Therapeutic possibilities of plasmonically heated gold nanoparticles

Drug delivery interfaces in the 21st century: from science fiction ideas to viable technologies

Early science fiction envisioned the future of drug delivery as targeted micrometer-scale submarines and "cyborg" body parts. Here we describe the progression of the field toward technologies that are now beginning to capture aspects of this early vision. Specifically, we focus on the two most prominent types of systems in drug delivery: the intravascular micro/nano drug carriers for delivery to the site of pathology and drug-loaded implantable devices that facilitate release with the predefined kinetics or in response to a specific cue. We discuss the unmet clinical needs that inspire these designs, the physiological factors that pose difficult challenges for their realization, and viable technologies that promise robust solutions. We also offer a perspective on where drug delivery may be in the next 50 years based on expected advances in material engineering and in the context of future diagnostics.

Selective dehybridization of DNA-Au nanoconjugates using laser irradiation

Plasmonic heating to trigger release of oligonucleotides from nanoconjugates is potentially useful for therapeutic purposes and designed assembly of DNA nanostructures. In the past, great controllability has been achieved by introducing distinctive absorption nanoparticle centers, where the anchoring bond (e.g., sulfur-gold bond) has been selectively broken. Instead of releasing the surface-bound duplex DNA via breakage of the gold-sulphur anchor bond, selective and non-destructive dehybridization of DNA under a "mild" condition on different gold nanoconjugates is demonstrated in this work. This finding will permit sequential dehybridization/release of DNA at specific regions of a complex system; thus it can be extended to control gene expression and to manipulate an assembly of highly organized DNA constructs. Particularly we show herein the feasibility of selectively dehybridizing DNA-Au nanoconjugates via localized plasmonic heating, which is accomplished by controlling the laser wavelength, power, and irradiation time.

Gold nanocrescents for remotely measuring and controlling local temperature

We present a novel technique to remotely measure and control the local temperature within a medium. This technique is based on the observation of the rotational Brownian motion of gold nanocrescent particles, which possess a strong anisotropic light interaction due to their plasmonic properties. Rotational scattering correlation spectroscopy performed on a single nanoparticle is able to determine the local temperature with high accuracy. These nano-thermometers can simultaneously play the role of nano-heaters when absorbing the light of a focused laser beam.

Uptake of gold nanoparticles in several rat organs after intraperitoneal administration in vivo: a fluorescence study

Background. The gold nanoparticles (GNPs) have potential applications in cancer diagnosis and therapy. In an attempt to characterise the potential toxicity or hazards of GNPs as a therapeutic or diagnostic tool, the fluorescence spectra in several rat organs in vivo were measured after intraperitoneal administration of GNPs. Methods. The experimental rats were divided into control and six groups (G1A, G1B, G2A, G2B, G3A, and G3B; G1: 20 nm; G2: 10 nm; G3: 50 nm; A: infusion of GNPs for 3 days; B: infusion of GNPs for 7 days). The fluorescence measurements were investigated in the liver, kidney, heart, and lung organs of rats after intraperitoneal administration of GNPs for periods of 3 and 7 days in vivo. Results. The 10 and 20 nm GNPs exhibited spherical morphology shape, while the 50 nm GNPs exhibited hexagonal shape. A sharp decrease in the fluorescence intensity induced with the larger 50 nm GNPs in the liver, kidney, heart, and lung organs of rats at the exposure duration of 3 and 7 days in vivo compared with the smaller 10 and 20 nm GNPs was observed. Conclusions. The decrease in fluorescence intensity may be attributed to occurrence of strong quenching, decrease in number and surface area of GNPs, and high clearance of GNPs via urine and bile. Moreover, decreasing size may lead to an exponential increase in surface area relative to volume, thus making GNPs surface more reactive on aggregation and to its surrounding biological components. The size, shape, surface area, number, and clearance of GNPs play a key role in toxicity and accumulation in the different rat organs. This study demonstrates that fluorescence peak intensity is particle size and exposure duration dependent. This study suggests that fluorescence intensity can be used as a useful tool for pointing to bioaccumulation and toxicity induced by GNPs in the different rat organs.

