The 7-Day Predictive Engraftment Potential Assay


Download the Potency Assay Flyer



Buy HALO® SC-IPS Assay Kits

Buy HALO® RS Assay Kits

A complete bioluminescence assay to determine stem cell identity, purity and strength (potency) for umbilical cord blood, bone marrow and mobilized peripheral blood.


  • SC = Stem Cell
  • IPS = Identity, Purity, Strength. These are the parameters that the U.S. Food and Drug Administration (FDA) requires for traditional drugs and now biological drugs, such as umbilical cord blood and products for regenerative medicine.
  • Identity defines the "active ingredients" that are responsible for the intended effect or response. For a hematopoietic cell therapy products, only the stem cells are the "active" ingredients and must therefore be identified.
  • Purity defines whether the "active" ingredients are free of impurities and whether these impurities influence the intended effect or response. For hematopoietic cell therapy products, impurities can dilute and mask the identity of the "active" ingredients thereby leading to serious underestimation of the stem cell response. 
  • Strength is considered by the FDA to be equivalent to potency, which predicts the intended effect or response. The strength or potency of the "active" stem cell ingredients predicts stem cell engraftment prior to transplantation and therefore provide the measurement assurance to release the product for use in a patient. 
  • Accurate cell proliferation data provides stem cell potency (strength), identity, purity and quality information in a single assay.
  • For cord blood, bone marrow, mobilized peripheral blood or purified cells (e.g. CD34+, CD133+ etc).
  • Provide the transplantation physician with the most qualified information on the stem cell product in the shortest possible time prior to use. 
  • Establish in-house reference standards (using HALO® RS) that allow the potency ratio (measure of potency) to be determined.
  • Fully compliant with FDA potency assay regulations and guidelines for hematopoietic cell therapy products.
  • HALO® SC-IPS has a Master File with the FDA that can be referenced in an IND or BLA to the FDA. For more information, please contact Preferred Cell Systems™.
  • Fully standardized, verified and validated according to FDA guidelines.
  • Proficiency testing performed and completed during the assay standardization procedure. No additional costly and time-consuming proficiency testing required.
  • Measurement assurance parameters provide proficiency and the trust in your results.
  • Measurement of strength or potency is performed using a modified "Slope-Ratio Concentration-Response Model" standardized by the U.S. Pharmacopeia.
  • Makes "potency" testing using TNC, viability, CD34 or CFU assays obsolete.
  • Suspension Expansion Culture™ (SEC™) Technology provides high accuracy and precision and makes dispensing methylcellulose obsolete.
  • 96-well plate format means smaller sample and reagent volumes with faster setup.
  • Short 7-day incubation to predict engraftment potential.
  • Let the plate reader acquire and calculate results in just 5 minutes or less.
  • Directly compare stem cell potency, identity, purity and quality from different donors and processing procedures over time. 
  • Includes everything needed to culture and measure stem cell potency, identity, purity and quality. Just prepare and add cells.
  • Time-efficient and highly cost-effective.
  • Easy to learn in just 1 day.

Principle of ATP Bioluminescence Cell Proliferation Assays

All ATP bioluminescence assays kits from Preferred Cell Systems™ include an ATP standard(s) and controls.  Performing the ATP standard curve and controls is highly recommended. The controls are used to calibrate the luminescence plate reader and the ATP standard is used to standardize the assay. The values obtained from the standard curve and controls (see diagram below) are then compared to the measurement assurance parameters that are provided in the instruction manual. If the values obtained are within the ranges provided by the measurement assurance parameters, you, the user, have successfully performed the proficiency testing to ensure that you have not only performed the assay correctly, but that the results you obtain can be trusted.

No additional proficiency testing is required if the calibration and standardization procedure is performed. The values you obtain from each calibration and standardization can be logged and used for certification that the assay has been performed correctly and that the results are trustworthy.

