Tear fluid is emerging as a valuable resource for biomarker discovery, but its low sample volume and dynamic composition pose significant challenges for analytical testing. Most tear proteomics studies have focused on samples collected with Schirmer strips, while capillary tube collection has received less attention. To address these challenges, we developed a novel in-capillary trypsin digestion workflow that requires as little as 0.5 μL of tear fluid for bottom-up shotgun proteomics. This method uses liquid chromatography-tandem mass spectrometry (LC-MS/MS) to identify a higher number of proteins with enhanced efficiency compared to previously reported methods, which typically required 5-10 μL of pooled tear fluid. Using the same microcentrifuge tube for both tear collection and sample processing, this streamlined workflow simplifies sample handling and minimizes both sample loss and experimental errors associated with sample transfer. This method also efficiently reduced sample processing time to under 2 hours prior to overnight trypsin digestion, compared to the 5-8 hours required by other methods. With this workflow, we identified 500-800 proteins per 0.5 μL sample without the need for fractionation, allowing for at least three technical replicates. This optimized workflow greatly enhances the efficiency of tear proteomics for biomarker discovery.

Cardiovascular risk factors (CRFs) such as hypertension, high cholesterol, and diabetes are increasingly implicated in cognitive decline and cerebral small vessel disease (cSVD). White matter hyperintensities (WMH), a hallmark of cSVD, are strongly linked to cognitive impairment, but their underlying mechanisms remain unclear. Blood-brain barrier (BBB) dysfunction has been proposed as a potential contributor to WMH development. This study aimed to explore the relationships between CRFs, BBB integrity, and WMH burden. We analyzed 155 participants from the Biomarkers and Cognition Study, Singapore, assessing CRFs through blood tests for glucose and lipid profiles, alongside blood pressure measurements. WMH volume was quantified using MRI, and an in vitro assay evaluated the impact of plasma on BBB integrity using human brain microvascular endothelial cells. Results showed that plasma from participants with higher WMH burden correlated with increased BBB disruption, which was further associated with higher blood pressure, elevated blood glucose, and lipid levels. Both periventricular and subcortical WMH were linked to BBB disruption. These findings suggest that CRFs contribute to BBB dysfunction, promoting WMH development and cognitive decline in cSVD. Further research is needed to clarify the precise mechanisms driving these associations.