An Experimental Study on the Mechanical and Biological Properties of Bio-Printed Alginate/Halloysite Nanotube/Methylcellulose/Russian Olive-Based Scaffolds

A comprehensive review on methods for promotion of mechanical features and biodegradation rate in amniotic membrane scaffolds

Amniotic membrane (AM) is a biological tissue that surrounds the fetus in the mother's womb. It has pluripotent cells, immune modulators, collagen, cytokines with anti-fibrotic and anti-inflammatory effect, matrix proteins, and growth factors. In spite of the biological characteristics, some results have been released in preventing the adhesion on traumatized surfaces. Application of the AM as a scaffold is limited due to its low biomechanical resistance and rapid biodegradation. Therefore, for using the AM during surgery, its modification by different methods such as cross-linking of the membrane collagen is necessary, because the cross-linking is an effective way to reduce the rate of biodegradation of the biological materials. In addition, their cross-linking is likely an efficient way to increase the tensile properties of the material, so that they can be easily handled or sutured. In this regard, various methods related to cross-linking of the AM subsuming the composite materials, physical cross-linking, and chemical cross-linking with the glutraldehyde, carbodiimide, genipin, aluminum sulfate, etc. are reviewed along with its advantages and disadvantages in the current work.

Fabrication and characterization of microstructure-controllable COL-HA-PVA hydrogels for cartilage repair

Polyvinyl alcohol (PVA) hydrogel has gained interest in cartilage repair because of its highly swollen, porosity, and viscoelastic properties. However, PVA has some deficiencies, such as its poor biocompatibility and microstructure. This research aimed to design novel hydroxyapatite (HA)-collagen (COL)-PVA hydrogels. COL was added to improve cell biocompatibility, and the microstructure of the hydrogels was controlled by fused deposition modeling (FDM). The feasibility of the COL-HA-PVA hydrogels in cartilage repair was evaluated by in vitro and in vivo experiments. The scanning electron microscopy results showed that the hybrid hydrogels had interconnected macropore structures that contained a COL reticular scaffold. The diameter of the macropore was 1.08-1.85 mm, which corresponds to the diameter of the denatured PVA column. The chondrocytes were then seeded in hydrogels to assess the cell viability and formation of the cartilage matrix. The in vitro results revealed excellent cellular biocompatibility. Osteochondral defects (8 mm in diameter and 8 mm in depth) were created in the femoral trochlear of goats, and the defects were implanted with cell-seeded hydrogels, cell-free hydrogels, or a blank control. The in vivo results showed that the COL-HA-PVA hydrogels effectively repaired cartilage defects, especially the conditions inoculated with chondrocyte in advance. This research suggests that the COL-HA-PVA hydrogels have promising application in cartilage repair.

Nanoclay Reinforced Biomaterials for Mending Musculoskeletal Tissue Disorders

Nanoclay-reinforced biomaterials have sparked a new avenue in advanced healthcare materials that can potentially revolutionize treatment of musculoskeletal defects. Native tissues display many important chemical, mechanical, biological, and physical properties that engineered biomaterials need to mimic for optimal tissue integration and regeneration. However, it is time-consuming and difficult to endow such combinatorial properties on materials via feasible and nontoxic procedures. Fortunately, a number of nanomaterials such as graphene, carbon nanotubes, MXenes, and nanoclays already display a plethora of material properties that can be transferred to biomaterials through a simple incorporation procedure. In this direction, the members of the nanoclay family are easy to functionalize chemically, they can significantly reinforce the mechanical performance of biomaterials, and can provide bioactive properties by ionic dissolution products to upregulate cartilage and bone tissue formation. For this reason, nanoclays can become a key component for future orthopedic biomaterials. In this review, we specifically focus on the rapidly decreasing gap between clinic and laboratory by highlighting their application in a number of promising in vivo studies.

Recent trends in natural polysaccharide based bioinks for multiscale 3D printing in tissue regeneration: A review

Biofabrication by three-dimensional (3D) printing has been an attractive technology in harnessing the possibility to print anatomical shaped native tissues with controlled architecture and resolution. 3D printing offers the possibility to reproduce complex microarchitecture of native tissues by printing live cells in a layer by layer deposition to provide a biomimetic structural environment for tissue formation and host tissue integration. Plant based biomaterials derived from green and sustainable sources have represented to emulate native physicochemical and biological cues in order to direct specific cellular response and formation of new tissues through biomolecular recognition patterns. This comprehensive review aims to analyze and identify the most commonly used plant based bioinks for 3D printing applications. An overview on the role of different plant based biomaterial of terrestrial origin (Starch, Nanocellulose and Pectin) and marine origin (Ulvan, Alginate, Fucoidan, Agarose and Carrageenan) used for 3D printing applications are discussed elaborately. Furthermore, this review will also emphasis in the functional aspects of different 3D printers, appropriate printing material, merits and demerits of numerous plant based bioinks in developing 3D printed tissue-like constructs. Additionally, the underlying potential benefits, limitations and future perspectives of plant based bioinks for tissue engineering (TE) applications are also discussed.

