Parvesh Sharma

Nanoparticles as contrast agents for in-vivo bioimaging: current status and future perspectives

Nanoparticle-based contrast agents are quickly becoming valuable and potentially transformative tools for enhancing medical diagnostics for a wide range of in-vivo imaging modalities. Compared with conventional molecular-scale contrast agents, nanoparticles (NPs) promise improved abilities for in-vivo detection and potentially enhanced targeting efficiencies through longer engineered circulation times, designed clearance pathways, and multimeric binding capacities. However, NP contrast agents are not without issues. Difficulties in minimizing batch-to-batch variations and problems with identifying and characterizing key physicochemical properties that define the in-vivo fate and transport of NPs are significant barriers to the introduction of new NP materials as clinical contrast agents. This manuscript reviews the development and application of nanoparticles and their future potential to advance current and emerging clinical bioimaging techniques. A focus is placed on the application of solid, phase-separated materials, for example metals and metal oxides, and their specific application as contrast agents for in-vivo near-infrared fluorescence (NIRF) imaging, magnetic resonance imaging (MRI), positron emission tomography (PET), computed tomography (CT), ultrasound (US), and photoacoustic imaging (PAI). Clinical and preclinical applications of NPs are identified for a broad spectrum of imaging applications, with commentaries on the future promise of these materials. Emerging technologies, for example multifunctional and theranostic NPs, and their potential for clinical advances are also discussed.

Gold nanoparticles as a contrast agent for in vivo tumor imaging with photoacoustic tomography

Photoacoustic tomography (PAT) is a rapidly emerging non-invasive imaging technology that integrates the merits of high optical contrast with high ultrasound resolution. The ability to quantitatively and non-invasively image nanoparticles has important implications for the development of nanoparticles as in vivo cancer diagnostic and therapeutic agents. In this study, the ability of systemically administered poly(ethylene glycol)-coated (PEGylated) gold nanoparticles as a contrast agent for in vivo tumor imaging with PAT has been evaluated. We demonstrate that gold nanoparticles (20 and 50 nm) have high photoacoustic contrast as compared to mouse tissue ex vivo. Gold nanoparticles can be visualized in mice in vivo following subcutaneous administration using PAT. Following intravenous administration of PEGylated gold nanoparticles to tumor-bearing mice, accumulation of gold nanoparticles in tumors can be effectively imaged with PAT. With gold nanoparticles as a contrast agent, PAT has important potential applications in the image guided therapy of superficial tumors such as breast cancer, melanoma and Merkel cell carcinoma.

Gold-Speckled Multimodal Nanoparticles for Noninvasive Bioimaging

In this report the synthesis, characterization, and functional evaluation of a multimodal nanoparticulate contrast agent for noninvasive imaging through both magnetic resonance imaging (MRI) and photoacoustic tomography (PAT) is presented. The nanoparticles described herein enable high resolution and highly sensitive three-dimensional diagnostic imaging through the synergistic coupling of MRI and PAT capabilities. Gadolinium (Gd)-doped gold-speckled silica (GSS) nanoparticles, ranging from 50 to 200 nm, have been prepared in a simple one-pot synthesis using nonionic microemulsions. The photoacoustic signal is generated from a nonuniform, discontinuous gold nanodomains speckled across the silica surface, whereas the MR contrast is provided through Gd incorporated in the silica matrix. The presence of a discontinuous speckled surface, as opposed to a continuous gold shell, allows sufficient bulk water exchange with the Gd ions to generate a strong MR contrast. The dual imaging capabilities of the particles have been demonstrated through in silicio and in vitro methods. The described particles also have the capacity for therapeutic applications including the thermal ablation of tumors through the absorption of irradiated light.

Polyhydroxy fullerenes for non-invasive cancer imaging and therapy.

DOI: 10.1002/smll.201000847 Nanoparticle-mediated, image-guided cancer therapy has tremendous promise for increasing the effi cacy of cancer treatment while reducing toxic side effects traditionally associated with treatment. Carbon nanotubes and metal-based nanomaterials are leading candidates for image-guided therapy in cancer nanotechnology. [ 1–5 ] However, limited solvent compatibility, non-biodegradability and concerns over the safety of these nanomaterials may hinder their commercialization. Here, we show that the photothermal and photoacoustic properties of polyhydroxy fullerenes [ 6 ] (PHF)—which are water-soluble, biodegradable, [ 7 ] antioxidant, [ 8–10 ] and rapidly excreted [ 11 ] —can be applied for imaging and therapy of cancer. Biodegradable PHF-containing chitosan nanoparticles provided excellent photoacoustic contrast. Tumors injected with PHF nanoparticles and exposed to near infrared laser decreased in cross-sectional area by an average of 32% within two hours of treatment, with only a blister visible 20 hours post-treatment. We anticipate that photoacoustic and photothermal properties of PHF along with their other therapeutic properties [ 12–15 ] will enable safe, non-invasive image-guided therapy of cancer with minimal side-effects. Polyhydroxy Fullerenes for Non-Invasive Cancer Imaging and Therapy