Synthesis and in vitro studies of gold nanoparticles loaded with docetaxel

The aim of these studies was to synthesize, characterize and evaluate the efficacy of pegylated gold nanoparticles (AuNPs) that differed in their PEG molecular weight, using PEG 550 and PEG 2000. The synthesis of the gold nanoparticles was carried out by modified Brust method with a diameter of 4-15 nm. The targeting agent folic acid was introduced by the covalent linkage. Finally, the anti-cancer drug docetaxel was encapsulated by the AuNPs by non covalent adsorption. The nanoparticles were characterized by transmission electron microscopy and used for in vitro studies against a hormone-responsive prostate cancer cell line, LnCaP. The loaded nanoparticles reduced the cell viability in more than 50% at concentrations of 6 nM and above after 144 h of treatment. Moreover, observation of prostate cancer cells by optical microscopy showed damage to the cells after exposure to drug-loaded AuNPs while unloaded AuNPs had much less effect.

Plasmon assisted thermal modulation in nanoparticles

Single-particle interactions hold the promise of nanometer-scale devices in areas such as data communications and storage, nanolithography, waveguides, renewable energy and therapeutics. We propose that the collective electronic properties possessed by noble metal nanoparticles may be exploited for device actuation via the unapparent mechanism of plasmon-assisted heat generation and flux. The temperature dependence of the dielectric function and the thermal transport properties of the particles play the central role in the feasibility of the thermally-actuated system, however the behavior of these thermoplasmonic processes is unclear. We experimentally and computationally analyzed modulation via thermoplasmonic processes on a test system of gold (Au) nano-islands. Modulation and energy transport in discontinuous domains exhibited quantitatively different characteristics compared to thin films. The results have implications for all surface plasmon based nano-devices where inevitable small-scale thermal processes are present.

Remotely triggered scaffolds for controlled release of pharmaceuticals

Fe3O4-Au hybrid nanoparticles (HNPs) have shown increasing potential for biomedical applications such as image guided stimuli responsive drug delivery. Incorporation of the unique properties of HNPs into thermally responsive scaffolds holds great potential for future biomedical applications. Here we successfully fabricated smart scaffolds based on thermo-responsive poly(N-isopropylacrylamide) (pNiPAM). Nanoparticles providing localized trigger of heating when irradiated with a short laser burst were found to give rise to remote control of bulk polymer shrinkage. Gold-coated iron oxide nanoparticles were synthesized using wet chemical precipitation methods followed by electrochemical coating. After subsequent functionalization of particles with allyl methyl sulfide, mercaptodecane, cysteamine and poly(ethylene glycol) thiol to enhance stability, detailed biological safety was determined using live/dead staining and cell membrane integrity studies through lactate dehydrogenase (LDH) quantification. The PEG coated HNPs did not show significant cytotoxic effect or adverse cellular response on exposure to 7F2 cells (p < 0.05) and were carried forward for scaffold incorporation. The pNiPAM-HNP composite scaffolds were investigated for their potential as thermally triggered systems using a Q-switched Nd:YAG laser. These studies show that incorporation of HNPs resulted in scaffold deformation after very short irradiation times (seconds) due to internal structural heating. Our data highlights the potential of these hybrid-scaffold constructs for exploitation in drug delivery, using methylene blue as a model drug being released during remote structural change of the scaffold.

Remotely Triggered Drug Release from Gold Nanoparticle-based Systems

Nanoparticles are attractive drug carriers that can combine drug molecules and targeting moieties in order to improve treatment efficacy and reduce unwanted side effects. In addition, activatable nanoparticles may enable drug release in the target sites at accurate timings or conditions, in which drug discharge can be controlled by specific stimuli. Especially, gold nanoparticles provide a great opportunity as drug carriers because of the following advantageous features: i) simple formulation with various sizes and shapes and non-toxicity; ii) easy incorporation of targeting molecules, drugs or other therapeutic molecules on them; iii) triggered drug release by means of external or internal stimuli. In this chapter, we describe relevant examples of the preparation techniques and the performance of various types of gold nanoparticles for drug delivery as well as theranostics.