Tailorable Zinc-Substituted Mesoporous Bioactive Glass/Alginate-Methylcellulose Composite Bioinks

Bioactive glasses have been used for bone regeneration applications thanks to their excellent osteoconductivity, an osteostimulatory effect, and high degradation rate, releasing biologically active ions. Besides these properties, mesoporous bioactive glasses (MBG) are specific for their highly ordered mesoporous channel structure and high specific surface area, making them suitable for drug and growth factor delivery. In the present study, calcium (Ca) (15 mol%) in MBG was partially and fully substituted with zinc (Zn), known for its osteogenic and antimicrobial properties. Different MBG were synthesized, containing 0, 5, 10, or 15 mol% of Zn. Up to 7 wt.% of Zn-containing MBG could be mixed into an alginate-methylcellulose blend (algMC) while maintaining rheological properties suitable for 3D printing of scaffolds with sufficient shape fidelity. The suitability of these composites for bioprinting applications has been demonstrated with immortalized human mesenchymal stem cells. Uptake of Ca and phosphorus (P) (phosphate) ions by composite scaffolds was observed, while the released concentration of Zn2+ corresponded to the initial amount of this ion in prepared glasses, suggesting that it can be controlled at the MBG synthesis step. The study introduces a tailorable bioprintable material system suitable for bone tissue engineering applications.

Challenges on optimization of 3D-printed bone scaffolds

Advances in biomaterials and the need for patient-specific bone scaffolds require modern manufacturing approaches in addition to a design strategy. Hybrid materials such as those with functionally graded properties are highly needed in tissue replacement and repair. However, their constituents, proportions, sizes, configurations and their connection to each other are a challenge to manufacturing. On the other hand, various bone defect sizes and sites require a cost-effective readily adaptive manufacturing technique to provide components (scaffolds) matching with the anatomical shape of the bone defect. Additive manufacturing or three-dimensional (3D) printing is capable of fabricating functional physical components with or without porosity by depositing the materials layer-by-layer using 3D computer models. Therefore, it facilitates the production of advanced bone scaffolds with the feasibility of making changes to the model. This review paper first discusses the development of a computer-aided-design (CAD) approach for the manufacture of bone scaffolds, from the anatomical data acquisition to the final model. It also provides information on the optimization of scaffold's internal architecture, advanced materials, and process parameters to achieve the best biomimetic performance. Furthermore, the review paper describes the advantages and limitations of 3D printing technologies applied to the production of bone tissue scaffolds.

Methylcellulose – a versatile printing material that enables biofabrication of tissue equivalents with high shape fidelity

This minireview highlights the use of the polysaccharide methylcellulose for biofabrication applications. Its properties are useful for printing of dissolvable support structures as well as the development of novel bioinks.

Graphene oxide/alginate composites as novel bioinks for three-dimensional mesenchymal stem cell printing and bone regeneration applications

Three-dimensional (3D) cell printing is a versatile technique enabling the creation of 3D constructs containing hydrogel and cells in the desired shape or pattern. Bioinks exhibiting appropriate mechanical properties and biological activities to support cell growth and/or differentiation toward a specific lineage play critical roles in 3D cell printing and tissue engineering applications. Herein, we explored alginate/graphene oxide (GO) composites as bioinks for their potential to improve printability, structural stability, and osteogenic activities for osteogenic tissue engineering applications. The addition of GO (0.05-1.0 mg mL^-1) to 3% alginate significantly enhanced the printing performances of the alginate bioink. In addition, mesenchymal stem cells (MSCs) printed with alginate/GO showed good proliferation and higher survival in an oxidative stress environment. The 3D scaffolds printed with MSCs and alginate/GO demonstrated significantly enhanced osteogenic differentiation compared with those printed with MSCs and alginate. Overall, a bioink of 3% alginate and 0.5 mg mL^-1 GO showed the most balanced characteristics in terms of printability, structural stability, and osteogenic induction of the printed MSCs. Alginate/GO composite bioinks will be useful for bioprinting research for various tissue engineering applications.

Waste Autochthonous Tuscan Olive Leaves (Olea europaea var. Olivastra seggianese) as Antioxidant Source for Biomedicine

Olive leaf extract (OLE) can be obtained as biowaste and is extensively used a food supplement and an over-the-counter drug for its beneficial effects. New studies have investigated OLE concerning the role of oxidative stress in the pathogenesis of vascular disease. This in vitro study aims to evaluate if OLE extracted from the Tuscan Olea europaea protects endothelial cells against oxidative stress generated by reactive oxygen species (ROS).

METHODS

OLE total polyphenols (TPs) were characterized by the Folin-Ciocalteu method. Endothelial cells were grown in conventional cultures (i.e., two-dimensional, 2D) and on a biomaterial scaffold (i.e., three-dimensional, 3D) fabricated via electrospinning. Cell viability and ROS measurement after H₂O₂ insults were performed.

RESULTS

OLE TP content was 23.29 mg GAE/g, and oleuropein was the principal compound. The dose-dependent viability curve highlighted the absence of significant cytotoxic effects at OLE concentrations below 250 µg/mL TPs. By using OLE preconditioning at 100 µg/mL, cell viability decrease was observed, being in 3D lower than in the 2D model. OLE was protective against ROS in both models.

CONCLUSIONS

OLE represents a high-value antioxidant source obtained by biowaste that is interesting for biomedical products. Using a 3D scaffold could be the best predictive model to mimic the physiological conditions of vascular tissue reaction.