posted on 2024-01-16, 07:29authored byChuan Zhang, Kaixin Zheng, Chi Li, Ranran Zhang, Yicheng Zhu, Linxiao Xia, Yicheng Ma, Hans M. Wyss, Xiaoyu Cheng, Sailing He
Detecting
proteins in ultralow concentrations in complex media
is important for many applications but often relies on complicated
techniques. Herein, a single-molecule protein analyzer with the potential
for high-throughput applications is reported. Gold-coated magnetic
nanoparticles with DNA-labeled antibodies were used for target recognition
and separation. The immunocomplex was loaded into microdroplets generated
with centrifugation. Immuno-PCR amplification of the DNA enabled the
quantification of proteins at the level of single molecules. As an
example, ultrasensitive detection of α-synuclein, a biomarker
for neurodegenerative diseases, is achieved. The limit of detection
was determined to be ∼50 aM in buffer and ∼170 aM in
serum. The method exhibited high specificity and could be used to
analyze post-translational modifications such as protein phosphorylation.
This study will inspire wider studies on single-molecule protein detection,
especially in disease diagnostics, biomarker discovery, and drug development.