Superhydrophobic Polymer Composite Surfaces Developed via Photopolymerization.

Fabrication of superhydrophobic materials using incumbent techniques involves several processing steps and is therefore either quite complex, not scalable, or often both. Here, the development of superhydrophobic surface-patterned polymer-TiO2 composite materials using a simple, single-step photopolymerization-based approach is reported. The synergistic combination of concurrent, periodic bump-like pattern formation created using irradiation through a photomask and photopolymerization-induced nanoparticle (NP) phase separation enables the development of surface textures with dual-scale roughness (micrometer-sized bumps and NPs) that demonstrate high water contact angles, low roll-off angles, and desirable postprocessability such as flexibility, peel-and-stick capability, and self-cleaning capability. The effect of nanoparticle concentration on surface porosity and consequently nonwetting properties is discussed. Large-area fabrication over an area of 20 cm2, which is important for practical applications, is also demonstrated. This work demonstrates the capability of polymerizable systems to aid in the organization of functional polymer-nanoparticle surface structures.

In vitro evaluation of decellularized ECM-derived surgical scaffold biomaterials.

Decellularized extracellular matrix (ECM) biomaterials are increasingly used in regenerative medicine for abdominal tissue repair. Emerging ECM biomaterials with greater compliance target surgical procedures like breast and craniofacial reconstruction to enhance aesthetic outcome. Clinical studies report improved outcomes with newly designed ECM scaffolds, but their comparative biological characteristics have received less attention. In this study, we investigated scaffolds derived from dermis (AlloDerm Regenerative Tissue Matrix), small intestinal submucosa (Surgisis 4-layer Tissue Graft and OASIS Wound Matrix), and mesothelium (Meso BioMatrix Surgical Mesh and Veritas Collagen Matrix) and evaluated biological properties that modulate cellular responses and recruitment. An assay panel was utilized to assess the ECM scaffold effects upon cells. Results of the material-conditioned media study demonstrated Meso BioMatrix and OASIS best supported cell proliferation. Meso BioMatrix promoted the greatest migration and chemotaxis signaling, followed by Veritas and OASIS; OASIS had superior suppression of cell apoptosis. The direct adhesion assay indicated that AlloDerm, Meso BioMatrix, Surgisis, and Veritas had sidedness that affected cell-material interactions. In the chick chorioallantoic membrane assay, Meso BioMatrix and OASIS best supported cell infiltration. Among tested materials, Meso BioMatrix and OASIS demonstrated characteristics that facilitate scaffold incorporation, making them promising choices for many clinical applications. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 585-593, 2017.

A bilayer small diameter in vitro vascular model for evaluation of drug induced vascular injury.

In pre-clinical safety studies, drug-induced vascular injury (DIVI) is defined as an adverse response to a drug characterized by degenerative and hyperplastic changes of endothelial cells and vascular smooth muscle cells. Inflammation may also be seen, along with extravasation of red blood cells into the smooth muscle layer (i.e., hemorrhage). Drugs that cause DIVI are often discontinued from development after considerable cost has occurred. An in vitro vascular model has been developed using endothelial and smooth muscle cells in co-culture across a porous membrane mimicking the internal elastic lamina. Arterial flow rates of perfusion media within the endothelial chamber of the model induce physiologic endothelial cell alignment. Pilot testing with a drug known to cause DIVI induced extravasation of red blood cells into the smooth muscle layer in all devices with no extravasation seen in control devices. This engineered vascular model offers the potential to evaluate candidate drugs for DIVI early in the discovery process. The physiologic flow within the co-culture model also makes it candidate for a wide variety of vascular biology investigations.

Synthesis and characterization of a zwitterionic hydrogel blend with low coefficient of friction.

Hydrogels display a great deal of potential for a wide variety of biomedical applications. Often times the performance of these biomimetic materials is limited due to inferior friction and wear properties. This manuscript presents a method inspired by the tribological phenomena observed in nature for enhancing the lubricious properties of poly(vinyl alcohol) (PVA) hydrogels. This was achieved by blending PVA with various amounts of zwitterionic polymer, poly([2-(methacryloyloxy) ethyl] dimethyl-(3-sulfopropyl) ammonium hydroxide) (pMEDSAH). Our results indicate that pMEDSAH acts as an effective boundary lubricant, allowing for reduction in coefficient of friction by more than 80%. This reduction in friction coefficient was achieved while maintaining comparable mechanical and physical properties to that of the neat material. Also, these zwitterionic blends were found to be cytocompatible. Analysis of the structure to property relationships within this system indicate that the zwitterionic polymer served as a boundary lubricant and promoted a reduction in friction through hydration lubrication. This novel approach provides a promising platform for further investigations enhancing the tribological properties of hydrogels for biomedical applications. STATEMENT OF SIGNIFICANCE: The novelty of this work stems from showing that zwitterionic polymers can be used as an extremely effective hydrogel boundary lubricant. This work will have significant scientific impact because to date, design of hydrogels has emphasized replication of mechanical properties, but in order for these types of materials to be fully utilized as biomaterials it is imperative that they possess improved tribological and lubrication properties, because ignoring the surface and boundary lubrication mechanism, make these potential load-bearing substitutes incompatible with other natural articulating surfaces, leading the constructs to wear, fail, and damage healthy tissue. Our work also provides unique insight to the structure-property-function relationships of these biomaterials which will be of great interest to the readership of the journal.

