Magnetic resonance molecular imaging with nanoparticles

Surface functionalized nanoparticles: A boon to biomedical science

The rapid development of nanomedicine has increased the likelihood that manufactured nanoparticles will one day come into contact with people and the environment. A variety of academic fields, including engineering and the health sciences, have taken a keen interest in the development of nanotechnology. Any significant development in nanomaterial-based applications would depend on the production of functionalized nanoparticles, which are believed to have the potential to be used in fields like pharmaceutical and biomedical sciences. The functionalization of nanoparticles with particular recognition chemical moieties does result in multifunctional nanoparticles with greater efficacy while at the same time minimising adverse effects, according to early clinical studies. This is because of traits like aggressive cellular uptake and focused localization in tumours. To advance this field of inquiry, chemical procedures must be developed that reliably attach chemical moieties to nanoparticles. The structure-function relationship of these functionalized nanoparticles has been extensively studied as a result of the discovery of several chemical processes for the synthesis of functionalized nanoparticles specifically for drug delivery, cancer therapy, diagnostics, tissue engineering, and molecular biology. Because of the growing understanding of how to functionalize nanoparticles and the continued work of innovative scientists to expand this technology, it is anticipated that functionalized nanoparticles will play an important role in the aforementioned domains. As a result, the goal of this study is to familiarise readers with nanoparticles, to explain functionalization techniques that have already been developed, and to examine potential applications for nanoparticles in the biomedical sciences. This review's information is essential for the safe and broad use of functionalized nanoparticles, particularly in the biomedical sector.

Albumin-based nanoparticles as contrast medium for MRI: vascular imaging, tissue and cell interactions, and pharmacokinetics of second-generation nanoparticles

This multidisciplinary study examined the pharmacokinetics of nanoparticles based on albumin-DTPA-gadolinium chelates, testing the hypothesis that these nanoparticles create a stronger vessel signal than conventional gadolinium-based contrast agents and exploring if they are safe for clinical use. Nanoparticles based on human serum albumin, bearing gadolinium and designed for use in magnetic resonance imaging, were used to generate magnet resonance images (MRI) of the vascular system in rats ("blood pool imaging"). At the low nanoparticle doses used for radionuclide imaging, nanoparticle-associated metals were cleared from the blood into the liver during the first 4 h after nanoparticle application. At the higher doses required for MRI, the liver became saturated and kidney and spleen acted as additional sinks for the metals, and accounted for most processing of the nanoparticles. The multiple components of the nanoparticles were cleared independently of one another. Albumin was detected in liver, spleen, and kidneys for up to 2 days after intravenous injection. Gadolinium was retained in the liver, kidneys, and spleen in significant concentrations for much longer. Gadolinium was present as significant fractions of initial dose for longer than 2 weeks after application, and gadolinium clearance was only complete after 6 weeks. Our analysis could not account quantitatively for the full dose of gadolinium that was applied, but numerous organs were found to contain gadolinium in the collagen of their connective tissues. Multiple lines of evidence indicated intracellular processing opening the DTPA chelates and leading to gadolinium long-term storage, in particular inside lysosomes. Turnover of the stored gadolinium was found to occur in soluble form in the kidneys, the liver, and the colon for up to 3 weeks after application. Gadolinium overload poses a significant hazard due to the high toxicity of free gadolinium ions. We discuss the relevance of our findings to gadolinium-deposition diseases.

Perfluorocarbons-Based 19F Magnetic Resonance Imaging in Biomedicine

Fluorine-19 (¹⁹F) magnetic resonance (MR) molecular imaging is a promising noninvasive and quantitative molecular imaging approach with intensive research due to the high sensitivity and low endogenous background signal of the ¹⁹F atom in vivo. Perfluorocarbons (PFCs) have been used as blood substitutes since 1970s. More recently, a variety of PFC nanoparticles have been designed for the detection and imaging of physiological and pathological changes. These molecular imaging probes have been developed to label cells, target specific epitopes in tumors, monitor the prognosis and therapy efficacy and quantitate characterization of tumors and changes in tumor microenvironment noninvasively, therefore, significantly improving the prognosis and therapy efficacy. Herein, we discuss the recent development and applications of ¹⁹F MR techniques with PFC nanoparticles in biomedicine, with particular emphasis on ligand-targeted and quantitative ¹⁹F MR imaging approaches for tumor detection, oxygenation measurement, smart stimulus response and therapy efficacy monitoring, et al.

SiO2-PVA-Fe(acac)3 Hybrid Based Superparamagnetic Nanocomposites for Nanomedicine: Morpho-textural Evaluation and In Vitro Cytotoxicity Assay

A facile sol-gel route has been applied to synthesize hybrid silica-PVA-iron oxide nanocomposite materials. A step-by-step calcination (processing temperatures up to 400 °C) was applied in order to oxidize the organics together with the iron precursor. Transmission electron microscopy, X-ray diffraction, small angle neutron scattering, and nitrogen porosimetry were used to determine the temperature-induced morpho-textural modifications. In vitro cytotoxicity assay was conducted by monitoring the cell viability by the means of MTT assay to qualify the materials as MRI contrast agents or as drug carriers. Two cell lines were considered: the HaCaT (human keratinocyte cell line) and the A375 tumour cell line of human melanoma. Five concentrations of 10 µg/mL, 30 µg/mL, 50 µg/mL, 100 µg/mL, and 200 µg/mL were tested, while using DMSO (dimethylsulfoxid) and PBS (phosphate saline buffer) as solvents. The HaCaT and A375 cell lines were exposed to the prepared agent suspensions for 24 h. In the case of DMSO (dimethyl sulfoxide) suspensions, the effect on human keratinocytes migration and proliferation were also evaluated. The results indicate that only the concentrations of 100 μg/mL and 200 μg/mL of the nanocomposite in DMSO induced a slight decrease in the HaCaT cell viability. The PBS based in vitro assay showed that the nanocomposite did not present toxicity on the HaCaT cells, even at high doses (200 μg/mL agent).

