Acoustic droplet vaporization-mediated dissolved oxygen scavenging in blood-mimicking fluids, plasma, and blood

Acoustic droplet vaporization (ADV) has been shown to reduce the partial pressure of oxygen (PO₂) in a fluid. The goals of this study were three-fold: 1) to determine the ADV pressure amplitude threshold in fluids that had physiologically relevant values for surface tension, protein concentration, and viscosity; 2) to assess whether these parameters and fluid mixing affect ADV-mediated PO₂ reduction; and 3) to assess the feasibility of ADV-mediated PO₂ reduction in plasma and whole blood. In vitro ADV experiments were conducted using perfluoropentane droplets (number density: 5 × 10⁶ ± 0.2 × 10⁶/mL) dispersed in fluids (saline, polyvinylpyrrolidone solutions, porcine plasma, or porcine whole blood) that had a physiological range of surface tensions (62-68 mN/m), protein concentrations (0 and 68.7 mg/mL), and viscosities (0.7-4 cP). Droplets were exposed to pulsed ultrasound (5 MHz, 4.25 MPa peak negative pressure) while passing through a 37 °C flow system with inline PO₂ sensors. In select experiments, the fluid also passed through mixing channels after ultrasound exposure. Our results revealed that the ADV pressure thresholds were the same for all fluids. Surface tension and protein concentration had no effect on PO₂ reduction. Increasing viscosity attenuated PO₂ reduction. However, the attenuated effect was absent after fluid mixing. Furthermore, ADV-mediated PO₂ reduction in whole blood (30.8 ± 3.2 mmHg) was less than that in a polyvinylpyrrolidone solution (40.2 ± 2.1 mmHg) with equal viscosity. These findings should be considered when planning clinical studies of ADV-mediated PO₂ reduction and other biomedical applications of ADV.