Water-Soluble Fullerene Monoderivatives for Biomedical Applications

Monoderivatives of fullerenes functionalized with hydrophilic groups make them water soluble, while preserving the hydrophobic fullerene cage. This class of molecules have intriguing biomedical applications, including drug delivery, photodynamic therapy (PDT), antiviral and antimicrobial activity and reactive oxygen species (ROS)-scavenging abilities. In this Concept we discuss the synthesis and biomedical applications of water-soluble fullerene monoderivatives and their biological behavior based on their structures.

Origin of intersystem crossing in highly distorted organic molecules: a case study with red light-absorbing N,N,O,O-boron-chelated Bodipys

To explore the relationship between the twisted π-conjugation framework of aromatic chromophores and the efficacy of intersystem crossing (ISC), we have studied a N,N,O,O-boron-chelated Bodipy derivative possessing a severely distorted molecular structure. Surprisingly, this chromophore is highly fluorescent, showing inefficient ISC (singlet oxygen quantum yield, Φ_Δ = 12%). These features differ from those of helical aromatic hydrocarbons, where the twisted framework promotes ISC. We attribute the inefficient ISC to a large singlet-triplet energy gap (ΔE_S1/T1 = 0.61 eV). This postulate is tested by critical examination of a distorted Bodipy having an anthryl unit at the meso-position, for which Φ_Δ is increased to 40%. The improved ISC yield is rationalized by the presence of a T₂ state, localized on the anthryl unit, with energy close to that of the S₁ state. The electron spin polarization phase pattern of the triplet state is (e, e, e, a, a, a), with the T_z sublevel of the T₁ state overpopulated. The small zero-field splitting D parameter (-1470 MHz) indicates that the electron spin density is delocalized over the twisted framework. It is concluded that twisting of π-conjugation framework does not necessarily induce ISC, but S₁/T_n energy matching may be a generic feature for increasing ISC for a new-generation of heavy atom-free triplet photosensitizers.

Recent advances in Prussian blue-based photothermal therapy in cancer treatment

Malignant tumours are a serious threat to human health. Traditional chemotherapy has achieved breakthrough improvements but also has significant detrimental effects, such as the development of drug resistance, immunosuppression, and even systemic toxicity. Photothermal therapy (PTT) is an emerging cancer therapy. Under light irradiation, the phototherapeutic agent converts optical energy into thermal energy and induces the hyperthermic death of target cells. To date, numerous photothermal agents have been developed. Prussian blue (PB) nanoparticles are among the most promising photothermal agents due to their excellent physicochemical properties, including photoacoustic and magnetic resonance imaging properties, photothermal conversion performance, and enzyme-like activity. By the construction of suitably designed PB-based nanotherapeutics, enhanced photothermal performance, targeting ability, multimodal therapy, and imaging-guided cancer therapy can be effectively and feasibly achieved. In this review, the recent advances in PB-based photothermal combinatorial therapy and imaging-guided cancer therapy are comprehensively summarized. Finally, the potential obstacles of future research and clinical translation are discussed.

Heavy Atom-Free Triplet Photosensitizers: Molecular Structure Design, Photophysical Properties and Application in Photodynamic Therapy

Photodynamic therapy (PDT) is a promising method for the treatment of cancer, because of its advantages including a low toxicity, non-drug-resistant character, and targeting capability. From a photochemical aspect, a critical property of triplet photosensitizers (PSs) used for PDT reagents is the intersystem crossing (ISC) efficiency. Conventional PDT reagents are limited to porphyrin compounds. However, these compounds are difficult to prepare, purify, and derivatize. Thus, new molecular structure paradigms are desired to develop novel, efficient, and versatile PDT reagents, especially those contain no heavy atoms, such as Pt or I, etc. Unfortunately, the ISC ability of heavy atom-free organic compounds is usually elusive, and it is difficult to predict the ISC capability of these compounds and design novel heavy atom-free PDT reagents. Herein, from a photophysical perspective, we summarize the recent developments of heavy atom-free triplet PSs, including methods based on radical-enhanced ISC (REISC, facilitated by electron spin-spin interaction), twisted π-conjugation system-induced ISC, the use of fullerene C₆₀ as an electron spin converter in antenna-C₆₀ dyads, energetically matched S₁/T_n states-enhanced ISC, etc. The application of these compounds in PDT is also briefly introduced. Most of the presented examples are the works of our research group.