Designing Calcium-Binding Proteins for Molecular MR Imaging

Early diagnosis, noninvasive detection, and staging of various diseases, remain one of the major clinical barriers to effective medical treatment and prevention of disease progression toward major clinical consequences. Molecular imaging technologies play an indispensable role in the clinical field in overcoming these major barriers. The increasing application of imaging techniques and agents in early detection of different diseases such as cancer has resulted in improved treatment response and clinical patient management. In this chapter we will first introduce criteria for the design and engineering of calcium-binding protein (CaBP) parvalbumin as a protein Gd-MRI contrast agent (ProCA) with unprecedented metal selectivity for Gd³⁺ over physiological metal ions. We will then discuss the further development of targeted MRI contrast agent for molecular imaging of PSMA biomarker for early detection of prostate cancer.

Ratiometric optical nanoprobes enable accurate molecular detection and imaging

Exploring and understanding biological and pathological changes are of great significance for early diagnosis and therapy of diseases. Optical sensing and imaging approaches have experienced major progress in this field. Particularly, an emergence of various functional optical nanoprobes has provided enhanced sensitivity, specificity, targeting ability, as well as multiplexing and multimodal capabilities due to improvements in their intrinsic physicochemical and optical properties. However, one of the biggest challenges of conventional optical nanoprobes is their absolute intensity-dependent signal readout, which causes inaccurate sensing and imaging results due to the presence of various analyte-independent factors that can cause fluctuations in their absolute signal intensity. Ratiometric measurements provide built-in self-calibration for signal correction, enabling more sensitive and reliable detection. Optimizing nanoprobe designs with ratiometric strategies can surmount many of the limitations encountered by traditional optical nanoprobes. This review first elaborates upon existing optical nanoprobes that exploit ratiometric measurements for improved sensing and imaging, including fluorescence, surface enhanced Raman scattering (SERS), and photoacoustic nanoprobes. Next, a thorough discussion is provided on design strategies for these nanoprobes, and their potential biomedical applications for targeting specific biomolecule populations (e.g. cancer biomarkers and small molecules with physiological relevance), for imaging the tumor microenvironment (e.g. pH, reactive oxygen species, hypoxia, enzyme and metal ions), as well as for intraoperative image guidance of tumor-resection procedures.

Assessing the selective therapeutic efficacy of superparamagnetic erlotinib nanoparticles in lung cancer by using quantitative magnetic resonance imaging and a nuclear factor kappa-B reporter gene system

Non-small-cell lung cancer (NSCLC) is the most common type of lung cancer. Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors are commonly used as the first-line treatment for advanced NSCLC; however, the efficacy of drug delivery remains unknown. Hence, we successfully developed erlotinib-conjugated iron oxide nanoparticles (FeDC-E NPs) as theranostic probe that can potentially provide a new avenue for monitoring drug delivering through noninvasive magnetic resonance imaging. MRI ΔR2* relaxivity measurements offer an opportunity to quantitatively evaluate the uptake of FeDC-E NPs at cellular and tumoral levels. Additionally, NF-κB reporter gene system provides NF-κB activation status monitoring to validate the therapeutic efficiency of FeDC-E NPs. FeDC-E NPs not only inhibit the tumor growth and NF-κB-modulated antiapoptotic mechanism but also trigger extrinsic and intrinsic apoptotic pathways. Taken together, dual functional FeDC-E NPs offer diagnostic and therapeutic benefits against lung cancers, indicating that our presented probe could be applied in clinical.

Optimization of the composition and dosage of PEGylated polyethylenimine-entrapped gold nanoparticles for blood pool, tumor, and lymph node CT imaging

Gold nanoparticles (Au NPs) with a high X-ray attenuation coefficient have a good potential in CT imaging applications. Here, we report the design and synthesis of Au NPs entrapped within polyethylene glycol (PEG)-modified branched polyethyleneimine (PEI) with varying the initial Au salt/PEI molar ratios and with the remaining PEI surface amines being acetylated for blood pool, lung tumor and lymph node CT imaging. The formed unacetylated and acetylated PEGylated PEI-entrapped Au NPs (Au PENPs) were characterized via different methods. We show that the PEGylated PEI is an effective template to entrap Au NPs having a uniform size ranging from 1.7nm to 4.4nm depending on the Au salt/PEI molar ratio. After optimization of the composition-dependent X-ray attenuation effect, we then selected {(Au⁰)₁₀₀-PEI·NHAc-mPEG} NPs for biological testing and show that the particles have good cytocompatibility in the given concentration range and can be used as a contrast agent for effective CT imaging of the blood pool of rats, lung cancer model of nude mice and lymph node of rabbits after intravenous injection. For each application, the injected dosage of the particles was optimized. In addition, the {(Au⁰)₁₀₀-PEI·NHAc-mPEG} NPs could be excreted out of the body with time. Our results indicate that the formed Au PENPs with an appropriate composition and dosage hold a great promise to be used for CT imaging of various biosystems.

Copper-64 Radiopharmaceuticals for Oncologic Imaging

The positron emitting radionuclide (64)Cu has a radioactive half-life of 12.7 hours. The decay characteristics of (64)Cu allow for PET images that are comparable in quality to those obtained using (18)F. Given the longer radioactive half-life of (64)Cu compared with (18)F and the versatility of copper chemistry, copper is an attractive alternative to the shorter-lived nuclides for PET imaging of peptides, antibodies, and small molecules that may require longer circulation times. This article discusses a number of copper radiopharmaceuticals, such as Cu-ATSM, that have been translated to the clinic and new developments in copper-based radiopharmaceuticals.