Visible and near infrared resonance plasmonic enhanced nanosecond laser optoporation of cancer cells

In this paper, we report a light driven, non-invasive cell membrane perforation technique based on the localized field amplification by a nanosecond pulsed laser near gold nanoparticles (AuNPs). The optoporation phenomena is investigated with pulses generated by a Nd:YAG laser for two wavelengths that are either in the visible (532 nm) or near infrared (NIR) (1064 nm). Here, the main objective is to compare on and off localized surface plasmonic resonance (LSPR) to introduce foreign material through the cell membrane using nanosecond laser pulses. The membrane permeability of human melanoma cells (MW278) has been successfully increased as shown by the intake of a fluorescent dye upon irradiation. The viability of this laser driven perforation method is evaluated by propidium iodide exclusion as well as MTT assay. Our results show that up to 25% of the cells are perforated with 532 nm pulses at 50 mJ/cm(2) and around 30% of the cells are perforated with 1064 nm pulses at 1 J/cm(2). With 532 nm pulses, the viability 2 h after treatment is 64% but it increases to 88% 72 h later. On the other hand, the irradiation with 1064 nm pulses leads to an improved 2 h viability of 81% and reaches 98% after 72 h. Scanning electron microscopy images show that the 5 pulses delivered during treatment induce changes in the AuNPs size distribution when irradiated by a 532 nm beam, while this distribution is barely affected when 1064 nm is used.

A plasmon ruler based on nanoscale photothermal effect

The determination of nanoscale distances or distance changes necessitates a nanoscale ruler. In the present paper, distance dependence of particle temperature in an optically heated gold nanoparticle pair is quantitatively investigated to explore the possibility of creating a plasmon ruler based on this effect. The two origins of the distance-dependence, i.e., electromagnetic coupling and thermal accumulative effect, are studied. For the particle temperature, a scaling behavior is found, and it suggests that the decay of particle temperature with the interparticle gap for different particle sizes follows a common exponential decay equation. This scaling behavior is qualitatively explained with a simple dipolar-coupling model combined with a point heat source interaction model. On the basis of this scaling behavior of absorption power, we further establish a plasmon ruler equation relating the particle temperature and the interparticle distance. Our findings can serve as an excellent guideline for designing and optimizing temperature-based plasmon rulers.

Intelligent drug-delivery devices based on micro- and nano-technologies

This review focuses on the current drug-delivery modalities in R&D, as well as commercially available. Intelligent drug-delivery systems are described as novel technological innovations and clinical approaches to improve conventional treatments. These systems differ in methodology of therapeutic administration, intricacy, materials and patient compliance to address numerous clinical conditions that require various pharmacological therapies. These systems have been primarily described as active and passive microelectrical mechanical system devices, injectors and nanoparticle-based therapies, optimized to tailor specific pharmacokinetic profiles. The most critical considerations for the design of these intelligent delivery systems include the controlled release, target specificity, on-demand dosage adjustment, mass transfer and stability of the pharmacological agents. Drug-delivery systems continue to be developed and enhanced to provide better and more sophisticated treatments, promising an improvement in quality of life and extension of life expectancy.

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.

Enhancing of plasmonic photothermal therapy through heat-inducible transgene activity

We explore the synergistic effect of photothermal therapy and gene therapy, simultaneously triggered by silica-gold nanoshells (NS) or hollow gold nanoparticles (HGNPs) in human HeLa cells following near-infrared (NIR) light irradiation. Thermal transfer from NS was higher than that displayed by HGNPs, owing to a differential interaction of the nanomaterial with the biological environment. Under sublethal photothermal conditions, NS and HGNPs effectively modulated the expression levels of a DsRed-monomer reporter gene controlled by the highly heat-inducible human HSP70B promoter, as a function of nanomaterial concentration and length of laser exposure. Hyperthermia treatments at doses that do not promote cell death generated a lethal outcome in HeLa cells harboring the fusogenic GALV-FMG transgene under the control of the HSP70B promoter. Combination of lethal photothermia with the triggering of the cytotoxic transgene resulted in a dramatic increase of the cell-ablation area as a result of the synergistic activity established.

