Photophysical and Antibacterial Properties of Porphyrins Encapsulated inside Acetylated Lignin Nanoparticles

Abstract

Lignin has recently attracted the attention of the scientific community, as a suitable raw material for biomedical applications. In this work, acetylated lignin was used to encapsulate five different porphyrins, aiming to preserve their photophysical properties, and for further use as antibacterial treatment. The obtained nanoparticles were physically characterized, through dynamic light scattering size measurement, polydispersity index and zeta potential values. Additionally, the photophysical properties of the nanoparticles, namely UV-vis absorption, fluorescence emission, singlet oxygen production and photobleaching, were compared with those of the free porphyrins. It was found that all the porphyrins were susceptible to encapsulation, with an observed decrease in their fluorescence quantum yield and singlet oxygen production. These nanoparticles were able to exert an effective photodynamic bactericide effect (blue-LED light, 450–460 nm, 15 J/cm2) on Staphylococcus aureus and Escherichia coli. Furthermore, it was achieved a photodynamic bactericidal activity on an encapsulated lipophillic porphyrin, where the free porphyrin failed to diminish the bacterial survival. In this work it was demonstrated that acetylated lignin encapsulation works as a universal, cheap and green material for the delivery of porphyrins, while preserving their photophysical properties.

Porphyrin Photosensitizers Grafted in Cellulose Supports: A Review

“…The results of aPDT accomplished by Leroy-Lhez and co-authors motivated the same authors to extend the strategy on the preparation of photoactive material with acetylated lignin containing other porphyrin derivatives. In 2022 [ 190 ], they reported the encapsulation of 5,10,15,20-tetrakis(4-hydroxyphenyl)porphyrin and four other porphyrin derivatives (5,10,15,20-tetrakis(4-acetyloxyphenyl)porphyrin; 5,10,15,20-tetrakis(4-hydroxyphenyl)porphyrinatozinc(II), 5,10,15,20-tetrakis(4-(3-( N,N,N -trimethylammoniumpropoxy)phenyl)porphyrin tetra-bromide and 5,10,15,20-tetrakis(1-(3-hydroxypropyl)pyridinium-4-yl)porphyrin tetra-bromide) inside acetylated lignin nanoparticles (AcLi).…”

Antibacterial lignin-based nanoparticles and their use in composite materials

“…Later, in the same group, four different derivatives of THPP with different physicochemical characteristics (charge, size, and solubility) were encapsulated into AcLi. 108 The cationic porphyrins were able to reduce the growth of E. coli only in free form, but not aer being encapsulated into AcLi NPs. Interestingly, for some porphyrins, the antibacterial efficacy against S. aureus increased in their encapsulated form in comparison with their free form.…”

Latest trends on photodynamic disinfection of Gram-negative bacteria: photosensitizer’s structure and delivery systems

“…Furthermore, a complete Fig. 4 Core structure of the most prominent PSs families, along with a representative UV-Vis absorbance spectrum [33][34][35][36] family of porphyrins bearing either non-cationic phenyl moieties or methylpyridinium-4-yl moieties (13-16, Fig. 5) was tested against E. coli cells.…”