Cholecystokinin (CCK) ELISA Kit

Antigen: Cholecystokinin (CCK)

Synonyms: CCK-CHR, CCK, MGC140193, cck-l, CCKN, cck-n, MGC117187

Reactivity: Human

Application: ELISA

Certificates: ISO 9001:2008, ISO 13485:2003

Catalog no.: ABIN415079

Additional Information

Method type: Competition ELISA

Detection Method: Colorimetric

Alternative name: CCK

Cross-Reactivity (Details): No significant cross-reactivity or interference between human CCK and analogues was observed. Note: Limited by current skills and knowledge, it is impossible for us to complete the cross- reactivity detection between human CCK and all the analogues, therefore, cross reaction may still exist.

Sample Type: Serum, Plasma, Biological Fluids, Tissue Homogenate, Cell Culture Supernatant

Sample Volume: 50µL

Plate: Pre-coated 12 × 8 strip

Components:

• Pre-coated, ready to use 96-well strip plate - 1
• Plate sealer for 96 wells - 4
• Standard (lyophilized) - 2
• Standard Diluent - 1×20mL
• Detection Reagent A (green) - 1×120µL
• Assay Diluent A (2 × concentrate) - 1×6mL
• Detection Reagent B (red) - 1×120µL
• Assay Diluent B (2 × concentrate) - 1×6mL
• TMB Substrate - 1×9mL
• Stop Solution - 1×6mL
• Wash Buffer (30 × concentrate) - 1×20mL
• Instruction manual - 1

Specificity: This assay has high sensitivity and excellent specificity for detection of human CCK.

Sensitivity: The sensitivity of this assay, or Lower Limit of Detection (LLD) was defined as the lowest protein concentration that could be differentiated from zero. It was determined by subtracting two standard deviations to the mean optical density value of twenty zero standard replicates and calculating the corresponding concentration.

Minimum Detection Limit: 4.55 pg/mL

Detection Range: 12.35-1,000 pg/mL

Assay Precision: Intra-assay Precision (Precision within an assay): 3 samples with low, middle and high level human CCK were tested 20 times on one plate, respectively.
Inter-assay Precision (Precision between assays): 3 samples with low, middle and high level human CCK were tested on 3 different plates, 8 replicates in each plate.
CV(%) = SD/meanX100

• Intra-Assay: CV less than 10%
• Inter-Assay: CV less than 12%

Comments:

The standard curve concentrations used for the ELISA’s were 1,000pg/mL, 333.33pg/mL, 111.11pg/mL, 37.04pg/mL, 12.35pg/mL.The stability of ELISA kit is determined by the loss rate of activity. The loss rate of this kit is less than 5% within the expiration date under appropriate storage condition. The loss rate was determined by accelerated thermal degradation test. Keep the kit at 37°C for 3 days, and compare O.D.values of the kit kept at 37°C with that of at recommended temperature. (referring from China Biological Products Standard, which was calculated by the Arrhenius equation. For ELISA kit, 1 day storage at 37°C can be considered as 2 months at 4°C, which means 3 days at 37°C equaling 6 months at 4°C).

Application Details

Principle: The kit is a competitive inhibition enzyme immunoassay technique for the in vitro quantitative measurement of CCK in human serum, plasma, tissue homogenates, cell culture supernates and other biological fluids.

Protocol: This assay employs the competitive inhibition enzyme immunoassay technique. A monoclonal antibody specific for human CCK has been pre-coated onto a microplate. A competitive inhibition reaction is launched between biotin labeled human CCK and unlabeled human CCK (Standards or samples) with the pre-coated antibody specific for human CCK. After incubation the unbound conjugate is washed off. Next, avidin conjugated to Horseradish Peroxidase (HRP) is added to each microplate well and incubated. The amount of bound HRP conjugate is reverse proportional to the concentration of CCK in the sample. After addition of the substrate solution, the intensity of color developed is reverse proportional to the concentration of CCK in the sample.

