FT3 ELISA Kit

Sample Collection, Preparation, and Storage

1. Serum: After placing whole blood samples at room temperature for 2 hours or at 4°C overnight, centrifuge at 1000×g for 20 minutes. Remove the supernatant for testing. Blood collection tubes should be disposable, pyrogen-free, and endotoxin-free. Store at -20°C or -80°C and avoid repeated freezing and thawing.

2. Plasma: Within 30 minutes of collection, centrifuge at 1000×g for 15 minutes at 2-8°C. Remove the supernatant for testing. EDTA-Na2 is recommended as an anticoagulant. Avoid using samples with hemolysis or hyperlipidemia. Store at -20°C or -80°C and avoid repeated freezing and thawing. 3. Tissue Homogenization: Take an appropriate amount of tissue and wash it in pre-chilled PBS (0.01M, pH 7.0-7.2) to remove blood (lysed red blood cells in the homogenate will affect the measurement results). After weighing, mince the tissue and mix it with the appropriate volume of PBS (generally a 1:9 weight-to-volume ratio; the specific volume can be adjusted according to experimental needs and recorded. It is recommended to add protease inhibitors to the PBS). Pour the mixture into a glass homogenizer and grind thoroughly on ice. To further lyse tissue cells, the homogenate can be sonicated or freeze-thawed repeatedly (keep the sonication in an ice bath and repeat the freeze-thaw cycle twice). Finally, centrifuge the homogenate at 5000 × g for 5-10 minutes. Remove the supernatant for analysis. (The tissue homogenate should also be assayed for protein concentration to obtain a more accurate concentration of the test substance per milligram of protein.) 4. Cell Culture Supernatant: Centrifuge the cell supernatant at 1000 × g for 20 minutes to remove impurities and cell debris. Remove the supernatant for testing and store at -20°C or -80°C, but avoid repeated freezing and thawing.

5. Urine: Collect the first morning urine (midstream) or 24-hour urine collection. Centrifuge at 2000×g for 15 minutes, collect the supernatant, and store the sample at -20°C. Avoid repeated freezing and thawing.

6. Saliva: Collect the sample using a saliva sample collection tube, then centrifuge at 1000×g for 15 minutes at 2-8°C. Remove the supernatant for testing, or aliquot and store at -20°C. Avoid repeated freezing and thawing.

7. Other biological samples: Centrifuge at 1000×g for 20 minutes, collect the supernatant, and store at -20°C. Avoid repeated freezing and thawing.

Precautions

1. The sample should be clear and transparent, and suspended matter should be removed by centrifugation. Hemolysis of the sample will affect the results, so hemolyzed samples should not be used.
2. If the sample is tested within 1 week after collection, it can be stored at 4°C. If testing cannot be done promptly, please aliquot the sample into a single-use amount and freeze at -20°C (for testing within 1 month) or -80°C (for testing within 3-6 months). Avoid repeated freeze-thaw cycles. Please bring the sample to room temperature before the experiment.
3. If the concentration of the test substance in your sample is higher than the highest value of the standard, please dilute it appropriately based on the actual situation (it is recommended to conduct a preliminary experiment to determine the dilution factor).

Sample Dilution Principles

If your test sample needs to be diluted, the general dilution principles are as follows:

1. 50-fold dilution: One-step dilution. Add 5 μL of sample to 245 μL of standard and sample diluent for a 50-fold dilution.
2. 100-fold dilution: One-step dilution. Add 5 μL of sample to 495 μL of standard and sample diluent for a 100-fold dilution.
3. 1000-fold dilution: Two-step dilution. Add 5 μL of sample to 95 μL of Standard & Sample Diluent for a 20-fold dilution. Then add 5 μL of the 20-fold diluted sample to 245 μL of Standard & Sample Diluent for a 50-fold dilution, for a total dilution of 1,000. 4. 100,000-fold dilution: Three-step dilution. Add 5 μL of sample to 195 μL of Standard & Sample Diluent for a 40-fold dilution. Then, add 5 μL of the 40-fold diluted sample to 245 μL of Standard & Sample Diluent for a 50-fold dilution. Finally, add 5 μL of the 2,000-fold diluted sample to 245 μL of Standard & Sample Diluent for a 50-fold dilution, for a total dilution of 100,000-fold. 5. For each dilution step, use at least 3 μL of sample volume, and do not exceed a 100-fold dilution. Excessively small sample volumes can lead to greater errors during mixing. Ensure thorough mixing at each dilution step to avoid foaming. 6. For very high dilution ratios, dilute with PBS first, and then use the Standard & Sample Diluent provided in the kit as the final step.

