Magnetic nanoparticles
[23] The surface of a maghemite or magnetite magnetic nanoparticle is relatively inert and does not usually allow strong covalent bonds with functionalization molecules.
[30] Nanoparticles with a magnetic core consisting either of elementary Iron or Cobalt with a nonreactive shell made of graphene have been synthesized recently.
The size, shape, and composition of the magnetic nanoparticles very much depends on the type of salts used (e.g.chlorides, sulfates, nitrates), the Fe2+/Fe3+ ratio, the reaction temperature, the pH value and ionic strength of the media,[21] and the mixing rate with the base solution used to provoke the precipitation.
[33] The co-precipitation approach has been used extensively to produce ferrite nanoparticles of controlled sizes and magnetic properties.
[34][35][36][37] A variety of experimental arrangements have been reported to facilitate continuous and large–scale co–precipitation of magnetic particles by rapid mixing.
[40] Magnetic nanocrystals with smaller size can essentially be synthesized through the thermal decomposition of alkaline organometallic compounds in high-boiling organic solvents containing stabilizing surfactants.
Sullivan at al. developed a one-pot microwave method that allows the magnetic nanoparticles to be produced and functionalised with glutaraldehyde, at the same time.
[43] Using the microemulsion technique, metallic cobalt, cobalt/platinum alloys, and gold-coated cobalt/platinum nanoparticles have been synthesized in reverse micelles of cetyltrimethlyammonium bromide, using 1-butanol as the cosurfactant and octane as the oil phase.,[21][44] Using flame spray pyrolysis [31][45] and varying the reaction conditions, oxides, metal or carbon coated nanoparticles are produced at a rate of > 30 g/h .
Despite research efforts, however, the accumulation of nanoparticles inside of cancer tumors of all types is sub-optimal, even with affinity ligands.
[49] The challenge of accumulating large amounts of nanoparticles inside of tumors is arguably the biggest obstacle facing nanomedicine in general.
Iron oxide particles have been used for the detection of Gram negative bacteria like Escherichia coli and for detection of Gram positive bacteria like Streptococcus suis[52][53] Core-shell magnetic nanoparticles, particularly cobalt ferrite, possess antimicrobial properties against hazardous prokaryotic (E. coli, Staphylococcus aureus) and eukaryotic (Candida parapsilosis, Candida albicans) microorganisms.
It is known that the size of the magnetic nanoparticles performs a critical role, as the smaller the particles, the more significant the antimicrobial effect.
This assay involves the specific binding of an antibody to its antigen, where a magnetic label is conjugated to one element of the pair.
Coated-magnetic nanoparticles have a key aspect in electrochemical sensing not only because it facilitates the collecting of analyte but also it allows MNPs to be part of the sensor transduction mechanism.
[62] The immobilization of enzymes on inexpensive, non-toxic and easily synthesized iron magnetic nanoparticles (MNP) has shown great promise due to more stable proteins, better product yield, ease of protein purification and multiple usage as a result of their magnetic susceptibility.
[64] This technology is potentially relevant to cellular labelling/cell separation, detoxification of biological fluids, tissue repair, drug delivery, magnetic resonance imaging, hyperthermia and magnetofection.
[65] Random versus site-directed enzyme immobilization Enzymes immobilized on magnetic nanoparticles (MNP) via random multipoint attachment, result in a heterogeneous protein population with reduced activity due to restriction of substrate access to the active site.
Immobilizing the catalytic center on top of nanoparticles with a large surface to volume ratio addresses this problem.
[72] Magnetic CoPt nanoparticles are being used as an MRI contrast agent for transplanted neural stem cell detection.
These nanoparticles produce heat that typically increases tumor temperature to 40-46 °C, which can kill cancer cells.
[75][76][77] Another major potential of magnetic nanoparticles is the ability to combine heat (hyperthermia) and drug release for a cancer treatment.
Numerous studies have shown particle constructs that can be loaded with a drug cargo and magnetic nanoparticles.
[78] The most prevalent construct is the "Magnetoliposome", which is a liposome with magnetic nanoparticles typically embedded in the lipid bilayer.
If it's possible to modify the MNPs at this small scale, the information density that can be achieved with this media could easily surpass 1 Terabyte per square inch.
