Biomimetic biphasic scaffolds in osteochondral tissue engineering: Their composition, structure and consequences.

Approaches to the design and construction of biomimetic scaffolds for osteochondral tissue, show increasing advances. Considering the limitations of this tissue in terms of repair and regeneration, there is a need to develop appropriately designed scaffolds. A combination of biodegradable polymers especially natural polymers and bioactive ceramics, shows promise in this field. Due to the complicated architecture of this tissue, biphasic and multiphasic scaffolds containing two or more different layers, could mimic the physiology and function of this tissue with a higher degree of similarity. The purpose of this review article is to discuss the approaches focused on the application of biphasic scaffolds for osteochondral tissue engineering, common methods of combining layers and the ultimate consequences of their use in patients were discussed.

Physical, mechanical, and biological performance of chitosan-based nanocomposite coating deposited on the polycaprolactone-based 3D printed scaffold: Potential application in bone tissue engineering.

Recently, coating on composite scaffolds has attracted many researchers' attention to improve scaffolds' properties. In this research, a 3D printed scaffold was fabricated from polycaprolactone (PCL)/magnetic mesoporous bioactive glass (MMBG)/alumina nanowire (Al2O3, Optimal percentage 5 %) (PMA) and then coated with chitosan (Cs)/multi-walled carbon nanotubes (MWCNTs) by an immersion coating method. Structural analyses such as XRD and ATR-FTIR confirmed the presence of Cs and MWCNTs in the coated scaffolds. The SEM results of the coated scaffolds showed homogeneous three-dimensional structures with interconnected pores compared to the uncoated scaffolds. The coated scaffolds exhibited an increase in compression strength (up to 16.1 MPa) and compressive modulus (up to 40.83 MPa), improved surface hydrophilicity (up to 32.69°), and decrease in degradation rate (68 % remaining weight) compared to the uncoated scaffolds. The increase in apatite formation in the scaffold coated with Cs/MWCNTs was confirmed by SEM, EDAX, and XRD tests. Coating the PMA scaffold with Cs/MWCNTs leads to the viability and proliferation of MG-63 cells and more secretion of alkaline phosphatase and Ca activity, which can be introduced as a suitable candidate for use in bone tissue engineering.

Electro-conductive 3D printed polycaprolactone/gold nanoparticles nanocomposite scaffolds for myocardial tissue engineering.

The human's heart cannot regenerate after a wound by itself. So myocardial tissue can be damaged, leading to acute inflammation and scar. To overcome this issue, three dimensional (3D) scaffolds with appropriate properties have been proposed. In this study, Poly ε-caprolactone (PCL)/Gold nanoparticles (GNPs) nanocomposite scaffolds containing 0, 0.25 and 0.5 wt% GNPs were prepared by 3-D printing by using Fused Deposition Modeling (FDM) technique. Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Fourier transform-infrared spectroscopy (FTIR-ATR), and X-ray diffraction (XRD) were then used to characterize the scaffolds. Also, mechanical properties, electrical conductivity, contact angle, and thermal behavior of the scaffolds were measured. According to the results, the scaffold containing 0.5 wt% GNPs corroborated optimal properties including appropriate mechanical properties, adequate wettability and suitable electrical conductivity for cardiovascular application, as compressive strength and electrical conductivity were increased approximately by 9.1% and 25%, respectively. In contrast, contact angle was decreased about 38%, which caused the scaffolds' hydrophilicity. Overall the electrocunductive 3D PCL/GNPs 0.5 wt% scaffold could be developed with the control of some parameters that could be well implemented by this fabrication method; also, the addition of GNPs to improve some properties can be regarded as a promising candidate for myocardial tissue engineering.

Introducing a flexible drug delivery system based on poly(glycerol sebacate)-urethane and its nanocomposite: potential application in the prevention and treatment of oral diseases.

In this study, a novel biopolymer based on poly(glycerol sebacic)-urethane (PGS-U) and its nanocomposites containing Cloisite@30B were synthesized by facile approach in which the crosslinking was created by aliphatic hexamethylene diisocyanate (HDI) at room temperature and 80 °C. Moreover, metronidazole and tetracycline drugs were selected as target drugs and loaded into PGSU based nanocomposites. A uniform and continuous microstructure with smooth surface is observed in the case of pristine PGS-U sample. The continuity of microstructure is observed in the case of all bionanocomposites. XRD result confirmed an intercalated morphology for PGSU containing 5 wt% of clay nanoparticles with a d-spacing 3.4 nm. The increment of nanoclay content up to 5%, the ultimate tensile stress and elastic modulus were obtained nearly 0.32 and 0.83 MPa, which the latter was more than eight-fold than that of pristine PGS-U. A sustained release for both dugs was observed by 200 h. The slowest and controlled drug release rate was determined in the case of PGSU containing 5 wt% clay and cured at 80 °C. A non-Fickian diffusion can be concluded in the case of tetracycline release via PGS-U/nanoclay bionanocomposites, while a Fickian process was detected in the case of metronidazole release by PGS-U/nanoclay bionanocomposites. As a result, the designed scaffold showed high flexibility, which makes it an appropriate option for utilization in the treatment of periodontal disease.

