Exosome TSG101 Protein Assay Kit: Usage & Protocol Guide

Exosome TSG101 Protein Assay Kit is a specialized immunoassay tool designed to detect and quantify TSG101, an established endosomal sorting complex required for transport (ESCRT) marker protein, enabling researchers to reliably characterize and normalize exosome preparations.

Product Name

Exosome TSG101 Protein Assay Kit

SKU

E1526236

Target Marker

TSG101 (Tumor Susceptibility Gene 101), a canonical exosome/multivesicular body marker

Assay Principle

Sandwich immunoassay (ELISA-based) for quantitative detection of TSG101 protein in exosome samples

Typical Application

Exosome quality control, normalization of exosome preparations, validation of isolation purity

Sample Types

Isolated exosome fractions from cell culture conditioned media, plasma, serum, urine, and other biofluids (verify with kit insert)

Background: TSG101 as an Exosome Marker

Exosomes are small extracellular vesicles (EVs) typically 30–150 nm in diameter, formed by the inward budding of late endosomes to produce multivesicular bodies (MVBs) that subsequently fuse with the plasma membrane to release their intraluminal vesicles into the extracellular space. They carry a characteristic set of proteins, lipids, and nucleic acids that reflect the biology of their cell of origin and have emerged as important mediators of intercellular communication and promising biomarker reservoirs.

TSG101 (Tumor Susceptibility Gene 101) is a component of the ESCRT-I (Endosomal Sorting Complexes Required for Transport I) complex and is consistently enriched in exosomes relative to other EV subtypes. Its presence is widely used as a positive marker to confirm exosome identity and to semi-quantitatively normalize exosome preparations across experiments. The International Society for Extracellular Vesicles (ISEV) Minimal Information for Studies of Extracellular Vesicles (MISEV) guidelines recommend reporting at least one transmembrane or membrane-anchored protein and one cytosolic protein when characterizing EVs; TSG101 satisfies the cytosolic marker requirement.

Quantifying TSG101 by an immunoassay approach, as provided by this kit, offers a reproducible, plate-reader-based alternative to Western blotting, reducing subjective band interpretation and enabling higher throughput normalization workflows.

Kit Components and Storage

The exact contents of the Exosome TSG101 Protein Assay Kit (E1526236) should always be confirmed against the package insert supplied with each lot. Typical components for an ELISA-format TSG101 assay kit include:

• Pre-coated microplate: Anti-TSG101 capture antibody coated on a 96-well strip plate.
• TSG101 recombinant protein standard: Lyophilized or liquid reference standard for generating a calibration curve.
• Detection antibody: Biotinylated or HRP-conjugated anti-TSG101 detection antibody.
• Streptavidin-HRP conjugate (if detection antibody is biotinylated).
• Assay diluent / sample buffer: Optimized buffer for diluting standards and samples.
• Wash buffer concentrate.
• TMB substrate solution.
• Stop solution.

Storage: Store the kit at 2–8 °C upon receipt. Do not freeze components unless explicitly stated in the kit insert. Equilibrate all reagents to room temperature (18–25 °C) before use. Record the lot number and expiration date; do not use components from different lots interchangeably unless validated.

Note to reviewers: Exact component list and storage conditions must be verified against the official E1526236 product datasheet prior to publication.

Step-by-Step Assay Protocol

The following protocol reflects general best-practice procedures for a sandwich ELISA-based exosome TSG101 assay. Always refer to the official kit insert for lot-specific incubation times, dilution factors, and instrument settings.

1. Sample Preparation

Isolate exosomes from your biological source using an established method (differential ultracentrifugation, size-exclusion chromatography, precipitation, or affinity capture). Resuspend the exosome pellet or eluate in the assay diluent provided. If the sample matrix is complex (e.g., plasma-derived), prepare serial dilutions (recommended starting range: 1:2 to 1:10) to ensure readings fall within the linear range of the standard curve. Lyse exosomes if the kit requires intravesicular access to TSG101 (follow the lysis buffer instructions in the kit insert).

2. Standard Curve Preparation

Reconstitute the lyophilized TSG101 standard according to the kit insert. Prepare a series of at least 6–8 serial dilutions (typically 2-fold) in assay diluent to cover the full dynamic range. Include a blank (assay diluent only) as the zero standard.

3. Plate Setup and Sample Addition

Allow the pre-coated plate to equilibrate to room temperature. Add the appropriate volume of standards, controls, and diluted samples to designated wells in duplicate or triplicate. Seal the plate and incubate at the temperature and duration specified in the kit insert (typically 1–2 h at room temperature or 37 °C).

4. Washing

Aspirate or flick out well contents. Wash each well with the recommended volume of diluted wash buffer (typically 3–5 wash cycles). Blot the inverted plate firmly on absorbent paper after the final wash to remove residual buffer.

5. Detection Antibody Incubation

Add the detection antibody solution to each well. Incubate as specified. Wash as in Step 4.

6. Streptavidin-HRP Incubation (if applicable)

If a biotinylated detection antibody is used, add the Streptavidin-HRP conjugate and incubate per kit instructions. Wash as above.

7. Substrate Development

Add TMB substrate solution to all wells. Incubate in the dark until the desired color development is achieved (monitor visually; typically 10–30 min). Add stop solution to terminate the reaction. Read absorbance at 450 nm (reference wavelength 570 nm or 630 nm) within 30 minutes of stopping.

8. Data Analysis

Plot the standard curve (OD450 vs. TSG101 concentration) using a 4-parameter logistic (4PL) curve fit. Back-calculate sample TSG101 concentrations and apply the appropriate dilution factor. Express results as ng TSG101 per mL of exosome preparation or per µg of total exosome protein, depending on your normalization strategy.

