Biological and Tribological Assessment of Poly(Ethylene Oxide Terephthalate)/Poly(Butylene Terephthalate), Polycaprolactone, and Poly (L\DL) Lactic Acid Plotted Scaffolds for Skeletal Tissue Regeneration

Melt Electrowriting of Elastic Scaffolds Using PEOT-PBT Multi-block Copolymer

Melt electrowriting (MEW) is a powerful additive manufacturing technique to produce tissue engineering scaffolds. Despite its strength, it is limited by a small number of processable polymers. Therefore, to broaden the library of materials for MEW, we investigated the printability of poly(ethylene oxide terephthalate)-poly(butylene terephthalate) (PEOT-PBT), a thermoplastic elastomer. The effect of different printing parameters and material thermal degradation are studied. It is observed that the material is stable for >60 min at a printing temperature of 195 °C in a nitrogen environment. Next, two types of designs are printed and characterized: mesh-like and semi-random scaffolds. For both types of designs, PEOT-PBT scaffolds reveal a higher yield strain, and lower Young's modulus as compared to control polycaprolactone scaffolds. Biological studies performed using mouse embryonic fibroblasts (NIH-3T3) show good cell viability and metabolic activity on all print scaffolds. SEM imaging reveals actively migrating cells on PEOT-PBT mesh scaffolds after 24 h of culture and 98.87% of pore bridging by cells after 28 days of culture. Immunofluorescence staining shows decreased expression of alpha-smooth muscle actin from day 14 to day 28 in PEOT-PBT mesh scaffolds. Overall, it is shown that melt electrowritten PEOT-PBT scaffolds have great potential for soft tissue regeneration.

Solvent-cast 3D printing with molecular weight polymer blends to decouple effects of scaffold architecture and mechanical properties on mesenchymal stromal cell fate

The biochemical and physical properties of a scaffold can be tailored to elicit specific cellular responses. However, it is challenging to decouple their individual effects on cell-material interactions. Here, we solvent-cast 3D printed different ratios of high and low molecular weight (MW) poly(caprolactone) (PCL) to fabricate scaffolds with significantly different stiffnesses without affecting other properties. Ink viscosity was used to match processing conditions between inks and generate scaffolds with the same surface chemistry, crystallinity, filament diameter, and architecture. Increasing the ratio of low MW PCL resulted in a significant decrease in modulus. Scaffold modulus did not affect human mesenchymal stromal cell (hMSC) differentiation under osteogenic conditions. However, hMSC response was significantly affected by scaffold stiffness in chondrogenic media. Low stiffness promoted more stable chondrogenesis whereas high stiffness drove hMSC progression toward hypertrophy. These data illustrate how this versatile platform can be used to independently modify biochemical and physical cues in a single scaffold to synergistically enhance desired cellular response.

The biological applications of DNA nanomaterials: current challenges and future directions

DNA, a genetic material, has been employed in different scientific directions for various biological applications as driven by DNA nanotechnology in the past decades, including tissue regeneration, disease prevention, inflammation inhibition, bioimaging, biosensing, diagnosis, antitumor drug delivery, and therapeutics. With the rapid progress in DNA nanotechnology, multitudinous DNA nanomaterials have been designed with different shape and size based on the classic Watson-Crick base-pairing for molecular self-assembly. Some DNA materials could functionally change cell biological behaviors, such as cell migration, cell proliferation, cell differentiation, autophagy, and anti-inflammatory effects. Some single-stranded DNAs (ssDNAs) or RNAs with secondary structures via self-pairing, named aptamer, possess the ability of targeting, which are selected by systematic evolution of ligands by exponential enrichment (SELEX) and applied for tumor targeted diagnosis and treatment. Some DNA nanomaterials with three-dimensional (3D) nanostructures and stable structures are investigated as drug carrier systems to delivery multiple antitumor medicine or gene therapeutic agents. While the functional DNA nanostructures have promoted the development of the DNA nanotechnology with innovative designs and preparation strategies, and also proved with great potential in the biological and medical use, there is still a long way to go for the eventual application of DNA materials in real life. Here in this review, we conducted a comprehensive survey of the structural development history of various DNA nanomaterials, introduced the principles of different DNA nanomaterials, summarized their biological applications in different fields, and discussed the current challenges and further directions that could help to achieve their applications in the future.

