Near-infrared-resonant gold/gold sulfide nanoparticles as a photothermal cancer therapeutic agent

Photothermal response of near-infrared-absorbing NanoGUMBOS

The photothermal properties of several near-infrared-absorbing nanoparticles derived from group of uniform materials based on organic salts (GUMBOS) and composed of cationic dyes coupled with biocompatible anions are evaluated. These nanoparticles were synthesized using a reprecipitation method performed at various pH values: 2.0, 5.0, 7.0, 9.0, and 11.0. The cations for the nanoparticles derived from GUMBOS (nanoGUMBOS), [1048] and [1061], have absorbance maxima at wavelengths overlapping with human soft tissue absorbance minima. Near-infrared-absorbing nanoGUMBOS excited with a 1064 nm continuous laser led to heat generation, with an average temperature increase of 20.4 ± 2.7 °C. Although the [1061][Deoxycholate] nanoGUMBOS generated the highest temperature increase (23.7 ± 2.4 °C), it was the least photothermally efficient compound (13.0%) due to its relatively large energy band gap of 0.892 eV. The more photothermally efficient compound [1048][Ascorbate] (64.4%) had a smaller energy band gap of 0.861 eV and provided an average photothermal temperature increase of 21.0 ± 2.1 °C.

Plasmonic nanobubbles as tunable cellular probes for cancer theranostics

This review is focused on a novel cellular probe, the plasmonic nanobubble (PNB), which has the dynamically tunable and multiple functions of imaging, diagnosis, delivery, therapy and, ultimately, theranostics. The concept of theranostics was recently introduced in order to unite the clinically important stages of treatment, namely diagnosis, therapy and therapy guidance, into one single, rapid and highly accurate procedure. Cell level theranostics will have far-reaching implications for the treatment of cancer and other diseases at their earliest stages. PNBs were developed to support cell level theranostics as a new generation of on-demand tunable cellular probes. A PNB is a transient vapor nanobubble that is generated within nanoseconds around an overheated plasmonic nanoparticle with a short laser pulse. In the short term, we expect that PNB technology will be rapidly adaptable to clinical medicine, where the single cell resolution it provides will be critical for diagnosing incipient or residual disease and eliminating cancer cells, while leaving healthy cells intact. This review discusses mechanisms of plasmonic nanobubbles and their biomedical applications with the focus on cancer cell theranostics.

Perspectives of nanotechnology in minimally invasive therapy of breast cancer

Breast cancer, the most common type of cancer among women in the western world, affects approximately one out of every eight women over their lifetime. In recognition of the high invasiveness of surgical excision and severe side effects of chemical and radiation therapies, increasing efforts are made to seek minimally invasive modalities with fewer side effects. Nanoparticles (<100 nm in size) have shown promising capabilities for delivering targeted therapeutic drugs to cancer cells and confining the treatment mainly within tumors. Additionally, some nanoparticles exhibit distinct properties, such as conversion of photonic energy into heat, and these properties enable eradication of cancer cells. In this review, current utilization of nanostructures for cancer therapy, especially in minimally invasive therapy, is summarized with a particular interest in breast cancer.

Infrared light-absorbing gold/gold sulfide nanoparticles induce cell death in esophageal adenocarcinoma

Gold nanoparticles and near infrared-absorbing light are each innocuous to tissue but when combined can destroy malignant tissue while leaving healthy tissue unharmed. This study investigated the feasibility of photothermal ablation therapy for esophageal adenocarcinoma using chitosan-coated gold/gold sulfide (CS-GGS) nanoparticles. A rat esophagoduodenal anastomosis model was used for the in vivo ablation study, and three human esophageal cell lines were used to study the response of cancer cells and benign cells to near infrared light after treatment with CS-GGS. The results indicate that both cancerous tissue and cancer cells took up more gold nanoparticles and were completely ablated after exposure to near infrared light. The benign tissue and noncancerous cells showed less uptake of these nanoparticles, and remained viable after exposure to near infrared light. CS-GGS nanoparticles could provide an optimal endoluminal therapeutic option for near infrared light ablation of esophageal cancer.

