Body Biodistribution Research Articles

Highly hydrophilic methacrylamide-based copolymers as precursors for polymeric nanomedicines containing anthracyclines

The crucial limitation of most low molecular weight cytostatic drugs, including anthracyclines, is their nonspecific biodistribution causing severe adverse effects during cancer treatment. Recently, nanomedicines such as polymer-based systems have been developed as advanced drug delivery systems. Herein, we report the design, synthesis, and characterization of highly water-soluble polymer-carriers based on N‑(1,3‑dihydroxyprop-2-yl)methacrylamide (DHPMA). Polymers differing in molecular weight, hydrodynamic size, and dispersity were synthesized via free or controlled radical polymerization and conjugated to an anthracycline drug pirarubicin (THP) via a pH-sensitive hydrazone bond achieving up to 21 wt% of THP. The DHPMA copolymers were extensively compared to the well-known drug delivery vectors, N-(2-hydroxypropyl)methacrylamide (HPMA)-based copolymers. Importantly, DHPMA-based conjugates showed excellent hydrophilicity exceeding that of HPMA-based copolymers and did not aggregate even after loading with THP reaching 21 wt%. The DHPMA-based polymer nanomedicines exhibited excellent cytotoxicity, body biodistribution, tumor accumulation, and antitumor efficacy, significantly reducing the side effects and toxicity comparable to HPMA-based systems, thus demonstrating their applicability and suitability as efficient drug carriers.

Biodistribution and radiation dosimetry of multiple tracers on total-body positron emission tomography/computed tomography.

[18F]F-FDG, [68Ga]Ga-PSMA-11, and [68Ga]Ga-FAPI-04 have achieved good results in multiple clinical trials and clinical practice, but the imaging of these tracers is limited to traditional short-axis positron emission tomography/computed tomography (PET/CT). Therefore, we aimed to use total-body PET/CT dynamic scanning to describe whole-body biodistribution of these three tracers and to calculate more precise radiation doses. Total-body PET/CT (uExplorer, United Imaging Healthcare) dynamic scanning was performed on 54 patients, including 30 patients with [18F]F-FDG, 10 patients with [68Ga]Ga-PSMA-11, and 14 patients with [68Ga]Ga-FAPI-04. A 60-minute dynamic scanning of whole body was performed simultaneously after bedside bolus injection of the corresponding tracers. The dynamic sequence of 92 frames was quantitatively analyzed by the Pmod4.0 software. Whole body biodistribution was calculated as time-activity curves (TACs) describing dynamic uptake patterns in the subject's major organs, followed by calculation of tracer kinetics and cumulative organ activity. Finally, combined with the OLINDA/EXM software, effective doses of the different tracers and individual organ doses were calculated. In a systematic TAC analysis of three tracers, we identified distinct biodistribution patterns in major organs. [68Ga]Ga-PSMA-11 showed a trend of rapid increasing and slow decreasing in liver, spleen, muscle, and bone. In the heart, stomach, brain, and lung, tracer decreased rapidly after rapid increasing. Similarly, tracer uptake in the kidney and urinary bladder increased gradually. [68Ga]Ga-FAPI-04 showed a rapid increasing and rapid decreasing trend in brain, lung, liver, spleen, bone, heart, kidney, and stomach. The mean effective dose of [68Ga]Ga-PSMA-11 was 1.47E-02 mSv/MBq, and the mean effective doses of [18F]F-FDG and [68Ga]Ga-FAPI-04 were comparable (2.52E-02 mSv/MBq and 2.23E-02 mSv/MBq). The mean effective dose of [18F]F-FDG was lower than that reported in the literature measured by previous short-axis PET, while both [68Ga]Ga-PSMA-11 and [68Ga]Ga-FAPI-04 had higher value than previously reported value. [18F]F-FDG, [68Ga]Ga-PSMA-11 and [68Ga]Ga-FAPI-04 have good biodistribution in human organs. Real-time high-sensitivity dynamic scanning with total-body PET/CT is a very effective way to accurately calculate biodistribution and effective dose of positron-labeled radiopharmaceuticals.