FROM THE CLINICAL EDITOR

In this study photothermal therapy and gene therapy, simultaneously triggered by silica-gold nanoshells or hollow gold nanoparticles, was investigated in human HeLa cells following near-infrared (NIR) light irradiation. It is shown that the combination of lethal photothermia with the triggering of the cytotoxic transgene at sublethal levels results in a synergistic cytotoxic effect in vitro.

Encapsulation of gold nanoparticles into self-assembling protein nanoparticles

BACKGROUND

Gold nanoparticles are useful tools for biological applications due to their attractive physical and chemical properties. Their applications can be further expanded when they are functionalized with biological molecules. The biological molecules not only provide the interfaces for interactions between nanoparticles and biological environment, but also contribute their biological functions to the nanoparticles. Therefore, we used self-assembling protein nanoparticles (SAPNs) to encapsulate gold nanoparticles. The protein nanoparticles are formed upon self-assembly of a protein chain that is composed of a pentameric coiled-coil domain at the N-terminus and trimeric coiled-coil domain at the C-terminus. The self-assembling protein nanoparticles form a central cavity of about 10 nm in size, which is ideal for the encapsulation of gold nanoparticles with similar sizes.

RESULTS

We have used SAPNs to encapsulate several commercially available gold nanoparticles. The hydrodynamic size and the surface coating of gold nanoparticles are two important factors influencing successful encapsulation by the SAPNs. Gold nanoparticles with a hydrodynamic size of less than 15 nm can successfully be encapsulated. Gold nanoparticles with citrate coating appear to have stronger interactions with the proteins, which can interfere with the formation of regular protein nanoparticles. Upon encapsulation gold nanoparticles with polymer coating interfere less strongly with the ability of the SAPNs to assemble into nanoparticles. Although the central cavity of the SAPNs carries an overall charge, the electrostatic interaction appears to be less critical for the efficient encapsulation of gold nanoparticles into the protein nanoparticles.

CONCLUSIONS

The SAPNs can be used to encapsulate gold nanoparticles. The SAPNs can be further functionalized by engineering functional peptides or proteins to either their N- or C-termini. Therefore encapsulation of gold nanoparticles into SAPNs can provide a useful platform to generate a multifunctional biodevices.

Superparamagnetic iron oxide nanoparticle 'theranostics' for multimodality tumor imaging, gene delivery, targeted drug and prodrug delivery

The superparamagnetic iron oxide nanoparticle (SPIO) 'theranostics', which contain imaging probes for tumor diagnosis and therapeutic compounds for therapy in a single nanoparticle, might provide significant benefits compared with exiting tumor imaging and therapeutic strategies. In this review, we summarize the progress of SPIO 'theranostics' that integrate tumor targeting, multimodality imaging, and gene delivery or targeted drug and prodrug delivery. This review describes various methods of SPIO synthesis, surface coating and characterization. Different tumor-targeting strategies, such as antibody fragments, nucleotides and receptor ligands, are discussed to improve SPIO delivery for multimodality imaging. We also examine the utility of SPIOs for gene delivery, siRNA delivery and imaging. Several methods for drug encapsulation and conjugation onto SPIOs are compared for targeted drug delivery, site-specific release and imaging-guided drug delivery. Finally, we also review the pharmacokinetics (including biodistribution) of SPIOs based on their characteristics.

Plasmonic photothermic and stem cell therapy of atherosclerotic plaque as a novel nanotool for angioplasty and artery remodeling

BACKGROUND

Some modern angioplasty techniques drastically affect the geometry of the plaque and the lumen, but have some inherent clinical and technical limitations.

METHODS

A total of 101 Yucatan miniature swine were allocated to the three following groups (34 pigs into 60/15- to 70/40-nm silica-gold nanoparticles (NPs), 34 swine into ferromagnetic group with iron-bearing NPs and delivery in hand of magnetic fields, and 33 in a sirolimus stenting control). Animals in the nanogroup were subdivided further into four subsets according to the delivery approach: (1) Intracoronary infused circulating stem progenitor cells (SPCs), including SP(+) (side population) cells, (2) intracoronary infused, ultrasound-mediated, albumin-coated, gas-filled microbubbles, (3) CD73(+)105(+) SPCs in the composition of a bioengineered on-artery patch (cardiac surgery), (4) CD73(+)CD105(+) SPCs engrafted by manual subadventitial injection (cardiac surgery). NPs were detonated with a microwatt near-infrared (NIR) laser (821 nm, 35-44 W/cm(2) for 7 min of exposure).

