The phototoxicity of argon laser irradiation was studied in aqueous suspensions of Porphyromonas endodontalis (American Type Culture Collection [ATCC] 35406), Porphyromonas gingivalis (ATCC 33277), Prevotella denticola (ATCC 33184) and two strains of Prevotella intermedia (ATCC 15033 and 49046), all "black-pigmented bacteria," BPB, that accumulate cellular porphyrins. Several of these species have been implicated in the etiology of periodontal disease. Non-black-pigmented bacteria were also studied to test the specificity of irradiation as a potential photodynamic treatment for periodontal infections. Cell suspensions were irradiated with an argon laser at fluences of 20-200 J/cm2. When cultured in hemin-supplemented media, ATCC 15033 was the most sensitive to irradiation. However, a second strain of the same species (ATCC 49046) was resistant. The photosensitivity of other species ranked ATCC 33277 > 35406 = 33184 = 35496. When hemin was replaced in media by hemoglobin, ATCC 33277 became resistant to irradiation. Protoporphyrin IX content in BPB cells was shown not to be a major factor determining photosensitivity. Oxygen was required during irradiation for BPB species to be affected. Non-black-pigmented bacteria were much less sensitive to irradiation than BPB.

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A photodynamic method has been evaluated as a means of eradicating viral contaminants with the potential for rendering blood safe for transfusion. Herpes simplex virus type 1 (HSV-1) was tested under flowing conditions in culture media or in blood supplemented with the virus. Hematoporphyrin derivative was used as the sensitizer and was photoactivated with visible light at 630 nm and 5 J/cm2. HSV-1 in suspension both in culture medium as well as in blood was shown to be killed. The human immunodeficiency virus was also found to be photoinactivated in flowing cell culture medium and, thus, potentially may be inactivated in blood. These findings extend our previous studies which demonstrated that enveloped viruses can be photoinactivated with hematoporphyrin derivative in a static fluid system. Analysis of blood cell number, red cell lysis, plasma proteins, and other standard hematological tests showed no significant change. The possibility that transfusion-associated acquired immunodeficiency syndrome (AIDS) may result from a blood unit infected with human immunodeficiency virus that tested negative makes it imperative that a safe and effective means of viral killing be developed. The system reported here offers promise as an effective approach to this problem.

The photodynamic inactivation of HSV-1, a virus having a membranous envelope, with both a decaalkyl sapphyrin and its dicarboxy-substituted analog was studied. The decaalkyl sapphyrin was as efficient in the inactivation of HSV-1 on a per macrocycle basis as DHE, whereas the efficiency of the dicarboxy-substituted sapphyrin was approximately two orders of magnitude less. Fluorescence studies of sapphyrin's binding to liposomes and VSV suggested that the decaalkylsapphyrin bound monomerically to cholesterol-rich regions of the viral envelope, whereas its charged analog localized in a more polar environment.