Cavitation dynamics in commercial scaffolds and native extracellular matrix

Commercial scaffolds and native extracellular matrix (nECM) are commonly used for cell reseeding and in vitro tissue models; however, how their viscoelastic differences affect acoustic cavitation remains unclear. Using focused ultrasound (FUS), we examined how pulse length and peak negative pressure (p-) influence cavitation probability in PureCol EZ-Gel, Cultrex Ultimatrix, and nECM derived from decellularized porcine kidney (n = 8 each). A 3.68-MHz FUS transducer (f# = 1) delivered 100–800 µs pulses at 1 Hz PRF with p-≤6.2 MPa. Cavitation events were captured using brightfield microscopy and high-speed imaging at 20 000 fps. A viscoelastic Keller-Miksis-Kelvin-Voigt bubble model was compared to the experimental results. Among the tested materials, nECM consistently showed higher cavitation thresholds than PureCol and Cultrex, supporting the literature that higher elastic modulus suppresses cavitation. In nECM, bubble radius significantly increased from 13.5 ± 2.5 µm to 24.1 ± 4.8 µm as p- increased from 4.1 to 5.8 MPa (p = 0.023). Increasing pulse length from 200 to 600 µs consistently reduced cavitation thresholds in nECM, while thresholds in commercial scaffolds plateaued beyond 300 µs. The model matched relatively well with the experimental results and indicated viscosity damped bubble expansion with minimum radial expansion observed in Cultrex; R max = 5.44 µm. Future work will compare nECM derived from porcine liver with the tested scaffolds/nECM. [Work supported by NSF CAREER 1943937.]