RESULTS

Changes of the total atheroma volume (TAV; mm(3)) immediately after the laser irradiation at month 6 in the nanoshell, ferromagnetic, and control groups were -7.54%/-22.92%, -9.7%/-16.84%, and -10.5%/-7.06% (p<0.01), respectively, and in the subsets reached -2.79%/-21.92%, -6.26%/-15.24%, -4.6%/-31.21%, -16.5%/-23.3% (p<0.05), respectively. Some cases of atherothrombosis and distal embolism (23.5%) were documented only in the microbubbles subset. The impact of the therapy on the nonorganic part of the plaque-antiinflammative and antiapoptotic effects, signs of neovascularization, and restoration of artery function-were predominant in the observed subsets with SPCs (p<0.01).

CONCLUSION

Nanoburning, especially in combination with stem cell technologies, is a very challenging technique for altering advanced plaque and holds the promise of revolutionizing state-of-the-art interventional cardiology, assuring destruction of plaque and functional restoration of the vessel wall. It could potentially become the current mechanical and pharmacological treatment.

Cytotoxicity of gold nanoparticles

Nanomaterials are now routinely used in technical as well as medical applications. The very physicochemical properties that favor nanomaterial application are the prime cause that these materials cannot be considered "generally safe." We are still far from predicting the toxicological profile of new nanoparticles, despite continuous attempts to establish a structure-function relation between the physical and chemical properties of nanoparticles and their interactions with biological systems. Herein, we summarize some basic concept to assess nanoparticle toxicity, death pathways, cell cycle, and oxidative stress in response to nanoparticle exposure of cells.

Hybrid gold-iron oxide nanoparticles as a multifunctional platform for biomedical application

Background

Iron oxide nanoparticles (IONPs) have increasing applications in biomedicine, however fears over long term stability of polymer coated particles have arisen. Gold coating IONPs results in particles of increased stability and robustness. The unique properties of both the iron oxide (magnetic) and gold (surface plasmon resonance) result in a multimodal platform for use as MRI contrast agents and as a nano-heater.

Results

Here we synthesize IONPs of core diameter 30 nm and gold coat using the seeding method with a poly(ethylenimine) intermediate layer. The final particles were coated in poly(ethylene glycol) to ensure biocompatibility and increase retention times in vivo. The particle coating was monitored using FTIR, PCS, UV–vis absorption, TEM, and EDX. The particles appeared to have little cytotoxic effect when incubated with A375M cells. The resultant hybrid nanoparticles (HNPs) possessed a maximal absorbance at 600 nm. After laser irradiation in agar phantom a ΔT of 32°C was achieved after only 90 s exposure (50 μgmL^-1). The HNPs appeared to decrease T₂ values in line with previously clinically used MRI contrast agent Feridex®.

Conclusions

The data highlights the potential of these HNPs as dual function MRI contrast agents and nano-heaters for therapies such as cellular hyperthermia or thermo-responsive drug delivery.

In situ measurement of bovine serum albumin interaction with gold nanospheres

We present in situ observations of adsorption of bovine serum albumin (BSA) on citrate-stabilized gold nanospheres. We implemented scattering correlation spectroscopy as a tool to quantify changes in the nanoparticle brownian motion resulting from BSA adsorption onto the nanoparticle surface. Protein binding was observed as an increase in the nanoparticle hydrodynamic radius. Our results indicate the formation of a protein monolayer at similar albumin concentrations as those found in human blood. Additionally, by monitoring the frequency and intensity of individual scattering events caused by single gold nanoparticles passing the observation volume, we found that BSA did not induce colloidal aggregation, a relevant result from the toxicological viewpoint. Moreover, to elucidate the thermodynamics of the gold nanoparticle-BSA association, we measured an adsorption isotherm which was best described by an anticooperative binding model. The number of binding sites based on this model was consistent with a BSA monolayer in its native state. In contrast, experiments using poly(ethylene glycol)-capped gold nanoparticles revealed no evidence for adsorption of BSA.

