title: In Vitro Modeling of Emulsification of Silicone Oil as Intraocular Tamponade Using Microengineered Eye-on-a-Chip.
abstract: OBJECTIVE
  There is a lack of a standardized methodology or a physiologically realistic in vitro model to investigate silicone oil (SO) emulsification. In this study, we replicated the SO-aqueous interface within a microfluidic chip to study the formation of SO emulsion droplets in the eye cavity.
  
  
  METHODS
  A chip made of poly(methylmethacrylate) was used to represent a cross-section of the posterior eye chamber. A retinal ganglion cell line was coated on the inner surface of the chamber to mimic the surface property of the retina. Silicone oil of different viscosities were tested. The SO-aqueous interface was created inside the chip, which, in turn, was affixed to a stepper-motor-driven platform and subjected to simulated saccadic eye movement for four days. Optical microscopy was used to quantify the count and size of SO emulsified droplets.
  
  
  RESULTS
  Among SO of different viscosities, SO 5 centistokes (cSt) emulsifies readily, and a high number of droplets formed inside the chip. Silicone oil 100 cSt led to fewer droplets than 5 cSt, but the droplet count was still significantly higher than other SO of higher viscosities. There were no significant differences in the number of droplets among SO with viscosities of 500, 1000, and 5000 cSt. In all SOs tested, the number of droplets increased, whereas their size decreased with longer duration of simulated saccades.
  
  
  CONCLUSIONS
  The study platform allows quantification of the number and size of emulsified SO droplets in situ. More importantly, this platform demonstrates the potential of microtechnology for constructing a more physiologically realistic in vitro eye model. Eye-on-a-chip technology presents exciting opportunities to study emulsification and potentially other phenomena in the human eye.
authors.affiliation: Department of Mechanical Engineering, Faculty of Engineering, University of Hong Kong, Hong Kong 2Department of Ophthalmology, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong.
authors.forename: Yau Kei
authors.initials: YK
authors.lastname: Chan
authors.affiliation: Department of Mechanical Engineering, Faculty of Engineering, University of Hong Kong, Hong Kong.
authors.forename: Kwun Hei Samuel
authors.initials: KH
authors.lastname: Sy
authors.affiliation: Department of Mechanical Engineering, Faculty of Engineering, University of Hong Kong, Hong Kong.
authors.forename: Chun Yu
authors.initials: CY
authors.lastname: Wong
authors.affiliation: Department of Mechanical Engineering, Faculty of Engineering, University of Hong Kong, Hong Kong.
authors.forename: Ping Kwan
authors.initials: PK
authors.lastname: Man
authors.affiliation: Department of Ophthalmology, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong.
authors.forename: David
authors.initials: D
authors.lastname: Wong
authors.affiliation: Department of Mechanical Engineering, Faculty of Engineering, University of Hong Kong, Hong Kong 3University of Hong Kong-Shenzhen Institute of Research and Innovation (HKU-SIRI), Shenzhen, Guangdong, China.
authors.forename: Ho Cheung
authors.initials: HC
authors.lastname: Shum
mesh_terms: D002460:Cell Line; D004655:Emulsions; D058450:Endotamponade; D006801:Humans; D008953:Models, Anatomic; D008954:Models, Biological; D011109:Polymethacrylic Acids / Q000737:chemistry; D012165:Retinal Ganglion Cells; D012438:Saccades / Q000502:physiology*; D012827:Silicone Oils / Q000737:chemistry*; D013499:Surface Properties; D014783:Viscosity
chemical_list: D004655:Emulsions; D011109:Polymethacrylic Acids; D012827:Silicone Oils