Zn doped CaP coatings used for controlling the degradation rate of MgCa1 alloy: In vitro anticorrosive properties, sterilization and bacteria/cell-material interactions.

The purpose of this study was to investigate the effect of Zn doped CaP coatings prepared by micro-arc oxidation method, as a possible approach to control MgCa1 alloy degradation. All the prepared coatings comprised a calcium deficient CaP phase. The control in this evaluation was performed with undoped CaP coating in SBF solution at body temperature (37 ± 0.5°C). The investigation involved determination of microchemical, mechanical, morphological, properties along with anticorrosive, cytocompatibility and antibacterial efficacy. The effect of sterilization process on the properties of the surfaces was also investigated. The results showed that the addition of Zn into CaP increased the corrosion resistance of MgCa1 alloy. Moreover, the adhesion strength of the coatings to MgCa1 alloy was enhanced by Zn addition. In cytotoxicity testing of the samples, extracts of the samples in MEM were incubated with L929 cells and malformation, degeneration and lysis of the cells were examined microscopically after 72 h. The results showed that all samples were cytocompatible. The degradation of MgCa1 alloy in the simulated body fluids (SBF) or DMEM was decreased by coating with CaP. Moreover, the degradation rate of CaP was further decreased by adding a small amount of Zn into the CaP matrix. The samples having CaP coatings and Zn doped CaP coating demonstrated antibacterial efficacy against E.coli. As a result, coating of magnesium alloy with Zn-doped CaP decreased the degradation rate, increased the corrosion resistance, cytocompatibility and the antibacterial effects of the alloys.

Novel additive manufacturing applications for communicable disease prevention and control: focus on recent COVID-19 pandemic.

COVID-19 disease caused by the SARS-CoV-2 virus has had serious adverse effects globally in 2020 which are foreseen to extend in 2021, as well. The most important of these effects was exceeding the capacity of the healthcare infrastructures, and the related inability to meet the need for various medical equipment especially within the first months of the crisis following the emergence and rapid spreading of the virus. Urgent global demand for the previously unavailable personal protective equipment, sterile disposable medical supplies as well as the active molecules including vaccines and drugs fueled the need for the coordinated efforts of the scientific community. Amid all this confusion, the rapid prototyping technology, 3D printing, has demonstrated its competitive advantage by repositioning its capabilities to respond to the urgent need. Individual and corporate, amateur and professional all makers around the world with 3D printing capacity became united in effort to fill the gap in the supply chain until mass production is available especially for personal protective equipment and other medical supplies. Due to the unexpected, ever-changing nature of the COVID-19 pandemic-like all other potential communicable diseases-the need for rapid design and 3D production of parts and pieces as well as sterile disposable medical equipment and consumables is likely to continue to keep its importance in the upcoming years. This review article summarizes how additive manufacturing technology can contribute to such cases with special focus on the recent COVID-19 pandemic.

Myogenic Differentiation of ASCs Using Biochemical and Biophysical Induction.

Adipose-derived stem/stromal cells (ASCs) constitute a very promising source for cell therapy and tissue engineering approaches as they can be easily obtained in large quantities with comparatively minimal patient discomfort. Moreover, ASCs have multilineage differentiation capacity. Among these, differentiation capacity along the myogenic lineage is of particular interest since myogenic precursors are scarce and obtaining a large number of cells from skeletal muscle biopsies is difficult. Here, we describe a method to effectively induce ASC myogenesis through the combination of biochemical (cocktail including 5-azacytidine and horse serum) and biophysical (dynamic culture via uniaxial cyclic strain) stimulation. This method results in multinucleated cells that are positive in myogenic markers including Pax 3/7, desmin, myoD, and myosin heavy chain.

Infrapatellar Fat Pad-Derived Stem Cell-Based Regenerative Strategies in Orthopedic Surgery.

Infrapatellar fat pad is a densely vascularized and innervated extrasynovial tissue that fills the anterior knee compartment. It plays a role in knee biomechanics as well as constitutes a source of stem cells for regeneration after knee injury. Infrapatellar fat pad-derived stem cells (IPFP-ASCs) possess enhanced and age-independent differentiation capacity as compared to other stem cells, which makes them a very promising candidate in stem cell-based regenerative therapy. The aims of this review are to outline the latest advances and potential trends in using IPFP-ASCs and to emphasize the advantages over other sources of stem cells for applications in orthopedic surgery.

Scaffold pore size modulates in vitro osteogenesis of human adipose-derived stem/stromal cells.

