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Herein we report an efficient method for iodine radioisotope labeling of cyclooctyne-containing molecules using copper-free click reaction. For this study, radioiodination using the tin precursor 2 was carried out at room temperature to give 125 I-labeled azide ([ 125 I] 1 ) with high radiochemical yield (85%) and excellent radiochemical purity. Dibenzocyclooctyne (DBCO) containing cRGD peptide and gold nanoparticle were labeled with [ 125 I] 1 at 37 °C for 30 min to give triazoles with good radiochemical yields (67–95%). We next carried out tissue biodistribution study of [ 125 I] 1 in normal ICR mice to investigate the level of organ accumulation which needs to be considered for pre-targeted in vivo imaging. Large amount of [ 125 I] 1 distributed rapidly in liver and kidney from bloodstream and underwent rapid renal and hepatobiliary clearance. Moreover [ 125 I] 1 was found to be highly stable (>92%) in mouse serum for 24 h. Therefore [ 125 I] 1 could be used as a potentially useful radiotracer for pre-targeted imaging. Those results clearly indicated that the present radiolabeling method using copper free click reaction would be quite useful for both in vitro and in vivo labeling of DBCO group containing molecules with iodine radioisotopes. [ABSTRACT FROM AUTHOR]

Concern about environmental exposure to hazardous substances has grown over the past several decades, because these substances have adverse effects on human health. Methods used to monitor the biological uptake of hazardous substances and their spatiotemporal behavior in vivo must be accurate and reliable. Recent advances in radiolabeling chemistry and radioanalytical methodologies have facilitated the quantitative analysis of toxic substances, and whole-body imaging can be achieved using nuclear imaging instruments. Herein, we review recent literature on the radioanalytical methods used to study the biological distribution, changes in the uptake and accumulation of hazardous substances, including industrial chemicals, nanomaterials, and microorganisms. We begin with an overview of the radioisotopes used to prepare radiotracers for in vivo experiments. We then summarize the results of molecular imaging studies involving radiolabeled toxins and their quantitative assessment. We conclude the review with perspectives on the use of radioanalytical methods for future environmental research. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

[Display omitted] • New fluorescent probes (8a–d) were designed and synthesized based on a curcumin scaffold. • Probe 8b displayed an emission wavelength in the NIR region and a good binding affinity for the Aβ aggregates. • Probe 8b achieved clear visualization of Aβ plaques in 5XFAD transgenic mice. • The signal intensity of 8b in the brain of the 5XFAD mouse was much higher than that of the control group. • The biological uptake of 8b into the internal organs and brain was confirmed via ex vivo experiments. The abnormal self-assembly of amyloid-beta (Aβ) peptides into oligomers, as well as insoluble fibrils, has been identified as a key factor for monitoring the progression of Alzheimer's disease (AD). The noninvasive imaging of Aβ aggregates utilizing chemical probes can be a powerful and practical technique for accurately diagnosing and monitoring the progress of AD, as well as evaluating the effectiveness of therapeutic drug candidates in treating or managing it. Particularly, the near-infrared (NIR) fluorescence imaging of Aβ plaques is a potentially promising approach toward the efficient detection of the biomarker. In this study, we describe a new NIR fluorophore, which was based on curcumin derivatives. The fluorophore is equipped with desirable optical properties for in vivo brain imaging. The emission wavelength of the probe, 8b , is 667 nm, and its fluorescent intensity is significantly increased through binding with the Aβ aggregates. The probe allows the clear visualization of the Aβ plaques 10 min post administration, and the intensity of the fluorescent signal in the brain of a 5XFAD transgenic mouse model is more than three times higher than that of the normal control group. These results demonstrate that the designed probe can be an effective tool for visualizing Aβ plaques, as well as investigating the pathological progress of AD. [ABSTRACT FROM AUTHOR]