Influence of shape, adhesion and simulated lung mechanics on amorphous silica nanoparticle toxicity

Prevailing theories suggest that acicular, or fiber-like, particles induce enhanced toxicity over isotropic material through hindrance of phagocyte-mediated clearance mechanisms and through the aggravation of proximal cells via mechanical interactions. Currently, the degree to which either of these mechanisms operates is not well understood. To gain a more fundamental understanding of acicular particle toxicity, we have synthesized submicron and nanoscale amorphous silica spheres and rods as model materials for shape-driven toxicological experimentation. To accentuate contributions from mechanical damage in vitro, exposure studies were performed in the presence and absence of simulated lung mechanics. To promote and mitigate cell–particle contact-mediated mechanical interactions, the adhesion of the particles to the cell membrane was respectively modified by the physisorption of fibronectin and chemisorption of the polyethylene glycol to the silica particle surface. Lactic acid dehydrogense (LDH) and interleukin (IL)-8 release were used as endpoints for cytotoxicity and inflammation, respectively. The results indicate that particle exposures in the presence of physiological stretch induce increased LDH release and IL-8 expression regardless of shape. Moreover, it is evident that shape-induced aggregation may play a significant role in mitigating particle clearance pathways.

Gadolinium‐Doped Silica Nanoparticles Encapsulating Indocyanine Green for Near Infrared and Magnetic Resonance Imaging

Clinical applications of the indocyanine green (ICG) dye, the only near infrared (NIR) imaging dye approved by the Food and Drug Administration (FDA) in the USA, are limited due to rapid protein binding, fast clearance, and instability in physiologically relevant conditions. Encapsulating ICG in silica particles can enhance its photostability, minimize photobleaching, increase the signal-to-noise (S/N) ratio and enable in vivo studies. Furthermore, a combined magnetic resonance (MR) and NIR imaging particulate can integrate the advantage of high-resolution 3D anatomical imaging with high-sensitivity deep-tissue in-vivo fluorescent imaging. In this report, a novel synthesis technique that can achieve these goals is presented. A reverse-microemulsion-based synthesis protocol is employed to produce 25 nm ICG-doped silica nanoparticles (NPs). The encapsulation of ICG is achieved by manipulating coulombic attractions with bivalent ions and aminated silanes and carrying out silica synthesis in salt-catalyzed, mildly basic pH conditions using dioctyl sulfosuccinate (AOT)/heptane/water microemulsion system. Furthermore, paramagnetic properties are imparted by chelating paramagnetic Gd to the ICG-doped silica NPs. Aqueous ICG-dye-doped silica NPs show increased photostability (over a week) and minimal photobleaching as compared to the dye alone. The MR and optical imaging capabilities of these particles are demonstrated through phantom, in vitro and in vivo experiments. The described particles have the potential to act as theranostic agents by combining photodynamic therapy through the absorption of NIR irradiated light.

A nanoceria–platinum–graphene nanocomposite for electrochemical biosensing

Most graphene-metal nanocomposites for biosensing are formed using noble metals. Recently, development of nanocomposites using rare earth metals has gained much attention. This paper reports on the development of a nanoceria-nanoplatinum-graphene hybrid nanocomposite as a base transducing layer for mediator-free enzymatic biosensors. The hybrid nanocomposite was shown to improve detection of superoxide or hydrogen peroxide when compared to other carbon-metal hybrid nanocomposites. Based on this finding, the nanocomposite was applied for biosensing by adding either a peroxide-producing oxidase (glucose oxidase), or a superoxide-producing oxidase (xanthine oxidase). Material analysis indicated that nanoceria and nanoplatinum were equally distributed along the surface of the hybrid material, ensuring detection of either superoxide or hydrogen peroxide produced by oxidase activity. Glucose biosensors demonstrated a sensitivity (66.2±2.6μAmM(-1)cm(-2)), response time (6.3±3.4s), and limit of detection (1.3±0.6μM) that were comparable to other graphene-mediated electrodes in the current literature. Remarkably, XOD biosensor sensitivity (1164±332μAmM(-1)), response time (5.0±1.5s), and limit of detection (0.2±0.1μM) were higher than any reported biosensors using similar metal-decorated carbon nanomaterials. This material is the first demonstration of a highly efficient, diverse nanoceria/nanoplatinum/graphene hybrid nanocomposite for biosensing.

