Design of an artificial skin. Part III. Control of pore structure.

Several methods are compared for preparing collagen-glycosaminoglycan (GAG) membranes of high or low porosity. Collagen-GAG membranes have been used to cover satisfactorily large experimental full-thickness skin wounds in guinea pigs over the past few years. Methods studied as means for controlling pore size are confined to purely physical processes which do not require use of additives or chemical reagents to form the porous membrane. We find that membranes, initially swollen in distilled water or saline, shrink linearly to no less than 94% of original dimension after freeze drying; to 75% after critical point drying (from CO2, following water-ethanol exchange); and to 41% of original dimension following air drying from the swollen state. Scanning electron microscopic study of the pore structure resulting from eah drying procedure confirms our major conclusion: A carefully designed freeze drying process, two variants of which are described in detail, yields membranes with the highest mean pore size, as measured by quantitative stereological procedures. Critical point drying gave significantly more shrinkage and a lower mean pore size than either one of the two freeze drying procedures used.