The Molecular Analysis of Breast Cancer Utilizing Targeted Nanoparticle Based Ultrasound Contrast Agents

A nanomechanical model enables comprehensive characterization of biological tissues in ultrasound imaging

Sonography, elastography, sonoelastography are ultrasound imaging techniques commonly used in the clinical practice for the diagnosis of many pathological conditions. These highly reliable, non-invasive methods use high frequency, elastic pressure waves (ultrasounds) to interrogate the internal structure of biological tissues and organs, and the continuum mechanics hypothesis to reconstruct, from the output of the system, the biophysical characteristics of the samples. Nevertheless, continuum mechanics disregards the discrete nature of tissues and organs, resulting in an inability for the model to describe some important tissue biophysical characteristics such as the cell size and their spatial layout. Here, we used the theory of doublet mechanics - a discrete nano-mechanical field theory - to model the propagation of ultrasounds in a multilayered biological tissue. We found that the output of the model exhibits a very high sensitivity to the macro and micro characteristics of the tissue, including cell size. We used results from the model to correlate the internal structure of the samples to the reflection coefficient, i.e. the continuum level response of the system. This model, and its more sophisticated evolutions that will be developed over time, can complement traditional ultrasound imaging, and provide ways to analyze non-invasively living tissues with a resolution inaccessible to conventional techniques of analysis, including positron emission tomography, computer tomography, and magnetic resonance.

Recent Advancements of Magnetic Nanomaterials in Cancer Therapy

Magnetic nanomaterials belong to a class of highly-functionalizable tools for cancer therapy owing to their intrinsic magnetic properties and multifunctional design that provides a multimodal theranostics platform for cancer diagnosis, monitoring, and therapy. In this review article, we have provided an overview of the various applications of magnetic nanomaterials and recent advances in the development of these nanomaterials as cancer therapeutics. Moreover, the cancer targeting, potential toxicity, and degradability of these nanomaterials has been briefly addressed. Finally, the challenges for clinical translation and the future scope of magnetic nanoparticles in cancer therapy are discussed.

Applications of nanoparticles in biomedical imaging

An urgent need for early detection and diagnosis of diseases continuously pushes the advancements of imaging modalities and contrast agents. Current challenges remain for fast and detailed imaging of tissue microstructures and lesion characterization that could be achieved via development of nontoxic contrast agents with longer circulation time. Nanoparticle technology offers this possibility. Here, we review nanoparticle-based contrast agents employed in most common biomedical imaging modalities, including fluorescence imaging, MRI, CT, US, PET and SPECT, addressing their structure related features, advantages and limitations. Furthermore, their applications in each imaging modality are also reviewed using commonly studied examples. Future research will investigate multifunctional nanoplatforms to address safety, efficacy and theranostic capabilities. Nanoparticles as imaging contrast agents have promise to greatly benefit clinical practice.

Theranostic nanoparticles carrying doxorubicin attenuate targeting ligand specific antibody responses following systemic delivery

Understanding the effects of immune responses on targeted delivery of nanoparticles is important for clinical translations of new cancer imaging and therapeutic nanoparticles. In this study, we found that repeated administrations of magnetic iron oxide nanoparticles (IONPs) conjugated with mouse or human derived targeting ligands induced high levels of ligand specific antibody responses in normal and tumor bearing mice while injections of unconjugated mouse ligands were weakly immunogenic and induced a very low level of antibody response in mice. Mice that received intravenous injections of targeted and polyethylene glycol (PEG)-coated IONPs further increased the ligand specific antibody production due to differential uptake of PEG-coated nanoparticles by macrophages and dendritic cells. However, the production of ligand specific antibodies was markedly inhibited following systemic delivery of theranostic nanoparticles carrying a chemotherapy drug, doxorubicin. Targeted imaging and histological analysis revealed that lack of the ligand specific antibodies led to an increase in intratumoral delivery of targeted nanoparticles. Results of this study support the potential of further development of targeted theranostic nanoparticles for the treatment of human cancers.

