Theragnostics for tumor and plaque angiogenesis with perfluorocarbon nanoemulsions

Dual-drug loaded ultrasound-responsive nanodroplets for on-demand combination chemotherapy

Phase-changing nanodroplets are nanometric sized constructs that can be vaporized via external stimuli, such as focused ultrasound, to generate gaseous bubbles that are visible in ultrasound. Their activation can also be leveraged to release their payload, creating a method for ultrasound-modulated localized drug delivery. Here, we develop a perfluoropentane core nanodroplet that can simultaneously load paclitaxel and doxorubicin, and release them in response to an acoustic trigger. A double emulsion method is used to incorporate the two drugs with different physio-chemical properties, which allows for a combinatorial chemotherapy regimen to be used. Their loading, release, and biological effects on a triple negative breast cancer mouse model are investigated. We show that activation enhances the drug-delivery effect and delays the tumor growth rate in vivo. Overall, the phase-changing nanodroplets are a useful platform to allow on-demand delivery of combinations of drugs.

Single low-dose INC280-loaded theranostic nanoparticles achieve multirooted delivery for MET-targeted primary and liver metastatic NSCLC

BACKGROUND

Non-small cell lung cancer (NSCLC) patients with primary tumors and liver metastases have substantially reduced survival. Since mesenchymal-epithelial transition factor (MET) plays a significant role in the molecular mechanisms of advanced NSCLC, small molecule MET inhibitor capmatinib (INC280) hold promise for clinically NSCLC treatment. However, the major obstacles of MET-targeted therapy are poor drug solubility and off-tumor effects, even oral high-dosing regimens cannot significantly increase the therapeutic drug concentration in primary and metastatic NSCLC.

METHODS

We developed a multirooted delivery system INC280-PFCE nanoparticles (NPs) by loading INC280 into perfluoro-15-crown-5-ether for improving MET-targeted therapy. Biodistribution and anti-MET/antimetastatic effects of NPs were validated in orthotopic NSCLC and NSCLC liver metastasis models in a single low-dose. The efficacy of INC280-PFCE NPs was also explored in human NSCLC specimens.

RESULTS

INC280-PFCE NPs exhibited excellent antitumor ability in vitro. In orthotopic NSCLC models, sustained release and prolonged retention behaviors of INC280-PFCE NPs within tumors could be visualized in real-time by ¹⁹F magnetic resonance imaging (¹⁹F-MRI), and single pulmonary administration of NPs showed more significant tumor growth inhibition than oral administration of free INC280 at a tenfold higher dose. Furthermore, a single low-dose INC280-PFCE NPs administered intravenously suppressed widespread dissemination of liver metastasis without systemic toxicity. Finally, we verified the clinical translation potential of INC280-PFCE NPs in human NSCLC specimens.

CONCLUSIONS

These results demonstrated high anti-MET/antimetastatic efficacies, real-time MRI visualization and high biocompatibility of NPs after a single low-dose.

Recent Advances in Functionalized Nanoparticles in Cancer Theranostics

Cancer theranostics is the combination of diagnosis and therapeutic approaches for cancer, which is essential in personalized cancer treatment. The aims of the theranostics application of nanoparticles in cancer detection and therapy are to reduce delays in treatment and hence improve patient care. Recently, it has been found that the functionalization of nanoparticles can improve the efficiency, performance, specificity and sensitivity of the structure, and increase stability in the body and acidic environment. Moreover, functionalized nanoparticles have been found to possess a remarkable theranostic ability and have revolutionized cancer treatment. Each cancer treatment modality, such as MRI-guided gene therapy, MRI-guided thermal therapy, magnetic hyperthermia treatment, MRI-guided chemotherapy, immunotherapy, photothermal and photodynamic therapy, has its strengths and weaknesses, and combining modalities allows for a better platform for improved cancer control. This is why cancer theranostics have been investigated thoroughly in recent years and enabled by functionalized nanoparticles. In this topical review, we look at the recent advances in cancer theranostics using functionalized nanoparticles. Through understanding and updating the development of nanoparticle-based cancer theranostics, we find out the future challenges and perspectives in this novel type of cancer treatment.

Orthogonal targeting of osteoclasts and myeloma cells for radionuclide stimulated dynamic therapy induces multidimensional cell death pathways

Rationale: Multiple myeloma (MM) is a multifocal malignancy of bone marrow plasma cells, characterized by vicious cycles of remission and relapse that eventually culminate in death. The disease remains mostly incurable largely due to the complex interactions between the bone microenvironment (BME) and MM cells (MMC). In the “vicious cycle” of bone disease, abnormal activation of osteoclasts (OCs) by MMC causes severe osteolysis, promotes immune evasion, and stimulates the growth of MMC. Disrupting these cancer-stroma interactions would enhance treatment response.

Methods: To disrupt this cycle, we orthogonally targeted nanomicelles (NM) loaded with non-therapeutic doses of a photosensitizer, titanocene (TC), to VLA-4 (α4ß1, CD49d/CD29) expressing MMC (MM1.S) and αvß3 (CD51/CD61) expressing OC. Concurrently, a non-lethal dose of a radiopharmaceutical, ¹⁸F-fluorodeoxyglucose ([¹⁸F]FDG) administered systemically interacted with TC (radionuclide stimulated therapy, RaST) to generate cytotoxic reactive oxygen species (ROS). The in vitro and in vivo effects of RaST were characterized in MM1.S cell line, as well as in xenograft and isograft MM animal models.

Results: Our data revealed that RaST induced non-enzymatic hydroperoxidation of cellular lipids culminating in mitochondrial dysfunction, DNA fragmentation, and caspase-dependent apoptosis of MMC using VLA-4 avid TC-NMs. RaST upregulated the expression of BAX, Bcl-2, and p53, highlighting the induction of apoptosis via the BAK-independent pathway. The enhancement of multicopper oxidase enzyme F5 expression, which inhibits lipid hydroperoxidation and Fenton reaction, was not sufficient to overcome RaST-induced increase in the accumulation of irreversible function-perturbing α,ß-aldehydes that exerted significant and long-lasting damage to both DNA and proteins. In vivo, either VLA-4-TC-NM or αvß3-TC-NMs RaST induced a significant therapeutic effect on immunocompromised but not immunocompetent MM-bearing mouse models. Combined treatment with both VLA-4-TC-NM and αvß3-TC-NMs synergistically inhibited osteolysis, reduced tumor burden, and prevented rapid relapse in both in vivo models of MM.

