Gold nanoparticle conjugates: recent advances toward clinical applications

Platinum-Decorated Gold Nanoparticles with Dual Functionalities for Ultrasensitive Colorimetric in Vitro Diagnostics

Au nanoparticles (AuNPs) as signal reporters have been utilized in colorimetric in vitro diagnostics (IVDs) for decades. Nevertheless, it remains a grand challenge to substantially enhance the detection sensitivity of AuNP-based IVDs as confined by the inherent plasmonics of AuNPs. In this work, we circumvent this confinement by developing unique dual-functional AuNPs that were engineered by coating conventional AuNPs with ultrathin Pt skins of sub-10 atomic layers (i.e., Au@Pt NPs). The Au@Pt NPs retain the plasmonic activity of initial AuNPs while possessing ultrahigh catalytic activity enabled by Pt skins. Such dual functionalities, plasmonics and catalysis, offer two different detection alternatives: one produced just by the color from plasmonics (low-sensitivity mode) and the second more sensitive color catalyzed from chromogenic substrates (high-sensitivity mode), achieving an "on-demand" tuning of the detection performance. Using lateral flow assay as a model IVD platform and conventional AuNPs as a benchmark, we demonstrate that the Au@Pt NPs could enhance detection sensitivity by 2 orders of magnitude.

Therapeutic potential of carbohydrates as regulators of macrophage activation

It is well established for a broad range of disease states, including cancer and Mycobacterium tuberculosis infection, that pathogenesis is bolstered by polarisation of macrophages towards an anti-inflammatory phenotype, known as M2. As these innate immune cells are relatively long-lived, their re-polarisation to pro-inflammatory, phagocytic and bactericidal "classically activated" M1 macrophages is an attractive therapeutic approach. On the other hand, there are scenarios where the resolving inflammation, wound healing and tissue remodelling properties of M2 macrophages are beneficial - for example the successful introduction of biomedical implants. Although there are numerous endogenous and exogenous factors that have an impact on the macrophage polarisation spectrum, this review will focus specifically on prominent macrophage-modulating carbohydrate motifs with a view towards highlighting structure-function relationships and therapeutic potential.

Polymeric and Lipid Membranes-From Spheres to Flat Membranes and vice versa

Membranes are important components in a number of systems, where separation and control of the flow of molecules is desirable. Controllable membranes represent an even more coveted and desirable entity and their development is considered to be the next step of development. Typically, membranes are considered on flat surfaces, but spherical capsules possess a perfect "infinite" or fully suspended membranes. Similarities and transitions between spherical and flat membranes are discussed, while applications of membranes are also emphasized.

Applications of Gold Nanoparticles in Nanomedicine: Recent Advances in Vaccines

Nowadays, gold is used in (nano-)medicine, usually in the form of nanoparticles, due to the solid proofs given of its therapeutic effects on several diseases. Gold also plays an important role in the vaccine field as an adjuvant and a carrier, reducing toxicity, enhancing immunogenic activity, and providing stability in storage. An even brighter golden future is expected for gold applications in this area.

Green synthesis of gold nanoparticles using brown algae Cystoseira baccata: Its activity in colon cancer cells

This study is the first dealt with the use of brown macroalgae Cystoseira baccata (CB) extracts in obtaining gold nanoparticles (Au@CB) through an eco-friendly, fast, one-pot synthetic route. The formation of spherical, stable, polycrystalline nanoparticles with mean diameter of 8.4±2.2nm was demonstrated by UV-vis spectroscopy, TEM, HRTEM, STEM and zeta potential measurements. The extract appears to act as a protective agent where the particles are embedded, keeping them separated, avoiding aggregation and coalescence. The EELS and EDS analyses confirmed the elemental composition of the extract and nanoparticles. Moreover, the functional group of biomolecules present in CB and Au@CB were characterized by FTIR. The effects of CB extract and Au@CB were tested in vitro on the colon cancer cell lines HT-29 and Caco-2, as well as on normal primary neonatal dermal fibroblast cell line PCS-201-010. Results show a stronger cytotoxic effect against HT-29 than that on Caco-2; interestingly, a lack of toxicity on PCS-201-010 was obtained. Finally, the apoptotic activity was determined; Au@CB is able to induce apoptosis activation by the extrinsic and mitochondrial pathway in our CRC in vitro model. These encouraging results suggest that Au@CB has a significant potential for the treatment of colon rectal cancer.

