A nanoparticle (NP) is an ultrafine unit with dimensions measured in nanometres (nm; 1 nm = 10−9 metre). Nanoparticles exist in the natural world and are also created as a result of human activities. Because of their sub-microscopic size, they have unique material characteristics, and manufactured nanoparticles may find practical applications in a variety of areas. The small size of nanoparticles is especially advantageous in medicine; nanoparticles can not only circulate widely throughout the body but also enter cells or be designed to bind to specific cells. Those properties have enabled new ways of enhancing images of organs as well as tumours and other diseased tissues in the body. Some examples of NP used for medical purposes are metallic NP, carbon nanotube, liposome, gold NP, silica NP and many more.
The massive use of nanomaterials in biomedical applications enhanced research interest to explore the antibacterial mechanisms of NPs. NPs can alter the metabolic activity of bacteria by maintaining contact with bacterial cells via electrostatic interaction, Van der Waals forces, receptor-ligand and hydrophobic interactions. Further, these NPs can cross the bacterial membrane and assemble along the metabolic pathway influencing the shape and functioning of the cell membrane. Finally, NPs interact with the bacterial cell basic components causing oxidative stress, permeability and gene expression changes, diverse alterations, electrolyte balance disorders, protein deactivation, and enzyme inhibition
These NPs work on a bacterial cell in three ways, they are as follows:
Dissolved metal ions: Metal oxide NPs release metal ions and these metal ions are absorbed through the cell membrane. Each metal ion has its sensitivity to different microorganisms. For instance, Ag+ ions react with the sulfhydryl group in enzymes and other cellular constituents leading to cellular dysfunction. Ag+ also prevents cell wall synthesis in Gram-positive bacteria. Ag+ ions can also interact with DNA inhibiting the growth by obstructing DNA replication and cell division.
Reactive oxygen species: The toxicity of nanomaterial can be mainly attributed to the production of reactive oxygen species ROS that inhibits bacterial growth by restricting amino acid synthesis, lipid peroxidation and DNA replication. The presence of NPS excessive production of ROS leads to an unbalanced state, which results in oxidative stress, creating damage to the basic individual components of bacterial cells. ROS namely Superoxide radical, hydroxyl radical, hydrogen peroxide that is generated by different levels of activity and toxicity.
Direct contact / Non-oxidative mechanism: The non-oxidative mechanism involves direct interaction on NPs with the cell wall. Direct contact is often but not in all cases a necessary mechanism of toxicity. Direct contact inhibits enzymes and proteins involved in cell metabolism, thus disrupting the normal functioning of the bacterial cell.
Nanoparticles can be used as tags or labels, which will help us in the detection of infectious agents even in small sample volumes directly in a very specific, sensitive and rapid format with lower costs than current in-use technologies. Also, the earlier detections will help in accurate and prompt treatment of the disease. however, nanoparticles that are used in nanomedicines can travel through a mother’s placenta and can assist in the formation of free radicals.
•Asian Journal of Pharmaceutical Sciences, Vol. 15, Issue 1, January 2020, pages 42-59https://doi.org/10.1016/j.ajps.2019.03.002
Ashish Ranjan, Nikorn Pothayee, Mohamed N. Seleem, Stephen M. Boyle, Ramanathan Kasimanickam, Judy S. Riffle, Nammalwar Sriranganathan, Nanomedicine for intracellular therapy, FEMS Microbiology Letters, Volume 332, Issue 1, July 2012, Pages 1–9, https://doi.org/10.1111/j.1574-6968.2012.02566.x