Preparation Before Assay

1. Remove the test kit from the refrigerator 30 minutes in advance and equilibrate to room temperature.
2. Dilute 25 μg/mL of concentrated wash buffer to 1 μg/mL of working solution with double-distilled water. Return any unused portion to 4°C.
3. Standard: Add 1.0 mL of Universal Diluent for Standards & Samples to the lyophilized standard. Tighten the cap and let stand for 10 minutes to allow for full dissolution. Gently mix to achieve a concentration of 100 pg/mL. Serially dilute the standard to 100 pg/mL, 50 pg/mL, 25 pg/mL, 12.5 pg/mL, 6.25 pg/mL, 3.13 pg/mL, and 1.57 pg/mL. The standard diluent (0 pg/mL) serves as a blank well. Prepare the required amount of standard for use. It is recommended to add the prepared standard within 15 minutes. It is not recommended to leave it for an extended period.

1. Biotin Conjugate Working Solution (1x): Centrifuge before opening the bottle. Dilute with Biotin Conjugate Diluent immediately before use. Prepare the pre-calculated total volume for each experiment (50 μL per well). Add 0.1-0.2 mL more than the actual volume. Prepare a 10 μL biotin conjugate solution with 990 μL biotin conjugate diluent, mix gently, and prepare within one hour before use.
2. Streptomycin-Horseradish Peroxidase Conjugate Working Solution (1x): Centrifuge before opening the bottle. Dilute with enzyme conjugate diluent immediately before use. Prepare the solution based on the pre-calculated total volume required for each experiment (100 μL per well). Add 0.1-0.2 mL more. Prepare a 10 μL enzyme conjugate solution with 990 μL enzyme conjugate diluent, mix gently, and prepare within one hour before use.
3. TMB Substrate - Pipette the required amount of solution. Do not return any remaining solution to the reagent bottle.

Preparation

1. Equilibrate all materials and prepared reagents to room temperature before use. Before use, mix all reagents thoroughly, taking care not to produce any foam.
2. The user should calculate the number of samples that may be used in the entire test. Please reserve enough samples in advance.
3. Please estimate the concentration before measurement. If these values are not within the range of the standard curve, the user must determine the optimal sample dilution for their specific experiment.

Operation steps

1. Before starting the experiment, all reagents should be equilibrated to room temperature and all reagents should be prepared in advance. When diluting reagents or samples, they must be mixed thoroughly and try to avoid foaming during mixing. If the sample concentration is too high, dilute it with sample diluent so that the sample is within the detection range of the kit.
2. Sample addition: Set up standard wells and sample wells to be tested respectively. Add 50 μL of the standard or sample to be tested, being careful not to create bubbles. Pour the sample onto the bottom of the ELISA plate well, avoiding contact with the sides. Next, add 50 μL of biotin conjugate (1 x) to each well and gently shake to mix. Cover the plate or seal the plate with film and incubate at 37°C for 1 hour.
3. To ensure the validity of the experimental results, use a fresh standard solution for each experiment.
4. After the 1-hour incubation, discard the liquid in the wells, spin dry, and wash the plate three times, adding 200 μL of wash buffer (1 x) to each well, soaking for 1-2 minutes each time, and spin dry.
5. Next, add 100 μL of streptavidin-HRP (1 x) to each well and gently shake to mix. Cover the plate or seal the plate with film and incubate at 37°C for 1 hour. 6. Discard the liquid in the wells, spin dry, and wash the plate five times, adding 200 μL of wash solution (1 x) to each well, soaking for 1-2 minutes each time, and spin dry. 7. Add 90 μL of TMB colorimetric reagent to each well in sequence and develop the color at 37°C in the dark for 20 minutes (this time may be shortened or extended depending on the actual color development, but should not exceed 30 minutes). 8. Add 50 μL of stop solution to each well in sequence to terminate the reaction (the blue color will immediately turn yellow). The stop solution should be added in the same order as the substrate solution. To ensure accurate experimental results, add the stop solution as soon as possible after the substrate reaction time expires. 9. Measure the optical density (OD) of each well in sequence using a microplate reader at a wavelength of 450 nm. Measure within 5 minutes after adding the stop solution. 10. *Samples may require dilution. Please refer to the sample processing section. Calculation of Results 1. The OD values of the competition standards and samples can be directly substituted into the calculation. If replicates are used, the average value should be used for calculation. 2. For ease of calculation, although concentration is the independent variable and OD value is the dependent variable, the graphs use the OD value of the standard as the horizontal axis (X-axis) and the concentration of the standard as the vertical axis (Y-axis). To ensure intuitiveness of the experimental results, the graphs present raw data rather than logarithmic values. Due to differences in experimental operating conditions (such as operator, pipetting technique, plate washing technique, and temperature), the OD values of the standard curve will vary. The provided standard curve is for reference only; experimenters should establish a standard curve based on their own experiments. The sample concentration can be calculated from the OD value of the sample used on the standard curve. This value is then multiplied by the dilution factor to obtain the actual sample concentration. It is recommended to use professional curve drawing software, such as Curve Expert.