Nanotechnology in Glycomics: Applications in Diagnostics, Therapy, Imaging, and Separation Processes

This review comprehensively covers the most recent achievements (from 2013) in the successful integration of nanomaterials in the field of glycomics. The first part of the paper addresses the beneficial properties of nanomaterials for the construction of biosensors, bioanalytical devices, and protocols for the detection of various analytes, including viruses and whole cells, together with their key characteristics. The second part of the review focuses on the application of nanomaterials integrated with glycans for various biomedical applications, that is, vaccines against viral and bacterial infections and cancer cells, as therapeutic agents, for in vivo imaging and nuclear magnetic resonance imaging, and for selective drug delivery. The final part of the review describes various ways in which glycan enrichment can be effectively done using nanomaterials, molecularly imprinted polymers with polymer thickness controlled at the nanoscale, with a subsequent analysis of glycans by mass spectrometry. A short section describing an active glycoprofiling by microengines (microrockets) is covered as well.

Polyethylenimine-mediated synthetic insertion of gold nanoparticles into mesoporous silica nanoparticles for drug loading and biocatalysis

Mesoporous silica nanoparticles (MSNPs) have been used as an efficient and safe carrier for drug delivery and biocatalysis. The surface modification of MSNPs using suitable reagents may provide a robust framework in which two or more components can be incorporated to give multifunctional capabilities (e.g., synthesis of noble metal nanoparticles within mesoporous architecture along with loading of a bioactive molecule). In this study, the authors reported on a new synthetic route for the synthesis of gold nanoparticles (AuNPs) within (1) unmodified MSNPs and (2) 3-trihydroxysilylpropyl methylphosphonate-modified MSNPs. A cationic polymer, polyethylenimine (PEI), and formaldehyde were used to mediate synthetic incorporation of AuNPs within MSNPs. The AuNPs incorporated within the mesoporous matrix were characterized by transmission electron microscopy, energy dispersive x-ray analysis, and high-resolution scanning electron microscopy. PEI in the presence of formaldehyde enabled synthetic incorporation of AuNPs in both unmodified and modified MSNPs. The use of unmodified MSNPs was associated with an increase in the polycrystalline structure of the AuNPs within the MSNPs. The AuNPs within modified MSNPs showed better catalytic activity than those within unmodified MSNPs. MSNPs with an average size of 200 nm and with a pore size of 4-6 nm were used for synthetic insertion of AuNPs. It was found that the PEI coating enabled AuNPs synthesis within the mesopores in the presence of formaldehyde or tetrahydrofuran hydroperoxide at a temperature between 10 and 25 °C or at 60 °C in the absence of organic reducing agents. The as-made AuNP-inserted MSNPs exhibited enhanced catalytic activity. For example, these materials enabled rapid catalytic oxidation of the o-dianisidine substrate to produce a colored solution in proportion to the amount of H₂O₂ generated as a function of glucose oxidase-catalyzed oxidation of glucose; a linear concentration range from 80 to 800 μM and a detection limit as low as 80 μM were observed. The mesoscale pores of the as developed AuNP-inserted MSNPs were also used to entrap the hydrophobic drug paclitaxel. The results of this study indicate the potential use of the AuNP-inserted MSNPs in biocatalysis and drug delivery.

Immunological properties of gold nanoparticles

In the past decade, gold nanoparticles have attracted strong interest from the nanobiotechnological community owing to the significant progress made in robust and easy-to-make synthesis technologies, in surface functionalization, and in promising biomedical applications. These include bioimaging, gene diagnostics, analytical sensing, photothermal treatment of tumors, and targeted delivery of various biomolecular and chemical cargos. For the last-named application, gold nanoparticles should be properly fabricated to deliver the cargo into the targeted cells through effective endocytosis. In this review, we discuss recent progress in understanding the selective penetration of gold nanoparticles into immune cells. The interaction of gold nanoparticles with immune cell receptors is discussed. As distinct from other published reviews, we present a summary of the immunological properties of gold nanoparticles. This review also summarizes what is known about the application of gold nanoparticles as an antigen carrier and adjuvant in immunization for the preparation of antibodies in vivo. For each of the above topics, the basic principles, recent advances, and current challenges are discussed. Thus, this review presents a detailed analysis of data on interaction of gold nanoparticles with immune cells. Emphasis is placed on the systematization of data over production of antibodies by using gold nanoparticles and adjuvant properties of gold nanoparticles. Specifically, we start our discussion with current data on interaction of various gold nanoparticles with immune cells. The next section describes existing technologies to improve production of antibodies in vivo by using gold nanoparticles conjugated with specific ligands. Finally, we describe what is known about adjuvant properties of bare gold or functionalized nanoparticles. In the Conclusion section, we present a short summary of reported data and some challenges and perspectives.

