Osteo-mucosal engineered construct: In situ adhesion of hard-soft tissues

Optimization of dental adhesive interfaces using tissue biomodulation with DESIGNER biopolymers

OBJECTIVE

To investigate the modulatory effects of four proanthocyanidin-DESIGNERS (PAC-DESIGNERs) on the long-term bond strength of the resin-adhesive interface, the degree of conversion of resin monomers, the chemical-mechanical properties of dentin matrix, and cell biocompatibility.

METHODS

Standardized formulations of PACs with a dominant degree of polymerization - DP (trimers: PM-AB and CV-AB; tetramers: PM-ABA and CV-ABB) were prepared from two sources of AB-Type PACs using a DESIGNER approach. Resin-dentin interface was assessed after 24 hours and 1 year using a microtensile bond strength (µTBS) test. The degree of conversion (DC) of resin monomers and chemical analysis of the dentin matrix were analyzed by ATR-FTIR spectroscopy. The viscoelastic properties of the dentin matrix were assessed by dynamic mechanical analysis (DMA). Cell viability was analyzed using a 3D cell culture model. Data analysis using two- and one-way ANOVA and post-hoc tests (α = 0.05).

RESULTS

All PAC-DESIGNER biomodulation increased the µTBS when compared to control (p < 0.05), regardless of source, DP, and aging. The DC of resin adhesive was not negatively impacted, and an increase in DC was observed with the incorporation of PM-AB and PM-ABA DESIGNERs (p < 0.05). PAC-DESIGNER treatment also increased the dentin matrix complex modulus (153-79 MPa) and storage modulus (151-78 MPa) when compared to control (∼9 MPa, p < 0.05). All DESIGNERs decreased the intensity of amide II/CH2 ratio; a decrease in the amide III/CH2 ratio was observed for CV-ABB (p < 0.05). Moreover, PAC-DESIGNERs exhibited good cell biocompatibility and healthy cell morphology.

SIGNIFICANCE

All PAC-DESIGNERs optimized the dentin-resin µTBS. The different molecular structures played a modulatory role in the chemical-mechanical properties of the dentin matrix, the degree of conversion of adhesive, and cell biocompatibility.

Tyrosinases: a family of copper-containing metalloenzymes

Tyrosinases (TYRs) are a family of copper-containing metalloenzymes that are present in all domains of life. TYRs catalyze the reactions that start the biosynthesis of melanin, the main pigment of the animal kingdom, and are also involved in the formation of the bright colors seen on the caps of mushrooms and in the petals of flowers. TYRs catalyze the ortho-hydroxylation and oxidation of phenols and the oxidation of catechols to the respective o-quinones. They only need molecular oxygen to do that, and the products of TYRs-o-quinones-are highly reactive and will usually react with the next available nucleophile. This reactivity can be harnessed for pharmaceutical applications as well as in environmental and food biotechnology. The majority of both basic and applied research on TYRs utilizes "mushroom tyrosinase", a crude enzyme preparation derived from button mushroom (Agaricus bisporus) fruiting bodies. Access to pure TYR preparations comes almost exclusively from the production of recombinant TYRs as the purification of these enzymes from the natural source is usually very laborious and plagued by low yields. In this text an introduction into the biochemistry of the enzyme TYR will be given, followed by an overview of available structural data of TYRs, the current model for the catalytic mechanism, a survey of reports on the recombinant production of this important metalloenzyme family, and a review of the applications of TYRs for the synthesis of catechols, as biosensors, in bioremediation, for the cross-linking of proteins and medical hydrogels as well as for melanoma treatment.

Graphical Abstract

Fabricating Multiphasic Angiogenic Scaffolds Using Amyloid/Roxadustat-Assisted High-Temperature Protein Printing

Repairing multiphasic defects is cumbersome. This study presents new soft and hard scaffold designs aimed at facilitating the regeneration of multiphasic defects by enhancing angiogenesis and improving cell attachment. Here, the nonimmunogenic, nontoxic, and cost-effective human serum albumin (HSA) fibril (HSA-F) was used to fabricate thermostable (up to 90 °C) and hard printable polymers. Additionally, using a 10.0 mg/mL HSA-F, an innovative hydrogel was synthesized in a mixture with 2.0% chitosan-conjugated arginine, which can gel in a cell-friendly and pH physiological environment (pH 7.4). The presence of HSA-F in both hard and soft scaffolds led to an increase in significant attachment of the scaffolds to the human periodontal ligament fibroblast (PDLF), human umbilical vein endothelial cell (HUVEC), and human osteoblast. Further studies showed that migration (up to 157%), proliferation (up to 400%), and metabolism (up to 210%) of these cells have also improved in the direction of tissue repair. By examining different in vitro and ex ovo experiments, we observed that the final multiphasic scaffold can increase blood vessel density in the process of per-vascularization as well as angiogenesis. By providing a coculture environment including PDLF and HUVEC, important cross-talk between these two cells prevails in the presence of roxadustat drug, a proangiogenic in this study. In vitro and ex ovo results demonstrated significant enhancements in the angiogenic response and cell attachment, indicating the effectiveness of the proposed design. This approach holds promise for the regeneration of complex tissue defects by providing a conducive environment for vascularization and cellular integration, thus promoting tissue healing.

