Conventional characterization of porous biological materials, while valuable, comes with certain limitations. Common methods include mercury intrusion, which requires drying a sample which will be wet during its use, and risks collapsing the pore structure if the material is not strong enough. NMR overcomes the dry sample problem, but significant analysis is required in order to translate resonance data into porosity. In addition, neither of these gives an image, or provides information about gradients of pore size or interconnectivity within the sample. In microscopic methods, like SEM, cross-sections of materials may be taken so as to visualize the topography; however, this information is generally qualitative. In this work we have used X-ray tomography to replace these methods and to characterize a material for which some information would be lost otherwise.

This is a novel application of X-Ray tomography. We are using it to characterize a highly-porous biological material, or whey protein isolate sol-gel intended for use as a degradable scaffold for bone regeneration. The pore size distribution and profile are key aspects of the scaffold, as a certain threshold pore diameter allows sufficient diffusion of nutrients to the in-grown cells, as well as proper initial seeding of the implant with preosteoblastic cells.

In this technique, a series of x-ray projections are obtained for different projections of the object. The data are computer-reconstructed into slices, which can be assembled into a three-dimensional image. The final data set allows the material to be viewed from different angles for qualitative analysis. It also allows for quantitative characterization of the pore size distribution, radial and axial dependence of pore size, and information about the shape and interconnectivity of the pores.

The output of the technique also becomes a tool in numerical modeling of the potential flow and diffusion through this material, allowing access to information critical to material design. It could give insight into the phenomena occurring during in-vitro studies as well as provide an additional measure of certainty that the scaffold will function as is expected before it is tested on live models.