• Prepare all reagents, samples and standards,
• Add 50µL standard or sample to each well. And then add 50µL prepared Detection Reagent A immediately. Shake and mix. Stay overnight at 4°C,
• Aspirate and wash 3 times,
• Add 100µL prepared Detection Reagent B. Incubate 30 minutes at 37°C,
• Aspirate and wash 5 times,
• Add 90µL Substrate Solution. Incubate 15-25 minutes at 37°C,
• Add 50µL Stop Solution. Read at 450 nm immediately.

Reagent Preparation:

• Bring all kit components and samples to room temperature (18-25°C) before use.
• Standard - Reconstitute the Standard with 0.5mL of Standard Diluent, kept for 10 minutes at room temperature, shake gently(not to foam). The concentration of the standard in the stock solution is 1,000pg/mL. Please prepare 5 tubes containing 0.6mL Standard Diluent and produce a triple dilution series. Mix each tube thoroughly before the next transfer. Set up 5 points of diluted standard such as 1,000pg/mL, 333.33pg/mL, 111.11pg/mL, 37.04pg/mL, 12.35pg/mL, and the last EP tubes with Standard Diluent is the blank as 0pg/mL.
• Assay Diluent A and Assay Diluent B - Dilute 6mL of Assay Diluent A or B Concentrate(2×) with 6mL of deionized or distilled water to prepare 12 mL of Assay Diluent A or B. (In fact, more than 6mL Assay Diluent A and Assay Diluent B are contained in the bottles. Therefore, in every test, please precisely pipette required amount of Diluent and make double dilution in a new container. The prepared working dilution cannot be frozen.)
• Detection Reagent A and Detection Reagent B - Briefly spin or centrifuge the stock Detection A and Detection B before use. Dilute to the working concentration with working Assay Diluent A or B, respectively (1:100).
• Wash Solution - Dilute 20mL of Wash Solution concentrate (30×) with 580mL of deionized or distilled water to prepare 600 mL of Wash Solution (1×).
• TMB substrate - Aspirate the needed dosage of the solution with sterilized tips and do not dump the residual solution into the vial again.

Note:

• Making serial dilution in the wells directly is not permitted.
• Prepare standard within 15 minutes before assay. Please do not dissolve the reagents at 37°C directly.
• Detection Reagent A and B are sticky solutions, therefore, slowly pipette them to reduce the volume errors.
• Please carefully reconstitute Standards or working Detection Reagent A and B according to the instruction, and avoid foaming and mix gently until the crystals are completely dissolved. To minimize imprecision caused by pipetting, use small volumes and ensure that pipettors are calibrated. It is recommended to suck more than 10µL for once pipetting.
• The reconstituted Standards, Detection Reagent A and Detection Reagent B can be used only once.
• If crystals have formed in the Wash Solution concentrate (30×), warm to room temperature and mix gently until the crystals are completely dissolved.
• Contaminated water or container for reagent preparation will influence the detection result.

Sample Collection: Not all sample types may be valid for this kit. Please look up which sample types apply.

Serum: Allow samples to clot for two hours at room temperature or overnight at 4°C before centrifugation for 20 minutes at approximately 1000 × g. Assay immediately or store samples in aliquot at -20°C or -80°C. Avoid repeated freeze/thaw cycles.
Plasma: Collect plasma using EDTA or heparin as an anticoagulant. Centrifuge samples for 15 minutes at 1000 × g within 30 minutes of collection. Remove plasma and assay immediately or store samples in aliquot at -20°C or -80°C. Avoid repeated freeze/thaw cycles.
Tissue homogenates: The preparation of tissue homogenates will vary depending upon tissue type. For this assay, rinse tissues in ice-cold PBS (0.02mol/L,pH 7.0-7.2) to remove excess blood thoroughly and weigh before homogenization. Mince the tissues to small pieces and homogenize them in 5-10 mL of PBS with a glass homogenizer on ice (Micro Tissue Grinders work, too). Sonicate the resulting suspension with an ultrasonic cell disrupter or subject it to two freeze-thaw cycles to further break the cell membranes. Centrifugate the homogenates for 5 minutes at 5000 × g. Remove the supernate and assay immediately or aliquot and store at -20°C.
Cell lysates: Cells must be lysed before assaying according to the following directions. Adherent cells should be detached with trypsin and then collected by centrifugation (suspension cells can be collected by centrifugation directly). Wash cells three times in cold PBS. Resuspend cells in PBS (1×) and subject them to ultrasonication for 4 times (or Freeze cells at -20 °C. Thaw cells with gentle mixing. Repeat the freeze/thaw cycle for 3 times.) Centrifuge at 1500 × g for 10 minutes at 2 - 8°C to remove cellular debris.

