64Cu loaded liposomes as positron emission tomography imaging agents (original) (raw)
Related papers
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.
Theranostics, 2018
Deposition of liposomal drugs into solid tumors is a potentially rate-limiting step for drug delivery and has substantial variability that may influence probability of response. Tumor deposition is a shared mechanism for liposomal therapeutics such that a single companion diagnostic agent may have utility in predicting response to multiple nanomedicines. We describe the development, characterization and preclinical proof-of-concept of the positron emission tomography (PET) agent, MM-DX-929, a drug-free untargeted 100 nm PEGylated liposome stably entrapping a chelated complex of 4-DEAP-ATSC and Cu (copper-64). MM-DX-929 is designed to mimic the biodistribution of similarly sized therapeutic agents and enable quantification of deposition in solid tumors. MM-DX-929 demonstrated sufficient and stability with PET images accurately reflecting the disposition of liposome nanoparticles over the time scale of imaging. MM-DX-929 is also representative of the tumor deposition and intratumoral ...
Remote Loading of 64 Cu 2+ into Liposomes without use of Ion Transport Enhancers
ACS Applied Materials & Interfaces, 2015
Due to low ion permeability of lipid bilayers, it has been and still is common practice to use transporter molecules such as ionophores or lipophilic chelators to increase trans-membrane diffusion rates and loading efficiencies of radionuclides into liposomes. Here, we report a novel and very simple method for loading the positron emitter 64 Cu 2+ into liposomes, which is important for in vivo positron emission tomography (PET) imaging. By this approach, copper is added to liposomes entrapping a chelator, which causes spontaneous diffusion of copper across the lipid bilayer where it is trapped. Using this method, we achieve highly efficient 64 Cu 2+ loading, high radionuclide retention, and favorable loading kinetics, excluding use of transporter molecule additives. We investigate the molecular coordination of entrapped copper using X-ray absorption spectroscopy, and demonstrate high adaptability of the loading method to different lipid formulations. We demonstrate high in vivo stability of 64 Cu-liposomes in a canine cancer model and evaluate tumor accumulation in mice using PET imaging. With this work, it is demonstrated that copper ions are capable of crossing a lipid membrane unassisted. This method is highly valuable for characterizing in vivo performance of liposome-based nanomedicine with great potential in diagnostic imaging applications.
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...
Theranostics
Long circulating liposomes entrapping iodinated and radioiodinated compounds offer a highly versatile theranostic platform. Here we report a new methodology for efficient and high-yielding loading of such compounds into liposomes, enabling CT/SPECT/PET imaging and 131 I-radiotherapy. Methods: The CT contrast agent diatrizoate was synthetically functionalized with a primary amine, which enabled its remote loading into PEGylated liposomes by either an ammonium sulfate or a citrate based pH transmembrane gradient. Further, the amino-diatrizoate was radiolabeled with either 124 I (t1/2 = 4.18 days) for PET or 125 I (t1/2 = 59.5 days) for SPECT, through an aromatic Finkelstein reaction. Results: Quantitative loading efficiencies (>99%) were achieved at optimized conditions. The 124 I-labeled compound was remote-loaded into liposomes, with an overall radiolabeling efficiency of 77 ± 1%, and imaged in vivo in a CT26 murine colon cancer tumor model by PET/CT. A prolonged blood circulation half-life of 19.5 h was observed for the radiolabeled liposomes, whereas injections of the free compound were rapidly cleared. Lower accumulation was observed in the spleen, liver, kidney and tumor than what is usually seen for long-circulating liposomes. Conclusion: The lower accumulation was interpreted as release of the tracer from the liposomes within these organs after accumulation. These results may guide the design of systems for controlled release of remote loadable drugs from liposomes.
The use and importance of liposomes in Positron Emission Tomography
Drug Delivery, 2012
Among different imaging modalities, Positron Emission Tomography (PET) gained importance in routine hospital practice depending on ability to diagnose diseases in early stages and tracing of therapy by obtaining metabolic information. The combination of PET with Computed Tomography (CT) forms hybrid imaging modality that gives chance to obtain better images having higher resolution by fusing both functional and anatomical images in the same imaging modality at the same time. Therefore, better contrast agents are essentially needed. The advance in research about developing drug delivery systems as specific nanosized targeted systems gained an additional importance for obtaining better diagnosis and therapy of different diseases. Liposomes appear to be more attractive drug delivery systems in delivering either drugs or imaging ligands to target tissue or organ of diseases with higher accumulation by producing in nano-scale, long circulating by stealth effect and specific targeting by modifying with specific ligands or markers. The combination of positron emitting radionuclides with liposomes are commonly in research level nowadays and there is no commercially available liposome formulation for PET imaging. However by conjugating positron emitter radionuclide with liposomes can form promising diagnostic agents for improved diagnosis and following up treatments by increasing image signal/contrast in the target tissue in lower concentrations by specific targeting as the most important advantage of liposomes. More accurate and earlier diagnosis of several diseases can be obtained even in molecular level with the use of stable and effectively radiolabeled molecular target specific nano sized liposomes with longer half-lived positron emitting radionuclides.