Determination of the bioavailability and biodistribution of a single dose of oral cholecalciferol/Calcirol® soft gelatin capsule by pharmacoscintigraphy- CalSci study

Background: It is required to study the bioavailability and biodistribution of specific cholecalciferol formulation before prescribing. Pharmacoscintigraphy is an established radiological-imaging technique that is used to map various drug formulations as they traverses the human body (biodistribution) in real-time. We evaluated the bioavailability and biodistribution pattern, transit time, and gastrointestinal clearance of a single dose of Calcirol® soft gelatin capsule 60,000 IU [an oral cholecalciferol (vitamin D) formulation] using pharmacoscintigraphy. Methods: Six male healthy adult volunteers were administered a single oral dose of Calcirol® soft gelatin capsule labelled with technetium-99m. Post-dosing, serial venous blood samples were collected till day 27 for the estimation of the plasma levels of 25-hydroxycholecalciferol and 1,25-dihydroxycholecalciferol levels. Different pharmacokinetic parameters were calculated. Sequential static gamma imaging was performed to evaluate the biodistribution of Calcirol® soft gelatin capsule. Descriptive statistics was used. Various pharmacokinetic parameters were calculated from the concentration-time curves. Statistical analysis was carried out using Student’s t-test. Suitable multivariate analysis was performed based on the distribution of data. All statistical analyses were performed using SAS® Software (v 9.4). Results: The overall absorption of Calcirol® soft gelatin capsule was 93.23%, which was fully from the small intestine. It led to achieving a sufficient level of 25-hydroxycholecalciferol (>60 ng/ml) within 6 hours of oral intake. The levels of plasma 25-hydroxycholecalciferol and 1,25-dihydroxycholecalciferol increased (maximum around 6 and 18 days, respectively). The small intestinal residence time was around 16 hours. No adverse event was noted. Conclusions: This was the first pharmacoscintigraphy study in the world which demonstrated the favourable bio-distribution of the Calcirol softgels supporting its role in vitamin D supplementation.

Intravenous and oral whole body ketone dosimetry, biodistribution, metabolite correction and kinetics studied by (R)-[1-11C]β-hydroxybutyrate ([11C]OHB) PET in healthy humans

BackgroundKetones are increasingly recognized as an important and possibly oxygen sparing source of energy in vital organs such as the heart, the brain and the kidneys. Drug treatments, dietary regimens and oral ketone drinks designed to deliver ketones for organ and tissue energy production have therefore gained popularity. However, whether ingested ketones are taken up by various extra-cerebral tissues and to what extent is still largely unexplored. It was therefore the aim of this study to use positron emission tomography (PET) to explore the whole body dosimetry, biodistribution and kinetics of the ketone tracer (R)-[1-11C]β-hydroxybutyrate ([11C]OHB). Six healthy subjects (3 women and 3 men) underwent dynamic PET studies after both intravenous (90 min) and oral (120 min) administration of [11C]OHB. Dosimetry estimates of [11C]OHB was calculated using OLINDA/EXM software, biodistribution was assessed visually and [11C]OHB tissue kinetics were obtained using an arterial input function and tissue time-activity curves.ResultsRadiation dosimetry yielded effective doses of 3.28 upmuSv/MBq (intravenous administration) and 12.51 upmuSv/MBq (oral administration). Intravenous administration of [11C]OHB resulted in avid radiotracer uptake in the heart, liver, and kidneys, whereas lesser uptake was observed in the salivary glands, pancreas, skeletal muscle and red marrow. Only minimal uptake was noted in the brain. Oral ingestion of the tracer resulted in rapid radiotracer appearance in the blood and radiotracer uptake in the heart, liver and kidneys. In general, [11C]OHB tissue kinetics after intravenous administration were best described by a reversible 2-tissue compartmental model.ConclusionThe PET radiotracer [11C]OHB shows promising potential in providing imaging data on ketone uptake in various physiologically relevant tissues. As a result, it may serve as a safe and non-invasive imaging tool for exploring ketone metabolism in organs and tissues of both patients and healthy individuals.Trial registrationClinical trials, NCT0523812, Registered February 10th 2022, https://clinicaltrials.gov/ct2/show/NCT05232812?cond=NCT05232812&draw=2&rank=1.

Pilot study on 11C-CFT dynamic imaging using total-body PET/CT: biodistribution and radiation dosimetry in Parkinson's disease.

