Lipid-Iron Nanoparticle with a Cell Stress Release Mechanism Combined with a Local Alternating Magnetic Field Enables Site-Activated Drug Release

Simple Summary A novel active release system magnetic sphingomyelin-containing liposome encapsulated with indocyanine green, fluorescent marker, or the anticancer drug cisplatin was evaluated. The liposomal sphingomyelin is a target for the sphingomyelinase enzyme, which is released by stressed cells. Thus, sphingomyelin containing liposomes behave as a sensitizer for biological stress situations. In addition, the liposomes were engineered by adding paramagnetic beads to act as a receiver of outside given magnetic energy. The enzymatic activity towards liposomes and destruction caused by the applied magnetic field caused the release of the content from the liposomes. By using these novel liposomes, we could improve the drug release feature of liposomes. The improved targeting and drug-release were shown in vitro and the orthotopic tongue cancer model in mice optical imaging. The increased delivery of cisplatin prolonged the survival of the targeted delivery group versus free cisplatin. Most available cancer chemotherapies are based on systemically administered small organic molecules, and only a tiny fraction of the drug reaches the disease site. The approach causes significant side effects and limits the outcome of the therapy. Targeted drug delivery provides an alternative to improve the situation. However, due to the poor release characteristics of the delivery systems, limitations remain. This report presents a new approach to address the challenges using two fundamentally different mechanisms to trigger the release from the liposomal carrier. We use an endogenous disease marker, an enzyme, combined with an externally applied magnetic field, to open the delivery system at the correct time only in the disease site. This site-activated release system is a novel two-switch nanomachine that can be regulated by a cell stress-induced enzyme at the cellular level and be remotely controlled using an applied magnetic field. We tested the concept using sphingomyelin-containing liposomes encapsulated with indocyanine green, fluorescent marker, or the anticancer drug cisplatin. We engineered the liposomes by adding paramagnetic beads to act as a receiver of outside magnetic energy. The developed multifunctional liposomes were characterized in vitro in leakage studies and cell internalization studies. The release system was further studied in vivo in imaging and therapy trials using a squamous cell carcinoma tumor in the mouse as a disease model. In vitro studies showed an increased release of loaded material when stress-related enzyme and magnetic field was applied to the carrier liposomes. The theranostic liposomes were found in tumors, and the improved therapeutic effect was shown in the survival studies.Peer reviewe

A polymeric microbubble platform for ultrasound-mediated drug delivery

In this dissertation, I describe the synthesis and characterization of poly(butyl cyanoacrylate) (PBCA) microbubbles (MB), which were applied as ultrasound (US) contrast agents and drug delivery systems to tumors or across the blood brain barrier (BBB) in preclinical settings. The MB were prepared by an established protocol in one-batch synthesis, which comprised the polymerization of butyl cyanoacrylate in water at a pH of 2.5. The resulted PBCA polymer chains attached to each other due to hydrophobic interactions, thus forming a round shell, encapsulating air. Different synthesis parameters such as stirring time/speed, pH and surfactant were varied to evaluate their influence on the MB properties like size (distribution), molecular weight (distribution) of the PBCA chains, shell thickness, and acoustic properties. The physicochemical properties of MB were evaluated with various techniques: Coulter counter, dynamic light scattering (DLS), gel permeation chromatography (GPC), and electron/fluorescence microscopy. The results showed that stirring time had a high impact on MB size distribution, while pH and surfactant mainly influenced shell thickness and molecular weight of the PBCA chains. Acoustic properties were analyzed at different US frequencies and PBCA MB showed a better acoustic response at 5 MHz in the non-linear US mode compared to commercial micromarker lipid MB. For their in vitro and in vivo application, MB were functionalized by loading fluorescent dyes, iron oxide nanoparticles and drugs within the MB shell, or oxygen in the MB core and analyzed using spectroscopic and microscopic methods. The surface of the MB was modified using fluorescent dyes, PEG or peptides/proteins. Different peptides, targeting E-selectin (a cell adhesion molecule overexpressed on activated endothelial cells in several tumor types), were screened for their binding to endothelial cells. MB conjugated to the best binding peptide were tested in a flow-chamber and showed higher binding to activated HUVEC compared to control MB.MB loaded with the vascular targeting agent combretastatin A4 were tested for their sonoporation ability compared to standard MB in tumor bearing mice. For US and MB treatment, the extravasation of a co-injected fluorescently labeled polymer increased. The results show that MB can be efficiently used as targeted drug delivery system and for ultrasound and photoacoustic imaging

Tumor targeting via EPR: Strategies to enhance patient responses

The tumor accumulation of nanomedicines relies on the enhanced permeability and retention (EPR) effect. In the last 5–10 years, it has been increasingly recognized that there is a large inter- and intra-individual heterogeneity in EPR-mediated tumor targeting, explaining the heterogeneous outcomes of clinical trials in which nanomedicine formulations have been evaluated. To address this heterogeneity, as in other areas of oncology drug development, we have to move away from a one-size-fits-all tumor targeting approach, towards methods that can be employed to individualize and improve nanomedicine treatments. To this end, efforts have to be invested in better understanding the nature, the complexity and the heterogeneity of the EPR effect, and in establishing systems and strategies to enhance, combine, bypass and image EPR-based tumor targeting. In the present manuscript, we summarize key studies in which these strategies are explored, and we discuss how these approaches can be employed to enhance patient responses

