Unlike most other non-radioactive labeling technologies, DELFIA® technology is applicable to various types of tracer technologies with different labeling procedures and targets. Biodistribution is one example of an area where radioactive labels with suitable image analysis (PET, SPECT) have been difficult to replace.
Using DELFIA, a typical biodistribution study (pharmacokinetics) can be performed with Europium- (or another DELFIA lanthanide-) labeled target, which is injected into the test animal for biodistribution. Distribution is followed by sampling (blood, urine, feces, or tissue homogenates) for fluorescence. Alternatively, the target molecule is injected and biodistribution is followed by analyzing target organs or body fluids via a DELFIA immunoassay.
Compared to radioactive labels, such as 125I, the DELFIA Europium assay avoids the use of radioactivity, offers longer reagent shelf-life, and can be multiplexed. It also has similar or better sensitivity when compared to radioactive biodistribution assays (Neville et al., 2000).
What do I need to run this assay?
- Microplate (we recommend white, clear, or DELFIA yellow microplates, as appropriate for your assay design)
- Europium-labeled reagent, DTPA chelate
- DELFIA Inducer (or another DELFIA dissociating reagent, as appropriate)
- A TRF-capable plate reader
- Plate shaker (we recommend our DELFIA Plateshake)
Products and catalog numbers
View a listing of DELFIA products with catalog numbers.
- Labeling of target molecules
- Different chelates have been used in biodistribution, including DDTA, DTPA, or DOTA through amide linkage or as a tetracid. Due to the comparatively-limited stability of DDTA and the low dissociation rate of DOTA, we recommend using a DTPA chelate for labeling. You can view our Label your own DELFIA reagents page for more information on labeling reagents and protocols.
- If a more-stable chelate is needed, detection should be performed after a short acid treatment (2 M HCl) before adding DELFIA Inducer or DELFIA Enhancement solution.
- Living cells (such as stem cells) can be labeled very simply with a Europium ion (e.g. using Eu citrate, Figure 1). The membrane-embedded Europium phosphate will stay inside cell membranes as long as the cells are intact, and can be measured with DELFIA as reported for Europium nanobeads with mass spectrometry.
- Hale, S.L., Daí, W., Dow, J.S. & Kloner, R.A. Mesenchymal Stem Cell Administration at Coronary Artery Reperfusion in the Rat by Two Delivery Routes: A Quantitative Assessment. Life Sci 83: 511-15 (2008). Link
Figure 1. A simple protocol for labeling living cells with a Europium ion. Image from van der Kamp KWHJ, van Oeveren W. A sensitive non-radioisotopic in vitro method for platelet adherence studies. In 19th Annual Meeting of the Society for Biomaterials, April 1993, Birmingham, AL, USA.
Analyzing your samples
- When lanthanides are used as tracers, analysis of biodistribution is generally performed by analyzing body fluid in suitable dilution (1/100) in DELFIA Inducer or DELFIA Enhancement solution prior to reading. If tissues are to be analyzed, they need to be homogenized and the suspension diluted into Enhancement solution or Inducer. To avoid excessive biological material and pH effects, you will need to use a high enough dilution (1/100) in the enhancement process.
Powerpoint presentation: Single and dual label biodistribution studies with Eu/Tb-labeled peptides by Karyon Ltd, Helsinki, Finland
Custom labeling and custom assay development at PerkinElmer
PerkinElmer offers custom labeling services as well as custom assay development. If you are interested in having your biomolecule custom-labeled, or in custom assay development, please contact our custom teams: