Synthesis of Metallo-Chromone Porphyrin Nano-Starch Sensitizers as Photodynamic Therapeutics for the Eradication of Enterococci Dental Pathogens

Near-IR nanolignin sensitizers based on pyrene-conjugated chlorin and bacteriochlorin for ROS generation, DNA intercalation and bioimaging

Near-infrared (NIR) fluorescent agents are extensively used for biomedical imaging due to their ability for deep tissue penetration. Tetrapyrrole-based photosensitizers are promising candidates in this regard. Further, the extended conjugation of such macromolecules with chromophores can enhance their fluorescence efficiency and DNA intercalation ability. Herein, pyrene-conjugated NIR photosensitizers, such as chlorin (PyChl) and bacteriochlorin (PyBac), were synthesized from the corresponding pyrene-porphyrin (PyP). The correlation between the theoretical and experimental optical properties (absorption and fluorescence spectroscopy results) was determined using the DFT/TD-DFT computational approach. Next, studies on the photophysical properties, reactive oxygen species (ROS) production, and DNA binding were conducted on these macrocycles to study the effect of pyrene conjugation on the pyrrolic ring. Furthermore, each photosensitizer was loaded into lignin nanoparticles (LNPs) using the solvent-antisolvent method to accomplish fluorescence-guided imaging. The developed near-IR chlorin- and bacteriochlorin-doped lignin nanocarriers (PyChl-LNCs and PyBac-LNCs) exhibited significant in vitro singlet oxygen generation upon red LED light exposure. Moreover, these macrocycle-loaded nanolignin sensitizers showed good fluorescence-guided bioimaging with fungal cells (Candida albicans). Further, the nanoprobes exhibited pH-dependent release profiles for biological applications. These nanolignin sensitizers demonstrated promising potential to be utilized in near-IR image-guided photodynamic therapy.

Lignin-Derived Gold-Titanium Dioxide Nanophotocomposites as Potent Photoactivatable Probes for Microbial Inactivation

The overuse of antibiotics has accelerated antibiotic resistance, and it is a significant global threat to public health. To combat the rising threat of drug-resistant microbes, antimicrobial photodynamic therapy (APDT) has emerged as a promising alternative therapeutic strategy. This study focuses on the synthesis of eco-friendly lignin-derived gold-titanium dioxide nanophotocomposites (L@Au-TiO2 NCs). Lignin was utilized as a sustainable precursor for the synthesis of L@Au-TiO2 NCs. The gold and TiO2 nanoparticles possess inherent photodynamic properties, and thus the developed L@Au-TiO2 NCs exhibit enhanced antimicrobial efficacy due to the synergistic combination of their attributes. The antimicrobial potential of the L@Au-TiO2 NCs was evaluated against various microbial strains (Escherichia coli, Bacillus megaterium, and Candida tropicalis) under dark and green light conditions. The outcome of this study highlights the promising potential of L@Au-TiO2 NCs for photodynamic antimicrobial applications. The L@Au-TiO2 nanophotocomposites could be explored in the fields of medicine and nanotechnology to introduce innovative ideas into the biomedical field.

Mechano-triggered eradication of dentinal tubule biofilm via in situ generation of nanoscale sonosensitizer by the tailored irrigation formulation

The efficient elimination of bacteria within the dentinal tubules has been hindered by the poor deposition and short residence of disinfecting agents. Meanwhile, the current irrigant (e.g., NaClO, 5.25 %) shows severe adverse effects on the surrounding soft tissues because of its inherent high irritancy. To address this issue, this work reports an in situ generated sonosensitizer to handle the biofilm in dentinal tubules with minimal adverse effects. The production of nanoscale sonosensitizer involves the concurrent delivery of H2O2 (0.01 %), ferrocene derivative (Fc), and indocyanine green (ICG). With ultrasound treatment, the reaction between H2O2 and Fc liberated Fe3+ that was further complexed with ICG to generate the nanoscale sonosensitizer in situ, followed by singlet oxygen production for potent disinfecting action. Because the above cascade reactions occur within the confined dentinal tubules, the generated ICG-Fe3+ nanosensitizer would show prolonged retention therein. The anti-bacterial potency of nanosensitizer was demonstrated in petrodish and ex vivo biofilm models. Meanwhile, the transmission electron microscope imaging of biofilm and cytotoxicity assay in L929 fibroblast cells proved the superiority of nanosensitizer against NaClO regarding adverse effects. The current work opens new avenues of biofilm elimination in dentinal tubules, showing a high translation potential.

Design and Synthesis of Metalloporphyrin Nanoconjugates for Dual Light-Responsive Antimicrobial Photodynamic Therapy

Antimicrobial photodynamic therapy (APDT) utilizes photosensitizers (PSs) that eradicate a broad spectrum of bacteria in the presence of light and molecular oxygen. On the other hand, some light sources such as ultraviolet (UVB and UVC) have poor penetration and high cytotoxicity, leading to undesired PDT of the PSs. Herein, we have synthesized conjugatable mesosubstituted porphyrins and extensively characterized them. Time-dependent density functional theory (TD-DFT) calculations revealed that metalloporphyrin EP (5) is a suitable candidate for further applications. Subsequently, the metalloporphyrin was conjugated with lignin-based zinc oxide nanocomposites (ZnOAL and ZnOKL) to develop hydrophilic nanoconjugates (ZnOAL@EP and ZnOKL@EP). Upon dual light (UV + green light) exposure, nanoconjugates showed enhanced singlet oxygen generation ability and also demonstrated pH responsiveness. These nanoconjugates displayed significantly improved APDT efficiency (4-7 fold increase) to treat bacterial infection under dual light irradiation.