Calibration and standardization of an ATP bioluminescence assay from Preferred Cell Systems™ - Measurement Assurance
  • To measure strength or potency, a reference standard (RS) of the same material as the sample is required so that the potency ratio can be determined. The inclusion of a RS to measure potency is an FDA requirement. Universal or global reference standards for cell therapy products are not available. As a result, it is necessary for individual centers to establish their own RS. To accomplish this, a standardized and validated assay platform is required.
  • HALO® RS is used to establish your first in-house RS for a specific tissue. The assay includes a vial of cryopreserved cord blood, peripheral blood or bone marrow cells, at a specific purification, that are used to compare to your own preparation. HALO® RS is only required once to set up your first RS cell preparation. Preparation of all further reference standards can be establish using HALO® SC-IPS by comparing the biological activity of a newly prepared RS with a previous RS. (See below).
  • To measure potency of hematopoietic cellular therapy product samples prior to use in a patient, HALO® SC-IPS is used. The in-house established RS is compared to that of the sample To do this, it is necessary to perform a cell dose response for both the sample and the RS for both stem cell populations. NOTE: A single cell dose tested for a single cell population does not constitute a potency assay. 
  • A minimum 3-point cell dose response for both the sample and the RS is performed for both stem cell populations for which culture reagents are provided in the HALO® SC-IPS assay kit. A dose response is required because the slope of the sample cell dose response compared to that of the RS provides the potency ratio. The potency of a reference standard is always 1.
  • If the potency ratio of the sample is lower than 1, i.e. the RS, the cells being considered will probably not have sufficient potency to ensure engraftment. If the potency ratio is similar to or greater than 1, the sample exhibits a high potency and the probability is also high that engraftment will occur.
  • NOTE: A total nucleated cell (TNC) preparation, a single cell dose, a single cell population that is not a stem cell population and lack of a RS does not constitute a potency assay. In addition, a non-validated assay that lacks measurement assurance parameters also does not consitute a potency assay.   
  • In vitro, hematopoietic multipotential stem cell (SC-GEMM 1)
  • In vitro, lympho-hematopoietic primitive stem cell (SC-HPP 2)
  • Mobilized peripheral blood
  • Umbilical cord blood
  • Bone marrow
  • Purified cells from the above tissues

The recommended cell purity is a mononuclear cell (MNC) fraction or higher purity. A total nucleated cell (TNC) fraction is not recommended as this contains high concentrations of cell impurities, such as red blood cells, neutrophils, platelets and other cells that dilute, mask and severely underestimate, and even inhibit the detection of rare primitive stem cells.

  1. Standardization of the CFU-GM assay using hematopoietic growth factors. J. Hematotherapy:6:191-192 (1997)
  2. Development of a novel assay to evaluate the functional potential of umbilical cord blood progenitors. Transfusion. 48:620-628 (2008).
  3. Potency, Proliferation and Engraftment Potential of Stem Cell Therapeutics: The Relationship between Potency and Clinical Outcome for Hematopoietic Stem Cell Products. J Cell Sci Therapy. (2013).
  4. Detecting primitive hematopoietic stem cells in total nucleated and mononuclear cell fractions from umbilical cord blood segments and units. J Translational Medicine 13:94 (2015)
  5. Improving quality and potency testing for umbilical cord blood: A New Perspective. Stem Cells Translational Medicine. 4:967-973 (2015)
  6. Hematopoietic stem cell potency for cellular therapeutic transplantation. In: Hematopoietic Stem Cells, Ed. Rosana P. Camacho. Published by: InTech Open Access Publisher. ISBN 978-953-307-746-8. (2011).
  7. Measuring the Potency of a Stem Cell Therapeutic. In: Stem Cell Protocols. Methods in Molecular Biology, 1235, Ed. Rich IN. Published by Human Press (2015).
  8. Bioluminescence Potency Measurement of Cellular Therapy Products. In: Cellular Therapy: Principles, Methods, and Regulations, 2nd Edition, Eds. Areman EM and Loper K. Published by AABB.
  9. Present Cord Blood Testing Fails to Determine if the Stem Cells Used for Transplantation are of High Quality and PotencyThe Parents Guide to Cord Blood Foundation
  10. The Difference Between Stem Cell Viability and Potency: A Short Guide for Parent and Patients. The Parents Guide to Cord Blood Foundation

