Label-Free Nanosensing Platform for Breast Cancer Exosome Profiling

Abstract

Breast cancer accounts for 11.6% of all cancer cases in both genders. Even though several diagnostic techniques have been developed, the mostly used are invasive, complex, time-consuming, and cannot guarantee an early diagnosis, significantly constraining the tumor treatment success rate. Exosomes are extracellular vesicles that carry biomolecules from tissues to the peripheral circulation, representing an emerging noninvasive source of markers for early cancer diagnosis. Current techniques for exosomes analysis are frequently complex, time-consuming, and expensive. Raman spectroscopy interest has risen lately, because of its nondestructive analysis and little to no sample preparation, while having very low analyte concentration/volume, because of surface enhancement signal (SERS) possibility. However, active SERS substrates are needed, and commercially available substrates come with a high cost and low shelf life. In this work, composites of commercial nata de coco to produce bacterial nanocellulose and in-situ-synthesized silver nanoparticles are tested as SERS substrates, with a low cost and green approach. Enhancement factors from 104 to 105 were obtained, detecting Rhodamine 6G (R6G) concentrations as low as 10–11 M. Exosome samples coming from MCF-10A (nontumorigenic breast epithelium) and MDA-MB-231 (breast cancer) cell cultures were tested on the synthesized substrates, and the obtained Raman spectra were subjected to statistical principal component analysis (PCA). Combining PCA with Raman intravariability and intervariability in exosomal samples, data grouping with 95% confidence was possible, serving as a low-cost, green, and label-free diagnosis method, with promising applicability in clinical settings.

Surface-Enhanced Raman Scattering (SERS) Spectroscopy for Sensing and Characterization of Exosomes in Cancer Diagnosis

“…For these reasons, they have been largely preferred for biosensing applications over direct approaches. Nonetheless, the current literature survey on exosome SERS analysis shows a larger number of reports based on direct approaches [ 69 , 70 , 71 , 72 , 73 , 74 , 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 , 83 , 84 , 85 , 86 , 87 , 88 , 89 , 90 , 91 ] than indirect ones [ 92 , 93 , 94 , 95 , 96 , 97 , 98 , 99 , 100 , 101 ]. This apparent anomaly may be explained by taking into considerations the intrinsic exosomal heterogeneity that currently burdens the identification of specific disease-related biomarkers for selective separation and labelling of clinically relevant exosome subpopulations [ 90 , 99 , 102 ].…”

“…Besides the direct casting of preformed colloids onto glass-slide surfaces, inexpensive SERS substrate can be generated by in-situ synthesis of plasmonic nanoparticles anchored onto the solid support. In this regard, Ferreira et al [ 81 ] reported the simple fabrication of a hybrid SERS material via in situ silver nanoparticles growth into bacterial cellulose (BC), a low-cost and abundant support obtained from commercial nata de coco. The viability of the substrate for direct SERS analysis of exosomes was demonstrated in the efficient discrimination of exosome samples isolated from MCF-10A (nontumorigenic breast epithelium) and MDA-MB-231 (breast cancer) cell cultures.…”

Emerging Diagnostic Potential of Tumor-derived Exosomes

“…However, the step-by-step processing and analysis of exosomes is time and labor-consuming. Moreover, the samples are also vulnerable to external contamination [109]. Faster and more directional extraction procedures such as alternating current (AC) chip and microfluidic chip have been developed.…”

Transcriptome Reprogramming of CD11b+ Bone Marrow Cells by Pancreatic Cancer Extracellular Vesicles

“…The EV isolation/purification procedure was performed as previously described (Ferreira et al, 2019). Specifically, the conditioned medium was submitted to two initial centrifugations (10 min, 500 g and 20 min, 3,000 g) to remove any suspended or dead cells in the medium.…”