Total-body PET/CT equipment, uEXPLORER, is a newly developed imaging technology with a superior resolution, high sensitivity, and high signal-to-noise ratio, providing unique application advantages in the pharmacokinetic evaluation of positron tracers. While 11C-CFT PET/CT has been widely utilized in the early diagnosis of Parkinson's disease (PD), it is limited by the short half-life of the radionuclide and an incomplete understanding of its biological distribution in humans. This study aimed to use a total-body PET/CT dynamic scan with 11C-CFT imaging to describe the real-time internal biodistribution in PD patients and to obtain accurate radiation dosimetry. Six male subjects with suspected PD underwent dynamic 11C-CFT total-body PET/CT. Following a bedside intravenous bolus injection of 373.3 ± 71.56 MBq of 11C-CFT, PET acquisition was performed synchronously for 75 min with a maximum axial field of view (AFOV) of 194 cm. Time-activity curves (TACs) were generated by delineating volumes of interest (VOIs) of the sourced organs using PMOD software. Tracer kinetics and cumulative organ activities were calculated, and absorbed doses were calculated and estimated using the OLINDA/EXM software. In the systemic TAC analysis of 11C-CFT, several unique types of distribution patterns were obtained among several major organs, including a "Fast-in Fast-out" pattern in the kidneys, lungs, spleen, and thyroid, a "Fast-in Slow-out" curve in the heart wall, a "Slow-in Slow-out" mode in the liver, a "Low-level extending" pattern in the whole brain and muscle, and a "Slow-in to plateau" trend in the striatum and bone. The effective dose of 11C-CFT was calculated to be 2.83E-03 mSv/MBq, which is only one-third of the literature value measured by the conventional method. Moreover, this dose is much lower compared to all other doses of DAT radioligands used in PET imaging. This study is a pioneering application of total-body PET/CT to 11C-CFT dynamic imaging. Our results confirmed that 11C-CFT has a favorable total body biodistribution, an extremely low internal radiation dose, and high imaging quality, making it suitable for reasonable PD diagnosis in patients requiring multiple follow-up examinations.

Abstract 14256: Dual-Targeted NIRF Molecular Imaging Combined With Intravascular OCT for Inflammatory Micro-Calcification in the High-Risk Plaque

Background/Objectives: Micro-calcification is a major target for high-risk plaque but the mechanistic linkage with macrophage-driven inflammation remains questionable. To address this issue, we newly innovated dual-targeted multimodal imaging strategy for calcifying inflammatory activity by integration of intravascular OCT with near-infrared fluorescence (NIRF) molecular imaging. Methods/Results: We fully integrated dual-targeted NIRF molecular imaging with intravascular OCT. Novel NIRF emitting probe targeting micro-calcification was fabricated by chemically coupling alendronate and Cy5.5 to the ends of azide-PEG-NHS ester (Al-Cy5.5). Based on whole body biodistribution, OCT/dual-NIRF in vivo imaging of rabbit aortoiliac atheroma was acquired 48 hrs and 72 hrs after intravenous injection of Al-Cy5.5 (5.0 mg/kg) and macrophage mannose receptor targeted Cy7-emitting probe (7.5 mg/kg), respectively. NIRF signals of Cy5.5 and Cy7 were highly enhanced at the area of micro-calcification and macrophage accumulation within the plaque (Figure) (p<0.01). Fluorescence microscopy and immunostainings from the corresponding sections well corroborated the in vivo findings and concomitantly elevated dual-NIRF signals indicated the presence of calcifying inflammatory activity in atheroma. Intriguingly, osteogenic activity (TRAP stain) was closely interconnected with macrophages in superficial micro-calcification rather inner dense calcification (p<0.01). Conclusions: Our intravascular OCT/dual-NIRF imaging was feasible to simultaneously visualize micro-calcification, osteogenic activity and macrophages in the coronary-sized atheroma. This novel imaging strategy is expected to expand our pathophysiologic insight for the biological behavior of calcifying inflammatory activity existing on the superficial fibrous cap portion of high-risk plaques.

