Measuring the Compressibility of Cellulose Nanofiber-Stabilized Microdroplets Using Acoustophoresis

Abstract

Droplets with a liquid perfluoropentane core and a cellulose nanofiber shell have the potential to be used as drug carriers in ultrasound-mediated drug delivery. However, it is necessary to understand their mechanical properties to develop ultrasound imaging sequences that enable in vivo imaging of the vaporization process to ensure optimized drug delivery. In this work, the compressibility of droplets stabilized with cellulose nanofibers was estimated using acoustophoresis at three different acoustic pressures. Polyamide particles of known size and material properties were used for calibration. The droplet compressibility was then used to estimate the cellulose nanofiber bulk modulus and compare it to experimentally determined values. The results showed that the acoustic contrast factor for these droplets was negative, as the droplets relocated to pressure antinodes during ultrasonic actuation. The droplet compressibility was 6.6–6.8 ×10−10 Pa−1, which is higher than for water (4.4×10−10 Pa−1) but lower than for pure perfluoropentane (2.7×10−9 Pa−1). The compressibility was constant across different droplet diameters, which was consistent with the idea that the shell thickness depends on the droplet size, rather than being constant.

Cellulose Nanofiber-Coated Perfluoropentane Droplets: Fabrication and Biocompatibility Study

“…Previous studies have shown that CNF-shelled PFP droplets are stabilized via a Pickering mechanism. 11 Figure 2A shows that similarly to the previous work by Ghorbani et al 11 and Loskutova et al, 27 CNFs act as a stabilizing agent as they form a coherent layer on the surface of the droplets. The initial droplet size of the produced emulsion is determined by the energy density, ie, energy dissipated per unit volume of the processed mixture, with an increase in energy output decreasing the size of produced droplets.…”

“…The two droplet components that may have a cytotoxic effect is the cationic CNFs and PFP. Previous studies have estimated the volume fraction of CNF to be between 1.5% and 8.8% 27 and the density of CNFs to be 1.5 g/cm 3 . 53 Therefore, the volume of CNF present in 72 droplets should be between 1.68 and 11.21 pL, or between 2.53 and 16.82 ng.…”

“…Recently, perfluoropentane (PFP) droplets stabilized by cellulose nanofibers (CNFs) were developed by Ghorbani et al 11 The acoustic and mechanical properties of these droplets have been studied both in numerical and experimental studies; [25][26][27] however, the biological compatibility of these droplets is still unknown. The aim of this work was to study the effect of CNF-shelled PFP droplets on cancer cell viability, using murine breast cancer cell line 4T1 as a model.…”

Measuring and simulating the biophysical basis of the acoustic contrast factor of biological cells

“…c HNC Tu686, 686LN, M4e, 37B -head and neck cancer cells whereas M4e & 37B have a higher metastatic potential than Tu686 & 686LN; density and compressibility from Wang et al ). e MESC2.10 -human embryonic ventral mesencephalic cell; MESC2.10-diff4d -human embryonic ventral mesencephalic cell differentiated in a special medium for 4 days; Augustsson et al 21 ; the acoustic contrast Φ is measured via acoustic manipulation at 1.97 MHz; we multiplied the average Φ from 21 by a factor of 3 to match our definition of Φ. f Loskutova et al 31 demonstrated a negative ACF, whereas the ACF is dependent on the pressure amplitude. g SaOs-2 & LM5 -human bone cancer cell line with a lower respectively higher metastatic potential and ACF data generated during this study.…”