Decellularized extracellular matrix microparticles as a vehicle for cellular delivery in a model of anastomosis healing.

Extracellular matrix (ECM) materials from animal and human sources have become important materials for soft tissue repair. Microparticles of ECM materials have increased surface area and exposed binding sites compared to sheet materials. Decellularized porcine peritoneum was mechanically dissociated into 200 µm microparticles, seeded with fibroblasts and cultured in a low gravity rotating bioreactor. The cells avidly attached and maintained excellent viability on the microparticles. When the seeded microparticles were placed in a collagen gel, the cells quickly migrated off the microparticles and through the gel. Cells from seeded microparticles migrated to and across an in vitro anastomosis model, increasing the tensile strength of the model. Cell seeded microparticles of ECM material have potential for paracrine and cellular delivery therapies when delivered in a gel carrier. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 1728-1735, 2016.

Biologic properties of surgical scaffold materials derived from dermal ECM.

Surgical scaffold materials manufactured from donor human or animal tissue are increasingly being used to promote soft tissue repair and regeneration. The clinical product consists of the residual extracellular matrix remaining after a rigorous decellularization process. Optimally, the material provides both structural support during the repair period and cell guidance cues for effective incorporation into the regenerating tissue. Surgical scaffold materials are available from several companies and are unique products manufactured by proprietary methodology. A significant need exists for a more thorough understanding of scaffold properties that impact the early steps of host cell recruitment and infiltration. In this study, a panel of in vitro assays was used to make direct comparisons of several similar, commercially-available materials: Alloderm, Medeor Matrix, Permacol, and Strattice. Differences in the materials were detected for both cell signaling and scaffold architecture-dependent cell invasion. Material-conditioned media studies found Medeor Matrix to have the greatest positive effect upon cell proliferation and induction of migration. Strattice provided the greatest chemotaxis signaling and best suppressed apoptotic induction. Among assays measuring structure-dependent properties, Medeor Matrix was superior for cell attachment, followed by Permacol. Only Alloderm and Medeor Matrix supported chemotaxis-driven cell invasion beyond the most superficial zone. Medeor Matrix was the only material in the chorioallantoic membrane assay to support substantial cell invasion. These results indicate that both biologic and structural properties need to be carefully assessed in the considerable ongoing efforts to develop new uses and products in this important class of biomaterials.

The role of fibroblasts in self-assembled skeletal muscle.

Small facial skeletal muscles often have no autologous donor source to effect surgical reconstruction. Autologously derived muscles could be engineered for replacement tissue, but must be vascularized and innervated to be functional. As a critical step, engineered muscle must mimic the morphology, protein and gene expression, and function of native muscle. This study utilized a self-assembly process to engineer three-dimensional (3D) muscle from a statically strained muscle cell monolayer. Primary mouse myoblasts (PMMs) and mouse embryonic fibroblasts (MEFs) were separately proliferated and coseeded on a fibrin sheet with anchored sutures. Within 10 days of initiating PMM differentiation, the cell-gel layer contracted, lifted, and rolled into a cylindrical 3D structure around the tendon-like suture anchors; the myotubes longitudinally aligned along the lines of tensile force. The objectives of this study were to characterize these engineered muscles and to elucidate the role of the fibroblasts in the self-assembly process. Fibroblasts maintained myotube viability, mediated fibrin degradation, and assisted in muscle self-assembly. The optimal 1:1 PMM:MEF ratio resulted in tissue morphology remarkably similar to native muscle. Through gene and protein expression assays, the development and maturation of the engineered muscle tissue was demonstrated to recapitulate normal skeletal muscle development.

Expression of vascular endothelial growth factor isoforms in the Japanese quail embryo.

Vascular endothelial growth factor (VEGF) i s required for vascular development. In the quail, four VEGF isoforms formed by alternative splicing, are translated into proteins with 122, 146, 166, and 190 amino acids. VEGF isoforms differ biochemically, with variable affinities for heparan sulfate proteoglycans, the extracellular matrix and VEGF receptors. There are few data on the functional significance of VEGF isoforms. RT-PCR was used to examine isoform expression during quail vascular development. Our results suggest that all quail isoforms are expressed during establishment of the vascular pattern in whole embryos and extraembryonic tissues at apparently equal levels. No isoform-specific expression patterns were detected in isolated endoderm or between embryo halves.

Vascular endothelial growth factor: a regulator of vascular morphogenesis in the Japanese quail embryo.

Experiments in mouse embryos indicate that a critical level of VEGF is required for normal vascular development, as mice lacking a single VEGF allele die at midgestation. Thus VEGF concentration may be a determinant of the size and location of major blood vessels during formation of the primary capillary plexus. Ectopic VEGF delivery was used to examine the effect of VEGF concentration on early vascular patterning in the quail embryo. VEGF was delivered by implanting VEGF-soaked heparin chromatography beads at three rostral-caudal locations in embryos with six somite pairs, which allowed us to study the effect of VEGF on different cellular activities. Ectopic VEGF resulted in significant changes in the vascular pattern at three rostral-caudal levels. Quantitation demonstrated an increased vascularity in the area of the implanted VEGF bead compared to the vascular pattern of embryos with control beads. Areas lateral to the dorsal aortae that are normally avascular became vascularized, and there was an apparent fusion between the dorsal aorta and lateral capillary plexus.