Platelet-poor plasma: Collect plasma using EDTA or heparin as an anticoagulant. Centrifuge samples for 15 minutes at 1000 × g at 2-8°C within 30 minutes of collection. It is recommended to centrifuge samples for 10 minutes at 10,000 × g for complete platelet removal. Remove plasma and assay (see activation procedure) immediately or store samples in aliquot at -20°C or -80°C for later use. Avoid repeated freeze/thaw cycles.

Saliva: Collect sample in centrifuge tube. To clarify, freeze sample at -70°C for 1 hour. Thaw sample on ice, and centrifuge at 2,000 × g for 10 minutes. Transfer clarified supernatant to clean tube for use in the assay. Alternatively, the clarified saliva samples can be frozen at -20°C and assayed at a later date. It is recommended that the saliva sample be aliquoted to convenient volumes prior to storing at -20°C to avoid multiple freeze thaw cycles.

Seminal plasma: Collect semen samples using a sterile container, then allow it to liquefy at room temperature or 37°C. After liquefaction, centrifuge at 4000 rpm for 10 min. Remove the supernate and assay immediately or store samples at -20°C.
Sperm: Collect semen samples using a sterile container, then allow it to liquefy at room temperature or 37°C. After liquefaction, centrifuge at 2,000 × g for 10-15 minutes and remove seminal plasma, wash precipitated protein and centrifuge for three times. Subject the precipitated protein to ultrasonication, centrifuge at 2,000 × g for 10-15 minutes. Remove the supernate and assay immediately or store samples at -20°C or -80°C for later use. Avoid repeated freeze/thaw cycles.

Urine: Aseptically collect the first urine of the day (mid-stream) , voided directly into a sterile container. Centrifuge to remove particulate matter, assay immediately or aliquot and store at -20°C. Avoid repeated freeze-thaw cycles.

Milk, cell culture supernates and other biological fluids: Centrifuge samples for 20 minutes at 1000 × g. Remove particulates and assay immediately or store samples in aliquot at -20 °C or -80 °C for later use. Avoid repeated freeze/thaw cycles.Tears: Centrifuge samples for 20 minutes at 1000 × g. Remove particulates and assay immediately or store samples in aliquot at -20°C or -80°C for later use. Avoid repeated freeze/thaw cycles.
Lung lavage fluid: Remove particulates by centrifugation and assay immediately or aliquot and store samples at -20°C or -80°C. Avoid repeated freeze-thaw cycles.
Cerebrospinal fluid: Remove particulates by centrifugation and assay immediately or aliquot and store samples at -20°C. Avoid repeated freeze-thaw cycles.
Biological agents: Remove particulates by centrifugation and assay immediately or aliquot and store samples at -20°C. Avoid repeated freeze-thaw cycles.

Sweat: Collect sweat using a collection device or equivalent. Assay immediately or aliquot and store samples at -20°C. Avoid repeated freeze-thaw cycles.

Sample Preparation: Notes:

• The supplier is only responsible for the kit itself, but not for the samples consumed during the assay. The user should calculate the possible amount of the samples used in the whole test. Please reserve sufficient samples in advance.
• Please predict the concentration before assaying. If values for these are not within the range of the standard curve, users must determine the optimal sample dilutions for their particular experiments.
• If the samples are not indicated in the manual, a preliminary experiment to determine the validity of the kit is necessary.
• Tissue or cell extraction samples prepared by chemical lysis buffer may cause unexpected ELISA results due to the impacts from certain chemicals.
• Due to the possibility of mismatching between antigen from other origin and antibody used in our kits (e.g., antibody targets conformational epitope rather than linear epitope), some native or recombinant proteins from other manufacturers may not be recognized by our products.
• Influenced by the factors including cell viability, cell number or sampling time, samples from cell culture supernatant may not be detected by the kit.
• Fresh samples without long time storage is recommended for the test. Otherwise, protein degradation and denaturalization may occur in those samples and finally lead to wrong results.