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Precision

Intraplate precision (precision within an assay): CV%

Three samples of known concentrations were tested 20 times on each ELISA plate to assess intraplate precision.

Interplate precision (precision between assay plates): CV%

Three samples of known concentrations were tested 40 times on each of three different ELISA plates to assess assay precision.

? Recovery rate

Recovery rate experiments were performed by adding known concentrations of fT3 to different samples to obtain the recovery rate range and average recovery rate.

Linearity

The samples spiked with fT3 were diluted 2-fold, 4-fold, 8-fold, and 16-fold to perform recovery experiments, and the recovery rate range was obtained. style="border-collapse: collapse;" border="1">

Sample type

1:2

1:4

1:8

1:16

Serum (n=5)

85-94%

87-96%

82-95%

82-93%

EDTA?Plasma (n=5)

85-98%

88-104%

86-102%

79-93%

heparin plasma (n=5)

85-92%

80-96%

87-98%

95-102%

Sensitivity 0.51 pg/mL

Species Reactivity General

Theory This kit utilizes a competitive assay. Purified fT3 is coated on a microplate to form a solid-phase support. Samples or standards, followed by biotin-labeled antibodies, are sequentially added to the fT3-coated wells. Streptavidin-HRP is then added after the reaction. After thorough washing, the reaction is developed using the substrate TMB. TMB converts to blue under the catalysis of peroxidase and to yellow under the action of acid. The intensity of the color is inversely correlated with the fT3 content in the sample. The absorbance (OD) is measured at 450 nm using a microplate reader to calculate the sample concentration.

Synonym fT3(Free Triiodothyronine) ELISA Kit

Detection Type It can detect fT3 in samples and does not cross-react with other related substances.

Composition

General Notes 1. Before using the kit, ensure that all components are dissolved and mixed thoroughly. Discard any unused standard after reconstitution. 2. Concentrated biotin conjugates and concentrated enzyme conjugates are relatively small and may disperse throughout the tube during transportation. Centrifuge at 1000 × g for 1 minute before use to allow any liquid on the tube walls or cap to settle to the bottom. Mix the solution by carefully pipetting 4-5 times before use. Prepare the standard, biotin conjugate working solution, and enzyme conjugate working solution according to the required volume and use the corresponding diluents. Do not mix them. 3. Concentrated wash solution may crystallize after removal from the refrigerator. This is normal. Dissolve the crystals completely in a water bath or incubator before preparing the wash solution (do not heat above 40°C). The wash solution should be at room temperature before use. 4. Sample addition should be rapid, ideally within 10 minutes for each addition. To ensure experimental accuracy, replicate wells are recommended. When pipetting reagents, maintain a consistent order of addition from one well to the next. This will ensure consistent incubation times for all wells. 5. During the wash process, any remaining wash solution in the reaction wells should be patted dry on absorbent paper. Do not place filter paper directly into the reaction wells to absorb water. Before reading, be sure to remove any remaining liquid and fingerprints from the bottom of the wells to avoid affecting the microplate reader reading. 6. The chromogen TMB should be protected from direct sunlight during storage and use. After adding the substrate, carefully observe the color changes in the reaction wells. If a gradient is already evident, terminate the reaction early to avoid excessive color changes that may affect the microplate reader reading. 7. All test tubes and reagents used in the experiment are disposable. Reuse is strictly prohibited, as this will affect the experimental results. 8. Wear a lab coat and latex gloves for proper protection during the experiment, especially when testing blood or other body fluid samples. Please follow the national biological laboratory safety regulations. 9. Kit components from different batches must not be mixed (except for the wash solution and the reaction stop solution). 10. The enzyme label strips in the kit are detachable. Please use them in batches according to experimental needs.

Storage Temp.Unopened test kit, stored at 4°C, has a shelf life of 6 months.

Test Range 1.56-100 pg/mL