Effects of light fractionation and different fluence rates on photodynamic therapy with 5-aminolaevulinic acid in vivo

Abstract

To improve efficacy of photodynamic therapy (PDT) with intravenously administered 5-aminolaevulinic acid (ALA) fractionating the light dose or reducing the light intensity may be a possibility. Therefore, Syrian Golden hamsters were fitted with dorsal skinfold chambers containing an amelanotic melanoma (n ¼ 26). PDT was performed (100 mW cm À2 , 100 J cm À2 , continuously or fractionated, and 25 mW cm À2 , 100 J cm À2 ; continuously or fractionated) using an incoherent light source following i.v. application of ALA. Following fractionated irradiation, the light was paused after 20 J cm À2 for 15 min. Prior to and up to 24 h after PDT tissue, pO 2 was measured using luminescence lifetime imaging. The efficacy was evaluated by measuring the tumour volume of amelanotic melanoma cells grown subcutaneously in the back of Syrian Golden hamsters (n ¼ 36). Only high-dose PDT resulted in a significant decrease of pO 2 . Irrespective of the mode of irradiation only high-dose PDT induced complete remission of all tumours (13 out of 13). It could be shown that low-dose PDT failed to induce a significant decrease of pO 2 . No significant effect of fractionated irradiation was shown regarding the therapeutic efficacy 28 days after PDT. Thus performing a fractionated PDT with ALA or reducing the light intensity seems not to be successful in clinical PDT according to the present data.

A Dual Luminescent Sensor Material for Simultaneous Imaging of Pressure and Temperature on Surfaces

“…[7,28,[41][42][43] Temperature and pressure sensors were successfully applied to aerodynamic research [5,10,44] and dermatology. [3] Most of the approaches are based on the measurement of luminescence intensity instead of lifetime. Regardless of the method applied, temperature correction of the pressure measurement is necessary, because both analytes cause a response.…”

“…Both parameters can be imaged instantly and in high spatial resolution by means of luminescent oxygen-sensitive materials. [1][2][3][4][5] Generally, optical sensors are based on materials responding to an analyte by changing their optical properties like absorption, intensity or wavelength of fluorescence emission, or their luminescence lifetime. The indicators can be encapsulated into polymer particles to control response characteristics or, in case of multi-indicator systems, to minimize interferences.…”

Inativação fotodinâmica de microrganismos

“…PpIX pode ser sintetizada em todas as células contendo mitocôndria 53 . O fenômeno de acumulação do FS em tecidos doentes não é específico para doenças neoplásicas ou pré-neoplásicas.…”

Simulation of fractionated and continuous irradiation in photodynamic therapy: study the differences between photobleaching and singlet oxygen dose deposition

“…Suggested strategies of improving tumor response include lowering fluence rate, fractionating light illumination, and increasing tumor oxygen tension during PDT [9,10]. Splitting the light dose into fractions by pausing the light source for a certain time is supposed to enable reoxygenation of the irradiated tissue and may increase the generation of singlet oxygen thus enhancing PDT [11,12]. A low-dose PDT is supposed to result in slower oxygen consumption and therefore allows oxygen to be continuously supplied compared with high-dose PDT [11][12][13].…”