Product Selection Guide
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How to Choose the Appropriate Magnetic Beads

Alpha Biobeads provides superparamagnetic beads with sizes range from 50 nm to 1 µm. These beads could be modified by different functional groups or ligands to fit different purposes. Several key factors may be considered before choosing the appropriate beads.

Which magnetic beads have the lowest non-specific binding?

     All the magnetic beads offered by Alpha Biobeads are pre-blocked with a layer of covalently bonded BSA. This layer of covalently bonded BSA makes our magnetic beads an ideal platform for ligands immobilization with significantly low non-specific binding. No blocking steps are needed to reduce the non-specific binding from Alpha Biobeads’s magnetic beads.

How do I choose the right size magnetic beads?

     The time it takes for the magnetic beads to settle and to be separated are the most frequently considered factors for researchers when it comes down to choosing the right size magnetic beads. Overall, the separation time will decrease with the increase of particle size. However, the time for settlement will also decrease with the increase of particle size. Table 1 summarizes the separation time and settlement time of the magnetic beads offered by Alpha Biobeads. 

         If the long settlement time is a required characteristic for certain applications, such as assay development, the magnetic beads with size range from 100 nm to 200 nm will be the ideal choice. The damage of isolated targets may be a concern for certain applications, such as cell separation. In this case, magnetic beads with a size range from 100 nm to 200 nm will be the ideal candidates. However, in several applications such as protein or nucleic acid isolation, the separation time becomes the most important factor to be considered. In that case, magnetic beads with large size (1 µm) will become the best choice even if the magnetic beads with smaller size have higher binding capacity.

Name of Beads Separation Time Settlement Time
Super Mag 50 nm 2 to 8 hours > 6 Months
Super Mag 75 nm 10 to 20 minutes > 6 Months
Super Mag 100 nm 5 to 10 minutes 30 days
Super Mag 150 nm 2 to 5 minutes 16 days
Super Mag 200 nm 1 to 2 minutes 7 days
Mono Mag 500 nm 1 to 2 minutes 24 hours
Mono Mag 1 µm < 1 minute 6 hours
Hi-Sur Mag 1 µm 1 to 2 minutes 12 hours

 How do I choose magnetic beads for chemiluminescence enzyme immunoassay (CLEIA) and enzyme immunoassays (EIA)? 

      Most of the commercially available magnetic beads are manufactured with iron oxide exposure even if there is no iron or iron oxide leaking. The exposed iron oxide can function like horseradish peroxidase, and thus decompose hydrogen peroxide and oxidize substances such as TMB substrate to yield color change. Consequently, magnetic beads with exposed iron oxide will generate signal even when there is no analyte and subsequently increase the background noise level.

         Alpha Biobeads’s Mono Mag series products (0.5 and 1 µm) are designed to fit the needs of these assays. For all the Mono Mag products, the iron oxide is sealed from the outer environment by a hydrophobic layer coating. There is no iron oxide exposure in Mono Mag beads.

Magnetic Beads

Alpha Biobeads provides two different types of magnetic beads with 1 µm in diameter (Mono Mag 1 µm Vs Hi-Sur Mag 1 µm). Which one is better for my experiments?

       In the last section, we mentioned that all the Mono Mag series have a layer of hydrophobic coating to isolate the iron oxide from the outer environment. There are no exposed iron oxide in Mono Mag beads. However, there are exposed iron oxide in the Hi-Sur Mag. The other differences between Mono Mag 1 µm and Hi-Sur Mag 1 µm are their size distributions and surface areas. Mono Mag 1 µm has very narrow size distribution (CV<5%, see Figure 1). The surface area of Hi-Sur Mag 1 µm is around four times larger than that of the same weight of Mono Mag 1 µm. As a result, Hi-Sur Mag has higher binding capacity for both protein and nucleic acid than Mono Mag. In addition, other than 1 µm Mono Mag beads, we also offer 500 nm Mono Mag beads.