Targeted dose enhancement in radiotherapy for breast cancer using gold nanoparticles, part 2: A treatment planning study

PURPOSE

In recent years, there has been growing interest in the use of gold nanoparticles (GNPs) combined with radiotherapy to improve tumor control. However, the complex interplay between GNP uptake and dose distribution in realistic clinical treatment are still somewhat unknown.

METHODS

The effects of different concentrations of 2 nm diameter GNP, ranging from 0 to 5×105 nanoparticles per tumoral cell, were theoretically investigated. A parametrization of the GNP distribution outside the target was carried out using a Gaussian standard deviation σ, from a zero value, relative to a selective concentration of GNPs inside the tumor volume alone, to 50mm, when GNPs are spatially distributed also in the healthy tissues surrounding the tumor. Treatment simulations of five patients with breast cancer were performed with 6 and 15 MV photons assuming a partial breast irradiation. A closed analytical reformulation of the Local Effect Model coupled with the estimation of local dose deposited around a GNP was validated using an in vitro study for MDA-MB-231 tumoral cells. The expected treatment outcome was quantified in terms of tumor control probability (TCP) and normal tissue complication probability (NTCP) as a function of the spatially varying gold uptake.

RESULTS

Breast cancer treatment planning simulations show improved treatment outcomes when GNPs are selectively concentrated in the tumor volume (i.e., σ = 0 mm). In particular, the TCP increases up to 18% for 5×105 nanoparticles per cell in the tumor region depending on the treatment schedules, whereas an improvement of the therapeutic index is observed only for concentrations of about 105 GNPs per tumoral cell and limited spatial distribution in the normal tissue.

CONCLUSIONS

The model provides a useful framework to estimate the nanoparticle-driven radiosensitivity in breast cancer treatment irradiation, accounting for the complex interplay between dose and GNP uptake distributions.

Gold Nanoparticles: Recent Advances in the Biomedical Applications

Among the multiple branches of nanotechnology applications in the area of medicine and biology, Nanoparticle technology is the fastest growing and shows significant future promise. Nanoscale structures, with size similar to many biological molecules, show different physical and chemical properties compared to either small molecules or bulk materials, find many applications in the fields of biomedical imaging and therapy. Gold nanoparticles (AuNPs) are relatively inert in biological environment, and have a number of physical properties that are suitable for several biomedical applications. For example, AuNPs have been successfully employed in inducing localized hyperthermia for the destruction of tumors or radiotherapy for cancer, photodynamic therapy, computed tomography imaging, as drug carriers to tumors, bio-labeling through single particle detection by electron microscopy and in photothermal microscopy. Recent advances in synthetic chemistry makes it possible to make gold nanoparticles with precise control over physicochemical and optical properties that are desired for specific clinical or biological applications. Because of the availability of several methods for easy modification of the surface of gold nanoparticles for attaching a ligand, drug or other targeting molecules, AuNPs are useful in a wide variety of applications. Even though gold is biologically inert and thus shows much less toxicity, the relatively low rate of clearance from circulation and tissues can lead to health problems and therefore, specific targeting of diseased cells and tissues must be achieved before AuNPs find their application for routine human use.

Gold nanoparticles for applications in cancer radiotherapy: Mechanisms and recent advancements

Gold nanoparticles (AuNPs) have emerged as novel radiosensitizers owing to their high X-ray absorption, synthetic versatility, and unique chemical, electronic and optical properties. Multi-disciplinary research performed over the past decade has demonstrated the potential of AuNP-based radiosensitizers, and identified possible mechanisms underlying the observed radiation enhancement effects of AuNPs. Despite promising findings from pre-clinical studies, the benefits of AuNP radiosensitization have yet to successfully translate into clinical practice. In this review, we present an overview of the current state of AuNP-based radiosensitization in the context of the physical, chemical and biological modes of radiosensitization. As well, recent advancements that focus on formulation design and enable multi-modality treatment and clinical utilization are discussed, concluding with design considerations to guide the development of next generation AuNPs for clinical applications.

Towards enhanced optical sensor performance: SEIRA and SERS with plasmonic nanostars

We report the development of plasmonic chip-based systems comprising self-assembled gold nanostars at silicon substrates that enable concomitantly enhanced Raman (surface enhanced Raman spectroscopy; SERS) and mid-infrared (surface enhanced infrared reflection or absorption spectroscopy; SEIRA) spectral signatures.

Nanostructured materials for photodynamic therapy: synthesis, characterization and in vitro activity

The influence of size and shape on the photodynamic properties of three gold-based porphyrin-loaded vehicles: spherical nanoparticles, hexahedral microparticles and cylindrical nanorods.