Enhanced drug delivery via hyperthermal membrane disruption using targeted gold nanoparticles with PEGylated Protein-G as a cofactor

Gold nanoparticles (GNPs) with near infrared (NIR) plasmon resonance have been promisingly used in photothermal cancer therapy as a less invasive treatment. Recombinant Protein-G (ProG) was PEGylated to act as a cofactor to immobilize immunoglobulins (IgGs) on GNPs by the Fc region, resulting in optimal orientation of IgGs for efficient cancer targeting. In-vitro studies showed that HER-2 overexpressing breast cancer cells, SK-BR-3, were efficiently targeted and ablated at a laser power of 900 J/cm(2) (5 W/cm(2) for 3 min). However, as a means of enhancing treatment efficacy by increasing cellular sensitivity to chemotherapeutic agents, we showed that GNP exposure to lower power laser resulted in small disruptions of cell membrane due to localized hyperthermia. This did not lead to cell death but provided a mechanism for killing cancer cells by providing enhanced uptake of drug molecules thus leading to a new avenue for hyperthermia-anticancer drug combined cancer therapeutics.

FROM THE CLINICAL EDITOR

PEGylated recombinant Protein-G was used as a cofactor to optimize the orientation of IgGs providing "target seeking" properties to gold nanoparticles used in photothermal cancer therapy. The system demonstrated excellent properties in cancer therapy, with the hope and expectation of future clinical translation.

Prospects of nano-material in breast cancer management

Breast cancer evaluation and early diagnosis are core complexity worldwide and an ambiguity for scientists till date. Nano-materials are innovative tools for rapid diagnosis and therapy, which may induce an immense result in the field of oncology. Their exceptional size-dependent properties make them special and superior materials and quite indispensable in several fields of the human activities. The major obstacle in finding cure for malignant breast cancer is to increase in development of resistances for tumors to the therapeutic treatments. The widespread mammo-graph particle is being developed by nations to diagnosis disease in primitive stage to decline the mortality rates caused by breast carcinoma. The advancement of nano-particle based diagnostic tools facilitates in evaluation and provides encouraging development in breast cancer therapeutics. In this compact review, efforts have been made to compose the current advancements in the area of functional nano-particles. Furthermore, in vivo and in vitro applications of nano-materials in breast cancer management are also discussed.

Design maps for the hyperthermic treatment of tumors with superparamagnetic nanoparticles

A plethora of magnetic nanoparticles has been developed and investigated under different alternating magnetic fields (AMF) for the hyperthermic treatment of malignant tissues. Yet, clinical applications of magnetic hyperthermia are sporadic, mostly due to the low energy conversion efficiency of the metallic nanoparticles and the high tissue concentrations required. Here, we study the hyperthermic performance of commercially available formulations of superparamagnetic iron oxide nanoparticles (SPIOs), with core diameter of 5, 7 and 14 nm, in terms of absolute temperature increase ΔT and specific absorption rate (SAR). These nanoparticles are operated under a broad range of AMF conditions, with frequency f varying between 0.2 and 30 MHz; field strength H ranging from 4 to 10 kA m(-1); and concentration cMNP varying from 0.02 to 3.5 mg ml(-1). At high frequency field (∼30 MHz), non specific heating dominates and ΔT correlates with the electrical conductivity of the medium. At low frequency field (<1 MHz), non specific heating is negligible and the relaxation of the SPIO within the AMF is the sole energy source. We show that the ΔT of the medium grows linearly with cMNP , whereas the SARMNP of the magnetic nanoparticles is independent of cMNP and varies linearly with f and H(2) . Using a computational model for heat transport in a biological tissue, the minimum requirements for local hyperthermia (Ttissue >42°C) and thermal ablation (Ttissue >50°C) are derived in terms of cMNP , operating AMF conditions and blood perfusion. The resulting maps can be used to rationally design hyperthermic treatments and identifying the proper route of administration - systemic versus intratumor injection - depending on the magnetic and biodistribution properties of the nanoparticles.

Multifunctional gold nanoparticles for diagnosis and therapy of disease

Gold nanoparticles (AuNPs) have a number of physical properties that make them appealing for medical applications. For example, the attenuation of X-rays by gold nanoparticles has led to their use in computed tomography imaging and as adjuvants for radiotherapy. AuNPs have numerous other applications in imaging, therapy and diagnostic systems. The advanced state of synthetic chemistry of gold nanoparticles offers precise control over physicochemical and optical properties. Furthermore gold cores are inert and are considered to be biocompatible and nontoxic. The surface of gold nanoparticles can easily be modified for a specific application, and ligands for targeting, drugs or biocompatible coatings can be introduced. AuNPs can be incorporated into larger structures such as polymeric nanoparticles or liposomes that deliver large payloads for enhanced diagnostic applications, efficiently encapsulate drugs for concurrent therapy or add additional imaging labels. This array of features has led to the aforementioned applications in biomedical fields, but more recently in approaches where multifunctional gold nanoparticles are used for multiple methods, such as concurrent diagnosis and therapy, so-called theranostics. This review covers basic principles and recent findings in gold nanoparticle applications for imaging, therapy and diagnostics, with a focus on reports of multifunctional AuNPs.