Multimode resonances in silver nanocuboids

A rich variety of dipolar and higher order plasmon resonances have been predicted for nanoscale cubes and parallopipeds of silver, in contrast to the simple dipolar modes found on silver nanospheres or nanorods. However, in general, these multimode resonances are not readily detected in experimental colloidal ensembles, due primarily to the usual variation of size and shape of the particles obscuring or blending the individual extinction peaks. Recently, methods have been found to prepare silver parallopipeds with unprecedented shape control by nucleating the silver onto a tightly controlled suspension of gold nanorods (Okuno, Y.; Nishioka, K.; Kiya, A.; Nakashima, N.; Ishibashi, A.; Niidome, Y. Uniform and Controllable Preparation of Au-Ag Core-Shell Nanorods Using Anisotropic Silver Shell Formation on Gold Nanorods. Nanoscale 2010, 2, 1489-1493). The optical extinction spectra of suspensions of such monodisperse particles are found to contain multiple extinction peaks, which we show here to be due to the multimode resonances predicted by theoretical studies. Control of the radius of the nanoparticle edges is found to be an effective way to turn some of these modes on or off. These nanoparticles provide a flexible platform for the excitation, manipulation, and exploration of higher order plasmon resonances.

CYTOTOXICITY AND DIFFERENTIATION EFFECTS OF GOLD NANOPARTICLES TO HUMAN BONE MARROW MESENCHYMAL STEM CELLS

Gold nanoparticles (GNPs) are widely used in chemical sensing, drug delivery, biomedical imaging, and photothermal therapy due to their strong and size-tunable surface plasmon resonance, fluorescence, and easy-surface functionalization. In this study, we investigated the effects of water-dispersed GNPs on the cytotoxicity and differentiation of human bone marrow mesenchymal stem cells (hBMSCs) and the associated death pathway. The results showed that the viability of hBMSCs was dependent upon the size of GNPs. Further, GNPs at the smallest size exhibited the highest cytotoxicity after treatment for 5 days and also substantially suppressed the number of colony-forming unit-fibroblast (CFU-F) of hBMSCs after continuous exposure for 21 days. Although large and medium sizes of GNPs had minor cytotoxicity to the cells, the sizes of CFU-F formed in the groups treated with GNPs at medium and large sizes were smaller compared to the control group. Further study of the cell death pathway using GNPs at medium size found that GNPs triggered hBMSCs necrosis, possibly by oxidative stress after GNPs were endocytosed. In addition, GNPs exerted the inhibitory effects on induced osteogenesis and adipogenesis of hBMSCs. Alkaline phosphatase (ALP) activity and calcium mineralization during osteogenic induction as well as the accumulation of triacylglycerides in adipogenic hBMSCs were repressed significantly by coculturing with GNPs at medium size. Our results suggest that the application of GNPs as long-term tracers for the activities of mesenchymal stem cells (MSCs) should be carefully evaluated.

A novel study of antibacterial activity of copper iodide nanoparticle mediated by DNA and membrane damage

In this article potential activity of nanoparticles (NPs) of copper iodide (CuI) as an antibacterial agent has been presented. The nano particles are synthesized by co-precipitation method with an average size of 8 nm as determined by Transmission Electron Microscope (TEM). The average charge of the NPs is -21.5 mV at pH 7 as obtained by zeta potential measurement and purity is determined by XRD. These NPs are able to kill both gram positive and gram negative bacteria. Among the bacteria tested, DH5α is more sensitive but Bacillus subtilis is more resistant to NPs of CuI. Consequently, the MIC and MBC values of DH5α is least (0.066 mg/ml and 0.083 mg/ml respectively) and B. subtilis is highest (0.15 mg/ml and 0.18 mg/ml respectively) among the tested bacterial strains. From our studies it is inferred that CuI NPs produce reactive oxygen species (ROS) in both gram negative and gram positive bacteria and it also causes ROS mediated DNA damage for the suppression of transcription as revealed by reporter gene assay. Probably ROS is formed on the surface of NPs of CuI in presence of amine functional groups of various biological molecules. Furthermore they induce membrane damage as determined by atomic force microscopy (AFM). Thus production of ROS and membrane damage are major mechanisms of the bactericidal activity of these NPs of CuI.

