Mediastinal node and diaphragmatic targeting after intracavitary injection of avidin/99mTc-blue-biotin-liposome system

Radiolabeled liposomes and lipoproteins as lipidic nanoparticles for imaging and therapy

Radiolabeled lipidic nanoparticles, particularly liposomes and lipoproteins, are of great interest as agents for imaging and therapy, due not only to their peculiar physicochemical and biological properties, but also to their great versatility and the ability to manipulate them to obtain the desired properties. This review provides an overview of radionuclide labeling strategies for preparing diagnostic and therapeutic nanoparticles based on liposomes and lipoproteins that have been developed to date, as well as the main quality control methods and in vivo applications.

Prolonged retention of liposomes in the pleural cavity of normal mice and high tumor distribution in mice with malignant pleural effusion, after intrapleural injection

Background: Intrapleural administration of compounds is a lung targeted, innovative therapeutic strategy for mesothelioma, which can be refined as a route for drug delivery that minimizes the potential for systemic toxicity. However, little is currently known about the retention of liposomal drugs at the site, after such topical administration. Purpose: To evaluate the retention of liposomes in lungs following intrapleural injection, and how this might be modulated by liposome properties and disease progression. Methods: DiR-incorporating liposomes with various lipid compositions and sizes were prepared, characterized (for size distribution and zeta potential) and injected intrapleurally in normal mice and mice with malignant pleural effusion (MPE). DiR retention in pleural cavity was followed by biofluorescence imaging. Results: Experimental results demonstrate that liposome size and PEG-coating, have a significant effect on residence time in the pleural cavity; negative surface charge does not. More than 20% liposomal-DiR is retained 24 d post-injection (in some cases), indicating the high potential towards localized diseases. Ex-vivo liposomal-DiR signal in tumors of MPE mice was similar to signal in liver, suggesting high tumor targeting potential of intrapleurally injected liposomes. Finally, no difference was noticed in liposomal-DiR retention between tumor-inoculated (MPE) and healthy mice, indicating the stability of liposomes in the presence of effusion (in MPE mice). Conclusion: The current study provides novel insights for using liposomes by intrapleural administration for the treatment of lung diseases.

Techniques for Loading Technetium-99m and Rhenium-186/188 Radionuclides into Preformed Liposomes for Diagnostic Imaging and Radionuclide Therapy

Liposomes can serve as carriers of radionuclides for diagnostic imaging and therapeutic applications. Herein, procedures are outlined for radiolabeling liposomes with the gamma-emitting radionuclide, technetium-99m (^99mTc), for noninvasive detection of disease and for monitoring the pharmacokinetics and biodistribution of liposomal drugs, and/or with therapeutic beta-emitting radionuclides, rhenium-186/188 (^186/188Re), for radionuclide therapy. These efficient and practical liposome radiolabeling methods use a post-labeling mechanism to load ^99mTc or ^186/188Re into preformed liposomes prepared in advance of the labeling procedure. For all liposome radiolabeling methods described, a lipophilic chelator is used to transport ^99mTc or ^186/188Re across the lipid bilayer of the preformed liposomes. Once within the liposome interior, the pre-encapsulated glutathione or ammonium sulfate (pH) gradient provides for stable entrapment of the ^99mTc and ^186/188Re within the liposomes. In the first method, ^99mTc is transported across the lipid bilayer by the lipophilic chelator, hexamethylpropyleneamine oxime (HMPAO) and ^99mTc-HMPAO becomes trapped by interaction with the pre-encapsulated glutathione within the liposomes. In the second method, ^99mTc or ^186/188Re is transported across the lipid bilayer by the lipophilic chelator, N,N-bis(2-mercaptoethyl)-N',N'-diethylethylenediamine (BMEDA), and ^99mTc-BMEDA or ^186/188Re-BMEDA becomes trapped by interaction with pre-encapsulated glutathione within the liposomes. In the third method, an ammonium sulfate (pH) gradient loading technique is employed using liposomes with an extraliposomal pH of 7.4 and an interior pH of 5.1. BMEDA, which is lipophilic at pH 7.4, serves as a lipophilic chelator for ^99mTc or ^186/188Re to transport the radionuclides across the lipid bilayer. Once within the more acidic liposome interior, ^99mTc/^186/188Re-BMEDA complex becomes protonated and more hydrophilic, which results in stable entrapment of the ^99mTc/^186/188Re-BMEDA complex within the liposomes. Since many commercially available liposomal drugs use an ammonium sulfate (pH) gradient for drug loading, these liposomal drugs can be directly radiolabeled with ^99mTc-BMEDA for noninvasive monitoring of tissue distribution during treatment or with ^186/188Re-BMEDA for combination chemo-radionuclide therapy.

Current and future lymphatic imaging modalities for tumor staging

Tumor progression is supported by the lymphatic system which should be scanned efficiently for tumor staging as well as the enhanced therapeutic outcomes. Poor resolution and low sensitivity is a limitation of traditional lymphatic imaging modalities; thus new noninvasive approaches like nanocarriers, magnetic resonance imaging, positron-emission tomography, and quantum dots are advantageous. Some newer modalities, which are under development, and their potential uses will also be discussed in this review.

