Silver nanoparticle
The properties of silver nanoparticles applicable to human treatments are under investigation in laboratory and animal studies, assessing potential efficacy, biosafety, and biodistribution.
[5] The most common capping ligands are trisodium citrate and polyvinylpyrrolidone (PVP), but many others are also used in varying conditions to synthesize particles with particular sizes, shapes, and surface properties.
In this method, the citrate ion traditionally acts as both the reducing agent and the capping ligand,[19] making it a useful process for AgNP production due to its relative ease and short reaction time.
Some of these surface stabilizing species are: NaBH4 in large amounts,[20] poly(vinyl pyrrolidone) (PVP),[22] sodium dodecyl sulfate (SDS),[20][22] and/or dodecanethiol.
[9][28] Seed-mediated growth is a synthetic method in which small, stable nuclei are grown in a separate chemical environment to a desired size and shape.
There are a few competing mechanisms which may result in the decrease in nanoparticle size; destruction of NPs upon collision, sputtering of the sample surface, particle fusion upon heating and dissociation.
High temperature conditions during the initial stages of implantation will increase the impurity diffusion in the substrate and as a result limit the impinging ion saturation, which is required for nanoparticle nucleation.
[41] Both the implant temperature and ion beam current density are crucial to control in order to obtain a monodisperse nanoparticle size and depth distribution.
The biological synthesis of nanoparticles has provided a means for improved techniques compared to the traditional methods that call for the use of harmful reducing agents like sodium borohydride.
[42][43][44] The problems with the chemical production of silver nanoparticles is usually involves high cost and the longevity of the particles is short lived due to aggregation.
[45][46] In addition, precise control over shape and size is vital during nanoparticle synthesis since the NPs therapeutic properties are intimately dependent on such factors.
This provides a means to develop biomolecules that can synthesize AgNPs of varying shapes and sizes in high yield, which is at the forefront of current challenges in nanoparticle synthesis.
[1] Stirring for twelve hours results in the silica shell being formed consisting of a surrounding layer of silicon oxide with an ether linkage available to add functionality.
[63] NIST RM 8017 contains 75 nm silver nanoparticles embedded in a cake of the polymer polyvinylpyrrolidone to stabilize them against oxidation for a long shelf life.
Although the most common applications are for medicinal or antibacterial purposes, silver nanoparticles have been demonstrated to show catalytic redox properties for dyes, benzene, and carbon monoxide.
[67] The support plays virtually no role in the catalytic ability and serves as a method of preventing coalescence of the silver nanoparticles in colloidal solution.
[67] Without the silver nanoparticle catalyst, virtually no reaction occurs between sodium borohydride and the various dyes: methylene blue, eosin, and rose bengal.
The important feature of silver nanostructures that are enabling for photocatalysis is their nature to create resonant surface plasmons from light in the visible range.
[70] Researchers have explored the use of silver nanoparticles as carriers for delivering various payloads such as small drug molecules or large biomolecules to specific targets.
[74][75] Recent chemotherapeutic applications have designed anti cancer drugs with a photo cleavable linker,[76] such as an ortho-nitrobenzyl bridge, attaching it to the substrate on the nanoparticle surface.
[74][75] A second approach is to attach a chemotherapeutic drug directly to the functionalized surface of the silver nanoparticle combined with a nucelophilic species to undergo a displacement reaction.
[81] A pitfall of the commonly used nano-drug delivery systems is that free drugs that are released from the nanocarriers into the cytosol get exposed to the MDR transporters once again, and are exported.
To solve this, 8 nm nanocrystalline silver particles were modified by the addition of trans-activating transcriptional activator (TAT), derived from the HIV-1 virus, which acts as a cell-penetrating peptide (CPP).
[citation needed] Silver nanoparticles have been shown to have synergistic antibacterial activity with commonly used antibiotics such as; penicillin G, ampicillin, erythromycin, clindamycin, and vancomycin against E. coli and S.
[89] This antibacterial synergy between silver nanoparticles and hydrogen peroxide can be possibly attributed to a Fenton-like reaction that generates highly reactive oxygen species such as hydroxyl radicals.
[101] Samsung has described the system: [A] grapefruit-sized device alongside the [washer] tub uses electrical currents to nanoshave two silver plates the size of large chewing gum sticks.
[100][101] When clothes are run through the cycle, the intended mode of action is that bacteria contained in the water are sterilized as they interact with the silver present in the washing tub.
[99] The washing machines being developed by Samsung do contain a pesticide and have to be registered and tested for safety under the law, particularly the U.S. Federal Insecticide, Fungicide, and Rodenticide Act.
[104] The U.S. National Institute for Occupational Safety and Health derived a recommended exposure limit (REL) for silver nanomaterials (with <100 nm primary particle size) of 0.9 μg/m3 as an airborne respirable 8-hour time-weighted average (TWA) concentration.
[107] Nano-silver applied to tissue-cultured human cells leads to the formation of free radicals, raising concerns of potential health risks.