Anti-CD30-targeted gold nanoparticles for photothermal therapy of L-428 Hodgkin's cell

Purpose

Due to the efficient bioconjugation and highly photothermal effect, gold nanoparticles can stain receptor-overexpressing cancer cells through specific targeting of ligands to receptors, strongly absorb specific light and efficiently convert it into heat based on the property of surface plasmon resonance, and then induce the localized protein denaturation and cell death.

Methods

Two gold nanoparticle–antibody conjugates, gold-BerH2 antibody (anti-CD30 receptor) and gold-ACT1 antibody (anti-CD25-receptor), were synthesized. Gold-BerH2 conjugates can specifically bind to the surface of L-428 Hodgkin’s cells, and gold-ACT1 conjugates were used for the control. The gold nanoparticle-induced L-428 cell-killing experiments were implemented with different experimental parameters.

Results

At a relatively low concentration of gold and short incubation time, the influence of cytotoxicity of gold on cell viability can be overlooked. Under laser irradiation at suitable power, the high killing efficiency of gold-targeted L-428 cells was achieved, but little damage was done to nontargeted cancer cells.

Conclusion

Gold nanoparticle-mediated photothermal therapy provides a relatively safe therapeutic technique for cancer treatment.

The chemistry of the sulfur-gold interface: in search of a unified model

Over the last three decades, self-assembled molecular films on solid surfaces have attracted widespread interest as an intellectual and technological challenge to chemists, physicists, materials scientists, and biologists. A variety of technological applications of nanotechnology rely on the possibility of controlling topological, chemical, and functional features at the molecular level. Self-assembled monolayers (SAMs) composed of chemisorbed species represent fundamental building blocks for creating complex structures by a bottom-up approach. These materials take advantage of the flexibility of organic and supramolecular chemistry to generate synthetic surfaces with well-defined chemical and physical properties. These films already serve as structural or functional parts of sensors, biosensors, drug-delivery systems, molecular electronic devices, protecting capping for nanostructures, and coatings for corrosion protection and tribological applications. Thiol SAMs on gold are the most popular molecular films because the resulting oxide-free, clean, flat surfaces can be easily modified both in the gas phase and in liquid media under ambient conditions. In particular, researchers have extensively studied SAMs on Au(111) because they serve as model systems to understand the basic aspects of the self-assembly of organic molecules on well-defined metal surfaces. Also, great interest has arisen in the surface structure of thiol-capped gold nanoparticles (AuNPs) because of simple synthesis methods that produce highly monodisperse particles with controllable size and a high surface/volume ratio. These features make AuNPs very attractive for technological applications in fields ranging from medicine to heterogeneous catalysis. In many applications, the structure and chemistry of the sulfur-gold interface become crucial since they control the system properties. Therefore, many researchers have focused on understanding of the nature of this interface on both planar and nanoparticle thiol-covered surfaces. However, despite the considerable theoretical and experimental efforts made using various sophisticated techniques, the structure and chemical composition of the sulfur-gold interface at the atomic level remains elusive. In particular, the search for a unified model of the chemistry of the S-Au interface illustrates the difficulty of determining the surface chemistry at the nanoscale. This Account provides a state-of-the-art analysis of this problem and raises some questions that deserve further investigation.

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.

Vascular-targeted photothermal therapy of an orthotopic murine glioma model

AIM

To develop nanoshells for vascular-targeted photothermal therapy of glioma.

MATERIALS & METHODS

The ability of nanoshells conjugated to VEGF and/or poly(ethylene glycol) (PEG) to thermally ablate VEGF receptor-2-positive endothelial cells upon near-infrared laser irradiation was evaluated in vitro. Subsequent in vivo studies evaluated therapy in mice bearing intracerebral glioma tumors by exposing tumors to near-infrared light after systemically delivering saline, PEG-coated nanoshells, or VEGF-coated nanoshells. The treatment effect was monitored with intravital microscopy and histology.

RESULTS

VEGF-coated but not PEG-coated nanoshells bound VEGF receptor-2-positive cells in vitro to enable targeted photothermal ablation. In vivo, VEGF targeting doubled the proportion of nanoshells bound to tumor vessels and vasculature was disrupted following laser exposure. Vessels were not disrupted in mice that received saline. The normal brain was unharmed in all treatment and control mice.

