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Updated: May 10, 2026
Photodynamic Therapy with Blended Conducting Polymer/Fullerene Nanoparticle Photosensitizers
Published on: October 28, 2015
Exploring Gluconamide-Modified Silica Nanoparticles of Different Sizes as Effective Carriers for Antimicrobial
Ruth Prieto-Montero1, Lucia Herrera1, Maite Tejón1
1Departamento de Química Física, Facultad de Ciencia y Tecnología, Universidad del País Vasco, UPV-EHU, Apartado 644, 48080 Bilbao, Spain.
Abstract:
Antimicrobial resistance (AMR), a consequence of the ability of microorganisms, especially bacteria, to develop resistance against conventional antibiotics, hampering the treatment of common infections, is recognized as one of the most imperative health threats of this century. Antibacterial photodynamic therapy (aPDT) has emerged as a promising alternative strategy, utilizing photosensitizers activated by light to generate reactive oxygen species (ROS) that kill pathogens without inducing resistance. In this work, we synthesized silica nanoparticles (NPs) of different sizes (20 nm, 80 nm, and 250 nm) functionalized with the photosensitizer Rose Bengal (RB) and a gluconamide ligand, which targets Gram-negative bacteria, to assess their potential in aPDT. Comprehensive characterization, including dynamic light scattering (DLS) and photophysical analysis, confirmed the stability and effective singlet oxygen production of the functionalized nanoparticles. Although the surface loading density of Rose Bengal was constant at the nanoparticle external surface, RB loading (in mg/g nanoparticle) was size-dependent, decreasing with increasing nanoparticle diameter. Further, the spherical geometry of nanoparticles favored smaller nanoparticles for antibacterial PDT, as this maximizes the surface contact area with the bacteria wall, with the smallest (20 nm) and intermediate (80 nm) particles being more promising. Bacterial assays in E. coli revealed minimal dark toxicity and significant light-activated phototoxicity for the RB-loaded nanoparticles. The addition of gluconamide notably enhanced phototoxic activity, particularly in the smallest nanoparticles (RB-G-20@SiNP), which demonstrated the highest phototoxicity-to-cytotoxicity ratio. These findings indicate that small, gluconamide-functionalized silica nanoparticles are highly effective for targeted aPDT, offering a robust strategy to combat AMR.
Insights
Small silica nanoparticles loaded with Rose Bengal and a gluconamide ligand show promise for antibacterial photodynamic therapy (aPDT). These targeted nanoparticles effectively kill bacteria with minimal toxicity, offering a new strategy against antimicrobial resistance (AMR).
Area of Science:
- Nanotechnology
- Photochemistry
- Microbiology
Background:
- Antimicrobial resistance (AMR) is a critical global health threat, necessitating novel therapeutic strategies.
- Antibacterial photodynamic therapy (aPDT) offers a promising alternative to conventional antibiotics, generating reactive oxygen species (ROS) to kill pathogens without inducing resistance.
- Photosensitizers like Rose Bengal (RB) are key components in aPDT, but their efficacy can be enhanced through nanoparticle delivery and targeting.
Purpose of the Study:
- To synthesize and characterize silica nanoparticles (NPs) of varying sizes functionalized with Rose Bengal (RB) and a gluconamide ligand for targeted aPDT.
- To evaluate the antibacterial efficacy and phototoxicity of these functionalized NPs against Gram-negative bacteria, particularly *E. coli*.
- To determine the optimal nanoparticle size and ligand presence for enhanced aPDT performance.
Main Methods:
- Synthesis of silica nanoparticles (NPs) with sizes of 20 nm, 80 nm, and 250 nm.
- Functionalization of NPs with Rose Bengal (RB) photosensitizer and a gluconamide (G) targeting ligand.
- Characterization using dynamic light scattering (DLS), photophysical analysis, and bacterial assays to assess stability, singlet oxygen production, phototoxicity, and cytotoxicity.
Main Results:
- RB loading on NPs was size-dependent, decreasing with larger NP diameters.
- Smaller NPs (20 nm and 80 nm) exhibited greater antibacterial phototoxicity due to increased surface contact.
- Gluconamide functionalization significantly enhanced phototoxicity, especially in the smallest NPs (RB-G-20@SiNP), resulting in a high phototoxicity-to-cytotoxicity ratio.
Conclusions:
- Small, gluconamide-functionalized silica nanoparticles loaded with Rose Bengal are highly effective for targeted antibacterial photodynamic therapy.
- These nanoparticles demonstrate potent light-activated antibacterial activity with minimal dark toxicity.
- The developed system presents a robust and promising strategy for combating antimicrobial resistance.
