Research Article DIAGNOSTICS AND THERAPEUTIC APPLICATION OF GOLD NANOPARTICLES RAGHAVENDRA R. , KANTHADEIVI ARUNACHALAM*, SATHESH KUMAR ANNAMALAI, AARRTHY M. ARUNACHALAM, Center for Environmental Nuclear Research, Directorate of Research, SRM University, Chennai,Tamil Nadu, India- 603203, Kaplan University, Washington DC, USA. Email: kanthad.arunachalam@gmail.com Received: 29 Nov, 2013 Revised and Accepted: 20 Dec 2013 ABSTRACT Recent years with advancement in the synthesis of a variety of nanomaterials, it has become a surge of interest in the use of nanoparticles due to their astonishing range of applications. Size effects and multifunctionality are the main characteristics of nanoparticles.Super paramagnetic iron oxide nanoparticles, quantum dots, silver and gold nanoparticles are the most widely studied nanoparticles. Among these, gold nanoparticles have attracted intense interest, because of theirunique physical and chemical properties, optical properties, ease of synthesis,surface modification, less toxicity,biocompatibility, and ease of detection. This review presents the overview of the applications of gold nanoparticles in biomedical research. Keywords: gold nanoparticles, Biomedical applications, Nano carrier INTRODUCTION Nanotechnology can be defined as the design, characterization, production and application of structures, devices and systems by controlling shape and size at a nanometer scale [1]. Nanotechnology has provided research-level breakthrough in various industrial applications. Among those it has attained remarkable levels in medicine (bio diagnostics, drug delivery and cancer therapy)[2-4]. These achievements came from the usage of versatile nanomaterials.Nanomaterials are materials with the sizes in the range of 1 to several 100’s of nanometers, attracts an ample attention in different fields of physics, chemistry, material science, medicine and biology, due to their unique electronic, magnetic, optical, mechanical, physical and chemical properties. Super paramagnetic iron oxide nanoparticles, quantum dots, silver and gold nanoparticles are the most widely studied nanoparticles. They can be produced from different materials in different sizes and shapes such as spheres, rods, wires and tubes. A wide range of techniques have been used to synthesize nanoparticles in different solid mediums such as glass [5], metallic [6] and polymeric films [7] to realize new applications. They can be produced from different materials in different sizes and shapes such as spheres, rods, wires, and tubes. The characteristic properties of nanoparticles are their (a) small size (1–100 nm), (b) large surface-to-volume ratio, (c) physical and chemical properties that can be tuned depending upon the requirements of size, composition, and shape, (d) quantitative and qualitative target-binding properties and (e) high robustness shown by some of the nanostructure materials[3].In recent years, the use of metal nanoparticles has expanded in biomedical research. They are used in diagnosis and therapeutics due to their unique properties of high reactivity to the living cells, stability over high temperatures and translocation into the cells, etc. They also exhibit exceptional optical properties making them capable of producing quantum effects suitable for imaging applications. Most commonly studied metal nanoparticles include gold, silver, titanium oxide and iron nanoparticles[8]. Mainly nanoparticles are used as nanocarriers for drug delivery applications and in the treatment of cancer. Nanocarriers have provided a novel platform for target-specific delivery of therapeutic agents[2]. Several delivery systems have been designed based on different nanomaterials, such as polymers[9], dendrimers[10], liposomes[11], nanotubes[12] and nanorods[13]. Various types of nanoparticles (e.g.inorganic nanoparticles, liposomes) have attracted attention as drug carriers for the delivery of drugs into tumors[14, 15]. Traditional tumor- targeting strategies are classified into ‘passive targeting’ and ‘active targeting’. Passive targeting is based on the enhanced permeation and retention (EPR). Nanoparticles exhibits EPR, which makes them accumulate in tumor tissues to higher extents than in normal tissue due to the leaky tumor blood vasculature [2, 16]. Moreover, the high surface area of nanoparticles is advantageous to load drugs and thus enhance drug's solubility, stability, and pharmacokinetic parameters [17]. Active targeting involves conjugating molecules that have affinity for the cell surface[18, 19]. Gold nanoparticles are compatible for a wide range of biological applications because of their unique physical and chemical properties. Recently, the applications of gold nanoparticles have expanded into various biomedical fields (biosensors, immunoassays, genomics, photo thermolysis of cancer cells, microorganisms detection and control, targeted drug delivery, optical imaging, monitoring of biological cells and tissues by exploiting resonance scattering,or in vivo photo acoustic techniques[20-29]). Gold nanoparticles find significant exploitations in biomedical field due to their (i) comparative chemical stability,(ii) simple and ease of synthesis and fabrication process,(iii) genuine biocompatibility and noninterference with other labeled biomaterials (e.g. antibody and other biomarkers)[30, 31],(iv) convenient surface bioconjugation with molecular probes,(v) remarkable optical properties related with the localized Plasmon resonance and (vi) low toxicity [32]. Release of drug would involve two processes, such as internalstimuli operated system, which could occur in a biologicallycontrolled manner, or external stimuli, operatedby the support of stimuli- generated processes [17, 33].Size and monodispersity are key aspects for drug delivery systems. Gold nanoparticles can be readily fabricated with sizes matching with that of biomolecules such as proteins and DNA, facilitating their integration into biological systems. The high surface area-to-volume ratio of nanoparticles provides dense loading of functionalities incorporating targeting and therapeutic materials[34]. The highly tunable and multivalent surface structures of goldnanoparticles offer the diversity to incorporate multiple therapeutic drugs or biomacromolecules by covalent or non- covalent conjugation on the surface of a nanoparticle[17, 35]. One important aspect of gold nanoparticle is their ease of functionalization. This ability to tailor the surface made gold nanoparticles effective in both active and passive targeting[36].To sum up, engineering the nanoparticles in different directions and ability to tailor the physico- chemical properties have together given a right way to make the materials more advanced and highly robust for the binding affinities of various biomolecules and drug targets[30] as well as for the diagnosis and treatment of diseases. International Journal of Pharmacy and Pharmaceutical Sciences ISSN- 0975-1491 Vol 6 suppl 2, 2014 Academic Sciences