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Rangger C.,Innsbruck Medical University | Helbok A.,Innsbruck Medical University | Sosabowski J.,Queen Mary, University of London | Kremser C.,Innsbruck Medical University | And 7 more authors.
International Journal of Nanomedicine | Year: 2013

Background: The significant progress in nanotechnology provides a wide spectrum of nanosized material for various applications, including tumor targeting and molecular imaging. The aim of this study was to evaluate multifunctional liposomal nanoparticles for targeting approaches and detection of tumors using different imaging modalities. The concept of dual-targeting was tested in vitro and in vivo using liposomes derivatized with an arginine-glycine-aspartic acid (RGD) peptide binding to αvβ3 integrin receptors and a substance P peptide binding to neurokinin-1 receptors. Methods: For liposome preparation, lipids, polyethylene glycol building blocks, DTPA-derivatized lipids for radiolabeling, lipid-based RGD and substance P building blocks and imaging labels were combined in defined molar ratios. Liposomes were characterized by photon correlation spectroscopy and zeta potential measurements, and in vitro binding properties were tested using fluorescence microscopy. Standardized protocols for radiolabeling were developed to perform biodistribution and micro-single photon emission computed tomography/computed tomography (SPECT/CT) studies in nude mice bearing glioblastoma and/or melanoma tumor xenografts. Additionally, an initial magnetic resonance imaging study was performed. Results: Liposomes were radiolabeled with high radiochemical yields. Fluorescence microscopy showed specific cellular interactions with RGD-liposomes and substance P-liposomes. Biodistribution and micro-SPECT/CT imaging of 111In-labeled liposomal nanoparticles revealed low tumor uptake, but in a preliminary magnetic resonance imaging study with a single-targeted RGD-liposome, uptake in the tumor xenografts could be visualized. Conclusion: The present study shows the potential of liposomes as multifunctional targeted vehicles for imaging of tumors combining radioactive, fluorescent, and magnetic resonance signaling. Specific in vitro tumor targeting by fluorescence microscopy and radioactivity was achieved. However, biodistribution studies in an animal tumor model revealed only moderate tumor uptake and no additive effect using a dual-targeting approach. © 2013 Rangger et al. Source

Rangger C.,Innsbruck Medical University | Helbok A.,Innsbruck Medical University | Ocak M.,Istanbul University | Radolf T.,PiCHEM Research and Development | And 4 more authors.
Anticancer Research | Year: 2013

Background: Vasoactive intestinal peptide (VIP) receptors are overexpressed in a broad variety of tumours. For the detection of these tumours, novel chemically modified and shortened VIP derivatives were designed. Materials and Methods: 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA)-derivatised VIP analogues were radiolabelled with 111In and in vitro and in vivo behaviour was evaluated using stability and internalisation assays, as well as an initial biodistribution study. Results: Radiolabelling of the VIP analogues resulted in high radiochemical yields, without need for further purification steps. Stability of the VIP derivatives was variable and cell uptake studies in VIP receptor-positive cell lines revealed that only a limited number of derivatives were internalised. In the tumour mouse model, no specific tumour targeting was shown. Conclusion: Since the tested VIP derivatives exhibited impaired in vitro and in vivo characteristics alternative modifications to increase their stability while retaining receptor affinity should be considered to enable the use of synthetic VIP analogues for tumour targeting. Source

Rangger C.,Innsbruck Medical University | Helbok A.,Innsbruck Medical University | von Guggenberg E.,Innsbruck Medical University | Sosabowski J.,Queen Mary, University of London | And 6 more authors.
International Journal of Nanomedicine | Year: 2012

Purpose: Liposomes have been proposed to be a means of selectively targeting cancer sites for diagnostic and therapeutic applications. The focus of this work was the evaluation of radiolabeled PEGylated liposomes derivatized with varying amounts of a cyclic arginyl-glycyl-aspartic acid (RGD) peptide. RGD peptides are known to bind to αvβ3 integrin receptors overexpressed during tumor-induced angiogenesis. Methods: Several liposomal nanoparticles carrying the RGD peptide targeting sequence (RLPs) were synthesized using a combination of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine, cholesterol, diethylenetriaminepentaacetic acid-derivatized lipids for radiolabeling, a polyethylene glycol (PEG) building block, and a lipid-based RGD building block. Relative amounts of RGD and PEG building blocks were varied. In vitro binding affinities were determined using isolated αvβ3 integrin receptors incubated with different concentrations of RLPs in competition with iodine-125-labeled cyclo-(-RGDyV-). Binding of the indium-111-labeled RLPs was also evaluated. Biodistribution and micro single photon emission computed tomography/computed tomography imaging studies were performed in nude mice using different tumor xenograft models. Results: RLPs were labeled with indium-111 with high radiochemical yields. In vitro binding studies of RLPs with different RGD/PEG loading revealed good binding to isolated receptors, which was dependent on the extent of RGD and PEG loading. Binding increased with higher RGD loading, whereas reduced binding was found with higher PEG loading. Biodistribution showed increased circulating time for PEGylated RLPs, but no dependence on RGD loading. Both biodistribution and micro single photon emission computed tomography/computed tomography imaging studies revealed low, nonspecific tumor uptake values. Conclusion: In this study, RLPs for targeting angiogenesis were described. Even though good binding to αvβ3 integrin receptors was found in vitro, the balance between PEGylation and RGD loading clearly requires optimization to achieve targeting in vivo. These data form the basis for future development and provide a platform for the investigation of multimodal approaches. © 2012 Rangger et al, publisher and licensee Dove Medical Press Ltd. Source

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