Erythrosine-Based PDT of Oral Epithelial Cells Figure 1. Erythrosine Uptake Analysis. Uptake of erythrosine by pre-malignant (DOK) and malignant (H357) oral epithelial cells was analyzed at 37uC and 4uC. (A) Drug uptake kinetics of erythrosine in DOK cells at 37uC and 4uC. (B) Drug uptake kinetics of erythrosine in H357 cells at 37uC and 4uC. The values are means of four replicate determinations 6 S.E.M. Statistical analysis was done via student’s t-test with significance set at P,0.05 (* indicates statistical comparison of 37uC data-points vs. the respective data values of 0 mM erythrosine; # indicates comparison of 4uC data-points vs. the respective data values of 0 mM erythrosine and ** indicates comparison between 37uC data-points and the corresponding 4uC data-points). doi:10.1371/journal.pone.0034475.g001 utilized the photosensitizer, Erythrosine B. Three major advan- tages of erythrosine over certain other photosensitizers are – (1) it is not toxic to the host, (2) it is approved by the FDA for usage in food/food products and (3) it has already been approved for use in dentistry, thereby making its translation into clinic easier (in case of promising pre-clinical data) than possible for other photosen- sitizers, as far as oral cancer is concerned [16,17]. The potential of erythrosine to undergo photochemical reactions and generate singlet oxygen was known previously [18] and it has been used by ourselves as a photosensitizer of bio-films of Streptococcus mutans for the PDT-based cell killing of these oral infectious bacteria [17]. This suggested that erythrosine may also be an effective photosensitizing agent for the treatment of cancer cells [19]. PLoS ONE | www.plosone.org 2 April 2012 | Volume 7 | Issue 4 | e34475