Conclusions: By targeting MM and bone cells simultaneously, combination RaST suppressed MM disease progression through a multi-prong action on the vicious cycle of bone cancer. Instead of using the standard multidrug approach, our work reveals a unique photophysical treatment paradigm that uses nontoxic doses of a single light-sensitive drug directed orthogonally to cancer and bone cells, followed by radionuclide-stimulated generation of ROS to inhibit tumor progression and minimize osteolysis in both immunocompetent murine and immunocompromised human MM models.

Nanotechnology in Oral Cancer Prevention and Therapeutics: A Literature Review

The concept of nanotechnology revolves around the delivery of nano particle incorporated drugs which are originally engineered technology. Nanoparticles are used for targeted delivery and controlled release of a curative agents. Nanotechnology is gaining importance and is likely to be routine element of regular dental clinics. Nanomaterials are being incorporated in toothpastes, mouth rinses for improved efficiencies. It has found its use in restorative dental materials, anti-cariogenic enamel surface polishing agents, implant materials, etc. Few nanoparticles possess antimicrobial propertiesand intercepts bacterial activity. Nano dentistry is cost-effectiveness and timesaving compared to other techniques. Nano particles have also been beneficial to annihilate drug resistance, prevention of metastasis or lesion recurrence by earmarking malignant stem cells. Remarkable achievements were made in using nanoparticles for detecting and treating multiple variety of malignancies including colon cancer, prostate cancer, lung cancer, breast cancer, head and neck cancer, etc. This review was made to highlight the various clinical applications of nanotechnology in the diagnosis and curative care for oral cancer.

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.

Theranostic application of nanoemulsions in chemotherapy

Theranostics has the potential to revolutionize the diagnosis, treatment, and prognosis of cancer, where novel drug delivery systems could be used to detect the disease at an early stage with instantaneous treatment. Various preclinical approaches of nanoemulsions with entrapped contrast and chemotherapeutic agents have been documented to act specifically on the tumor microenvironment (TME) for both diagnostic and therapeutic purposes. However, bringing these theranostic nanoemulsions through preclinical trials to patients requires several fundamental hurdles to be overcome, including the in vivo behavior of the delivery tool, degradation, and clearance from the system, as well as long-term toxicities. Here, we discuss recent advances in the application of nanoemulsions in molecular imaging with simultaneous therapeutic efficacy in a single delivery system.

Inhibition of snake venom induced sterile inflammation and PLA2 activity by Titanium dioxide Nanoparticles in experimental animals

Sterile inflammation (SI) is an essential process in response to snakebite and injury. The venom induced pathophysiological response to sterile inflammation results into many harmful and deleterious effects that ultimately leads to death. The available treatment for snakebite is antiserum which does not provide enough protection against venom-induced pathophysiological changes like haemorrhage, necrosis, nephrotoxicity and often develop hypersensitive reactions. In order to overcome these hindrances, scientists around the globe are searching for an alternative therapy to provide better treatment to the snake envenomation patients. In the present study TiO₂ (Titanium dioxide)-NPs (Nanoparticles) has been assessed for antisnake venom activity and its potential to be used as an antidote. In this study, the synthesis of TiO₂-NPs arrays has been demonstrated on p-type Silicon Si < 100 > substrate (∼30 ohm-cm) and the surface topography has been detected by Field-emission scanning electron microscopy (FESEM). The TiO₂-NPs successfully neutralized the Daboia russelii venom (DRV) and Naja kaouthia venom (NKV)-induced lethal activity. Viper venom induced haemorrhagic, coagulant and anticoagulant activities were effectively neutralized both in in-vitro and in vivo studies. The cobra and viper venoms-induced sterile inflammatory molecules (IL-6, HMGB1, HSP70, HSP90, S100B and vWF) were effectively neutralised by the TiO₂-NPs in experimental animals.

Multiple linear regression applied to predicting droplet size of complex perfluorocarbon nanoemulsions for biomedical applications

Multiple linear regression (MLR) modeling as a novel methodological advancement for design, development, and optimization of perfluorocarbon nanoemulsions (PFC NEs) is presented. The goal of the presented work is to develop MLR methods applicable to design, development, and optimization of PFC NEs in broad range of biomedical uses. Depending on the intended use of PFC NEs as either therapeutics or diagnostics, NE composition differs in respect to specific applications (e.g. magnetic resonance imaging, drug delivery, etc). PFC NE composition can significantly impact on PFC NE droplet size which impacts the NE performance and quality. We demonstrated earlier that microfluidization combined with sonication produces stable emulsions with high level of reproducibility. The goal of the presented work was to establish correlation between droplet size and composition in complex PFC-in-oil-in-water NEs while manufacturing process parameters are kept constant. Under these conditions, we demonstrate that MLR model can predict droplet size based on formulation variables such as amount and type of PFC oil and hydrocarbon oil. To the best of our knowledge, this is the first report where PFC NE composition was directly related to its colloidal properties and MLR used to predict colloidal properties from composition variables.

Nanoemulsions in drug delivery: formulation to medical application

Nanoscale oil-in-water emulsions (NEs), heterogeneous systems of two immiscible liquids stabilized by emulsifiers or surfactants, show great potential in medical applications because of their attractive characteristics for drug delivery. NEs have been explored as therapeutic carriers for hydrophobic compounds via various routes of administration. NEs provide opportunities to improve drug delivery via alternative administration routes. However, deep understanding of the NE manufacturing and functionalization fundamentals, and how they relate to the choice of administration route and pharmacological profile is still needed to ease the clinical translation of NEs. Here, we review the diversity of medical applications for NEs and how that governs their formulation, route of administration, and the emergence of increasing sophistication in NE design for specific application.

Molecular oxygen loading in candidate theranostic droplets stabilized with biocompatible fluorinated surfactants: Particle size effect and application to in situ19F MRI mapping of oxygen partial pressure

OBJECTIVE

Perfluorocarbon nano- and micron-sized emulsions are a new field of investigation in cancer treatment due to their ability to be used as imaging contrast agents, or as delivery vectors for pharmaceuticals. They also demonstrated capability to enhance the efficiency of high intensity focused ultrasound thermo-therapy. In the context of new biomedical applications we investigated perfluorooctyl bromide (PFOB) theranostic droplets using ¹⁹F NMR. Each droplet contains biocompatible fluorinated surfactants composed of a polar Tris(hydroxymethyl)aminomethane head unit and hydrophobic perfluorinated tail (abbreviated as F-TAC). The influence of the droplet size on the oxygen loading capacity was determined from longitudinal relaxation (T₁) data of ¹⁹F NMR signal.