Clove Oil-Nanostructured Lipid Carriers: A Platform of Herbal Anesthetics in Whiteleg Shrimp (Penaeus vannamei)

Whiteleg shrimp (Penaeus vannamei) have been vulnerable to the stress induced by different aquaculture operations such as capture, handling, and transportation. In this study, we developed a novel clove oil-nanostructured lipid carrier (CO-NLC) to enhance the water-soluble capability and improve its anesthetic potential in whiteleg shrimp. The physicochemical characteristics, stability, and drug release capacity were assessed in vitro. The anesthetic effect and biodistribution were fully investigated in the shrimp body as well as the acute multiple-dose toxicity study. The average particle size, polydispersity index, and zeta potential value of the CO-NLCs were 175 nm, 0.12, and −48.37 mV, respectively, with a spherical shape that was stable for up to 3 months of storage. The average encapsulation efficiency of the CO-NLCs was 88.55%. In addition, the CO-NLCs were able to release 20% of eugenol after 2 h, which was lower than the standard (STD)-CO. The CO-NLC at 50 ppm observed the lowest anesthesia (2.2 min), the fastest recovery time (3.3 min), and the most rapid clearance (30 min) in shrimp body biodistribution. The results suggest that the CO-NLC could be a potent alternative nanodelivery platform for increasing the anesthetic activity of clove oil in whiteleg shrimp (P. vannamei).

Glycosylation of PAMAM dendrimers significantly improves tumor macrophage targeting and specificity in glioblastoma

Glioblastoma is among the most aggressive forms of cancers, with a median survival of just 15–20 months for patients despite maximum clinical intervention. The majority of conventional anti-cancer therapies fail due to associated off-site toxicities which can be addressed by developing target-specific drug delivery systems. Advances in nanotechnology have provided targeted systems to overcome drug delivery barriers associated with brain and other types of cancers. Dendrimers have emerged as promising vehicles for targeted drug and gene delivery. Dendrimer-mediated targeting strategies can be further enhanced through the addition of targeting ligands to enable receptor-specific interactions. Here, we explore the sugar moieties as ligands conjugated to hydroxyl-terminated polyamidoamine dendrimers to leverage altered metabolism in cancer and immune targeting. Using a highly facile click chemistry approach, we modified the surface of dendrimers with glucose, mannose, or galactose moieties in a well-defined manner, to target upregulated sugar transporters in the context of glioblastoma. We show that glucose modification significantly enhanced targeting of tumor-associated macrophages (TAMs) and microglia by increasing brain penetration and cellular internalization, while galactose modification shifts targeting away from TAMs towards galectins on glioblastoma tumor cells. Mannose modification did not alter TAMs and microglia targeting of these dendrimers, but did alter their kinetics of accumulation within the GBM tumor. The whole body biodistribution was largely similar between the systems. These results demonstrate that dendrimers are versatile delivery vehicles that can be modified to tailor their targeting for the treatment of glioblastoma and other cancers.

Targeted radionuclide therapy: an emerging field in solid tumours.

Targeted radionuclide therapy (TRNT) is characterized by systemic administration of radiolabelled drugs, targeting specific molecular alterations expressed on the tumour cells. Small molecules, labelled with β- or α- emitting radioisotopes, are used to deliver radiation directly to the tumour sites. Pretreatment imaging to visualize whole body biodistribution of the target, using the same drugs labelled with positron or γ-emitting radionuclides, completes the concept of theranostic. This review will briefly summarize the current clinical research findings and applications of TRNT in solid tumours, mostly focusing on neuroendocrine and prostate neoplasms. Peptide receptor radionuclide therapy is a major component in the management of gastroentropancreatic neuroendocrine tumours, with favourable safety profile, quality-of-life improvement and survival benefit. On the NETTER-1 study, it proved to be more effective than high-dose long-acting-release octreotide, leading to its regulatory approval. Prostate-specific membrane antigen (PSMA) is an excellent target for TRNT in prostate cancer. 177Lu-PSMA radioligand therapy demonstrated higher response rates in patients with metastatic castration resistant prostate cancer, when compared with second-line chemotherapy. New developments, including targeting of fibroblast activation proteins overexpressed in the tumour stroma, show promising preliminary results in the theranostic setting. Recent research has demonstrated and consolidated the use of TRNT against well established targets in neuroendocrine tumours and prostate cancer. The identification of new promising molecular targets for TRNT, will further expand the theranostic applications of radionuclides in the field of nuclear medicine.