Nanobiosensors: role in cancer detection and diagnosis

The ability to detect many cancers at an early stage in its clinical course has the potential to improve patient outcomes in terms of morbidity and mortality. Nanosized components incorporated into existing clinical diagnostic and detection systems as well as novel nanobiosensors have demonstrated improved sensitivity and specificity compared with traditional cancer testing approaches. Nanoparticles, nanowires, nanotubes, and nanocantilevers are examples of four nanobiosensor systems that have been used experimentally in the context of detection and diagnosis of prostate, breast, pancreatic, lung, and brain cancers over the past few years. Nanobiosensors will begin to transition into clinically validated tests as experimental and engineering techniques advance. This paper presents examples of some such nanobiosensors for cancer diagnosis and detection.

Physically facilitating drug-delivery systems

Facilitated/modulated drug-delivery systems have emerged as a possible solution for delivery of drugs of interest to pre-allocated sites at predetermined doses for predefined periods of time. Over the past decade, the use of different physical methods and mechanisms to mediate drug release and delivery has grown significantly. This emerging area of research has important implications for development of new therapeutic drugs for efficient treatments. This review aims to introduce and describe different modalities of physically facilitating drug-delivery systems that are currently in use for cancer and other diseases therapy. In particular, delivery methods based on ultrasound, electrical, magnetic and photo modulations are highlighted. Current uses and areas of improvement for these different physically facilitating drug-delivery systems are discussed. Furthermore, the main advantages and drawbacks of these technologies reviewed are compared. The review ends with a speculative viewpoint of how research is expected to evolve in the upcoming years.

Development of polymeric microbubbles targeted to prostate-specific membrane antigen as prototype of novel ultrasound contrast agents

Ultrasound-targeted microbubbles (MBs) offer new opportunities to enhance the capabilities of diagnostic ultrasound (US) imaging to specific pathological tissue. Herein, we report on the design and development of a novel prototype of US contrast agent based on polymeric MBs targeted to prostate-specific membrane antigen (PSMA) for use in the diagnosis of prostate cancer (PCa). First, a set of air-filled MBs by a variety of biocompatible polymers were prepared and characterized in terms of morphology and echogenic properties after exposure to US. MBs derived from poly(D,L-lactic-co-glycolic acid) (PLGA)-poly(ethylene glycol) (PEG) copolymer resulted as the most effective in terms of reflectivity. Such polymer was therefore preconjugated with a urea-based PSMA inhibitor molecular probe (DCL), and the obtained MBs were investigated in vitro for their targeting efficacy toward PSMA positive PCa (LNCaP) cells. Fluorescence microscopy proved a specific and efficient adhesion of targeted MBs to LNCaP cells. To our knowledge, this work reports the first model of polymeric MBs appropriately engineered to target PSMA, which might be further optimized and used for PCa diagnosis and potential carriers for selective drug delivery.

Estimating design space available for polyepitopes through consideration of major histocompatibility complex binding motifs

Major histocompatibility complex (MHC ) epitope presentation is needed for robust adaptive immune responses. Core peptide binding motifs for class I and class II MHC are 8-10 amino acids long, containing two or more "anchor" residues. These binding motifs define epitope anchor amino acid content and spacing, and knowledge of them has facilitated emergence of polyepitope vaccines. However, polyepitopes can exhibit "junctional epitopes" (neoepitopes interfering with vaccine function) resulting from juxtaposition of authentic epitopes. We have developed an algorithm for consideration of polyepitope sequence in light of MHC motifs to exhaustively identify all junctional-free polyepitope designs for any given set of authentic epitopes, and in so doing discovered that the number of such variants of any given polyepitope can be astronomically high. Our approach designs polyepitopes of any length, considers multiple MHC class I or class II motifs simultaneously and can be adapted to design variants of existing proteins with pre-selected epitope contents. We have also implemented the algorithm as a computer-based tool (CANVAC II), which we make available to interested parties. The vast diversity of junctional-free polyepitopes suggests that the number of potential T-helper epitope free protein variants may also be large, which may have implications for discovery of bioactive but non-immunogenic therapeutics.

Design and fabrication of magnetic nanoparticles for targeted drug delivery and imaging

Magnetic nanoparticles (MNPs) represent a class of non-invasive imaging agents that have been developed for magnetic resonance (MR) imaging. These MNPs have traditionally been used for disease imaging via passive targeting, but recent advances have opened the door to cellular-specific targeting, drug delivery, and multi-modal imaging by these nanoparticles. As more elaborate MNPs are envisioned, adherence to proper design criteria (e.g. size, coating, molecular functionalization) becomes even more essential. This review summarizes the design parameters that affect MNP performance in vivo, including the physicochemical properties and nanoparticle surface modifications, such as MNP coating and targeting ligand functionalizations that can enhance MNP management of biological barriers. A careful review of the chemistries used to modify the surfaces of MNPs is also given, with attention paid to optimizing the activity of bound ligands while maintaining favorable physicochemical properties.

