Optimization of singlet oxygen production from photosensitizer-incorporated, medically relevant hydrogels.

Áine T De Baróid,Rebecca A Craig,Gavin P Andrews,Colin P Mccoy,Sean P Gorman,Louise Carson,David S Jones

doi:10.1002/jbm.b.33562

Abstract

Photodynamic therapy and photodynamic antimicrobial chemotherapy are widely used, but despite this, the relationships between fluence, wavelength of irradiation and singlet oxygen (1O2) production are poorly understood. To establish the relationships between these factors in medically relevant materials, the effect of fluence on 1O2 production from a tetrakis(4‐N‐methylpyridyl)porphyrin (TMPyP)‐incorporated 2‐hydroxyethyl methacrylate: methyl methacrylate: methacrylic acid (HEMA: MMA:MAA) copolymer, a total energy of 50.48 J/cm2, was applied at varying illumination power, and times. 1O2 production was characterized using anthracene‐9,10‐dipropionic acid, disodium salt (ADPA) using a recently described method. Using two light sources, a white LED array and a white halogen source, the LED array was found to produce less 1O2 than the halogen source when the same power (over 500 − 600 nm) and time conditions were applied. Importantly, it showed that the longest wavelength Q band (590 nm) is primarily responsible for 1O2 generation, and that a linear relationship exists between increasing power and time and the production of singlet oxygen. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 320–326, 2017.

Highlights

Photodynamic antimicrobial chemotherapy (PACT) exploits the production of singlet oxygen (1O2) that occurs when a photosensitizer (PS) is illuminated in the presence of oxygen, to either prevent or reduce the adherence of bacteria to a surface
The power outputs of the LED array and the halogen source, integrated between 500 and 600 nm (Figure 2) were measured to determine if the power outputs of the two light sources varied along the wavelength range of the Q bands of TMPyP (500–600 nm), which are responsible for the production of 1O2
The Q bands of TMPyP, which are responsible for the production of 1O2 lie within this range (500–600 nm), as shown in the UV-visible spectrum of TMPyP incorporated hydroxyethyl methacrylate: methyl methacrylate: methacrylic acid (HEMA):methacrylic acid 99% (MAA):methyl methacrylate 99% (MMA) copolymer, Figure 3

Summary

Introduction

Photodynamic antimicrobial chemotherapy (PACT) exploits the production of singlet oxygen (1O2) that occurs when a photosensitizer (PS) is illuminated in the presence of oxygen, to either prevent or reduce the adherence of bacteria to a surface. The ground state PS (S0) absorbs light energy and is excited into the singlet state (S1). This is transformed, by intersystem crossing, to the excited triplet state, which reacts with molecular oxygen to give 1O2,1 a highly reactive oxygen species (ROS).[2] This type II photodynamic reaction is believed to be the major pathway for photodynamic antimicrobial chemotherapy.[3] A second pathway, the type I photodynamic reaction, involves the transfer of energy to a substrate such as a cell membrane; from this, the transfer of a hydrogen atom to form radicals takes place. When the energy is transferred the PS is regenerated and acts as a catalyst, meaning that many 1O2 molecules can be produced as long as a supply of light and molecular oxygen is maintained.[4]

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