CONCLUSION

Nanoshell therapy can induce vascular disruption in glioma.

Targeted cancer therapy by immunoconjugated gold-gold sulfide nanoparticles using Protein G as a cofactor

Gold-gold sulfide nanoparticles (GGS-NPs) fabricated from chloroauric acid and sodium thiosulfate show unique near infrared (NIR) absorption that renders them as a promising candidate for photothermal cancer therapy. To improve targeting efficiency, we developed a versatile method to allow ordered immunoconjugation of antibodies on the surfaces of these nanoparticles via a PEGylated recombinant Protein G (ProG). The PEGylated ProG was prepared with orthopyridyldisulfide-polyethylene glycol-succinimidyl valerate, average MW 2000 (OPSS-PEG-SVA), to first allow the self-assembly of ProG on the nanoparticles, subsequently antibodies were added to this construct to enable active targeting. The bioconjugated GGS-NPs were characterized by TEM, NIR-spectra, dynamic light scattering and modified immunoassay. In in vitro studies, the ProG-conjugated GGS-NPs with bound mouse anti c-erbB-2 (HER-2) immunoglobulin G (IgG) successfully targeted the HER-2 overexpressing breast cancer cell, SK-BR-3. Extensive cell death was observed for the targeted SK-BR-3 line at a low laser power of 540 J (3 W cm(-2) for 3 min) while the control breast cancer cell (low expressing HER-2), HTB-22 survived. Using PEGylated ProG as a cofactor for immobilization of antibodies offers a promising strategy to functionalize various IgGs on nanoparticles for engineering their biomedical applications in cancer therapeutics.

The golden age: gold nanoparticles for biomedicine

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).

Multifunctional plasmonic shell-magnetic core nanoparticles for targeted diagnostics, isolation, and photothermal destruction of tumor cells

Cancer is the greatest challenge in human healthcare today. Cancer causes 7.6 million deaths and economic losses of around 1 trillion dollars every year. Early diagnosis and effective treatment of cancer are crucial for saving lives. Driven by these needs, we report the development of a multifunctional plasmonic shell-magnetic core nanotechnology-driven approach for the targeted diagnosis, isolation, and photothermal destruction of cancer cells. Experimental data show that aptamer-conjugated plasmonic/magnetic nanoparticles can be used for targeted imaging and magnetic separation of a particular kind of cell from a mixture of different cancer cells. A targeted photothermal experiment using 670 nm light at 2.5 W/cm(2) for 10 min resulted selective irreparable cellular damage to most of the cancer cells. We also showed that the aptamer-conjugated magnetic/plasmonic nanoparticle-based photothermal destruction of cancer cells is highly selective. We discuss the possible mechanism and operating principle for the targeted imaging, separation, and photothermal destruction using magnetic/plasmonic nanotechnology.

In vivo particle tracking and photothermal ablation using plasmon-resonant gold nanostars

Gold nanostars offer unique plasmon properties that efficiently transduce photon energy into heat for photothermal therapy. Nanostars, with their small core size and multiple long thin branches, exhibit high absorption cross-sections that are tunable in the near-infrared region with relatively low scattering effect, making them efficient photothermal transducers. Here, we demonstrate particle tracking and photothermal ablation both in vitro and in vivo. Using SKBR3 breast cancer cells incubated with bare nanostars, we observed photothermal ablation within 5 minutes of irradiation (980-nm continuous-wave laser, 15 W/cm2). On a mouse injected systemically with PEGylated nanostars for 2 days, extravasation of nanostars was observed and localized photothermal ablation was demonstrated on a dorsal window chamber within 10 minutes of irradiation (785-nm continuous-wave laser, 1.1 W/cm2). These preliminary results of plasmon-enhanced localized hyperthermia are encouraging and have illustrated the potential of gold nanostars as efficient photothermal agents in cancer therapy.

FROM THE CLINICAL EDITOR

Gold nanostars are tunable in the near-infrared region with low scattering, thus enable photothermal therapy. Encouraging preliminary results of plasmon-enhanced localized hyperthermia both in vitro and in vivo demonstrate that Au nanostars may be efficient photothermal agents for cancer therapy.