MATERIAL AND METHODS

Liquid PFOB and five samples of PFOB droplets of average diameter 0.177, 0.259, 1.43, 3.12 and 4.53 µm were tested with different oxygen levels. A dedicated gas exchange system was validated to maintain steady state oxygen concentrations, including a spatial gradient of oxygen concentration. A prototyped transmit-receive switchable ¹⁹F/¹H quadrature coil was integrated on a 3 T clinical scanner. The coil is compatible with focused ultrasound sonication for future application. A spectroscopy FID inversion-recovery (IR) sequence was used to measure the T₁ value per sample and per value of equilibrium oxygen pressure. Pixel wise, spatial T₁ mapping was performed with magnetization prepared 2D gradient echo sequences in tissue mimicking gels doped with theranostic droplets.

RESULTS

Experimental data indicated that the longitudinal relaxation rate of ¹⁹F signal of the investigated theranostic droplets depended approximately linearly on the oxygen level and its slope decreased with the particle size according to a second order polynomial over the investigated range. This semi-empirical model was derived from general thermodynamics and weak electrostatic forces theory and fitted the experimental data within 0.75% precision. The capacity of oxygen transportation for the described theranostic droplets tended to that of pure PFOB, while micron-sized droplets lost up to 50% of this capacity. In a specific setup producing a steady state gradient of oxygen concentration, we demonstrated spatial mapping of oxygen pressure gradient of 6 kPa/mm with 1 mm in-plane resolution.

CONCLUSION

The size-tunable PFOB theranostic droplets stabilized with F-TAC surfactants could be characterized by ¹⁹F MRI in a clinical setup readily compatible with interventional in vivo studies under MR guidance. Current precision and spatial resolution of T₁ mapping are promising. A potential challenge for further in vivo studies is the reduction of the imaging time.

Phosphatidylserine-Targeted Nanotheranostics for Brain Tumor Imaging and Therapeutic Potential

Phosphatidylserine (PS), the most abundant anionic phospholipid in cell membrane, is strictly confined to the inner leaflet in normal cells. However, this PS asymmetry is found disruptive in many tumor vascular endothelial cells. We discuss the underlying mechanisms for PS asymmetry maintenance in normal cells and its loss in tumor cells. The specificity of PS exposure in tumor vasculature but not normal blood vessels may establish it a useful biomarker for cancer molecular imaging. Indeed, utilizing PS-targeting antibodies, multiple imaging probes have been developed and multimodal imaging data have shown their high tumor-selective targeting in various cancers. There is a critical need for improved diagnosis and therapy for brain tumors. We have recently established PS-targeted nanoplatforms, aiming to enhance delivery of imaging contrast agents across the blood-brain barrier to facilitate imaging of brain tumors. Advantages of using the nanodelivery system, in particular, lipid-based nanocarriers, are discussed here. We also describe our recent research interest in developing PS-targeted nanotheranostics for potential image-guided drug delivery to treat brain tumors.

Multicompartment Theranostic Nanoemulsions Stabilized by a Triphilic Semifluorinated Block Copolymer

The presence of a perfluorocarbon block in a multiblock polymer has been shown to be an additional driving force toward nanoparticle assembly. In the preparation of nanoemulsions, this perfluorocarbon block also provides enhanced particle stability. Herein, the synthesis of a new triphilic, semifluorinated copolymer, M2F8H18, is introduced. This ABC type block copolymer can be used to formulate extremely stable nanoemulsions, assembled around a lipophilic droplet, with lifetimes of one year or more. The central oil droplet can stably solubilize high concentrations of hydrophobic drugs, making this system an ideal drug delivery vehicle. The incorporation of the perfluorocarbon block modulates drug release from the lipophilic core via the surrounding fluorous shell. Fluorous imaging agents incorporated into the fluorous shell prolong drug release even further as well as provide potent ¹⁹F-MRI contrast ability. In vitro studies show that these nanoemulsions efficiently inhibit cancer cell growth, thus providing a theranostic drug delivery system.

Nano-sized and other improved reporters for magnetic resonance imaging of angiogenesis

Magnetic Resonance Imaging (MRI) enables to provide anatomical, functional and molecular information of pathological angiogenesis when used with properly tailored imaging probes. Functional studies have been the domain of Dynamic Contrast Enhancement (DCE) -MRI protocols from which it is possible to extract quantitative estimations on key parameters such as the volumes of vascular and extracellular compartments and the rates of the bidirectional exchange of the imaging reporters across the endothelial barrier. Whereas paramagnetic Gd-complexes able to reversibly bind to serum albumin act better than the clinically used small-sized, hydrophilic species, new findings suggest that an accurate assessment of the vascular volume is possible by analyzing images acquired upon the i.v. administration of Gd-labelled Red Blood Cells (RBCs). As far as it concerns molecular MRI, among the many available biomarkers, α_vβ₃ integrins are the most investigated ones. The low expression of these targets makes mandatory the use of nano-sized systems endowed with the proper signal enhancing capabilities. A number of targeted nano-particles have been investigated including micelles, liposomes, iron oxides and perfluorocarbon containing systems. Finally, a growing attention is devoted to the design and testing of "theranostic" agents based on the exploitation of MRI to monitor drug delivery processes and therapeutic outcome.

Iron oxide core oil-in-water nanoemulsion as tracer for atherosclerosis MPI and MRI imaging

PURPOSE

For early atherosclerosis imaging, magnetic oil-in-water nanoemulsion (NE) decorated with atheroma specific monoclonal antibody was designed for Magnetic Particle Imaging (MPI) and Magnetic Resonance Imaging (MRI). MPI is an emerging technique based on direct mapping of superparamagnetic nanoparticles which may advantageously complement MRI.

METHODS

NE oily droplets were loaded with superparamagnetic iron oxide nanoparticles of 7, 11 and 18nm and biofunctionalized with atheroma specific scFv-Fc TEG4-2C antibody.

RESULTS

Inclusion of nanoparticles inside NE did not change the hydrodynamic diameter of the oil droplets, close to 180nm, nor the polydispersity. The droplets were negatively charged (ζ=-30mV). In vitro MPI signal was assessed by Magnetic Particle Spectroscopy (MPS). NE displayed MRI and MPS signals confirming its potential as new contrast agent. NE MPS signal increase with NPs size close to the gold standard (Resovist). In MRI, NE displayed R₂* transversal relaxivity of 45.45, 96.04 and 218.81mM^-1s^-1 for 7, 11 and 18nm respectively. NE selectively bind atheroma plaque both in vitro and ex vivo in animal models of atherosclerosis.

CONCLUSION

Magnetic NE showed reasonable MRI/MPS signals and a significant labelling of the atheroma plaque. These preliminary results support that NE platform could selectively image atherosclerosis.