Molecular imaging of atherosclerosis with nanoparticle-based fluorinated MRI contrast agents

As atherosclerosis remains one of the most prevalent causes of patient mortality, the ability to diagnose early signs of plaque rupture and thrombosis represents a significant clinical need. With recent advances in nanotechnology, it is now possible to image specific molecular processes noninvasively with MRI, using various types of nanoparticles as contrast agents. In the context of cardiovascular disease, it is possible to specifically deliver contrast agents to an epitope of interest for detecting vascular inflammatory processes, which serve as predecessors to atherosclerotic plaque development. Herein, we review various applications of nanotechnology in detecting atherosclerosis using MRI, with an emphasis on perfluorocarbon nanoparticles and fluorine imaging, along with theranostic prospects of nanotechnology in cardiovascular disease.

Dendrimer-Based Responsive MRI Contrast Agents (G1-G4) for Biosensor Imaging of Redundant Deviation in Shifts (BIRDS)

Biosensor imaging of redundant deviation in shifts (BIRDS) is a molecular imaging platform for magnetic resonance that utilizes unique properties of low molecular weight paramagnetic monomers by detecting hyperfine-shifted nonexchangeable protons and transforming the chemical shift information to reflect its microenvironment (e.g., via temperature, pH, etc.). To optimize translational biosensing potential of BIRDS we examined if this detection scheme observed with monomers can be extended onto dendrimers, which are versatile and biocompatible macromolecules with modifiable surface for molecular imaging and drug delivery. Here we report on feasibility of paramagnetic dendrimers for BIRDS. The results show that BIRDS is resilient with paramagnetic dendrimers up to the fourth generation (i.e., G1-G4), where the model dendrimer and chelate were based on poly(amido amine) (PAMAM) and 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA(4-)) complexed with thulium ion (Tm(3+)). Temperature sensitivities of two prominent signals of Gn-PAMAM-(TmDOTA(-))x (where n = 1-4, x = 6-39) were comparable to that of prominent signals in TmDOTA(-). Transverse relaxation times of the coalesced nonexchangeable protons on Gn-PAMAM-(TmDOTA(-))x were relatively short to provide signal-to-noise ratio that was comparable to or better than that of TmDOTA(-). A fluorescent dye, rhodamine, was conjugated to a G2-PAMAM-(TmDOTA)12 to create a dual-modality nanosized contrast agent. BIRDS properties of the dendrimer were unaltered with rhodamine conjugation. Purposely designed paramagnetic dendrimers for BIRDS in conjunction with novel macromolecular surface modification for functional ligands/drugs could potentially be used for biologically compatible theranostic sensors.

Synthesis and Evaluation of Gd(III) -Based Magnetic Resonance Contrast Agents for Molecular Imaging of Prostate-Specific Membrane Antigen

Magnetic resonance (MR) imaging is advantageous because it concurrently provides anatomic, functional, and molecular information. MR molecular imaging can combine the high spatial resolution of this established clinical modality with molecular profiling in vivo. However, as a result of the intrinsically low sensitivity of MR imaging, high local concentrations of biological targets are required to generate discernable MR contrast. We hypothesize that the prostate-specific membrane antigen (PSMA), an attractive target for imaging and therapy of prostate cancer, could serve as a suitable biomarker for MR-based molecular imaging. We have synthesized three new high-affinity, low-molecular-weight Gd(III) -based PSMA-targeted contrast agents containing one to three Gd(III)  chelates per molecule. We evaluated the relaxometric properties of these agents in solution, in prostate cancer cells, and in an in vivo experimental model to demonstrate the feasibility of PSMA-based MR molecular imaging.

Prolonging the circulatory retention of SPIONs using dextran sulfate: in vivo tracking achieved by functionalisation with near-infrared dyes

The rapid reticuloendothelial system (RES) mediated clearance of superparamagnetic iron oxide nanoparticles (SPIONs) from circulation is considered a major limitation of their clinical utility. We aimed to address this by using dextran sulfate 500 (DSO4 500), a Kupffer cell blocking agent, to prolong SPIONs circulatory time. Blood concentrations of SPIONs are difficult to quantify due to the presence of haemoglobin. We therefore developed methods to functionalise SPIONs with near-infrared (NIR) dyes in order to trace their biodistribution. Two SPIONs were investigated: Nanomag®-D-spio-NH(2) and Ferucarbotran. Nanomag®-D-spio-NH(2) was functionalised using NHS (N-hydroxysuccinimide) ester NIR dye and Ferucarbotran was labelled using periodate oxidation followed by reductive amination or a combination of EDC (ethyl(dimethylaminopropyl) carbodiimide )/NHS and click chemistries. Stability after conjugation was confirmed by dynamic light scattering (DLS), superconducting quantum interference device (SQUID) and transmission electron microscopy (TEM). In vivo experiments with the functionalised SPIONs showed a significant improvement in SPIONs blood concentrations in mice pre-treated with dextran sulfate sodium salt 500 (DSO4 500).

Improved quantitative (19) F MR molecular imaging with flip angle calibration and B1 -mapping compensation

PURPOSE

To improve (19) F flip angle calibration and compensate for B1 inhomogeneities in quantitative (19) F MRI of sparse molecular epitopes with perfluorocarbon (PFC) nanoparticle (NP) emulsion contrast agents.

MATERIALS AND METHODS

Flip angle sweep experiments on PFC-NP point source phantoms with three custom-designed (19) F/(1) H dual-tuned coils revealed a difference in required power settings for (19) F and (1) H nuclei, which was used to calculate a calibration ratio specific for each coil. An image-based correction technique was developed using B1 -field mapping on (1) H to correct for (19) F and (1) H images in two phantom experiments.