Enhancing radiotherapy for lung cancer using immunoadjuvants delivered in situ from new design radiotherapy biomaterials: a preclinical study

Studies show that radiotherapy of a primary tumor in combination with immunoadjuvants (IA) can result in increased survival or immune-mediated regression of metastasis outside the radiation field, a phenomenon known as abscopal effect. However, toxicities due to repeated systematic administration of IA have been shown to be a major obstacle in clinical trials. To minimize the toxicities and prime a more potent immune response, Ngwa et al have proposed that inert radiotherapy biomaterials such as fiducials could be upgraded to multifunctional ones loaded with IA for in situ delivery directly into the tumor sub-volume at no additional inconvenience to patients. In this preliminary study, the potential of such an approach is investigated for lung cancer using anti-CD40 antibody. First the benefit of using the anti-CD40 delivered in situ to enhance radiotherapy was tested in mice with subcutaneous tumors generated with the Lewis Lung cancer cell line LL/2 (LLC-1). The tumors were implanted on both flanks of the mice to simulate metastasis. Tumors on one flank were treated with and without anti-CD40 and the survival benefits compared. An experimentally determined in vivo diffusion coefficient for nanoparticles was then employed to estimate the time for achieving intratumoral distribution of the needed minimal concentrations of anti-CD40 nanoparticles if released from a multifuntional radiotherapy biomaterials. The studies show that the use of anti-CD40 significantly enhanced radiotherapy effect, slowing the growth of the treated and untreated tumors, and increasing survival. Meanwhile our calculations indicate that for a 2-4 cm tumor and 7 mg g^-1 IA concentrations, it would take 4.4-17.4 d, respectively, following burst release, for the required concentration of IA nanoparticles to accumulate throughout the tumor during image-guided radiotherapy. The distribution of IA could be customized as a function of loading concentrations or nanoparticle size to fit current Stereotactic Body Radiotherapy schedules. Overall, the preliminary results support ongoing work in developing multifunctional radiotherapy biomaterials for in situ delivery of immunoadjuvants such as anti-CD40 to leverage the abscopal effect, while minimizing systemic toxicities. The potential of extending such an approach to other cancer types is discussed.

Vaccine technologies: From whole organisms to rationally designed protein assemblies

Vaccines have been the single most significant advancement in public health, preventing morbidity and mortality in millions of people annually. Vaccine development has traditionally focused on whole organism vaccines, either live attenuated or inactivated vaccines. While successful for many different infectious diseases whole organisms are expensive to produce, require culture of the infectious agent, and have the potential to cause vaccine associated disease in hosts. With advancing technology and a desire to develop safe, cost effective vaccine candidates, the field began to focus on the development of recombinantly expressed antigens known as subunit vaccines. While more tolerable, subunit vaccines tend to be less immunogenic. Attempts have been made to increase immunogenicity with the addition of adjuvants, either immunostimulatory molecules or an antigen delivery system that increases immune responses to vaccines. An area of extreme interest has been the application of nanotechnology to vaccine development, which allows for antigens to be expressed on a particulate delivery system. One of the most exciting examples of nanovaccines are rationally designed protein nanoparticles. These nanoparticles use some of the basic tenants of structural biology, biophysical chemistry, and vaccinology to develop protective, safe, and easily manufactured vaccines. Rationally developed nanoparticle vaccines are one of the most promising candidates for the future of vaccine development.

EGF-coated gold nanoparticles provide an efficient nano-scale delivery system for the molecular radiotherapy of EGFR-positive cancer

Purpose Radiolabeled antibodies and peptides hold promise for molecular radiotherapy but are often limited by a low payload resulting in inadequate delivery of radioactivity to tumour tissue and, therefore, modest therapeutic effect. We developed a facile synthetic method of radiolabeling indium-111 (111In) to epidermal growth factor (EGF)-gold nanoparticles (111In-EGF-Au NP) with a high payload. Materials and methods EGF-Au NP were prepared via an interaction between gold and the disulphide bonds of EGF and radiolabeled using 111InCl3. Targeting efficiency was investigated by quantitating internalized radioactivity and by confocal imaging following exposure of MDA-MB-468 (1.3 × 106 EGFR/cell) and MCF-7 (104 EGFR/cell) cells to Cy3-EGF-Au NP. Cytotoxicity was evaluated in clonogenic assays. Results The proportion of total administered radioactivity that was internalized by MDA-MB-468 and MCF-7 cells was 15% and 1.3%, respectively (mixing ratio of EGF:Au of 160). This differential uptake in the two cell lines was confirmed using confocal microscopy. 111In-EGF-Au NP were significantly more radiotoxic to MDA-MB-468 than MCF-7 cells with a surviving fraction of 17.1 ± 4.4% versus 89.8 ± 1.4% (p < 0.001) after exposure for 4 h. Conclusions An 111In-labeled EGF-Au nanosystem was developed. It enabled targeted delivery of a high 111In payload specifically to EGFR-positive cancer cells leading to radiotoxicity that can be exploited for molecularly targeted radiotherapy.