Antimicrobial Nanostructures for Neurodegenerative Infections

Nanostructures have been widely involved in changes in the drug delivery system. Nanoparticles have unique physicochemical properties, e.g., ultrasmall size, large surface area, and the ability to target specific actions. Various nanomaterials, like Ag, ZnO, Cu/CuO, and Al₂O₃, have antimicrobial activity. Basically, six mechanisms are involved in the production of antimicrobial activity, i.e., (1) destruction of the peptidoglycan layer, (2) release of toxic metal ions, (3) alteration of cellular pH via proton efflux pumps, (4) generation of reactive oxygen species, (5) damage of nuclear materials, and (6) loss of ATP production. Nanomedicine contributes to various pharmaceutical applications, like diagnosis and treatment of various ailments including microbial diseases. Furthermore, nanostructured antimicrobial agents are also involved in the treatment of the neuroinfections associated with neurodegenerative disorders. This chapter focuses on the nanostructure and nanomedicine of antimicrobial agents and their prospects for the possible management of infections associated with neurodegenerative disorders.

(19)F Magnetic Resonance Imaging Signals from Peptide Amphiphile Nanostructures Are Strongly Affected by Their Shape

Magnetic resonance imaging (MRI) is a noninvasive imaging modality that provides excellent spatial and temporal resolution. The most commonly used MR probes face significant challenges originating from the endogenous (1)H background signal of water. In contrast, fluorine MRI ((19)F MRI) allows quantitative probe imaging with zero background signal. Probes with high fluorine content are required for high sensitivity, suggesting nanoscale supramolecular assemblies containing (19)F probes offer a potentially useful strategy for optimum imaging as a result of improved payload. We report here on supramolecular nanostructures formed by fluorinated peptide amphiphiles containing either glutamic acid or lysine residues in their sequence. We identified molecules that form aggregates in water which transition from cylindrical to ribbon-like shape as pH increased from 4.5 to 8.0. Interestingly, we found that ribbon-like nanostructures had reduced magnetic resonance signal, whereas their cylindrical counterparts exhibited strong signals. We attribute this drastic difference to the greater mobility of fluorinated tails in the hydrophobic compartment of cylindrical nanostructures compared to lower mobility in ribbon-like assemblies. This discovery identifies a strategy to design supramolecular, self-assembling contrast agents for (19)F MRI that can spatially map physiologically relevant changes in pH using changes in morphology.

Recent Advances in 19Fluorine Magnetic Resonance Imaging with Perfluorocarbon Emulsions

The research roots of ¹⁹fluorine (¹⁹F) magnetic resonance imaging (MRI) date back over 35 years. Over that time span, ¹H imaging flourished and was adopted worldwide with an endless array of applications and imaging approaches, making magnetic resonance an indispensable pillar of biomedical diagnostic imaging. For many years during this timeframe, ¹⁹F imaging research continued at a slow pace as the various attributes of the technique were explored. However, over the last decade and particularly the last several years, the pace and clinical relevance of ¹⁹F imaging has exploded. In part, this is due to advances in MRI instrumentation, ¹⁹F/¹H coil designs, and ultrafast pulse sequence development for both preclinical and clinical scanners. These achievements, coupled with interest in the molecular imaging of anatomy and physiology, and combined with a cadre of innovative agents, have brought the concept of ¹⁹F into early clinical evaluation. In this review, we attempt to provide a slice of this rich history of research and development, with a particular focus on liquid perfluorocarbon compound-based agents.

Application of acoustic droplet vaporization in ultrasound therapy

Microbubbles have been used widely both in the ultrasonic diagnosis to enhance the contrast of vasculature and in ultrasound therapy to increase the bioeffects induced by bubble cavitation. However, due to their large size, the lifetime of microbubbles in the circulation system is on the order of minutes, and they cannot penetrate through the endothelial gap to enter the tumor. In an acoustic field, liquefied gas nanoparticles may be able to change the state and become the gas form in a few cycles of exposure without significant heating effects. Such a phenomenon is called as acoustic droplet vaporization (ADV). This review is intended to introduce the emerging application of ADV. The physics and the theoretical model behind it are introduced for further understanding of the mechanisms. Current manufacturing approaches are provided, and their differences are compared. Based on the characteristic of phase shift, a variety of therapeutic applications have been carried out both in vitro and in vivo. The latest progress and interesting results of vessel occlusion, thermal ablation using high-intensity focused ultrasound (HIFU), localized drug delivery to the tumor and cerebral tissue through the blood-brain barrier, localized tissue erosion by histotripsy are summarized. ADV may be able to overcome some limitations of microbubble-mediated ultrasound therapy and provide a novel drug and molecular targeting carrier. More investigation will help progress this technology forward for clinical translation.

Therapeutic potential of ultrasound microbubbles in gastrointestinal oncology: recent advances and future prospects

Microbubbles were initially invented as contrast agents for ultrasound imaging. However, lately more and more therapeutic applications of microbubbles are emerging, mostly related to drug and gene delivery. Ultrasound is a safe and noninvasive therapeutic modality which has the unique ability to interact with microbubbles and release their payload in situ in addition to permeabilizing the target tissues. The combination of drug-loaded microbubbles and ultrasound has been used in preclinical studies on blood-brain barrier opening, drug and gene delivery to solid tumors, and ablation of blood vessels. This review covers the basic principles of ultrasound-microbubble interaction, the types of microbubbles and the effect they have on tissue, and the preclinical and clinical experience with this approach to date in the field of gastrointestinal oncology.

Contact-facilitated drug delivery with Sn2 lipase labile prodrugs optimize targeted lipid nanoparticle drug delivery

Sn2 lipase labile phospholipid prodrugs in conjunction with contact-facilitated drug delivery offer an important advancement in Nanomedicine. Many drugs incorporated into nanosystems, targeted or not, are substantially lost during circulation to the target. However, favorably altering the pharmacokinetics and volume of distribution of systemic drug delivery can offer greater efficacy with lower toxicity, leading to new prolonged-release nanoexcipients. However, the concept of achieving Paul Erhlich's inspired vision of a 'magic bullet' to treat disease has been largely unrealized due to unstable nanomedicines, nanosystems achieving low drug delivery to target cells, poor intracellular bioavailability of endocytosed nanoparticle payloads, and the substantial biological barriers of extravascular particle penetration into pathological sites. As shown here, Sn2 phospholipid prodrugs in conjunction with contact-facilitated drug delivery prevent premature drug diffusional loss during circulation and increase target cell bioavailability. The Sn2 phospholipid prodrug approach applies equally well for vascular constrained lipid-encapsulated particles and micelles the size of proteins that penetrate through naturally fenestrated endothelium in the bone marrow or thin-walled venules of an inflamed microcirculation. At one time Nanomedicine was considered a 'Grail Quest' by its loyal opposition and even many in the field adsorbing the pains of a long-learning curve about human biology and particles. However, Nanomedicine with innovations like Sn2 phospholipid prodrugs has finally made 'made the turn' toward meaningful translational success.

