Acetylated Lignins: A Potential Bio‐Sourced Photosensitizer

Abstract

Nowadays, lignins are receiving an increasing interest from the scientific community. Indeed, this biopolymer, formerly considered a waste‐product of the paper industry, appears today as an interesting oil equivalent in many fields. In this context, many chemical modifications of lignins have been presented to valorize this attractive feedstock. However, spectroscopic properties of these modified materials remain poorly studied, in particular their capacity to produce reactive oxygen species (ROS) under light irradiation. Thus, the purpose of this work is to monitor the production of singlet oxygen and superoxide anion under light irradiation of three different acetylated lignins. The results obtained show that those modified lignins can generate ROS levels, allowing to consider a use of these materials as photosensitizers for applications such as photodynamic treatments.

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

“…AcLi was prepared as previously described ( Marchand et al, 2018 ), and their chemical properties are discussed in Supplementary Material 3 . Acetylated lignin nanoparticles were prepared as previously described ( Figueiredo et al, 2017 ; Marchand et al, 2020 ) from an acetone solution ( Figure 1 ).…”

“…It has been demonstrated that AcLi can produce ROS, specifically, singlet oxygen and superoxide anion ( Marchand et al, 2018 ). We extrapolate these observations to the particular case of @AcLi , acting as photosensitizers in aqueous media and producing ROS.…”

“…AcLi was prepared according to previous publications ( Marchand et al, 2018 ). A kraft lignin solution (50 mg/ml) was prepared in an acetic anhydride/dry pyridine (1:1) mixture and stirred at 25°C, under a calcium chloride (CaCl 2 ) trap, for 48 h. Then, the reaction mixture was poured onto 500 ml distilled water, and the precipitate was filtrated, dissolved on chloroform, and washed three times with distilled water.…”

“…It is a polymer of p-coumaryl alcohol, coniferyl alcohol, and sinapyl alcohol units, whose proportions vary according to its botanic origin ( Faix, 1991 ). Due to its chemical nature, it can withstand several chemical modifications, either through the creation of new chemically active sites or through the substitution of the already available ones ( Calvo-Flores and Dobado, 2010 ; Duval and Lawoko, 2014 ; Wang et al, 2016 ; Figueiredo et al, 2018 ; Marchand et al, 2018 ). In addition to chemical modifications, different methods for the preparation of lignin-based nanomaterials had been developed.…”

“…Among all the possible lignin modifications, lignin acetylation is widely described in the literature ( Qian et al, 2014b ). For instance, recent reports have demonstrated that acetylated Kraft and Organosolv lignins ( AcLi ) work as weak photosensitizers ( Marchand et al, 2018 ) and that AcLi is also able to form spherical nanoparticles ( Qian et al, 2014a , b ; Marchand et al, 2020 ), further demonstrating the capability to transport active molecules ( Zhou et al, 2019 ; Marchand et al, 2020 ).…”