Dae Seong Choi

Highly efficient method for 125I-radiolabeling of biomolecules using inverse-electron-demand Diels–Alder reaction

In this report, we present a rapid and highly efficient method for radioactive iodine labeling of trans-cyclooctene group conjugated biomolecules using inverse-electron-demand Diels-Alder reaction. Radioiodination reaction of the tetrazine structure was carried out using the stannylated precursor 2 to give 125I-labeled azide ([125I]1) with high radiochemical yield (65±8%) and radiochemical purity (>99%). For radiolabeling application of [125I]1, trans-cyclooctene derived cRGD peptide and human serum albumin were prepared. These substrated were reacted with [125I]1 under mild condition to provide the radiolabeled products [125I]6 and [125I]8, respectively, with excellent radiochemical yields. The biodistribution study of [125I]8 in normal ICR mice showed significantly lower thyroid uptake values than that of 125I-labeled human serum albumin prepared by a traditional radiolabeling method. Therefore [125I]8 will be a useful radiolabeled tracer in various molecular imaging and biological studies. Those results clearly demonstrate that [125I]1 will be used as a valuable prosthetic group for radiolabeling of biomolecules.

Radiosynthesis of 123I-labeled hesperetin for biodistribution study of orally administered hesperetin

The purpose of this study is to synthesize 123I-labeled hesperetin and to investigate its in vivo behavior. The optimized labeling condition provided two isomers of 123I-labeled hesperetin with high radiochemical yields and radiochemical purities. Both 123I-labeled products were orally administered to normal ICR mice, and the initial result showed that most of 123I activity was detected in the stomach and the intestines. A part of 123I-labeled hesperetin was absorbed from the small intestine to bloodstream and then it was distributed in normal organs. The results in the present study provided an efficient radiolabeling method of flavonoid and quantitative organ distribution of orally administered hesperetin.

Synthesis and evaluation of an (125)I-labeled azide prosthetic group for efficient and bioorthogonal radiolabeling of cyclooctyne-group containing molecules using copper-free click reaction.

Herein we report the radiosynthesis of a pyridine derived azide prosthetic group for iodine radioisotope labeling of dibenzocyclooctyne (DBCO) conjugated molecules. The radiolabeling of the stannylated precursor 2 was conducted using [(125)I]NaI and chloramine-T to give (125)I-labeled azide ([(125)I]1) with high radiochemical yield (72±8%, n=4) and radiochemical purity (>99%). Using (125)I-labeled azide ([(125)I]1), cyclic RGD peptide and near infrared fluorescent molecule were efficiently labeled with modest to good radiochemical yields. The biodistribution study and SPECT/CT images showed that [(125)I]1 underwent rapid renal clearance. These results clearly demonstrated that [(125)I]1 could be used as an useful radiotracer for in vivo pre-targeted imaging as well as efficient in vitro radiolabeling of DBCO containing molecules.

Gamma-irradiated black ginseng extract inhibits mast cell degranulation and suppresses atopic dermatitis-like skin lesions in mice

Gamma irradiation is able to affect various structural modification and an increase of the biological properties of biomaterials. This study was conducted to investigate the anti-allergenic effect of γ-irradiated black ginseng extract (BGE) using in vitro and in vivo experiments. IgEantigen complex-induced degranulation was measured in RBL-2H3 mast cells. In addition, an anti-atopic dermatitis (AD) test was carried out by spreading γ-irradiated BGE on the dorsal skin of 2,4-dinitrochlorobenzene (DNCB)-induced BALB/c mice. The content of arginylfructose (AF) of gamma-irradiated BGE was higher than that of BGE. In RBL-2H3 mast cells, γ-irradiated BGE treatments significantly reduced the IgE-antigen complex-induced release of β-hexosaminidase, histamine, intracellular ROS, and Ca2+ influx. A western blot analysis showed that γ-irradiated BGE had an inhibitory activity on the FcεRI-mediated signaling in mast cells. In the DNCB-induced AD model, γ-irradiated BGE significantly alleviated the ADlike skin symptoms and clinical signs. The suppression of AD by γ-irradiated BGE was accompanied by a decrease in the serum level of IgE and IL-4, as well as the number of leukocyte. Gamma-irradiated BGE also suppressed IL-4 and increased IFN-γ in splenocytes. Our data suggests that γ-irradiated BGE may be effective therapeutic agents for the treatment of AD.

