| Usage |
I. Specimen Collection, Preparation, and Storage
- 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.
- 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 to avoid hemolysis or high-lipidemia samples. Store at -20°C or -80°C and avoid repeated freezing and thawing. 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). Pulse 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. 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. 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. Saliva: Collect the sample using a saliva 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. Other biological samples: Centrifuge at 1000×g for 20 minutes, remove the supernatant, and store at -20°C. Avoid repeated freezing and thawing.
Note:
- Samples should be clear and transparent, and suspended matter should be removed by centrifugation. Hemolysis of the sample can affect the results, so hemolyzed samples should not be used.
Samples can be stored at 4°C if tested within one week of collection. If testing cannot be performed promptly, aliquot the sample into single-use portions and freeze at -20°C (for testing within one month) or -80°C (for testing within three to six months). Avoid repeated freeze-thaw cycles. Bring samples to room temperature before experimenting.
If the concentration of the test substance in your sample is higher than the highest concentration of the standard, dilute it appropriately based on the actual concentration (it is recommended to conduct a pilot experiment to determine the dilution factor).
II.Pre-Test Preparation
- Remove the test kit from the refrigerator 30 minutes in advance and equilibrate to room temperature. Dilute 25 μg/mL of concentrated wash buffer to 1 μg/mL of working solution with double-distilled water. Return any unused solution to 4°C. Standards: Add 1.0 mL of Universal Standard & Sample Diluent to the lyophilized standard. Tighten the cap and let stand for 10 minutes to fully dissolve. Then gently mix (concentration: 2000 pg/mL). Subsequently, serially dilute the standard to 2000 pg/mL, 1000 pg/mL, 500 pg/mL, 250 pg/mL, 125 pg/mL, 62.5 pg/mL, and 31.25 pg/mL. Use the standard diluent (0 pg/mL) as a blank well. Prepare the required amount of standard and set aside. It is recommended that the prepared standard be added to the sample within 15 minutes; it is not recommended to allow the sample to sit for extended periods. Biotinylated Antibody Working Solution: Before use, calculate the required volume (100 μL/well; add 100-200 μL more). 15 minutes before use, dilute the concentrated biotinylated antibody (1:100) with Biotinylated Antibody Diluent to the working concentration for use the same day. For dilution, add 1 μL of concentrated biotinylated antibody to 99 μL of Biotinylated Antibody Diluent and mix thoroughly using a pipette. Enzyme Conjugate Working Solution: Before use, calculate the required volume for each experiment (assuming 100 μL/well; prepare 100-200 μL more). 15 minutes before use, dilute the concentrated HRP enzyme conjugate (1:100) with enzyme conjugate diluent to the working concentration for use that day. To achieve this dilution, add 1 μL of concentrated enzyme conjugate to 99 μL of enzyme conjugate diluent and mix thoroughly with a pipette. TMB Substrate: Pipette the required volume of solution; do not return any remaining solution to the reagent bottle. Note: Ensure all kit components are dissolved and mixed thoroughly before use. Discard any remaining standard after reconstitution. Concentrated biotinylated antibodies and concentrated enzyme conjugates are relatively small and may disperse throughout the tube during shipping. Before use, centrifuge at 1000 × g for 1 minute 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, biotinylated antibody working solution, and enzyme conjugate working solution according to the required volume and use the corresponding diluents. Do not mix them. Concentrated wash buffer may crystallize after removal from the refrigerator. This is normal. Dissolve the crystals completely in a water bath or incubator before preparing the wash buffer (do not heat above 40°C). The wash buffer should be at room temperature before use. Samples should be added quickly, ideally within 10 minutes for each addition. To ensure accuracy, replicate wells are recommended. When pipetting reagents, maintain a consistent order of addition from well to well. This will ensure consistent incubation times for all wells. 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. The color developer, TMB, should be protected from direct sunlight during storage and use. After adding the substrate, carefully observe the color change in the reaction wells. If a gradient is already evident, terminate the reaction early to prevent excessive color from affecting the microplate reader reading. The test tubes and reagents used in the experiment are disposable. Reuse is strictly prohibited, as this will affect the experimental results. 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. Components from different batches of the kit should not be mixed (except for the wash solution and the reaction stop solution). The enzyme labeling strips in the kit are removable; please use them in batches according to your experimental needs.
