Gold nanoparticles: From nanomedicine to nanosensing

Gold nanoparticle-siRNA mediated oncogene knockdown at RNA and protein level, with associated gene effects

Aims: RNAi is a powerful tool for gene silencing that can be used to reduce undesirable overexpression of oncogenes as a novel form of cancer treatment. However, when using RNAi as a therapeutic tool there is potential for associated gene effects. This study aimed to utilize gold nanoparticles to deliver siRNA into HeLa cells. Results: Knockdown of the c-myc oncogene by RNAi, at the RNA, protein and cell proliferation level was achieved, while also identifying associated gene responses. Discussion: The gold nanoparticles used in this study present an excellent delivery platform for siRNA, but do note associated gene changes. Conclusion: The study highlights the need to more widely assess the cell physiological response to RNAi treatment, rather than focus on the immediate RNA levels.

Inorganic nanovectors for nucleic acid delivery

Nucleic acids show immense potential to treat cancer, acquired immune deficiency syndrome, neurological diseases and other incurable human diseases. Upon systemic administration, they encounter a series of barriers and hence barely reach the site of action, the cell. Intracellular delivery of nucleic acids is facilitated by nanovectors, both viral and non-viral. A major advantage of non-viral vectors over viral vectors is safety. Nanovectors evaluated specifically for nucleic acid delivery include polyplexes, lipoplexes and other cationic carrier-based vectors. However, more recently there is an increased interest in inorganic nanovectors for nucleic acid delivery. Nevertheless, there is no comprehensive review on the subject. The present review would cover in detail specific properties and types of inorganic nanovectors, their preparation techniques and various biomedical applications as therapeutics, diagnostics and theranostics. Future prospects are also suggested.

Silica-gold nanoparticles for atheroprotective management of plaques: results of the NANOM-FIM trial

BACKGROUND

Atheroregression becomes an attractive target for cardiovascular treatment. Some clinical trials have demonstrated that intensive therapy with rosuvastatin or recombinant ApoA-I Milano can partially reduce the total atheroma volume (TAV) up to 6.38 mm(3) or 14.1 mm(3) respectively. Our previous bench studies of selected nanotechnologies documented TAV reduction up to an unprecedented 79.4 mm(3).

METHODS

The completed observational three arms (n = 180) first-in-man trial (the NANOM FIM trial) assessed (NCT01270139) the safety and feasibility of two delivery techniques for nanoparticles (NP), and plasmonic photothermal therapy (PPTT). Patients were assigned to receive either (1) nano-intervention with delivery of silica-gold NP in a bioengineered on-artery patch (n = 60), or (2) nano-intervention with delivery of silica-gold iron-bearing NP with targeted micro-bubbles and stem cells using a magnetic navigation system (n = 60) versus (3) stent implantation (n = 60). The primary outcome was TAV at 12 months.

RESULTS

The mean TAV reduction at 12 months in the Nano group was 60.3 mm(3) (SD 39.5; min 41.9 mm(3), max 94.2 mm(3); p < 0.05) up to mean 37.8% (95% CI: 31.1%, 51.7%; p < 0.05) plaque burden. The analysis of the event free survival of the ongoing clinical follow-up shows the significantly lower risk of cardiovascular death in the Nano group when compared with others (91.7% vs. 81.7% and 80% respectively; p < 0.05) with no cases of the target lesion-related complications.

CONCLUSIONS

PPTT using silica-gold NP associated with significant regression of coronary atherosclerosis.

