Production and characterization of ECM powder: implications for tissue engineering applications

Two methods to produce a particulate form of extracellular matrix (ECM) from porcine urinary bladder were investigated. One method to produce the powder involved snap freezing a lyophilized form of the material and then pulverizing it in a grinding mill. The second method was similar except that the ECM was saturated in a solution of NaCl prior to snap freezing to precipitate salt crystals within the matrix before grinding. Several methods were utilized to analyze the particle size distribution and ultrastructure including sonic sifting, laser diffraction, and scanning electron microscopy (SEM). The salt precipitation method yielded a more uniform distribution of particles with a smaller mean diameter (158 vs. 191 microm). SEM showed that the particles produced by grinding without salt precipitation were irregularly shaped, sheet-like particles. ECM particles produced by the salt precipitation method were round and porous in appearance with many particles in the range of 1 microm which tended to agglomerate with the larger particles and with each other. We conclude that the production of a comminuted form of ECM is possible and that the uniformity of particle size and shape are dependent upon the manufacturing methodology.