RESULTS

Optimized (19) F peak power differed significantly from that of (1) H power for each coil (P < 0.05). A ratio of (19) F/(1) H power settings yielded a coil-specific and spatially independent calibration value (surface: 1.48 ± 0.06; semicylindrical: 1.71 ± 0.02, single-turn-solenoid: 1.92 ± 0.03). (1) H-image-based B1 correction equalized the signal intensity of (19) F images for two identical (19) F PFC-NP samples placed in different parts of the field, which were offset significantly by ~66% (P < 0.001), before correction.

CONCLUSION

(19) F flip angle calibration and B1 -mapping compensations to the (19) F images employing the more abundant (1) H signal as a basis for correction resulted in a significant change in the quantification of sparse (19) F MR signals from targeted PFC NP emulsions.

Engineered nanoparticles: thrombotic events in cancer

Engineered nanoparticles are being increasingly produced for specific applications in medicine. Broad selections of nano-sized constructs have been developed for applications in diagnosis, imaging, and drug delivery. Nanoparticles as contrast agents enable conjugation with molecular markers which are essential for designing effective diagnostic and therapeutic strategies. Such investigations can also lead to a better understanding of disease mechanisms such as cancer-associated thrombosis which remains unpredictable with serious bleeding complications and high risk of death. Here we review the recent and current applications of engineered nanoparticles in diagnosis and therapeutic strategies, noting their toxicity in relation to specific markers as a target.

Biologic properties of gadolinium diethylenetriaminepentaacetic acid-labeled and PKH26-labeled human umbilical cord mesenchymal stromal cells

BACKGROUND AIMS

This study was conducted to characterize gadolinium diethylenetriaminepentaacetic acid (Gd-DTPA)-labeled and PKH26-labeled human umbilical cord mesenchymal stromal cells (HuMSCs) and to track them with magnetic resonance imaging (MRI) in vitro and in vivo.

METHODS

HuMSCs were isolated from umbilical cords and expanded in vitro. Cells were sequentially labeled with Gd-DTPA and PKH26. The labeling efficiency was determined by spectrophotometry measurements, and the longevity of Gd-DTPA maintenance was measured with MRI. The influence of double labeling on cellular biologic properties was assessed by cell proliferation, viability, differentiation, cycle and apoptosis. Transplantation of double-labeled HuMSCs or placebo was performed in 39 female Sprague-Dawley rats. Leak point pressure and maximal bladder capacity were measured in animals 6 weeks after injection.

RESULTS

The T1 values and signal intensity on T1-weighted imaging of labeled cells were significantly higher than the control group (P < 0.05). The signal intensity on T1-weighted imaging of labeled cells was retained >14 days in vitro and in vivo. There was no significant difference in the cell cycle, cell apoptosis, cell proliferation and cell viability between labeled and unlabeled HuMSCs (P > 0.05). After double labeling, HuMSCs were still capable of differentiating into osteoblasts and adipocytes. Periurethrally injected HuMSCs in the rats significantly improved leak point pressure and maximal bladder capacity.

CONCLUSIONS

HuMSCs were successfully labeled with Gd-DTPA and PKH26. This labeling method is reliable and efficient and can be applied for tracking cells in vitro and in vivo without altering cellular biologic properties.

Nano-sized CT contrast agents

Computed tomography (CT) is one of the most widely used clinical imaging modalities. In order to increase the sensitivity of CT, small iodinated compounds are used as injectable contrast agents. However, the iodinated contrast agents are excreted through the kidney and have short circulation times. This rapid renal clearance not only restricts in vivo applications that require long circulation times but also sometimes induces serious adverse effects related to the excretion pathway. In addition, the X-ray attenuation of iodine is not efficient for clinical CT that uses high-energy X-ray. Due to these limitations, nano-sized iodinated CT contrast agents have been developed that can increase the circulation time and decrease the adverse effects. In addition to iodine, nanoparticles based on heavy atoms such as gold, lanthanides, and tantalum are used as more efficient CT contrast agents. In this review, we summarize the recent progresses made in nano-sized CT contrast agents.

Ultrasound-triggered BSA/SPION hybrid nanoclusters for liver-specific magnetic resonance imaging

Nanoclusters of superparamagnetic iron oxide nanoparticles (SPION) are developed for liver-specific magnetic resonance imaging (MRI) by a unique synthesis route. The process is efficient, environmentally benign, and straight forward within five minutes. The clustering effect is triggered in the presence of bovine serum albumin (BSA) aqueous phase under ultrasonication condition. The hydrophobic SPION are densely self-assembled into BSA/SPION hybrid nanoclusters with a uniform size of ~86 nm. The as-prepared BSA/SPION hybrid nanoclusters are found to be biocompatible and stable. They exhibit high transverse relaxivity and longitudinal relaxivity in water (r(2) and r(1) values are 600.8 and 4.3 s(-1) per mM of Fe(3+), respectively). In vivo T(2)-weighted MRI shows excellent enhancement in liver with an imaging time-window up to 48 h. In vivo biodistribution study indicates a gradual excretion of the nanoclusters via hepatobiliary (HB) processing. No toxicity is observed in the in vivo and ex vivo experiments. The BSA/SPION hybrid nanoclusters present great potential in MRI as the liver-specific contrast agents (CAs).

Specific biomarkers of receptors, pathways of inhibition and targeted therapies: pre-clinical developments

A deeper understanding of the role of specific genes, proteins, pathways and networks in health and disease, coupled with the development of technologies to assay these molecules and pathways in patients, promises to revolutionise the practice of clinical medicine. Especially the discovery and development of novel drugs targeted to disease-specific alterations could benefit significantly from non-invasive imaging techniques assessing the dynamics of specific disease-related parameters. Here we review the application of imaging biomarkers in the management of patients with brain tumours, especially malignant glioma. In our other review we focused on imaging biomarkers of general biochemical and physiological processes related with tumour growth such as energy, protein, DNA and membrane metabolism, vascular function, hypoxia and cell death. In this part of the review, we will discuss the use of imaging biomarkers of specific disease-related molecular genetic alterations such as apoptosis, angiogenesis, cell membrane receptors and signalling pathways and their application in targeted therapies.