Anti protein A antibody-gold nanorods conjugate: a targeting agent for selective killing of methicillin resistant Staphylococcus aureus using photothermal therapy method

The high prevalence of methicillin resistant Staphylococcus aureus (MRSA) and developing resistance to antibiotics requires new approaches for treatment of infectious diseases due to this bacterium. In this study, we developed a targeting agent for selective killing of MRSA using photothermal therapy method based on anti protein A antibody and gold nanorods (GNRs). Polystyrene sulfonate (PSS) coated GNRs were conjugated with anti protein A antibody. The FT-IR and UV-vis analyses approved the formation of anti protein A antibody-gold nanorods conjugate. In vitro study of photothermal therapy showed 82% reduction in the MRSA cells viability which was significantly greater than the ablation effect of free GNRs and laser alone. Significant accumulation of anti protein A antibody-GNRs in the infected muscle in comparison with normal muscle approved the targeting ability of new agent. In vivo study of photothermal therapy resulted in a significant reduction (73%) in the bacterial cells viability in the infected mouse model. These results demonstrated the ability of anti protein A antibody-GNRs conjugate in combination with NIR laser energy for selective killing of MRSA in mouse model.

Synthesis of proton caged disulphide compounds for gold nanoparticle functionalization

Novel proton caged compounds have been synthesized, with a sulphur bridge to bind gold nanoparticles and release protons upon UV irradiation.

The impact of the polar core size and external organic media composition on micelle–micelle interactions: the effect on gold nanoparticle synthesis

An easy way to modulate reverse micelles as nanoreactors to produce different kinds of gold nanoparticles.

Magnetic nanoparticles-serum proteins bioconjugates for binding of irinotecan

The binding of irinotecan to serum proteins (hemoglobin, globulin and human serum albumin) was studied on the surface of epoxide modified superparamagnetic iron oxide nanoparticles (GPTS-SPIONs), which were synthesized by the coprecipitation of ferrous and ferric salts with NH4OH and then modified with [3-(2,3-epoxypropoxy)propyl] trimethoxy silane (GPTS) to obtain functional epoxide groups on the SPIONs' surface. Results were compared to find an alternative as drug carries system. Data showed that binding amount of human serum albumin (HSA), globulin (Glb) and hemoglobin (Hb) found to be as 44, 21.2 and 32.6 μg per 20 mg of GPTS modified SPIONs, respectively. The thermal behavior of the serum protein-Ir interaction on GPTS-SPIONs was also studied by using thermo gravimetric analysis (TGA) technique and then the kinetic parameters for the thermal decomposition were determined using Horowitz-Metzger method.

Role of Fe-responsive genes in bioreduction and transport of ionic gold to roots of Arabidopsis thaliana during synthesis of gold nanoparticles

Several studies have shown potassium chloroaurate (KAuCl4)-mediated synthesis of gold nanoparticles (AuNPs) by using extracts of different parts of diverse plant species. However, the mechanism underlying the formation of AuNPs in planta has far from being elucidated. Here, we report the molecular evidence towards the role of genes involved in iron (Fe) homeostasis during in planta synthesis of AuNPs in roots of Arabidopsis thaliana. Firstly, we examined the dosage-dependent effects of KAuCl4 treatment on primary root length (PRL), and meristematic activity of roots in transgenic CycB1;1::uidA. Compared to control seedling (0 ppm KAuCl4), PRL and meristematic activity of primary and lateral roots showed progressive attenuation in seedlings treated with higher concentrations of KAuCl4 (25 ppm or above). Therefore, subsequent studies on in planta synthesis of AuNPs, and molecular responses were carried out in roots of the seedlings treated with 10 ppm KAuCl4 for 7 d. TEM of KAuCl4-treated seedlings showed the presence of monodisperse AuNPs of different shapes and sizes in root biomatrix. There was a significant induction of FRO2 in KAuCl4-treated roots, and therefore its likely involvement in bioreduction of Au(3)(+) could be assumed. Elevated expression levels of Fe transporters IRT1 and IRT2 further suggested their potential role in transport of bioreduced Au(3+) across root membrane. Expression levels of other genes involved in Fe homeostasis, and also different members of zinc (Zn), phosphate (Pi), and potassium (K) transporter families remained unaffected by KAuCl4 treatment. An increased Au content in Fe-deprived roots further provided evidence towards the specific role of a subset of Fe-responsive genes during in planta synthesis of AuNPs.

