Digital Microfluidics for Microproteomic Analysis of Minute Mammalian Tissue Samples Enabled by a Photocleavable Surfactant

Proteome profiles of precious tissue samples have great
clinical
potential for accelerating disease biomarker discovery and promoting
novel strategies for early diagnosis and treatment. However, tiny
clinical tissue samples are often difficult to handle and analyze
with conventional proteomic methods. Automated digital microfluidic
(DMF) workflows facilitate the manipulation of size-limited tissue
samples. Here, we report the assessment of a DMF microproteomics workflow
enabled by a photocleavable surfactant for proteomic analysis of minute
tissue samples. The surfactant 4-hexylphenylazosulfonate (Azo) was
found to facilitate fast droplet movement on DMF and enhance the proteomics
analysis. Comparisons of Azo and n-Dodecyl β-d-maltoside (DDM) using small samples of HeLa digest standards
and MCF-7 cell digests revealed distinct differences at the peptide
level despite similar results at the protein level. The DMF microproteomics
workflow was applied for the sample preparation of ∼3 μg
biopsies from murine brain tissue. A total of 1969 proteins were identified
in three samples, including established neural biomarkers and proteins
related to synaptic signaling. Going forward, we propose that the
Azo-enabled DMF workflow has the potential to advance the practical
clinical application of DMF for the analysis of size-limited tissue
samples.