New incubation protocol can increase drug uptake in antimicrobial photodynamic therapy

Light-driven photosensitizer uptake shows high homogeneity and efficacy

Image source: University of São Paulo

Health

New photodynamic inactivation protocol

The new protocol uses a low dose pre-irradiation during the photosensitizer incubation, resulting in an increased cell photosensitizer uptake, and consequently in a more effective photodynamic therapy. This improved photosensibilization under irradiation was called light-driven uptake. This important finding paves the way for a new incubation protocol to be investigated aiming to increase the efficacy in the photodynamic inactivation field.

Today, there is a great concern about infections caused by microorganism resistant species. One of the main issues is the disseminated use of broad spectrum antibiotics and the resulted selection of resistant species to most or all available drugs. In this context, photodynamic inactivation of microorganisms is a promising treatment for localized infections, where the action mechanism mainly based on highly oxidative reactions has all biomolecules as potential targets. This technique involves coupling light of a proper wavelength with the photosensitizer present in the cell to produce reactive species to induce death.

Optimizing the patient treatment is an important task in antimicrobial photodynamic therapy. With the new protocol, less concentration of photosensitizer or lower light dose is needed to achieve certain damage in the cells. Under these circumstances, not only the cost of the treatment is reduced, as well as the treatment time.

A group of Brazilian researchers planned an in vitro experiment to demonstrate the light-driven uptake increase. Two sets of Candida albicans cells were incubated with Photogem (hematoporphyrin derivative), the first one were kept in the dark during 20 minutes, whereas the second set was light-driven incubated for the same period. Total delivered energy fluence on the irradiated group was of 4 J/cm² at 420 nm. After the incubation time, the two sets of samples received the same irradiation dose of 17 J/cm² at 660 nm.

Higher selectivity and homogeneity

The cells culture treated with the light-driven drug uptake showed a higher photosensitizer concentration as well as a higher homogeneity distribution.

Higher efficacy

The inactivation was 7 times greater than the traditional protocol using the same photosensitizer concentration and photodynamic inactivation light dose.

As a next step, it is important to test the new protocol in bacteria and in mammalian cells.

More details in the article published by Romano, R.A. et. al at Journal of Biophotonics "Light-driven photosensitizer uptake increases Candida albicans photodynamic inactivation".