Biotin derivatives carrying two chelating DOTA units. Synthesis, in vitro evaluation of biotinidases resistance, avidin binding, and radiolabeling tests.

The synthesis of four biotin derivatives carrying two DOTA moieties for each ligand (BisDOTA set) is reported, for increasing radiation/dose ratio and improving efficiency in the pretargeted avidin-biotin radioimmunotherapy. The biotin-containing scaffold of two BisDOTA was similar to the mono-DOTA derivative previously described. Then the scaffold was elongated by trifunctionalized spacers of different length and conjugated with one of the COOH groups of two DOTA. Two others were prepared starting from a on-resin lysine residue. The lysine alpha-NH2 was bonded to biotin, and then spacers were appended to the epsilon-NH2 and conjugated with two DOTA molecules. One compound contained a p-aminobenzoic acid spacer, which ensured higher head-to-tail distance and increased rigidity of the chain. These last two compounds had a very high ability to bond avidin and were labeled with 90Y at high specific activity. All the compounds were resistant to the action of serum biotinidases.

Quantification of drugs of abuse and some stimulants in hair samples by liquid chromatography-electrospray ionization ion trap mass spectrometry.

A qualitative and quantitative method for the analysis of drugs of abuse (cocaine and benzoylecgonine, opiates) and some stimulants in human hair was developed and validated. Hair samples were incubated with phosphate buffer (pH 5.0), chosen as the extraction medium, extracted with Bond Elut Certify cartridges and analyzed by LC-MS-MS and LC-MS(3) as confirmation for positive results. The method proved to be specific, accurate and precise across the calibration range (0.1-30 ng/mg) where good linearity was observed. Total extraction recovery, intra-assay accuracy and precision, limits of detection and limits of quantitation were estimated. The method was successfully applied to the analysis of hair samples collected from drug abusers and it was suitable for routine analytical applications in the Antidoping Laboratory of Public Health Laboratory.