鏈霉親和素磁珠（Streptavidin Magnetic Beads）是一類以鏈霉親和素（Streptavidin）為功能配基、表面共價偶聯在超順磁性微球上的親和介質，依托SA-生物素的超高親和力，實現目標分子的快速、高特異性富集與磁分離，廣泛用于生物素化分子（DNA、RNA、抗體、蛋白等）的高選擇性捕獲與富集。

Streptavidin magnetic beads are a type of affinity medium that uses streptavidin as the functional ligand and is covalently coupled to superparamagnetic microspheres on the surface. Relying on the extremely high affinity of SA-biotin, they enable rapid and highly specific enrichment and magnetic separation of target molecules, and are widely used for the high-selective capture and enrichment of biotinylated molecules (such as DNA, RNA, antibodies, proteins, etc.).

鏈霉親和素磁珠的核心原理是利用鏈霉親和素與生物素之間極強的非共價結合能力。鏈霉親和素是一種從鏈霉菌中提取的四聚體蛋白，每個亞基都能與一個生物素分子結合。通過將鏈霉親和素共價偶聯到磁性納米顆粒表面，形成功能化磁珠。這種技術結合了磁珠的快速分離特性和鏈霉親和素-生物素系統的高親和力（Kd≈10?1? M），實現了對生物分子的高效、特異性捕獲和純化。

The core principle of streptavidin magnetic beads is is based on the extremely strong non-covalent binding ability between streptavidin and biotin. Streptavidin is a tetrameric protein extracted from Streptomyces bacteria, with each subunit capable of binding to a biotin molecule. Functionalized magnetic beads are formed by covalently coupling streptavidin to the surface of magnetic nanoparticles. This technology combines the rapid separation properties of magnetic beads with the high affinity of the streptavidin-biotin system (Kd≈10?1? M) to achieve efficient and specific capture and purification of bio molecules.

一、鏈霉親和素磁珠主要由以下幾部分組成：

1. 磁性核心：這是磁珠的核心部分，通常由鐵、鈷、鎳等磁性金屬或其合金制成。這些材料能夠被外部磁場吸引，從而實現磁珠的快速分離和回收。 

This is the core part of the magnetic beads, usually made of magnetic metals such as iron, cobalt, nickel or their alloys. These materials can be attracted by external magnetic fields, allowing for rapid separation and recovery of magnetic beads.

2. 鏈霉親和素：鏈霉親和素是一種蛋白質，能夠與生物素（biotin）高度特異性結合。生物素是一種小分子化合物，能夠與鏈霉親和素的四個結合位點緊密結合，形成高度穩定的復合物。Streptavidin is a protein that highly specifically binds to biotin. Biotin is a small molecule compound that can bind tightly to the four binding sites of streptavidin to form a highly stable complex.

3. 表面修飾材料：為了提高磁珠的穩定性和功能性，通常需要對磁珠表面進行修飾。常用的表面修飾材料包括聚乙二醇（PEG）、聚丙烯酸酯（PAA）等。這些材料不僅可以增加磁珠的親水性，還可以減少非特異性吸附，提高檢測的靈敏度和特異性。

In order to improve the stability and functionality of magnetic beads, it is usually necessary to modify the surface of the magnetic beads. Commonly used surface modification materials include polyethylene glycol (PEG), polyacrylate (PAA), etc. These materials can not only increase the hydrophilicity of the magnetic beads, but also reduce non-specific adsorption and improve the sensitivity and specificity of detection.

二、鏈霉親和素磁珠核心材料和表面修飾材料的選擇依據

1.磁性核心材料 磁性核心材料的選擇主要考慮以下幾個因素：

 a.磁性能：材料的磁性能（如磁化強度和矯頑力）直接影響磁珠的磁響應性和分離效率。高磁性能的材料能夠產生更強的磁場，從而提高分離速度和效率。

The magnetic properties of materials (such as magnetization and coercivity) directly affect the magnetic responsiveness and separation efficiency of magnetic beads. Materials with high magnetic properties can generate stronger magnetic fields, thereby increasing separation speed and efficiency.