Rapid Clearance of IR783 and Methyl‐β‐cyclodextrin Complex for Improved Tumor Imaging

AbstractNear‐infrared (NIR) fluorescence cancer imaging with targeted NIR fluorophores holds considerable promise for accurate detection and cancer diagnosis. Among the various NIR heptamethine cyanine dyes reported previously, IR783 as a single small molecule has been widely used for tumor‐targeted imaging without the additional conjugation of targeting moieties. Despite the potential advantages of IR783, the major problems, such as its non‐specific uptake in normal tissues/organs and slow clearance, remain to be solved. A key determinant of sensitivity and detectability in tumor imaging is the improvement of the tumor‐to‐background ratio (TBR). Herein, a simple and effective supramolecular complex self‐assembled from IR783 and methyl‐β‐cyclodextrin is developed to improve tumor imaging accompanied by rapid clearance from the body. The IR783‐cyclodextrin complex allowed for rapid whole body biodistribution, which remarkably reduced non‐specific background uptake, and thus increased the TBR value within 24 h post‐injection. Therefore, this strategy is applicable in combination with many different types of carbocyanine dyes for improved tumor imaging.

Critical Parameters to Improve Pancreatic Cancer Treatment Using Magnetic Hyperthermia: Field Conditions, Immune Response, and Particle Biodistribution.

Magnetic hyperthermia (MH) was used to treat a murine model of pancreatic cancer. This type of cancer is generally characterized by the presence of dense stroma that acts as a barrier for chemotherapeutic treatments. Several alternating magnetic field (AMF) conditions were evaluated using three-dimensional (3D) cell culture models loaded with magnetic nanoparticles (MNPs) to determine which conditions were producing a strong effect on the cell viability. Once the optimal AMF conditions were selected, in vivo experiments were carried out using similar frequency and field amplitude parameters. A marker of the immune response activation, calreticulin (CALR), was evaluated in cells from a xenograft tumor model after the MH treatment. Moreover, the distribution of nanoparticles within the tumor tissue was assessed by histological analysis of tumor sections, observing that the exposure to the alternating magnetic field resulted in the migration of particles toward the inner parts of the tumor. Finally, a relationship between an inadequate body biodistribution of the particles after their intratumoral injection and a significant decrease in the effectiveness of the MH treatment was found. Animals in which most of the particles remained in the tumor area after injection showed higher reductions in the tumor volume growth in comparison with those animals in which part of the particles were found also in the liver and spleen. Therefore, our results point out several factors that should be considered to improve the treatment effectiveness of pancreatic cancer by magnetic hyperthermia.

Synthesis and Characterization of [18F]JNJ-46356479 as the First 18F-Labeled PET Imaging Ligand for Metabotropic Glutamate Receptor 2.

Metabotropic glutamate receptor 2 (mGluR2) has been implicated in various psychiatric and neurological disorders, such as schizophrenia and Alzheimer's disease. We have previously developed [11C]7 as a PET radioligand for imaging mGluR2. Herein, [18F]JNJ-46356479 ([18F]8) was synthesized and characterized as the first 18F-labeled mGluR2 imaging ligand to enhance diagnostic approaches for mGluR2-related disorders. JNJ-46356479 (8) was radiolabeled via the copper (I)-mediated radiofluorination of organoborane 9. In vivo PET imaging experiments with [18F]8 were conducted first in C57BL/6 J mice and Sprague-Dawley rats to obtain whole body biodistribution and brain uptake profile. Subsequent PET studies were done in a cynomolgus monkey (Macaca fascicularis) to investigate the uptake of [18F]8 in the brain, its metabolic stability, as well as pharmacokinetic properties. JNJ-46356479 (8) exhibited excellent selectivity against other mGluRs. In vivo PET imaging studies showed reversible and specific binding characteristic of [18F]8 in rodents. In the non-human primate, [18F]8 displayed good in vivo metabolic stability, excellent brain permeability, fast and reversible kinetics with moderate heterogeneity across brain regions. Pre-treatment studies with compound 7 revealed time-dependent decrease of [18F]8 accumulation in mGluR2 rich regions based on SUV values with the highest decrease in the nucleus accumbens (18.7 ± 5.9%) followed by the cerebellum (18.0 ± 7.9%), the parietal cortex (16.9 ± 7.8%), and the hippocampus (16.8 ± 6.9%), similar to results obtained in the rat studies. However, the volume of distribution (VT) results derived from 2T4k model showed enhanced VT from a blocking study with compound 7. This is probably because of the potentiating effect of compound 7 as an mGluR2 PAM as well as related non-specific binding in the tissue data. [18F]8 readily crosses the blood-brain barrier and demonstrates fast and reversible kinetics both in rodents and in a non-human primate. Further investigation of [18F]8 on its binding specificity would warrant translational study in human.

