Principle of magnetic bead method for nucleic acid extraction

With the rapid development of molecular biology technology, molecular diagnosis and detection technologies represented by nucleic acid hybridization, nucleic acid amplification and nucleic acid sequence analysis have increasingly played a vital role in many fields. Sample processing is the "first step" and the most critical step in molecular diagnostic experiments. The quality of the nucleic acids obtained will directly affect the success or failure of downstream molecular biology experiments. The global outbreak of the new coronavirus has prompted a surge in the nucleic acid testing market. During the entire epidemic period, the domestic nucleic acid testing market will exceed 40 billion.

Traditional methods of nucleic acid extraction Traditional extraction methods mainly include: phenol/chloroform extraction, alcohol precipitation, affinity chromatography column, density gradient centrifugation and silica gel column method. These traditional extraction methods can isolate DNA and RNA from different tissue samples. However, these technologies include precipitation and centrifugation steps, which require a large amount of biological samples. The extraction steps are complicated, time-consuming and labor-intensive, and the yield is low. High, it is difficult to realize automated operations. In addition, most traditional methods also require the use of toxic chemical reagents, which are potentially harmful to the health of operators. Therefore, with the development of molecular biology and materials science, magnetic beads are used. New methods for isolating and purifying nucleic acids from liquid-phase systems have emerged.

The principle of magnetic bead method for separating nucleic acids. Nano-magnetic beads are formed by coating polymer materials or biomolecules with a core of iron tetraoxide. They can be adsorbed by magnets and nano-sized beads at the same time. The functional groups on the surface of magnetic beads used for nucleic acid purification are generally (OH) and carboxyl (COOH).

The core technology of magnetic bead separation of nucleic acids is solid-phase reversible immobilization technology. However, it is not yet clear how the magnetic beads and nucleic acids interact and adsorb together. The salt bridge theory is one of the conjectures. In a system that uses magnetic beads to bind nucleic acids, the nucleic acid molecules (DNA & RNA) will change from linear to spherical due to the action of the buffer, exposing a large number of negatively charged groups on the nucleic acid skeleton to connect to the cations in the reaction system. Under the action of the negatively charged groups on the outer layer, a salt bridge structure of "anion-cation-anion" is formed, allowing nucleic acid molecules to be specifically adsorbed to the surface of the magnetic beads. When the reaction buffer is discarded and water-based molecules are added, the nucleic acid molecules will be quickly and fully hydrated, and the ionic interactions between the three will be released, allowing the nucleic acid molecules adsorbed to the magnetic beads to be purified.

Magnetic bead nucleic acid extraction is a perfect combination of nanotechnology and biotechnology. Nanomagnetic beads have a large specific surface area due to their small size. Nanotechnology is used to modify the surface of magnetic beads so that the surface of the magnetic beads has more nucleic acid binding sites, thereby improving the efficiency and sensitivity of nucleic acid extraction and recovery by nanomagnetic beads.

Nucleic acid extraction has the following characteristics:

1. The production process of magnetic beads is strictly controlled. Each magnetic bead has a regular spherical shape to ensure the stability of extraction of low-abundance samples.
2. The surface of magnetic beads is specially treated to achieve DNA/RNA co-extraction.
3. Also suitable for low-abundance samples, including cell-free DNA, viral DNA and RNA.
4. The production capacity is stable and the monthly production capacity can reach 10kg.
5. The batches are stable, and the nucleic acid extraction efficiency CV of different batches is <10%.
6. It can achieve high-throughput and automated operations, and can achieve extraction in 9 minutes at the fastest when used with a nucleic acid extraction instrument.