Plasmon resonance based analysis of a single protein conjugated Au nanoshell

The authors perform a numerical calculation of a gold nanoshell, having either a silica core or a hollow one, interacting with incident electromagnetic radiation and aggregated with a single protein on its surface, by using the discrete dipole approximation. The protein model accounts for a tertiary structure that may contain internal cavities, while the entire structure is placed either in vacuum or a uniform host medium. The authors further analyze the near field pattern by a spherical harmonic transform. Our results identify the interactions that account for the observed extinction peak and wavelength shift in related optical experiments. The theoretical basis provided in this work may be used not only to identify a single protein conjugated nanoparticle, but also to determine the cavity content of the protein by its refractive index properties, determined from optical measurements.

Phytolatex synthesized gold nanoparticles as novel agent to enhance sun protection factor of commercial sunscreens

OBJECTIVE

To study the potential of phytolatex (latex of Jatropha gossypifolia) fabricated gold nanoparticles as promising candidate in sunscreen formulations for enhancement in sun protection factor.

METHODS

In this study, plant latex was used as reducing and capping agent to synthesize gold nanoparticles. Latex fabricated gold nanoparticles were characterized by different analytical techniques such as UV-Vis spectroscopy, Fourier transforms infrared spectroscopy, dynamic light scattering, zeta potential, transmission electron microscopy and X-ray diffraction. Potential of sunscreen preparations containing gold nanoparticles to protect skin from UV radiation was investigated by in vitro sun protection factor analysis. Transmission electron microscopy and UV-Vis spectroscopy techniques were used to get insight into mechanism by which AuNPs enhance sun protection factor of sunscreen.

RESULTS

Monodisperse gold nanoparticles were synthesized using plant latex without need of hazardous chemical reducing and capping agents. Gold nanoparticles showed surface plasmon resonance peak at 550 nm in UV-Vis spectroscopic study. Gold nanoparticles were spherical and triangular in shape with size range of 30-50 nm. The zeta potential of gold nanoparticles was found to be -9.39 ± 0.19 mV. XRD analysis confirmed face-centred cubic (fcc) structure of gold nanoparticles. Incorporation of latex synthesized gold nanoparticles (2 and 4 [% w/w]) into commercial sunscreens increased the sun protection factor from 2.43 ± 0.74 to 24.11 ± 0.46% than sunscreen devoid of gold nanoparticles. From UV-Vis absorption spectroscopy and TEM analysis, it was observed that gold nanoparticles enhance the sun protection factor of commercial sunscreens due to reflection and scattering of UV radiation.

CONCLUSION

Phytolatex synthesized gold nanoparticle is novel agent to enhance sun protection factor of commercial sunscreens. Gold nanoparticles aggregation in commercial sunscreen was the main factor behind SPF enhancement. This study showed that gold nanoparticles are potent alternative to traditionally used hazardous titanium dioxide and zinc oxide nanoparticles in sunscreen.

Quantification of functionalised gold nanoparticle-targeted knockdown of gene expression in HeLa cells

INTRODUCTION

Gene therapy continues to grow as an important area of research, primarily because of its potential in the treatment of disease. One significant area where there is a need for better understanding is in improving the efficiency of oligonucleotide delivery to the cell and indeed, following delivery, the characterization of the effects on the cell.

METHODS

In this report, we compare different transfection reagents as delivery vehicles for gold nanoparticles functionalized with DNA oligonucleotides, and quantify their relative transfection efficiencies. The inhibitory properties of small interfering RNA (siRNA), single-stranded RNA (ssRNA) and single-stranded DNA (ssDNA) sequences targeted to human metallothionein hMT-IIa are also quantified in HeLa cells. Techniques used in this study include fluorescence and confocal microscopy, qPCR and Western analysis.

