Reduced Platelet Adhesion for Blended Electrospun Meshes with Low Amounts of Collagen Type I.

A clinically approved, tissue engineered graft is needed as an alternative for small-diameter artery replacement. Collagen type I is commonly investigated for naturally derived grafts. However, collagen promotes thrombosis, currently requiring a graft pre-seeding step. This study investigates unique impacts of blending low collagen amounts with synthetic polymers on scaffold platelet response, which would allow for viable acellular grafts that can endothelialize in vivo. While platelet adhesion and activation are confirmed to be high with 50% collagen samples, low collagen ratios surprisingly exhibit the opposite, anti-thrombogenic effect. Different platelet interactions in these blended materials can be related to collagen structure. Low collagen ratios show homogenous distribution of the components within individual fibers. Importantly, blended collagen scaffolds exhibit significant differences from gelatin scaffolds, including retaining percentage of collagen after incubation. These findings correlate with functional benefits including better endothelial cell spreading on collagen versus gelatin blended materials. This appears to differ from the current paradigm that processing with harsh solvents will irreversibly denature collagen into less desirable gelatin, but an important distinction is the interaction between collagen and synthetic materials during processing. Overall, excellent anti-thrombogenic properties of low collagen blends and benefits after grafting show promise for this vascular graft strategy.

Regenerative engineering: a review of recent advances and future directions.

Regenerative engineering is defined as the convergence of the disciplines of advanced material science, stem cell science, physics, developmental biology and clinical translation for the regeneration of complex tissues and organ systems. It is an expansion of tissue engineering, which was first developed as a method of repair and restoration of human tissue. In the past three decades, advances in regenerative engineering have made it possible to treat a variety of clinical challenges by utilizing cutting-edge technology currently available to harness the body's healing and regenerative abilities. The emergence of new information in developmental biology, stem cell science, advanced material science and nanotechnology have provided promising concepts and approaches to regenerate complex tissues and structures.

The Role of Nanomaterials and Biological Agents on Rotator Cuff Regeneration.

The rotator cuff is a musculotendon unit responsible for movement in the shoulder. Rotator cuff tears represent a significant number of musculoskeletal injuries in the adult population. In addition, there is a high incidence of retear rates due to various complications within the complex anatomical structure and the lack of proper healing. Current clinical strategies for rotator cuff augmentation include surgical intervention with autograft tissue grafts and beneficial impacts have been shown, but challenges still exist because of limited supply. For decades, nanomaterials have been engineered for the repair of various tissue and organ systems. This review article provides a thorough summary of the role nanomaterials, stem cells and biological agents have played in rotator cuff repair to date and offers input on next generation approaches for regenerating this tissue.

Poly(butyl cyanoacrylate) nanoparticle containing an organic photoCORM.

Carbon monoxide (CO) is a gasotransmitter, which has shown therapeutic effects in recent studies. Photo carbon monoxide releasing molecules (PhotoCORMs) allow the delivery of CO to be controlled by light. In this work, a new organic photoCORM DK4 is studied. DK4 is a diketone type photoCORM, which releases two CO molecules under visible light and simultaneously generates a fluorescent anthracene derivative. However, this type of CORM suffers from a deactivating hydration reaction and often needs to be incorporated in polymers or micelles. The two highly hydrophobic tert-butyl groups of DK4 protect it from the hydration reaction. DK4 functions in 1% DMSO aqueous solution, in which other DKs are deactivated. DK4 was incorporated in a poly(butyl cyanoacrylate) (PBCA) nanoparticle. PBCA has been used as a tissue adhesive and has been extensively studied for delivery of drugs to the brain. The PBCA/DK4 nanoparticle showed good photoactivity and low cytotoxicity, and thus is a promising material for studying the biomedical effects of CO.

Delivery of Antioxidant and Anti-inflammatory Agents for Tissue Engineered Vascular Grafts.

The treatment of patients with severe coronary and peripheral artery disease represents a significant clinical need, especially for those patients that require a bypass graft and do not have viable veins for autologous grafting. Tissue engineering is being investigated to generate an alternative graft. While tissue engineering requires surgical intervention, the release of pharmacological agents is also an important part of many tissue engineering strategies. Delivery of these agents offers the potential to overcome the major concerns for graft patency and viability. These concerns are related to an extended inflammatory response and its impact on vascular cells such as endothelial cells. This review discusses the drugs that have been released from vascular tissue engineering scaffolds and some of the non-traditional ways that the drugs are presented to the cells. The impact of antioxidant compounds and gasotransmitters, such as nitric oxide and carbon monoxide, are discussed in detail. The application of tissue engineering and drug delivery principles to biodegradable stents is also briefly discussed. Overall, there are scaffold-based drug delivery techniques that have shown promise for vascular tissue engineering, but much of this work is in the early stages and there are still opportunities to incorporate additional drugs to modulate the inflammatory process.