Human Tear Protein Analysis Using a Quantitative Microfluidic System: A Pilot Study

Objectives: Human tears have the potential to be used as biomarkers to aid in the diagnosis and management of dry eye disease (DED). This prospective, controlled pilot study aimed to investigate the hypothesis that a panel of tear protein profiles can be detected and are repeatable when analyzed using a miniaturized quantitative microfluidic system.Methods: Ten participants were recruited following institutional ethics committee approval. Participants attended two visits 1 week apart when the following measurements were taken in a sequence: tear meniscus height, noninvasive breakup time, ocular redness, tear collection, and corneal and conjunctival staining. Basal tears (>4 mu L) were collected using glass microcapillary tubes. Tears were processed to analyze a panel of proteins (14-230 kDa) following the manufacturer's guidelines using a miniaturized quantitative microfluidic system (Protein 230 LabChip with Agilent 2100 Bioanalyzer). Demographics of the clinical measurements and a comparison of the panel of identified proteins and their repeatability were made.Results: Mean age of the participants was 20.8 +/- 1.6 years, nine were females, three fulfilled the TFOS DEWS-II diagnostic criteria for DED. The total protein concentration across participants was 6.72 +/- 3.56 mg/mL. Several proteins (lysozyme C, lipocalin 1, IgA light chain, zinc-alpha 2-glycoprotein, albumin, and lactoferrin) were identified at both visits for seven or more participants. There were no significant differences ( P >0.05) in individual protein concentrations between the two visits. A high correlation was found between the two visits for all proteins where correlation coefficient ranged between 0.63 and 0.98 ( P <0.05).Conclusion: The protein profiles measured by the quantitative microfluidic system are repeatable, thus validating quantitative microfluidic system as a reliable method for investigating a panel of tear proteins. This method is quick, affordable, requires only 4 mu L of tear, and is relatively easy method to perform that can be incorporated in a clinical setting. Further studies in larger clinical setting may be beneficial exploring the usability of this method in various patient groups.