FINDINGS

We show that the use of transfection reagents does significantly increase nanoparticle transfection efficiencies. Furthermore, siRNA, ssRNA and ssDNA sequences all have comparable inhibitory properties to ssDNA sequences immobilized onto gold nanoparticles. We also show that functionalized gold nanoparticles can co-localize with autophagosomes and illustrate other factors that can affect data collection and interpretation when performing studies with functionalized nanoparticles.

CONCLUSIONS

The desired outcome for biological knockdown studies is the efficient reduction of a specific target; which we demonstrate by using ssDNA inhibitory sequences targeted to human metallothionein IIa gene transcripts that result in the knockdown of both the mRNA transcript and the target protein.

PS microspheres coated by AuNPs via thermodynamic driving heterocoagulation and their high catalytic activity

A unique method of fabricating PS/AuNPs composite particles in ex situ mode is proposed on the basis of thermodynamically driving mechanism. It is facile and versatile as it eliminates the need for surface functionalizations and modifications of both PS microspheres and AuNPs. The PS/AuNPs composite particles take on a raspberry-like morphology with controllable coverage according to some thermodynamic factors, which have been extensively characterized by scanning electron microscopy, transmission electron microscopy, and thermogravimetric analysis. More importantly, the PS/AuNPs composite particles hold higher catalytic efficiency and better repeatability than the previously reported results, which are confirmed in two oxidation-reduction reactions of 2-nitroaniline/NaBH(4) and rhodamine B/NaBH(4).

Anthelmintic efficacy of gold nanoparticles derived from a phytopathogenic fungus, Nigrospora oryzae

Exploring a green chemistry approach, this study brings to the fore, the anthelmintic efficacy of gold nanoparticles, highlighting the plausible usage of myconanotechnology. Gold nanoparticles of ∼6 to ∼18 nm diameter were synthesized by treating the mycelia-free culture filtrate of the phytopathogenic fungus with gold chloride. Their size and morphology were confirmed by UV-Vis spectroscopy, DLS data, AFM and TEM images. The XRD studies reveal a crystalline nature of the nanoparticles, which are in cubic phase. The FTIR spectroscopic studies before and after the formation of nanoparticles show the presence of possible functional groups responsible for the bio-reduction and capping of the synthesized gold nanoparticles. The latter were tested as vermifugal agents against a model cestode Raillietina sp., an intestinal parasite of domestic fowl. Further, ultrastructural and biochemical parameters were used to corroborate the efficacy study.

Modulation of structural, energetic and electronic properties of DNA and size-expanded DNA bases upon binding to gold clusters

A strong modulation in electronic properties, indicating that such complexes have the potential to serve as scaffolds for building nano electronic devices.

The anti-inflammatory properties of Au–scopoletin nanoconjugates

Au particles capped with scopoletin, isolated from Artemisia roxburghiana using column chromatography, show no change in NO inhibitory activity and inhibition of the oxidative burst of reactive oxygen species (ROS) in whole blood phagocytes and isolated neutrophils is enhanced by three times when compared to pure scopoletin.

Genome wide transcriptome analysis reveals ABA mediated response in Arabidopsis during gold (AuCl(-) 4) treatment

