Evaluation of a hybrid small caliber vascular graft in a rabbit model

The application of small intestinal submucosa in tissue regeneration

The distinctive three-dimensional architecture, biological functionality, minimal immunogenicity, and inherent biodegradability of small intestinal submucosa extracellular matrix materials have attracted considerable interest and found wide-ranging applications in the domain of tissue regeneration engineering. This article presents a comprehensive examination of the structure and role of small intestinal submucosa, delving into diverse preparation techniques and classifications. Additionally, it proposes approaches for evaluating and modifying SIS scaffolds. Moreover, the advancements of SIS in the regeneration of skin, bone, heart valves, blood vessels, bladder, uterus, and urethra are thoroughly explored, accompanied by their respective future prospects. Consequently, this review enhances our understanding of the applications of SIS in tissue and organ repair and keeps researchers up-to-date with the latest research advancements in this area.

Structural design and mechanical performance of composite vascular grafts

This study reviews the state of the art in structural design and the corresponding mechanical behaviours of composite vascular grafts. We critically analyse surface and matrix designs composed of layered, embedded, and hybrid structures along the radial and longitudinal directions; materials and manufacturing techniques, such as tissue engineering and the use of textiles or their combinations; and the corresponding mechanical behaviours of composite vascular grafts in terms of their physical–mechanical properties, especially their stress–strain relationships and elastic recovery. The role of computational studies is discussed with respect to optimizing the geometrics designs and the corresponding mechanical behaviours to satisfy specialized applications, such as those for the aorta and its subparts. Natural and synthetic endothelial materials yield improvements in the mechanical and biological compliance of composite graft surfaces with host arteries. Moreover, the diameter, wall thickness, stiffness, compliance, tensile strength, elasticity, and burst strength of the graft matrix are determined depending on the application and the patient. For composite vascular grafts, hybrid architectures are recommended featuring multiple layers, dimensions, and materials to achieve the desired optimal flexibility and function for complying with user-specific requirements. Rapidly emerging artificial intelligence and big data techniques for diagnostics and the three-dimensional (3D) manufacturing of vascular grafts will likely yield highly compliant, subject-specific, long-lasting, and economical vascular grafts in the near-future.

Graphic abstract

A Biohybrid Material With Extracellular Matrix Core and Polymeric Coating as a Cell Honing Cardiovascular Tissue Substitute

Objective

To investigate the feasibility of a hybrid material in which decellularized pericardial extracellular matrix is functionalized with polymeric nanofibers, for use as a cardiovascular tissue substitute.

Background

A cardiovascular tissue substitute, which is gradually resorbed and is replaced by host's native tissue, has several advantages. Especially in children and young adults, a resorbable material can be useful in accommodating growth, but also enable rapid endothelialization that is necessary to avoid thrombotic complications. In this study, we report a hybrid material, wherein decellularized pericardial matrix is functionalized with a layer of polymeric nanofibers, to achieve the mechanical strength for implantation in the cardiovascular system, but also have enhanced cell honing capacity.

Methods

Pericardial sacs were decellularized with sodium deoxycholate, and polycaprolactone-chitosan fibers were electrospun onto the matrix. Tissue-polymer interaction was evaluated using spectroscopic methods, and the mechanical properties of the individual components and the hybrid material were quantified. In-vitro blood flow loop studies were conducted to assess hemocompatibility and cell culture methods were used to assess biocompatibility.

Results

Encapsulation of the decellularized matrix with 70 μm thick matrix of polycaprolactone-chitosan nanofibers, was feasible and reproducible. Spectroscopy of the cross-section depicted new amide bond formation and C–O–C stretch at the interface. An average peel strength of 56.13 ± 11.87 mN/mm2 was measured, that is sufficient to withstand a high shear of 15 dynes/cm2 without delamination. Mechanical strength and extensibility ratio of the decellularized matrix alone were 18,000 ± 4,200 KPa and 0.18 ± 0.03% whereas that of the hybrid was higher at 20,000 ± 6,600 KPa and 0.35 ± 0.20%. Anisotropy index and stiffness of the biohybrid were increased as well. Neither thrombus formation, nor platelet adhesion or hemolysis was measured in the in-vitro blood flow loop studies. Cellular adhesion and survival were adequate in the material.