Biocorona Bound Gold Nanoparticles Augment Their Hematocompatibility Irrespective of Size or Surface Charge

Despite colloidal gold nanoparticles (AuNP) being proposed for a multitude of biomedical applications, there is a lack of understanding on how the protein corona (PC) formation over AuNP influences its interaction with blood components. Herein, 40 and 80 nm AuNP with branched polyethylenimine, lipoic acid, and polyethylene glycol surface coatings were exposed to human plasma, and time-dependent evolution of the PC was evaluated using differential centrifugation sedimentation. Further, the impact of PC-AuNP interaction with human blood components was studied by evaluating red blood cell (RBC) aggregation, hemolysis, platelet activation and aggregation, prothrombin time, activated partial thromboplastin time, complement activation and cytokine release. In contrast to bare AuNP, PC-coated AuNP exhibited enhanced compatibility with RBC, platelets, and lymphocytes. More importantly, PC-AuNP did not activate the platelet coagulation cascade or complement system or elicit an immune response up to a relatively higher dose of 100 μg/mL. This study suggests that, irrespective of the physicochemical properties, the adsorption of the PC over AuNP significantly influences its biological impact by alleviating adverse hematotoxicity of bare NP.

Glyco-gold nanoparticle shapes enhance carbohydrate-protein interactions in mammalian cells

Advances in shape-dependent nanoparticle (NP) research have prompted a close scrutiny of the behaviour of nanostructures in vitro and in vivo. Data pertaining to cellular uptake and site specific sequestration of different shapes of NPs will undoubtedly assist researchers to design better nano-probes for therapeutic and imaging purposes. Herein, we investigated the shape dependent uptake of glyco-gold nanoparticles (G-AuNPs) in different cancer cell lines. Specifically, we have compared the behaviour of spherical, rod and star AuNPs with mannose and galactose conjugations. In vitro experiments showed that the rod-AuNPs exhibited the highest uptake over that of the star and spherical counterparts. Further, an investigation of the mechanism of the uptake clearly demonstrated clathrin mediated endocytosis of the specific G-AuNPs. These results reveal the benefits of different G-AuNP shapes in carbohydrate-mediated interactions.

Nanoparticles and DNA - a powerful and growing functional combination in bionanotechnology

Functionally integrating DNA and other nucleic acids with nanoparticles in all their different physicochemical forms has produced a rich variety of composite nanomaterials which, in many cases, display unique or augmented properties due to the synergistic activity of both components. These capabilities, in turn, are attracting greater attention from various research communities in search of new nanoscale tools for diverse applications that include (bio)sensing, labeling, targeted imaging, cellular delivery, diagnostics, therapeutics, theranostics, bioelectronics, and biocomputing to name just a few amongst many others. Here, we review this vibrant and growing research area from the perspective of the materials themselves and their unique capabilities. Inorganic nanocrystals such as quantum dots or those made from gold or other (noble) metals along with metal oxides and carbon allotropes are desired as participants in these hybrid materials since they can provide distinctive optical, physical, magnetic, and electrochemical properties. Beyond this, synthetic polymer-based and proteinaceous or viral nanoparticulate materials are also useful in the same role since they can provide a predefined and biocompatible cargo-carrying and targeting capability. The DNA component typically provides sequence-based addressability for probes along with, more recently, unique architectural properties that directly originate from the burgeoning structural DNA field. Additionally, DNA aptamers can also provide specific recognition capabilities against many diverse non-nucleic acid targets across a range of size scales from ions to full protein and cells. In addition to appending DNA to inorganic or polymeric nanoparticles, purely DNA-based nanoparticles have recently surfaced as an excellent assembly platform and have started finding application in areas like sensing, imaging and immunotherapy. We focus on selected and representative nanoparticle-DNA materials and highlight their myriad applications using examples from the literature. Overall, it is clear that this unique functional combination of nanomaterials has far more to offer than what we have seen to date and as new capabilities for each of these materials are developed, so, too, will new applications emerge.