Converting bile acids into mitocans

Cholic acid (1, CD), deoxycholic (3, DCA), chenodeoxycholic acid (5, CDCA), ursodeoxycholic acid (7, UDCA), and lithocholic acid (9, LCA) were acetylated and converted into their piperazinyl spacered rhodamine B conjugates 16-20. While the parent bile acids showed almost no cytotoxic effects for several human tumor cell lines, the piperazinyl amides were cytostatic but an even superior effect was observed for the rhodamine B conjugates. Extra staining experiments showed these compounds as mitocans; they led to a cell arrest in the G1 phase.

Recent advances in metal-organic frameworks and their composites for the phototherapy of skin wounds

Wound healing is a complex process that greatly affects the normal physiological activities of genes, proteins, signaling pathways, tissues, and organs. Bacterial infection could easily lead to serious tissue damage during wound healing, thus countering wound infections becomes a major challenge for clinicians and nursing professionals. At present, the exploration of highly effective, low toxicity and environment friendly methods for wound healing is attracting considerable interest all over the world. Recently, metal-organic frameworks (MOFs) have presented great potential for treating wound infections due to their unique characteristics of diversified functionality, large specific surface area, and high biocompatibility. These properties endow MOFs/MOF-based composites with an outstanding anti-wound infection effect, which is mainly attributed to the continuously released active components and the exerted catalytic activity with the assistance of phototherapy. In this review, the current progress of MOFs/MOF-based composites for the phototherapy of skin wounds is presented. Firstly, we illustrate the pathophysiological mechanisms, principles of phototherapy and the conventional methods for wound healing. Then, the structures and characteristics of MOFs are systematically summarized. Moreover, the review highlights the recent advances in the application of phototherapy for wound healing (including photodynamic therapy, photothermal therapy, and synergistic therapy) based on various MOFs/MOF-based composites. Finally, the challenges and perspectives are provided for the further development of MOF-based materials for medical application.

Hollow Mesoporous Manganese Oxides: Application in Cancer Diagnosis and Therapy

The precision, minimal invasiveness, and integration of diagnosis and treatment are critical factors for tumor treatment at the present. Although nanomedicine has shown the potential in tumor precision treatment, nanocarriers with high efficiency, excellent targeting, controlled release, and good biocompatibility still need to be further explored. Hollow mesoporous manganese oxides nanomaterials (HM-MONs), as an efficient drug delivery carrier, have attracted substantial attention in applications of tumor diagnosis and therapy due to their unique properties, such as tumor microenvironment stimuli-responsiveness, prominent catalytic activity, excellent biodegradation, and outstanding magnetic resonance imaging ability. The HM-MONs can not only enhance the therapeutic efficiency but also realize multimodal diagnosis of tumors. Consequently, it is necessary to introduce applications based on HM-MONs in cancer diagnosis and therapy. In this review, the representative progress of HM-MONs in synthesis is discussed. Then, several promising applications in drug delivery, bio-imaging, and bio-detection are highlighted. Finally, the challenges and perspectives of the anticancer applications are summarized, which is expected to provide meaningful guidance on further research.

Antibody guided activatable NIR photosensitizing system for fluorescently monitored photodynamic therapy with reduced side effects

Photodynamic therapy (PDT) utilizing an organic dye (photosensitizer) capable of killing cancer cells in the body upon light irradiation is one of the promising non-invasive treatment modalities for many cancers. A known drawback of PDT is a side-effect caused by existing photosensitizers to organs due to insufficient specificity and accidental light exposure of a patient during the delivery of the photosensitizer in the bloodstream. To overcome this issue, we developed a novel antibody guided, activatable photosensitizing system, Ab-mI₂XCy-Ac, where the trastuzumab (Ab) is linked to the non-active (not phototoxic and not fluorescent) dye, mI₂XCy-Ac, that contains the hydroxyl group protected by acetyl (Ac). This targeting, non-photo-active conjugate was shown to be safely (without detectable side-effects) delivered to the targeted tumor, where it is activated by the esterase-mediated acetyl group cleavage and effectively treats the tumor upon NIR light irradiation. It was demonstrated in the Her2 positive BT-474 tumor mouse model that the treatment efficacy of the activatable photosensitizing system is about the same as for the permanently active photosensitizer, Ab-mI₂XCy, while the side-effects are noticeably reduced. In addition, this activatable system enables fluorescence monitoring of the photosensitizer activation events.

