Photosensitizer absorption coefficient modeling and necrosis prediction during Photodynamic Therapy

Gallium Protoporphyrin Liquid Crystalline Lipid Nanoparticles: A Third-Generation Photosensitizer against Pseudomonas aeruginosa Biofilms

The looming antimicrobial resistance pandemic has encouraged the investigation of antimicrobial photodynamic therapy (aPDT) as a promising technology to combat recalcitrant bacterial infections caused by antibiotic resistant strains. Here, we report on the optimization and effective application of gallium protoporphyrin liquid crystalline lipid nanoparticles (GaPP-LCNP) as a photosensitizer for aPDT against the Gram-negative bacteria P. aeruginosa in both planktonic and biofilm modes of growth. LCNP significantly enhanced the performance of GaPP as photosensitizer by two-fold, which was correlated with higher antibacterial activity, reducing the viability of planktonic P. aeruginosa by 7 log₁₀ using 0.8 µM GaPP-LCNP and a light dose of 17 J.cm⁻². Importantly, GaPP-LCNP also reduced the viability of biofilms by 6 log₁₀ at relatively low light dose of 34.2 J.cm⁻² using only 3 µM GaPP-LCNP. The high antibiofilm activity of GaPP-LCNP at low GaPP-LCNP dose indicated the high efficiency and safety profile of GaPP-LCNP as a promising platform for photodynamic inactivation of recalcitrant infections.

In vitro evaluation of physical and chemical parameters involved in aPDT of Aggregatibacter actinomycetemcomitans

Periodontitis is an infectious disease characterized by the destruction of supporting tissues. Antimicrobial photodynamic therapy (aPDT) has been proposed as an improved method for eliminating microorganisms. Its efficiency depends on the correct use of physical and chemical parameters. Thus, these parameters and their relations were evaluated in this study with the purpose of establishing lethal conditions for combating bacterial agents. Diode lasers and light-emitting diodes (LEDs) were characterized to evaluate the absorption profile and resonance of methylene blue (MB) and toluidine blue O (TBO). The relations between light energy density and photosensitizer absorption were determined. Two methodologies were used to evaluate the effects of aPDT against Aggregatibacter actinomycetemcomitans. LED light exhibited a broad emission spectrum with a peak light wavelength of 637 nm and 99% purity. The resonance intensity of MB was higher with diode laser irradiation, and TBO showed higher resonance intensity with LED irradiation. There was no difference in the absorption profile of photosensitizers using diode lasers or LEDs, and variations in power density did not result in an increasing or decrease in light absorption. A. actinomycetemcomitans was susceptible to photodynamic processes. Emission spectra and peak light wavelengths of light sources combined with the absorption profiles of photosensitizers were the main parameters involved in determining the efficiency of photodynamic effects. Power density did not alter the light absorption of photosensitizers. The association between adequate irradiation characteristics and photosensitizer absorption results in complete inactivation of A. actinomycetemcomitans. In addition, the bactericidal effect was not altered by an increase in energy densities.

Superficial radially resolved fluorescence and 3D photochemical time-dependent model for photodynamic therapy

Photodynamic therapy (PDT) dosimetric tools are crucial for treatment planning and noninvasive monitoring by means of fluorescence. Present approaches consider usually a 1D problem, a simple photochemical process, or a spatially homogeneous photosensitizer. In this work, a radially resolved superficial photosensitizer fluorescence and 3D photochemical time-dependent PDT model are presented. The model provides a time-dependent estimation of tissue fluorescence and the photosensitizer and singlet oxygen 3D concentrations. The model is applied to a basal cell carcinoma treated by Metvix topical photosensitizer protocol. The analysis shows the potentiality in treatment planning and monitoring. The fluorescence results are in agreement with previous measurements.