Abstract
The effect of photodynamic action of certain dyes on various substances, among which may be mentioned different types of animal cells, viruses 1 , 2 , 3 and soluble toxins of both bacterial 4 and animal origin, 5 is a well-known phenomenon. Workers generally agree as to the extreme susceptibility of these substances to the photodynamic action of dyes, the optimal concentration of the dye employed, and the relatively short time required for exposure, but disagree with regard to the antigenicity of substances so treated. The present study aims to investigate the reaction of diphtheria toxin to the photodynamic action of methylene blue upon which subject little study has been made. Diphtheria toxin is looked upon as a more suitable material than either tetanus toxin or viruses on account of its greater stability and ease with which quantities given can be accurately measured and properly controlled.
The technique employed is essentially similar to those of other workers. 1 , 5 Methylene blue is selected since it has been more thoroughly studied than other dyes. A single batch of toxin containing 400 M.L.D. per cc. for the guinea pig, or 2000 M.L.D per cc. for Chinese hamsters weighing 20-25 gm., was used throughout the experiment, employing as diluent 0.9% salt solution for both dye and toxin. As source of radiation, both direct sunlight during summer and early autumn and electric light of 100 watts, 110 volts at 16.5 inches distance were used. In a preliminary study, the minimal time for exposure was found to lie between 20-30 minutes. In order to obtain full manifestation of combined action of light and dye, it was subsequently fixed at 60 minutes in all instances. Table I shows the maximal M.L.D. for hamsters which may be destroyed by the optimal concentration of methylene blue when exposed to sunlight and to artificial light. The number of animals in each group varied from 3 to 9.
Get full access to this article
View all access options for this article.