Synthesis and evaluation of a peptide targeted small molecular Gd-DOTA monoamide conjugate for MR molecular imaging of prostate cancer

Tumor extracellular matrix has an abundance of cancer related proteins that can be used as biomarkers for cancer molecular imaging. Innovative design and development of safe and effective targeted contrast agents to these biomarkers would allow effective MR cancer molecular imaging with high spatial resolution. In this study, we synthesized a low molecular weight CLT1 peptide targeted Gd(III) chelate CLT1-dL-(Gd-DOTA)(4) specific to clotted plasma proteins in tumor stroma for cancer MR molecular imaging. CLT1-dL-(Gd-DOTA)(4) was synthesized by conjugating four Gd-DOTA monoamide chelates to a CLT1 peptide via generation 1 lysine dendrimer. The T(1) relaxivity of CLT1-dL-(Gd-DOTA)(4) was 40.4 mM(-1) s(-1) per molecule (10.1 mM(-1) s(-1) per Gd) at 37 °C and 1.5 T. Fluorescence imaging showed high binding specificity of CLT1 to orthotopic PC3 prostate tumor in mice. The contrast agent resulted in improved tumor contrast enhancement in male athymic nude mice bearing orthotopic PC3 prostate tumor xenograft at a dose of 0.03 mmol Gd/kg. The peptide targeted MRI contrast agent is promising for high-resolution MR molecular imaging of prostate tumor.

Novel multifunctional theranostic liposome drug delivery system: construction, characterization, and multimodality MR, near-infrared fluorescent, and nuclear imaging

Liposomes are effective lipid nanoparticle drug delivery systems, which can also be functionalized with noninvasive multimodality imaging agents with each modality providing distinct information and having synergistic advantages in diagnosis, monitoring of disease treatment, and evaluation of liposomal drug pharmacokinetics. We designed and constructed a multifunctional theranostic liposomal drug delivery system, which integrated multimodality magnetic resonance (MR), near-infrared (NIR) fluorescent and nuclear imaging of liposomal drug delivery, and therapy monitoring and prediction. The premanufactured liposomes were composed of DSPC/cholesterol/Gd-DOTA-DSPE/DOTA-DSPE with the molar ratio of 39:35:25:1 and having ammonium sulfate/pH gradient. A lipidized NIR fluorescent tracer, IRDye-DSPE, was effectively postinserted into the premanufactured liposomes. Doxorubicin could be effectively postloaded into the multifunctional liposomes. The multifunctional doxorubicin-liposomes could also be stably radiolabeled with (99m)Tc or (64)Cu for single-photon emission computed tomography (SPECT) or positron emission tomography (PET) imaging, respectively. MR images displayed the high-resolution micro-intratumoral distribution of the liposomes in squamous cell carcinoma of head and neck (SCCHN) tumor xenografts in nude rats after intratumoral injection. NIR fluorescent, SPECT, and PET images also clearly showed either the high intratumoral retention or distribution of the multifunctional liposomes. This multifunctional drug carrying liposome system is promising for disease theranostics allowing noninvasive multimodality NIR fluorescent, MR, SPECT, and PET imaging of their in vivo behavior and capitalizing on the inherent advantages of each modality.

Medicinal chemistry based approaches and nanotechnology-based systems to improve CNS drug targeting and delivery

The central nervous system (CNS) is protected by various barriers, which regulate nervous tissue homeostasis and control the selective and specific uptake, efflux, and metabolism of endogenous and exogenous molecules. Among these barriers is the blood-brain barrier (BBB), a physical and physiological barrier that filters very efficiently and selectively the entry of compounds from the blood to the brain and protects nervous tissue from harmful substances and infectious agents present in the bloodstream. The BBB also prevents the entry of potential drugs. As a result, various drug targeting and delivery strategies are currently being developed to enhance the transport of drugs from the blood to the brain. Following a general introduction, we briefly overview in this review article the fundamental physiological properties of the BBB. Then, we describe current strategies to bypass the BBB (i.e., invasive methods, alternative approaches, and temporary opening) and to cross it (i.e., noninvasive approaches). This section is followed by a chapter addressing the chemical and technological solutions developed to cross the BBB. A special emphasis is given to prodrug-targeting approaches and targeted nanotechnology-based systems, two promising strategies for BBB targeting and delivery of drugs to the brain.

Advancement in multifunctional nanoparticles for the effective treatment of cancer

INTRODUCTION

Nanotechnology has gained wider importance for the treatment of various diseases, including cancer. Multifunctional or theranostic agents are emerging as promising therapeutic paradigms, which provide attractive vehicles for both image and therapeutic agents. Nanosystems are capable of diagnosis, specific targeted drug therapy and monitoring therapeutic response. Due to their well-developed surface nature, nanomolecules are easy to anchor with multifunctional groups.

AREAS COVERED

The present review aims to give an extensive account on the progress of multifunctional nanoparticles throughout the blooming research with regards to their clinical application in cancer. This paper discusses graphene, a newly developed multifunctional vehicle in nanotechnology. Furthermore, it focuses on the development of tumor cells, the advantages of novel multifunctional nanoparticles over traditional methods and the use of nanoparticles in cancer therapy. In addition, patents issued by the US office are also included.

EXPERT OPINION

Despite numerous advantages, multifunctional nanoparticles are still at an infancy stage. Many great achievements have been attained in this field to date, but many challenges still remain. A problem that limits the use of multifunctional nanoparticles is toxicity. If this toxicity can be overcome then the advancement in nanocomposite material science will be well on the way to a prospective treatment of cancer.