Troubleshooting & Best Practices

Use the following guidance to resolve common issues encountered when running the Exosome TSG101 Protein Assay Kit:

Symptom	Likely Cause	Corrective Action
Signal too low / no signal	Insufficient TSG101 in sample; reagents not equilibrated; inadequate lysis of exosomes	Increase exosome loading amount; ensure room-temperature equilibration; optimize lysis protocol
High background	Insufficient washing; cross-contamination of wells; non-specific binding from complex matrix	Increase wash cycles; use multichannel pipette carefully; dilute sample further
Poor standard curve fit	Improperly prepared standards; pipetting error; degraded standard stock	Prepare fresh dilution series; calibrate pipettes; check standard reconstitution procedure
High CV between replicates	Pipetting inconsistency; temperature gradient across plate	Use electronic multichannel pipette; pre-warm plate uniformly; maintain consistent timing
Sample OD outside standard range	Wrong dilution factor	Re-run with additional dilution steps; ensure linear range coverage

Best Practices:

• Always run samples in at least duplicate wells.
• Include an internal positive control (e.g., a previously characterized exosome preparation) across all plates to monitor run-to-run variability.
• Avoid repeated freeze–thaw cycles of exosome samples, as TSG101 may be degraded by proteolysis.
• Confirm exosome purity by orthogonal methods (e.g., nanoparticle tracking analysis, transmission electron microscopy) alongside TSG101 quantification.
• Document all lot numbers and expiration dates for regulatory-compliant research records.

Interpreting Results and Reporting

TSG101 quantification by this kit provides a standardized, quantitative index of the exosome content in a given preparation. When interpreting and reporting results, consider the following:

Normalization strategies: TSG101 concentration can be expressed per unit volume of biofluid (e.g., ng/mL plasma) or normalized to the number of particles (by nanoparticle tracking analysis) or to total protein content of the EV fraction (µg EV protein). The chosen approach should be consistent across all experiments within a study and should be explicitly stated in the Methods section of any publication.

Contextual benchmarking: Because absolute TSG101 levels vary substantially across cell types, tissues, and biofluid sources, results are most meaningful when compared within the same experimental system. Establish baseline TSG101 levels in your specific sample type before drawing conclusions about enrichment or depletion.

MISEV2018 compliance: To meet ISEV MISEV2018 guidelines, TSG101 data should be accompanied by at least one additional positive EV marker (e.g., CD63, CD9, CD81) and one negative marker to rule out non-EV contaminants (e.g., GM130 for Golgi, calnexin for ER). The TSG101 assay alone is necessary but not sufficient for full EV characterization.

Publication reporting: Report kit name, catalog number (E1526236), lot number, instrument used for plate reading, and the curve-fitting method applied. Include representative standard curves and specify inter-assay and intra-assay CVs.

Frequently asked questions

What sample types are compatible with the Exosome TSG101 Protein Assay Kit?

The kit is designed for use with isolated exosome fractions. Compatible starting materials typically include conditioned cell culture media, plasma, serum, and urine, provided exosomes have been enriched prior to assay. Always verify sample compatibility and optimal dilution ranges with the official kit insert for E1526236, as matrix effects may necessitate sample-specific dilution optimization.

Do I need to lyse exosomes before adding them to the assay plate?

This depends on whether the kit targets intravesicular TSG101 or surface-exposed epitopes. TSG101 is a cytosolic/intraluminal protein and typically requires exosome lysis for optimal immunoassay detection. Consult the kit insert for the recommended lysis protocol and buffer. Incomplete lysis will result in underestimation of TSG101 levels.

How should I normalize TSG101 data across different experiments?

Common normalization approaches include expressing TSG101 per mL of source biofluid, per microgram of total EV protein (determined by BCA or Bradford assay), or per number of particles (determined by NTA). Choose a strategy appropriate to your scientific question and apply it consistently. Including an inter-assay positive control allows correction for plate-to-plate variability.

Can the kit be used to compare exosome yields from different isolation methods?

Yes. TSG101 quantification is a well-established approach for comparing the relative exosome content across preparations obtained by different isolation strategies (e.g., ultracentrifugation vs. size-exclusion chromatography vs. precipitation kits). Ensure that the isolation buffers are compatible with the assay and do not interfere with antibody binding; refer to the kit insert for buffer compatibility information.

What is the expected shelf life and storage condition for this kit?

Generally, ELISA-based kits of this type are stored at 2–8 °C with a shelf life of 6–12 months from the date of manufacture. The exact expiration date is printed on the kit box and individual component labels. Do not use the kit beyond the stated expiration date, and avoid freeze–thaw cycles of liquid reagents unless the insert specifically permits this.

References

1. Théry C, et al. Minimal information for studies of extracellular vesicles 2018 (MISEV2018): a position statement of the International Society for Extracellular Vesicles and update of the MISEV2014 guidelines. Journal of Extracellular Vesicles. 2018;7(1):1535750. doi:10.1080/20013078.2018.1535750
2. Kowal J, et al. Proteomic comparison defines novel markers to characterize heterogeneous populations of extracellular vesicle subtypes. Proceedings of the National Academy of Sciences. 2016;113(8):E968–E977. doi:10.1073/pnas.1521230113
3. Baietti MF, et al. Syndecan–syntenin–ALIX regulates the biogenesis of exosomes. Nature Cell Biology. 2012;14(7):677–685. doi:10.1038/ncb2502
4. Aladdin Scientific. Exosome TSG101 Protein Assay Kit (E1526236) Product Datasheet.

Products are supplied for research and development use only. Not for use in humans, animals, diagnosis, or therapy.