2016
The clinical value of current and future nanomedicines can be improved by introducing patient selection strategies based on noninvasive sensitive whole-body imaging techniques such as positron emission tomography (PET). Thus, a broad method to radiolabel and track preformed nanomedicines such as liposomal drugs with PET radionuclides will have a wide impact in nanomedicine. Here, we introduce a simple and efficient PET radiolabeling method that exploits the metal-chelating properties of certain drugs (e.g., bisphosphonates such as alendronate and anthracyclines such as doxorubicin) and widely used ionophores to achieve excellent radiolabeling yields, purities, and stabilities with 89 Zr, 52 Mn, and 64 Cu, and without the requirement of modification of the nanomedicine components. In a model of metastatic breast cancer, we demonstrate that this technique allows quantification of the biodistribution of a radiolabeled stealth liposomal nanomedicine containing alendronate that shows high uptake in primary tumors and metastatic organs. The versatility, efficiency, simplicity, and GMP compatibility of this method may enable submicrodosing imaging studies of liposomal nanomedicines containing chelating drugs in humans and may have clinical impact by facilitating the introduction of image-guided therapeutic strategies in current and future nanomedicine clinical studies.
ACS nano, 2015
Since the first report of the enhanced permeability and retention (EPR) effect, the research in nanocarrier based anti-tumor drugs has been intense. The field has been devoted to treatment of cancer by exploiting EPR-based accumulation of nanocarriers in solid tumors, which for many years was considered to be a ubiquitous phenomenon. However, the understanding of differences in the EPR-effect between tumor types, heterogeneities within each patient group, and dependency on tumor development stage in humans is sparse. It is therefore important to enhance our understanding of the EPR-effect in large animals and humans with spontaneously developed cancer. In the present paper, we describe a novel loading method of copper-64 into PEGylated liposomes and use these liposomes to evaluate the EPR-effect in 11 canine cancer patients with spontaneous solid tumors by PET/CT imaging. We thereby provide the first high-resolution analysis of EPR-based tumor accumulation in large animals. We find ...
Copper-64 labeled liposomes for imaging bone marrow
Nuclear Medicine and Biology, 2016
Introduction-Bone marrow is the soft tissue compartment inside the bones made up of hematopoietic cells, adipocytes, stromal cells, phagocytic cells, stem cells, and sinusoids. While [ 18 F]-FLT has been utilized to image proliferative marrow, to date, there are no reports of particle based positron emission tomography (PET) imaging agents for imaging bone marrow. We have developed copper-64 labeled liposomal formulation that selectively targets bone marrow and therefore serves as an efficient PET probe for imaging bone marrow. Methods-Optimized liposomal formulations were prepared with succinyl PE, DSPC, cholesterol, and mPEG-DSPE (69:39:1:10:0.1) with diameters of 90 and 140 nm, and were doped with DOTA-Bn-DSPE for stable 64 Cu incorporation into liposomes. Results-PET imaging and biodistribution studies with 64 Cu-labeled liposomes indicate that accumulation in bone marrow was as high as 15.18 ± 3.69 %ID/g for 90 nm liposomes and 7.01 ± 0.92 %ID/g for 140 nm liposomes at 24 h post-administration. In vivo biodistribution studies in tumor-bearing mice indicate that the uptake of 90 nm particles is approximately 0.89 ± 0.48 %ID/g in tumor and 14.22 ± 8.07 %ID/g in bone marrow, but respective values for Doxil® like liposomes are 0.83 ± 0.49 %ID/g and 2.23 ± 1.00 %ID/g.
Journal of Controlled Release, 2011
Changes in lipid acyl chain length can result in desorption of lipid from the liposomal anchorage and interaction with blood components. PET studies of the stability of such lipids have not been performed previously although such studies can map the pharmacokinetics of unstable lipids noninvasively in vivo. The purpose of this study was to characterize the in vivo clearance of 64 Culabeled distearoyl-and dipalmitoyl lipid included within long circulating liposomes. Distearoyl and dipalmitoyl maleimide lipids (1 mol%) in liposomes were labeled with a 64 Cu-incorporated bifunctional chelator (TETA-PDP) after the activation of pyridine disulfide to thiol by TCEP. Long circulating liposomes containing HSPC:DSPE-PEG2k-OMe:cholesterol: x (55:5:39:1), where x was 64 Cu-DSPE or 64 Cu-DPPE, or HSPC:DSPE-PEG2k-OMe:cholesterol: 64 Cu-DSPE:DPPC (54:5:39:1:1) were evaluated in serum (in vitro) and via intravenous injection to FVB mice. The time activity curves for the blood, liver, and kidney were measured from PET images and the biodistribution was performed at 48 hours. In vitro assays showed that 64 Cu-DPPE transferred from liposomes to serum with a 7.9 hour half-life but 64 Cu-DSPE remained associated with the liposomes. The half clearance of radioactivity from the blood pool was 18 and 5 hours for 64 Cu-DSPE-and 64 Cu-DPPE liposome-injected mice, respectively. The clearance of radioactivity from the liver and kidney was significantly greater following the injection of 64 Cu-DPPE-labelled liposomes than 64 Cu-DSPE-labelled liposomes at 6, 18 and 28 hours. Forty eight hours after injection, the whole body radioactivity was 57 and 17% ID/cc for 64 Cu-DSPE and 64 Cu-DPPE, respectively. These findings suggest that the acyl chain length of the radiolabel should be considered for liposomal PET studies and that PET is an effective tool for evaluating the stability of nanoformulations in vivo.