Metallic Nanoparticles are a focus of intense interest in the field of drug delivery and disease imaging. In fact, various imaging modalities have been developed to utilize metallic compounds or magnetic nanoparticles, such as Fe3O4 and silver particles, as contrast agents. In this blog post, we go in depth on the methods of manufacture and applications of metallic nanoparticles, specifically iron oxide nanoparticles, gold nanoparticles, and silver nanoparticles.
Iron Oxide Nanoparticles
Fe3O4 is an ultrafine, biocompatible, superparamagnetic iron oxide. Superparamagnetic iron oxide nanoparticles (SPIONs), show great promise in the field of enhanced resolution contrast agents (for MRI), in targeted drug delivery (as ligands can be easily conjugated to iron oxide particles), in cell tracking, and in the early detection of cancer, diabetes, and atherosclerosis. The magnetic abilities of SPIONs make them ideal imaging probes for use in magnetic resonance imaging modalities. Their small size allows them to permeate tissue more easily, allowing for visualization not previously possible with older contrast agents. SPIONs are produced via a coprecipitation process, in which iron oxide crystals of various sizes are formed.
Carboxylation is used to attach useful moieties to SPIONs in order to increase the agent’s half-life in circulation or target the NPs to specific tissues. They can easily be conjugated to drugs, proteins, antibodies, or nucleotides. The ability of SPIONs to combine contrast agents with ligands capable of targeting specific tissue types is a big advantage over traditional, nonspecific contrast agents.
Gold Nanoparticles
Colloidal gold, also known as gold nanoparticles, have unique optical properties, modulated by their size and lattice structure, that arise from their interaction with light. The free electrons existing around the positive ion cores in gold NPs can absorb photons (light energy) and undergo oscillations with respect to their underlying lattice structure. This activity has been dubbed localized surface plasmon resonance (LSPR). Absorbed energy is released as light. The absorption and emission spectra of a gold NP is determined by its size as well as its shape.
These physical properties have myriad potential uses in biological imaging and material science, and as such, are currently an area of intense research. The main method of gold NP synthesis involves the reduction of gold salts using citrate to produce monodisperse nanoparticles in the range of 10-20 nm in diameter. The strong affinity of gold allows for easy conjugation of a variety of ligands, such as oligonucleotides, phosphines, and amines, further increasing the potential for development of unique ligands capable of targeting cancer cells more specifically.
Silver Nanoparticles
Silver Nanoparticles typically range between 1 and 100 nm in diameter. Mostly composed of silver oxide compounds, silver NPs have proved to be an effective agent for the treatment of wounds. The LSPR characteristics of silver NPs lend them towards use in molecular labeling. Silver nanoparticles are synthesized by the reduction of silver slats with reducing agents in the presence of a colloidal stabilizer, such as polyvinyl alcohol. The size of silver NPs greatly affects their capabilities, as small 1-10 nm sized particles have been shown in a recent study to attach to and block certain parts of the HIV virus while larger particles did not.
The medley of metal nanoparticles in development today demonstrates the ways in which the physical properties of nanomaterials can be exploited to control and combat disease. Lattice structure, bonding nature, and the characteristics of metal atoms account for a wide range of intersting phenomena that require futher reserach. The unique properties of metals, especially on the nanoscale, have allowed for increased targeting specificity, better imagining of tissues and organs, and many other therapeutic advances.
Refrence:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2996072/#!po=54.2453