The graphs below demonstrate how umbilical cord blood and bone marrow stem cell potency ratios are determined. There are two primary requisites for measuring potency. The first is the requirement to perform a dose response of the sample. Potency cannot be measured using a single-point determination. The second is to compare the response of the sample with that of a reference standard. Since stem cells are the only cells that provide engraftment potential after transplantation, it is the potency or strength of the stem cells that needs to measured. All other cells are irrelevant. In addition, detecting just a single cell population will not provide the information required to determine engraftment potential. For this reason, the response of two stem cell populations are measured, namely the primitive lympho-hematopoietic stem cell, SC-HPP 2, and the primitive hematopoietic stem cell, SC-GEMM 1. Detecting downstream stem or progenitor cell populations will produce erroneous engraftment potential results. NOTE that potency is a predictive parameter. Potency predicts the dose. In this case, it is meant to predict the stem cell dose that will result in potential for stem cell engraftment. Measurement of potency cannot, therefore, be determined retrospectively.

The black dose response line in each graph represents the in-house umbilical cord blood reference standard. The slope of each cord blood sample dose response curve is compared to that of the reference standard to produce the potency ratio. The potency ratio is the measurement of potency. A sample with potency ratio lower than 1 (the potency of the reference standard) should not be used. A sample with a potency ration similar or greater than 1 can be used. Both stem cell populations should display a potency ration similar or greater than 1 to be used.

The name HALO® SC-IPS, indicates that the assay not only measures strength (S) or potency, but also identity and purity of the stem cells in the sample. The steepness of the stem cell dose response curve compared to that in other samples is a direct indication of the primitiveness and, therefore, the identity (I) of the stem cells in that sample. The steeper the curve, the more primitive the stem cells. In addition, if the purity (P) of the stem cells in a TNC, MNC or CD34+ sample were compared, the slope of the dose response curve would also determine the purity; the great the slope, the better the purity and, therefore, the more accurate the potency determination. Thus, the slope and therefore the purity of the cells would be: CD34+ > MNC > TNC. It is for this reason why the TNC fraction of cord blood should not and cannot be used to measure potency; it contains too many cellular impurities that mask the true potency of the sample.

Measuring Umbilical Cord Blood Stem Cell Potency using HALO SC-IPS

Human Bone Marrow Stem Cell Potency Measured Using HALO SC-IPS

For Research Use Only. Not for clinical diagnostic use.

Luminescence or multimode plate reader capable of measuring "glow" luminescence.

HALO®-RS Kit Contents:

  • Vial of cryopreserved reference standard umbilical cord blood, mobilized peripheral blood, bone marrow mononuclear cells (MNC) or purified cells (CD34 ) from the respective tissue

  • HALO® Master Mixes for both SC-HPP 2 and SC-GEMM 1 stem cell populations
  • ATP standards
  • ATP controls
  • ATP Enumeration Reagent
  • Sterile, 96-well plate(s)
  • Non-sterile, 96-well plate(s)
  • Sterile, adhesive foil covers

HALO® SC-IPS Kit Contents

  • HALO® SC-IPS Master Mixes for SC-HPP 2 and SC-GEMM 1 stem cell populations
  • ATP standard
  • ATP controls
  • ATP Enumeration Reagent
  • Sterile, 96-well plates
  • Non-sterile, 96-well plates
  • Sterile, adhesive foil covers

HALO® RS and SC-IPS QuickGuides
HALO® RS to Establish In-House Reference Standards for use with HALO® SC-IPS Potency Assays

HALO® SC-IPS: The Stem Cell Identity, Purity and Strength (Potency) Assay for Hematopoietic Stem Cell Therapy Products