Calcium phosphate ceramic systems in growth factor and drug delivery for bone tissue engineering: a review

Calcium phosphates (CaPs) are the most widely used bone substitutes in bone tissue engineering due to their compositional similarities to bone mineral and excellent biocompatibility. In recent years, CaPs, especially hydroxyapatite and tricalcium phosphate, have attracted significant interest in simultaneous use as bone substitute and drug delivery vehicle, adding a new dimension to their application. CaPs are more biocompatible than many other ceramic and inorganic nanoparticles. Their biocompatibility and variable stoichiometry, thus surface charge density, functionality, and dissolution properties, make them suitable for both drug and growth factor delivery. CaP matrices and scaffolds have been reported to act as delivery vehicles for growth factors and drugs in bone tissue engineering. Local drug delivery in musculoskeletal disorder treatments can address some of the critical issues more effectively and efficiently than the systemic delivery. CaPs are used as coatings on metallic implants, CaP cements, and custom designed scaffolds to treat musculoskeletal disorders. This review highlights some of the current drug and growth factor delivery approaches and critical issues using CaP particles, coatings, cements, and scaffolds towards orthopedic and dental applications.

Mechanisms of nanoparticle-mediated photomechanical cell damage

Laser-assisted killing of gold nanoparticle targeted macrophages was investigated. Using pressure transient detection, flash photography and transmission electron microscopy (TEM) imaging, we studied the mechanism of single cell damage by vapor bubble formation around gold nanospheres induced by nanosecond laser pulses. The influence of the number of irradiating laser pulses and of particle size and concentration on the threshold for acute cell damage was determined. While the single pulse damage threshold is independent of the particle size, the threshold decreases with increasing particle size when using trains of pulses. The dependence of the cell damage threshold on the nanoparticle concentration during incubation reveals that particle accumulation and distribution inside the cell plays a key role in tissue imaging or cell damaging.

Does shape matter? Bioeffects of gold nanomaterials in a human skin cell model

Gold nanomaterials (AuNMs) have distinctive electronic and optical properties, making them ideal candidates for biological, medical, and defense applications. Therefore, it is imperative to evaluate the potential biological impact of AuNMs before employing them in any application. This study investigates two AuNMs with different aspect ratios (AR) on mediation of biological responses in the human keratinocyte cell line (HaCaT) to model potential skin exposure to these AuNMs. The cellular responses were evaluated by cell viability, reactive oxygen species (ROS) generation, alteration in gene and protein expression, and inflammatory response. Gold nanospheres, nominally 20 nm in diameter and coated with mercaptopropane sulfonate (AuNS-MPS), formed agglomerates when dispersed in cell culture media, had a large fractal dimension (D(f) = 2.57 ± 0.4) (i.e., tightly bound and densely packed) and were found to be nontoxic even at the highest dose of 100 μg/mL. Highly uniform, 16.7 nm diameter, and 43.8 nm long polyethylene glycol-capped gold nanorods (AuNR-PEG) also formed agglomerates when dispersed into the cell culture media. However, the agglomerates had a smaller fractal dimension (D(f) = 1.28 ± 0.08) (i.e., loosely bound) and were found to be cytotoxic to the HaCaT cells, with a significant decrease in cell viability occurring at 25 μg/mL and higher. Moreover, AuNR-PEG caused significant ROS production and up-regulated several genes involved in cellular stress and toxicity. These results, combined with increased levels of inflammatory and apoptotic proteins, demonstrated that the AuNR-PEG induced apoptosis. Exposure to AuNS-MPS, however, did not show any of the detrimental effects observed from the AuNR-PEG. Therefore, we conclude that shape appears to play a key role in mediating the cellular response to AuNMs.