Facile synthesis of superparamagnetic Fe3O4@Au nanoparticles for photothermal destruction of cancer cells

Superparamagnetic Fe(3)O(4) nanoparticles with positive surface ξ-potential were synthesized via a solvothermal route. After Fe(3)O(4) was mixed with HAuCl(4) and NaBH(4), the reduced Au nanoparticles could be directly adsorbed onto the surface of Fe(3)O(4) nanoparticles. The as-synthesized nanocomposites were successfully applied to photothermal destruction of cancer cells.

Ultrasmall hollow gold-silver nanoshells with extinctions strongly red-shifted to the near-infrared

Hollow gold-silver nanoshells having systematically varying sizes between 40 and 100 nm were prepared. These particles consist of a hollow spherical silver shell surrounded by a thin gold layer. By varying the volume of the gold stock solution added to suspensions of small silver-core templates, we tailored the hollow gold-silver nanoshells to possess strong tunable optical extinctions that range from the visible to the near-IR spectral regions, with extinctions routinely centered at ∼950 nm. The size and morphology of these core/shell nanoparticles were characterized by dynamic light scattering (DLS), field emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM). Separately, X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) were used for measuring their elemental composition; UV-vis spectroscopy was used to evaluate their optical properties. Given their relatively small size compared to other nanoparticles that absorb strongly at near IR wavelengths, these easy-to-synthesize particles should find use in applications that require ultrasmall nanoparticles with extinctions comfortably beyond visible wavelengths (e.g., medicinal therapies, diagnostic imaging, nanofluidics, and display technologies).

Assessment of the evolution of cancer treatment therapies

Cancer therapy has been characterized throughout history by ups and downs, not only due to the ineffectiveness of treatments and side effects, but also by hope and the reality of complete remission and cure in many cases. Within the therapeutic arsenal, alongside surgery in the case of solid tumors, are the antitumor drugs and radiation that have been the treatment of choice in some instances. In recent years, immunotherapy has become an important therapeutic alternative, and is now the first choice in many cases. Nanotechnology has recently arrived on the scene, offering nanostructures as new therapeutic alternatives for controlled drug delivery, for combining imaging and treatment, applying hyperthermia, and providing directed target therapy, among others. These therapies can be applied either alone or in combination with other components (antibodies, peptides, folic acid, etc.). In addition, gene therapy is also offering promising new methods for treatment. Here, we present a review of the evolution of cancer treatments, starting with chemotherapy, surgery, radiation and immunotherapy, and moving on to the most promising cutting-edge therapies (gene therapy and nanomedicine). We offer an historical point of view that covers the arrival of these therapies to clinical practice and the market, and the promises and challenges they present.

Specific cell targeting with nanobody conjugated branched gold nanoparticles for photothermal therapy

Branched gold nanoparticles are potential photothermal therapy agents because of their large absorption cross section in the near-infrared window. Upon laser irradiation they produce enough heat to destroy tumor cells. In this work, branched gold nanoparticles are biofunctionalized with nanobodies, the smallest fully functional antigen-binding fragments evolved from the variable domain, the VHH, of a camel heavy chain-only antibody. These nanobodies bind to the HER2 antigen which is highly expressed on breast and ovarian cancer cells. Flow cytometric analysis and dark field images of HER2 positive SKOV3 cells incubated with anti-HER2 conjugated branched gold nanoparticles show specific cell targeting. Laser irradiation studies reveal that HER2 positive SKOV3 cells exposed to the anti-HER2 targeted branched gold nanoparticles are destroyed after five minutes of laser treatment at 38 W/cm(2) using a 690 nm continuous wave laser. Starting from a nanoparticle optical density of 4, cell death is observed, whereas the control samples, nanoparticles with anti-PSA nanobodies, nanoparticles only, and laser only, do not show any cell death. These results suggest that this new type of bioconjugated branched gold nanoparticles are effective antigen-targeted photothermal therapeutic agents for cancer treatment.