 b.生物相容性：磁性材料必須具有良好的生物相容性，以避免對生物樣本的污染和毒性。鐵、鈷、鎳及其合金是常用的生物相容性材料。

Magnetic materials must have good biocompatibility to avoid contamination and toxicity to biological samples. Iron, cobalt, nickel and their alloys are commonly used biocompatible materials.

c.穩定性：磁性材料需要在各種環境條件下保持穩定性，包括高溫、高壓和酸堿環境。因此，選擇具有高穩定性的材料非常重要。

Magnetic materials need to remain stable under a variety of environmental conditions, including high temperatures, high pressures, and acid-base environments. Therefore, it is important to choose materials with high stability.

2.表面修飾材料 表面修飾材料的選擇主要考慮以下幾個因素：

 a.親水性：修飾材料需要提高磁珠的親水性，使其在水溶液中具有良好的分散性和穩定性。聚乙二醇（PEG）是一種常用的親水性修飾材料。

The modified material needs to improve the hydrophilicity of the magnetic beads so that they have good dispersion and stability in aqueous solutions. Polyethylene glycol (PEG) is a commonly used hydrophilic modification material.

b.減少非特異性吸附：修飾材料應能減少磁珠表面的非特異性吸附，從而提高檢測的特異性和靈敏度。聚丙烯酸酯（PAA）等材料能夠有效減少非特異性吸附。

Modified materials should be able to reduce non-specific adsorption on the surface of magnetic beads, thereby improving the specificity and sensitivity of detection. Materials such as polyacrylate (PAA) can effectively reduce non-specific adsorption.

c.穩定性：修飾材料需要在各種環境條件下保持穩定，不會因pH變化、溫度變化或機械力而脫落。

Modified materials need to remain stable under various environmental conditions and not fall off due to pH changes, temperature changes or mechanical forces.

三.微觀結構及其對性能的影響 鏈霉親和素磁珠的微觀結構對其性能有重要影響。

1.磁珠的微觀結構包括以下幾個部分：

a.磁核：這是磁珠的核心部分，通常為球形或類球形。磁核的尺寸和形狀直接影響磁珠的磁響應性和分離效率。

This is the core part of the magnetic beads, usually spherical or spherical-like. The size and shape of the magnetic core directly affect the magnetic responsiveness and separation efficiency of the magnetic beads.

b.親水性外殼：這是修飾材料形成的外殼，覆蓋在磁核表面。親水性外殼不僅增加了磁珠的親水性，還減少了非特異性吸附。

This is a shell formed by modified materials covering the surface of the magnetic core. The hydrophilic shell not only increases the hydrophilicity of the magnetic beads, but also reduces non-specific adsorption.

c.鏈霉親和素層：這是位于磁珠表面的鏈霉親和素層，負責與生物素結合。鏈霉親和素層的存在使得磁珠能夠特異性地捕獲目標分子。

This is the layer of streptavidin located on the surface of the magnetic beads, which is responsible for binding to biotin. The presence of the streptavidin layer enables the magnetic beads to specifically capture target molecules.

2.微觀結構對性能的影響

a.磁響應性：磁核的尺寸和形狀直接影響磁珠的磁響應性。通常，較大的磁核能夠產生更強的磁場，從而提高分離速度和效率。

The size and shape of the magnetic core directly affect the magnetic responsiveness of the magnetic beads. Generally, larger magnetic cores produce stronger magnetic fields, which increases separation speed and efficiency.

b.親水性和非特異性吸附：親水性外殼的存在顯著提高了磁珠的親水性，減少了非特異性吸附，提高了檢測的特異性和靈敏度。

The presence of the hydrophilic shell significantly improves the hydrophilicity of the magnetic beads, reduces non-specific adsorption, and improves the specificity and sensitivity of detection.

c.結合容量和穩定性：鏈霉親和素層的存在使得磁珠能夠高容量地結合目標分子。同時，鏈霉親和素與生物素的特異性結合具有極高的穩定性，確保了檢測的可靠性。

The presence of the streptavidin layer enables the magnetic beads to bind target molecules with high capacity. At the same time, the specific binding of streptavidin and biotin has extremely high stability, ensuring the reliability of detection.