Near-infared upper phenyl-fused BODIPY as photosensitizer for photothermal-photodynamic therapy

BODIPY scaffolds by introducing ring-fused segment promoted bathochromic-shift spectrum and enhanced intersystem crossing capability by a twisted structure. In this work, we designed the upper phenyl-fused BODIPY with 4-dimethylaminostyryl groups...

Photosensitized Oxidation of Intracellular Targets: Understanding the Mechanisms to Improve the Efficiency of Photodynamic Therapy

The development of improved photosensitizers is a key aspect in the establishment of photodynamic therapy (PDT) as a reliable treatment modality. In this chapter, we discuss how molecular design can lead to photosensitizers with higher selectivity and better efficiency, with focus on the importance of specific intracellular targeting in determining the cell death mechanism and, consequently, the PDT outcome.

The Synthesis of Protein-Encapsulated Ceria Nanorods for Visible-Light Driven Hydrogen Production and Carbon Dioxide Reduction

1D rare earth-based nanomaterials have attracted significant attention due to their excellent photo/electro-catalytic performance. The corresponding challenge is how to synthesize shape and size-controlled nanostructures in an easy scale-up way. Herein, the authors present a facile one-step strategy to design 1D multifunctional protein-encapsulated cerium oxide nanorods (PCNRs) by utilizing bovine serum albumin as an efficient biotemplate. Remarkably, the PCNRs exhibit high chemical and interfacial adhesion stability with intriguing properties, resulting in an exceptionally high activity towards H₂ evolution and CO₂ reduction. The photocatalytic activity of PCNRs to produce H₂ is about 10 times higher than conventional CeO₂ nanorods. The incorporation of rhodamine B into the PCNRs brings unprecedentedly high photocatalytic H₂ evolution rate being 123 times higher than that of conventional CeO₂ nanorods. Further the presence of the -NH₂ groups on the PCNRs facilitated the adsorption and activation of CO₂ and efficiently suppressed the proton reduction, and as a result, the PCNRs photocatalyst is highly active in converting CO₂ to CO and CH₄ , with the evolution rates being 50 and 83 times higher than those of conventional CeO₂ nanorods, respectively. Achieving such efficient photocatalyst is a critical step toward practical production of high-value renewable fuels using solar energy.

Controlling the triplet states and their application in external stimuli-responsive triplet-triplet-annihilation photon upconversion: from the perspective of excited state photochemistry

The property of organic light-responsive materials is determined by their electronic excited states to a large extent, for instance, the radiative decay rate constants, redox potentials, and lifetimes. Tuning the excited state properties with external stimuli will lead to versatile functional materials; a representative example is the fluorescence molecular probes, in which the singlet excited states are controlled by the external stimuli, i.e., by interaction with the analytes. In comparison, controlling the triplet excited state with external stimuli has been rarely reported, although it is also crucial for the development of novel materials for targeted photodynamic therapy (PDT) reagents and phosphorescent molecular probes. The reported results show that the principles used in singlet excited state tuning are unable to be simply applied to the triplet excited state. In this review article, we summarized the recent results on controlling the triplet excited states by the external stimuli (chemical or light), and the application of the triplet state tuning in the chemical/light controllable triplet-triplet-annihilation upconversion (TTA UC). We discussed the methods for the control of the triplet states, as well as singlet excited state, for the purpose of controlling the TTA UC. Both successful and unsuccessful methods are discussed. This information is helpful for understanding the photophysical processes in which the triplet excited state is involved, and the development of novel external stimuli-responsive triplet photosensitizers.

Nanoscale metal-organic frameworks for tumor phototherapy

Metal-Organic Frameworks (MOFs) are constructed from metal ions/cluster nodes and functional organic ligands through coordination bonds. Owing to the advantages of diverse synthetic methods, easy modification after synthesis, large adsorption capacity for heavy metals, and short equilibrium time, considerable attention has recently been paid to MOFs for tumor phototherapy. Through rational tuning of metal ions and ligands, MOFs present abundant properties for various applications. Light-triggered phototherapy, including photodynamic therapy (PDT) and photothermal therapy (PTT), is an emerging cancer treatment approach. Nanosized MOFs can be applied as phototherapeutic agents to accomplish phototherapy with excellent phototherapeutic efficacy. This review outlines the latest advances in the field of phototherapy with various metal ion-based MOFs.

