Polystyrene and Poly(ethylene glycol)-b-Poly(ε-caprolactone) Nanoparticles with Porphyrins: Structure, Size, and Photooxidation Properties

Abstract

The transport of a photosensitizer to target biological structures followed by the release of singlet oxygen is a critical step in photodynamic therapy. We compared the (photo)­physical properties of polystyrene nanoparticles (TPP@PS) of different sizes and self-assembled poly­(ethylene glycol)-b-poly­(ε-caprolactone) core/shell nanoparticles (TPP@PEG-PCL) with different lengths of copolymer blocks, both suitable for the transport of the tetraphenylporphyrin (TPP) photosensitizer. The singlet oxygen was formed inside both nanoparticles after irradiation with visible light. Its kinetics was controlled by the size of TPP@PS; its lifetime (τΔ) increased with increasing nanoparticle size (from 6.5 to 16 μs) because of hindered diffusion into the external aqueous environment, where it was quickly deactivated. Accordingly, the prolongation of the singlet oxygen-sensitized delayed fluorescence kinetics was found for TPP@PS of high size. The TPP@PEG-PCL self-assemblies allowed for enhanced oxygen diffusion, and the estimated low values of τΔ ≈ 3.7 μs were independent of the size of building blocks. The delayed fluorescence in oxygen-free conditions originating from triplet–triplet annihilation indicated a high mobility of TPP in the PCL core in comparison with fixed molecules in the PS matrix. Photooxidation of uric acid revealed the highest efficacy for TPP@PS of small sizes, whereas the largest TPP@PS exhibited the lowest activity, and the efficacy of TPP@PEG-PCL remained independent of the sizes of the building blocks.

Role of Polymer Micelles in the Delivery of Photodynamic Therapy Agent to Liposomes and Cells

“…At 37 • C, PCL is thus expected to be much softer than PS, providing higher mobility for all species. This has been very recently shown by Mosinger's team who proved that oxygen was able to move more easily in a PCL matrix compared to a PS one [36]. This difference in characteristics of the micellar cores leads to differences of behavior when the micelles are in the presence of target membranes.…”

“…In the case of Pheo delivered by PEO-PS micelles, direct jump and endocytotic mechanisms seem to be the main cell entrance pathways. Very recently Kubát et al [36] clearly showed that the lifetime of singlet oxygen produced by photosensitizer encapsulated in PS is higher (6.4 µs to 16 µs) than that photo-generated in PEO-PCL micelles (3.6-3.8 µs). In PEO-PS, singlet oxygen due to its longer lifetime will have time to diffuse through the nanovector in the vicinity of numerous intracellular targets and to photo-oxidize them.…”

Photodynamic effect of TPP encapsulated in polystyrene nanoparticles toward multi-resistant pathogenic bacterial strains: AFM evaluation

“…The fraction of effectively released O 2 ( 1 Δ g ) is higher for smaller sizes of TPP-NPs (7-162 nm). Accordingly, photooxidation of chemical substrates confirmed higher photoxidation ability for TPP-NPs with smaller sizes of polymer carrier 18 .…”

Solubilization of Charged Porphyrins in Interpolyelectrolyte Complexes: A Computer Study

“…In brief, the primary goal of the paper is obtaining information on the solubilization of porphyrins into IPEC complexes. Knowledge of whether they solubilize in cores of polymeric nanoparticles and whether they associate there is extremely important for medical applications (e.g., for targeted porphyrins delivery into cells or for delayed and isotropic release of singlet oxygen from porphyrin-containing nanoparticles into tissues to be treated by photodynamic therapy [65][66][67][68][69]). As the simulated system is large, we used coarse-grained DPD, which is the only method applicable for this research.…”