Theoretical study on the possible use of SiC microparticles as photothermal agents for the heating of bacteria

Gold nanoparticles exhibiting surface plasmon resonances have been considered as photothermal agents for the selective destruction of bacteria by visible to near-infrared radiation. Here, we consider theoretically the possible complementary use of sub-micron silicon carbide (SiC) particles as photothermal agents for the heating of bacteria by pulsed mid-infrared (MIR) radiation. A SiC microparticle can exhibit surface phonon resonances in the MIR. Similar to the effect of surface plasmon resonances in gold nanoparticles, this could lead to enhanced absorption at the resonant wavelength and strong heating of the microparticle locally. If the heating is sufficient, this might lead to damage of bacterial cells adjacent to SiC particles. We estimate the heating of sub-micron SiC particles in a water medium under various pulse lengths of radiation at wavelength 10.6 μm. Noting that SiC is being investigated as a biocompatible material that could be functionalized for biomedical applications, and that an appropriately roughened SiC surface could be expected to exhibit similar surface phonon resonances, we speculate that enhanced heating under MIR radiation may be useful for in vitro sterilization of such surfaces.

Silica-metal core-shell nanostructures

Silica-metal nanostructures consisting of silica cores and metal nanoshells attract a lot of attention because of their unique properties and potential applications ranging from catalysis and biosensing to optical devices and medicine. The important feature of these nanostructures is the possibility of controlling their properties by the variation of their geometry, shell morphology and shell material. This review is devoted to silica-noble metal core-shell nanostructures; specifically, it outlines the main methods used for the preparation and surface modification of silica particles and presents the major strategies for the formation of metal nanoshells on the modified silica particles. A special emphasis is given to the Stöber method, which is relatively simple, effective and well verified for the synthesis of large and highly uniform silica particles (with diameters from 100 nm to a few microns). Next, the surface chemistry of these particles is discussed with a special focus on the attachment of specific organic groups such as aminopropyl or mercaptopropyl groups, which interact strongly with metal species. Finally, the synthesis, characterization and application of various silica-metal core-shell nanostructures are reviewed, especially in relation to the siliceous cores with gold or silver nanoshells. Nowadays, gold is most often used metal for the formation of nanoshells due to its beneficial properties for many applications. However, other metals such as silver, platinum, palladium, nickel and copper were also used for fabrication of core-shell nanostructures. Silica-metal nanostructures can be prepared using various methods, for instance, (i) growth of metal nanoshells on the siliceous cores with deposited metal nanoparticles, (ii) reduction of metal species accompanied by precipitation of metal nanoparticles on the modified silica cores, and (iii) formation of metal nanoshells under ultrasonic conditions. A special emphasis is given to the seed-mediated growth, where metal nanoshells are formed on the modified silica cores with deposited metal nanoparticles. This strategy assures a good control of the nanoshell thickness as well as its surface properties.

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).

Fate and toxicity of metallic and metal-containing nanoparticles for biomedical applications

It is important to obtain a better understanding of the uptake, trafficking, pharmacokinetics, clearance, and role of nanomaterials in biological systems, so that their possible undesirable effects can be avoided. A number of metallic or metal-containing nanomaterials, such as gold nanoparticles and nanorods, quantum dots, iron oxides nanoparticles, and endohedral metallofullerenes, have already been or will soon become very promising for biomedical applications. This review presents a summary of currently available data on the fate and toxicity of these metallic or metal-containing nanoparticles based on animal studies. Several issues regarding the nanotoxicity assessment and future directions on the study of the fate of these nanoparticles are also proposed.

Electronic and vibrational spectra of novel Lanreotide peptide capped gold nanoparticles

Lanreotide, a somatostatin analogue peptide used for peptide receptor mediated therapy in metastatic neuroendocrine tumors, was used as capping agent of gold nanoparticles (GNPs) obtained by citrate reduction method. The displacement of the citrate groups from the GNPs surface by Lanreotide (LAN) molecules was evidenced by infrared and Raman spectra. The nanoparticles system, Au@LAN, was also characterized from HRTEM (High-Resolution Transmission Electron Microscopy) and Z-contrast images, UV-vis and EDS spectra. The stability on aging in water solution of the composite is discussed from the UV-vis spectra. The affinity constant of Au@LAN conjugate, calculated from Capillary Zone Electrophoresis data, was found to be 0.52. All the experimental evidence supports that the gold nanoparticles are effectively capped by the Lanreotide molecules through relatively strong covalent interactions. This result opens the possibility of combining the optical properties of gold nanoparticles and of Lanreotide molecule to form a bifunctional system for potential biomedical applications.