Vitamin D3 (VD3) ELISA Kit

This assay employs a two-site sandwich ELISA to quantitate VD3 in samples. An antibody specific for VD3 has been pre-coated onto a microplate. Standards and samples are pipetted into the wells and any VD3 present is bound by the immobilized antibody. After removing any unbound substances, a biotin-conjugated antibody specific for VD3 is added to the wells. After washing, Streptavidin conjugated Horseradish Peroxidase (HRP) is added to the wells. Following a wash to remove any unbound avidin-enzyme reagent, a substrate solution is added to the wells and color develops in proportion to the amount of VD3 bound in the initial step. The color development is stopped and the intensity of the color is measured.
 

Cholecalciferol is a form of vitamin D, also called vitamin D3. It is structurally similar to steroids such as testosterone, cholesterol, and cortisol (though vitamin D3 itself is a secosteroid). Cholecalciferol is produced industrially for use in vitamin supplements and to fortify foods by the ultraviolet irradiation of 7-dehydrocholesterol extracted from lanolin found in sheep's wool. Paraphrasing a more detailed explanation, cholesterol is extracted from wool grease and wool wax alcohols obtained from the cleaning of wool after shearing. The cholesterol undergoes a four step process to make 7-dehydrocholesterol, the same compound that is stored in the skin of animals. The 7-dehydrocholesterol is then irradiated with ultra violet light. Rodents are somewhat more susceptible to high doses than other species, and cholecalciferol has been used in poison bait for the control of these pests.
 

Reagents	Quantity	Reagents	Quantity
Assay plate (96 Wells)	1	Instruction manual	1
Standard (lyophilized)	2	Sample Diluent	1 x 20 mL
Biotin-Conjugate (concentrate 100 x)	1 x 120 μL	Biotin-Conjugate Diluent	1 x 12 mL
Streptavidin-HRP  (concentrate 100 x)	1 x 120 μL	Streptavidin-HRP Diluent	1 x 12 mL
Wash Buffer (concentrate 25 x)	1 x 20 mL	Substrate Solution	1 x 10 mL
Stop Solution	1 x 6 mL	Adhesive Films	4

 

This assay has high sensitivity and excellent specificity for detection of Human VD3. No significant cross-reactivity or interference between Human VD3 and analogues was observed.
 

Matrices listed below were spiked with certain level of recombinant Human VD3 and the recovery rates were calculated by comparing the measured value to the expected amount of Human VD3 in samples.

Sample Type	Number	Recovery range (%)	Average(%)
Serum	10	90-101	96
EDTA plasma	10	89-97	93
Heparin plasma	10	91-99	95

 

Intra-assay Precision (Precision within an assay) Three samples of known concentration were tested twenty times on one plate to assess intra-assay precision. Inter-assay Precision (Precision between assays) Three samples of known concentration were tested in forty separate assays to assess inter-assay precision. CV (%) = SD/meanX100 Intra-Assay: CV<8% Inter-Assay: CV<12%
 

The linearity of the kit was assayed by testing samples spiked with appropriate concentration of Human VD3 and their serial dilutions. The results were demonstrated by the percentage of calculated concentration to the expected.

Sample Type	1：2	1：4	1：8	1：16
Serum	78-89%	81-99%	92-103%	95-105%
EDTA plasma	91-101%	90-98%	93-101%	91-98%
Heparin plasma	92-103%	93-102%	92-99%	91-101%

 

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 4 and 7 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, 4 days storage at 37°C can be considered as 6 months at 2 - 8°C, which means 7 days at 37°C equaling 12 months at 2 - 8°C).
 

Serum: Use a serum separator tube (SST) and allow samples to clot for two hours at room temperature or overnight at 2 - 8°C before centrifugation for 15 minutes at 1000 × g. Remove serum and assay immediately or aliquot and store samples at ≤ -20°C. Avoid repeated freeze-thaw cycles. Plasma: Collect plasma using EDTA, or heparin as an anticoagulant. Centrifuge for 15 minutes at 1000 × g at 2 - 8°C within 30 minutes of collection. Assay immediately or aliquot and store samples at ≤ -20°C. Avoid repeated freeze-thaw cycles. 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. Avoid repeated freeze/thaw cycles.
 

Store at 2-8°C. Please refer to Instruction Manual.