Engineering Intelligent Nanosystems for Enhanced Medical Imaging

Medical imaging serves to obtain anatomical and physiological data, supporting medical diagnostics as well as providing therapeutic evaluation and guidance. A variety of contrast agents have been developed to enhance the recorded signals and to provide molecular imaging. However, fast clearance from the body or nonspecific biodistribution often limit their efficiency, constituting challenges that need to be overcome. Nanoparticle‐based systems are currently emerging as versatile and highly integrated platforms providing improved circulating times, tissue specificity, high loading capacity for signaling moieties, and multimodal imaging features. Furthermore, nanoengineered devices can be tuned for specific applications and the development of responsive behaviors. Responses include in situ modulation of nanoparticle size, increased intratissue mobility through active propulsion of motorized particles, and active modulation of the particle surroundings such as the extracellular matrix for an improved penetration and retention at the desired locations. Once accumulated in the targeted tissue, smart nanoparticle‐based contrast agents can provide molecular sensing of biomarkers or characteristics of the tissue microenvironment. In this case, the signal or contrast provided by the nanosystem is responsive to the presence or concentration of an analyte. Herein, recent developments of intelligent nanosystems to improve medical imaging are presented.

In Vitro and In Vivo Toxicity and Biodistribution of Paclitaxel-Loaded Cubosomes as a Drug Delivery Nanocarrier: A Case Study Using an A431 Skin Cancer Xenograft Model

Cubosomes with an internal three-dimensional (3D) periodic and porous particulate nanostructure have emerged as a promising drug delivery system for hydrophobic small molecules as well as large biomolecules over the past several decades. Limited understanding of their safety profiles and biodistribution, however, hinders clinical translation. This study used monoolein-based cubosomes stabilized by Pluronic F127 and 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[maleimide(polyethylene glycol)] polymers to encapsulate paclitaxel (PTX) as a model drug and investigated the in vitro cytotoxicity, in vivo acute response, and whole body biodistribution of the developed nanoparticles. Comparison of the PTX and nanoparticle cytotoxicity in two-dimensional and 3D spheroid cell models revealed distinct differences, with the cells in the 3D model found to be more tolerable to unloaded PTX as well as the PTX-loaded nanoparticle form. One-time intraperitoneal (i.p.) injection of unloaded cubosomes were generally well tolerated up to 400 mg/kg. Using the A431 skin cancer xenograft model, in vivo imaging studies showed the preferential accumulation of PTX-loaded cubosomes at the tumor sites following i.p. injection. Lastly, average tumor size was reduced by approximately 50% in the nanoparticle-based treatment group compared to the unloaded PTX drug group. The study provides significant information on the biological response of cubosomes and highlights their potential as a versatile drug delivery platform for safe and effective delivery of chemotherapeutic drugs.

Synthesis and preliminary studies of 11C-labeled tetrahydro-1,7-naphthyridine-2-carboxamides for PET imaging of metabotropic glutamate receptor 2.

