Exosome quantitation assays and ELISA kits for AChE and tetraspanin-based EV measurement

You can measure extracellular vesicles by acetylcholinesterase (AChE) activity on a standard plate reader, without a nanoparticle tracking instrument. AChE-based assays estimate the enzymatic activity of your EVs. Calibration against particle standards, within the validated range, gives you kit-calibrated particle equivalents in compatible samples.

AChE is not a universal EV marker, and its activity does not directly equal particle number across all sample types. Pairing it with orthogonal methods (NTA/TRPS, protein markers, contaminant analysis) supports publication-quality quantification. Fluorescent substrate variants offer higher sensitivity for your low-concentration samples such as urine or CSF.

Surface-marker exosome ELISA kits use a different principle. Sandwich capture assays immobilise EVs on tetraspanin-coated plates, then a detection antibody measures the bound particles. Tetraspanin capture-surface variants allow selective quantification of EV subpopulations by surface marker expression. Formats span plate-reader enzymatic assays, fluorescence assays, and sandwich ELISA kits, for your workflow.

Choose your exosome quantification assay by detection principle and sensitivity needs.

1. Detection principle. Enzymatic activity (AChE) suits your routine EV quantification on any absorbance plate reader, with no specialist equipment required. Fluorescence substrate assays give higher sensitivity for your low particle concentrations in dilute biofluids. Surface-marker sandwich ELISA gives marker-specific quantification that distinguishes EV subpopulations by tetraspanin expression.

2. Absolute vs relative. Relative particle equivalents come from enzymatic assays without reference standards, useful for your inter-sample comparison. Calibrated particle equivalents per ml come from adding calibration standards to the enzymatic assay. This gives you quantitative results within the validated range of the kit. These values represent kit-calibrated equivalents rather than absolute particle counts, unless verified against an independent particle sizing method. Surface ELISA gives relative AU values unless calibrated against a known particle standard.

3. Instrument. An absorbance plate reader suits enzymatic AChE assays. A fluorescence plate reader suits fluorescent substrate assays, and a standard ELISA plate reader at 450 nm suits your sandwich ELISA kit.

4. Marker selectivity. For your total EV population, enzymatic or fluorescence assays apply. For tetraspanin-positive EVs only, CD9 or an alternative capture sandwich ELISA kit gives subpopulation-specific counts.