Caetano P Sabino1, Mark Wainwright2, Carolina Dos Anjos3, Fábio P Sellera3, Maurício S Baptista4, Nilton Lincopan5, Martha S Ribeiro6. 1. BioLambda, Scientific and Commercial LTD, São Paulo, SP, Brazil; Department of Clinical Analysis, School of Pharmaceutical Sciences, University of São Paulo, São Paulo, SP, Brazil. Electronic address: caetanosabino@gmail.com. 2. School of Pharmacy & Biomolecular Sciences, Liverpool John Moores University, Liverpool, UK. 3. Department of Internal Medicine, School of Veterinary Medicine and Animal Science, University of São Paulo, São Paulo, SP, Brazil. 4. Department of Biochemistry, Institute of Chemistry, University of São Paulo, São Paulo, SP, Brazil. 5. Department of Clinical Analysis, School of Pharmaceutical Sciences, University of São Paulo, São Paulo, SP, Brazil; Department of Microbiology, Institute for Biomedical Sciences, University of São Paulo, São Paulo, SP, Brazil. 6. Center for Lasers and Applications, Nuclear and Energy Research Institute, National Commission for Nuclear Energy, São Paulo, SP, Brazil.
Abstract
BACKGROUND: Antimicrobial Photodynamic therapy (A-PDT) has been used to treat infections. Currently, microbial inactivation data is reported presenting survival fraction averages and standard errors as discrete points instead of a continuous curve of inactivation kinetics. Standardization of this approach would allow clinical protocols to be introduced globally, instead of the piecemeal situation which currently applies. METHODS: To this end, we used a power-law function to fit inactivation kinetics and directly report values of lethal doses (LD) and a tolerance factor (T) that informs if inactivation rate varies along the irradiation procedure. A deduced formula was also tested to predict LD for any given survival fraction value. We analyzed the photoantimicrobial effect caused by red light activation of methylene blue (MB-APDT) and by blue light (BL) activation of endogenous microbial pigments against 5 clinically relevant pathogens. RESULTS: Following MB- APDT, Escherichia coli and Staphylococcus aureus cells become increasingly more tolerant to inactivation along the irradiation process (T < 1). Klebsiella pneumoniae presents opposite behavior, i.e., more inactivation is observed towards the end of the process (T > 1). P. aeruginosa and Candida albicans present constant inactivation rate (T˜1). In contrast, all bacterial species presented similar behavior during inactivation caused by BL, i.e., continuously becoming more sensitive to blue light exposure (T > 1). CONCLUSION: The power-law function successfully fit all experimental data. Our proposed method precisely predicted LD and T values. We expect that these analytical models may contribute to more standardized methods for comparisons of photodynamic inactivation efficiencies.
BACKGROUND: Antimicrobial Photodynamic therapy (A-PDT) has been used to treat infections. Currently, microbial inactivation data is reported presenting survival fraction averages and standard errors as discrete points instead of a continuous curve of inactivation kinetics. Standardization of this approach would allow clinical protocols to be introduced globally, instead of the piecemeal situation which currently applies. METHODS: To this end, we used a power-law function to fit inactivation kinetics and directly report values of lethal doses (LD) and a tolerance factor (T) that informs if inactivation rate varies along the irradiation procedure. A deduced formula was also tested to predict LD for any given survival fraction value. We analyzed the photoantimicrobial effect caused by red light activation of methylene blue (MB-APDT) and by blue light (BL) activation of endogenous microbial pigments against 5 clinically relevant pathogens. RESULTS: Following MB- APDT, Escherichia coli and Staphylococcus aureus cells become increasingly more tolerant to inactivation along the irradiation process (T < 1). Klebsiella pneumoniae presents opposite behavior, i.e., more inactivation is observed towards the end of the process (T > 1). P. aeruginosa and Candida albicans present constant inactivation rate (T˜1). In contrast, all bacterial species presented similar behavior during inactivation caused by BL, i.e., continuously becoming more sensitive to blue light exposure (T > 1). CONCLUSION: The power-law function successfully fit all experimental data. Our proposed method precisely predicted LD and T values. We expect that these analytical models may contribute to more standardized methods for comparisons of photodynamic inactivation efficiencies.
Authors: Ana L Tomás; Anna Reichel; Patrícia M Silva; Pedro G Silva; João Pinto; Inês Calado; Joana Campos; Ilídio Silva; Vasco Machado; Roberto Laranjeira; Paulo Abreu; Paulo Mendes; Nabiha Ben Sedrine; Nuno C Santos Journal: J Photochem Photobiol B Date: 2022-07-23 Impact factor: 6.814
Authors: Caetano P Sabino; Fábio P Sellera; Douglas F Sales-Medina; Rafael Rahal Guaragna Machado; Edison Luiz Durigon; Lucio H Freitas-Junior; Martha S Ribeiro Journal: Photodiagnosis Photodyn Ther Date: 2020-09-08 Impact factor: 3.631