Efficient Radiolabeling of Proteins and Antibodies via Maleamate–Cysteine Bioconjugation

The study introduces a novel maleamate-based prosthetic group specifically designed for efficient, site-specific radioiodination of biomolecules that contain or are modified with cysteine residues. This strategy is a compelling alternative to the conventional maleimide-based approach, demonstrating outstanding attributes such as high radiochemical yield, rapid reaction kinetics, applicability in aqueous media at neutral pH, and exceptional stability under a competitive environment

Pyrene-Tagged Ionic Liquids: Separable Organic Catalysts for S_N2 Fluorination

We prepared pyrene-substituted imidazolium-based ionic liquids (PILs) as organic catalysts for the S_N2 fluorination using alkali metal fluoride (MF). In this system, the PIL significantly enhanced the reactivity of MF due to the phase-transfer catalytic effect of the imidazolium moiety as well as the metal cation−π (pyrene) interactions. Furthermore, this homogeneous catalyst PIL was easily separated from the reaction mixture using reduced graphene oxide by π–π stacking with the pyrene of PIL

Radiometallic Complexes of DO3A-Benzothiazole Aniline for Nuclear Medicine Theranostics

To develop a radioactive metal complex platform for tumor theranostics, we introduced three radiopharmaceutical derivatives of 1,4,7,10-tetraazacyclododecane-1,4,7-trisacetic acid-benzothiazole aniline (DO3A-BTA, L1) labeled with medical radioisotopes for diagnosis (⁶⁸Ga/⁶⁴Cu) and therapy (¹⁷⁷Lu). The tumor-targeting ability of these complexes was demonstrated in a cellular uptake experiment, in which ¹⁷⁷Lu-L1 exhibited markedly higher uptake in HeLa cells than the ¹⁷⁷Lu-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid complex. According to in vivo positron emission tomography imaging, high accumulation of ⁶⁸Ga-L1 and ⁶⁴Cu-L1 was clearly visualized in the tumor site, while ¹⁷⁷Lu-L1 showed therapeutic efficacy in therapy experiments. Consequently, this molecular platform represents a useful approach in nuclear medicine toward tumor-theranostic radiopharmaceuticals when ⁶⁸Ga-L1 or ⁶⁴Cu-L1 is used for diagnosis, ¹⁷⁷Lu-L1 is used for therapy, or two of the compounds are used in conjunction with each other

Simple Methods for Tracking Stem Cells with ⁶⁴Cu-Labeled DOTA-hexadecyl-benzoate

The purpose of this study was to evaluate ⁶⁴Cu-labeled hexadecyl-1,4,7,10-tetraazacyclododecane-tetraacetic acid-benzoate (⁶⁴Cu-DOTA-HB) (<b>1</b>) as positron emission tomography (PET) radiotracer for stem cell imaging. Hexadecyl-DOTA-benzoate (DOTA-HB) (<b>2</b>) was efficiently labeled with ⁶⁴Cu (>99%), and cell labeling efficiency with adipose-derived stem cells (ADSCs) was over 50%. Labeling with <b>1</b> did not compromise cell viability. In the PET imaging, intramuscularly transplanted <b>1</b>-labeled ADSCs were monitored for 18 h in normal rat heart. These results indicate that <b>1</b> can be utilized as a promising radiotracer for monitoring of transplanted stem cells

High in Vivo Stability of ⁶⁴Cu-Labeled Cross-Bridged Chelators Is a Crucial Factor in Improved Tumor Imaging of RGD Peptide Conjugates

Although the importance of bifunctional chelators (BFCs) is well recognized, the chemophysical parameters of chelators that govern the biological behavior of the corresponding bioconjugates have not been clearly elucidated. Here, five BFCs closely related in structure were conjugated with a cyclic RGD peptide and radiolabeled with Cu-64 ions. Various biophysical and chemical properties of the Cu­(II) complexes were analyzed with the aim of identifying correlations between individual factors and the biological behavior of the conjugates. Tumor uptake and body clearance of the ⁶⁴Cu-labeled bioconjugates were directly compared by animal PET imaging in animal models, which was further supported by biodistribution studies. Conjugates containing propylene cross-bridged chelators showed higher tumor uptake, while a closely related ethylene cross-bridged analogue exhibited rapid body clearance. High in vivo stability of the copper–chelator complex was strongly correlated with high tumor uptake, while the overall lipophilicity of the bioconjugate affected both tumor uptake and body clearance

High in Vivo Stability of ⁶⁴Cu-Labeled Cross-Bridged Chelators Is a Crucial Factor in Improved Tumor Imaging of RGD Peptide Conjugates

Although the importance of bifunctional chelators (BFCs) is well recognized, the chemophysical parameters of chelators that govern the biological behavior of the corresponding bioconjugates have not been clearly elucidated. Here, five BFCs closely related in structure were conjugated with a cyclic RGD peptide and radiolabeled with Cu-64 ions. Various biophysical and chemical properties of the Cu­(II) complexes were analyzed with the aim of identifying correlations between individual factors and the biological behavior of the conjugates. Tumor uptake and body clearance of the ⁶⁴Cu-labeled bioconjugates were directly compared by animal PET imaging in animal models, which was further supported by biodistribution studies. Conjugates containing propylene cross-bridged chelators showed higher tumor uptake, while a closely related ethylene cross-bridged analogue exhibited rapid body clearance. High in vivo stability of the copper–chelator complex was strongly correlated with high tumor uptake, while the overall lipophilicity of the bioconjugate affected both tumor uptake and body clearance