Multimodal [GdO]+[ICG]− Nanoparticles for Optical, Photoacoustic, and Magnetic Resonance Imaging

Multimodal contrast agents with high biocompatibility and biodegradability, as well as low material complexity, are in great demand for clinical diagnostics at different scales of resolution and/or for translating preclinical diagnosis into intraoperative imaging. Multimodality, however, often results in multicomponent and multistructured materials with complexity becoming a severe restriction for synthesis, approval, and use in routine clinical practice. Here, we present sulfonate-based saline [GdO]+[ICG]− (ICG, indocyanine green) inorganic-organic hybrid nanoparticles (IOH-NPs with an inorganic [GdO]+ cation and an organic [ICG]− anion) as a novel, multimodality contrast agent for optical, photoacoustic, and magnetic resonance imaging (OI, PAI, MRI). [GdO]+[ICG]− IOH-NPs have a plain composition based on clinically used constituents and are prepared as an insoluble saline compound in water. The high [ICG]− content (81 wt %) ensures intense near-infrared emission (780-840 nm) and a strong photoacoustic signal. First, in vitro studies demonstrate longer detectability and greater emission intensity for [GdO]+[ICG]− IOH-NP suspensions than for ICG solutions, as well as a reduced toxicity compared to that of Gd-DTPA, a standard MRI contrast agent. Conceptual in vivo studies confirm the utility of the [GdO]+[ICG]− IOH-NPs for optical and magnetic resonance imaging with a T1 relaxivity better than that of Gd-DTPA. Taken together, [GdO]+[ICG]− represents a new compound and nanomaterial that can be highly interesting as a multimodal contrast agent

A computational and experimental study to develop E-selectin targeted peptides for molecular imaging applications

International audienc

Noninvasive Assessment of Elimination and Retention using CT-FMT and Kinetic Whole-body Modeling

Fluorescence-mediated tomography (FMT) is a quantitative three-dimensional imaging technique for preclinical research applications. The combination with micro-computed tomography (μCT) enables improved reconstruction and analysis. The aim of this study is to assess the potential of μCT-FMT and kinetic modeling to determine elimination and retention of typical model drugs and drug delivery systems. We selected four fluorescent probes with different but well-known biodistribution and elimination routes: Indocyanine green (ICG), hydroxyapatite-binding OsteoSense (OS), biodegradable nanogels (NG) and microbubbles (MB). μCT-FMT scans were performed in twenty BALB/c nude mice (5 per group) at 0.25, 2, 4, 8, 24, 48 and 72 h after intravenous injection. Longitudinal organ curves were determined using interactive organ segmentation software and a pharmacokinetic whole-body model was implemented and applied to compute physiological parameters describing elimination and retention. ICG demonstrated high initial hepatic uptake which decreased rapidly while intestinal accumulation appeared for around 8 hours which is in line with the known direct uptake by hepatocytes followed by hepatobiliary elimination. Complete clearance from the body was observed at 48 h. NG showed similar but slower hepatobiliary elimination because these nanoparticles require degradation before elimination can take place. OS was strongly located in the bones in addition to high signal in the bladder at 0.25 h indicating fast renal excretion. MB showed longest retention in liver and spleen and low signal in the kidneys likely caused by renal elimination or retention of fragments. Furthermore, probe retention was found in liver (MB, NG and OS), spleen (MB) and kidneys (MB and NG) at 72 h which was confirmed by ex vivo data. The kinetic model enabled robust extraction of physiological parameters from the organ curves. In summary, μCT-FMT and kinetic modeling enable differentiation of hepatobiliary and renal elimination routes and allow for the noninvasive assessment of retention sites in relevant organs including liver, kidney, bone and spleen. © Ivyspring International Publisher

Image-guided, targeted and triggered drug delivery to tumors using polymer-based microbubbles.

Abstract Microbubbles (MB) are routinely used contrast agents for functional and molecular ultrasound (US) imaging. In addition, they have been attracting more and more attention for drug delivery purposes, enabling e.g. US-mediated drug delivery across biological barriers and US-induced triggered drug release from the MB shell. The vast majority of efforts in this regard have thus far focused on phospholipid-based soft-shell MB, which are suboptimal for stably incorporating large amounts of drug molecules because of their relatively thin shell. Using poly(butyl cyanoacrylate) (PBCA)-based hard-shell MB, we show here that both hydrophilic (Rhodamine-B) and hydrophobic (Coumarin-6) model drugs can be efficiently and stably entrapped within the ~50 nm shell of PBCA MB. In addition, we demonstrate that model drug loading does not negatively affect the acoustic properties of the MB, and that functionalizing the surface of fluorophore-loaded MB with anti-VEGFR2 antibodies enables image-guided and targeted model drug delivery to tumor blood vessels. Finally, we show both in vitro and in vivo that disintegrating VEGFR2-targeted MB with high-mechanical index US pulses leads to high levels of model drug release. Consequently, these findings indicate that polymer-based MB are highly suitable systems for image-guided, targeted and triggered drug delivery to tumors and tumor blood vessels