Targeted delivery into motor nerve terminals of inhibitors for SNARE-cleaving proteases via liposomes coupled to an atoxic botulinum neurotoxin

A targeted drug carrier (TDC) is described for transferring functional proteins or peptides into motor nerve terminals, a pivotal locus for therapeutics to treat neuromuscular disorders. It exploits the pronounced selectivity of botulinum neurotoxin type B (BoNT/B) for interacting with acceptors on these cholinergic nerve endings and becoming internalized. The gene encoding an innocuous BoNT/B protease-inactive mutant (BoTIM) was fused to that for core streptavidin, expressed in Escherichia coli and the purified protein was conjugated to surface-biotinylated liposomes. Such decorated liposomes, loaded with fluorescein as traceable cargo, acquired pronounced specificity for motor nerve terminals in isolated mouse hemidiaphragms and facilitated the intraneuronal transfer of the fluor, as revealed by confocal microscopy. Delivery of the protease light chain of botulinum neurotoxin type A (BoNT/A) via this TDC accelerated the onset of neuromuscular paralysis, indicative of improved translocation of this enzyme into the presynaptic cytosol with subsequent proteolytic inactivation of synaptosomal-associated protein of molecular mass 25 kDa (SNAP-25), an exocytotic soluble N-ethyl-maleimide-sensitive factor attachment protein receptor (SNARE) essential for neurotransmitter release. BoTIM-coupled liposomes, loaded with peptide inhibitors of proteases, yielded considerable attenuation of the neuroparalytic effects of BoNT/A or BoNT/F as a result of their cytosolic transfer, the first in situ demonstration of the ability of designer antiproteases to suppress the symptoms of botulism ex vivo. Delivery of the BoNT/A inhibitor by liposomes targeted with the full-length BoTIM proved more effective than that mediated by its C-terminal neuroacceptor-binding domain. This demonstrated versatility of TDC for nonviral cargo transfer into cholinergic nerve endings has unveiled its potential for direct delivery of functional targets into motor nerve endings.

Lymphatic drug delivery using engineered liposomes and solid lipid nanoparticles

The lymphatic system plays a crucial role in the immune system's recognition and response to disease, and most solid cancers initially spread from the primary site via the tumor's surrounding lymphatics before hematological dissemination. Hence, the lymphatic system is an important target for developing new vaccines, cancer treatments, and diagnostic agents. Targeting the lymphatic system by subcutaneous, intestinal, and pulmonary routes has been evaluated and subsequently utilized to improve lymphatic penetration and retention of drug molecules, reduce drug-related systemic toxicities, and enhance bioavailability of poorly soluble and unstable drugs. Lymphatic imaging is an essential tool for the detection and staging of cancer. New nano-based technologies offer improved detection and characterization of the nodal diseases, while new delivery devices can better target and confine treatments to tumors within the nodal space while sparing healthy tissues. This manuscript reviews recent advances in the field of lymphatic drug delivery and imaging and focuses specifically on the development of liposomes and solid lipid nanoparticles for lymphatic introduction via the subcutaneous, intestinal, and pulmonary routes.

Techniques for loading technetium-99m and rhenium-186/188 radionuclides into pre-formed liposomes for diagnostic imaging and radionuclide therapy

Liposomes can serve as carriers of radionuclides for diagnostic imaging and therapeutic applications. Herein, procedures are outlined for radiolabeling liposomes with the gamma-emitting radionuclide, technetium-99m ((99m)Tc), for non-invasive detection of disease and for monitoring the pharmacokinetics and biodistribution of liposomal drugs, and/or with therapeutic beta-emitting radionuclides, rhenium-186/188 ((186/188)Re), for radionuclide therapy. These efficient and practical liposome radiolabeling methods use a post-labeling mechanism to load (99m)Tc or (186/188)Re into pre-formed liposomes prepared in advance of the labeling procedure. For all liposome radiolabeling methods described, a lipophilic chelator is used to transport (99m)Tc or (186/188)Re across the lipid bilayer of the pre-formed liposomes. Once within the liposome interior, the pre-encapsulated glutathione or ammonium sulfate (pH) gradient provides for stable entrapment of the (99m)Tc and (186/188)Re within the liposomes. In the first method, (99m)Tc is transported across the lipid bilayer by the lipophilic chelator, hexamethylpropyleneamine oxime (HMPAO) and (99m)Tc-HMPAO becomes trapped by interaction with the pre-encapsulated glutathione within the liposomes. In the second method, (99m)Tc or (186/188)Re is transported across the lipid bilayer by the lipophilic chelator, N,N-bis(2-mercaptoethyl)-N',N'-diethylethylenediamine (BMEDA), and (99m)Tc-BMEDA or (186/188)Re-BMEDA becomes trapped by interaction with pre-encapsulated glutathione within the liposomes. In the third method, an ammonium sulfate (pH) gradient loading technique is employed using liposomes with an extraliposomal pH of 7.4 and an interior pH of 5.1. BMEDA, which is lipophilic at pH 7.4, serves as a lipophilic chelator for (99m)Tc or (186/188)Re to transport the radionuclides across the lipid bilayer. Once within the more acidic liposome interior, (99m)Tc/(186/188)Re-BMEDA complex becomes protonated and more hydrophilic, which results in stable entrapment of the (99m)Tc/(186/188)Re-BMEDA complex within the liposomes. Since many commercially available liposomal drugs use an ammonium sulfate (pH) gradient for drug loading, these liposomal drugs can be directly radiolabeled with (99m)Tc-BMEDA for non-invasive monitoring of tissue distribution during treatment or with (186/188)Re-BMEDA for combination chemo-radionuclide therapy.