Controlled synthesis of polyethylenimine coated gold nanoparticles: Application in glutathione sensing and nucleotide delivery

Synthesis of functional gold nanoparticles (AuNPs) justifying selectivity in biochemical interaction along with biocompatibility suited for in vivo biomedical applications has been a challenging issue. We report herein the role of polyethylenimine (PEI) in controlled synthesis of AuNPs under ambient conditions which has potentiality for sensing glutathione and selective interaction with DNA binding proteins facilitating endosomal escape for the nucleotide delivery. The choice of organic reducing agents like formaldehyde/acetaldehyde/acetyl acetone/tetrahydrofuran hydroperoxide and other similar compounds allow rapid conversion of PEI capped gold cations into AuNPs at room temperature thus controlling the functional ability of nanoparticles as a function of organic reducing agents. Both small and higher molecular weight PEI facilitates fast synthesis of AuNPs controlling cytotoxicity during in vivo biomedical applications. The AuNPs have been characterized by UV-Vis and transmission electron microscopy revealing excellent polycrystallinity and controlled nanogeometry. The cationic polymer coating enhances the electrocatalytic performances of nanoparticles. The typical biomedical application on glutathione (GSH) sensing based on peroxidase mimetic ability of as made AuNPs is studied. The as synthesized AuNPs are extreme salt and pH resistant and have potentiality for both homogeneous and heterogeneous biocatalysis. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1191-1199, 2017.

Gold nanoparticles coated with a polydopamine layer and dextran brush surface for diagnosis and highly efficient photothermal therapy of tumors

The nanoparticles improved tumor CT imaging and cured tumors after injection of the nanoparticles followed by NIR laser irradiation.

Hybrid nanoparticles for combination therapy of cancer

Nanoparticle anticancer drug delivery enhances therapeutic efficacies and reduces side effects by improving pharmacokinetics and biodistributions of the drug payloads in animal models. Despite promising preclinical efficacy results, monotherapy nanomedicines have failed to produce enhanced response rates over conventional chemotherapy in human clinical trials. The discrepancy between preclinical data and clinical outcomes is believed to result from the less pronounced enhanced permeability and retention (EPR) effect in and the heterogeneity of human tumors as well as the intrinsic/acquired drug resistance to monotherapy over the treatment course. To address these issues, recent efforts have been devoted to developing nanocarriers that can efficiently deliver multiple therapeutics with controlled release properties and increased tumor deposition. In ideal scenarios, the drug or therapeutic modality combinations have different mechanisms of action to afford synergistic effects. In this review, we summarize recent progress in designing hybrid nanoparticles for the co-delivery of combination therapies, including multiple chemotherapeutics, chemotherapeutics and biologics, chemotherapeutics and photodynamic therapy, and chemotherapeutics and radiotherapy. The in vitro and in vivo anticancer effects are also discussed.

Gold Nanotheranostics: Proof-of-Concept or Clinical Tool?

Nanoparticles have been making their way in biomedical applications and personalized medicine, allowing for the coupling of diagnostics and therapeutics into a single nanomaterial—nanotheranostics. Gold nanoparticles, in particular, have unique features that make them excellent nanomaterials for theranostics, enabling the integration of targeting, imaging and therapeutics in a single platform, with proven applicability in the management of heterogeneous diseases, such as cancer. In this review, we focus on gold nanoparticle-based theranostics at the lab bench, through pre-clinical and clinical stages. With few products facing clinical trials, much remains to be done to effectively assess the real benefits of nanotheranostics at the clinical level. Hence, we also discuss the efforts currently being made to translate nanotheranostics into the market, as well as their commercial impact.

In-vitro Optimization of Nanoparticle-Cell Labeling Protocols for In-vivo Cell Tracking Applications

Recent advances in theranostic nanomedicine can promote stem cell and immune cell-based therapy. Gold nanoparticles (GNPs) have been shown to be promising agents for in-vivo cell-tracking in cell-based therapy applications. Yet a crucial challenge is to develop a reliable protocol for cell upload with, on the one hand, sufficient nanoparticles to achieve maximum visibility of cells, while on the other hand, assuring minimal effect of particles on cell function and viability. Previous studies have demonstrated that the physicochemical parameters of GNPs have a critical impact on their efficient uptake by cells. In the current study we have examined possible variations in GNP uptake, resulting from different incubation period and concentrations in different cell-lines. We have found that GNPs effectively labeled three different cell-lines - stem, immune and cancer cells, with minimal impairment to cell viability and functionality. We further found that uptake efficiency of GNPs into cells stabilized after a short period of time, while GNP concentration had a significant impact on cellular uptake, revealing cell-dependent differences. Our results suggest that while heeding the slight variations within cell lines, modifying the loading time and concentration of GNPs, can promote cell visibility in various nanoparticle-dependent in-vivo cell tracking and imaging applications.

