Answers to the misunderstandings of nucleic acid extraction with biological magnetic beads
What is nucleic acid extraction using biological magnetic beads?
Compared with the traditional chloroform isoamyl alcohol extraction method and centrifuge column kit method, the use of biological magnetic beads for nucleic acid extraction is a new method of nucleic acid extraction.
What are the advantages of nucleic acid extraction from biological magnetic beads?
With the popularity of genetic testing, personalized drug delivery, prenatal diagnosis, and other fields in the biological industry are pursuing high-throughput and automated today, the limitations of traditional DNA extraction methods are becoming more and more obvious, while the advantages of magnetic bead method DNA extraction are becoming more and more obvious: it can realize automatic, mass operation; Simple operation, short time; Do not use the traditional method of benzene, chloroform and other toxic reagents, safe and non-toxic completely in line with the modern environmental protection concept; The specific binding to nucleic acid makes the extracted nucleic acid high purity and high concentration.
However, there are still many people who do not fully understand this approach. There are also some misunderstandings in the process of nucleic acid purification by magnetic beads. The following articles will give you a new understanding of the magnetic bead purification of nucleic acids.
Answers to the misunderstandings of nucleic acid extraction with biological magnetic beads
Misunderstanding 1: the more magnetic beads used, the better the extraction effect
Many people like to increase the number of magnetic beads when the extraction effect is not good. They thought that adding more magnetic beads would bind more nucleic acids. But this is not always the case.
The main characteristic of magnetic beads is that they can be dispersed in a liquid and separated from a liquid in a solid state under the action of the external magnetic field. In any reagent system, there should be a certain threshold for the ratio of magnetic beads to liquid. Beyond a certain proportion, too many magnetic beads will lose their dispersing characteristics because they cannot be evenly dispersed in the liquid, which also makes it impossible to fully improve the efficiency of the contact between nucleic acid, magnetic beads and liquid during the washing process.
Too many magnetic beads also adsorb more impurities, making them harder to remove. Moreover, too many magnetic beads will adsorb protease, lysozyme and other functional components that play a major role in the liquid system, resulting in low extraction efficiency of the kit. Most of the time, when the extraction effect is not good, reducing the number of magnetic beads used is the best way to improve the extraction effect.
Misunderstanding 2: the more reagent dosage, the better the extraction effect
For the magnetic bead method, increasing the volume of liquid will reduce the probability of magnetic bead collision, and reducing the probability of magnetic bead collision will lead to a significant decrease in adsorption efficiency. So in many cases, although the addition of lysis buffer and washing buffer can indeed enhance lysis and enhance the washing effect, the core of magnetic bead extraction is the adsorption efficiency of magnetic beads on the nucleic acid. Lower collisions between magnetic beads lead to lower extraction results. Therefore, simply increasing the amount of reagent to improve the extraction effect may not be completely effective.
Misunderstanding 3: the more washing times, the better the extraction effect
When there are too many impurities in the extracted nucleic acid, the user will consider doing more washing to obtain a purer nucleic acid. Increasing the washing times is indeed beneficial to the purification of nucleic acid, but it is believed that a certain amount of nucleic acid will be lost in each washing, which increases the possibility of nucleic acid fragmentation and hydrolysis. Therefore, the washing times should be controlled in 2 ~ 4 times.
Misunderstanding 4: the more samples added, the better the extraction effect
When the sample is not fresh enough or the nucleic acid itself is very small, it often leads to poor nucleic acid extraction. At this time, many people will increase the amount of nucleic acid extraction by adding samples.
But simply increasing the sample size can sometimes introduce too many impurities. In addition, exceeding the lysis capacity of the lysis buffer also reduces the extraction efficiency, so increasing the extraction volume by simply increasing the sample size is not recommended.
Misunderstanding 5: If a magnetic bead is good, it should work well in all tests
There are many kinds of magnetic beads, and different particle sizes, different dispersions, different magnetic response times, different coating substrates, different surface modification functional groups, different coating densities, and different functional arm lengths, will lead to different characteristics of magnetic beads. Therefore, different magnetic beads adapt to different experiments and systems.
Some magnetic beads showed higher adsorption efficiency in constant nucleic acid extraction, and some magnetic beads were more suitable for trace nucleic acid extraction. Some magnetic beads are suitable for acid series reagent systems, and some magnetic beads are suitable for basic series reagent systems. Some magnetic beads' magnetic response is good, but the sedimentation speed is fast, more suitable for magnetic rod automatic extraction instrument; Some magnetic beads have slow sedimentation speed, but long magnetic response time, which is more suitable for the pipet-type automatic extractor.
Few magnetic beads are suitable for all experimental situations. In addition to the fixed kit, in most cases, a series of adjustments must be made to the magnetic bead and reagent systems.
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