Synergy between surface and core entrapped metals in a mixed manganese-gadolinium nanocolloid affords safer MR imaging of sparse biomarkers

High-relaxivity T1-weighted (T1w) MR molecular imaging nanoparticles typically present high surface gadolinium payloads that can elicit significant acute complement activation (CA). The objective of this research was to develop a high T1w contrast nanoparticle with improved safety. We report the development, optimization, and characterization of a gadolinium-manganese hybrid nanocolloid (MnOL-Gd NC; 138±10 (Dav)/nm; PDI: 0.06; zeta: -27±2 mV). High r1 particulate relaxivity with minute additions of Gd-DOTA-lipid conjugate to the MnOL nanocolloid surface achieved an unexpected paramagnetic synergism. This hybrid MnOL-Gd NC provided optimal MR TSE signal intensity at 5 nM/voxel and lower levels consistent with the level expression anticipated for sparse biomarkers, such as neovascular integrins. MnOL NC produced optimal MR TSE signal intensity at 10 nM/voxel concentrations and above. Importantly, MnOL-Gd NC avoided acute CA in vitro and in vivo while retaining minimal transmetallation risk. From the clinical editor: The authors developed a gadolinium-manganese hybrid nanocolloid (MnOL-Gd NC) in this study. These were used as a high-relaxivity paramagnetic MR molecular imaging agent in experimental models. It was shown that MnOL-Gd NC could provide high T1w MR contrast for targeted imaging. As the level of gadolinium used was reduced, there was also reduced risk of systemic side effects from complement activation.

Macrophage targeted theranostics as personalized nanomedicine strategies for inflammatory diseases

Inflammatory disease management poses challenges due to the complexity of inflammation and inherent patient variability, thereby necessitating patient-specific therapeutic interventions. Theranostics, which integrate therapeutic and imaging functionalities, can be used for simultaneous imaging and treatment of inflammatory diseases. Theranostics could facilitate assessment of safety, toxicity and real-time therapeutic efficacy leading to personalized treatment strategies. Macrophages are an important cellular component of inflammatory diseases, participating in varied roles of disease exacerbation and resolution. The inherent phagocytic nature, abundance and disease homing properties of macrophages can be targeted for imaging and therapeutic purposes. This review discusses the utility of theranostics in macrophage ablation, phenotype modulation and inhibition of their inflammatory activity leading to resolution of inflammation in several diseases.

The effects of oil-in-water nanoemulsion polyethylene glycol surface density on intracellular stability, pharmacokinetics, and biodistribution in tumor bearing mice

PURPOSE

Lipid-based nanoparticles are extensively studied for drug delivery. These nanoparticles are often surface-coated with polyethylene glycol (PEG) to improve their biodistribution. Until now, the effects of varying PEG surface density have been studied in a narrow and low range. Here, the effects of high and a broad range of PEG surface densities on the in vivo performance of lipid-based nanoparticles were studied.

METHODS

Oil-in-water nanoemulsions were prepared with PEG surface densities of 5-50 mol%. Confocal microscopy was used to assess intracellular disintegration in vitro. In vivo pharmacokinetics and biodistribution in tumor bearing mice were studied using a small animal optical imager.

RESULTS

PEG surface density did not affect intracellular nanoemulsion stability. Surprisingly, circulation half-lives decreased with increasing PEG surface density. A plausible explanation was that nanoemulsion with high (50 mol%) PEG surface density activated the complement in a whole blood assay, whereas nanoemulsion with low (5 mol%) PEG density did not. In vivo, nanoemulsion with low PEG surface density was mostly confined to the tumor and organs of the mononuclear phagocyte system, whereas nanoemulsion with high PEG density accumulated throughout the mouse.

CONCLUSIONS

Optimal PEG surface density of lipid-based nanoparticles for tumor targeting was found to be below 10 mol%.

Perfluorocarbon nanoparticles: evolution of a multimodality and multifunctional imaging agent

Perfluorocarbon nanoparticles offer a biologically inert, highly stable, and nontoxic platform that can be specifically designed to accomplish a range of molecular imaging and drug delivery functions in vivo. The particle surface can be decorated with targeting ligands to direct the agent to a variety of biomarkers that are associated with diseases such as cancer, cardiovascular disease, obesity, and thrombosis. The surface can also carry a high payload of imaging agents, ranging from paramagnetic metals for MRI, radionuclides for nuclear imaging, iodine for CT, and florescent tags for histology, allowing high sensitivity mapping of cellular receptors that may be expressed at very low levels in the body. In addition to these diagnostic imaging applications, the particles can be engineered to carry highly potent drugs and specifically deposit them into cell populations that display biosignatures of a variety of diseases. The highly flexible and robust nature of this combined molecular imaging and drug delivery vehicle has been exploited in a variety of animal models to demonstrate its potential impact on the care and treatment of patients suffering from some of the most debilitating diseases.

Vascular targeting of nanocarriers: perplexing aspects of the seemingly straightforward paradigm

Targeted nanomedicine holds promise to find clinical use in many medical areas. Endothelial cells that line the luminal surface of blood vessels represent a key target for treatment of inflammation, ischemia, thrombosis, stroke, and other neurological, cardiovascular, pulmonary, and oncological conditions. In other cases, the endothelium is a barrier for tissue penetration or a victim of adverse effects. Several endothelial surface markers including peptidases (e.g., ACE, APP, and APN) and adhesion molecules (e.g., ICAM-1 and PECAM) have been identified as key targets. Binding of nanocarriers to these molecules enables drug targeting and subsequent penetration into or across the endothelium, offering therapeutic effects that are unattainable by their nontargeted counterparts. We analyze diverse aspects of endothelial nanomedicine including (i) circulation and targeting of carriers with diverse geometries, (ii) multivalent interactions of carrier with endothelium, (iii) anchoring to multiple determinants, (iv) accessibility of binding sites and cellular response to their engagement, (v) role of cell phenotype and microenvironment in targeting, (vi) optimization of targeting by lowering carrier avidity, (vii) endocytosis of multivalent carriers via molecules not implicated in internalization of their ligands, and (viii) modulation of cellular uptake and trafficking by selection of specific epitopes on the target determinant, carrier geometry, and hydrodynamic factors. Refinement of these aspects and improving our understanding of vascular biology and pathology is likely to enable the clinical translation of vascular endothelial targeting of nanocarriers.