III.Procedure
- Before beginning the experiment, all reagents should be equilibrated to room temperature. Prepare all reagents in advance. When diluting reagents or samples, mix thoroughly and avoid foaming as much as possible. If the sample concentration is too high, dilute it with sample diluent to bring it within the detection range of the kit.
- Add 100 μL of the standard or sample to be tested (if the sample requires dilution, refer to the sample dilution guidelines for dilution methods). Be careful not to create bubbles. Add the sample to the bottom of the ELISA plate well, avoiding contact with the well walls. Gently shake to mix. Cover the plate or cover with film and incubate at 37°C for 80 minutes. To ensure the validity of the experimental results, use a fresh standard solution for each experiment.
- Discard the liquid in the wells, spin dry, and wash the plate three times. Wash each well with 200 μL of wash buffer, soak for 1-2 minutes, and discard the liquid from the plate (or wash the plate using a plate washer). After the final wash, pat the plate dry on absorbent paper. Add 100 μL of biotinylated antibody working solution to each well (can be prepared 15 minutes in advance), cover the plate with film, and incubate at 37°C for 50 minutes. Discard the liquid from the wells and wash the plate three times. Wash each well with 200 μL of wash buffer, soak for 1-2 minutes, and discard the liquid from the plate (or wash the plate using a plate washer). After the final wash, pat the plate dry on absorbent paper. Add 100 μL of enzyme conjugate working solution to each well (can be prepared 15 minutes in advance), incubate at 37°C for 50 minutes. Discard the liquid from the wells and wash the plate five times. Wash each well with 200 μL of wash buffer, soak for 1-2 minutes, and shake off any remaining liquid from the plate (or wash using a plate washer). After the final wash, pat the plate dry on absorbent paper. Add 90 μL of TMB chromogenic substrate solution to each well and incubate at 37°C in the dark for 20 minutes (shorten or extend the time depending on the color development, but do not exceed 30 minutes). Add 50 μL of stop solution to each well to terminate the reaction (the blue color will immediately turn yellow). The stop solution should be added in the same order as the color developer. To ensure accurate results, add the stop solution as soon as possible after the substrate reaction time expires. Immediately measure the optical density (OD) of each well using a microplate reader at a wavelength of 450 nm. The instrument should be preheated and the assay program set before use.
Result Calculation
- The OD value of the blank well should be subtracted from the OD value of each standard and sample. If replicate wells are used, the average value should be used for calculation.
- 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). Also, 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 used sample 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.
Concentration(pg/mL) |
OD |
Corrected OD |
2000 |
2.128 |
2.026 |
1000 |
1.517 |
1.415 |
500 |
1.136 |
1.034 |
250 |
0.828 |
0.726 |
125 |
0.517 |
0.415 |
62.5 |
0.357 |
0.255 |
31.25 |
0.216 |
0.114 |
0 |
0.102 |
0.000 |
Note: This picture is for reference only
Precision
Intra-assay precision (within-assay precision): CV% <8%
Three samples of known concentrations were tested 20 times on a single ELISA plate to assess intra-assay precision.
Inter-assay precision (between-assay precision): CV% <10%
Three samples of known concentrations were tested 40 times on three different ELISA plates to assess inter-assay precision.
Recovery
Recovery experiments were performed by spiking different samples with known concentrations of rat TNNI3 to determine the range and average recovery.
Sample type |
Recovery range |
Average recovery |
Serum(n=5) |
83-101% |
87% |
EDTA plasma (n=5) |
86-94% |
90% |
heparin plasma(n=5) |
81-93% |
87% |
Linearity
The samples spiked with rat TNNI3 were diluted 2-fold, 4-fold, 8-fold, and 16-fold to obtain the recovery rate range.
Sample type |
1:2 |
1:4 |
1:8 |
1:16 |
Serum (n=5) |
81-94% |
96-105% |
92-103% |
82-96% |
EDTA plasma (n=5) |
89-102% |
82-94% |
85-96% |
78-90% |
heparin plasma (n=5) |
93-102% |
80-93% |
91-100% |
88-95% |
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