Adhesion of silicone oil and emulsification: an in vitro assessment using a microfluidic device and ‘Eye‐on‐a‐Chip’

Abstract

Purpose: Silicone oil (SiO) with additives of high-molecular-weight (HMW) SiO molecules, eases both the injection and removal. When used inside an eye, it remains unclear how increasing extensional viscosity of SiO might reduce emulsification. Using cell-lined models, this study aims to understand the reason why SiO with HMW is less prone to emulsification. Methods: The adhesion of SiO was studied and recorded in a cell-coated microchannel by optical microscopy. The resistance of SiO against emulsification was tested on another cell-coated eye-on-a-chip platform, which was subject to simulated saccadic eye movements, for 4 days. Silicone oil (SiO) candidates with HMW, SiO HMW2000 and SiO HMW5000 , and their counterparts SiO 2000 and SiO 5000 without HMW, were tested. The quantity of the SiO emulsified droplets formed was assessed daily by optical microscopy. Results: When flowing in the microchannel, SiO adheres on the cell-coated substrate. The number of droplets is generally lower in SiO with HMW than their counterparts. At the end of the experiment, the average numbers of droplets in SiO 2000 (29.1 AE 41.0) and SiO 5000 (9.1 AE 19.5) are higher than those in SiO HMW2000 (6.0 AE 4.5) and SiO HMW5000 (5.6 AE 4.1). Conclusion: A new mechanism of emulsification of SiO is proposed: SiO adheres to ocular tissue to form emulsified droplets. The presence of HMW, which increases the extensional viscosity, may resist the break-up of SiO from the substrate to form emulsified droplets. When tested in a physiologically representative platform, the use of HMW in SiO generally reduces the number of droplets formed in vitro.

Amphiphilic additives in silicone oil tamponade and emulsification: an eye‐on‐a‐chip study

“…; Lu et al. ). In brief, SiO samples (0.5 mL) were injected to the eye chips made of Poly(methyl methacrylate) (PMMA).…”

“…; Lu et al. ). Adding high‐density materials yields SiO blends that possess a higher density than water to tackle inferior retinal diseases (Joussen et al.…”

“…; Lu et al. ), with simulated saccadic eye movements for four consecutive days. This platform allows the better mimicking of both the mechanical and physiological micro‐environment of the posterior segment of the eye to study the emulsification of SiO tamponade in vitro .…”

“…Different additives were added to the conventional SiO for different indications of use. For instance, addition of high-molecularweight components eases the injection and improves the resistance against emulsification (Williams et al 2010;Caramoy et al 2015;Lu et al 2019). Adding high-density materials yields SiO blends that possess a higher density than water to tackle inferior retinal diseases (Joussen et al 2007).…”

“…Emulsification of SO with amphiphilic additives is compared with the conventional SO with similar shear viscosities. The study was carried out on our previously developed eye-cavity-on-a-chip platform (Chan et al 2015b;Lu et al 2019), with simulated saccadic eye movements for four consecutive days. This platform allows the better mimicking of both the mechanical and physiological micro-environment of the posterior segment of the eye to study the emulsification of SiO tamponade in vitro.…”