Advances in MRI-Based Detection of Cerebrovascular Changes after Experimental Traumatic Brain Injury

Traumatic brain injury is a heterogeneous and multifaceted neurological disorder that involves diverse pathophysiological pathways and mechanisms. Thorough characterization and monitoring of the brain’s status after neurotrauma is therefore highly complicated. Magnetic resonance imaging (MRI) provides a versatile tool for in vivo spatiotemporal assessment of various aspects of central nervous system injury, such as edema formation, perfusion disturbances and structural tissue damage. Moreover, recent advances in MRI methods that make use of contrast agents have opened up additional opportunities for measurement of events at the level of the cerebrovasculature, such as blood–brain barrier permeability, leukocyte infiltration, cell adhesion molecule upregulation and vascular remodeling. It is becoming increasingly clear that these cerebrovascular alterations play a significant role in the progression of post-traumatic brain injury as well as in the process of post-traumatic brain repair. Application of advanced multiparametric MRI strategies in experimental, preclinical studies may significantly aid in the elucidation of pathomechanisms, monitoring of treatment effects, and identification of predictive markers after traumatic brain injury.

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

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

Highly biocompatible TiO₂:Gd³⁺ nano-contrast agent with enhanced longitudinal relaxivity for targeted cancer imaging

We report the development of a novel magnetic nano-contrast agent (nano-CA) based on Gd(3+) doped amorphous TiO(2) of size ∼25 nm, exhibiting enhanced longitudinal relaxivity (r(1)) and magnetic resonance (MR) contrasting together with excellent biocompatibility. Quantitative T1 mapping of phantom samples using a 1.5 T clinical MR imaging system revealed that the amorphous phase of doped titania has the highest r(1) relaxivity which is ∼2.5 fold higher than the commercially used CA Magnevist™. The crystalline (anatase) samples formed by air annealing at 250 °C and 500 °C showed significant reduction in r(1) values and MR contrast, which is attributed to the loss of proton-exchange contribution from the adsorbed water and atomic re-arrangement of Gd(3+) ions in the crystalline host lattice. Nanotoxicity studies including cell viability, plasma membrane integrity, reactive oxygen stress and expression of pro-inflammatory cytokines, performed on human primary endothelial cells (HUVEC), human blood derived peripheral blood mononuclear cells (PBMC) and nasopharyngeal epidermoid carcinoma (KB) cell line showed excellent biocompatibility up to relatively higher doses of 200 μg ml(-1). The potential of this nano-CA to cause hemolysis, platelet aggregation and plasma coagulation were studied using human peripheral blood samples and found no adverse effects, illustrating the possibility of the safe intravenous administration of these agents for human applications. Furthermore, the ability of these agents to specifically detect cancer cells by targeting molecular receptors on the cell membrane was demonstrated on folate receptor (FR) positive oral carcinoma (KB) cells, where the folic acid conjugated nano-CA showed receptor specific accumulation on cell membrane while leaving the normal fibroblast cells (L929) unstained. This study reveals that the Gd(3+) doped amorphous TiO(2) nanoparticles having enhanced magnetic resonance contrast and high biocompatibility is a promising candidate for molecular receptor targeted MR imaging.

Inorganic nanoparticle-based contrast agents for molecular imaging

Inorganic nanoparticles (NPs) including semiconductor quantum dots (QDs), iron oxide NPs and gold NPs have been developed as contrast agents for diagnostics by molecular imaging. Compared with traditional contrast agents, NPs offer several advantages: their optical and magnetic properties can be tailored by engineering the composition, structure, size and shape; their surfaces can be modified with ligands to target specific biomarkers of disease; the contrast enhancement provided can be equivalent to millions of molecular counterparts; and they can be integrated with a combination of different functions for multimodal imaging. Here, we review recent advances in the development of contrast agents based on inorganic NPs for molecular imaging, and also touch on contrast enhancement, surface modification, tissue targeting, clearance and toxicity. As research efforts intensify, contrast agents based on inorganic NPs that are highly sensitive, target-specific and safe to use are expected to enter clinical applications in the near future.

In vivo near-infrared fluorescence imaging of cancer with nanoparticle-based probes

The use of in vivo near-infrared fluorescence (NIRF) imaging techniques for sensitive cancer early detection is highly desirable, because biological tissues show very low absorption and autofluorescence in the NIR spectrum window. Cancer NIRF molecular imaging relies greatly on stable, highly specific and sensitive molecular probes. Nanoparticle-based NIRF probes have overcome some of the limitations of the conventional NIRF organic dyes, such as poor hydrophilicity and photostability, low quantum yield, insufficient stability in biological system, low detection sensitivity, etc. Therefore, a lot of efforts have been made to actively develop novel NIRF nanoparticles for in vivo cancer molecular imaging. The main focus of this article is to provide a brief overview of the synthesis, surface modification, and in vivo cancer imaging applications of nanoparticle-based NIRF probes, including dye-containing nanoparticles, NIRF quantum dots, and upconversion nanoparticles.

Engineering biofunctional magnetic nanoparticles for biotechnological applications

Synthesis and characterization of magnetic nanoparticles with excellent size control are showed here. Their functionalization using an amphiphilic polymer is also described. This strategy allows the stabilization of magnetic nanoparticles in aqueous solvents and in addition, the polymer shell serves as a platform to incorporate relevant biomolecules, such as poly(ethylene glycol) and a number of carbohydrates. Nanoparticles functionalized with carbohydrates show the ability to avoid unspecific interactions between proteins present in the working medium and the nanoparticles, so can be used as an alternative to poly(ethylene glycol) molecules. Results confirm these nanoparticles as excellent contrast agents for magnetic resonance imaging. Changes in the spin-spin transversal relaxation times of the surrounding water protons due to nanoparticle aggregation demonstrates the bioactivity of these nanoparticles functionalized with carbohydrates. To finish with, nanoparticle toxicity is evaluated by means of MTT assay. The obtained results clearly indicate that these nanoparticles are excellent candidates for their further application in nanomedicine or nanobiotechnology.