Selective modulation of metabotropic glutamate receptor 2 (mGlu2) represents a novel therapeutic approach for treating brain disorders, including schizophrenia, depression, Parkinson's disease (PD), Alzheimer's disease (AD), drug abuse and addiction. Imaging mGlu2 using positron emission tomography (PET) would allow for in vivo quantification under physiological and pathological conditions and facilitate drug discovery by enabling target engagement studies. In this paper, we aimed to develop a novel specific radioligand derived from negative allosteric modulators (NAMs) for PET imaging of mGlu2.Methods. A focused small molecule library of mGlu2 NAMs with tetrahydro naphthyridine scaffold was synthesized for pharmacology and physicochemical evaluation. GIRK dose-response assays and CNS panel binding selectivity assays were performed to study the affinity and selectivity of mGlu2 NAMs, among which compounds 14a and 14b were selected as PET ligand candidates. Autoradiography in SD rat brain sections was used to confirm the in vitro binding specificity and selectivity of [11C]14a and [11C]14b towards mGlu2. In vivo binding specificity was then studied by PET imaging. Whole body biodistribution study and radiometabolite analysis were conducted to demonstrate the pharmacokinetic properties of [11C]14b as most promising PET mGlu2 PET ligand.Results. mGlu2 NAMs 14a-14g were synthesized in 14%-20% yields in five steps. NAMs 14a and 14b were selected to be the most promising ligands due to their high affinity in GIRK dose-response assays. [11C]14a and [11C]14b displayed similar heterogeneous distribution by autoradiography, consistent with mGlu2 expression in the brain. While PET imaging study showed good brain permeability for both tracers, compound [11C]14b demonstrated superior binding specificity compared to [11C]14a. Further radiometabolite analysis of [11C]14b showed excellent stability in the brain.Conclusions. Compound 14b exhibited high affinity and excellent subtype selectivity, which was then evaluated by in vitro autoradiography and in vivo PET imaging study after labeling with carbon-11. Ligand [11C]14b, which we named [11C]MG2-1904, demonstrated high brain uptake and excellent in vitro/in vivo specific binding towards mGlu2 with high metabolic stability in the brain. As proof-of-concept, our preliminary work demonstrated a successful example of visualizing mGlu2 in vivo derived from NAMs, which represents a promising chemotype for further development and optimization aimed for clinical translation.

Yttrium-86 Is a Positron Emitting Surrogate of Gadolinium for Noninvasive Quantification of Whole-Body Distribution of Gadolinium-Based Contrast Agents.

Gadolinium-based contrast agents (GBCAs) are used to provide diagnostic information in clinical magnetic resonance (MR) examinations. Gadolinium (Gd) has been detected in the brain, bone and skin of patients, months and years following GBCA administration, raising concerns about long term toxicity. Despite increased scrutiny, the concentration, chemical form and fate of the retained gadolinium species remain unknown. Importantly, the whole body biodistribution and organ clearance of GBCAs is poorly understood in humans. Gadolinium lacks suitable isotopes for nuclear imaging. We demonstrate that the yttrium-86 isotope can be used as a gadolinium surrogate. We show that Gd and their analogous Y complexes have similar properties both in solution and in vivo, and that yttrium-86 PET can be used to track the biodistribution of GBCAs over a two-day period.

18F]SPA-RQ/PET Study of NK1 receptors in the Whole Body of Guinea Pig and Rat

There is a substantial interest in the development of NK1 substance P antagonists as potential treatments for various neuropsychiatric and somatic disorders. The aim of this study was to determine whether [18F]SPA-RQ can be utilized as a tool for studying the whole body distribution and function of NK1 receptors in preclinical settings. The compound was injected into guinea pigs with or without premedication with a NK1 receptor antagonist (NK1A-2). For comparison, we included two rats in the study, as the affinity of antagonists for NK1 receptors is known to vary between species. The whole body biodistribution of the tracer was determined at several time points. The tracer showed specific binding in organs compatible with the known location of NK1-receptors. Premedication with a NK1 antagonist led to an inhibited uptake of [18F]SPA-RQ in several organs of guinea pigs, notably intestine, pancreas, urinary bladder, uterus, skin and lung. Specific binding was also seen in both cortex and striatum. In contrast, negligible specific binding was observed in the rat brain with [18F]SPA-RQ, whereas the tracer uptake in peripheral tissues was similar to that seen in guinea pigs. We conclude that [18F]SPA-RQ/PET is a useful tool to study the distribution and function of peripherally located NK1 receptors e.g. in different disease models.

In vivo and in vitro evaluation of 177Lu-labeled DOTA-2-deoxy-D-glucose in mice. A novel radiopharmaceutical agent for cells imaging and therapy.