Conclusion

Encapsulating a decellularized matrix with a polymeric nanofiber coating, has favorable attributes for use as a cardiovascular tissue substitute.

Vascular transplantation with dual-biofunctional ePTFE vascular grafts in a porcine model

Cardiovascular disease (CVD) poses serious health concerns worldwide. The lack of transplantable vascular grafts is an unmet clinical need in the surgical treatment of CVD. Although expanded polytetrafluoroethylene (ePTFE) vascular grafts have been used in clinical practice, a low long-term patency rate in small-diameter transplantation application is still the biggest challenge. Thus, surface modification of ePTFE is sought after. In this study, polydopamine (PDA) was used to improve the hydrophilia and provide immobilization sites in ePTFE. Bivalirudin (BVLD), a direct thrombin inhibitor, was used to enhance the anti-thrombotic activity of ePTFE. The peptides derived from extracellular matrix proteins were used to elevate the bioactivity of ePTFE. The morphology, chemical composition, peptide modified strength, wettability, and hemocompatibility of modified ePTFE vascular grafts were investigated. Then, an endothelial cell proliferation assay was used to evaluate the best co-modification strategy of the ePTFE vascular graft in vitro. Since a large animal could relatively better mimic human physiology, we chose a porcine carotid artery replacement model in the current study. The results showed that the BVLD/REDV co-modified ePTFE vascular grafts had a satisfactory patency rate (66.7%) and a higher endothelial cell coverage ratio (70%) at 12 weeks after implantation. This may offer an opportunity to produce a multi-biofunctional ePTFE vascular graft, thereby yielding a potent product to meet the clinical needs.

Preparation and Characterization of Antibacterial Porcine Acellular Dermal Matrices with High Performance

Infection is a common complication in the process of wound management. An ideal wound dressing is supposed to reduce or even prevent the infection while promoting wound healing. A porcine acellular dermal matrix (pADM) has been already used as a wound dressing in clinic due to its capacity to accelerate wound healing. However, not only is pure pADM not antibacterial, its mechanical properties are poor. In this study, an antibacterial pADM with good performance was prepared by adding two natural products as modifiers, quercetin (QCT) and tea tree oil (TTO). The result of Fourier-transform infrared (FTIR) proved that the addition of modifiers did not break the natural triple-helical structure of collagen. Meanwhile, the results of differential scanning calorimetry (DSC), thermogravimetric analysis (TG), mechanic experiment, and enzymatic degradation demonstrated that pADM handled with QCT and TTO (termed QCT-TTO-pADM) had better thermal stability, mechanical strength, and resistance to enzymatic degradation than pADM. Meanwhile, QCT-TTO-pADM had excellent antibacterial activity and showed an antibacterial rate of over 80%. Furthermore, in the cytocompatibility analysis, QCT-TTO-pADM had no side effects on the adhesion, growth, and proliferation of fibroblasts. QCT-TTO-pADM could even accelerate wound healing more efficiently than pADM and glutaraldehyde-modified pADM (GA-pADM). In conclusion, QCT-TTO-pADM was a potential antibacterial wound dressing with good performance.

Surface modification of small intestine submucosa in tissue engineering

With the development of tissue engineering, the required biomaterials need to have the ability to promote cell adhesion and proliferation in vitro and in vivo. Especially, surface modification of the scaffold material has a great influence on biocompatibility and functionality of materials. The small intestine submucosa (SIS) is an extracellular matrix isolated from the submucosal layer of porcine jejunum, which has good tissue mechanical properties and regenerative activity, and is suitable for cell adhesion, proliferation and differentiation. In recent years, SIS is widely used in different areas of tissue reconstruction, such as blood vessels, bone, cartilage, bladder and ureter, etc. This paper discusses the main methods for surface modification of SIS to improve and optimize the performance of SIS bioscaffolds, including functional group bonding, protein adsorption, mineral coating, topography and formatting modification and drug combination. In addition, the reasonable combination of these methods also offers great improvement on SIS surface modification. This article makes a shallow review of the surface modification of SIS and its application in tissue engineering.