Development of fibroblast/endothelial cell-seeded collagen scaffolds for in vitro prevascularization

The development of vascularized scaffolds remains one of the major challenges in tissue engineering, and co-culturing with endothelial cells is known as one of the possible approaches for this purpose. In this approach, optimization of cell culture conditions, scaffolds, and fabrication techniques is needed to develop tissue equivalents that will enable in vitro formation of a capillary network. Prevascularized equivalents will be more physiologically comparable to the native tissues and potentially prevent insufficient vascularization after implantation. This study aimed to culture human umbilical vein endothelial cells (HUVECs), alone or in co-culture with fibroblasts, on collagen scaffolds prepared by simple fabrication approaches for in vitro prevascularization. Different concentrations and ratios of HUVECs and fibroblasts seeded on collagen gel and sponge scaffolds under several culture conditions were examined. Cell viability, scaffolds morphology, and structure were analyzed. Collagen gel scaffolds showed good cell proliferation and viability, with higher proliferation rates for cells cultured in a 2:1 (fibroblasts: HUVECs) ratio and kept in endothelial cell growth medium. However, these matrices were unable to support endothelial cell sprouting. Collagen sponges were highly porous and showed good cell viability. However, they became fragile over time in culture, and they still lack signs of vascularization. Collagen scaffolds were a good platform for cell growth and viability. However, under the experimental conditions of this study, the HUVEC/fibroblast-seeded scaffolds were not suitable platforms to generate in vitro prevascularized equivalents. Our findings will be a valuable starting point to optimize culture microenvironments and scaffolds during fabrication of prevascularized scaffolds.

Enzyme-Triggered Crosslinked Hybrid Hydrogels for Bone Tissue Engineering

The quest to develop state-of-the-art hydrogels for bone tissue engineering has accompanied substantial innovation and significant progression in the field of bioactive hydrogels. Still, there is scope for advancement in this cell-friendly and biocompatible scaffold system. The crosslinking approaches used for hydrogel synthesis plays a decisive role in guiding and regulating the mechanical stability, network framework, macroscopic architect, immunological behaviors, and cellular responses. Until recently, enzyme-based crosslinking strategies were considered as the pinnacle in designing efficient hybrid hydrogel systems. A variety of enzymes have been explored for manufacturing hydrogels while taking the advantage of the biocompatible nature, specificity, ability to produce nontoxic by products and high efficiency of enzymes. The current review focuses on the utility of different enzymes as crosslinking agents for hydrogel formation with their application in bone tissue engineering. The field of enzyme crosslinked hydrogel synthesis is rapidly maturing with a lot of opportunities to be explored in bone tissue engineering. Enzyme-based in situ and externally crosslinked hydrogels for bone regeneration is an attractive field, and with innovation in using engineered enzymes this field will continue to flourish with clinical orientation.

Coating of 3D printed PCL/TCP scaffolds using homogenized-fibrillated collagen

BACKGROUND

Poly(3-caprolactone) (PCL)/β-tricalcium phosphate (β-TCP) composite scaffolds fabricated by three-dimensional (3D) printing are one of the common scaffolds for bone tissue regeneration. However, the main challenge of these 3D printed PCL/β-TCP scaffolds is the fact that many cells pass from porosities during in vitro cell seeding, leading to poor initial cell attachment. This study aimed to demonstrate the fabrication of a new collagen coating process for optimizing the hydrophilic property and cell-substrate interactions. This method may be used for coating collagen on any relevant biomedical constructs made of synthetic polymers to increase their biocompatibility and cell attachment.

MATERIALS AND METHODS

Porous composite scaffolds fabricated by 3D printing were coated with collagen by a novel method and compared to traditional methods. After plasma treatment, samples were inverted in a homogenized collagen solution, freeze-dried, stabilized by crosslinking, freeze-dried again, and fibrillated using a defined salt concentration. Samples were characterized by a 3D laser microscope, cytocompatibility assay, attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy, water absorption, protein absorption, and bioactivity assay.

RESULTS

Homogenized collagen at pH= 7 resulted in a very uniform layer on the surface of scaffolds with significantly higher cell proliferation (p < 0.05). Collagen-coated scaffolds showed significantly higher water absorption, protein absorption, and bioactivity compared to non-coated samples (p < 0.05).

CONCLUSION

The results demonstrate that both the pH and collagen structure influence the coating of scaffolds, while the concentrations used in this study do not have a significant difference in this aspect. The combination of homogenization and fibrillization makes scaffolds more biocompatible and desirable for bone tissue engineering.