Revealing the differences in collision cross section values of small organic molecules acquired by different instrumental designs and prediction models.

The number of open access databases containing experimental and predicted collision cross section (CCS) values is rising and leads to their increased use for compound identification. However, the reproducibility of reference values with different instrumental designs and the comparison between predicted and experimental CCS values is still under evaluation. This study compared experimental CCS values of 56 small molecules (Contaminants of Emerging Concern) acquired by both drift tube (DT) and travelling wave (TW) ion mobility mass spectrometry (IM-MS). The TWIM-MS included two instrumental designs (Synapt G2 and VION). The experimental TWCCSN2 values obtained by the TWIM-MS systems showed absolute percent errors (APEs) < 2% in comparison to experimental DTIMS data, indicating a good correlation between the datasets. Furthermore, TWCCSN2 values of [M - H]- ions presented the lowest APEs. An influence of the compound class on APEs was observed. The applicability of prediction models based on artificial neural networks (ANN) and multivariate adaptive regression splines (MARS), both built using TWIM-MS data, was investigated for the first time for the prediction of DTCCSN2 values. For [M+H]+ and [M - H]- ions, the 95th percentile confidence intervals of observed APEs were comparable to values reported for both models indicating a good applicability for DTIMS predictions. For the prediction of DTCCSN2 values of [M+Na]+ ions, the MARS based model provided the best results with 73.9% of the ions showing APEs below the threshold reported for [M+Na]+. Finally, recommendations for database transfer and applications of prediction models for future DTIMS studies are made.

Preclinical Evaluation of a Novel 18F-Labeled dTCO-Amide Derivative for Bioorthogonal Pretargeted Positron Emission Tomography Imaging.

Pretargeted positron emission tomography (PET) imaging based on the bioorthogonal inverse-electron-demand Diels-Alder reaction between tetrazines (Tz) and trans-cyclooctenes (TCO) has emerged as a promising tool for solid tumor imaging, allowing the use of short-lived radionuclides in immune-PET applications. With this strategy, it became possible to achieve desirable target-to-background ratios and at the same time to decrease the radiation burden to nontargeted tissues because of the fast clearance of small PET probes. Here, we show the synthesis of novel 18F-labeled dTCO-amide probes for pretargeted immuno-PET imaging. The PET probes were evaluated regarding their stability, reactivity toward tetrazine, and pharmacokinetic profile. [ 18 F]MICA-213 showed an extremely fast kinetic rate (10,553 M-1 s-1 in 50:50 MeOH/water), good stability in saline and plasma up to 4 h at 37 °C with no isomerization observed, and the biodistribution in healthy mice revealed a mixed hepatobiliary and renal clearance with no defluorination and low background in other tissues. [ 18 F]MICA-213 was further used for in vivo pretargeted immune-PET imaging carried out in nude mice bearing LS174T colorectal tumors that were previously treated with a tetrazine-modified anti-TAG-72 monoclonal antibody (CC49). Pretargeted µPET imaging results showed clear visualization of the tumor tissue with a significantly higher uptake when compared to the control.