Perfluorocarbon nanoemulsions with fluorescent, colloidal and magnetic properties

Bimodal imaging agents that combine magnetic resonance imaging (MRI) and nearinfrared (NIR) imaging formulated as nanoemulsions became increasingly popular for imaging inflammation in vivo. Quality of in vivo imaging using nanoemulsions is directly dependent on their integrity and stability. Here we report the design of nanoemulsions for bimodal imaging, where both photostability and colloidal stability are equally addressed. A highly chemically and photo stable quaterrylenediimide dye was introduced into perfluoro-15-crown-5 ether (PCE) nanoemulsions. The nanoemulsions were prepared with PCE and Miglyol 812N mixed at 1:1 v/v ratio as internal phase stabilized by non-ionic surfactants. Data shows exceptional colloidal stability demonstrated as unchanged droplet size (~130 nm) and polydispersity (<0.15) after 182 days follow up at both 4 and 25 °C. Nanoemulsions also sustained the exposure to mechanical and temperature stress, and prolonged exposure to light without changes in droplet size, (19)F signal or fluorescence signal. No toxicity was observed in vitro in model inflammatory cells upon 24 h exposure while confocal microscopy showed that nanoemulsions droplets accumulated in the cytoplasm. Overall, our data demonstrates that design of bimodal imaging agents requires consideration of stability of each imaging component and that of the nanosystem as a whole to achieve excellent imaging performance.

Anti-angiogenesis therapy in the Vx2 rabbit cancer model with a lipase-cleavable Sn 2 taxane phospholipid prodrug using α(v)β₃-targeted theranostic nanoparticles

In nanomedicine, the hydrophobic nature of paclitaxel has favored its incorporation into many nanoparticle formulations for anti-cancer chemotherapy. At lower doses taxanes are reported to elicit anti-angiogenic responses. In the present study, the facile synthesis, development and characterization of a new lipase-labile docetaxel prodrug is reported and shown to be an effective anti-angiogenic agent in vitro and in vivo. The Sn 2 phosphatidylcholine prodrug was stably incorporated into the lipid membrane of α_vβ₃-integrin targeted perfluorocarbon (PFC) nanoparticles (α_vβ₃-Dxtl-PD NP) and did not appreciably release during dissolution against PBS buffer or plasma over three days. Overnight exposure of α_vβ₃-Dxtl-PD NP to plasma spiked with phospholipase enzyme failed to liberate the taxane from the membrane until the nanoparticle integrity was compromised with alcohol. The bioactivity and efficacy of α_vβ₃-Dxtl-PD NP in endothelial cell culture was as effective as Taxol^® or free docetaxel in methanol at equimolar doses over 96 hours. The anti-angiogenesis effectiveness of α_vβ₃-Dxtl-PD NP was demonstrated in the Vx2 rabbit model using MR imaging of angiogenesis with the same α_vβ₃-PFC nanoparticle platform. Nontargeted Dxtl-PD NP had a similar MR anti-angiogenesis response as the integrin-targeted agent, but microscopically measured decreases in tumor cell proliferation and increased apoptosis were detected only for the targeted drug. Equivalent dosages of Abraxane^® given over the same treatment schedule had no effect on angiogenesis when compared to control rabbits receiving saline only. These data demonstrate that α_vβ₃-Dxtl-PD NP can reduce MR detectable angiogenesis and slow tumor progression in the Vx2 model, whereas equivalent systemic treatment with free taxane had no benefit.

Antibody-based tumor vascular theranostics targeting endosialin/TEM1 in a new mouse tumor vascular model

Tumor endothelial marker 1 (TEM1, endosialin) is a tumor vascular marker with significant diagnostic and therapeutic potential. However, in vivo small animal models to test affinity reagents specifically targeted to human (h)TEM1 are limited. We describe a new mouse tumor model where tumor vascular endothelial cells express hTEM1 protein.

METHODS

Immortalized murine endothelial cells MS1 were engineered to express hTEM1 and firefly luciferase and were inoculated in nude mice either alone, to form hemangioma-like endothelial grafts, or admixed with ID8 ovarian tumor cells, to form chimeric endothelial-tumor cell grafts. MORAb-004, a monoclonal humanized IgG 1 antibody specifically recognizing human TEM1 was evaluated for targeted theranostic applications, i.e., for its ability to affect vascular grafts expressing hTEM1 as well as being a tool for molecular positron emission tomography (PET) imaging.

RESULTS

Naked MORAb-004 treatment of mice bearing angioma grafts or chimeric endothelial-tumor grafts significantly suppressed the ability of hTEM1-positive endothelial cells, but not control endothelial cells, to form grafts and dramatically suppressed local angiogenesis. In addition, highly efficient radioiodination of MORAb-004 did not impair its affinity for hTEM1, and [ (124)I]-MORAb-004-PET enabled non-invasive visualization of tumors enriched with hTEM1-positive, but not hTEM1 negative vasculature with high degree of specificity and sensitivity.

CONCLUSION

The development of a new robust endothelial graft model expressing human tumor vascular proteins will help accelerate the development of novel theranostics targeting the tumor vasculature, which exhibit affinity specifically to human targets but not their murine counterparts. Our results also demonstrate the theranostic potential of MORAb-004 as PET imaging tracer and naked antibody therapy for TEM1-positive tumor.

Nanotechnological strategies for therapeutic targeting of tumor vasculature

Neovascularization plays fundamental roles in tumor growth and metastasis. Tumor blood vessels are highly accessible and express various angiogenic markers that are either not present or are expressed at low levels in normal vessels, thereby serving as favorable targets for cancer therapy. Cancer nanotechnology, as an integrated platform, offers great opportunities for optimizing drug efficacy and pharmacokinetics while reducing side effects. Nanoparticles with tunable size, shape and surface modification have been exploited to achieve effective tumor vascular targeting. Here, we briefly introduce the signatures of tumor neovascularization and the review investigations on vascular-targeted anti-tumor nanomedicines. We also provide our perspectives on the promising fields of combination therapy and theranostic nanomedicines, as well as the challenges of nanotechnology-based cancer therapy. Furthermore, introducing new functionality would significantly consolidate the current development of nanomaterials based on tumor vasculature targeting.

Gd-based macromolecules and nanoparticles as magnetic resonance contrast agents for molecular imaging

As we move towards an era of personalized medicine, molecular imaging contrast agents are likely to see an increasing presence in routine clinical practice. Magnetic resonance (MR) imaging has garnered particular interest as a platform for molecular imaging applications due its ability to monitor anatomical changes concomitant with physiologic and molecular changes. One promising new direction in the development of MR contrast agents involves the labeling and/or loading of nanoparticles with gadolinium (Gd). These nanoplatforms are capable of carrying large payloads of Gd, thus providing the requisite sensitivity to detect molecular signatures within disease pathologies. In this review, we discuss some of the progress that has recently been made in the development of Gd-based macromolecules and nanoparticles and outline some of the physical and chemical properties that will be important to incorporate into the next generation of contrast agents, including high Gd chelate stability, high "relaxivity per particle" and "relaxivity density", and biodegradability.