Nanoparticle-based theranostic agents

Theranostic nanomedicine is emerging as a promising therapeutic paradigm. It takes advantage of the high capacity of nanoplatforms to ferry cargo and loads onto them both imaging and therapeutic functions. The resulting nanosystems, capable of diagnosis, drug delivery and monitoring of therapeutic response, are expected to play a significant role in the dawning era of personalized medicine, and much research effort has been devoted toward that goal. A convenience in constructing such function-integrated agents is that many nanoplatforms are already, themselves, imaging agents. Their well-developed surface chemistry makes it easy to load them with pharmaceutics and promote them to be theranostic nanosystems. Iron oxide nanoparticles, quantum dots, carbon nanotubes, gold nanoparticles and silica nanoparticles, have been previously well investigated in the imaging setting and are candidate nanoplatforms for building up nanoparticle-based theranostics. In the current article, we will outline the progress along this line, organized by the category of the core materials. We will focus on construction strategies and will discuss the challenges and opportunities associated with this emerging technology.

Molecular imaging with contrast enhanced ultrasound

Noninvasive cardiovascular imaging techniques are well-established for studying cardiovascular anatomy and physiology. Over the past decade contrast enhanced imaging techniques have been developed that are also able to characterize the molecular constituents of cardiovascular disease. In this regard, microbubble- and ultrasound-based techniques have the ability to assess a broad range of molecular components of cardiovascular pathology such as inflammation, recent ischemia, atherosclerosis, acute transplant rejection, angiogenesis, and thrombosis. The advantages of ultrasound- and microbubble-based approach include the ability to assess multiple molecular disease markers without exposure to ionizing radiation or prolonged imaging protocols. This review highlights the development of microbubble-based molecular imaging, describes successful experimental conditions in which they have been studied, and postulates the importance of translating this technique into the clinical practice.

Biomimetic MRI contrast agent for imaging of inflammation in atherosclerotic plaque of ApoE-/- mice: a pilot study

OBJECTIVE

Atherosclerosis involves an inflammatory process characterized by cellular and molecular responses. A slow-clearance blood-pool paramagnetic agent (CMD-A2-Gd-DOTA: P717) chemically modified to create a functionalized product (F-P717) for targeting inflammation in vessel walls was evaluated in vivo in mice.

METHODS AND RESULTS

Carboxylate and sulfate groups were grafted onto the macromolecular paramagnetic Gd-DOTA-dextran backbone. Products were also fluorescently labeled with rhodamine isothiocyanate. Pre- and postcontrast MRI was performed on a 2-Tesla magnet in ApoE-/- and control C57BL/6 mice after P717 or F-P717 injection at a dose of 60 micromol Gd/kg. Axial T1-weighted images of the abdominal aorta were obtained using a 2D multislice spin-echo sequence. F-P717 significantly enhanced the magnetic resonance imaging (MRI) signal in the abdominal aortic wall of ApoE-/- mice (>50% signal-to-noise ratio increase between 10 and 30 minutes), but not of control mice. P717 produced only moderate (<20%) MRI signal enhancement within the same time frame. The MRI data were correlated to histopathology. Immunofluorescence in ApoE-/- mice colocalized F-P717 but not P717 with the inflammatory area revealed by P-selectin labeling.

CONCLUSION

This study demonstrates the efficacy of F-P717 as a new molecular imaging agent for noninvasive in vivo MRI location of inflammatory vascular tree lesions in ApoE-/- mice.

Multifunctional Polymeric Scaffolds for Enhancement of PARACEST Contrast Sensitivity and Performance: The Effects of Random Copolymer Variations

A DOTA (1,4,7,10-tetraazacyclododecane-N,N',N",N'"-tetraacetic acid) tetraamide ligand having a single acrylamide side-chain (M1) was copolymerized with either 2-methylacrylic acid (MAA), 2-(acryloylamino)-2-methyl-1-propanesulfonic acid (AMPS) or N-isopropylacrylamide (NIPAM) to create a series of linear random copolymers using classical free radical chain polymerization chemistry. The metal ion binding properties of hydrolyzed M1 were investigated by pH potentiometry and the europium (III) complexes of the resulting heteropolymers were evaluated as PARACEST imaging agents. All polymeric agents were found to possess similar intermediate-to-slow water exchange and CEST characteristics as the parent EuDOTA-tetraamide monomer. Consistent with basic multiplexing principles, the highest molecular weight polymer, Eu-DMAA 3.1, also showed the highest CEST sensitivity with a detection limit of 20 ± 2 μM. The second arylamide component gave polymers with widely different chemical characteristics and CEST properties. In particular, the Eu-DNIPAM 4.0 and Eu-DMAA 4.1 polymers displayed different solubility characteristics as a function of pH or temperature which, in turn, affected the water exchange and CEST properties of the corresponding agents. It was concluded that introduction of hydrophobic groups into the polymer backbone reduces solvent accessibility to the Eu(3+) component, effectively slowing water exchange between the inner-sphere water coordination position at each Eu(3+) center with bulk water. The CEST properties of the heteropolymers when dissolved in plasma suggest that the more hydrophobic characteristics of these polymers could be advantageous for in vivo applications.

Liver and brain imaging through dimercaptosuccinic acid-coated iron oxide nanoparticles

BACKGROUND & AIM

Uptake, cytotoxicity and interaction of improved superparamagnetic iron oxide nanoparticles were studied in cells, tissues and organs after single and multiple exposures.

