Human Tear Film Protein Sampling Using Soft Contact Lenses

Abstract

Human tear protein biomarkers are useful for detecting both ocular and systemic diseases. Unfortunately, existing tear film sampling methods (Schirmer strips (SS) and microcapillary tubes (MCT)) have significant drawbacks. Here we present an alternative tear protein sampling method using soft contact lenses (SCLs). First, we optimized SCL protein sampling in vitro, then performed in vivo studies in 6 human subjects. Using Etafilcon A SCLs and 4M guanidine-HCl for protein removal, we sampled an average of 60 +/- 31 ug of protein per eye. We also performed objective and subjective assessments of all sampling methods. Proteomic analysis by mass spectrometry (MS) revealed unique subsets of proteins for SS and SS/MCT methods. Additionally, SCLs had reduced levels of reflex tear protein zymogen granule protein 16 homolog B (ZG16B) versus SS and MCT. These experiments demonstrate SCLs as an accessible tear sampling method which may minimize reflex tearing and potentially aid biomarker discovery.

Proteomic Specificity of Soft Contact Lenses for Tear Protein Sampling

“…Samples were first prepped using 4M guanidine and the Filter Aided Sample Prep (FASP) method, as described previously [2]. Upon discovery of polymer contamination in our test samples, we used phosphate buffered saline (PBS, Genesse Scientific) and S-Trap (Protifi) micro spin columns to remove contaminants.…”

“…Tear peptides were analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) using instruments and methods as reported previously [2].…”

“…Tear sampling methodology significantly affects both subjects and researchers. For example, total protein for mass spectrometry (MS), subject comfort, ease of sampling, and tear type are all influenced by the sampling method [1,2]. In addition, significant proteomic differences exist between sampling approaches [1,2].…”

“…For example, total protein for mass spectrometry (MS), subject comfort, ease of sampling, and tear type are all influenced by the sampling method [1,2]. In addition, significant proteomic differences exist between sampling approaches [1,2]. Thus, it is important for researchers to determine which type of tear sampling best accomplishes the purposes of their research.…”

“…Our recent work demonstrated that soft contact lenses (SCLs) can be used to sample basal tears for proteomics [2]. When comparing SCLs to currently recommended tear sampling methods (microcapillary tubes [MCT] and Schirmer strips [SS]) [3], SCLs were shown to be comparable to MCT in both protein quality and quantity.…”