Improving the performance of phase-change perfluorocarbon droplets for medical ultrasonography: current progress, challenges, and prospects

Over the past two decades, perfluorocarbon (PFC) droplets have been investigated for biomedical applications across a wide range of imaging modalities. More recently, interest has increased in "phase-change" PFC droplets (or "phase-change" contrast agents), which can convert from liquid to gas with an external energy input. In the field of ultrasound, phase-change droplets present an attractive alternative to traditional microbubble agents for many diagnostic and therapeutic applications. Despite the progress, phase-change PFC droplets remain far from clinical implementation due to a number of challenges. In this review, we survey our recent work to enhance the performance of phase-change agents for ultrasound through a variety of techniques in order to provide increased efficacy in therapeutic applications of ultrasound and enable previously unexplored applications in diagnostic and molecular imaging.

Application of a hemolysis assay for analysis of complement activation by perfluorocarbon nanoparticles

Nanoparticles offer new options for medical diagnosis and therapeutics with their capacity to specifically target cells and tissues with imaging agents and/or drug payloads. The unique physical aspects of nanoparticles present new challenges for this promising technology. Studies indicate that nanoparticles often elicit moderate to severe complement activation. Using human in vitro assays that corroborated the mouse in vivo results we previously presented mechanistic studies that define the pathway and key components involved in modulating complement interactions with several gadolinium-functionalized perfluorocarbon nanoparticles (PFOB). Here we employ a modified in vitro hemolysis-based assay developed in conjunction with the mouse in vivo model to broaden our analysis to include PFOBs of varying size, charge and surface chemistry and examine the variations in nanoparticle-mediated complement activity between individuals. This approach may provide the tools for an in-depth structure-activity relationship study that will guide the eventual development of biocompatible nanoparticles.

FROM THE CLINICAL EDITOR

Unique physical aspects of nanoparticles may lead to moderate to severe complement activation in vivo, which represents a challenge to clinical applicability. In order to guide the eventual development of biocompatible nanoparticles, this team of authors report a modified in vitro hemolysis-based assay developed in conjunction with their previously presented mouse model to enable in-depth structure-activity relationship studies.

Perfluorocarbon nanoparticles for physiological and molecular imaging and therapy

Herein, we review the use of non-nephrotoxic perfluorocarbon nanoparticles (PFC NPs) for noninvasive detection and therapy of kidney diseases, and we provide a synopsis of other related literature pertinent to their anticipated clinical application. Recent reports indicate that PFC NPs allow for quantitative mapping of kidney perfusion and oxygenation after ischemia-reperfusion injury with the use of a novel multinuclear (1)H/(19)F magnetic resonance imaging approach. Furthermore, when conjugated with targeting ligands, the functionalized PFC NPs offer unique and quantitative capabilities for imaging inflammation in the kidney of atherosclerotic ApoE-null mice. In addition, PFC NPs can facilitate drug delivery for treatment of inflammation, thrombosis, and angiogenesis in selected conditions that are comorbidities for kidney failure. The excellent safety profile of PFC NPs with respect to kidney injury positions these nanomedicine approaches as promising diagnostic and therapeutic candidates for treating and following acute and chronic kidney diseases.

Assessing the barriers to image-guided drug delivery

Imaging has become a cornerstone for medical diagnosis and the guidance of patient management. A new field called image-guided drug delivery (IGDD) now combines the vast potential of the radiological sciences with the delivery of treatment and promises to fulfill the vision of personalized medicine. Whether imaging is used to deliver focused energy to drug-laden particles for enhanced, local drug release around tumors, or it is invoked in the context of nanoparticle-based agents to quantify distinctive biomarkers that could risk stratify patients for improved targeted drug delivery efficiency, the overarching goal of IGDD is to use imaging to maximize effective therapy in diseased tissues and to minimize systemic drug exposure in order to reduce toxicities. Over the last several years, innumerable reports and reviews covering the gamut of IGDD technologies have been published, but inadequate attention has been directed toward identifying and addressing the barriers limiting clinical translation. In this consensus opinion, the opportunities and challenges impacting the clinical realization of IGDD-based personalized medicine were discussed as a panel and recommendations were proffered to accelerate the field forward.

Current status and prospects for microbubbles in ultrasound theranostics

Encapsulated microbubbles have been developed over the past two decades to provide improvements both in imaging as well as new therapeutic applications. Microbubble contrast agents are used currently for clinical imaging where increased sensitivity to blood flow is required, such as echocardiography. These compressible spheres oscillate in an acoustic field, producing nonlinear responses which can be uniquely distinguished from surrounding tissue, resulting in substantial enhancements in imaging signal-to-noise ratio. Furthermore, with sufficient acoustic energy the oscillation of microbubbles can mediate localized biological effects in tissue including the enhancement of membrane permeability or increased thermal energy deposition. Structurally, microbubbles are comprised of two principal components--an encapsulating shell and an inner gas core. This configuration enables microbubbles to be loaded with drugs or genes for additional therapeutic effect. Application of sufficient ultrasound energy can release this payload, resulting in site-specific delivery. Extensive preclinical studies illustrate that combining microbubbles and ultrasound can result in enhanced drug delivery or gene expression at spatially selective sites. Thus, microbbubles can be used for imaging, for therapy, or for both simultaneously. In this sense, microbubbles combined with acoustics may be one of the most universal theranostic tools.

Toward ultrasound molecular imaging with phase-change contrast agents: an in vitro proof of principle

Phase-change contrast agents (PCCAs), which normally consist of nanoscale or microscale droplets of liquid perfluorocarbons in an encapsulating shell, can be triggered to undergo a phase transition to the highly echogenic gaseous state upon the input of sufficient acoustic energy. As a result of the subsequent volumetric expansion, a number of unique applications have emerged that are not possible with traditional ultrasound microbubble contrast agents. Although many studies have explored the therapeutic aspects of the PCCA platform, few have examined the potential of PCCAs for molecular imaging purposes. In this study, we demonstrate a PCCA-based platform for molecular imaging using α(v)β(3)-targeted nanoscale PCCAs composed of low-boiling-point perfluorocarbons. In vitro, nanoscale PCCAs adhered to target cells, could be activated and imaged with a clinical ultrasound system and produced a six-fold increase in image contrast compared with non-targeted control PCCAs and a greater than fifty-fold increase over baseline. Data suggest that low-boiling-point nanoscale PCCAs could enable future ultrasound-based molecular imaging techniques in both the vascular and extravascular spaces.

