Determination of the concentration of complex boronated compounds in biological tissues by inductively coupled plasma atomic emission spectrometry

The application of inductively coupled plasma atomic emission spectrometry (ICP-AES) to the determination of the concentration of complex boron-containing compounds in biological tissue samples is described. Tissue digestion is achieved with perchloric acid and hydrogen peroxide in 1 hr at 75 degrees C. The ICP-AES method gave a linear response for elemental boron concentration in the range 0.05 to 100 ppm and does not require the reduction of the boron to a simple species, such as boric acid. Complete recovery of boron in complex boron cluster compounds was obtained. The procedure has been applied to the determination of the boron content in compounds synthesised for neutron capture therapy and is suitable for use in biodistribution studies of such compounds.

Boronated monoclonal antibody 225.28S for potential use in neutron capture therapy of malignant melanoma

The concept of conjugating boron cluster compounds to monoclonal antibodies has been examined by several groups of research workers in boron neutron capture therapy (BNCT). The procedures reported to date for boronation of monoclonal antibodies resulted in either an inadequate level of boron incorporation, the precipitation of the conjugates, or a loss of immunological activity. The present report describes the conjugation of dicesium-mercapto-undecahydrododecaborate (Cs2B12H11SH) to 225.28S monoclonal antibody directed against high molecular weight melanoma-associated antigens (HMW-MAA), using poly-L-ornithine as a "bridge" to increase the carrying capacity of the antibody and to minimize change in the conformational structure of antibody. The method produces a boron content of 1,300 to 1,700 B atoms per molecule 225.28S while retaining the immunoreactivity. Characterization in terms of the homogeneity of the conjugation of the boron-monoclonal antibody conjugates has been studied by gel electrophoresis and ion-exchange HPLC.

Photolytic decomposition of hydrochlorothiazide

Hydrochlorothiazide decomposes upon irradiation with near-UV light (lambda greater than 310 nm) both in methanol and aqueous solutions. In the photolysis the chlorine substituent is removed to be replaced by either--H or--OR from the solvent ROH. Hydrolysis of the thiadiazine ring is superimposed upon the dechlorination. The presence of oxygen inhibits the decomposition. The mechanism of the photolysis is suggested to involve cation radical formation which facilitates the hydrolysis step. 5-Chloro-2,4-disulphonamido-aniline, the normal hydrolysis product from hydrochlorothiazide, is also susceptible to photolytic dechlorination by a similar mechanism.

Photosensitization by drugs: photolysis of some chlorine-containing drugs

Irradiation with ultraviolet light of chlorpromazine, prochlorperazine, frusemide or hydrochlorothiazide in either aqueous or methanol solution yielded free chloride ion. Potentiometric methods were used to detect one mol of chloride ion produced per mol of drug irradiated in deoxygenated solution, with a concomitant equimolar appearance of hydrogen ion. Saturation of the solutions with oxygen strongly inhibited the photolysis reaction in methanol but only partially inhibited the production of Cl- and H+ in aqueous solution. The oxidation of 2,5-dimethylfuran is photosensitized by these drugs more effectively in methanol compared with aqueous solution. The photochemical behaviour is consistent with a photodissociative process occurring predominantly in methanol while photoionization predominates in aqueous media. No chloride ion was detected after extended irradiation of chlortetracycline, demeclocycline, chlordiazepoxide and hexachlorophane. The photolability of the chlorine in the compounds tested correlated with their ability to photosensitize oxidation by the Type I (free radical) mechanism.