The unique physico-chemical properties of gold nanoparticles (AuNPs) find manifold applications in diagnostics, medicine and catalysis. Chemical synthesis produces reactive AuNPs and generates hazardous by-products. Alternatively, plants can be utilized to produce AuNPs in an eco-friendly manner. To better control the biosynthesis of AuNPs, we need to first understand the detailed molecular response induced by AuCl(-) 4 In this study, we carried out global transcriptome analysis in root tissue of Arabidopsis grown for 12- h in presence of gold solution (HAuCl4) using the novel unbiased Affymetrix exon array. Transcriptomics analysis revealed differential regulation of a total of 704 genes and 4900 exons. Of these, 492 and 212 genes were up- and downregulated, respectively. The validation of the expressed key genes, such as glutathione-S-transferases, auxin responsive genes, cytochrome P450 82C2, methyl transferases, transducin (G protein beta subunit), ERF transcription factor, ABC, and MATE transporters, was carried out through quantitative RT-PCR. These key genes demonstrated specific induction under AuCl4(-) treatment relative to other heavy metals, suggesting a unique plant-gold interaction. GO enrichment analysis reveals the upregulation of processes like oxidative stress, glutathione binding, metal binding, transport, and plant hormonal responses. Changes predicted in biochemical pathways indicated major modulation in glutathione mediated detoxification, flavones and derivatives, and plant hormone biosynthesis. Motif search analysis identified a highly significant enriched motif, ACGT, which is an abscisic acid responsive core element (ABRE), suggesting the possibility of ABA- mediated signaling. Identification of abscisic acid response element (ABRE) points to the operation of a predominant signaling mechanism in response to AuCl(-) 4 exposure. Overall, this study presents a useful picture of plant-gold interaction with an identification of candidate genes involved in nanogold synthesis.

Computer simulation and detailed mean-field approximation applied to adsorption on nanoparticles

Adsorption thermodynamics of interacting particles adsorbed on icosahedral and truncated octahedral nanoparticles was studied by a detailed mean-field approximation and Monte Carlo simulations. The nanoparticle is tackled as a multivariate surface, where different types of adsorption sites occur according to coordination with nearest neighbors. In addition, lateral couplings between the adsorbed particles are considered. The analysis covers a wide range of interactions, extending from physical to strong chemical bonds, and different sizes and shapes of nanoparticles.

Design and simulation of perturbed onion-like quantum-dot-quantum-well (CdSe/ZnS/CdSe/ZnS) and its influence on fluorescence resonance energy transfer mechanism

In this study, the authors investigate one of the biological sensory applications (fluorescence resonance energy transfer (FRET)) that has astonishing influence on implementation of the bio-medical assays. For the first time, in this study, the new inorganic modified nanoparticle structure (quantum-dot quantum-well (QDQW) heteronanocrystal) is used as donor particle. By considering the mentioned structure, the authors can easily manipulate the donor emission spectrum and all parameters of FRET, such as overlapping between the donor emission and acceptor absorption. In this procedure, the Förster radius can be completely controlled. Moreover, the quantum confinement effects, including the strong-confinement and the weak-confinement regime, are investigated for FRET essential variables. As a main goal of this study, the authors will mathematically explore the influences of perturbation on the intrinsic parameters of nanoparticles (lifetime and bandwidth of emission spectrum) and on the sensitivity of FRET. It can be revealed that the presence of perturbation in nanoparticle has a devastating influence on biological assay characteristics, which will be probe in presented simulations. Furthermore, the physically analysing of QDQW heteronanocrystal structure is performed by the accurate eight-band K.P theory and finite-element method.

Synthesis and characterization of surface-enhanced Raman-scattered gold nanoparticles

In this paper, we report a simple, rapid, and robust method to synthesize surface-enhanced Raman-scattered gold nanoparticles (GNPs) based on green chemistry. Vitis vinifera L. extract was used to synthesize noncytotoxic Raman-active GNPs. These GNPs were characterized by ultraviolet-visible spectroscopy, dynamic light-scattering, Fourier-transform infrared (FTIR), transmission electron microscopy (TEM), X-ray diffraction (XRD), and Raman spectroscopy. The characteristic surface plasmon-resonance band at ~ 528 nm is indicative of spherical particles, and this was confirmed by TEM. The N-H and C-O stretches in FTIR spectroscopy indicated the presence of protein molecules. The predominant XRD plane at (111) and (200) indicated the crystalline nature and purity of GNPs. GNPs were stable in the buffers used for biological studies, and exhibited no cytotoxicity in noncancerous MIO-M1 (Müller glial) and MDA-MB-453 (breast cancer) cell lines. The GNPs exhibited Raman spectral peaks at 570, 788, and 1,102 cm(-1). These new GNPs have potential applications in cancer diagnosis, therapy, and ultrasensitive biomarker detection.