Download the HALO® SC-IPS / HALO® RS Technical Manual
Download the ATP Optimization Kit Protocol for First-Time Users
Download the Luminometer Setup and Conversion of RLU to ATP Protocol Download Certificate of Analysis (CoAs) for ATP Enumeration Reagent (ATP-ER)
Download Certificate of Analysis for ATP Stanadrds
Download Certificate of Analysis for ATP Controls
Download Certificate of Analysis of ATP Reconstitution Reagent
Download Certificate of Analysis for Sterile 96-Well Plates
Download Certificate of Analysis for Non-Sterile, 96-Well Plates
Download Certificate of Analysis for Sealing Films
Download Certificate of Analysis for IMDM

When ordering HALO® RS and/or HALO® SC-IPS, simply click on the Catalog Number in the table below and you will be taken directly to the desired product.

HALO® RS Assays Kits Available to Establish
an In-House Reference Standard (RSa)
Populations Measured(*) Catalog Number Cell Type(#) No. of Plates/Kit Format
SC-HPP 2 and SC-GEMM 1 K2-PRS-1BM Bone marrow 1 Low serum
SC-HPP 2 and SC-GEMM 1 K2-PRS-1BM34 Bone Marrow CD34 1 Low serum
SC-HPP 2 and SC-GEMM 1 K2-PRS-1CB Cord blood 1 Low serum
SC-HPP 2 and SC-GEMM 1 K2-PRS-1CB34 Cord Blood CD34 1 Low serum
SC-HPP 2 and SC-GEMM 1 K2-PRS-1mPB Mobilized peripheral blood 1 Low serum
SC-HPP 2 and SC-GEMM 1 K2-PRS-1mPB34 Mobilized peripheral blood CD34 1 Low serum
SC-HPP 2 and SC-GEMM 1 K2SF-PRS-1BM Bone marrow 1 Serum-Free
SC-HPP 2 and SC-GEMM 1 K2SF-PRS-1BM34 Bone Marrow CD34 1 Serum-Free
SC-HPP 2 and SC-GEMM 1 K2SF-PRS-1CB Cord blood 1 Serum-Free
SC-HPP 2 and SC-GEMM 1 K2SF-PRS-1CB34 Cord Blood CD34 1 Serum-Free
SC-HPP 2 and SC-GEMM 1 K2SF-PRS-1mPB Mobilized peripheral blood 1 Serum-Free
SC-HPP 2 and SC-GEMM 1 K2SF-PRS-1mPB34 Mobilized peripheral blood CD34 1 Serum-Free

(a): Prior to measuring potency, a reference standard (RS) should be established to which the sample can be compared and the potency ratio determined. 

(#): HALO® RS assay kits are also available to help establish reference standards for purified CD34 cells from each of the 3 tissues. Please go to the online catalog or contact Preferred Cell Systems™ for more information.

(*): A minimum of 2 stem cell populations must be measured. Potency cannot be determined using a single cell population. 


HALO® SC-IPS Assays Kits Available to Determine
Identity, Purity and Strength (Potency)
Populations Measured (*) Catalog Number Cell Type No. of Plates/Kit Format
SC-HPP 2 and SC-GEMM 1 K2-PQR-1 Any hematopoietic tissue(1,2) 1 Low serum
SC-HPP 2 and SC-GEMM 1 K2SF-PQR-1 Any hematopoietic tissue(1,2) 1 Serum-Free

(*): A minimum of 2 stem cell populations must be measured. Potency cannot be determined using a single cell population.

(1): Includes mononuclear cells (MNC) from umbilical cord blood, mobilized peripheral blood, bone marrow or purified cells (e.g. CD34 or CD133 ) from these tissues.

(2): A RS should always be performed when an unknown sample is measured. If more than 1 sample is to be measured, a single RS of the same cell type can be used to compare with all samples performed on the same day.

Bulk assays are available upon request. Please contact Preferred Cell Systems™