Trabecular bone has an interconnected porous structure, which influences cellular responses, biochemical transport and mechanical strength. Appropriately mimicking this structural organization in biomaterial scaffolds can facilitate more robust bone tissue regeneration and integration by providing a native microenvironment to the cells. This study examined the effect of pore size on human adipose-derived stem/stromal cell (ASC) osteogenesis within poly(ε-caprolactone) (PCL) scaffolds. Scaffold pore size was controlled by porogen leaching of custom-made paraffin particles with three different size ranges: P200 (< 500 µm), P500 (500-1000 µm), and P1000 (1000-1500 µm). Scaffolds produced by leaching these particles exhibited highly interconnected pores and rough surface structures that were favorable for cell attachment and ingrowth. The osteogenic response of ASCs was evaluated following 3 weeks of in vitro culture using biochemical (ALP, Ca(2+)/DNA content), mechanical (compression test) and histological (H&E and von Kossa staining) analyses. It was observed that while the total number of cells was similar for all scaffolds, the cell distributions and osteogenic properties were affected by the scaffold pore size. ASCs were able to bridge smaller pores and grow uniformly within these scaffolds (P200) while they grew as a layer along the periphery of the largest pores (P1000). The cell-biomaterial interactions specific to the latter case led to enhanced osteogenic responses. The ALP activity and Ca(2+) deposition were doubled in P1000 scaffolds as compared to P200 scaffolds. A significant difference was observed between the compressive strength of unseeded and seeded P1000 scaffolds. Therefore, we demonstrated that the use of scaffolds with pores that are in the range of 1 mm enhances in vitro ASC osteogenesis, which may improve their performance in engineered bone substitutes.

Engineering anatomically shaped vascularized bone grafts with hASCs and 3D-printed PCL scaffolds.

The treatment of large craniomaxillofacial bone defects is clinically challenging due to the limited availability of transplantable autologous bone grafts and the complex geometry of the bones. The ability to regenerate new bone tissues that faithfully replicate the anatomy would revolutionize treatment options. Advances in the field of bone tissue engineering over the past few decades offer promising new treatment alternatives using biocompatible scaffold materials and autologous cells. This approach combined with recent advances in three-dimensional (3D) printing technologies may soon allow the generation of large, bioartificial bone grafts with custom, patient-specific architecture. In this study, we use a custom-built 3D printer to develop anatomically shaped polycaprolactone (PCL) scaffolds with varying internal porosities. These scaffolds are assessed for their ability to support induction of human adipose-derived stem cells (hASCs) to form vasculature and bone, two essential components of functional bone tissue. The development of functional tissues is assessed in vitro and in vivo. Finally, we demonstrate the ability to print large mandibular and maxillary bone scaffolds that replicate fine details extracted from patient's computed tomography scans. The findings of this study illustrate the capabilities and potential of 3D printed scaffolds to be used for engineering autologous, anatomically shaped, vascularized bone grafts.

A biomimetic growth factor delivery strategy for enhanced regeneration of iliac crest defects.

The importance of provision of growth factors in the engineering of tissues has long been shown to control the behavior of the cells within the construct and several approaches were applied toward this end. In nature, more than one type of growth factor is known to be effective during the healing of tissue defects and their peak concentrations are not always simultaneous. One of the most recent strategies includes the delivery of a combination of growth factors with the dose and timing to mimic the natural regeneration cascade. The sequential delivery of bone morphogenetic proteins BMP-2 and BMP-7 which are early and late appearing factors during bone regeneration, respectively, was shown in vitro to enhance osteoblastic differentiation of bone marrow derived mesenchymal stem cells. In the present study, the aim was to study the effectiveness of this delivery strategy in a rabbit iliac crest model. 3D plotted poly(ε-caprolactone) scaffolds were loaded with BMP carrying nanoparticles to achieve: (a) single BMP-2 or BMP-7 delivery, and (b) their combined delivery in a simultaneous or (c) sequential (biomimetic) fashion. After eight weeks of implantation, computed tomography and biomechanical tests showed better mineralized matrix formation and bone-implant union strength at the defect site in the case of sequential delivery compared to single or simultaneous delivery modes. Bone mineral density (BMD) and push-out stress were: 33.65±2.25 g cm(-3) and 14.5±2.28 MPa, respectively, and almost 2.5 fold higher in comparison to those without growth factors (BMD: 14.14±1.21 g cm(-3); PS: 6.59±0.65 MPa). This study, therefore, supports those obtained in vitro and emphasizes the importance of mimicking the natural timing of bioavailability of osteogenic factors in improving the regeneration of critical-sized bone defects.