Absolute Quantification of Serum Exosomes in Patients with an SERS-Lateral Flow Strip Biosensor for Noninvasive Clinical Cancer Diagnosis

Abstract

Exosomes (exos) widely existing in body fluids show great potential for noninvasive cancer diagnosis. Quantitative analysis of exos is traditionally performed by targeting specific exosomal surface proteins, but it is often imprecise due to the common expression of exosomal proteins and subtle expression differences between different cancer subtypes. Herein, we report quantitative surface-enhanced Raman spectroscopy (SERS) of serum exos through a combination of a paper-based lateral flow strip (LFS) biosensor with multivariate spectral unmixing analysis rather than simply quantifying exosomal proteins. Our SERS-LFS biosensor enables absolute quantification of two different serum exos with a limit of detection down to ∼106 particles/mL for both exos. We further exemplify the application of this strategy in quantitative dual-plex detection of serum exos from breast cancer patients. We find that human epidermal growth factor receptor 2+ (HER2+) and luminal A breast cancer patients undergoing no surgery are enriched in serum exos derived from SKBR-3 cells and MCF-7 cells (denoted as SKBR and MCF exos), respectively. The surgical treatment of these breast cancer patients accompanies an obvious decrease of either SKBR or MCF exos in the serum. These results suggest the great potential of the combination of the SERS-LFS biosensor and multivariate spectral unmixing for breast cancer subtyping and therapeutic surveillance with the powerful quantitative capability of exos in clinical samples.

Rational Design of Near‐infrared II Plasmonic Optofunctional Materials for Diagnostic and Therapeutic Applications

“…[63,64] Overall, SERS presents many prominent features for biosensing and bioimaging: i) SERS is able to perform label-free or label-based quantitative analysis with ultrahigh sensitivity even down to single molecule level; ii) SERS spectra enrich abundant molecular fingerprint information characteristic of biological systems or events; iii) SERS is resistant to photobleaching and photodegradation so that the SERS detection is suitable for longitudinal long-term monitoring, much superior to fluorescence; iv) The spectral bandwidth of the SERS bands is usually 10-100 times narrower than that of fluorescence emission from organic dyes, inorganic nanocrystals or quantum dots so that the SERS techniques allow for convenient multiplex detection with a single wavelength excitation; v) SERS-active nanostructures can be easily designed by tailoring the particle size, shape, and surface chemistry for different purposes. These unique features have enabled SERS for a wide range of biomedical applications, including in vitro and in vivo biosensing, [65][66][67][68][69][70] multimodal image-guided therapy, [71][72][73] SERS-guided surgical navigation with precise delineation of tumor margins and intraoperative removal of microscopic tumor foci. [73][74][75][76]…”

SERS biosensors for liquid biopsy towards cancer diagnosis by detection of various circulating biomarkers: current progress and perspectives

“…Recently, Su et al . developed two types of paper-based devices for the quantification of breast cancer exosomes in serum: a 3-plex VFA and a 2-plex LFA [ 177 , 178 ]. These two platforms are vastly different, with distinct advantages and disadvantages.…”

“…Su et al . ’s LFA sought to overcome this issue by integrating two spectrally different SERS probes made of AuSts coupled with distinct Raman reporters and aptamers against HER2 and MUC1 on the conjugate pad, while coating the test line with anti-CD63 aptamers [ 178 ]. Similar to Mao et al .…”

“…Similar to Mao et al . , HER2 and MUC1 were simultaneously detected on a single test line using these two SERS probes with distinct Raman reporters [ 176 , 178 ]. Su et al .…”

“…Su et al . took this a step further by using the combined Raman signals of the SERS probes to generate distinct Raman signatures that can differentiate between exosomes derived from SKBR-3 and MCF-7 cell lines (SKBR and MCF exosomes) [ 178 ]. A mixture of SKBR and MCF exosomes can result in a total of four Raman signals on the test line: SKBR-3 exosomes + HER2 /MUC1 probes, and MCF exosomes + HER3/MUC1 probes.…”