Core-shell hydrogel particles harvest, concentrate and preserve labile low abundance biomarkers

Background

The blood proteome is thought to represent a rich source of biomarkers for early stage disease detection. Nevertheless, three major challenges have hindered biomarker discovery: a) candidate biomarkers exist at extremely low concentrations in blood; b) high abundance resident proteins such as albumin mask the rare biomarkers; c) biomarkers are rapidly degraded by endogenous and exogenous proteinases.

Methodology and Principal Findings

Hydrogel nanoparticles created with a N-isopropylacrylamide based core (365 nm)-shell (167 nm) and functionalized with a charged based bait (acrylic acid) were studied as a technology for addressing all these biomarker discovery problems, in one step, in solution. These harvesting core-shell nanoparticles are designed to simultaneously conduct size exclusion and affinity chromatography in solution. Platelet derived growth factor (PDGF), a clinically relevant, highly labile, and very low abundance biomarker, was chosen as a model. PDGF, spiked in human serum, was completely sequestered from its carrier protein albumin, concentrated, and fully preserved, within minutes by the particles. Particle sequestered PDGF was fully protected from exogenously added tryptic degradation. When the nanoparticles were added to a 1 mL dilute solution of PDGF at non detectable levels (less than 20 picograms per mL) the concentration of the PDGF released from the polymeric matrix of the particles increased within the detection range of ELISA and mass spectrometry. Beyond PDGF, the sequestration and protection from degradation for a series of additional very low abundance and very labile cytokines were verified.

Conclusions and Significance

We envision the application of harvesting core-shell nanoparticles to whole blood for concentration and immediate preservation of low abundance and labile analytes at the time of venipuncture.

Multifunctional magnetic nanoparticles for targeted imaging and therapy

Magnetic nanoparticles have become important tools for the imaging of prevalent diseases, such as cancer, atherosclerosis, diabetes, and others. While first generation nanoparticles were fairly nonspecific, newer generations have been targeted to specific cell types and molecular targets via affinity ligands. Commonly, these ligands emerge from phage or small molecule screens, or are based on antibodies or aptamers. Secondary reporters and combined therapeutic molecules have further opened potential clinical applications of these materials. This review summarizes some of the recent biomedical applications of these newer magnetic nanomaterials.

In vitro immunogenicity of silicon-based micro- and nanostructured surfaces

The increasing use of micro- and nanostructured silicon-based devices for in vivo therapeutic or sensing applications highlights the importance of understanding the immunogenicity of these surfaces. Four silicon surfaces (nanoporous, microstructured, nanochanneled, and flat) were studied for their ability to provoke an immune response in human blood derived monocytes. The monocytes were incubated with the surfaces for 48 h and the immunogenicity was evaluated based on the viability, shape factors, and cytokine expression. Free radical oxygen formation was measured at 18 h to elicit a possible mechanism invoking immunogenicity. Although no cytokines were significantly different comparing the response of monocytes on the tissue culture polystyrene surfaces to those on the micropeaked surfaces, on average all cytokines were elevated on the micropeaked surface. The monocytes on the nanoporous surface also displayed an elevated cytokine response, overall, but not to the degree of those on the micropeaked surface. The nanochanneled surface response was similar to that of flat silicon. Overall, the immunogenicity and biocompatibility of flat, nanochanneled, and nanoporous silicon toward human monocytes are approximately equivalent to tissue culture polystyrene.

Biomedical nanotechnology for cancer

Nanotechnology may hold the key to controlling many devastating diseases. In the fight against the pain, suffering, and death due to cancer, nanotechnology will allow earlier diagnosis and even prevention of malignancy at premalignant stages, in addition to providing multimodality treatment not possible with current conventional techniques. This review discusses nanotechnology already used in diagnostic and therapeutic applications for cancer. Also addressed are theoretic and evolving uses of nanotechnology, including multifunctional nanoparticles for imaging and therapy, nanochannel implants for controlled release of drugs, nanoscale devices for evaluation of proteomics and genomics, and diagnostic techniques that take advantage of physical changes in diseased tissue.

