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Porphyrins and their derivatives have attracted great attention due to their unique properties and diverse functionalities which contribute to their wide applications such as ...catalysis, solar cells, biomedicine and environmental science. It is interesting to note that porphyrin-containing polymers have recently aroused great interest due to the simultaneous presence of both porphyrinic and polymeric characteristics, especially for porphyrin-containing polymers linked by covalent bonds giving well-defined macromolecular architectures, unique self-assembly morphologies and promising applications. Herein, we summarize the different synthetic strategies and self-assembly protocols adopted in recent years to explore various applications of porphyrin-based functional polymers followed by a brief discussion on the challenges and outlooks for future research.
With the discovery of advanced polymerization techniques such as living/controlled radical polymerization and click chemistry, the synthesis of porphyrin-containing functional polymers with well-defined architectures has been greatly developed. Porphyrin molecules tend to form the aggregates based on the self-assembly driving force of π-π stacking. Much attention has been paid to the self-assembly behavior of porphyrin-containing functional polymers, and various nanostructures have been constructed including nano-sized or micron-sized spheres, vesicles, belts, wires, rings, tubes, and rods. Porphyrin-containing functional polymers, with special photochemical and photophysical properties, present significant applications in photovoltaics, catalysis, biological and biomedicine fields. Particularly, the porphyrin-based photosensitizers for photodynamic therapy, porphyrin-conjugated polymers for solar cell devices, porphyrin-based polymeric nanocomposites in catalysis and chemical adsorption and separation have been widely studied. We hope this review on porphyrin-based functional polymers will be beneficial to researchers and newcomers in related fields.
Aggregation‐induced quenching (AIQ) of photosensitizers greatly reduces the quantum yield of singlet oxygen generation and mitigates the efficacy of photodynamic therapy (PDT). We have prepared an ...alternating copolymer starting from 4‐vinylbenzyl‐terminated tetraphenylporphyrin (VBTPP) and maleimide isobutyl polyhedral oligomeric silsesquioxane (MIPOSS), via alternating reversible addition–fragmentation chain transfer (RAFT) polymerization. Porphyrin and POSS are installed on the amphiphilic block copolymers backbone in an alternating fashion and POSS completely inhibits the aggregation of porphyrin units via stacking. The amphiphilic block copolymer can self‐assemble into nanoparticles and its application in PDT treatment was tested. These porphyrin‐containing polymeric nanoparticles display high photochemical yield and phototoxicity in vitro and in vivo, providing a novel strategy to enhance the PDT efficacy.
Nanoparticles formed by self‐assembly of amphiphilic block copolymers were investigated for their potential application in photodynamic therapy. The porphyrin‐containing polymeric nanoparticles display high photochemical yield and phototoxicity in vitro and in vivo, thus providing a novel strategy to enhance the PDT efficacy.
Well-defined hybrid polymers based on polyhedral oligomeric silsequioxane (POSS) with a variety of architectures have been developed, including telechelic polymers, block copolymers and star-shaped ...polymers. The synthesis, self-assembly and properties of this kind of materials are reviewed. Well-defined POSS-containing hybrid polymers can be constructed by living polymerization techniques, such as ring-opening polymerization and living free-radical polymerization or the combination of living polymerization and coupling reactions, such as click chemistry and hydrosilylation. The self-assembly behavior of well-defined POSS-containing hybrid polymers is also described in detail. The POSS-containing hybrid polymers can self-assemble into nano-scaled aggregates in selective solvents, and form nanostructures in bulk. Some of the interesting self-assembly morphologies are remarkably different from those formed from the conventional purely organic amphiphilic polymers. Well-defined POSS-containing hybrid polymers have shown the unexpected properties, which lead to unlimited possibilities for promising applications, such as biomedicine, electronic, optical, magnetic nanodevices, sensors and stimulated catalysts. We highlight several recent examples of these applications.
Drug resistance is a primary obstacle that seriously reduces the therapy efficiency of most chemotherapeutic agents. To address this issue, the photochemical internalization (PCI) was employed to ...help the anticancer drug escape from lysosome and improve their translocation to the nucleus. A pH-sensitive porphyrin-based amphiphilic block copolymer (PEG113-b-PCL54-a-porphyrin) was synthesized, which was acted not only as a carrier for the delivery of DOX but also as a photosensitizer for PCI. PEG113-b-PCL54-a-porphyrin as a drug carrier exhibited a higher drug loading capacity, entrapment efficiency, and DOX release content. The PCI effect of PEG113-b-PCL54-a-porphyrin was studied by confocal laser scanning microscopy, and the results showed that most of DOX could be translocated into the nucleus for DOX-loaded PEG113-b-PCL54-a-porphyrin micelles. Moreover, the IC50 of pH-sensitive DOX-loaded PEG113-b-PCL54-a-porphyrin micelles was much lower than that of its counterpart without pH-responsiveness, DOX-loaded PEG113-b-PCL54-porphyrin micelles. Therefore, this drug delivery system based on pH-sensitive porphyrin-containing block copolymer would act as a potential vehicle for overcoming drug resistance in chemotherapy.
