Gold nanoparticles have been used in biomedical applications since their first colloidal syntheses more than three centuries ago. However, over the past two decades, their beautiful colors and unique electronic properties have also attracted tremendous attention due to their historical applications in art and ancient medicine and current applications in enhanced optoelectronics and photovoltaics. In spite of their modest alchemical beginnings, gold nanoparticles exhibit physical properties that are truly different from both small molecules and bulk materials, as well as from other nanoscale particles. Their unique combination of properties is just beginning to be fully realized in range of medical diagnostic and therapeutic applications. This critical review will provide insights into the design, synthesis, functionalization, and applications of these artificial molecules in biomedicine and discuss their tailored interactions with biological systems to achieve improved patient health. Further, we provide a survey of the rapidly expanding body of literature on this topic and argue that gold nanotechnology-enabled biomedicine is not simply an act of ‘gilding the (nanomedicinal) lily’, but that a new ‘Golden Age’ of biomedical nanotechnology is truly upon us. Moving forward, the most challenging nanoscience ahead of us will be to find new chemical and physical methods of functionalizing gold nanoparticles with compounds that can promote efficient binding, clearance, and biocompatibility and to assess their safety to other biological systems and their long-term term effects on human health and reproduction (472 references).

The golden age: gold nanoparticles for biomedicine

Inorganic colloidal nanoparticles are very small, nanoscale objects with inorganic cores that are dispersed in a solvent. Depending on the material they consist of, nanoparticles can possess a number of different properties such as high electron density and strong optical absorption (e.g. metal particles, in particular Au), photoluminescence in the form of fluorescence (semiconductor quantum dots, e.g. CdSe or CdTe) or phosphorescence (doped oxide materials, e.g. Y(2)O(3)), or magnetic moment (e.g. iron oxide or cobalt nanoparticles). Prerequisite for every possible application is the proper surface functionalization of such nanoparticles, which determines their interaction with the environment. These interactions ultimately affect the colloidal stability of the particles, and may yield to a controlled assembly or to the delivery of nanoparticles to a target, e.g. by appropriate functional molecules on the particle surface. This work aims to review different strategies of surface modification and functionalization of inorganic colloidal nanoparticles with a special focus on the material systems gold and semiconductor nanoparticles, such as CdSe/ZnS. However, the discussed strategies are often of general nature and apply in the same way to nanoparticles of other materials.

https://faculty.washington.edu/mzhang/mse599/Surface-modification.full.pdf

Surface modification, functionalization and bioconjugation of colloidal inorganic nanoparticles

Gold nanorods have received much attention due to their unique optical and electronic properties which are dependent on their shape, size, and aspect ratio. This article covers in detail the synthesis, functionalization, self-assembly, and sensing applications of gold nanorods. The synthesis of three major types of rods is discussed: single-crystalline and pentahedrally-twinned rods, which are synthesized by wet chemistry methods, and polycrystalline rods, which are synthesized by templated deposition. Functionalization of these rods is usually necessary for their applications, but can often be problematic due to their surfactant coating. Thus, general strategies are provided for the covalent and noncovalent functionalization of gold nanorods. The review will then examine the significant progress that has been made in controllable assembly of nanorods into various arrangements. This assembly can have a large effect on measurable properties of rods, making it particularly applicable towards sensing of a variety of analytes. Other types of sensing not dependent on nanorod assembly, such as refractive-index based sensing, are also discussed.

Functional Gold Nanorods: Synthesis, Self-Assembly, and Sensing Applications

Light-activated therapies can be used to eradicate diseased cells and tissues in a noninvasive manner. Much attention has been focused on the emerging potential of photothermolysis (also referred to as optical hyperthermia), which involves the conversion of absorbed light into heat via nonradiative mechanisms. Photoactivated effects can be localized and intensified by employing exogenous agents with large absorption cross sections, confining damage to areas of interest with minimal collateral effects.[1] In particular, targeted photothermolysis may be most effective when mediated by photothermal agents that absorb strongly at near infrared (NIR) frequencies, to enable deeper penetration into biological tissues.[2]

/pdf/gold-nanorods-mediate-tumor-cell-death-by-compromising-3wzd3g3qmw.pdf

Gold Nanorods Mediate Tumor Cell Death by Compromising Membrane Integrity

/pdf/hyperthermic-effects-of-gold-nanorods-on-tumor-cells-2vuqwsnxyj.pdf

Hyperthermic effects of gold nanorods on tumor cells

Au surfaces are functionalized by stable dithiocarbamate ligands when exposed to carbon disulfide and secondary amines. The adsorbed dithiocarbamates are robust under a wide pH range and can resist displacement by other chemisorptive surfactants, providing an attractive method for conjugating sensitive molecules onto metal surfaces.

Dithiocarbamate Assembly on Gold

Gold nanoparticles can be encapsulated by various resorcinarene derivatives and assembled into monolayer films at solvent interfaces. Surface charge plays a critical role in both nanoparticle extraction and self-assembly: the degree of monolayer formation and local two-dimensional (2D) order within the nanoparticle arrays is dependent on the chemical nature of the resorcinarene headgroup as well as the presence of other electrolytes. Cluster size distribution analysis can be used to parameterize local 2D order within the arrays in a quantitative manner, based on mean cluster sizes and fractional hexagonal close-packed (hcp) cluster formation. 2D nanoparticle arrays can also be prepared in some cases using Langmuir–Blodgett techniques. These studies demonstrate that resorcinarenes with chemisorptive headgroups promote the self-assembly of well-ordered 2D arrays.

/pdf/self-assembly-of-resorcinarene-stabilized-gold-nanoparticles-3hqv8ldgzs.pdf

Waleska Pérez-Segarra

Papers

Dithiocarbamate Assembly on Gold

Self-assembly of Resorcinarene-stabilized Gold Nanoparticles: Influence of the Macrocyclic Headgroup