Size-dependent cellular toxicity and uptake of commercial colloidal gold nanoparticles in DU-145 cells

Urinary tract infection (UTI) is a predominant condition in prostate cancer patients. Escherichia coli ORN178 (EC-178) is the uropathogen that causes recurrent infection by binding specifically to adhesins of prostate cancer cells (DU-145 cells). Gold nanoparticles (GNPs) have been used in biodiagnosis of pathogens. In this study, we have investigated the binding time of EC-178 to DU-145 cells, the cytotoxicity and uptake of plain and mannose functionalized and 20 and 200 nm GNPs (d-mannan (Mn)-GNPs). We also investigated the protein corona of GNPs when incubated with fetal bovine serum to study the protein corona which decides the biological fate of the GNPs. It was seen that EC-178 binds and is inside the DU-145 cells by 3 h of incubation period. Plain 20 nm GNPs decrease the percentage of viable cells in 48 and 72 h in log and lag phase of DU-145 cells. It was also observed that the Mn-GNPs were taken up by the DU-145 cells significantly more than the plain GNPs. Protein corona was observed when GNPs were incubated with fetal bovine serum which was confirmed by dynamic light scattering measurements and SDS-PAGE gel.

Hair fiber as a nanoreactor in controlled synthesis of fluorescent gold nanoparticles

The synthesis and detailed characterization of gold nanoparticles (AuNPs) inside human hair has been achieved by treatment of hair with HAuCl(4) in alkaline medium. The AuNPs, which show a strong red fluorescence under blue light, are generated inside the fiber and are arranged in the cortex in a remarkably regular pattern of whorls based on concentric circles, like a fingerprint. It opens an area of genuine nanocomposites with novel properties due to AuNPs inside the hair shaft.

Multifunctional nanoscale strategies for enhancing and monitoring blood vessel regeneration

Nanomedicine has great potential in biomedical applications, and specifically in regenerative medicine and vascular tissue engineering. Designing nanometer-sized therapeutic and diagnostic devices for tissue engineering applications is critical because cells experience and respond to stimuli on this spatial scale. For example, nanoscaffolds, including nanoscalestructured or nanoscale surface-modified vascular scaffolds, can influence cell alignment, adhesion, and differentiation to promote better endothelization. Furthermore, nanoscale contrast agents can be extended to the field of biomedical imaging to monitor and track stem cells to better understand the process of neovascularization. In addition, nanoscale systems capable of delivering biomolecules (e.g. peptides and angiogenic genes/proteins) can influence cell behavior, function, and phenotype to promote blood vessel regeneration. This review will focus on nanomedicine and nanoscale strategies applied to vascular tissue engineering. In particular, some of the latest research and potential applications pertaining to nanoscaffolds, biomedical imaging and cell tracking using nanoscale contrast agents, and nanodelivery systems of bioactive molecules applied to blood vessel regeneration will be discussed. In addition, the overlap between these three areas and their synergistic effects will be examined as related to vascular tissue engineering.

Gold nanoparticles reduced in situ and dispersed in polymer thin films: optical and thermal properties

Optical and thermal activity of plasmon-active nanoparticles in transparent dielectric media is of growing interest in thermal therapies, photovoltaics and optoelectronic components in which localized surface plasmon resonance (LSPR) could play a significant role. This work compares a new method to embed gold nanoparticles (AuNPs) in dense, composite films with an extension of a previously introduced method. Microscopic and spectroscopic properties of the two films are related to thermal behavior induced via laser excitation of LSPR at 532 nm in the optically transparent dielectric. Gold nanoparticles were incorporated into effectively nonporous 680 μm thick polydimethylsiloxane (PDMS) films by (1) direct addition of organic-coated 16 nm nanoparticles; and (2) reduction of hydrogen tetrachloroaurate (TCA) into AuNPs. Power loss at LSPR excitation frequency and steady-state temperature maxima at 100 mW continuous laser irradiation showed corresponding increases with respect to the mass of gold introduced into the PDMS films by either method. Measured rates of temperature increase were higher for organic-coated NP, but higher gold content was achieved by reducing TCA, which resulted in larger overall temperature changes in reduced AuNP films.