Incorporation of lutetium-177 (177Lu) into suitable molecules that are implicated in cancer pathology represents a promising approach for the diagnosis and treatment of cancer. The goal of the present study was to develop a novel 177Lu labeled radiopharmaceutical agent for both radioimaging and targeted radionuclide therapy. Given the synthetic versatility of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) ligand as a metal chelator and high demand of sugar molecules such as deoxyglucose (DG) in cancer cells, we carried out the radiosynthesis of a novel radiopharmaceutical agent, namely, 177Lu-DOTA-DG, and utilized it for imaging of cancer and also for the targeted radiation therapy of cancer tissues. In this study, we developed an efficient radiochemical synthesis of 177Lu-DOTA-DG and evaluated its pharmacological properties in vitro/in vivo. Our results showed DOTA-DG can be labeled with 177Lu with excellent radiochemical yield at 90oC in 30min. The resulting 177Lu-DOTA-DG exhibited high degree of stability without significant radiolysis up to 120h in human serum and phosphate buffer. Favorable pharmacokinetics profile was demonstrated by rapid blood clearance in 4T1 murine tumor mice and heterogeneous whole body biodistribution of 177Lu-DOTA-DG. Further, Comet assay experiments indicated that cancer cells treated with 177Lu-DOTA-DG showed significant higher degree of DNA damage compared to cells treated with 177Lu3+ or non-treated cells. This study showed that there is a great potential of using 177Lu-DOTA-DG as an imaging and therapeutic agent for cancer diagnosis and treatment. Furthermore, this study provides valuable information for developing novel 177Lu-labeled radiopharmaceuticals.

Serum type and concentration both affect the protein-corona composition of PLGA nanoparticles.

Background: When nanoparticles (NPs) are applied into a biological fluid, such as blood, proteins bind rapidly to their surface forming a so-called “protein corona”. These proteins are strongly attached to the NP surface and confers them a new biological identity that is crucial for the biological response in terms of body biodistribution, cellular uptake, and toxicity. The corona is dynamic in nature and it is well known that the composition varies in dependence of the physicochemical properties of the NPs. In the present study we investigated the protein corona that forms around poly(lactide-co-glycolide) (PLGA) NPs at different serum concentrations using two substantially different serum types, namely fetal bovine serum (FBS) and human serum. The corona was characterized by means of sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE), Bradford protein assay, zeta potential measurements, and liquid chromatography–mass spectrometry/mass spectrometry (LC–MS/MS). Additionally, the time-dependent cell interaction of PLGA NPs in the absence or presence of a preformed protein corona was assessed by in vitro incubation experiments with the human liver cancer cell line HepG2.Results: Our data revealed that the physiological environment critically affects the protein adsorption on PLGA NPs with significant impact on the NP–cell interaction. Under comparable conditions the protein amount forming the protein corona depends on the serum type used and the serum concentration. On PLGA NPs incubated with either FBS or human serum a clear difference in qualitative corona protein composition was identified by SDS-PAGE and LC–MS/MS in combination with bioinformatic protein classification. In the case of human serum a considerable change in corona composition was observed leading to a concentration-dependent desorption of abundant proteins in conjunction with an adsorption of high-affinity proteins with lower abundance. Cell incubation experiments revealed that the respective corona composition showed significant influence on the resulting nanoparticle–cell interaction.Conclusion: Controlling protein corona formation is still a challenging task and our data highlight the need for a rational future experimental design in order to enable a prediction of the corona formation on nanoparticle surfaces and, therefore, the resulting biodistribution in the body.

In Vivo Toxicity Evaluation of PEGylated CuInS2/ZnS Quantum Dots in BALB/c Mice.

In recent years, quantum dots (QDs) have emerged as a potential contrast agent for bioimaging due to their bright luminescence and excellent photostability. However, the wide use of QDs in vivo has been limited due to underlying toxicity caused by leakage of heavy metals. Although non-cadmium QDs have been developed to resolve this issue, a comprehensive understanding of the toxicity of these newly developed QDs remains elusive. In this study, we administered PEGylated copper indium sulfide/zinc sulfide (CuInS2/ZnS), which are typical non-cadmium QDs, and analyzed the long-term effects of these nanoparticles in BALB/c mice. Body weight, hematology, blood biochemistry, organ histology, and biodistribution were examined at different time points. We found no significant difference in body weight after injection of CuInS2/ZnS QDs. These CuInS2/ZnS QDs entered and were accumulated in major organs for 90 days post-injection. The majority of biochemical indicators were not significantly different between the QDs-treated group and the control group. In addition, no significant histopathological abnormalities were observed in the treated mice compared with the control mice. CuInS2/ZnS QDs did not lead to observable toxicity in vivo following either the administration of a high or low dose. Our research not only provides direct evidence of the bio-safety of CuInS2/ZnS QDs, but also a feasible method for evaluating nanoparticle toxicity.