Efficient and Site-Specific 125I-Radioiodination of Bioactive Molecules Using Oxidative Condensation Reaction

In this report, the novel and site-specific radioiodination of biomolecules by using aryl diamine and alkyl aldehyde condensation reaction in the presence of a Cu2+ catalyst under ambient conditions was reported. 125I-labeled alkyl aldehyde was synthesized using a tin precursor with a high radiochemical yield (72 ± 6%, n = 5) and radiochemical purity (>99%). The utility of the radioiodinated precursor was demonstrated through aryl diamine-installed c[RGDfK(C)] peptide and human serum albumin (HSA). Radioiodinated c[RGDfK(C)] peptide and HSA protein were synthesized with high radiochemical yields and purity. 125I-HSA protein showed excellent in vivo stability and negligible thyroid uptake as compared with directly radioiodinated HSA by using the tyrosine group. Excellent reaction kinetics and the in vitro and in vivo stabilities of 125I-labeled alkyl aldehyde have suggested the usefulness of the strategy for the radioiodination of bioactive molecules.

Intracellular Protein Delivery System Using a Target-Specific Repebody and Translocation Domain of Bacterial Exotoxin

With the high efficacy of protein-based therapeutics and plenty of intracellular drug targets, cytosolic protein delivery in a cell-specific manner has attracted considerable attention in the field of precision medicine. Herein, we present an intracellular protein delivery system based on a target-specific repebody and the translocation domain of Pseudomonas aeruginosa exotoxin A. The delivery platform was constructed by genetically fusing an EGFR-specific repebody as a targeting moiety to the translocation domain, while a protein cargo was fused to the C-terminal end of the delivery platform. The delivery platform was revealed to efficiently translocate a protein cargo to the cytosol in a target-specific manner. We demonstrate the utility and potential of the delivery platform by showing a remarkable tumor regression with negligible toxicity in a xenograft mice model when gelonin was used as the cytotoxic protein cargo. The present platform can find wide applications to the cell-selective cytosolic delivery of diverse proteins in many areas.

An Optimized Protocol for the Efficient Radiolabeling of Gold Nanoparticles by Using a 125I-labeled Azide Prosthetic Group.

Here, we demonstrate a detailed protocol for the radiosynthesis of a 125I-labeled azide prosthetic group and its application to the efficient radiolabeling of DBCO-group-functionalized gold nanoparticles using a copper-free click reaction. Radioiodination of the stannylated precursor (2) was carried out by using [125I]NaI and chloramine T as an oxidant at room temperature for 15 min. After HPLC purification of the crude product, the purified 125I-labeled azide (1) was obtained with high radiochemical yield (75 ± 10%, n = 8) and excellent radiochemical purity (>99%). For the synthesis of radiolabeled 13-nm-sized gold nanoparticles, the DBCO-functionalized gold nanoparticles (3) were prepared by using a thiolated polyethylene glycol polymer. A copper-free click reaction between 1 and 3 gave the 125I-labeled gold nanoparticles (4) with more than 95% of radiochemical yield as determined by radio-thin-layer chromatography (radio-TLC). These results clearly indicate that the present radiolabeling method using a strain-promoted copper-free click reaction will be useful for the efficient and convenient radiolabeling of DBCO-group-containing nanomaterials.

Radioprotective effect of hesperetin against γ-irradiation-induced DNA damage and immune dysfunction in murine splenocytes

This study was conducted to evaluate the preventive effect of hesperetin against radiation-induced DNA damage and immune dysfunction in murine splenocytes. Isolated splenocytes from BALB/c mice were treated with hesperetin (20, 100, and 500 µM), and then irradiated at a dose of 2 and 4 Gy of γ-irradiation. Exposure to ?-radiation resulted in DNA damage and a reduction of cell viability as well as an elevation of the levels of proinflammatory cytokines, intracellular ROS (reactive oxygen species), and NO (nitric oxide). Hesperetin significantly enhanced the cell viability of the splenocytes compared with the irradiated group. In addition, hesperetin was found to be highly effective in preventing DNA damage as identified by comet and DNA ladder assays. Hesperetin also effectively inhibited proinflammatory cytokines, intracellular ROS, and NO in irradiated splenocytes. In conclusion, hesperetin was shown to be radioprotective against irradiation-induced DNA damage and immune dysfunction in murine splenocytes.

Radioprotective Effect of Post-treatment with Rutin on γ-Irradiation-induced Cellular Damage in Mice

This study aimed to investigate the therapeutic effect of rutin against whole-body γ-irradiation in BALB/c mice. BALB/c mice were randomly divided into four groups and exposed to 6 Gy γ-irradiation. One hour later, mice were orally administered rutin (50 and 100 mg/kg) for seven consecutive days. γ-Irradiation (6 Gy) resulted in cellular damage as manifested by elevated levels of plasma hepatic marker enzymes and lipid peroxidation in liver tissue, accompanied with decreased spleen and thymus indices, and white blood cell count. In addition, γ-irradiation significantly decreased the levels of antioxidant enzymes such as superoxide dismutase, glutathione peroxidase and catalase. Rutin treatment significantly protected against γ-irradiation-induced cellular damage, which was evident by the improvement in the status of most of the investigated parameters. Therefore, rutin has beneficial effects against radiation-induced damage.