Gold Nanoparticles in Cancer Diagnosis and Treatment: A Review

Review Article

Austin J Biotechnol Bioeng. 2014;1(6): 5.

Gold Nanoparticles in Cancer Diagnosis and Treatment: A Review

Faheem SM* and Hussaina Banu

Manipal University Dubai Campus, UAE

*Corresponding author: Faheem SM, Manipal University, Academic City, P.O.B 345050, Dubai, U.A.E.

Received: September 30, 2014; Accepted: November 01, 2014; Published: November 03, 2014

Abstract

Nanoparticles are increasingly becoming indispensable tool of modern day research in almost every field of science. Application of gold nanoparticles, particularly, in cancer imaging and therapy is notably promising through the recent surge of scientific communications from all around the world. Apart from being biocompatible and non-toxic, surface plasmon resonance enhanced light scattering and absorption, and their ability to convert absorbed light into localized heat makes them more suitable as agents for photothermal cancer therapy resulting in thermal ablation of the cancer cells. Moreover, the high surface-to-volume ratio of the gold nanoparticle supports the bio-functionalization of their surface with ligands that can specifically target the cancer cells and also with biocompatible polymers, making them more suitable for in vivo applications. This review focusses on overview of characteristic features, synthesis and potential applications of gold nanoparticles in cancer therapy and diagnosis.

Keywords: Gold Nanoparticles; Surface plasmon resonance; Cancer therapy; Hyperthermia; Drug delivery

Abbreviations

GNP: Gold Nanoparticles; DOX: Doxorubicin; PEG: Poly Ethylene Glycol; aHFR: Alpha Human Folate Receptor; NIR: Near Infra-Red; EGFR: Epidermal Growth Factor Receptor; MPEG-SH: Thiolatedmethoxy Polyethylene Glycol; MTG: Methyl ThioGlycolate

Introduction

Gold Nanoparticles (GNPs) are known for their unique optical & electronic properties. They produce vibrant colors upon interaction with visible light and thus were used by artisans in the past centuries. Gold nanoparticles have proved to be versatile for a range of applications with well characterized physical and electronic properties. Moreover, their surface chemistry can be easily modified. Their large surface area to volume ratio enables surface coating with a variety of molecules including therapeutics and target agents. The optical and electronic properties of gold nanoparticles are tunable by changing the size, shape, surface chemistry, or aggregation state. One of the unique properties exhibited by GNPs is surface plasmon resonance enhanced light scattering and absorption, which can be customized by varying the size or shape of the nanoparticles for different applications [1,2]. These features have made gold nanoparticles one of the most widely used nanomaterials for academic research. In recent years, GNPs have been researched for medical applications as therapeutic and drug delivery agents. Here, we have attempted to review synthesis and promising applications of GNPs in chemotherapy of cancer highlighting in-vitro efficacy studies in the recent times.

Synthesis

GNPs are synthesized using physical, chemical and biological methods. Nevertheless, synthesis of GNPs by the conversion of metallic gold into nanoparticulate gold by chemical reduction is the most popularly used method. For synthesizing stable and size controlled GNPs, various chemical methods such as sodium citrate mediated reduction described by Turkevich(1951) and Frens(1973); and sodium borohydride mediated reduction method (Brustand Schriffin; 1994) have been employed [3-5]. However, seed mediated growthproposed by Schmid et al (1996) is the widely used chemical method of synthesizing GNPs [6]. Similarly, seed-mediated growth methods by Murphy et al (2001) and Nikoobakht& El-Sayed (2003) arequite common for the chemical synthesis of gold nanorods. Although, several chemical methods have been successfully employed for the synthesis of various gold nanostructures, their toxicity limits their application in medicine [7,8]. Therefore, eco-friendly (green chemistry) and non-toxic biological or biomimetic methods have been widely considered for synthesis.

Several attempts had been made to synthesize GNPs of fairly uniform size and shape using plant extracts and extracellular microbial extracts [9]. Sastry et al reported the synthesis of GNPs using three different microbes, namely fungus Fusariumoxysporum, fungus Verticillium sp. and actinomycete Thermomonosporasp [10-12]. Biosynthesis of metal and semiconductor nanoparticles using microorganisms has emerged as a more ecofriendly, simpler, and more reproducible alternative to chemical synthesis, allowing the generation of rare forms such as triangles. Use of fungus Helminthosporumsolani, when incubated with an aqueous solution of chloroaurate ions, produced a mixture of extracellular gold nanocrystals in diverse shape and size. These smallest separated gold nanoparticles when conjugated to Doxorubicin (DOX) demonstrated efficient uptake and cytotoxicity in HEK293 cells [13].

Similarly GNPs of various shape and size can be synthesized in a controlled manner using plant extracts, where the bioreduction of gold ions to GNPs occurs on account of the pharmaceutically active biomolecules such as alkaloids, phenolic compounds, and terpenoidspresent in them [14,15]. For instance, stem extracts of Cassia fistula of Leguminosae family and leaf extracts of tropical almond tree (Terminalia catappa), rose plant (Rosa rugosa), Magnolia kobustree and persimmon (Diopyros kaki)were used for the synthesis of gold nanoparticles;rose geranium plant (Pelargonium graveolens) extract was used to synthesize decahedral and icosahedral shaped gold nanoparticles; lemon grass (Cymbopogonflexuosus) extract has been used to synthesize gold nanostructures of various shapes, namely gold nanospheres and gold nanotriangles; neem (Azadirachtaindica) extract used to synthesize gold triangles and hexagons; sugar beet pulp was used to synthesize gold nanowires; and Aloe vera plant extract for synthesizing gold nanotriangles [16-24]. All of these biosynthetic methods were highly reproducible and are relatively non-toxic (Figure 1).

Citation: Faheem SM and Banu H. Gold Nanoparticles in Cancer Diagnosis and Treatment: A Review. Austin J Biotechnol Bioeng. 2014;1(6): 5. ISSN: 2378-3036