Oral Presentation Australia and New Zealand Society for Extracellular Vesicles Conference 2023

Upconversion Nanoparticle-Enhanced Ultrasensitive Lateral Flow Assay for Detecting PD-L1-Positive Small Extracellular Vesicles (#10)

Pritam Bordhan 1 2 3 , Sareh Zhand 1 3 , Libing Fu 1 2 , Jin Dayong 1 2 , Yuen Yee Cheng 1 4 , Wen Shihui 1 2 , Majid E Warkiani 1 2 3
  1. Institute for Biomedical Materials & Devices, Faculty of Science, University of Technology Sydney, Ultimo, NSW, Australia
  2. ARC Research Hub for Integrated Device for End-User Analysis at Low Levels, Faculty of Science, University of Technology Sydney, Ultimo, NSW, Australia
  3. School of Biomedical Engineering, University of Technology Sydney, Ultimo, NSW, Australia
  4. Asbestos Disease Research Institute, Concord Hospital, Sydney, NSW, Australia

 

Introduction:  Small extracellular vesicles (sEVs) are integral to liquid biopsy and essential in physiological and pathological processes, including immune response [1, 2]. PD-L1 protein is a vital immune checkpoint, and sEV-bound PD-L1 has been detected in multiple cancer types and is a relevant biomarker for monitoring cancer progression and immunotherapy response [3, 4]. Here, for the first time, we developed a quantitative lateral flow assay (LFA) using highly doped upconversion nanoparticles (UCNPs) for ultrasensitive detection of PD-L1-positive sEVs.

Methods: sEVs were isolated from three human mesothelioma cell lines using ultracentrifugation. The NaYF4:40%Yb,4%Er@NaYF4 core-shell nanocrystals were synthesised, surface modified with copolymers, and bioconjugated with CD63 and PD-L1 antibodies. UCNP probes were used in the LFA to detect target analytes in samples using a strip reader integrated with a 980nm laser.

Results: The limit of detection (LoDs) for CD63 and PD-L1 proteins in the UCNP-LFA were 58 pg/ml and 10 pg/ml, respectively. The UCNP-LFA detected CD63 and PD-L1 positive sEVs at concentrations as low as 1.03 × 103 sEVs/µl and 2.15 × 103 sEVs/µl, respectively. The UCNP-LFA detected sEV markers from ~1000 lower sEV concentrations than traditional ELISA. It was also ~100 times more sensitive than other colorimetric LFA studies [5, 6].

Conclusions:  PD-L1 expression on sEVs excellently reflects the tumour environment in cancer patients and has significant diagnostic potential [7]. The technology represents a push towards simple and sensitive sEV biomarker detection that facilitates non-invasive and dynamic analyses of early-stage cancer biomarkers, particularly in clinical settings.  

 

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