Preliminary PET Study of ¹⁸F‑FC119S in Normal and Alzheimer’s Disease Models

To evaluate the efficacy of ¹⁸F-FC119S as a positron emission tomography (PET) radiopharmaceutical for the imaging of Alzheimer’s disease (AD), we studied the drug absorption characteristics and distribution of ¹⁸F-FC119S in normal mice. In addition, we evaluated the specificity of ¹⁸F-FC119S for β-amyloid (Aβ) in the AD group of an APP/PS1 mouse model and compared it with that in the wild-type (WT) group. The behavior of ¹⁸F-FC119S in the normal mice was characteristic of rapid brain uptake and washout patterns. In most organs, including the brain, ¹⁸F-FC119S reached its maximum concentration within 1 min and was excreted via the intestine. Brain PET imaging of ¹⁸F-FC119S showed highly specific binding of the molecule to Aβ in the cortex and hippocampus. The brain uptake and binding values for the AD group were higher than those for the WT group. These results indicated that ¹⁸F-FC119S would be a candidate PET imaging agent for targeting Aβ plaque

Facile Method To Radiolabel Glycol Chitosan Nanoparticles with ⁶⁴Cu via Copper-Free Click Chemistry for MicroPET Imaging

An efficient and straightforward method for radiolabeling nanoparticles is urgently needed to understand the <i>in vivo</i> biodistribution of nanoparticles. Herein, we investigated a facile and highly efficient strategy to prepare radiolabeled glycol chitosan nanoparticles with ⁶⁴Cu via a strain-promoted azide–alkyne cycloaddition strategy, which is often referred to as click chemistry. First, the azide (N₃) group, which allows for the preparation of radiolabeled nanoparticles by copper-free click chemistry, was incorporated to glycol chitosan nanoparticles (CNPs). Second, the strained cyclooctyne derivative, dibenzyl cyclooctyne (DBCO) conjugated with a 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) chelator, was synthesized for preparing the preradiolabeled alkyne complex with ⁶⁴Cu radionuclide. Following incubation with the ⁶⁴Cu-radiolabeled DBCO complex (DBCO-PEG₄-Lys-DOTA-⁶⁴Cu with high specific activity, 18.5 GBq/μmol), the azide-functionalized CNPs were radiolabeled successfully with ⁶⁴Cu, with a high radiolabeling efficiency and a high radiolabeling yield (>98%). Importantly, the radiolabeling of CNPs by copper-free click chemistry was accomplished within 30 min, with great efficiency in aqueous conditions. In addition, we found that the ⁶⁴Cu-radiolabeled CNPs (⁶⁴Cu-CNPs) did not show any significant effect on the physicochemical properties, such as size, zeta potential, or spherical morphology. After ⁶⁴Cu-CNPs were intravenously administered to tumor-bearing mice, the real-time, <i>in vivo</i> biodistribution and tumor-targeting ability of ⁶⁴Cu-CNPs were quantitatively evaluated by microPET images of tumor-bearing mice. These results demonstrate the benefit of copper-free click chemistry as a facile, preradiolabeling approach to conveniently radiolabel nanoparticles for evaluating the real-time <i>in vivo</i> biodistribution of nanoparticles

Additional file 1 of Development of finely tuned liposome nanoplatform for macrophage depletion

Additional file 1: Figure S1. NTA analysis of Liposomes. The size distribution of (a) Clodrosome and m-Clodrosome and (b) liposome nanoplatforms in PBS was measured using the NTA system. Figure S2. Stability of liposomes at different physiological conditions (PBS, human serum, and cell media (DMEM). No visible aggregates or precipitates of liposomes were observed in any of the experimental groups after 14 days. Figure S3. Clodronate releasing test. The clodronate encapsulation efficiency of the liposomes was measured using a nanodrop. None of the groups showed significant differences. Statistical analysis was conducted using one-way analysis of variance. Figure S4. Cell viability test of RAW264.7 treated liposomes. Comparison of liposomes with Clodrosome® and m-Clodrosome®. None of the groups showed significant differences. Statistical analysis was conducted using one-way analysis of variance. Figure S5. RAW264.7 cell uptake of liposomes. Comparison of the cellular uptake of liposomes at different time points (0.5, 1, 2, 4, and 24 h). All scale bars are 75 µm. Figure S6. Confocal images of the liver tissue treated with liposomes. Ex vivo tissue fluorescence images were acquired 24 h post-injection of liposomes in normal mice. All scale bars represent 250 µm. Figure S7. Histological analysis of H&E stained liposome-treated liver tissue. Figure S8. Labeling efficiency of all the liposomes. The labeling efficiency of all the liposomes used in the experiments was assessed using click chemistry with [64Cu]Cu-NOTA-N3. The radiochemical purity of all the liposomes was determined using the radio TLC chromatogram and percentage of value at Rf = 0.0–0.1