Construction and application of textile-based tissue engineering scaffolds: a review

Tissue engineering (TE) provides a practicable method for tissue and organ repair or substitution. As the most important component of TE, a scaffold plays a critical role in providing a growing environment for cell proliferation and functional differentiation as well as good mechanical support. And the restorative effects are greatly dependent upon the nature of the scaffold including the composition, morphology, structure, and mechanical performance. Medical textiles have been widely employed in the clinic for a long time and are being extensively investigated as TE scaffolds. However, unfortunately, the advantages of textile technology cannot be fully exploited in tissue regeneration due to the ignoring of the diversity of fabric structures. Therefore, this review focuses on textile-based scaffolds, emphasizing the significance of the fabric design and the resultant characteristics of cell behavior and extracellular matrix reconstruction. The structure and mechanical behavior of the fabrics constructed by various textile techniques for different tissue repairs are summarized. Furthermore, the prospect of structural design in the TE scaffold preparation was anticipated, including profiled fibers and some unique and complex textile structures. Hopefully, the readers of this review would appreciate the importance of structural design of the scaffold and the usefulness of textile-based TE scaffolds in tissue regeneration.

The Rheology of PEOT/PBT Block Copolymers in the Melt State and in the Thermally-Induced Sol/Gel Transition. Implications on the 3D-Printing Bio-Scaffold Process

Poly(ethyleneoxideterephthalate)/poly(butyleneterephthalate) (PEOT/PBT) segmented block copolymers are widely used for the manufacturing of 3D-printed bio-scaffolds, due to a combination of several properties, such as cell viability, bio-compatibility, and bio-degradability. Furthermore, they are characterized by a relatively low viscosity at high temperatures, which is desired during the injection stages of the printing process. At the same time, the microphase separated morphology generated by the demixing of hard and soft segments at intermediate temperatures allows for a quick transition from a liquid-like to a solid-like behavior, thus favoring the shaping and the dimensional stability of the scaffold. In this work, for the first time, the rheology of a commercial PEOT/PBT material is studied over a wide range of temperatures encompassing both the melt state and the phase transition regime. Non-isothermal viscoelastic measurements under oscillatory shear flow allow for a quantitative determination of the material processability in the melt state. Additionally, isothermal experiments below the order⁻disorder temperature are used to determine the temperature dependence of the phase transition kinetics. The importance of the rheological characterization when designing the 3D-printing scaffold process is also discussed.

Poly(propylene fumarate) stars, using architecture to reduce the viscosity of 3D printable resins

Additive manufacturing is changing tissue engineering by offering pathways to otherwise unattainable, highly complex scaffold morphologies.

Acrylic Acid Plasma Coated 3D Scaffolds for Cartilage tissue engineering applications

The current generation of tissue engineered additive manufactured scaffolds for cartilage repair shows high potential for growing adult cartilage tissue. This study proposes two surface modification strategies based on non-thermal plasma technology for the modification of poly(ethylene oxide terephthalate/poly(butylene terephthalate) additive manufactured scaffolds to enhance their cell-material interactions. The first, plasma activation in a helium discharge, introduced non-specific polar functionalities. In the second approach, a carboxylic acid plasma polymer coating, using acrylic acid as precursor, was deposited throughout the scaffolds. Both surface modifications were characterized by significant changes in wettability, linked to the incorporation of new oxygen-containing functional groups. Their capacity for chondrogenesis was studied using ATDC5 chondroblasts as a model cell-line. The results demonstrate that the carboxylic acid-rich plasma coating had a positive effect on the generation of the glucoaminoglycans (GAG) matrix and stimulated the migration of cells throughout the scaffold. He plasma activation stimulated the formation of GAGs but did not stimulate the migration of chondroblasts throughout the scaffolds. Both plasma treatments spurred chondrogenesis by favoring GAG deposition. This leads to the overall conclusion that acrylic acid based plasma coatings exhibit potential as a surface modification technique for cartilage tissue engineering applications.