Home» Gold Nanoparticles for Cancer Treatment
Nanotechnologies can be defined as the design, characterization, production and application of structures, devices and systems by controlling shape and size at a nanometer scale. In medicine, most interest is in the use of nanoparticles to enhance drug delivery with interest also invitro diagnostics, novel biomaterial design, Bioimaging, therapies and active implants.
AuNPs exhibit unique physicochemical properties including Surface Plasmon resonance (SPR) and the ability to bind amine and thiol groups, allowing surface modification and use in biomedical applications. Nanoparticles functionalization is the subject of intense research at present, with rapid progress being made towards the development of biocompatible, multifunctional particles for use in cancer diagnosis and therapy. For example, a multifunctional micellar hybrid nanoparticles containing metal nanoparticles for MRI detection, quantum dots for near infrared fluorescent imaging, polyethylene glycol (PEG) to increase circulation times, the tumour-specific F3 peptide for targeting and doxorubicin as a therapeutic payload has recently been developed. Efficacy has been demonstrated in vitro and in vivo in a mouse model implanted with human breast cancer cells.
Firstly, AuNPs are considered to be relatively biologically non-reactive and therefore suitable for in vivo applications compared to the very toxic cadmium and silver NPs although various groups are challenging this view. Other advantageous qualities include the strong optical properties of AuNPs due to localized surface Plasmon resonance (LSPR), easily controllable surface chemistry which enables versatility in adding surface functional groups, and lastly, the ease in control over particle size and shape during synthesis. AuNPs may be considered to be fully multifunctional, with the possibility of combining different desired functionalities in one molecular-sized package. All these factors contribute to the strong interest and preference for the use of AuNPs over other NPs.
AuNPs as sensors for probing and imaging tumor cells
AuNPs are good candidates for labelling applications because of their ability to interact strongly with visible light. Upon exposure to light, free electrons in gold atoms are excited to a state of collective oscillation known as surface Plasmon resonance (SPR), conferring gold the ability to absorb and scatter visible light. In labelling applications, AuNPs are targeted and accumulated at the site of interest and based on their optical scattering properties, they enable visualization of the region under study. AuNPs may then be detected by any of the following ways: phase contrast optical microscopy, dark field microscopy, photo thermal imaging, and photo acoustic imaging. In addition, owing to its high atomic weight, AuNPs remain the preferred label for visualization and immuno-staining at the ultra structural level using transmission electron microscopy.
A prominent application of AuNPs is their use as vehicles for delivery of molecules into cells. AuNPs have been described as “promising nanocarriers for therapeutics” owing to their ease of synthesis and functionalization, relative biocompatibility as well as low toxicity in preliminary assays. However, various factors need to be considered in designing an effective drug delivery system. The properties of AuNPs such as their size, charge and surface chemistry have been shown to affect the uptake of AuNPs into cells as well as their subsequent intracellular fate.
In addition, effective drug delivery strategies must take into account the nature of drug-AuNPs interaction (covalent/non-covalent binding) as well as the means of drug release following introduction of the drug-AuNPs complexes to cells. If AuNPs are used solely as carriers into cells, it is also critical to monitor any toxic effects of residual materials in the cell after delivery; a biodegradable NP vector whose lifespan is limited to the therapeutic window of the drug would be ideal. If the NP vector is cleared from the system once its purpose is reached, it will reduce exposure and limit its toxic effects in the body.