Exploiting the Metal-Chelating Properties of the Drug Cargo for In Vivo Positron Emission Tomography Imaging of Liposomal Nanomedicines (original) (raw)
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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 α v β 3 integrin receptors and a substance P peptide binding to neurokinin-1 receptors. Methods: For liposome preparation, lipids, polyethylene glycol building blocks, DTPAderivatized 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 111 In-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.
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Radiolabeled PEGylated liposomal nanoparticles (NPs) open new possibilities for a variety of applications including diagnosis, drug delivery, targeted therapy, and monitoring treatment effects. Here we describe the characterization of liposomal NPs (liposomes and micelles) derivatized with the somatostatin analogue tyrosine-3-octreotide as a proof of concept for tumor targeting. NPs were radiolabeled with indium-111, and targeting properties were evaluated in vitro on rat pancreatic tumor cells (AR42J), demonstrating specific binding and IC 50 values in the low nanomolar range. Biodistribution studies were performed in Lewis rats and compared to single-photon emission computed tomography images. Moderate tumor uptake was found in xenografted nude mice (b2.5% ID/g tissue) as compared to control. Micelles and liposomes revealed comparable pharmacokinetics and targeting properties. This study provides insight into tumor-targeting characteristics of peptide-derivatized liposomal NPs and can serve as a basis for further improvement of these constructs. From the Clinical Editor: The authors investigated tumor-targeting characteristics of peptide-derivatized liposomal NPs. Similar radiolabeled PEGylated liposomal NPs open new possibilities for a variety of applications including diagnosis, drug delivery, targeted therapy, and treatment monitoring.
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International journal of molecular sciences, 2017
Radiolabeled liposomes have been employed as diagnostic tools to monitor in vivo distribution of liposomes in real-time, which helps in optimizing the therapeutic efficacy of the liposomal drug delivery. This work utilizes the platform of [(111)In]-Liposome as a drug delivery vehicle, encapsulating a novel (18)F-labeled carboplatin drug derivative ([(18)F]-FCP) as a dual-molecular imaging tool as both a radiolabeled drug and radiolabeled carrier. The approach has the potential for clinical translation in individual patients using a dual modal approach of clinically-relevant radionuclides of (18)F positron emission tomography (PET) and (111)In single photon emission computed tomography (SPECT). [(111)In]-Liposome was synthesized and evaluated in vivo by biodistribution and SPECT imaging. The [(18)F]-FCP encapsulated [(111)In]-Liposome nano-construct was investigated, in vivo, using an optimized dual-tracer PET and SPECT imaging in a nude mouse. The biodistribution data and SPECT imag...
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Journal of controlled release : official journal of the Controlled Release Society, 2018
Liposomes are nanoparticles used in drug delivery that distribute over several days in humans and larger animals. Radiolabeling with long-lived positron emission tomography (PET) radionuclides, such as manganese-52 (52Mn, T½=5.6days), allow the imaging of this biodistribution. We report optimized protocols for radiolabeling liposomes with 52Mn, through both remote-loading and surface labeling. For comparison, liposomes were also remote-loaded and surface labeled with copper-64 (64Cu, T½=12.7h) through conventional means. The chelator DOTA was used in all cases. The in vivo stability of radiometal chelates is widely debated but studies that mimic a realistic in vivo setting are lacking. Therefore, we employed these four radiolabeled liposome types as platforms to demonstrate a new concept for such in vivo evaluation, here of the chelates 52Mn-DOTA and 64Cu-DOTA. This was done by comparing "shielded" remote-loaded with "exposed" surface labeled variants in a CT26 t...
Journal of Drug Delivery Science and Technology, 2019
Cancer is the major burden of disease worldwide. The folate receptor, as a specific tumor target, is over-expressed in many types of cancer including ovarian carcinomas, breast, colon, renal, and lung tumors. Nuclear medicine hybrid imaging modalities, such as SPECT/CT, provide both metabolic and anatomic information. Therefore, specific contrast agents are essentially needed. Liposomes are favorable systems with many advantages. The aim of this study was to formulate liposomal imaging agents for molecular tumor imaging by SPECT or SPECT/CT and evaluate their efficacy. Nanosized, polyethyleneglycolated, folate-conjugated and unmodified, diethylenetriaminepentaacetic acid-phosphatidylethanolamine containing, neutral and positively charged liposomes were formulated and characterized by mean particle size, zeta potential, and quantitative determination of the phospholipids in the liposomes. The binding of the synthetized imaging agents to 4T1 breast tumor cells was evaluated by fluorescence microscopy and radioactivity counting. Folate-conjugated neutral and positively charged liposomes were found to be effective as tumor imaging agents exhibiting an almost 3-fold increased uptake and brighter fluorescence microscopy images than unmodified ones in in vitro experiments using 4T1 breast tumor cells. These results could be considered as an important step towards the development of folate-specific agents for tumor imaging by SPECT and SPECT/CT.
Bioconjugate Chemistry, 2008
Radiolabeling of liposomes with 64 Cu (t 1/2 = 12.7 h) is attractive for molecular imaging and monitoring drug delivery. A simple chelation procedure, performed at a low temperature and under mild conditions, is required to radiolabel pre-loaded liposomes without lipid hydrolysis or the release of the encapsulated contents. Here we report a 64 Cu post-labeling method for liposomes. A 64 Cuspecific chelator, 6-[p-(bromoacetamido)benzyl]-1,4,8,11-tetraazacyclotetradecane-N,N',N",N"'tetraacetic acid (BAT), was conjugated with an artificial lipid to form a BAT-PEG-lipid. After incorporation of 0.5% (mol/mol) BAT-PEG-lipid during the liposome formulation, liposomes were successfully labeled with 64 Cu in 0.1 M NH 4 OAc pH 5 buffer, at 35 °C for 30~40 min with an incorporation yield as high as 95%. After 48 hour incubation of 64 Cu-liposomes in 50/50 serum/PBS solution, more than 88% of the 64 Cu label was still associated with liposomes. After injection of liposomal 64 Cu in a mouse model, 44 ± 6.9, 21 ± 2.7, 15 ± 2.5, and 7.4 ± 1.1 (n = 4) % of the injected dose per cubic centimeter remained within the blood pool at 30 min, 18, 28, and 48 hours, respectively. The biodistribution at 48 hours after injection verified that 7.0 ± 0.47 (n = 4), and 1.4 ± 0.58 (n = 3) % of the injected dose per gram of liposomal 64 Cu and free 64 Cu remained in the blood pool, respectively. Our results suggest that this fast and easy 64 Cu labeling of liposomes could be exploited in tracking liposomes in vivo for medical imaging and targeted delivery.