ABSTRACT
In general, cells and microorganisms are relatively insensitive to the direct effects of visible light, and in any case are frequently inaccessible to such radiation, since light is transmitted to a limited extent through the outer layers of living organisms. Some of the viruses were evidently impermeable to certain dyes, and this illustrates a possible limitation in the use of photosensitizers as antivirals, especially for viruses without membranes. The extent of photoinduced damage to viruses is dependent on the wavelength of the incident light, since photosensitizers are generally excited over a fairly narrow band of radiation. In order to excite the photosensitizer, light of the appropriate wavelength must be supplied to the chemical while it is in the vicinity of the potential target molecule, such as a virion component. The production of the excited molecule is referred to as the primary photochemical process.