Assay Procedure:

• 1. Determine wells for diluted standard, blank and sample. Prepare 5 wells for standard points, 1 well for blank. Add 50µL each of dilutions of standard (read Reagent Preparation), blank and samples into the appropriate wells, respectively. And then add 50µL of Detection Reagent A to each well immediately. Shake the plate gently (using a microplate shaker is recommended). Cover with a Plate sealer and stay overnight at 4°C. Detection Reagent A may appear cloudy. Warm to room temperature and mix gently until solution appears uniform.
• 2. Aspirate the solution and wash with 350µL of 1X Wash Solution to each well using a squirt bottle, multi-channel pipette, manifold dispenser or autowasher, and let it sit for 1-2 minutes. Remove the remaining liquid from all wells completely by snapping the plate onto absorbent paper. Repeat 3 times. After the last wash, remove any remaining Wash Buffer by aspirating or decanting. Invert the plate and blot it against absorbent paper.
• 3. Add 100µL of Detection Reagent B working solution to each well. Incubate for 30 minutes at 37°C after covering it with the Plate sealer.
• 4. Repeat the aspiration/wash process for total 5 times as conducted in step 2.
• 5. Add 90µL of Substrate Solution to each well. Cover with a new Plate sealer. Incubate for 15 - 25 minutes at 37°C (Don't exceed 30 minutes). Protect from light. The liquid will turn blue by the addition of Substrate Solution.
• 6. Add 50µL of Stop Solution to each well. The liquid will turn yellow by the addition of Stop solution. Mix the liquid by tapping the side of the plate. If color change does not appear uniform, gently tap the plate to ensure thorough mixing.
• 7. Remove any drop of water and fingerprint on the bottom of the plate and confirm there is no bubble on the surface of the liquid. Then, run the microplate reader and conduct measurement at 450nm immediately.

Note:

• 1. Assay preparation: Keep appropriate numbers of wells for 1 experiment and remove extra wells from microplate. Rest wells should be resealed and stored at -20°C.
• 2. Samples or reagents addition: Please use the freshly prepared Standard. Please carefully add samples to wells and mix gently to avoid foaming. Do not touch the well wall. For each step in the procedure, total dispensing time for addition of reagents or samples to the assay plate should not exceed 10 minutes. This will ensure equal elapsed time for each pipetting step, without interruption. Duplication of all standards and specimens, although not required, is recommended. To avoid cross-contamination, change pipette tips between additions of standards, samples, and reagents. Also, use separated reservoirs for each reagent.
• 3. Incubation: To ensure accurate results, proper adhesion of plate sealers during incubation steps is necessary. Do not allow wells to sit uncovered for extended periods between incubation steps. Once reagents are added to the well strips, DO NOT let the strips DRY at any time during the assay. Incubation time and temperature must be controlled.
• 4. Washing: The wash procedure is critical. Complete removal of liquid at each step is essential for good performance. After the last wash, remove any remaining Wash Solution by aspirating or decanting and remove any drop of water and fingerprint on the bottom of the plate. Insufficient washing will result in poor precision and false elevated absorbance reading.
• 5. Controlling of reaction time: Observe the change of color after adding TMB Substrate (e.g. observation once every 10 minutes), if the color is too deep, add Stop Solution in advance to avoid excessively strong reaction which will result in inaccurate absorbance reading.
• 6. TMB Substrate is easily contaminated. Please protect it from light.
• 7. The environment humidity which is less than 60% might have some effects on the final performance, therefore, a humidifier is recommended to be used at that condition.

