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—Vascularization remains a critical requirement for the long term survival of engineered tissue constructs, especially thick ones. Such thick constructs for cardiac tissue engineering has been reported by our group and others based on... more
—Vascularization remains a critical requirement for the long term survival of engineered tissue constructs, especially thick ones. Such thick constructs for cardiac tissue engineering has been reported by our group and others based on decellularized porcine cardiac extracellular matrix (pcECM) that has been shown to resemble the native tissue both structurally and chemically. The network of inherent vasculature, which was largely retained within our pcECM, can be used as primers for re-endothelialization and neo-vascularization with regenerative cells. Endothelial cells alone, seeded onto the ECM, not only attached and survived but also rearranged into typical confluent monolayer with self-alignment. Sequential co-cultures of human umbilical vein endothelial cells (HUVEC) and mesenchymal stem cells (MSC) were shown to support the growth of both lineages on the surface and in the vasculature of reseeded pcECM. After ECM treatment with gelatin or fibronectin, cell proliferation increased significantly for both MSCs and HUVECs. Preliminary results showed that future efforts combining co-culture, treated scaffolds and dynamic culture environment may result in re-endothelialization leading to functional blood vessels in thick engineered tissue for partial cardiac replacement therapy.
The same base resin, a HDPE with vinyl–silane units grafted along the backbone, was subjected to three different types of crosslinking: (a) using peroxides and heat, (b) using a catalyst under high humidity, and (c) using high-energy... more
The same base resin, a HDPE with vinyl–silane units grafted along the backbone, was subjected to three different types of crosslinking: (a) using peroxides and heat, (b) using a catalyst under high humidity, and (c) using high-energy radiation. Macroscopic properties, such as tensile behavior-at-break, shear modulus, gel content, and crystallinity were measured for all three types of crosslinked material. Although the mechanical and rheological properties appear to indicate differences in distribution of crosslinks, the major differences are seen for the degree of crystallinity. These differences are rationalized on the basis of the mechanism of crosslinking and the resultant location of crosslink sites.
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Research Interests:
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PLLA, PDLLA, and PLGA copolymers have been studied to understand the details of their degradation behavior. All polymers exhibited a homogeneous mode of degradation, with uniform rates of degradation throughout the film. Crystallinity... more
PLLA, PDLLA, and PLGA copolymers have been studied to understand the details of their degradation behavior. All polymers exhibited a homogeneous mode of degradation, with uniform rates of degradation throughout the film. Crystallinity inhibited water absorption and hence retarded degradation. The degradation rate was increased by the presence of glycolic acid units in the PLGA copolymer; this effect overwhelms any decrease in degradation rate because of increased crystallinity due to the additional GA units. This effect is demonstrated quantitatively in this study. In PLGA polymers, there is evidence of unusual recrystallization behavior as degradation proceeds, due mainly to the higher rate of hydrolytic scission of the glycolide linkage compared with the lactide, as verified quantitatively with the use of 1H NMR studies. Application of a Monte Carlo model to the degradation results, however, appears to show a random scission process. The details of the mechanistic study of different factors influencing the process of degradation, as reported here, may have important implications in terms of selecting the right material for specific biomedical applications. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3111–3117, 2006
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This review details the use of polymeric biomaterials used in implantable cardiovascular devices. Specifically, the role of the polymer in two major types of device, the vascular graft and the cardiovascular stent, is examined critically.... more
This review details the use of polymeric biomaterials used in implantable cardiovascular devices. Specifically, the role of the polymer in two major types of device, the vascular graft and the cardiovascular stent, is examined critically. In these two devices, the device ...
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Research Interests: Water, Biomaterials, Kinetics, Scanning Electron Microscopy, Polymers, and 14 moreMultidisciplinary, Diffusion, Weight Loss, Absorption, Structural Change, Water Absorption, Phosphates, Materials Testing, Biocompatible Materials, Drug Carriers, Lactic Acid, Drug Release, Transition Temperature, and Phosphate Buffer Saline
The use of pressure-sensitive adhesives (PSAs) for skin-contact applications is discussed. The requirements of such adhesives in various applications are examined in detail. Commercially available classes of PSAs used for skin-contact... more
The use of pressure-sensitive adhesives (PSAs) for skin-contact applications is discussed. The requirements of such adhesives in various applications are examined in detail. Commercially available classes of PSAs used for skin-contact applications are the acrylics, the polyisobutylenes, and the silicones. The main application examined in this review is transdermal drug delivery. The roles played by the PSA in two types of transdermal designs are described. Correlations between in vivo and ex vivo measurements of adhesion are discussed. Also, the reported human studies of various commercially available transdermals are examined critically, with a view to assessing the relative performance capabilities of each type of transdermal design. Finally, a comprehensive listing of currently commercialized transdermals is given.
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Research Interests:
Poly(lactide-co-glycolide) (PLGA 75 : 25), IV 0.94 dL/g was chosen as the matrix of the microparticles. Bovine serum albumin (BSA) (Fraction V) as the model drug was incorporated in the microparticles by a W/O/W emulsification and solvent... more
Poly(lactide-co-glycolide) (PLGA 75 : 25), IV 0.94 dL/g was chosen as the matrix of the microparticles. Bovine serum albumin (BSA) (Fraction V) as the model drug was incorporated in the microparticles by a W/O/W emulsification and solvent evaporation technique. The effect of the various preparation parameters on particle morphology, drug loading efficiency, and drug release profiles of the resultant microparticles were examined. Particle size varied from 5 to 60 μm. The final morphology of the microparticles varied dramatically with preparation variables such as equipment used to produce the primary emulsion (W1/O) and the water-to-oil ratio (W1/O) in the primary emulsion. In general, the viscosity of the primary emulsion had a significant effect on the porosity of particles produced. The release of BSA showed a strong relationship with the preparation parameters of microparticles, partly due to the morphological effects. For example, microparticles made from the vortex mixer that was used to disperse inner aqueous phase (W1) to oil phase (O) showed a lower burst effect than that made from the homogenizer because of its better surface morphology. W1/O ratio, speed of dispersing the primary emulsion into W2, PLGA concentration, and different matrix materials also affected the drug release profiles. In all the samples studied here, only diffusion-controlled release was observed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3053–3061, 2006