Conductive Biomaterials as Substrates for Neural Stem Cells Differentiation towards Neuronal Lineage Cells.

The injuries and defects in the central nervous system are the causes of disability and death of an affected person. As of now, there are no clinically available methods to enhance neural structural regeneration and functional recovery of nerve injuries. Recently, some experimental studies claimed that the injuries in brain can be repaired by progenitor or neural stem cells located in the neurogenic sites of adult mammalian brain. Various attempts have been made to construct biomimetic physiological microenvironment for neural stem cells to control their ultimate fate. Conductive materials have been considered as one the best choices for nerve regeneration due to the capacity to mimic the microenvironment of stem cells and regulate the alignment, growth, and differentiation of neural stem cells. The review highlights the use of conductive biomaterials, e.g., polypyrrole, polyaniline, poly(3,4-ethylenedioxythiophene), multi-walled carbon nanotubes, single-wall carbon nanotubes, graphene, and graphite oxide, for controlling the neural stem cells activities in terms of proliferation and neuronal differentiation. The effects of conductive biomaterials in axon elongation and synapse formation for optimal repair of central nervous system injuries are also discussed.

Review of Bioprinting in Regenerative Medicine: Naturally Derived Bioinks and Stem Cells.

Regenerative medicine offers the potential to repair or substitute defective tissues by constructing active tissues to address the scarcity and demands for transplantation. The method of forming 3D constructs made up of biomaterials, cells, and biomolecules is called bioprinting. Bioprinting of stem cells provides the ability to reliably recreate tissues, organs, and microenvironments to be used in regenerative medicine. 3D bioprinting is a technique that uses several biomaterials and cells to tailor a structure with clinically relevant geometries and sizes. This technique's promise is demonstrated by 3D bioprinted tissues, including skin, bone, cartilage, and cardiovascular, corneal, hepatic, and adipose tissues. Several bioprinting methods have been combined with stem cells to effectively produce tissue models, including adult stem cells, embryonic stem cells (ESCs), induced pluripotent stem cells (iPSCs), and differentiation techniques. In this review, technological challenges of printed stem cells using prevalent naturally derived bioinks (e.g., carbohydrate polymers and protein-based polymers, peptides, and decellularized extracellular matrix), recent advancements, leading companies, and clinical trials in the field of 3D bioprinting are delineated.

Preparation of superabsorbent eco-friendly semi-interpenetrating network based on cross-linked poly acrylic acid/xanthan gum/graphene oxide (PAA/XG/GO): Characterization and dye removal ability.

In this work, a novel environmentally friendly semi-interpenetrating anionic hydrogel based on Xanthan gum/cross-linked polyacrylic acid/graphene oxide was prepared as superabsorbent for removing methylene blue as cationic dye from the water. Acrylic acid (AA) was crosslinked in xanthan (XG)/graphene oxide (GO) solution by a novel synthetic acrylic-urethane crosslinker (MS). Various analyses such as SEM, FT-IR, 1H NMR, XRD, and TGA were used to study morphology, structure, and thermal stability of MS and semi-IPNs. The synthesized hydrogels showed pH-sensitive behavior in water uptake, with the highest and lowest swelling in alkaline and acidic media, respectively. The nanocomposites had better dimension stability and dye adsorption with increasing GO from 0 to 1%. Hydrogel containing 1% GO showed 485% and 88.5% swelling and dye adsorption efficiency, respectively. Different kinetic models including 1st order, 2nd order, intra-particle diffusion, and Elovich kinetics were studied. All models except 2nd order model are in good agreement with the experimental data. GO-containing hydrogels had a significant effect on methylene blue adsorption and this effect increased with an increase in the amount of GO. PAA/XG/GO hydrogels can be introduced as an eco-friendly adsorbent with high efficiency for the removal of cationic dye pollutions.

Antibacterial superhydrophobic polyvinyl chloride surfaces via the improved phase separation process using silver phosphate nanoparticles.

This study aims to induce antibacterial and superhydrophobic properties on the surface of thermoplastic polyurethane (TPU) sheets via an improved phase separation process through application of polyvinyl chloride (PVC) thin films. Porous PVC thin films were produced using different amounts of ethanol as nonsolvent. However, the created porosity was not sufficient to achieve superhydrophobicity. To improve the phase separation process, the silver phosphate nanoparticles were first synthesized and then added to the solution. According to scanning electron microscopy and X-ray photoelectron spectroscopy results, the nanoparticles were majorly localized at the bulk of PVC films. A direct relationship was found between the level of porosity and superhydrophobicity. An exceedingly high amount of nanoparticles had a deteriorating influence on porosity and superhydrophobicity. The optimum sample was found to be durable against liquids with different pH values. In contrast to the good resistance of superhydrophobic sample at elevated temperatures (80 °C), a sticky behavior was obtained upon exposure to 120 °C. The level of bacterial adhesion for the superhydrophobic sample was drastically declined (>99%) with respect to the pure PVC film in case of S. aureus and E. coli bacteria after an incubation time of 24 h. In conclusion, the hybrid of superhydrophobic behavior and an antibacterial material such as silver phosphate nanoparticles exhibited a promising potential in achieving antibacterial surfaces.