Hybrid organic-inorganic materials comprised of well-defined polymers have been widely recognized for a variety of applications due to their extraordinary properties based on the combination of the ...different building compositions. During the past decades, many kinds of well-defined hybrid polymers with a variety of architectures have been constructed by polymerization in the presence of inorganic compositions, or by the coupling reaction of functional polymers with inorganic nanoparticles. Thus, techniques could be utilized for the preparation of well-defined organic-inorganic hybrid polymers, including controlled living radical polymerizations (CLRP), such as atom transfer radical polymerization (ATRP) and reversible addition-fragmentation chain transfer (RAFT) polymerization. Organic-inorganic hybrid polymers based on polyhedral oligomeric silsesquioxane (POSS), poly(dimethylsiloxane) (PDMS), silica nanoparticles, graphene, carbon nanotubes (CNTs) and fullerene will be discussed in this paper.
Controlled living radical polymerizations, such as ATRP and RAFT polymerization, could be utilized for the preparation of well-defined organic-inorganic hybrid polymers based on POSS, PDMS, silica nanoparticles, graphene, CNTs and fullerene.
Photodynamic therapy (PDT) as a noninvasive and selective treatment technology has presented great potential in cancer prevention and precision medicine, but its therapeutic efficacy is still greatly ...inhibited by the limitations of photosensitizers (PSs) in the microenvironment such as the aggregation caused quenching (ACQ) of PSs. Herein, we proposed an “acid-triggered nanoexpansion” method to further reduce the aggregation of photosensitizers by constructing acetal-based polymeric micelles. A pH-responsive amphiphilic block copolymer, POEGMA-b-PTTMA-co-PTPPC6MA was synthesized by reversible addition–fragmentation chain transfer (RAFT) polymerization and self-assembled into spherical micelles. In the normal physiological environment, the micelles were stable and had good biocompatibility. Upon entry into the acidic microenvironment of the tumor, the acid-responsive hydrophobic 2, 4, 6-trimethoxybenzaldehyde in the micelles hydrolyzed and generated a hydrophilic diol moiety. Although the hydrophility of the micellar core was increased, the assembled structure of block copolymers was not dissociated but expanded. The responsive expansion of the micelles could allow the photosensitizers to well-disperse in the core, whereas more tumor-dissolved oxygen entered the micelles. This phenomenon could provide a better nanoenvironment for photosensitizers to reduce the ACQ of the photosensitizers, leading to more singlet oxygen (1O2) produced under the laser irradiation (650 nm). Both in vitro and in vivo studies have demonstrated that the remarkable photodynamic therapeutic efficacy of acid-responsive micelles could be realized. Thus, the acid-triggered nanoexpansion method might provide more possibilities to develop efficient platforms for treating cancers.
Rheumatoid arthritis (RA) is a chronicautoimmune disease, marked by joint swelling and pain, articular synovial hyperplasia, as well as cartilage and bone destruction. Triptolide (TP) is an ...anti-inflammatory molecule but its use to treat RA is limited due to poor solubility and extremely high toxicity. In this study, by encapsulating TP into a star-shaped amphiphilic block copolymer, POSS-PCL-b-PDMAEMA, we engineered a pH-sensitive TP-loaded nanomedicine (TP@NPs) to simultaneously reduce the toxicity of TP and improve its therapeutic efficacy. TP@NPs shows a uniform spherical structure with a hydrodynamic diameter of ~92 nm and notable pH-responsiveness. In vitro TP@NPs showed reduced cytotoxicity and cell apoptosis of treated RAW264.7 cells compared to free TP. And in vivo intravenous injection of indocyanine green-labeled NPs into a collagen-induced arthritis model in mice showed that the engineered compound had potent pharmacokinetic and pharmacodynamic profiles, while exhibiting significant cartilage-protective and anti-inflammatory effects with a better efficacy and neglible systemic toxicity even at an ultralow dose compared to free TP. These results suggest that TP@NPs may be a safe and effective therapy for RA and other autoimmune diseases.