Targeted delivery of nanomedicines

The role of targeting of the diseased region by a drug is emphasized. The rationale for resorting to nanomaterials as drug carriers is explained. A clear understanding of the biological environment, its degradation in diseased condition, and the interaction of the drug with it in normal condition and during illness lie at the core of successful drug delivery. Passive and active drug targeting approaches are differentiated. Commonly used drug targets, targeting ligands, and nanoscale systems are elaborated. Mechanisms of internalization of nanomedicines and circumventing P-glycoprotein mediated resistance are outlined. The paper presents an overview of the current scenario of targeted transportation of nanomedicines to the affected organ and suggests future research directions.

Gold nanoparticles capped by a GC-containing peptide functionalized with an RGD motif for integrin targeting

Gold nanoparticles were obtained by reduction of a tetrachloroaurate aqueous solution in the presence of a RGD-(GC)(2) peptide as stabilizer. As comparison, the behavior of the (GC)(2) peptide has been studied. The (GC)(2) and RGD-(GC)(2) peptides were prepared ad hoc by Fmoc synthesis. The colloidal systems have been characterized by UV-visible, TGA, ATR-FTIR, mono and bidimensional NMR techniques, confocal and transmission (TEM) microscopy, ζ-potential, and light scattering measurements. The efficient cellular uptake of Au-RGD-(GC)(2) and Au-(GC)(2) stabilized gold nanoparticles into U87 cells (human glioblastoma cells) were investigated by confocal microscopy and compared with the behavior of (GC)(2) capped gold nanoparticles. A quantitative determination of the nanoparticles taken up has been carried out by measuring the pixel brightness of the images, a measure that highlighted the importance of the RGD termination of the peptide. Insight in the cellular uptake mechanism was investigated by TEM microscopy. Various important evidences indicated the selective uptake of RGD-(GC)(2) gold nanoparticles into the nucleus.

Quantitative comparison of optimized nanorods, nanoshells and hollow nanospheres for photothermal therapy

The purpose of this study is to get more efficient gold nanoparticles, for necrosis of cancer cells, in photothermal therapy. Therefore a numerical maximization of the absorption efficiency of a set of nanoparticles (nanorod, nanoshell and hollow nanosphere) is proposed, assuming that all the absorbed light is converted to heat. Two therapeutic cases (shallow and deep cancer) are considered. The numerical tools used in this study are the full Mie theory, the discrete dipole approximation and the particle swarm optimization. The optimization leads to an improved efficiency of the nanoparticles compared with previous studies. For the shallow cancer therapy, the hollow nanosphere seems to be more efficient than the other nanoparticles, whereas the hollow nanosphere and nanorod, offer comparable absorption efficiencies, for deep cancer therapy. Finally, a study of tolerance for the size parameters to guarantee an absorption efficiency threshold is included.

Nanomaterials: a challenge for toxicological risk assessment?

