Latex Microspheres

Latex microspheres are spherical particles in the colloidal size range, formed by amorphous polymers such as polystyrene. The particle size of latex microspheres is usually between 1 micron and 100 microns, but can also be customized as needed. The surface of latex microspheres can be chemically modified to change its surface properties, such as surface charge, hydrophilicity or hydrophobicity.

SHBC Polystyrene latex microspheres (PS microspheres)

Base materials of latex microspheres

The base material of latex microspheres is polymers, and commonly used polymers include polystyrene, polypropylene, polyethylene, polyamide, polyester, etc.

The choice of polymer depends on the specific application requirements of latex microspheres.

Polystyrene microspheres have good hydrophobicity and are suitable for adsorption of water-soluble substances;

Polypropylene microspheres have good chemical resistance and are suitable for catalysis, adsorption and other applications;

Polyethylene microspheres have good biocompatibility and are suitable for biomedical applications.

Application of latex microspheres

Classification by industry:

1. Biochemistry and molecular biology: used for protein purification, enzyme catalysis, immunoassay, etc.
2. Materials science: used for polymer coating, nanomaterial preparation, etc.
3. Chemistry: used for catalysis, adsorption, separation, etc.

Specific applications:

1. Latex immunoturbidimetry: used to detect antigens or antibodies in serum
2. Immunoprecipitation: used to detect interactions between proteins
3. Lateral chromatography: used to analyze the size, shape and charge of proteins
4. Nucleic acid separation: used to separate DNA or RNA
5. Enzyme catalysis: used to improve the activity and stability of enzymes
6. Polymer coating: used to improve the surface properties of materials
7. Nanomaterial preparation: used to prepare nanoparticles, nanocomposites, etc.

Application examples：

1. Latex immunoturbidimetry: Latex immunoturbidimetry is a method of detecting diseases using the immunoprecipitation principle oflatex microspheres.In this method, specific antibodies are attached to latex microspheres. When the corresponding antigen is present in the sample to be tested, the antigen binds to the antibody to form an immune complex. The immune complex will precipitate on the surface of the latex microspheres, causing the particle size and refractive index of the latex microspheres to change. By detecting the particle size and refractive index of the latex microspheres, it can be determined whether the antigen exists in the sample to be tested.
2. Drug-loaded microspheres:Drug-loaded microspheres refer to microspheres that encapsulate drugs or therapeutic agents inlatex microspheres. Drug-loaded microspheres can transport drugs or therapeutic agents to specific sites to achieve the purpose of treatment. For example, drug-loaded microspheres can be used to transport anti-tumor drugs to tumor sites to achieve tumor treatment.
3. Immunotherapy microspheres: Immunotherapy microspheres refer to microspheres that encapsulate antibodies or other immune cells in latex microspheres. Immunotherapy microspheres can transport antibodies or immune cells to specific sites to achieve the purpose of immunotherapy. For example, immunotherapy microspheres can be used to transport antibodies to tumor sites and release antibodies at tumor sites to achieve tumor treatment.

Frequently Asked Questions about Latex Microspheres

1. How to choose the particle size of latex microspheres?

Generally, if you choose latex microspheres with small particle size, you need more antibodies, and the precision and linearity are relatively good; if you choose latex microspheres with large particle size, you need less antibodies, and the precision and linearity are relatively poor. Compared with small particle size, large particle size has better sensitivity.

2. What is the approximate concentration of microspheres in general?

In the entire measurement system, the concentration of microspheres is about 0.01%, which is more related to the linearity specified by the reagent itself.

3. Before the protein (antibody) is coupled to the microspheres, the longer the microspheres are activated, the better the efficiency?

It needs to be analyzed according to the experimental situation. For example, the activation time of acid-based microspheres is very short, generally 10-20 minutes is appropriate, and long-term activation will reduce the coupling efficiency.

4. When using the centrifugal method to couple latex microspheres, what is the general centrifugal force required?

The centrifugal force is related to the particle size of the latex microspheres used. Generally, microspheres with a particle size of about 70nm require about 13000g/min centrifugation for more than 30 min. The smaller the particle size, the longer the time required and the greater the centrifugal force.

5. The protein cannot be adsorbed onto the microspheres?

It can be improved through a variety of methods. For example, adding more protein: removing the microsphere surfactant to release its protein binding site: introducing an intermediate to connect the microspheres to the protein; changing the buffer, etc.

6. A large amount of protein was added during labeling, but it is still inactive?

You can try to change the amount of protein added to change the spatial conformation of the protein binding to the microspheres; use epitope diluents to occupy some of the protein binding sites on the microspheres to prevent the proteins from getting too close.

7. After the latex microspheres were coupled with antibodies, no agglutination was found at the time, but agglutination was found overnight. What is the reason? How to control and avoid it?

This situation is generally caused by low coupling efficiency. When there is insufficient protein in the system or other reasons, there are still many reactive groups on the surface of the microspheres after cross-linking. These groups can react with the proteins on the connected microspheres, resulting in aggregation. This can be solved by adding some blocking agents such as BSA. In addition, the cross-linking rate of the microspheres can also be increased. Agglutination occurs after a period of time because after the microspheres are coupled to the proteins, they are relatively stable (so they can exist in a colloid-like state) because they carry the same charge relationship. They can only combine when they occasionally collide with each other and encounter each other’s reactive groups.

8. How to control and avoid the self-aggregation of latex microspheres?

The self-aggregation is related to many factors, such as high electrolyte concentration, neutralization of surface valence charge, or being placed in certain unfavorable environments (when blood is frozen).

1) When the electrolyte concentration rises to a certain level, the surface negative charge is masked, and the latex microspheres come into contact and agglutinate, so high ionic strength buffer solutions cannot be used, and the buffer solution concentration should generally not exceed 50mM.

2) For negatively charged latex microspheres, positively charged buffer solutions (such as Tris buffer solutions) cannot be used.

3) During long-term storage, the pH of the suspension medium should be maintained at least 1-2 pH units higher than the pKa value of the surface group of the latex microspheres.

4) High-concentration latex microspheres are prone to cause colloid instability, so the concentration of it should be low, and it should not be frozen, otherwise they will agglutinate.

5) During coupling, add the microspheres to the protein solution instead of adding the protein to the microspheres.

6) During coupling, oscillation speeds up the reaction. In short, the principle is to reduce the chance of contact with other microspheres under high ionic strength before coupling the microspheres with proteins.

9. Why is the immediate detection effect very good after the antibody is coupled to the base microspheres, but the antibody activity decreases after being placed at 37°C for 2 days?

1) Latex microspheres contain surfactants, which cause it to self-condense, which can be observed under a microscope. It can be cleaned before coupling to avoid aggregation of coupled latex microspheres.

2) If the antibody activity is inactivated by covalent reaction, the common reason is poor antibody quality or expired reagents. You can check whether the reagents are contaminated, whether there is free-flowing white powder, continuous clumps, etc. in the reagents to judge.

10. What is the reason why the latex microspheres react with antigens after coupling antibodies, but the effect is not obvious?

1) The antigen and antibody do not match: 2) The amount of coated antibody is insufficient: 3) Although the amount of antibody used is large, the coupling efficiency is low.

11. How to store latex microspheres to ensure high stability?

1) Lower the storage temperature to 2~8℃;

2) Reduce the concentration of blocking agent in the storage solution to prevent the antibody from being replaced；

3) Confirm that there are no impurities in the storage solution that can compete with the antibody to prevent long-term replacement of the antibody；

4) Use low-concentration buffer for storage, such as MOPSO, MES, HEPES, etc.