Nanoparticle Characterization for Cancer Nanotechnology and Other Biological Applications

Nanotechnology is actively being used to develop promising diagnostics and therapeutics tools for the treatment of cancer and many other diseases. The unique properties of nanomaterials offer an exciting frontier of possibilities for biomedical researchers and scientists. Because existing knowledge of macroscopic materials does not always allow for adequate prediction of the characteristics and behaviors of nanoscale materials in controlled environments, much less in biological systems, careful nanoparticle characterization should accompany biomedical applications of these materials. Informed correlations between adequately characterized nanomaterial properties and reliable biological endpoints are essential for guiding present and future researchers toward clinical nanotechnology-based solutions for cancer. Biological environments are notoriously dynamic; hence, nanoparticulate interactions within these environments will likely be comparatively diverse. For this reason, we recommend that an interactive and systematic approach to material characterization be taken when attempting to elucidate or measure biological interactions with nanoscale materials. We intend for this chapter to be a practical guide that could be used by researchers to identify key nanomaterial characteristics that require measurement for their systems and the appropriate techniques to perform those measurements. Each section includes a basic overview of each measurement and notes on how to address some of the common difficulties associated with nanomaterial characterization.

Targeted delivery of let-7a microRNA encapsulated ephrin-A1 conjugated liposomal nanoparticles inhibit tumor growth in lung cancer

MicroRNAs (miRs) are small noncoding RNA sequences that negatively regulate the expression of target genes by posttranscriptional repression. miRs are dysregulated in various diseases, including cancer. let-7a miR, an antioncogenic miR, is downregulated in lung cancers. Our earlier studies demonstrated that let-7a miR inhibits tumor growth in malignant pleural mesothelioma (MPM) and could be a potential therapeutic against lung cancer. EphA2 (ephrin type-A receptor 2) tyrosine kinase is overexpressed in most cancer cells, including MPM and non-small-cell lung cancer (NSCLC) cells. Ephrin-A1, a specific ligand of the EphA2 receptor, inhibits cell proliferation and migration. In this study, to enhance the delivery of miR, the miRs were encapsulated in the DOTAP (N-[1-(2.3-dioleoyloxy)propyl]-N,N,N-trimethyl ammonium)/Cholesterol/DSPE (1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[cyanur(polyethylene glycol)-2000])-PEG (polyethylene glycol)-cyanur liposomal nanoparticles (LNP) and ephrin-A1 was conjugated on the surface of LNP to target receptor EphA2 on lung cancer cells. The LNP with an average diameter of 100 nm showed high stability, low cytotoxicity, and high loading efficiency of precursor let-7a miR and ephrin-A1. The ephrin-A1 conjugated LNP (ephrin-A1–LNP) and let-7a miR encapsulated LNP (miR–LNP) showed improved transfection efficiency against MPM and NSCLC. The effectiveness of targeted delivery of let-7a miR encapsulated ephrin-A1 conjugated LNP (miR–ephrin-A1–LNP) was determined on MPM and NSCLC tumor growth in vitro. miR–ephrin-A1–LNP significantly increased the delivery of let-7a miR in lung cancer cells when compared with free let-7a miR. In addition, the expression of target gene Ras was significantly repressed following miR–ephrin-A1–LNP treatment. Furthermore, the miR–ephrin-A1–LNP complex significantly inhibited MPM and NSCLC proliferation, migration, and tumor growth. Our results demonstrate that the engineered miR–ephrin-A1–LNP complex is an effective carrier for the targeted delivery of small RNA molecules to lung cancer cells. This could be a potential therapeutic approach against tumors overexpressing the EphA2 receptor.

Nanoparticle delivery for metastatic breast cancer

Breast cancer represents a major ongoing public health problem as the most common non-cutaneous malignancy among U.S. women. While significant progress has been made in improving loco-regional treatments for breast cancer, relatively little progress has been made in diagnosing and treating patients with metastatic breast cancer. At present there are limited curative options for patients with breast cancer metastatic beyond regional nodes. Emerging nanotechnologies promise new approaches to early detection and treatment of metastatic breast cancer. Fulfilling the promise of nanotechnologies for patients with metastatic breast cancer will require delivery of nanomaterials to sites of metastatic disease. Future translational approaches will rely on an ever increasing understanding of the biology of breast cancer subtypes and their metastases. These important concepts will be highlighted and elucidated in this manuscript.