Nanotechnology has emerged as one of the central technologies in the twenty-first century. This judgment becomes apparent by considering the increasing numbers of people employed in this area; the numbers of patents, of scientific publications, of products on the market; and the amounts of money invested in R&D. Prospects originating from different fields of nanoapplication seem unlimited. However, nanotechnology certainly will not be able to meet all of the ambitious expectations communicated, yet has high potential to heavily affect our daily life in the years to come. This might occur in particular in the field of consumer products, for example, by introducing nanomaterials in cosmetics, textiles, or food contact materials. Another promising area is the application of nanotechnology in medicine fueling hopes to significantly improve diagnosis and treatment of all kinds of diseases. In addition, novel technologies applying nanomaterials are expected to be instrumental in waste remediation and in the production of efficient energy storage devices and thus may help to overcome world's energy problems or to revolutionize computer and data storage technologies. In this chapter, we will focus on nanomaterials. After a brief historic and general overview, current proposals of how to define nanomaterials will be summarized. Due to general limitations, there is still no single, internationally accepted definition of the term "nanomaterial." After elaborating on the status quo and the scope of nanoanalytics and its shortcomings, the current thinking about possible hazards resulting from nanoparticulate exposures, there will be an emphasis on the requirements to be fulfilled for appropriate health risk assessment and regulation of nanomaterials. With regard to reliable risk assessments, until now there is still the remaining issue to be resolved of whether or not specific challenges and unique features exist on the nanoscale that have to be tackled and distinctively addressed, given that they substantially differ from those encountered with microsized materials or regular chemicals. Based on the current knowledge, we finally provide a proposal on how risk assessment in the nanofield could be achieved and how it might look like in the near future.

A gold nanoparticle-based immunochromatographic assay: the influence of nanoparticulate size

Four different sized gold nanoparticles (14 nm, 16 nm, 35 nm and 38 nm) were prepared to conjugate an antibody for a gold nanoparticle-based immunochromatographic assay which has many applications in both basic research and clinical diagnosis. This study focuses on the conjugation efficiency of the antibody with different sized gold nanoparticles. The effect of factors such as pH value and concentration of antibody has been quantificationally discussed using spectra methods after adding 1 wt% NaCl which induced gold nanoparticle aggregation. It was found that different sized gold nanoparticles had different conjugation efficiencies under different pH values and concentrations of antibody. Among the four sized gold nanoparticles, the 16 nm gold nanoparticles have the minimum requirement for antibody concentrations to avoid aggregation comparing to other sized gold nanoparticles but are less sensitive for detecting the real sample compared to the 38 nm gold nanoparticles. Consequently, different sized gold nanoparticles should be labeled with antibody under optimal pH value and optimal concentrations of antibody. It will be helpful for the application of antibody-labeled gold nanoparticles in the fields of clinic diagnosis, environmental analysis and so on in future.

Gold nanoparticles in biomedical applications: recent advances and perspectives

Gold nanoparticles (GNPs) with controlled geometrical, optical, and surface chemical properties are the subject of intensive studies and applications in biology and medicine. To date, the ever increasing diversity of published examples has included genomics and biosensorics, immunoassays and clinical chemistry, photothermolysis of cancer cells and tumors, targeted delivery of drugs and antigens, and optical bioimaging of cells and tissues with state-of-the-art nanophotonic detection systems. This critical review is focused on the application of GNP conjugates to biomedical diagnostics and analytics, photothermal and photodynamic therapies, and delivery of target molecules. Distinct from other published reviews, we present a summary of the immunological properties of GNPs. For each of the above topics, the basic principles, recent advances, and current challenges are discussed (508 references).

Ultrafast nonlinear optical response of photoconductive ZnO films with fluorine nanoparticles

The absorptive and refractive third order nonlinear optical properties exhibited by a ZnO thin solid film with fluorine nanoparticles were studied with picosecond and femtosecond pulses using different techniques. We were able to evaluate the photoconductivity of the material and the quenching of the induced birefringence observed in the presence of two-photon absorption. The samples were prepared by a chemical spray deposition technique. In order to investigate the different contributions of the third order nonlinearities of the film, we analyzed the vectorial self-diffraction effect and the optical Kerr transmittance observed in the sample. A dominantly absorptive nonlinearity was measured at a 532 nm wavelength with 50 ps pulses, while nonlinear refraction was found to be negligible in this regime. On the other side, a pure electronic refractive third order nonlinearity without the contribution of nonlinear absorption was detected at 830 nm with 80 fs pulse duration. A quasi-instantaneous optical response and a strong enhancement in the ultrafast nonlinear refraction with the inhibition of the picosecond two-photon absorption mechanism were measured for the case of the femtosecond excitation.