T cells enhance gold nanoparticle delivery to tumors in vivo

Gold nanoparticle-mediated photothermal therapy (PTT) has shown great potential for the treatment of cancer in mouse studies and is now being evaluated in clinical trials. For this therapy, gold nanoparticles (AuNPs) are injected intravenously and are allowed to accumulate within the tumor via the enhanced permeability and retention (EPR) effect. The tumor is then irradiated with a near infrared laser, whose energy is absorbed by the AuNPs and translated into heat. While reliance on the EPR effect for tumor targeting has proven adequate for vascularized tumors in small animal models, the efficiency and specificity of tumor delivery in vivo, particularly in tumors with poor blood supply, has proven challenging. In this study, we examine whether human T cells can be used as cellular delivery vehicles for AuNP transport into tumors. We first demonstrate that T cells can be efficiently loaded with 45 nm gold colloid nanoparticles without affecting viability or function (e.g. migration and cytokine production). Using a human tumor xenograft mouse model, we next demonstrate that AuNP-loaded T cells retain their capacity to migrate to tumor sites in vivo. In addition, the efficiency of AuNP delivery to tumors in vivo is increased by more than four-fold compared to injection of free PEGylated AuNPs and the use of the T cell delivery system also dramatically alters the overall nanoparticle biodistribution. Thus, the use of T cell chaperones for AuNP delivery could enhance the efficacy of nanoparticle-based therapies and imaging applications by increasing AuNP tumor accumulation.

A new era for cancer treatment: gold-nanoparticle-mediated thermal therapies

Nanotechnology-based cancer treatment approaches potentially provide localized, targeted therapies that aim to enhance efficacy, reduce side effects, and improve patient quality of life. Gold-nanoparticle-mediated hyperthermia shows particular promise in animal studies, and early clinical testing is currently underway. In this article, the rapidly evolving field of gold nanoparticle thermal therapy is reviewed, highlighting recent literature and describing current challenges to clinical translation of the technology.

Zinc oxide nanoparticles for selective destruction of tumor cells and potential for drug delivery applications

IMPORTANCE OF THE FIELD

Metal oxide nanoparticles, including zinc oxide, are versatile platforms for biomedical applications and therapeutic intervention. There is an urgent need to develop new classes of anticancer agents, and recent studies demonstrate that ZnO nanomaterials hold considerable promise.

AREAS COVERED IN THIS REVIEW

This review analyzes the biomedical applications of metal oxide and ZnO nanomaterials under development at the experimental, preclinical and clinical levels. A discussion regarding the advantages, approaches and limitations surrounding the use of metal oxide nanoparticles for cancer applications and drug delivery is presented. The scope of this article is focused on ZnO, and other metal oxide nanomaterial systems, and their proposed mechanisms of cytotoxic action, as well as current approaches to improve their targeting and cytotoxicity against cancer cells.

WHAT THE READER WILL GAIN

This review aims to give an overview of ZnO nanomaterials in biomedical applications.

TAKE HOME MESSAGE

Through a better understanding of the mechanisms of action and cellular consequences resulting from nanoparticles interactions with cells, the inherent toxicity and selectivity of ZnO nanoparticles against cancer may be improved further to make them attractive new anticancer agents.

Intracellular nanoparticle coating stability determines nanoparticle diagnostics efficacy and cell functionality

Iron oxide nanoparticles (NPs) are frequently employed in biomedical research as magnetic resonance (MR) contrast agents where high intracellular levels are required to clearly depict signal alterations. To date, the toxicity and applicability of these particles have not been completely unraveled. Here, we show that endosomal localization of different iron oxide particles results in their degradation and in reduced MR contrast, the rate of which is governed mainly by the stability of the coating. The release of ferric iron generates reactive species, which greatly affect cell functionality. Lipid-coated NPs display the highest stability and furthermore exhibit intracellular clustering, which significantly enhances their MR properties and intracellular persistence. These findings are of considerable importance because, depending on the nature of the coating, particles can be rapidly degraded, thus completely annihilating their MR contrast to levels not detectable when compared to controls and greatly impeding cell functionality, thereby hindering their application in functional in vivo studies.

Antibody-conjugated gold-gold sulfide nanoparticles as multifunctional agents for imaging and therapy of breast cancer

The goal of this study was to develop near-infrared (NIR) resonant gold-gold sulfide nanoparticles (GGS-NPs) as dual contrast and therapeutic agents for cancer management via multiphoton microscopy followed by higher intensity photoablation. We demonstrate that GGS-NPs exposed to a pulsed, NIR laser exhibit two-photon induced photoluminescence that can be utilized to visualize cancerous cells in vitro. When conjugated with anti-HER2 antibodies, these nanoparticles specifically bind SK-BR-3 breast carcinoma cells that over-express the HER2 receptor, enabling the cells to be imaged via multiphoton microscopy with an incident laser power of 1 mW. Higher excitation power (50 mW) could be employed to induce thermal damage to the cancerous cells, producing extensive membrane blebbing within seconds leading to cell death. GGS-NPs are ideal multifunctional agents for cancer management because they offer the ability to pinpoint precise treatment sites and perform subsequent thermal ablation in a single setting.