Current status and prospects for microbubbles in ultrasound theranostics

Encapsulated microbubbles have been developed over the past two decades to provide improvements both in imaging as well as new therapeutic applications. Microbubble contrast agents are used currently for clinical imaging where increased sensitivity to blood flow is required, such as echocardiography. These compressible spheres oscillate in an acoustic field, producing nonlinear responses which can be uniquely distinguished from surrounding tissue, resulting in substantial enhancements in imaging signal-to-noise ratio. Furthermore, with sufficient acoustic energy the oscillation of microbubbles can mediate localized biological effects in tissue including the enhancement of membrane permeability or increased thermal energy deposition. Structurally, microbubbles are comprised of two principal components--an encapsulating shell and an inner gas core. This configuration enables microbubbles to be loaded with drugs or genes for additional therapeutic effect. Application of sufficient ultrasound energy can release this payload, resulting in site-specific delivery. Extensive preclinical studies illustrate that combining microbubbles and ultrasound can result in enhanced drug delivery or gene expression at spatially selective sites. Thus, microbbubles can be used for imaging, for therapy, or for both simultaneously. In this sense, microbubbles combined with acoustics may be one of the most universal theranostic tools.

Multifunctional magnetic resonance imaging probes

Magnetic resonance imaging (MRI) is a key imaging modality in cancer diagnostics and therapy monitoring. MRI-based tumor detection and characterization is commonly achieved by exploiting the compositional, metabolic, cellular, and vascular differences between malignant and healthy tissue. Contrast agents are frequently applied to enhance this contrast. The last decade has witnessed an increasing interest in novel multifunctional MRI probes. These multifunctional constructs, often of nanoparticle design, allow the incorporation of multiple imaging agents for complementary imaging modalities as well as anti-cancer drugs for therapeutic purposes. The composition, size, and surface properties of such constructs can be tailored as to improve biodistribution and ensure optimal delivery to the tumor microenvironment by passive or targeted mechanisms. Multifunctional MRI probes hold great promise to facilitate more specific tumor diagnosis, patient-specific treatment planning, the monitoring of local drug delivery, and the early evaluation of therapy. This chapter reviews the state-of-the-art and new developments in the application of multifunctional MRI probes in oncology.

Phase-change nanoparticles using highly volatile perfluorocarbons: toward a platform for extravascular ultrasound imaging

Recent efforts using perfluorocarbon (PFC) nanoparticles in conjunction with acoustic droplet vaporization has introduced the possibility of expanding the diagnostic and therapeutic capability of ultrasound contrast agents to beyond the vascular space. Our laboratories have developed phase-change nanoparticles (PCNs) from the highly volatile PFCs decafluorobutane (DFB, bp =-2 °C) and octafluoropropane (OFP, bp =-37 °C ) for acoustic droplet vaporization. Studies with commonly used clinical ultrasound scanners have demonstrated the ability to vaporize PCN emulsions with frequencies and mechanical indices that may significantly decrease tissue bioeffects. In addition, these contrast agents can be formulated to be stable at physiological temperatures and the perfluorocarbons can be mixed to modulate the balance between sensitivity to ultrasound and general stability. We herein discuss our recent efforts to develop finely-tuned diagnostic/molecular imaging agents for tissue interrogation. We discuss studies currently under investigation as well as potential diagnostic and therapeutic paradigms that may emerge as a result of formulating PCNs with low boiling point PFCs.

19F molecular MR imaging for detection of brain tumor angiogenesis: in vivo validation using targeted PFOB nanoparticles

Molecular imaging with magnetic resonance imaging (MRI) targeted contrast agents has emerged as a promising diagnostic approach in cancer research to detect associated biomarkers. In this work, the potential of (19)F MRI was investigated to detect angiogenesis with α(ν)β(3)-targeted perfluorooctylbromide nanoparticles (PFOB NP) in a U87 glioblastoma mouse model at 7 Tesla. Mice were injected intravenously with targeted or non-targeted NP and (19)F images were immediately acquired for 90 min using a PFOB-dedicated MRI sequence. Mice infused with targeted NP exhibited higher concentrations in tumors than mice of the control group, despite the presence of nonspecific signal originating from the blood. Imaging results were corroborated by histology and fluorescence imaging, suggesting specific binding of targeted NP to α(ν)β(3) integrin. Two other groups of mice were injected 24 h before imaging to allow blood clearance but no significant differences were found between both groups, probably due to a loss of specificity of PFOB NP. This is the first demonstration of the ability of (19)F MRI to detect α(ν)β(3)-integrin endothelial expression in brain tumors in vivo.

Nanotheranostics for personalized medicine

The application of nanotechnology in the biomedical field, known as nanomedicine, has gained much interest in the recent past, as versatile strategy for selective drug delivery and diagnostic purposes. The already encouraging results obtained with monofunctional nanomedicines have directed the efforts of the scientists towards the creation of "nanotheranostics" (i.e. theranostic nanomedicines) which integrate imaging and therapeutic functions in a single platform. Nanotheranostics hold great promises because they combine the simultaneous non-invasive diagnosis and treatment of diseases with the exciting possibility to monitor in real time drug release and distribution, thus predicting and validating the effectiveness of the therapy. Due to these features nanotheranostics are extremely attractive for optimizing treatment outcomes in cancer and other severe diseases. The following step is the attempt to use nanotheranostics for performing a real personalized medicine which will tailor optimized treatment to each patient, taking into account the individual variability. Clinical application of nanotheranostics would enable earlier detection and treatment of diseases and earlier assessment of the response, thus allowing screening for patients which would potentially respond to therapy and have higher possibilities of a favorable outcome. This concept makes nanotheranostics extremely appealing to elaborate personalized therapeutic protocols for achieving the maximal benefit along with a high safety profile. Among the several systems developed up to now, this review focuses on the nanotheranostics which, due to the promising results, show the highest potential of translation to clinical applications and may transform into concrete practice the concept of personalized nanomedicine.

Phase-change contrast agents for imaging and therapy

Phase-change contrast agents (PCCAs) for ultrasound-based applications have resulted in novel ways of approaching diagnostic and therapeutic techniques beyond what is possible with microbubble contrast agents and liquid emulsions. When subjected to sufficient pressures delivered by an ultrasound transducer, stabilized droplets undergo a phase-transition to the gaseous state and a volumetric expansion occurs. This phenomenon, termed acoustic droplet vaporization, has been proposed as a means to address a number of in vivo applications at the microscale and nanoscale. In this review, the history of PCCAs, physical mechanisms involved, and proposed applications are discussed with a summary of studies demonstrated in vivo. Factors that influence the design of PCCAs are discussed, as well as the need for future studies to characterize potential bioeffects for administration in humans and optimization of ultrasound parameters.