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The development of more efficient photosensitizers with minimal damage to surrounding normal tissues has been a valuable and challenging subject during photodynamic therapy (PDT). Herein, a ...stimuli-activated porphyrinic photosensitizer (PEG-TPP-DNB; PEG = poly(ethylene glycol); TPP = 5,10,15,20-tetraphenylporphyrin; DNB = 2,4-dinitrobenzene) with capabilities of fluorescence and, remarkably, singlet oxygen quenching was prepared successfully for photodynamic therapy with high efficiency and biosecurity. The amphiphilic PEG-TPP-DNB could be self-assembled into nanomicelles in aqueous media and dissociated in response to reductive thiol such as glutathione. Meanwhile, the fluorescence and singlet oxygen generation of porphyrinic photosensitizer would be activated to regenerate. Moreover, the intracellular uptake and localization effectively confirmed the redox-responsive and activated behavior of PEG-TPP-DNB micelles. The cytotoxicity in vitro revealed that the micelles had low dark toxicity and great phototoxicity, and in vivo bioimaging and antitumor evaluation further indicated that the micelles possessed selective tumor imaging and targeted PDT antitumor effect as well as low systemic toxicity. Overall, this tumor microenvironment-activated photosensitizer system may provide a useful strategy for precise photodynamic therapy.
The treatment of pathogenic bacterial infection has long been the most serious threat to human life and attracted widespread attention. Herein, a supramolecular photosensitizer platform based on ...carboxylatopillar5arene (CP5) and tetrafluorophenyl porphyrin functionalized with a quaternary ammonium group (TFPP‐QA) for combating bacteria and dispersing biofilm via photodynamic treatment is constructed. By introducing the host macrocycle CP5 and host–guest interaction, the supramolecular photosensitizer has great biocompatibility and acid responsiveness. On the one hand, the acid‐triggered dissociation of TFPP‐QA/CP5 could induce the porphyrin photosensitizer to target bacterial cells and disrupt the charge balance of bacterial membranes, enhance the permeability of the bacterial membrane. On the other hand, the TFPP‐QA/CP5 antibacterial platform possesses superb reactive oxygen species (ROS) generation capability under light irradiation, leading to enhanced photodynamic antibacterial efficacy. The in vitro and in vivo studies show that the supramolecular photosensitizers exhibit high antibacterial efficiency and biofilm dissipation effect under 660 nm light irradiation. Therefore, it is anticipated that the rational design and integration of photosensitizers and quaternary ammonium compounds through the supramolecular strategy would provide a promising prospect for clinical photodynamic antimicrobial therapy.
An acid‐triggered supramolecular photosensitizer based on host–guest interaction between carboxylatopillar5arene (CP5) and tetrafluorophenyl porphyrin functionalized with a quaternary ammonium group (TFPP‐QA) is successfully designed for efficient photodynamic anti‐bacteria and biofilm eradication. The supramolecular photosensitizer possesses excellent biocompatibility and acid‐responsiveness, which are beneficial to target bacteria and penetrate biofilms for effective photodynamic antibacterial therapy.
A novel amphiphilic diblock copolymer, PHEMAPOSS-b-P(DMAEMA-co-CMA), was prepared via reversible addition–fragmentation chain transfer (RAFT) polymerization, where PHEMAPOSS block was first ...synthesized using a methacrylate monomer based on polyhedral oligomeric silsesquioxane (HEMAPOSS), and PHEMAPOSS was further utilized to prepare the block copolymer via RAFT copolymerization of 2-(dimethylamino)ethyl methacrylate (DMAEMA) and reduction-cleavable coumarin methacrylate (CMA) monomer. PHEMAPOSS-b-P(DMAEMA-co-CMA) could self-assemble in water to form spherical micelles with POSS core and stimuli-responsive shell. The micelles were cross-linked by photodimerization of coumarin, and then hollow polymeric capsules could be finally obtained via etching the POSS core in the solution of hydrofluoric acid (HF). The morphologies of the micelles and hollow polymeric capsules were well characterized by TEM, SEM, and DLS. The hollow polymeric capsules are responsive to typical physiological stimuli such as pH, and redox potential, and could be further utilized in the encapsulation and release of tetraphenylporphyrin tetrasulfonic acid hydrate (TPPS) for photodynamic therapy (PDT). The in vitro release of TPPS-loaded polymeric capsules allowed a relatively low TPPS release at pH = 7.4. However, a burst release of TPPS was observed in the presence of 10 mM glutathione (GSH) at pH = 5.5. Confocal laser scanning microscopy (CLSM) confirmed that TPPS-loaded polymeric capsules could well improve the internalization rate in MCF-7 cells. According to the result of MTT assay, TPPS-loaded polymeric capsules demonstrated efficient PDT efficacy and low dark toxicity toward MCF-7 cells. Thus, TPPS-loaded polymeric capsules have presented potential application in PDT.
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