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Abstract
BackgroundPhotodynamic therapy (PDT) is an anticancer treatment that utilizes the interaction of light and a photosensitiser (PS), promoting tumour cell death mediated by generation of reactive oxygen species. In this study, we evaluated the in vitro photoactivity of four meso-substituted porphyrins and a porphyrin coupled to a fullerene.MethodsThe cell line employed was the LM3 mammary adenocarcinoma, and the PS with the best photokilling activity was administered to mice bearing the LM3 subcutaneously implanted adenocarcinoma. The TEMCP4+ porphyrin and its analogue TEMCC4+ chlorine contain four identical carbazoyl substituents at the meso positions of the tetrapyrrolic macrocycle and have A4 symmetry. The TAPP derivative also has A4 symmetry, and it is substituted at the meso positions by aminopropoxy groups. The DAPP molecule has ABAB symmetry with aminopropoxy and the trifluoromethyl substituents in trans positions. The TCP-C604+ dyad is formed by a porphyrin unit covalently attached to the fullerene C60.ResultsThe PSs are taken up by the cells with the following efficiency: TAPP> TEMCP4+ = TEMCC4+ > DAPP >TCP-C604+, and the amount of intracellular PS correlates fairly with the photodamage degree, but also the quantum yields of singlet oxygen influence the PDT outcome. TAPP, DAPP, TEMCC4+ and TEMCP4+ exhibit high photoactivity against LM3 mammary carcinoma cells, being TAPP the most active. After topical application of TAPP on the skin of mice bearing LM3 tumours, the molecule is localized mainly in the stratum corneum, and at a lower extent in hair follicles and sebaceous glands. Systemic administration of TAPP produces a tumour: normal skin ratio of 31.4, and high accumulation in intestine and lung.ConclusionThe results suggest a potential use of topical TAPP for the treatment of actinic keratosis and skin adnexal neoplasms. In addition, selectivity for tumour tissue after systemic administration highlights the selectivity of and potentiality of TAPP as a new PS.
Highlights
Photodynamic therapy (PDT) is an anticancer treatment that utilizes the interaction of light and a photosensitiser (PS), promoting tumour cell death mediated by generation of reactive oxygen species
Photodynamic therapy (PDT) is a technique that involves the use of a photosensitising substance (PS), which after being irradiated with a suitable wavelength in the presence of oxygen, undergoes photoactivation and reacts with cellular molecules promoting cell death mediated by generation of reactive oxygen species [1]
This work aimed to evaluate the in vitro photoactivity of four meso-substituted compounds and a porphyrin coupled to a fullerene structure
Summary
Photodynamic therapy (PDT) is an anticancer treatment that utilizes the interaction of light and a photosensitiser (PS), promoting tumour cell death mediated by generation of reactive oxygen species. Photodynamic therapy (PDT) is a technique that involves the use of a photosensitising substance (PS), which after being irradiated with a suitable wavelength in the presence of oxygen, undergoes photoactivation and reacts with cellular molecules promoting cell death mediated by generation of reactive oxygen species [1]. First-generation PSs, such as Photofrin, exhibit poor clearance and lacks long-wavelength absorption. The synthesis of second-generation PSs moved towards modified tetrapyrrolic compounds, such as benzoporphyrin, chlorin and porphycene, which have a more intense long-wavelength absorption [5]. There is still an increasing need to develop new PSs showing better tumour selectivity, less cutaneous photosensitisation and increased photoactivity. Adequate PSs are expected to have a high absorption coefficient in the visible region of the spectrum and efficiently produce singlet oxygen [6]
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