Keratin, a naturally-derived polymer derived from human hair, is physiologically biodegradable, provides adequate cell support, and can self-assemble or be crosslinked to form hydrogels. Nevertheless, it has had limited use in tissue engineering and has been mainly used as casted scaffolds for drug or growth factor delivery applications. Here, we present and assess a novel method for the printed, sequential production of 3D keratin scaffolds. Using a riboflavin-SPS-hydroquinone (initiator-catalyst-inhibitor) photosensitive solution we produced 3D keratin constructs via UV crosslinking in a lithography-based 3D printer. The hydrogels obtained have adequate printing resolution and result in compressive and dynamic mechanical properties, uptake and swelling capacities, cytotoxicity, and microstructural characteristics that are comparable or superior to those of casted keratin scaffolds previously reported. The novel keratin-based printing resin and printing methodology presented have the potential to impact future research by providing an avenue to rapidly and reproducibly manufacture patient-specific hydrogels for tissue engineering and regenerative medicine applications.

The objective of this work was to investigate the effects of macroporous hydrogel architecture on the osteogenic signal expression and differentiation of human mesenchymal stem cells (hMSCs). In particular, we have proposed a tissue engineering approach for orbital bone repair based on a cyclic acetal biomaterial formed from 5-ethyl-5-(hydroxymethyl)-beta,beta-dimethyl-1,3-dioxane-2-ethanol diacrylate (EHD) and poly(ethylene glycol) diacrylate (PEGDA). The EHD monomer and PEGDA polymer may be fabricated into macroporous EH-PEG hydrogels by radical polymerization and subsequent porogen leaching, a novel technique for hydrophilic gels. We hypothesized that EH-PEG hydrogel macroporosity facilitates intercellular signaling among hMSCs. To investigate this phenomenon, hMSCs were loaded into EH-PEG hydrogels with varying pore size and porosity. The viability of hMSCs, the expression of bone morphogenetic protein-2 (BMP-2), BMP receptor type 1A, and BMP receptor type 2 by hMSCs, and the differentiation of hMSCs were then assessed. Results demonstrate that macroporous EH-PEG hydrogels support hMSCs and that this macroporous environment promotes a dramatic increase in BMP-2 expression by hMSCs. This upregulation of BMP-2 expression is associated by a more rapid hMSC differentiation, as measured by alkaline phosphatase expression. Altering hMSC interactions with the EH-PEG hydrogel surface, by the addition of fibronectin, did not appear to augment BMP-2 expression. We therefore speculate that EH-PEG hydrogel macroporosity facilitates autocrine and paracrine signaling by localizing endogenously expressed factors within the hydrogel's pores and thus promotes hMSC osteoblastic differentiation and bone regeneration.

Abstract. At an ever increasing pace, synthetic biomaterials are being developed with specific functionalities for tissue engineering applications. These biomaterials possess properties including biocompatibility, mechanical strength, and degradation as well as functionalities such as specific cell adhesion and directed cell migration. However, synthetic polymers are often not completely biologically inert and may non-specifically react with the surrounding in vivo environment. An example of this reactivity is the release of acidic degradation products from hydrolytically degradable polymers based upon an ester moiety. In order to address this concern, a novel class of biomaterials based upon a cyclic acetal unit has been developed. Scaffolds suitable for the replacement of both hard and soft tissues have been successfully fabricated from cyclic acetals and a detailed characterization of scaffold properties has been performed. Cyclic acetal based biomaterials have also been used to repair bone defects and promote bone growth, displaying a minimal inflammatory response. This review will discuss the most recent research of current biomaterials and cyclic acetals, and particularly focus on the tissue engineering applications of these materials. Finally, this review will also briefly discuss polyacetals and polyketals for drug delivery applications.

No abstract

Abdominal wall hernias resulting from prior incisions are a common surgical complication affecting hundreds of thousands of Americans each year. The negative consequences associated with abdominal hernias may be considerable, including pain, bowel incarceration, vascular disruption, organ loss, and death. Current clinical approaches for the treatment of abdominal wall hernias focus on the implantation of permanent biomaterial meshes or acellular xenografts. However, these approaches are not infrequently associated with postoperative infections, chronic sinuses, or small bowel obstruction. Furthermore, the most critical complication, hernia recurrence, has been well described and may occur in a large percentage of patients. Despite many advances in repair techniques, wound healing and skeletal muscle regeneration is limited in many cases, resulting in a decrease in abdominal wall tissue function and contributing to the high hernia recurrence rate. This review will give an overview of skeletal muscle anatomy, skeletal muscle regeneration, and herniation mechanisms, as well as discuss the current and future clinical solutions for abdominal wall hernia repair.