Photodynamic therapy (PDT), also known as photoradiation therapy, phototherapy, or photochemo-therapy, involves the use of a photoactive dye (photosensitizer) that is activated by exposure to light of a specific wavelength in the presence of oxygen. The transfer of energy from the activated photosensitizer to available oxygen results in the formation of toxic oxygen species, such as singlet oxygen and free radicals. These very reactive chemical species can damage proteins, lipids, nucleic acids, and other cellular components. Applications of PDT in dentistry are growing rapidly: the treatment of oral cancer, bacterial and fungal infection therapies, and the photodynamic diagnosis (PDD) of the malignant transformation of oral lesions. PDT has shown potential in the treatment of oral leukoplakia, oral lichen planus, and head and neck cancer. Photodynamic antimicrobial chemotherapy (PACT) has been efficacious in the treatment of bacterial, fungal, parasitic, and viral infections. The absence of genotoxic and mutagenic effects of PDT is an important factor for long-term safety during treatment. PDT also represents a novel therapeutic approach in the management of oral biofilms. Disruption of plaque structure has important consequences for homeostasis within the biofilm. Studies are now leading toward selective photosensitizers, since killing the entire flora leaves patients open to opportunistic infections. Dentists deal with oral infections on a regular basis. The oral cavity is especially suitable for PACT, because it is relatively accessible to illumination.

Fusion of lipid-enveloped viruses with the cellular plasma membrane or the endosome membrane is mediated by viral envelope proteins that undergo large conformational changes following binding to receptors. The HIV-1 fusion protein gp41 undergoes a transition into a “six-helix bundle” after binding of the surface protein gp120 to the CD4 receptor and a co-receptor. Synthetic peptides that mimic part of this structure interfere with the formation of the helix structure and inhibit membrane fusion. This approach also works with the S spike protein of SARS-CoV-2. Here we review the peptide inhibitors of membrane fusion involved in infection by influenza virus, HIV-1, MERS and SARS coronaviruses, hepatitis viruses, paramyxoviruses, flaviviruses, herpesviruses and filoviruses. We also describe recent computational methods used for the identification of peptide sequences that can interact strongly with protein interfaces, with special emphasis on SARS-CoV-2, using the PePI-Covid19 database.

Survivin, a member of the inhibitor of apoptosis (IAP) protein family, is associated with malignant transformation and is over-expressed in most human tumors. Using lipoplex-mediated transfection, we evaluated the activity of the reporter enzyme, luciferase, expressed from plasmids encoding the enzyme under the control of either the cytomegalovirus (CMV) or survivin promoters, in tumor- and non-tumor-derived human and murine cells. We also examined whether there is a correlation between the survivin promoter-driven expression of luciferase and the level of endogenous survivin. Human cancer cells (HeLa, KB, HSC-3, H357, H376, H413), oral keratinocytes, GMSM-K, and chemically immortalized human mammary cells, 184A-1, were transfected with Metafectene at 2 μl/1 μg DNA. Murine squamous cell carcinoma cells, SCCVII, mouse embryonic fibroblasts, NIH-3T3, and murine immortalized mammary cells, NMuMG, were transfected with Metafectene PRO at 2 μl/1 μg DNA. The expression of luciferase was driven by the CMV promoter (pCMV.Luc), the human survivin promoter (pSRVN.Luc-1430), or the murine survivin promoters (pSRVN.Luc-1342 and pSRVN.Luc-194). Luciferase activity was measured, using the Luciferase Assay System and expressed as relative light units (RLU) per ml of cell lysate or per mg of protein. The level of survivin in the lysates of human cells was determined by ELISA and expressed as ng survivin/mg protein. In all cell lines, significantly higher luciferase activity was driven by the CMV promoter than by survivin promoters. The expression of luciferase driven by the CMV and survivin promoters in murine cells was much higher than that in human cells. The cells displayed very different susceptibilities to transfection; nevertheless, high CMV-driven luciferase activity appeared to correlate with high survivin-promoter driven luciferase expression. The survivin concentration in lysates of cancer cells ranged from 5.8 ± 2.3 to 24.3 ± 2.9 ng/mg protein (mean, 13.7 ng/mg). Surprisingly, elevated survivin protein was determined in lysates of non-tumor-derived cells. Survivin levels for GMSM-K and 184A-1 cells, were 16.7 ± 8.7 and 13.5 ± 6.2 ng/mg protein, respectively. The expression of endogenous survivin did not correlate with the level of survivin promoter-driven transgene activity in the same cells. The expression of survivin by non-tumorigenic, transformed cell lines may be necessary for their proliferative activity. The level of survivin promoter-driven gene expression achieved via liposomal vectors in OSCC cells was too low to be useful in cancer-cell specific gene therapy.