Microfluidics is not a solution but only an approach to create a controlled environment, however, other supporting technologies are needed, depending upon what is intended to be achieved. Microfluidic platforms can be integrated with additional technologies to enhance the organ on chip simulations. Besides, new directions and areas are mentioned for interested researchers in this field, and future challenges regarding the simulation of OCs are also discussed, which will make microfluidics more accurate and beneficial for biological applications.
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