Development of Double Hydrophilic Block Copolymer/Porphyrin Polyion Complex Micelles towards Photofunctional Nanoparticles

The electrostatic complexation between double hydrophilic block copolymers (DHBCs) and a model porphyrin was explored as a means for the development of polyion complex micelles (PICs) that can be utilized as photosensitive porphyrin-loaded nanoparticles. Specifically, we employed a poly(2-(dimethylamino) ethyl methacrylate)-b-poly[(oligo ethylene glycol) methyl ether methacrylate] (PDMAEMA-b-POEGMA) diblock copolymer, along with its quaternized polyelectrolyte copolymer counterpart (QPDMAEMA-b-POEGMA) and 5,10,15,20-tetraphenyl-21H,23H-porphine-p,p',p″,p'''-tetrasulfonic acid tetrasodium hydrate (TPPS) porphyrin. The (Q)PDMAEMA blocks enable electrostatic binding with TPPS, thus forming the micellar core, while the POEGMA blocks act as the corona of the micelles and impart solubility, biocompatibility, and stealth properties to the formed nanoparticles. Different mixing charge ratios were examined aiming to produce stable nanocarriers. The mass, size, size distribution and effective charge of the resulting nanoparticles, as well as their response to changes in their environment (i.e., pH and temperature) were investigated by dynamic and electrophoretic light scattering (DLS and ELS). Moreover, the photophysical properties of the complexed porphyrin along with further structural insight were obtained through UV-vis (200-800 nm) and fluorescence spectroscopy measurements.

Quantum yields of singlet oxygen of tetrakis (4-carboxyphenyl) porphyrin in different solvents

The singlet oxygen quantum yields of photosensitizers in different solvents are very important for photodynamic therapy (PDT). Here, we investigated the singlet oxygen quantum yields of tetrakis (4-carboxyphenyl) porphyrin (TCPP) in various solvents by the iodide method. Results indicate that TCPP has different singlet oxygen formation efficiency in different solvents. When compared to TCPP dissolved in water, TCPP showed higher singlet oxygen yields in methanol and ethanol, but lower singlet oxygen yields in DMF under identical conditions. In particular, TCPP rapidly precipitated in acetone after potassium iodide added in the solution. The salting out effect of TCPP by potassium iodide in acetone was confirmed by re-dissolving the precipitation in water and the characteristic absorption of TCPP was measured. The phenomenon of salting out for TCPP in acetone suggests that acetone is not a good solvent for singlet oxygen generation when evaluated by the iodide method.

Fabrication of Hybrid Polymeric Micelles Containing AuNPs and Metalloporphyrin in the Core

Multi-structure assemblies consisting of gold nanoparticles and porphyrin were fabricated by using diblock copolymer, poly(ethylene glycol)-block-poly(4-vinylpyridine) (PEG-b-P4VP). The copolymer of PEG-b-P4VP was used in the formation of core-shell micelles in water, in which the P4VP block serves as the core, while the PEG block forms the shell. In the micellar core, gold nanoparticle and metalloporphyrin were dispersed through the axial coordination. Structural and morphological characterizations of the complex micelle were carried out by transmission electron microscopy, laser light scatting, and UV-visible spectroscopy. Metalloporphyrin in the complex micelle exhibited excellent photostability by reducing the generation of the singlet oxygen. This strategy may provide a novel approach to design photocatalysts that have target applications in photocatalysis and solar cells.

Self-Assembled Peptide- and Protein-Based Nanomaterials for Antitumor Photodynamic and Photothermal Therapy

Tremendous interest in self-assembly of peptides and proteins towards functional nanomaterials has been inspired by naturally evolving self-assembly in biological construction of multiple and sophisticated protein architectures in organisms. Self-assembled peptide and protein nanoarchitectures are excellent promising candidates for facilitating biomedical applications due to their advantages of structural, mechanical, and functional diversity and high biocompability and biodegradability. Here, this review focuses on the self-assembly of peptides and proteins for fabrication of phototherapeutic nanomaterials for antitumor photodynamic and photothermal therapy, with emphasis on building blocks, non-covalent interactions, strategies, and the nanoarchitectures of self-assembly. The exciting antitumor activities achieved by these phototherapeutic nanomaterials are also discussed in-depth, along with the relationships between their specific nanoarchitectures and their unique properties, providing an increased understanding of the role of peptide and protein self-assembly in improving the efficiency of photodynamic and photothermal therapy.

An enzyme-coupled artificial photosynthesis system prepared from antenna protein-mimetic tyrosyl bolaamphiphile self-assembly

An artificial photosynthesis system coupled with an enzyme was constructed using the nanospherical self-assembly of tyrosyl bolaamphiphiles, which worked as a host matrix exhibiting an antenna effect that allowed enhanced energy transfer to the ZnDPEG photosensitizer. The excited electrons from the photosensitizer were transferred to NAD+ to produce NADH, which subsequently initiated the conversion of an aldehyde to ethanol by alcohol dehydrogenase. Production of NADH and ethanol was enhanced by increasing the concentration of tyrosyl bolaamphiphiles. Spectroscopic investigations proved that the photosensitizer closely associated with the surface of the bolaamphiphile assembly through hydrogen bonds that allowed energy transfer between the host matrix and the photosensitizer. This study demonstrates that the self-assembly of bolaamphiphiles could be applicable to the construction of biomimetic energy systems exploiting biochemical activity.

Cooperative self-assembly of porphyrins with polymers possessing bioactive functions

This review covers recent research on design strategies for the cooperative self-assembly of porphyrins with polymers and its implementation as bioactive assembly.

Suppressing singlet oxygen formation from 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin using polyion complex micelles

The production of ¹O₂ from TPPS can be reduced by the formation of polyion micelles with PMVP₄₁-b-PEO₂₀₅.

Hemin-block copolymer micelle as an artificial peroxidase and its applications in chromogenic detection and biocatalysis

Following an inspiration from the fine structure of natural peroxidases, such as horseradish peroxidase (HRP), an artificial peroxidase was constructed through the self-assembly of diblock copolymers and hemin, which formed a functional micelle with peroxidase-like activity. The pyridine moiety in block copolymer poly(ethylene glycol)-block-poly(4-vinylpyridine) (PEG-b-P4VP) can coordinate with hemin, and thus hemin is present in a five-coordinate complex with an open site for binding substrates, which mimics the microenvironment of heme in natural peroxidases. The amphiphilic core-shell structure of the micelle and the coordination interaction of the polymer to the hemin inhibit the formation of hemin μ-oxo dimers, and thereby enhance the stability of hemin in the water phase. Hemin-micelles exhibited excellent catalytic performance in the oxidation of phenolic and azo compounds by H2O2. In comparison with natural peroxidases, hemin-micelles have higher catalytic activity and better stability over wide temperature and pH ranges. Hemin-micelles can be used as a detection system for H2O2 with chromogenic substrates, and they anticipate the possibility of constructing new biocatalysts tailored to specific functions.