Scaffold materials are essential for organ construction and cell culture. Among these, Extracellmatrix (ECM) prepared through the decellularization of biological tissues is an indispensable material for the advancement of organ engineering. Various methods for extracting ECM have been proposed, but among them, the method utilizing cavitation without relying on chemicals is one of the most promising approaches for medical applications. Previous studies have proposed techniques utilizing ultrasonic cavitation (UC). Still, these methods have efficiency issues, as the range of cavitation generated by ultrasound is narrow and its density is low, posing challenges for industrial-scale preparation. On the other hand, the development of technologies actively utilizing hydrodynamic cavitation(HC) is important for the industrialization of ECM hydrogels and the establishment of the field of organ engineering. In this report, we establish a manufacturing technology for ECM hydrogels using cavitation by utilizing advanced dispersion technology capable of dispersing particles in microchannels. We perform novel processing of ECM using HC, compared to UC, and assess the basic characteristics for adjusting ECM hydrogels using cavitation.

Experiments were conducted using ECM generated by UC using an ultrasonic homogenizer and HC using a high-pressure homogenizer (NAGS20, Jokoh, Japan). The ECM was prepared using decellularized pig kidneys (Tokyo Shibaura Zouki). Decellularization was performed by thawing frozen organs, perfusing them with a surfactant, and removing cells. The micronized samples were evaluated using a rheometer, particle size measurement device (Partica LA-960V2, Horiba), and SEM observation. Additionally, cavitation characteristics in microchannels were evaluated using CFD analysis.

As a result, particle size distribution and rheological properties were evaluated using a rheometer. The particle size distribution characteristics showed that untreated samples were dominated by particles in the 100–300 um range, with a maximum frequency at approximately 0.4um. In contrast, samples treated with UC exhibited a significant reduction in the dominant large-particle ECM, resulting in particles of several micrometers in size. As ultrasonic intensity and processing time increased, the maximum value of the particle size distribution shifted toward smaller particle sizes, and the second peak at approximately several micro scale gradually decreased, converging toward the maximum frequency on the smaller particle size side. HC demonstrated that micro-size reduction progresses with an increase in the number of cavitation cycles, and after five cycles, the distribution remains essentially unchanged. These results indicate that HC achieves processing equivalent to UC and, due to its ability for continuous processing, is considered a valuable technology for the production of ECM hydrogels.

In conclusion, Hydrodynamic Cavitation enables micro-size reduction of ECM.