The development of simple, light-weight, low-cost, and rapid detection devices for applications related to clinical diagnosis, health care, and environmental monitoring has attracted increasing interest. Scientists show a portable surface plasmon resonance (SPR) biosensor that uses a smartphone as a sensing platform. This SPR sensor uses surface electromagnetic evanescent waves at the metal-dielectric interface and is highly sensitive to changes in the small refractive index (RI). Therefore, SPR sensors are used in biomolecular interaction analysis, medical diagnostics, environmental monitoring, and food safety.
Fig.1 Instrumentation of the smartphone-based surface plasmon resonance imaging biosensor. (Liu, 2015)
MicroRNAs (miRNAs) is a single-stranded, non-coding RNA molecule of the short size that plays a crucial role in cellular processes like apoptosis, proliferation, differentiation, invasion, and migration. The aberrant expression of miRNA has been correlated to many human diseases such as cancer, cardiovascular diseases, and others. miRNA exhibits remarkable stability when released into circulation, making it a promising biomarker candidate for disease diagnosis.
However, due to its short length and low abundance, the detection of miRNA remains complex. Scientists developed a highly specific plasmonic biosensor for ultrasensitive miRNA detection in plasma from pancreatic cancer patients. This sensing platform allows for simple, rapid (30 minutes) and enzyme-free detection of miRNA with a limit of detection (LOD) of 9 ×10-9 mol/m3 (pM).
Fig.2 Schematic representation of cancer-related biomolecules such as cells, proteins, nucleic acids and microvesicles circulating into the bloodstream, and collection of these biomarkers by liquid biopsy. (Bellassai, 2019)
Both circulating tumor cells (CTCs) and circulating tumor DNA (ctDNA) provide deeper insights into the understanding of the dynamic fluctuations and characteristics of various tumors, contributing to more accurate profiling of various types of cancer. However, the ultralow abundance, inherent heterogeneity, and the high background levels of circulating wild-type DNA make the detection of CTCs and ctDNA even harder.
Scientists describe the most relevant plasmonic platforms able to detect ctDNA or CTCs in biofluids for cancer diagnosis by developing innovative and simple nano-plasmonic assays for label-free target detection in blood with excellent selectivity.
Circulating proteins represent further promising biomarkers for early cancer diagnosis, whose expression, abundance, localization, and biochemical modifications are greatly influenced by pathological process. Scientists selected the most clinically-relevant protein biomarkers that have been already implemented in clinical practice, and used SPR technology for their quantification in a real biological sample at a lower concentration. Nanoparticle-enhanced SPR-based sandwich detection has been regarded as a potential assay in early cancer diagnosis.
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