Calculation of Results: This assay employs the competitive inhibition enzyme immunoassay technique, so there is an inverse correlation between CCK concentration in the sample and the assay signal intensity. Average the duplicate readings for each standard, control, and samples. Create a standard curve on log-log or semi-log graph paper, with the log of CCK concentration on the y-axis and absorbance on the x-axis. Draw the best fit straight line through the standard points and it can be determined by regression analysis. Using some plot software, for instance, curve expert 1.30, is also recommended. If samples have been diluted, the concentration read from the standard curve must be multiplied by the dilution factor.
In order to make the calculation easier, we plot the O.D. value of the standard (X-axis) against the log of concentration of the standard (Y-axis), although concentration is the independent variable and O.D. value is the dependent variable. The O.D. values of the standard curve may vary according to the conditions of assay performance (e.g. operator, pipetting technique, washing technique or temperature effects). Typical standard curve below is provided for reference only.

Application Notes:

• Limited by the current condition and scientific technology, we cannot completely conduct the comprehensive identification and analysis on the raw material provided by suppliers. So there might be some qualitative and technical risks to use the kit.
• The final experimental results will be closely related to validity of the products, operation skills of the end users and the experimental environments. Please make sure that sufficient samples are available.
• Kits from different batches may be a little different in detection range, sensitivity and color developing time.
• Do not mix or substitute reagents from one kit lot to another. Use only the reagents supplied by manufacturer.
• Protect all reagents from strong light during storage and incubation. All the bottle caps of reagents should be covered tightly to prevent the evaporation and contamination of microorganism.
• There may be some foggy substance in the wells when the plate is opened at the first time. It will not have any effect on the final assay results. Do not remove microtiter plate from the storage bag until needed.
• Wrong operations during the reagents preparation and loading, as well as incorrect parameter setting for the plate reader may lead to incorrect results. A microplate plate reader with a bandwidth of 10nm or less and an optical density range of 0-3 O.D. or greater at 450 ± 10nm wavelength is acceptable for use in absorbance measurement. Please read the instruction carefully and adjust the instrument prior to the experiment.
• Even the same operator might get different results in two separate experiments. In order to get better reproducible results, the operation of every step in the assay should be controlled. Furthermore, a preliminary experiment before assay for each batch is recommended.
• Each kit has been strictly passed Q.C test. However, results from end users might be inconsistent with our in-house data due to some unexpected transportation conditions or different lab equipments. Intra-assay variance among kits from different batches might arise from above factors, too.
• Kits from different manufacturers for the same item might produce different results, since we have not compared our products with other manufacturers.

Handling Advice: To minimize extra influence on the performance, operation procedures and lab conditions, especially room temperature, air humidity, incubator temperature should be strictly controlled. It is also strongly suggested that the whole assay is performed by the same operator from the beginning to the end.

Precaution of Use: The Stop Solution suggested for use with this kit is an acid solution. Wear eye, hand, face, and clothing protection when using this material.

Material not included:

• Microplate reader with 450 ± 10 nm filter.
• Precision single or multi-channel pipettes and disposable tips.
• Eppendorf Tubes for diluting samples.
• Deionized or distilled water.
• Absorbent paper for blotting the microtiter plate.
• Container for Wash Solution

Storage: -20°C/4°C

Storage Comment:

• For unopened kit: All the reagents should be kept according to the labels on vials. The Standard, Detection Reagent A, Detection Reagent B and the 96-well strip plate should be stored at -20°C upon receipt while the others should be at 4°C.
• For opened kit: When the kit is opened, the remaining reagents still need to be stored according to the above storage condition. Besides, please return the unused wells to the foil pouch containing the desiccant pack, and reseal along entire edge of zip-seal.
  Note: It is highly recommended to use the remaining reagents within 1 month provided this is within the expiration date of the kit.
• For ELISA kit, 1 day storage at 37°C can be considered as 2 months at 4°C, which means 3 days at 37°C equaling 6 months at 4°C.

Expiry Date: The expiry date is stated on the label.

Restrictions: For Research Use only

Images

Typical Standard Curve for Human CCK ELISA.