Imaging of 186Re-liposome therapy in ovarian cancer xenograft model of peritoneal carcinomatosis

This study determined the biodistribution of rhenium-186 ((186)Re) encapsulated in biotin-liposomes containing patent blue dye, injected intraperitoneally (IP) with avidin in an OVCAR-3 ovarian cancer xenograft model and evaluated tumor response of this therapy with fluorine-18-fluorodeoxyglucose ((18)F-FDG) microPET imaging. Treated rats (n = 8) received an IP injection of (186)Re-blue-biotin-liposomes (1000 MBq/kg) 30 min before an IP injection of avidin (5 mg), whereas control rats (n = 4) received a sham IP injection of saline. Scintigraphic images showed that (186)Re-blue-biotin liposomes/avidin were retained in the peritoneal cavity with 18% of the original activity remaining after 5 days. From 1 to 4 weeks post-treatment, peritoneal (18)F-FDG standard uptake values decreased 30% in treatment group, yet increased 44% in control group. Total number of cells in ascites was significantly higher in control versus treatment group. Omental fat in control rats had numerous tumor cells compared with treated rats. Results show the potential for (186)Re-blue-biotin-liposome/avidin system in treating advanced ovarian cancer involving peritoneal carcinomatosis.

Use of avidin/biotin-liposome system for enhanced peritoneal drug delivery in an ovarian cancer model

The goal of this study was to determine the distribution of the avidin/biotin-liposome system in an ovarian cancer xenograft model. Optimal avidin/biotin-liposome injection sequence with enhanced liposome accumulation to the peritoneum was determined. Two weeks after NIH:OVCAR-3 cell inoculation, rats were divided into three groups. Group 1 (B-A) (n=4), received an intraperitoneal injection of (99m)Tc-blue-biotin-liposomes 30 min before an intraperitoneal injection of avidin. Group 2 (A-B) (n=4), received an intraperitoneal injection of avidin 30 min before an intraperitoneal injection of (99m)Tc-blue-biotin-liposomes. Group 3 (A-B 2h) (n=5), received an intraperitoneal injection of avidin 2h before an intraperitoneal injection of (99m)Tc-blue-biotin-liposomes. Three additional non-tumor nude rats served as controls in each group, and were subjected to the same injection sequences. Scintigraphic imaging commenced at various times post (99m)Tc-blue-biotin-liposome injection. After imaging, rats were euthanized at 23 h post-liposome injection for tissue biodistribution. Images showed no apparent difference in liposome distribution between control and tumor animals. Regional uptake analysis at 4h for tumor rats showed significantly higher lymphatic channel uptake in the A-B 2h group (p<0.05) and a trend of increased peritoneal uptake in A-B group. By 22 h, peritoneal and lymphatic channel uptake was similar for all groups. At necropsy, most activity was found in blue-stained omentum, diaphragm, mediastinal and abdominal nodes. Bowel activity was minimal. These results correlate with previous normal rat studies, and demonstrate potential use of this avidin/biotin-liposome system for prolonging drug delivery to the peritoneal cavity and associating lymph nodes in this ovarian cancer xenograft model.

SPECT/CT imaging of baculovirus biodistribution in rat

Non-invasive imaging provides essential information regarding the biodistribution of gene therapy vectors and it can also be used for the development of targeted vectors. In this study, we have utilized micro Single-photon emission computed tomography to visualize biodistribution of a (99m)Tc-polylys-ser-DTPA-biotin-labelled avidin-displaying baculovirus, Baavi, after intrafemoral (i.f.), intraperitoneal (i.p.), intramuscular (i.m.) and intracerebroventricular (i.c.v.) administration. The imaging results suggest that the virus can spread via the lymphatic network after different administration routes, also showing accumulation in the nasal area after systemic administration. Extensive expression in the kidneys and spleen was seen after i.p. administration, which was confirmed by reverse transcriptase-polymerase chain reaction and immunohistochemistry. Additionally, transduction of kidneys was seen with i.m. and i.f. administrations. We conclude that baculovirus may be beneficial for the treatment of kidney diseases after i.p. administration route.