Assessing the effect of poly (ethylene oxide-b-lactide) block copolymer on the characteristics of perfluoropentane phase-shift nanoemulsions

Abstract

Acoustic droplet vaporization is the ultrasound-mediated phase shift of liquid perfluorocarbon emulsions into echogenic microbubbles. To reduce the emulsion's interfacial surface tension and minimize coalescence, the perfluorocarbon is coated with a surfactant. Copolymer shelled phase-shift nanoemulsions have emerged as potential diagnostic and therapeutic agents. The goal of this study is to understand how adding Poly (ethylene oxide-b-lactide) (PEO-PLLA) to a Pluronic F-68 shell formulation impacts the perfluoropentane (PFP) nanoemulsion size and polydispersity index (PDI). PFP nanoemulsions coated with Pluronic F-68 or a Pluronic F-68: PEO-PLLA (1:0.05 (v/v)) blend was prepared using high shear pressure homogenization (LV1, Microfluidics International, Corp.). Nanoemulsion size distributions and concentrations were measured (n=5) using a Beckman Coulter Multisizer 4. At 10,000 psi pressure and 1 passage through the homogenizer, the copolymer blend and Pluronic F-68 nanoemulsions had modal diameters of 0.73 ± 0.09 μm and 1.25 ± 0.09 μm, respectively. Additionally, the concentration was larger (6.6 ± 0.1×10−2 vs 5.56 ± 0.2×10−2 ml/ml) and the PDI smaller (0.070 ± 0.004 vs 0.129 ± 0.004) for the copolymer blend. All differences were statistically significantly different (p < .05). The inclusion of PEO-PLLA with Pluronic F-68 reduced the PFP nanoemulsion size and polydispersity, which may reduce experimental variability in acoustic droplet vaporization experiments.