Recent advances in basic and clinical nanomedicine

Nanomedicine is a global business enterprise. Industry and governments clearly are beginning to envision nanomedicine's enormous potential. A clear definition of nanotechnology is an issue that requires urgent attention. This problem exists because nanotechnology represents a cluster of technologies, each of which may have different characteristics and applications. Although numerous novel nanomedicine-related applications are under development or nearing commercialization, the process of converting basic research in nanomedicine into commercially viable products will be long and difficult. Although realization of the full potential of nanomedicine may be years or decades away, recent advances in nanotechnology-related drug delivery, diagnosis, and drug development are beginning to change the landscape of medicine. Site-specific targeted drug delivery and personalized medicine are just a few concepts that are on the horizon.

Antibiological barrier nanovector technology for cancer applications

The advent of sophisticated drug delivery strategies for cancer applications has inundated the scientific and clinical community with new tactics and approaches such as molecular targeting, nanotechnology-based methods and personalized therapies. Unfortunately, the clinical impact has been moderate at best, falling significantly short from revolutionizing existing chemotherapeutic methodologies. To this day, a cancer patient has a higher probability of receiving traditional systemically administered drugs than a more sophisticated targeted or nanotechnology-based therapeutic. This is not a reflection upon the novelty or quality of the technologies, but an indication of opportunity for a new approach that offers the realisation of the full potential of these scientific advances. This approach acknowledges the significance of the numerous biological barriers presented in the human body and their sequential nature. It is then recommended that computational mathematical tools are used to predict which nanovectors, surface modifications, therapeutic agents and penetration enhancers to use for a multi-stage drug delivery strategy. An approach where several stages of micro-/nano-vectors are nested within each other and delivered to overcome specific biological barriers to ultimately release a concentrated dose of a therapeutic payload at the intended lesion site. This novel, multi-stage strategy enables efficient localised delivery of chemotoxic drugs that may lead to significant improvements in therapy efficacy, reduced systemic toxicity and decreased total amount of injected drugs.

Polymeric ultrasound contrast agents targeted to integrins: importance of process methods and surface density of ligands

The use of injectable gas-filled microbubbles during ultrasound imaging is accepted as a good method to increase image contrast. Site-targeted microbubbles are expected to provide higher sensitivity and specificity than blood pool contrast agents (CAs). We have shown that covalent attachment of GRGDS peptide fragments to the surface of poly(lactic acid) CAs facilitates attachment to MDA-MB-231 human breast cancer cells in vitro. This paper examines the effect of process conditions during microbubble fabrication and ligand attachment and also changes in ligand surface density and shows that they have important effects on in vitro acoustic response and CA adhesion to breast cancer and cell lines. Use of intermittent sonication in the emulsion step, shortening of reaction times, and increase in freeze-drying times allows for a reduction of 50% in the dose of GRGDS-modified capsules (from 0.16 to 0.012 mg/mL) required to achieve a maximum enhancement of 20 dB; signal loss after 15 min insonation of GRGDS-modified capsules is reduced from a loss of 60% to a loss of 40%, and cell attachment after 10 min contact time is increased from an average of 1.4 +/- 0.86 to 1.8 +/- 0.17 capsules/cell. Optimal attachment is achieved with a molar ratio of total -COOH groups to GRGDS of 1:0.5. The effect of process conditions during microcapsule fabrication, ligand attachment, and ligand surface density on in vitro acoustic response and CA adhesion to breast cancer cell lines in tissue culture are shown to be important parameters that can aid in the future design of an ultrasound CA that allows both cancer detection and treatment, potentially by targeted drug delivery.

Nanotechnological applications in medicine

Nanotechnology-based tools and techniques are rapidly emerging in the fields of medical imaging and targeted drug delivery. Employing constructs such as dendrimers, liposomes, nanoshells, nanotubes, emulsions and quantum dots, these advances lead toward the concept of personalized medicine and the potential for very early, even pre-symptomatic, diagnoses coupled with highly-effective targeted therapy. Highlighting clinically available and preclinical applications, this review explores the opportunities and issues surrounding nanomedicine.