AUTHOR=Maldonado-Carmona Nidia , Marchand Guillaume , Villandier Nicolas , Ouk Tan-Sothea , Pereira Mariette M. , Calvete Mário J. F. , Calliste Claude Alain , Żak Andrzej , Piksa Marta , Pawlik Krzysztof J. , Matczyszyn Katarzyna , Leroy-Lhez Stéphanie 

TITLE=Porphyrin-Loaded Lignin Nanoparticles Against Bacteria: A Photodynamic Antimicrobial Chemotherapy Application

JOURNAL=Frontiers in Microbiology

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2020.606185

DOI=10.3389/fmicb.2020.606185

ISSN=1664-302X

ABSTRACT=<p>The need for alternative strategies to fight bacteria is evident from the emergence of antimicrobial resistance. To that respect, photodynamic antimicrobial chemotherapy steadily rises in bacterial eradication by using light, a photosensitizer and oxygen, which generates reactive oxygen species that may kill bacteria. Herein, we report the encapsulation of 5,10,15,20-tetrakis(4-hydroxyphenyl)-21H,23H-porphyrin into acetylated lignin water-dispersible nanoparticles (<bold>THPP@AcLi</bold>), with characterization of those systems by standard spectroscopic and microscopic techniques. We observed that <bold>THPP@AcLi</bold> retained porphyrin’s photophysical/photochemical properties, including singlet oxygen generation and fluorescence. Besides, the nanoparticles demonstrated enhanced stability on storage and light bleaching. <bold>THPP@AcLi</bold> were evaluated as photosensitizers against two Gram-negative bacteria, <italic>Escherichia coli</italic> and <italic>Pseudomonas aeruginosa</italic>, and against three Gram-positive bacteria, <italic>Staphylococcus aureus</italic>, <italic>Staphylococcus epidermidis</italic>, and <italic>Enterococcus faecalis</italic>. <bold>THPP@AcLi</bold> were able to diminish Gram-positive bacterial survival to 0.1% when exposed to low white LED light doses (4.16 J/cm<sup>2</sup>), requiring concentrations below 5 μM. Nevertheless, the obtained nanoparticles were unable to diminish the survival of Gram-negative bacteria. Through transmission electron microscopy observations, we could demonstrate that nanoparticles did not penetrate inside the bacterial cell, exerting their destructive effect on the bacterial wall; also, a high affinity between acetylated lignin nanoparticles and bacteria was observed, leading to bacterial flocculation. Altogether, these findings allow to establish a photodynamic antimicrobial chemotherapy alternative that can be used effectively against Gram-positive topic infections using the widely available natural polymeric lignin as a drug carrier. Further research, aimed to inhibit the growth and survival of Gram-negative bacteria, is likely to enhance the wideness of acetylated lignin nanoparticle applications.</p>