Tissue scaffolding

Improved characterization of the morphological/microstructural properties of porous solids, and the associated transport properties of fluids imbibed into these materials, is crucial to the development of new porous materials, such as ceramics. Of particular interest is the fabrication of so-called functionalized ceramics, which contain a pore structure tailored to a specific biomedical or industrial application (e.g., molecular filters, catalysts, gas storage cells, drug delivery devices, tissue scaffolds) [1-3]. Functionalization of ceramics can involve the use of graded or layered pore microstructure, morphology or chemical composition. 

Trenor SR, Shultz AR, Love BJ, Long TE. Coumarins in polymers from light harvesting to photo-cross-linkable tissue scaffolds. Chem Rev 2004 104 3059-3077. 

Artificial biologies, whelher soff or hard, can be categorized as eifher temporary (short term) or permanent (long term) in their intended application. Most, but certainly not all, polymers for biomedical applications are of the short-term type and include sutures, drug delivery devices, temporary vascular grafts and stents, tissue scaffolds. 

Bioengineering and biomimetics seek to develop tissue scaffolds similar to the natural ones, in terms of composition and biological behavior. Efforts are being made to develop products and processes that can substitute tissue that is biocompatible and allows biointegration. 

Potential applications of peptide-polymer conjugates include drug delivery materials, optoelectronics, biosensors, tissue scaffolds, tissue replacement materials, hydrogels, adhesives, biomimetic polymers, lithographic masks, and templates for metallic or silica nanostructures. 

Keywords tissue scaffolds, mercury porosimetry, capillary flow porometry, scanning electron microscopy, image analysis... 

A range of techniques are being assessed for their potential to characterize tissue scaffolds that include some of the methods used in this study.8... 

Figure 1. The highly porous, interconnected structure of a particulate leached PCL tissue scaffold.

Figure 2. The normalized particle size distribution of the salt grains used to produce tissue scaffolds can be obtained by light scattering (Malvern Mastersizer series 2600c).

Scaffold porosity and information on the pore size distribution can be obtained from intrusion techniques. The most commonly used methods are mercury porosimetry and capillary flow porometry. In mercury porosimetry the pressure required to fill a tissue scaffold with non-wetting mercury is monitored over a set period of time. Higher pressures are required to fill small pores than large pores a fact that can be exploited using the Washburn equation13 to extract structural information where D is the diameter of the pore at a particular differential... 

The porosity of a scaffold is an often quoted characteristic of tissue scaffolds, per se porosity is a measure of the void volume contained within a porous... 

Three methods have been used in this investigation to estimate the porosity of PCL tissue scaffolds, namely weight determination, mercury porosimetry and analysis of scanning electron micrographs. The results are shown in Figure 4. 

Various techniques, such as intrusion methods, image analysis and weight determinations are used to provide estimates of the porosity and the distribution of pore sizes within a tissue scaffold. This preliminary study of the structural features of particulate-leached PCL scaffolds has shown that reliable measures of porosity can be obtained from simple weighing measurements (Buoyancy method). 

The distribution of pore sizes can be obtained from both mercury porosimetry and capillary flow porometry. These distributions are only representations of the actual scaffold structure reflecting the limitations of the underlying physics behind each technique. For this reason it is very difficult to compare pore size distributions for complex structures, such as particulate-leached tissue scaffolds. 

The authors would like to thank Sam Gnaniah for determining the level of crystallinity within the polycaprolactone and Adam Calver for performing many of the density measurements. This work was funded by the United Kingdom Department of Trade and Industry as part of its programme of reseach on Materials for Processing and Performance (Project MPP 4.2 Physical Characterisation of Tissue Scaffolds). 

E. Sachlos and J. T. Czemuska, Making tissue scaffolds work. Review on the application of solid freeform fabrication technology to the production of tissue engineering scaffolds, Europ. Cells Mater. 5, 29-40 (2003). 

CNTs are especially valued as implant materials thanks to their novel mechanical properties and surface functionability.35 They have been found to make an ideal scaffold for the growth of bone tissue.36 Moreover, many tissues and organs require bio-compatible substrates to facilitate tissue growth and implantation. The fabric made fom CNTs serves as an efficient tissue scaffold.36 Several publications demonstrate that CNTs can be used as a substrate for neuronal growth, and that modifications of the CNTs can be employed to modulate the development of neurons. This suggests that it may be possible to employ suitably functionalized CNTs as neural prostheses in neurite regeneration.35 Lipid bilayers have been developed using a nanotube template. 

Bioabsorbable tissue scaffold 4,512.038 1985 Alexander, Parsons, Strauchler. and Weiss ... 

Coumarins in polymers from light harvesting to photo-cross-linkable tissue scaffolds 04CRV3059. 

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