Characterization of Colloidal Antibacterial Activity

Our Characterization Range

Because of their unique properties and morphology, colloidal nanoparticles can be prepared into antimicrobial agents with a high degree of control. Their nanotoxicity and highly developed surface area enhance their antibacterial effect. Fig.1 presents the general mechanism of the antibacterial effect of silver nanoparticles. Alfa Chemistry can provide antimicrobial characterization services for metal oxide nanoparticles (such as ZnO, MgO, CuO, Cu₂O, Al₂O₃, TiO₂, CeO₂ and Y₂O₃), metal nanoparticles (such as copper, silver, gold, etc.), metal hydroxide such as Mg(OH)₂, and antibacterial-loaded colloids made of biodegradable materials such as chitosan, lignin, and dextran, among others.

Fig.1 General mechanisms for antimicrobial mode of action of silver nanoparticles.^[1]

Our Solutions

Our antimicrobial performance characterization services include, but are not limited to:

• Characterization of antibacterial activity

We tested the antibacterial activity of the samples by agar diffusion method and photonephelometric method. The former is mainly to co-culture the colloidal sample solution and the strain on sterile solid agar plates, and to characterize the antibacterial activity by measuring the inhibition zone. In the latter, the colloidal sample and bacterial suspension are added to the liquid medium for co-cultivation at a constant temperature, and the characterization is completed by testing the absorbance with a UV-visible spectrophotometer.

Fig. 2 Antibacterial activity of polyaniline/Pt-Pd nanocomposites.^[3]

• Minimum inhibitory concentration and minimum bactericidal concentration evaluation

We determined the minimum inhibitory concentration and minimum bactericidal concentration of the samples using the broth microdilution method. The specific method is:

1. Prepare a series of colloidal sample solutions with a concentration gradient and transfer them to a microtiter plate;

2. Add an equal amount of freshly prepared microbial suspension to each well and incubate for a period of time;

3. Take the quantitative medium from the microtiter plate and inoculate it on the nutrient agar plate, and observe the results after incubating for a period of time.

The lowest colloid concentration that completely inhibits bacterial growth is the minimum inhibitory concentration, and the lowest concentration of colloid that completely kills the inoculated bacterial strain is the lowest bactericidal concentration.

Types of Bacteria

According to the different application fields of colloids, the types of bacteria used to characterize the antibacterial activity are different. The following shows some of the types of bacteria we can provide for characterization:

• Cosmetic field: Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, mold, Salmonella, etc.
• Agricultural field: Bacillus licheniformis, Bacillus subtilis, Bifidobacterium bifidum, etc.
• Food field: Hemolytic Streptococcus, Campylobacter jejuni, Yersinia enterocolitica, Shigella, Escherichia coli, etc.

References

1. Roy A, et al. Green synthesis of silver nanoparticles: biomolecule-nanoparticle organizations targeting antimicrobial activity. RSC Advances. 2019, 9(5):2673-2702.
2. Halbus A F, et al. Colloid particle formulations for antimicrobial applications. Advances in Colloid and Interface Science. 2017:134-148.
3. Pandi Boomi, et al. Synthesis, characterization and antibacterial activity of polyaniline/Pt–Pd nanocomposite. European Journal of Medicinal Chemistry. 2014, 72(3):18-25.
4. Biao L, et al. Synthesis, characterization and antibacterial study on the chitosan-functionalized Ag nanoparticles. Materials Science and Engineering: C. 2017, 76(7):73-80.

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