Rational design of high performance nanotheranostics for NIR-II fluorescence/magnetic resonance imaging guided enhanced phototherapy

Nanotheranostics, which can provide great insight into cancer therapy, has been deemed as a promising technology to settle the unmet medical needs. The rational design of high performance nanotheranostics with multiple complementary imaging features and satisfactory therapeutic efficacy is particularly valuable. Herein, versatile nanotheranostic agents DPPB-Gd-I NPs were fabricated by using gadolinium-diethylenetriaminepentaacetic acid chelates and an iodine-decorated copolymer as encapsulation matrixes to encapsulate a polymer DPPB through one-step nanoprecipitation. We have demonstrated that such nanoagents are able to efficiently damage tumors under single dose injection and NIR laser illumination conditions due to the enhanced photodynamic therapy and enhanced photothermal therapy (the tumor inhibition rate was as high as 94.5%). Moreover, these nanoagents can be utilized as dual-modal NIR-II fluorescence/magnetic resonance imaging probes for tumor diagnosis with high sensitivity, deep tissue penetration, and excellent spatial resolution. Overall, this work offers a powerful tactic to fabricate high performance nanotheranostics for clinical application.

Organic/inorganic nanohybrids rejuvenate photodynamic cancer therapy

The development of nanotechnology has changed the 100-year-old paradigm of photodynamic therapy (PDT), in which organic/inorganic hybrid nanomaterials have made great contributions. In this review, we first describe the mechanisms of PDT and discuss the limitations of conventional PDT. On this basis, we summarize recent progress in organic/inorganic nanohybrids-based photodynamic agents, highlighting how these nanohybrids can be programmed to overcome challenges in photodynamic cancer therapy.

Development of multifunctional nanocomposites for controlled drug delivery and hyperthermia

Magnetic nano/micro-particles based on clinoptilolite-type of natural zeolite (CZ) were fabricated and were expected to act as carriers for controlled drug delivery/release, imaging and local heating in biological systems. Adsorption of rhodamine B, sulfonated aluminum phthalocyanine and hypericin by magnetic CZ nano/micro-particles was investigated, as was the release of hypericin. Using an alternating magnetic field, local temperature increase by 10 °C in animal tissue with injected magnetic CZ particles was demonstrated. In addition, the CZ-based particles have been found to exhibit an anti-amyloidogenic effect on the amyloid aggregation of insulin and lysozyme in a dose- and temperature-dependent manner. Therefore, the mesoporous structure of CZ particles provided a unique platform for preparation of multifunctional magnetic and optical probes suitable for optical imaging, MRI, thermo- and phototherapy and as effective containers for controlled drug delivery. We concluded that magnetic CZ nano/micro-particles could be evaluated for further application in cancer hyperthermia therapy and as anti-amyloidogenic agents.

NIR Photosensitizer for Two-Photon Fluorescent Imaging and Photodynamic Therapy of Tumor

Preparation of near-infrared (NIR) emissive fluorophore for imaging-guided PDT (photodynamic therapy) has attracted enormous attention. Hence, NIR photosensitizers of two-photon (TP) fluorescent imaging and photodynamic therapy are highly desirable. In this contribution, a novel D-π-A structured NIR photosensitizer (TTRE) is synthesized. TTRE demonstrates near-infrared (NIR) emission, good biocompatibility, and superior photostability, which can act as TP fluorescent agent for clear visualization of cells and vascular in tissue with deep-tissue penetration. The PDT efficacy of TTRE as photosensitizer is exploited in vitro and in vivo. All these results confirm that TTRE would serve as potential platform for TP fluorescence imaging and imaging-guided photodynamic therapy.

3,5-Anthryl-Bodipy dyad/triad: Preparation, effect of F-B-F induced conformation restriction on the photophysical properties, and application in triplet-triplet-annihilation upconversion