Cytotoxicity of various types of gold-mesoporous silica nanoparticles in human breast cancer cells

Recently, gold nanoparticles (AuNPs) have shown promising biological applications due to their unique electronic and optical properties. However, the potential toxicity of AuNPs remains a major hurdle that impedes their use in clinical settings. Mesoporous silica is very suitable for the use as a coating material for AuNPs and might not only reduce the cytotoxicity of cetyltrimethylammonium bromide-coated AuNPs but might also facilitate the loading and delivery of drugs. Herein, three types of rod-like gold-mesoporous silica nanoparticles (termed bare AuNPs, core-shell Au@mSiO2NPs, and Janus Au@mSiO2NPs) were specially designed, and the effects of these AuNPs on cellular uptake, toxic behavior, and mechanism were then systematically studied. Our results indicate that bare AuNPs exerted higher toxicity than the Au@mSiO2NPs and that Janus Au@mSiO2NPs exhibited the lowest toxicity in human breast cancer MCF-7 cells, consistent with the endocytosis capacity of the nanoparticles, which followed the order, bare AuNPs > core-shell Au@mSiO2NPs > Janus Au@mSiO2NPs. More importantly, the AuNPs-induced apoptosis of MCF-7 cells exhibited features that were characteristic of intracellular reactive oxygen species (ROS) generation, activation of c-Jun-N-terminal kinase (JNK) phosphorylation, an enhanced Bax-to-Bcl-2 ratio, and loss of the mitochondrial membrane potential. Simultaneously, cytochrome c was released from mitochondria, and the caspase-3/9 cascade was activated. Moreover, both ROS scavenger (N-acetylcysteine) and JNK inhibitor (SP600125) partly blocked the induction of apoptosis in all AuNPs-treated cells. Taken together, these findings suggest that all AuNPs induce apoptosis through the ROS-/JNK-mediated mitochondrial pathway. Thus, Janus Au@mSiO2NPs exhibit the potential for applications in biomedicine, thus aiding the clinical translation of AuNPs.

Determination of biodistribution of ultrasmall, near-infrared emitting gold nanoparticles by photoacoustic and fluorescence imaging

This study compares fluorescence and photoacoustic (PA) imaging of ex vivo tumors and organs from tumor-bearing mice injected intravenously with ultrasmall (<3  nm ) tiopronin-capped Au nanoparticles and compares the data with inductively coupled plasma mass spectrometry (ICP-MS). Good agreement is seen in particle distributions and concentrations at the organ level. The spatial resolution from the imaging techniques allows for localization of the particles within organ structures. Although the particles do not have a plasmon peak, their absorbance in the near-infrared (NIR) is sufficient for PA excitation. PA imaging shows an increase of signal as particle concentrations increase, with changes in spectrum if particles aggregate. Fluorescence imaging using the particles’ native NIR emission shows agreement in general intensity in each organ, though quenching of emission can be seen at very high concentrations. Both of these imaging techniques are noninvasive and labor-saving alternatives to organ digestion and ICP-MS and may provide insight into cellular distribution of particles. The simple construct avoids the use of toxic semiconductor materials or dyes, relying upon the gold itself for both the fluorescence and PA signal. This provides a useful alternative to more complex approaches to multimodal imaging and one that is readily translatable to the clinic.

Near-infrared light-responsive nanomaterials for cancer theranostics

Early diagnosis and effective cancer therapy are required, to properly treat cancer, which causes more than 8.2 million deaths in a year worldwide. Among various cancer treatments, nanoparticle-based cancer therapies and molecular imaging techniques have been widely exploited over the past decades to overcome current drawbacks of existing cancer treatments. In particular, gold nanoparticles (AuNPs), carbon nanotubes (CNTs), graphene oxide (GO), and upconversion nanocrystals (UNCs) have attracted tremendous attention from researchers due to their near-infrared (NIR) light-responsive behaviors. These nanomaterials are considered new multifunctional platforms for cancer theranostics. They would enable on-demand control of drug release or molecular imaging in response to a remote trigger by NIR light exposure. This approach allows the patient or physician to adjust therapy precisely to a target site, thus greatly improving the efficacy of cancer treatments, while reducing undesirable side effects. In this review, we have summarized the advantages of NIR light-responsive nanomaterials for in vivo cancer treatments, which includes NIR triggered photothermal therapy (PTT) and photodynamic therapy (PDT). Furthermore, recent developments, perspectives, and new challenges of NIR light-responsive nanomaterials are discussed for cancer theranostic applications.