MATERIAL & METHOD

We prepared dimercaptosuccinic acid-coated iron oxide nanoparticles by thermal decomposition in organic medium, resulting in aqueous suspensions with a small hydrodynamic size (< 100 nm), high saturation magnetization and susceptibility, high nuclear magnetic resonance contrast and low cytotoxicity.

RESULTS

In vitro and in vivo behavior showed that these nanoparticles are efficient carriers for drug delivery to the liver and brain that can be combined with MRI detection.

Gadolinium hexanedione nanoparticles for stem cell labeling and tracking via magnetic resonance imaging

The ability to trace transplanted stem cells and monitor their tissue biodistribution is prerequisite to an understanding of cellular migration after transplantation. Therefore, a new magnetic resonance imaging (MRI) contrast agent made of gadolinium hexanedione nanoparticles (GdH-NPs) was developed as a cell tracking agent. The GdH-NPs were fabricated by the microemulsion process. The physical characteristics, biocompatibility, and T1-MRI signal enhancement of these NPs were analyzed and evaluated for stem cell tracking. In this study, the size of the synthesized GdH-NPs was about 140 nm, and it had greater image enhancement ability than commercial gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA). From the biocompability test, we found GdH-NPs were nontoxic for human mesenchymal stem cells (hMSCs). The expression of surface antigens of hMSCs after culture with GdH-NPs was examined, and it showed no difference from the control group. The results of transmission electron microscopy (TEM) imaging for labeled hMSCs showed GdH-NPs were accumulated in the cells by the endocytotic pathway. The accumulation of GdH-NPs in hMSCs was three times higher in comparison to Gd-DTPA. Human MSCs labeled with low concentration of GdH-NPs (10 microg/mL) hold better signals in cellular MR image. We conclude GdH-NPs can be used to label hMSCs in vitro with greater T1 image-enhancing property and without affecting cell quality. Finally, GdH-NPs have great potential as a contrast agent for stem cell tracking by MRI methodology.

Magnetic resonance molecular imaging of post-stroke neuroinflammation with a P-selectin targeted iron oxide nanoparticle

We have developed a magnetic resonance molecular imaging method using a novel iron-oxide contrast agent targeted towards P-selectin - MNP-PBP (magnetic nanoparticle-P-selectin binding peptide) - to image endothelial activation following cerebral ischemia/reperfusion. MNP-PBP consists of approximately 1000 PBP ligands (primary sequence: GSIQPRPQIHNDGDFEEIPEEYLQ GGSSLVSVLDLEPLDAAWL) conjugated to a 50 nm diameter aminated dextran iron oxide particle. In vitro P- and E-selectin binding was assessed by competition ELISA. Transient focal cerebral ischemia was induced in male C57/BL 6 mice followed by contrast injection (MNP-PBP; MNP-NH2; Feridex; MNP-PBP-FITC) at 24 h after reperfusion and T(2) magnetic resonance imaging at 9.4 T was performed. Infarction and microvasculature accumulation of contrast agent was assessed in coronal brain sections. MNP-PBP attenuated antibody binding to P-selectin by 34.8 +/- 1.7%. P-selectin was preferentially increased in the infarct hemisphere and MNP-PBP-FITC accumulation in the infarct hemisphere microvasculature was observed. Compared with the nontargeted iron oxide agents MNP-NH2 and Feridex, MNP-PBP showed a significantly greater T(2) effect within the infarction. MR imaging of P-selectin expression with a targeted iron oxide nanoparticle contrast agent may reveal early endothelial activation in stroke and other neuroinflammatory states.

Anti-angiogenic perfluorocarbon nanoparticles for diagnosis and treatment of atherosclerosis

Complementary developments in nanotechnology, genomics, proteomics, molecular biology and imaging offer the potential for early, accurate diagnosis. Molecularly-targeted diagnostic imaging agents will allow noninvasive phenotypic characterization of pathologies and, therefore, tailored treatment close to the onset. For atherosclerosis, this includes anti-angiogenic therapy with specifically-targeted drug delivery systems to arrest the development of plaques before they impinge upon the lumen. Additionally, monitoring the application and effects of this targeted therapy in a serial fashion will be important. This review covers the specific application of alpha(nu)beta(3)-targeted anti-angiogenic perfluorocarbon nanoparticles in (1) the detection of molecular markers for atherosclerosis, (2) the immediate verification of drug delivery with image-based prediction of therapy outcomes, and (3) the serial, noninvasive observation of therapeutic efficacy.

Nanoparticle phagocytosis and cellular stress: involvement in cellular imaging and in gene therapy against glioma

In gene therapy against glioma, targeting tumoral tissue is not an easy task. We used the tumor infiltrating property of microglia in this study. These cells are well adapted to this therapy since they can phagocyte nanoparticles and allow their visualization by MRI. Indeed, while many studies have used transfected microglia containing a suicide gene and other internalized nanoparticles to visualize microglia, none have combined both approaches during gene therapy. Microglia cells were transfected with the TK-GFP gene under the control of the HSP(70) promoter. First, the possible cellular stress induced by nanoparticle internalization was checked to avoid a non-specific activation of the suicide gene. Then, MR images were obtained on tubes containing microglia loaded with superparamagnetic nanoparticles (VUSPIO) to characterize their MR properties, as well as their potential to track cells in vivo. VUSPIO were efficiently internalized by microglia, were found non-toxic and their internalization did not induce any cellular stress. VUSPIO relaxivity r(2) was 224 mM(-1).s(-1). Such results could generate a very high contrast between loaded and unloaded cells on T(2)-weighted images. The intracellular presence of VUSPIO does not prevent suicide gene activity, since TK is expressed in vitro and functional in vivo. It allows MRI detection of gene modified macrophages during cell therapy strategies.