We prepared a series of compact Bodipy-anthryl electron donor/acceptor triads and dyads by attaching anthryl moieties at the 3-,5-positions of the Bodipy core, with a novel conformation restriction approach, to study the spin-orbit charge transfer intersystem crossing (SOCT-ISC). The conformation restrictions are imposed by the BF₂ unit of Bodipy without invoking the previously reported method with 1,7-dimethyl or 1,3-dimethyl groups. Our new approach shows a few advantages, including the stronger electron accepting ability of the methyl-free Bodipy core (reduction potential anodically shifted by +0.3 V vs the methylated Bodipy), red-shifted absorption (by 21 nm), and longer triplet state lifetime (372 µs vs 126 µs). The effects of the different mutual orientations of the electron donor and acceptor on ultraviolet-visible absorption, fluorescence, triplet state quantum yields, and lifetimes were studied. Triads with orthogonal geometries show higher singlet oxygen quantum yields (Φ_Δ = 37%) than those with more coplanar geometries. Since the non-radiative decay for the S₁ state is significant in the parent Bodipy chromophore (Φ_F = 6.0%), we propose that in dyads/triads, the charge separation and recombination-induced ISC outcompete the non-radiative decay to the ground state, which is new in the study of SOCT-ISC. Density functional theory computation indicated a shallow torsion potential energy curve as compared to the meso-anthryl-Bodipy dyad analog, which may contribute a low triplet state quantum yield of the new dyads/triads. Triplet-triplet annihilation upconversion was performed with the electron donor/acceptor dyads as the triplet photosensitizer, with an upconversion quantum yield of 12.3%.

Aza-BODIPY-Based Nanomedicines in Cancer Phototheranostics

Cancer phototheranostics, composed of optical diagnosis and phototherapy (including photodynamic therapy and photothermal therapy), is a promising strategy for precise tumor treatment. Due to the unique properties of near-infrared absorption/emission, high reactive oxygen species generation, and photothermal conversion efficiency, aza-boron-dipyrromethene (aza-BODIPY), as an emerging organic photosensitizer, has shown great potential for tumor phototheranostics. By encapsulating aza-BODIPY photosensitizers within functional amphiphilic polymers, we can afford hydrophilic nanomedicines that selectively target tumor sites via an enhanced permeability and retention effect, thereby efficiently improving diagnosis and therapeutic efficacy. Herein, in this spotlight article, we attempt to highlight our recent contributions in the development of aza-BODIPY-based nanomedicines, which comprises three main sections: (1) to elucidate the design strategy of aza-BODIPY photosensitizers and corresponding nanomedicines; (2) to overview their photophysical properties and biomedical applications in phototheranostics, including fluorescence imaging, photoacoustic imaging, photodynamic therapy, photothermal therapy, and synergistic therapy; and (3) to depict the challenges and future perspectives of aza-BODIPY nanomedicines. It is believed that this Spotlight on Applications article would illuminate the way of developing new aza-BODIPY nanomedicines as well as other organic photosensitizer-based nanomedicines for future clinical translation.

Visualization photofragmentation-induced rhodamine B release from gold nanorod delivery system by combination two-photon luminescence imaging with correlation spectroscopy

Plasmon-enhanced gold nanorod (AuNR) with high photothermal conversion efficiency is a promising light-controllable nanodrug delivery system for cancer therapy. Understanding the mechanism for the light-controllable drug release of AuNR delivery systems is important for the development of nanomedicine. In this study, the rhodamine B (RB) released from AuNR-RB nanodelivery system was quantitated and visualized by using two-photon luminescence (TPL) imaging combined with correlation spectroscopy. The photofragmentation of AuNR induced by femtosecond pulsed laser was revealed by TPL correlation spectroscopy when the laser energy was above the thermal damage threshold of AuNR, and the RB released from this nanodrug delivery system was visualized by TPL imaging. Furthermore, the photofragmentation-induced release of RB from AuNR-RB nanodelivery system was visualized in living MCF-7 breast cancer cells by TPL imaging combined with correlation spectroscopy. These results provided a novel optical approach to quantify the release of drugs from gold nanocarriers in complex biological media.

Recent advances in pH-responsive nanomaterials for anti-infective therapy

The design and synthesis of pH-responsive antibacterial nanomaterials and their applications in anti-infective therapy.

FRET-based sensor for visualizing pH variation with colorimetric/ratiometric strategy and application for bioimaging in living cells, bacteria and zebrafish

Acid–base balance plays a key role in regulating biological processes, and the cells must stabilize the pH within a certain range, and pH instability will cause a series of diseases.

Diketopyrrolopyrrole–fullerene C60 architectures as highly efficient heavy atom-free photosensitizers: synthesis, photophysical properties and photodynamic activity

New diketopyrrolopyrrole–C₆₀ architectures were synthesized as potential heavy atom-free photosensitizers in photodynamic inactivation of microorganisms.

