Human CTSD (Cathepsin D) ELISA Kit (HUES01825)

This ELISA kit uses Sandwich-ELISA as the method. The micro ELISA plate provided in this kit has been pre-coated with an antibody specific to Human CTSD. Standards or samples are added to the appropriate micro ELISA plate wells and combined with the specific antibody. Then a biotinylated detection antibody specific for Human CTSD and Avidin-Horseradish Peroxidase (HRP) conjugate are added to each micro plate well successively and incubated. Free components are washed away. The substrate solution is added to each well. Only those wells that contain Human CTSD, biotinylated detection antibody and Avidin-HRP conjugate will appear blue in color. The enzyme-substrate reaction is terminated by adding Stop Solution and the color turns yellow. The optical density (OD) is measured spectrophotometrically at a wavelength of 450 nm ± 2 nm. The OD value is proportional to the concentration of Human CTSD. The concentration of Human CTSD in samples can be calculated by comparing the OD of the samples to the standard curve.

As the OD values of the standard curve may vary according to the conditions of the actual assay performance (e. g. operator, pipetting technique, washing technique or temperature effects), the operator should establish a standard curve for each test. Typical standard curve and data is provided below for reference only.

Precision

Intra-assay Precision (Precision within an assay): 3 samples with low, mid range and high level Human CTSD were tested 20 times on one plate, respectively.

Inter-assay Precision (Precision between assays): 3 samples with low, mid range and high level Human CTSD were tested on 3 different plates, 20 replicates in each plate.

Recovery

The recovery of Human CTSD spiked at three different levels in samples throughout the range of the assay was evaluated in various matrices.

Linearity

Samples were spiked with high concentrations of Human CTSD and diluted with Reference Standard & Sample Diluent to produce samples with values within the range of the assay.

An unopened kit can be stored at 4°C for 1 month. If the kit is not used within 1 month, store the items separately according to the following conditions once the kit is received.

1. Set standard, test sample and control (zero) wells on the pre-coated plate and record theirpositions. It is recommended to measure each standard and sample in duplicate. Note: addall solutions to the bottom of the plate wells while avoiding contact with the well walls. Ensuresolutions do not foam when adding to the wells.
2. Aliquot 100 µL of standard solutions into the standard wells.
3. Add 100 µL of Sample / Standard dilution buffer into the control (zero) well.
4. Add 100 µL of properly diluted sample (serum, plasma, tissue homogenates and otherbiological fluids) into test sample wells.
5. Cover the plate with the sealer provided in the kit and incubate for 90 min at 37 °C.
6. Aspirate the liquid from each well, do not wash. Immediately add 100 µL of BiotinylatedDetection Ab working solution to each well. Cover the plate with a plate seal and gently mix. Incubate for 1 hour at 37 °C.
7. Aspirate or decant the solution from the plate and add 350 µL of wash buffer to each welland incubate for 1-2 minutes at room temperature. Aspirate the solution from each well andclap the plate on absorbent filter paper to dry. Repeat this process 3 times. Note: a microplatewasher can be used in this step and other wash steps.
8. Add 100 µL of HRP Conjugate working solution to each well. Cover with a plate seal andincubate for 30 min at 37 °C.
9. Aspirate or decant the solution from each well. Repeat the wash process for five times asconducted in step 7.
10. Add 90 µL of Substrate Reagent to each well. Cover with a new plate seal and incubate forapproximately 15 min at 37 °C. Protect the plate from light. Note: the reaction time can beshortened or extended according to the actual color change, but not by more than 30min.
11. Add 50 µL of Stop Solution to each well. Note: Adding the stop solution should be done inthe same order as the substrate solution.
12. Determine the optical density (OD value) of each well immediately with a microplate readerset at 450 nm.