Exosomal biomarkers: A novel frontier in the diagnosis of gastrointestinal cancers

Table 4 Comparison of exosome detection methods: Advantages and disadvantages

Detection method	Advantages	Disadvantages	Ref.
Nanoparticle tracking analysis	Simple; can determine both particle size and concentration; can detect vesicles in the 10-1000 nm diameter range, covering the typical exosome size range of 50-150 nm	N/A	[66,67]
Dynamic light scattering	Provides information on relative particle size; can calculate absolute size distribution when microvesicle concentration is known; accurate for samples with exosomes of one specific size	Larger particles may hinder detection of smaller particles in samples with various particle sizes	[68-70]
Enzyme-linked immunosorbent assay	A plate - based biochemical diagnostic tool for detecting and quantifying ligands, antibodies, and hormones; can assay exosomal membrane proteins and other marker proteins	Time - consuming (several hours to detect exosomes); requires a relatively large sample volume; low sensitivity for exosome detection	[71]
Colorimetric detection	User - friendly operation and straightforward signal readout for point-of-care testing; can be partitioned into AuNP-based assays (using AuNPs as signal transducers/amplifiers with high extinction coefficient and distance - dependent optical properties) and enzyme-H2O2-TMB-based assays (using enzymes to catalyze TMB solution for color signals)	Generally provides binary or semi-quantitative results	[72-74]
Fluorescent detection (including fluorescence spectrophotometry)	High sensitivity and excellent selectivity; can provide insights into exosome origins; can be divided into direct (specific recognition between exosome surface antigens and fluorescent - labeled aptamers or antibodies) and indirect (exosomes triggering fluorescence recovery) modes; can monitor exosome dynamics in real-time	N/A	[73,75-79]
Transmission electron microscopy	High imaging resolution (< 1 nm), well-suited for visualizing nanoparticles and assessing exosome morphology and heterogeneity	Fixation and dehydration steps in sample preparation may affect microvesicle morphology and size distribution	[71,80]
Cryogenic transmission electron microscopy	Eliminates potential effects on exosomes during sample preparation	N/A	[81]
Atomic force microscopy	Allows for sub-nanometer resolution imaging; can simultaneously measure exosome size distribution and map mechanical properties with nanometer accuracy; useful for quantifying and detecting exosome abundance, structure, biomechanics, etc. in tumor samples	N/A	[68,82-84]
Microfluidics (including integration with SPR technology and electrochemical detection)	Decreased reagent consumption, minimized contamination, reduced analysis times, increased throughput, and ease of integration and automation; enhanced exploration of exosome physicochemical and biochemical attributes at the microscale; can be integrated with SPR technology for multiparametric profiling of exosomes; electrochemical detection methods can be rapid and sensitive	Integration with SPR technology requires bulky, intricate instrumentation and is prone to severe interferences	[68,72,85-90]

SPR: Surface plasmon resonance; N/A: Not applicable.