Water-Soluble Non-Ionic PEGylated Porphyrins: A Versatile Category of Dyes for Basic Science and Applications

This review arises from the need to rationalize the huge amount of information on the structural and spectroscopic properties of a peculiar class of porphyrin derivatives-the non-ionic PEGylated porphyrins-collected during almost two decades of research. The lack of charged groups in the molecular architecture of these porphyrin derivatives is the leitmotif of the work and plays an outstanding role in highlighting those interactions between porphyrins, or between porphyrins and target molecules (e.g., hydrophobic-, hydrogen bond related-, and coordination-interactions, to name just a few) that are often masked by stronger electrostatic contributions. In addition, it is exactly these weaker interactions between porphyrins that make the aggregated forms more prone to couple efficiently with external perturbative fields like weak hydrodynamic vortexes or temperature gradients. In the absence of charge, solubility in water is very often achieved by covalent functionalization of the porphyrin ring with polyethylene glycol chains. Various modifications, including of chain length or the number of chains, the presence of a metal atom in the porphyrin core, or having two or more porphyrin rings in the molecular architecture, result in a wide range of properties. These encompass self-assembly with different aggregate morphology, molecular recognition of biomolecules, and different photophysical responses, which can be translated into numerous promising applications in the sensing and biomedical field, based on turn-on/turn-off fluorescence and on photogeneration of radical species.

Thermo- and redox-responsive dumbbell-shaped copolymers: from structure design to the LCST–UCST transition

Redox- and thermo-responsive dumbbell-shaped copolymers and their self-assembly and stimuli-responsive properties were investigated.

Biodegradable zwitterionic nanoparticles with tunable UCST-type phase separation under physiological conditions

Thermo-responsive polymeric nanoparticles (NPs) are emerging as a powerful tool in nanomedicine for the fabrication of advanced drug delivery systems. In addition to their size and biodegradation rate, phase separation of NPs upon application of a thermal stimulus provides an additional switch to control the rate of release of active components. Among the materials currently developed for biomedical applications, NPs stabilized by zwitterionic polymers are gaining increasing interest due to their high stability and ability to escape the body immune response. Yet, biodegradable zwitterionic NPs with temperature response under physiological conditions are currently not available. Here, we develop a new class of biodegradable zwitterionic NPs that exhibit UCST phase transition in the biological temperature range (T = 30-45 °C) and in physiological solution (i.e. 0.9% w/w NaCl). We design a strategy that relies on the self-assembly of block copolymers produced via reversible addition-fragmentation chain transfer (RAFT) emulsion polymerization. These copolymers comprise a zwitterionic portion exhibiting an upper critical solution temperature (UCST) and a biodegradable hydrophobic block consisting of oligoesters functionalized with a vinyl group. This modular macromolecular architecture allows us to independently control a variety of NP properties by modifying the individual components of the copolymer. In particular, the zwitterionic block of the copolymers controls the UCST-type phase separation behavior, while the number of the oligoester repeating units governs the size of the NPs and the length of the oligoester dictates the degradation rate. After demonstrating the synthesis of highly controlled degradable NPs, we show the potential of this new class of materials in the context of drug delivery by controlling the release of a drug-mimic molecule upon temperature variations in a broad time range from few minutes to 20 hours.

Synthesis of star thermoresponsive amphiphilic block copolymer nano-assemblies and the effect of topology on their thermoresponse

Well-defined multi-arm star thermoresponsive block copolymer nano-assemblies of [poly(N-isopropylacrylamide)-block-polystyrene]_n [(PNIPAM-b-PS)_n] with n = 1, 2, 3 and 4 arms were synthesized by RAFT dispersion polymerization via polymerization-induced self-assembly.

Effect of chain architecture on the swelling and thermal response of star-shaped thermo-responsive (poly(methoxy diethylene glycol acrylate)-block-polystyrene)3 block copolymer films

The effect of chain architecture on the swelling and thermal response of thin films obtained from an amphiphilic three-arm star-shaped thermo-responsive block copolymer poly(methoxy diethylene glycol acrylate)-block-polystyrene ((PMDEGA-b-PS)₃) is investigated by in situ neutron reflectivity (NR) measurements. The PMDEGA and PS blocks are micro-phase separated with randomly distributed PS nanodomains. The (PMDEGA-b-PS)₃ films show a transition temperature (TT) at 33 °C in white light interferometry. The swelling capability of the (PMDEGA-b-PS)₃ films in a D₂O vapor atmosphere is better than that of films from linear PS-b-PMDEGA-b-PS triblock copolymers, which can be attributed to the hydrophilic end groups and limited size of the PS blocks in (PMDEGA-b-PS)₃. However, the swelling kinetics of the as-prepared (PMDEGA-b-PS)₃ films and the response of the swollen film to a temperature change above the TT are significantly slower than that in the PS-b-PMDEGA-b-PS films, which may be related to the conformation restriction by the star-shape. Unlike in the PS-b-PMDEGA-b-PS films, the amount of residual D₂O in the collapsed (PMDEGA-b-PS)₃ films depends on the final temperature. It decreases from (9.7 ± 0.3)% to (7.0 ± 0.3)% or (6.0 ± 0.3)% when the final temperatures are set to 35 °C, 45 °C and 50 °C, respectively. This temperature-dependent reduction of embedded D₂O originates from the hindrance of chain conformation from the star-shaped chain architecture.

Synthesis of well-defined star, star-block, and miktoarm star biodegradable polymers based on PLLA and PCL by one-pot azide–alkyne click reaction

Based on the “arm-first” strategy, ring-opening polymerization (ROP) and one-pot azide–alkyne click reaction, well-defined star-shaped polymers with different architectures have been successfully synthesized, including the star homopolymers four-arm star-shaped polycaprolactone (4sPCL) and four-arm star-shaped poly(l-lactic acid) (4sPLLA), star-block copolymer 4sPCL-b-PLLA and miktoarm star-shaped copolymer PCL₂PLLA₂. The star homopolymers 4sPCL and 4sPLLA were synthesized by a click reaction of an azide small molecule initiator and HC Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> C-PCL or HCC-PLLA. The star-block copolymer 4sPCL-b-PLLA was synthesized by a click reaction of an azide small molecule initiator and the block copolymer HCC-PCL-b-PLLA. The miktoarm star polymer PCL₂PLLA₂ was synthesized by a one-pot azide–alkyne click reaction of simultaneous addition of equal proportions of HCC-PCL and HCC-PLLA. The structures of these star-shaped polymers have been confirmed by NMR, FT-IR and GPC. Furthermore, the melting and crystallization behaviors investigated using DSC and WXRD also confirm the formation of star-shaped polymers with different architectures.

Star, star-block, and miktoarm star biodegradable polymers were synthesized by an “arm-first” strategy, ring-opening polymerization and one-pot azide-alkyne click reaction.

A fluorescent nanoprobe based on cellulose nanocrystals with porphyrin pendants for selective quantitative trace detection of Hg2+

A well-dispersed chemosensor based on cellulose nanocrystals with porphyrin pendants presented high sensitivity and selectivity for trace Hg²⁺ in aqueous solution.

A star-shaped amphiphilic block copolymer with dual responses: synthesis, crystallization, self-assembly, redox and LCST–UCST thermoresponsive transition

The micelles/aggregates that were self-assembled from a star-shaped copolymer presented redox-responsive behaviour and LCST–UCST thermoresponsive transition.