CONICET | Buscador de Institutos y Recursos Humanos

Lightof different wavelengths can be used to obtain a more profitable outcome of photodynamic therapy (PDT), according to the absorption bands of thephotosensitizer (PS). Low-grade cervical intraepithelial neoplasias (CINs) aresuperficial lesions that can be treated with light of shorter wavelength thanred because a large light penetration depth in tissue is not necessary. Wereport a comparative investigation performed to evaluate the efficacy oflight-emitting diodes (LEDs) of different wavelengths in the photodynamictreatment applied to both 2D and 3D HeLa cell spheroid cultures. The spheroidsare utilized as a PDT dosage model, and cell viability is evaluated atdifferent sections of the spheroids by confocal microscopy. Cells incubatedwith m-tetrahydroxyphenyl chlorin are illuminated with LED systems working inthe low fluence range, emitting in the violet (390 ? 415 nm), blue (440-470nm), red (620 ? 645 nm) and deep red (640 ? 670 nm) regions of the lightspectrum at various exposures times (tI) comprised between0.5 and 30 min. PDT experiments performed on both 2D and 3D cell culturesindicate that the PDT treatment outcome is more efficient with violet lightfollowed by red light. Dynamic data from the front displacement velocity oflarge 2D-quasi-radial colonies generated from cell spheroids adhered to thePetri dish bottom as well as the evolution of the 3D growth give furtherinsight about the effect of PDT at each condition. Results from 3D culturesindicate that the penetration of the violet light is appropriate to kill HeLacells several layers below, showing cell damage and death not only in the outerrim of the illuminated spheroids, where a PS accumulation exists, but also inthe more internal region. Results indicate that violet LED light could beuseful to treat CINs involving superficial dysplasia.