What are they?
Metal nanoparticles are microscopic colloids of metal and substrate combined either by wet chemistry, physical chemistry, or by a biological approach. These metal nanoparticles, as far as the medical/ pharmacological community is concerned, come in three major flavors, Silver, Gold and Ferrite – each metal possesses unique properties and potential uses. Silver and Gold nanoparticles are specifically intriguing for their antimicrobial and anticancer potentials (antimicrobial discussion below). Nanoparticles achieve these various properties not only through the substrate attached to them but also their size and shape; generally, smaller nanoparticles with large surface areas tend to have higher antimicrobial activity. The sizes range from ~ 1nm to over 200nm, with three basic shapes, Icosahedron, Face-centered cubic, and Decahedron.
A brief Wiki, a review is below: Nanomaterials
Why?
Gold and Silver Nanoparticles (GNPs & SNPs) have become increasingly popular due to their potential therapeutic use. Currently, there is research to streamline bio-friendly synthesis processes, test toxicity on various infectious agents and cell types, and evaluate the mechanism by which they control malignant cellular and microbial growth.
Synthesis
Vivek D. Badwaik et al recently published a new method for GNP synthesis that involves reducing and capping of Au3+ ions by various concentrations of Dextrose in aqueous solution. In contrast previous methods employed the use of chemicals, such as hydrogen tetrachloroaurate (III) hydrate or poly (N-vinyl-2-pyrrolidone (PVP). Three major points of consideration in the efforts to mass produce nanoparticles: 1) how hazardous is the process (ie, toxicity of chemicals and by products, potential for environmental contamination, etc…), 2) quality, reproducibility and conformity of the product, and 3) resources, feasibility and flexibility of the nanoparticle production process (ie, how conducive is it to substrate substitution, concentrations of chemicals and time necessary for production etc…)
Antimicrobial
As multidrug resistant bacteria strains and nosocomial infections rise a new emphasis has been placed on developing innovative means to control and treat these infectious agents.
GNPs and SNPs might provide the solution. Recent studies have demonstrated that SNP coated implantable devices, as well as fabrics have antimicrobial activity – even against pathogens like Staphylococcus aureu and Klebsiella pneumoniae. However, SNPs have a major flaw, as they are toxic towards healthy cells, and thus, leaving their role as potential anticancer therapeutics quite intriguing.
On the other hand, GNPs have recently gotten more air time, if you will, because of their comparable antimicrobial activity and decreased toxicity. GNPs seem to function much in the same manner as SNPs at preventing or diminishing microbial growth by affecting cell membrane charge/integrity, binding intracellular enzymes or inhibiting cellular components- however, a general mechanism for toxicity is still elusive. There has been some speculation that the method of toxicity is also dependent upon the GNPs bound substrate and the nature of the pathogen.
The following is an excellent in depth look at some of the topics mentioned above:
Khan, A.U., Medicine at nanoscale: a new horizon. Int J Nanomedicine, 2012. 7: p. 2997-8.
Learn more from…
1. Badwaik, V.D., et al., Single-step biofriendly synthesis of surface modifiable, near-spherical gold nanoparticles for applications in biological detection and catalysis. Langmuir, 2011. 27(9): p. 5549-54.
2. Bhattacharyya, K., et al., Gold nanoparticle-mediated detection of circulating cancer cells. Clin Lab Med, 2012. 32(1): p. 89-101.
3. Chen, M., et al., Antimicrobial activity and the mechanism of silver nanoparticle thermosensitive gel. Int J Nanomedicine, 2011. 6: p. 2873-7.
4. Friedman, A., et al., Susceptibility of Gram-positive and -negative bacteria to novel nitric oxide-releasing nanoparticle technology. Virulence, 2011. 2(3): p. 217-21.
5. Sweet, M.J., A. Chesser, and I. Singleton, Review: metal-based nanoparticles; size, function, and areas for advancement in applied microbiology. Adv Appl Microbiol, 2012. 80: p. 113-42.
6. Thubagere, A. and B.M. Reinhard, Nanoparticle-induced apoptosis propagates through hydrogen-peroxide-mediated bystander killing: insights from a human intestinal epithelium in vitro model. ACS Nano, 2010. 4(7): p. 3611-22.
7. Ma, X., et al., Gold nanoparticles induce autophagosome accumulation through size-dependent nanoparticle uptake and lysosome impairment. ACS Nano, 2011. 5(11): p. 8629-39.
8. Youngs, W.J., et al., Nanoparticle encapsulated silver carbene complexes and their antimicrobial and anticancer properties: a perspective. Dalton Trans, 2012. 41(2): p. 327-36.
