IL21 检测试剂盒参数性能比较

比较品牌：

用酶联免疫检测的品牌如下： 预包被试剂盒；

biolegend：定量范围31.3-2,000 pg/mL； 灵敏度：4.2 pg/mL；样本用量：50ul；样本类型：血清，血浆，上清液；正常样本测试30例，17个值在7.2-61.2pg/ml 之间，13个值未检出；

thermofisher：定量范围78-5,000 pg/mL；灵敏度：20.0 pg/mL；样本用量：50ul；样本类型：血清，血浆，上清液；

IBL international：定量范围78-5,000 pg/mL；样本用量：50ul；样本类型：血清，血浆，上清液；

raybiotech：110 pg/ml - 8000 pg/ml；灵敏度：11.0 pg/mL；样本类型：血清，血浆，上清液；

未包被试剂盒先不讨论；

另外，raybiotech 和thermofisher  invitrogen 均已有用qPCR 方式检测蛋白浓度的试剂盒；

list：

Human IL-21 Proquantum Immunoassay Kit；

优势：灵敏度高；<0.3 pg/mL；定量范围宽：0.32-5000 pg/mL；样本用量少；Plasma 2-5 µL；Serum 2-5 µL；Supernatant 2-5 µL；时间：2小时；仪器：qPCR 仪器；

原理如下：

(A)  Antibody-antigen binding: Antibodies bind to two separate epitopes on the antigen (during a 1-hr incubation), which brings the two conjugated oligonucleotides into close proximity. (B) Ligation and amplification of signal (in a qPCR instrument): DNA ligase and a third splint oligonucleotide connector are added to ligate the two ends of the conjugated oligonucleotides, creating a 100-base DNA template. Once the ligase is inactivated at 95°C, the sample is amplified through 40 cycles of annealing and extension. The amount of DNA produced is measured after each amplification cycle via fluorescent dyes, which exhibit fluorescence that is directly proportional to the number of PCR product molecules (or amplicons) generated. This graph shows the fluorescence vs. cycle number curves for four different starting protein concentrations. The dashed line represents the fluorescence threshold. The cycle number required to reach the fluorescence threshold (threshold cycle or Ct) is plotted vs. protein concentration to create a standard curve.

翻译过来，就是：

(A)抗体-抗原结合:抗体与抗原上的两个独立表位结合(在1小时的孵育过程中)，这使得两个结合的寡核苷酸非常接近。

(B)信号的连接和扩增(在qPCR仪器中):加入脱氧核糖核酸连接酶和第三夹板寡核苷酸接头，连接共轭寡核苷酸的两端，产生100碱基的脱氧核糖核酸模板。一旦连接酶在95℃失活，样品通过40个退火和延伸循环被扩增。在每个扩增循环后，通过荧光染料测量产生的DNA量，荧光染料显示的荧光与产生的扩增产物的数量成正比。

该图显示了四种不同起始蛋白质浓度的荧光对循环数曲线。

虚线代表荧光阈值。将达到荧光阈值(阈值循环或Ct)所需的循环数与蛋白质浓度进行对比，绘制出标准曲线。

raybiotech 的类似产品：

Human IL-21 IQELISA™ Kit：

The RayBio® Immuno Quantitative Enzyme Linked ImumunoSorbent Assay (IQELISA™) is an innovative new assay that combines the specificity and ease of use of an ELISA with the sensitivity of real-time PCR. This results in an assay that is simultaneously familiar and cutting edge and enables the use of lower sample volumes while also providing more sensitivity. The RayBio® Human IL-21 IQELISA™ Kit is a modified ELISA assay with high sensitivity qPCR readout for the quantitative measurement of Human IL-21 in serum, plasma, and cell culture supernatants. This assay employs an antibody specific for Human IL-21 coated on a 96-well PCR plate. Standards and samples are pipetted into the wells and IL-21 present in a sample is bound to the wells by the immobilized antibody. The wells are washed and a detection affinity molecule is added to the plates. After washing away unbound detection affinity molecule, primers and a PCR master mix are added to the wells and data is collected using qPCR. C_t values obtained from the qPCR are then used to calculate the amount of antigen contained in each sample, where lower C_t values indicate a higher concentration of antigen.