Dose-dependent and synergistic effects of proteoglycan 4 on boundary lubrication at a human cornea-polydimethylsiloxane biointerface

Eye Contact Lens. 2012 Jan;38(1):27-35. doi: 10.1097/ICL.0b013e31823f7041.


Objectives: Proteoglycan 4 (PRG4), also known as lubricin, is a boundary lubricating mucin-like glycoprotein present on several tissue surfaces in the body. The objectives of this study were to (1) implement and characterize an in vitro boundary lubrication test at a human cornea-polydimethylsiloxane (PDMS) biointerface and (2) determine the dose-dependent and synergistic effects of PRG4, with hyaluronan (HA), on ocular surface boundary lubrication using this test.

Methods: Human corneas and model PDMS material were articulated against each other, at effective sliding velocities v(eff) between 0.3 and 30 mm/sec under physiologic loads of approximately 8 to 25 kPa. Samples were tested serially in (1) saline, PRG4 at 30, 100, 300 μg/mL resuspended in saline, then saline again or (2) saline, AQuify Comfort Eye Drops (containing 0.1% HA), 300 μg/mL PRG4 in saline, 300 μg/mL PRG4 in AQuify, then saline again. Both static and kinetic friction coefficients were calculated.

Results: PRG4 effectively lowered friction at the cornea-PDMS biointerface, both alone in a dose-dependent manner and in combination with HA. PRG4 reduced kinetic friction coefficients, <μ(kinetic, Neq)>, from approximately 0.30 in saline, to approximately 0.30, 0.24, and 0.17 in 30, 100, and 300 μg/mL PRG4, respectively. Values of <μ(kinetic, Neq)> in AQuify, approximately 0.32, were similar to those in saline; however, when combined with 300 μg/mL PRG4, values of <μ(kinetic, Neq)> were reduced to approximately 0.15.

Conclusions: PRG4 functions as an effective ocular surface boundary lubricant, both alone in a dose-dependent manner and in combination with HA.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biocompatible Materials / chemistry*
  • Cornea / drug effects*
  • Cornea / physiology
  • Dimethylpolysiloxanes / chemistry*
  • Dose-Response Relationship, Drug
  • Drug Synergism
  • Humans
  • Hyaluronic Acid / pharmacology
  • Lubrication
  • Proteoglycans / pharmacology*
  • Stress, Physiological / physiology
  • Surface Properties


  • Biocompatible Materials
  • Dimethylpolysiloxanes
  • PRG4 protein, human
  • Proteoglycans
  • Hyaluronic Acid