Cationic liposomes are traditionally used for the delivery of genetic materials such as various types of DNA (pDNA, cDNA, CpG DNA, oligonucleotide, antisense oligonucleotide, etc.), various types of RNA such as (siRNA, mRNA, etc.) and nucleic acid mimics (NAMs). The encapsulation of DNA into the conventional neutral charged PC based liposomes can be a technical problem mainly due to the plasmid size. Due to this problem in late 80s, the liposomes composed of cationic lipids and PE have been developed. The idea was to neutralize the negative charge of pDNA with positive charge of cationic lipids in order to capture more plasmid efficiently mainly due to electrostatic interaction and deliver them into the cells. Generally, the procedure is simply based on mixing the cationic liposomes with DNA or RNA and adding them to the cells. This results in the formulations of aggregates.
In order to design a proper cationic lipid for gene delivery, two approaches have been used for the cationic lipid synthesis: 1) cholesterol-based design such as DC-Cholesterol and GL-67 lipids, and 2) non-cholesterol-based designs such as DOTAB, DDAB and DOTMA. To successfully transfer the gene in vitro using liposomes, some consideration should be taken into account: i) the ability of binding and packing DNA/RNA in liposomes; ii) the interaction of the packaged DNA/RNA to the cell surface; iii) the efficiency of the internalization of DNA/RNA; iv) the intracellular DNA-release from endosomes in case of endocytosis involvement; v) the transgenic expression level in cell nuclei. pH-sensitive liposomes have been designed based on their tendency to release their content in the acidic condition. The primary concept was based on viruses that fuse with the endosomal membrane by means of a protein at pH 5-6, delivering their genetic material to the cytosol before reaching the lysosomes. Typically, a pH-sensitive liposome consists of dioleoylphosphatidylethanolamine (DOPE). Since phosphatidylethanolamine (PE) changes in acidic conditions, it is believed to act as a membrane fusion promoter. The effectiveness of the interaction between liposomes and cells is highly dependent on the liposome compositions. Liposomes are captured by various endocytosic processes, and the efficiency depends on the cell type and liposome size. Liposomes of various sizes and charges can attach to the macrophages and neutrophils through active phagocytosis. After attachment of the liposome to the cell surface, the internalization into the endosomes occurs due to a more acidic pH (6.50) at early endosomes. The liposomes are transferred to the last endosome with more acidic pH (5.5-6.0) by maturation or vesicular fusion, which takes 10-15 min. Twenty minutes (or more) after uptake, the contents are delivered to the lysosome with pH 5.0 or less. Lysosomes are the main degrading and last endocytotic section in the endocytotic pathway, in where pH-insensitive liposomes are accumulated and degraded. However, after penetration of pH-sensitive liposomes into cells, the accumulation and degradation do not occur.
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2.加大辣根过氧化物酶标记的链霉亲和素；
我现在用商品化的试剂盒进行夹心法ELISA测定某抗体的浓度，盒子给定了4个标准品，标准品抗体浓度为70000~1000单位，测定步骤中要求对样品进行1:1000稀释后测定。
但是有的样本按照1:1000稀释后，最终OD值大于70000浓度的标准品的OD值，然后使用ELISACALC软件进行四参数拟合，超过了标准曲线的范围，就算不出来这个样品的浓度，但是如果在1000-70000之间的OD值就可以算出相应浓度。请教大神们，接下来我是否可以对样品进行1:2000,1:4000浓度稀释，算出结果后再×2、×4，算作此样品的浓度呢？还是直接给一个＞70000的定性结果？或者可以有能算出来的其他软件？
Ps试剂盒中提及Dilutionlinearity（稀释线性？）为141%，这个是什么意思呢？
多谢！！
请大家帮帮忙，第一步加完抗原后必须封闭吗
目前，我用该蛋白的鼠源性单抗来包被ELISA板子，5%BSA37度封闭二小时后，洗涤四次后将板子分三个组加入抗原：其中一个组中加入的是我重组的蛋白，另一个组为用其它方法证实含该蛋白的人体内血清，最后一个组加入PBS。37度一小时后洗涤四次后每孔加入我制备的兔源性多抗。37度一小时洗涤六次后我再加入酶标记的抗兔的抗体37度40分钟后洗涤六次后TMB显色。
问题就在我显色后所有的孔都是阳性，其中以抗原为我的重组蛋白组与PBS组OD值最高，两组都可以达到1.8以上，而加入的抗原为人体血清组低，为0.6-1.0不等。
后面我优化条件，封闭液用过5%的脱脂奶粉，2%的BSA，包被的单抗浓度摸了梯度，加入的多抗也摸了梯度，酶标的抗体也摸了梯度。结果都没有改变，连趋势每次都是一样以重组蛋白组与PBS组OD最高。
今天我还试着把抗原换成其它蛋白也做出了强阳性？
请教各位高手，我的ELISA该如何往下面做了啊，是不是我的抗体本身有问题呢？
对了，我包被用的单抗是用GE公司的预装柱纯化的，很纯，在考染中是看不到一条杂带的。
ELISA双抗体夹心法(enzyme linked immunosorbent assay——sandwich technique)的原理是将特异性抗体结合到固相载体上形成固相抗体，然后和待检血清中的相应抗原结合形成免疫复合物，洗涤后再加酶标记抗体，与免疫复合物中抗原结合形成酶标抗体-抗原-固相抗体复合物，加底物显色，判断抗原含量。
生物帮有相关介绍。编码RNA http://doc.bio1000.com/show-3399.html
（2）封闭：将已包被的板用洗涤液洗涤2次，每孔加入120 μL封闭液，封闭一段时间，取出，甩干备用。
（3）竞争反应：在制备好的板中每孔加入50 μL系列浓度的标准品溶液和50 μL稀释好的酶标抗体溶液，孵育一段时间。
（4）洗板：用洗涤液洗涤5次。
（5）显色反应：每孔加入显色溶液100 μL，孵育一段时间。
（6）终止：每孔各加入终止液，在酶标仪上测定各孔的吸光值。
