Operating & Working Principles of Automatic Nucleic Acid Extractor

I. Fundamental Chemical Principle of Nucleic Acid Extraction (Magnetic Bead Method, Industry Standard)

1. Lysis & Binding
   Samples (whole blood, swabs, tissue, sputum, etc.) are mixed with lysis buffer to rupture cell and nuclear membranes and release genomic DNA or viral RNA. Under high-salt conditions in the reaction system, the phosphate backbone of nucleic acids carries negative charges. Silica hydroxyl groups on magnetic beads adsorb nucleic acid-protein complexes, while impurities including proteins, polysaccharides and lipids remain suspended in the liquid phase.
2. Magnetic Separation
   An integrated magnetic rod/sleeve assembly generates a magnetic field when energized. Magnetic beads bound with nucleic acids are captured on the surface of magnetic rods and completely separated from waste liquid.
3. Washing & Purification
   Wash buffer is dispensed to remove residual proteins, salt ions and PCR inhibitors (heme, heparin, etc.), retaining only magnetic bead-nucleic acid complexes.
4. Elution & Recovery
   Low-salt elution buffer breaks the binding force between silica hydroxyl groups and nucleic acids, so nucleic acids dissolve into the eluent for purified recovery.

II. Mechanical Operating Principle of the Whole Instrument

1. Magnetic Rod Transfer & Mixing Assembly (Core Mechanical Component)

• Mixing mode: Magnetic rods sleeved with disposable sleeves immerse into reaction wells and reciprocate vertically at high speed to agitate magnetic beads thoroughly for sufficient lysis, binding and washing reactions.
• Separation mode: Magnetic rods are magnetized to capture all magnetic beads at the well bottom. The assembly translates horizontally to transfer magnetic beads to the next well, leaving waste liquid in the original well.

2. Automatic Liquid Dispensing & Waste Removal System

• Micro plunger pumps paired with 8-channel / 96-channel pipette tips deliver precise volumes of lysis buffer, wash buffer and elution buffer.
• Negative-pressure waste suction channels extract waste liquid into a waste tank post-separation to avoid cross-contamination.
• Microliter-level quantitative accuracy for trace samples ranging from 10 μL to 1000 μL.

3. Temperature Control Module (Standard for High-End Models)

• 56–60 °C: Accelerate cell lysis and protein denaturation;
• 70–80 °C: High-temperature elution to improve nucleic acid recovery rate.
  Constant-temperature incubation stabilizes reaction efficiency and eliminates extraction deviations caused by temperature fluctuation.

4. Microplate Carrier Assembly

III. Standard Fully Automated Operation Workflow

Step 1: Manual Pre-loading of Reagents and Samples

Step 2: Instrument Loading and Program Initiation

1. Lysis and Homogenization
   Magnetic rods descend into the first well and perform high-speed vertical mixing for 3–10 minutes to fully lyse cells and enable magnetic bead-nucleic acid binding.
2. Magnetic Separation and Transfer
   Magnetic rods are magnetized to capture magnetic beads. The assembly moves horizontally to the waste well, demagnetizes to release beads, and pipette tips aspirate all waste liquid.
3. Multi-Round Washing
   Magnetic beads are sequentially transferred into wash buffer wells for two rounds of thorough cleaning to remove proteins and PCR inhibitors. Waste liquid is fully aspirated after each washing cycle.
4. High-Temperature Elution
   Magnetic beads are transferred to elution wells, followed by constant heating and low-speed mixing to dissociate nucleic acids from magnetic beads into eluent. Magnetic separation removes beads, leaving purified nucleic acids in the elution well.
5. Program Completion Alert
   The instrument stops automatically. Take out the microplate; purified nucleic acids in eluent can be directly applied to downstream experiments including qPCR, fluorescent quantitative PCR and sequencing.

IV. Structural & Principle Differences of Two Mainstream Models

1. Magnetic Rod Transfer Type (96-throughput, mainstream for clinical laboratories)
   Magnetic beads are carried across wells by magnetic rods with automatic waste aspiration. Features fast processing and high throughput, ideal for high-volume testing in hospital clinical labs and third-party inspection institutions.
2. In-Situ Magnetic Adsorption Type (32-throughput compact model)
   Magnetic beads do not transfer between wells. Built-in electromagnets at each well bottom capture beads in situ before waste aspiration. Compact footprint with simple structure, suitable for small outpatient laboratories.

V. Core Advantages of Automated Instruments

1. Cross-Contamination Prevention
   Disposable magnetic sleeves, independent liquid-dispensing pipette tips and fully enclosed reaction chambers eliminate cross-well splashing.
2. High Result Consistency
   All parameters including mixing duration, magnetic intensity, dispensing volume and incubation temperature are standardized by programmed control, eliminating human errors from manual extraction.
3. Fully Enclosed Biosafety Design
   Built-in negative-pressure cabin and UV disinfection modules prevent aerosol nucleic acid diffusion to meet high biosafety requirements.

VI. Summary of Core Technical Principles

1. Chemical core: Reversible nucleic acid adsorption via silica hydroxyl-modified magnetic beads
2. Mechanical core: Collaborative operation of magnetic rod mixing, directional magnetic separation and automatic liquid transfer & waste removal
3. Workflow logic: Lysis & Binding → Magnetic Separation & Waste Discard → Multi-Cycle Washing → High-Temperature Elution
4. Auxiliary modules: Precise liquid dispensing, constant-temperature incubation and rail translation motion control system