Theranostic applications of carbon nanomaterials in cancer: Focus on imaging and cargo delivery

Carbon based nanomaterials have attracted significant attention over the past decades due to their unique physical properties, versatile functionalization chemistry, and biological compatibility. In this review, we will summarize the current state-of-the-art applications of carbon nanomaterials in cancer imaging and drug delivery/therapy. The carbon nanomaterials will be categorized into fullerenes, nanotubes, nanohorns, nanodiamonds, nanodots and graphene derivatives based on their morphologies. The chemical conjugation/functionalization strategies of each category will be introduced before focusing on their applications in cancer imaging (fluorescence/bioluminescence, magnetic resonance (MR), positron emission tomography (PET), single-photon emission computed tomography (SPECT), photoacoustic, Raman imaging, etc.) and cargo (chemo/gene/therapy) delivery. The advantages and limitations of each category and the potential clinical utilization of these carbon nanomaterials will be discussed. Multifunctional carbon nanoplatforms have the potential to serve as optimal candidates for image-guided delivery vectors for cancer.

Biomedical applications of gold nanomaterials: opportunities and challenges

In the past few years, there has been an unprecedented development of gold nanomaterials (AuNMs) for potential clinical applications. Owing to their advantageous physical, chemical, and biological properties, AuNMs have attracted great attention in the nanomedicine arena for applications in biological sensing, biomedical imaging, drug delivery, and photothermal therapy. Their tunable size, shape, and surface characteristics coupled with excellent biocompatibility render them ideal candidates for translation from bench-top to bedside. This review summarizes the recent research on the applications of AuNM with a focus on biomedical diagnostics and therapeutics. The bio-interaction of these NM with cells and their in vivo responses are presented. After reviewing these potential applications, future challenges and prospects are discussed and the suitability of how AuNMs are used as effective tools in clinical medicine is assessed.

Nanogold bioconjugates for direct and sensitive multiplexed immunosensing

The use of nanogold bioconjugates for direct detection of the antibody-antigen immunoreaction is addressed. The integration of gold nanoparticles tracers as signal generators in microarray immunosensing and compact disc detection technique show important advantages to reach sensitive, selective, high throughput, reliable and cost-effective assays. For that, a thorough study of the performances of the size of spherical nanogold particles and coating density was developed. The size of the nanoparticle determines the optimal antibody dilution, being the smaller particles the best performing ones. Enhancement effect of lower size is also studied. The gold labeling method do not affects the recognition capability of the labeled proteins. As a proof of concept, the nanoconjugates were used for the simultaneous and direct determination of small molecules. Employing nanogold bioconjugates as recognition labels resulted in robust and reliable assays, reaching a sensitivity of 0.03 and 1.3μg/L for sulfasalazine and atrazine, respectively. This shows that the use of nanogold bioconjugates for direct immunosensing is very competitive, achieving highly sensitive and reproducible assays (RSD<10%). This approach would simultaneously determine both small and large molecular size targets, in different formats, using the same detection mode what paves the way for many other applications in different scenarios.

Formation of lipid and polymer based gold nanohybrids using a nanoreactor approach

Nanocarriers encapsulating gold nanoparticles hold tremendous promise for biomedical applications. The nanoreactor approach offers a versatile, efficient, and highly reproducible preparation technology.

Nanoplasmonically-induced defects in lipid membrane monitored by ion current: transient nanopores versus membrane rupture

We have developed a nanoplasmonic-based approach to induce nanometer-sized local defects in the phospholipid membranes. Here, gold nanorods and nanoparticles having plasmon resonances in the near-infrared (NIR) spectral range are used as optical absorption centers in the lipid membrane. Defects optically induced by NIR-laser irradiation of gold nanoparticles are continuously monitored by high-precision ion conductance measurement. Localized laser-mediated heating of nanorods and nanoparticle aggregates cause either (a) transient nanopores in lipid membranes or (b) irreversible rupture of the membrane. To monitor transient opening and closing, an electrophysiological setup is assembled wherein a giant liposome is spread over a micrometer hole in a glass slide forming a single bilayer of high Ohmic resistance (so-called gigaseal), while laser light is coupled in and focused on the membrane. The energy associated with the localized heating is discussed and compared with typical elastic parameters in the lipid membranes. The method presented here provides a novel methodology for better understanding of transport across artificial or natural biological membranes.