Removal of Avitene microfibrillar collagen hemostat by use of suitable transfusion filters.

We assessed the ability of two commercial filters (Pall RC100 and Statlabs 20 microns) to filter out Avitene microfibrillar collagen hemostat from suspension. Quantitative determination of the collagen content as well as scanning electron and light microscopy, particle counting, and platelet aggregometry of filtrates revealed that these filters effectively remove potentially thrombogenic particles of Avitene microfibrillar collagen hemostat. The filters removed at least 97% of the total collagen, as determined by hydroxyproline analysis. The collagen that passed through the Pall filter did not pellet upon ultracentrifugation. Scanning electron and light microscopic analysis revealed no Avitene microfibrillar collagen hemostat particulates in the Pall filtrates but did reveal the presence of a significant number of approximately 1- to 8-microns particulates in the Statlabs filtrates. Concentrates of the filtrates from either of the two filters, however, did not promote platelet aggregation. Through ultracentrifugation and infrared analysis, the filtrates were found to consists of soluble, partially denatured collagen. The risk associated with the reintroduction of collagen particulates into the vasculature can be significantly reduced by use of appropriate, currently available blood-transfusion filters.

Scattering of light from histologic sections: a new method for the analysis of connective tissue.

We have developed a light scattering technique that can be used to analyze the orientation and diameter of collagen fibers in histologic sections of connective tissue. Scattering patterns obtained by transmitting laser light through sections of tissue contain information both on the orientation, degree of alignment, and size of the constituent collagen fibers. Analysis of the azimuthal intensity distribution of scattered light yields numerical values of the degree of alignment by use of an orientation index, S, which is chosen to vary between 0 for randomly oriented fibers and 1 for a perfectly aligned arrangement. The average diameter of the collagen fibers is calculated from the scattering angle at which the intensity reaches its first minimum. These measurements are independent of the nature of histologic stain. The procedure is illustrated by measurements obtained with sections of the guinea pig dermis and of control scar. We conclude from our experiments that light scattering can complement the analysis of tissue architecture typically performed with the light microscope.