Biodegradable Hollow MoSe2/Fe3O4 Nanospheres as the Photodynamic Therapy-Enhanced Agent for Multimode CT/MR/IR Imaging and Synergistic Antitumor Therapy

Photodynamic therapy (PDT) is considered as one of the most effective cancer treatment strategies because of its minimally invasive and high efficiency. On account of the correlation between PDT and photocatalytic oxidation, the hollow MoSe₂/Fe₃O₄ (MF-2) nanoheterostructure was constructed to enhance PDT as shown in this paper. The size and the hollow structure can be well controlled by the addition of F-127. MoSe₂/Fe₃O₄ reveals the twofold reactive oxygen species (ROS) generation in contrast to the pure MoSe₂, which is ascribed to the effective separation of photogenic charges. The novel hollow structure also supplies a lot of cavities for perfluorocarbon (PFC) and O₂ loading, and O₂@PFC@MF-2 can effectively overcome the hypoxic microenvironment to further cause more than 3 times ROS production. Moreover, the narrow band gap and hollow structure also make sure that the strong near-infrared (NIR) light absorption and high photothermal conversion efficiency is as high as 66.2%. Furthermore, the combination of Fe₃O₄ can further accelerate the effective biodegradation capacity of MF-2 because of the repeated endogenous redox reaction to form water-soluble Mo^VI-oxide species. Meanwhile, doxorubicin (Dox, anticancer drug) was assembled onto the MF-2@PEG nanomaterials through π-π staking and electrostatic interaction for chemotherapy. O₂@PFC@MF-2@PEG/Dox possesses the potential application in triple-model computed tomography, magnetic resonance, and infrared (CT/MR/IR) imaging-guided photothermal/photodynamic/chemotherapy (PTT/PDT/chemotherapy) nanodiagnosis platforms.

Light-Harvesting Antenna and Proton-Activated Photodynamic Effect of a Novel BODIPY-Fullerene C60 Dyad as Potential Antimicrobial Agent

A covalently linked BODIPY-fullerene C₆₀ dyad (BDP-C₆₀ ) was synthesized as a two-segment structure, which consists of a visible light-harvesting antenna attached to an energy or electron acceptor moiety. This structure was designed to improve the photodynamic action of fullerene C₆₀ to inactivate bacteria. The absorption spectrum of BDP-C₆₀ was found to be a superposition of the spectra of its constitutional moieties, whereas the fluorescence emission of the BODIPY unit was strongly quenched by the fullerene C₆₀ . Spectroscopic, calculations, and redox studies indicate a competence between photoinduced energy and electron transfer. Protonating the dimethylaminophenyl substituent through addition of an acidic medium led to a substantial increase in the fluorescence emission, triplet excited state formation, and singlet molecular oxygen production. At physiological pH, photosensitized inactivation of Staphylococcus aureus mediated by 1 μM BDP-C₆₀ exhibited a 4.5 log decrease of cell survival (>99.997 %) after 15 min irradiation. A similar result was obtained with Escherichia coli using 30 min irradiation. Moreover, proton-activated photodynamic action of BDP-C₆₀ turned this dyad into a highly effective photosensitizer to eradicate E. coli. Therefore, BDP-C₆₀ is an interesting photosensitizing structure in which the light-harvesting antenna effect of the BODIPY unit combined with the protonation of dimethylaminophenyl group can be used to improve the photoinactivation of bacteria.

Hydrangea-structured tumor microenvironment responsive degradable nanoplatform for hypoxic tumor multimodal imaging and therapy

Developing new strategies to alleviate tumor hypoxia and enhance the therapeutic efficacy towards solid tumors is of great significance to tumor therapy. Herein, to overcome tumor hypoxia, specifically designed aza-BODIPY photosensitizer is co-loaded with anti-cancer drug (doxorubicin, DOX) onto the hydrangea-structured MnO₂ nanoparticles, and a tumor microenvironment (TME) responsive degradable nanoplatform (MDSP NP) is established. MDSP NPs (∼54 nm), with near infrared absorption (∼853 nm), can be rapidly dissociated to generate oxygen in response to TME, whereby improving tumor hypoxia, in favor of effective drugs release and enhanced chemo/photodynamic therapy. Revealed by in vivo fluorescence and photoaccoustic imaging, MDSP NPs are preferential accumulated at tumor site. Confirmed by photothermal imaging, MDSP NPs can induce hyperthermia to relieve hypoxia, promote the uptake of therapeutic nanoparticles, and further reduce the resistance and improve the therapeutic efficiency. As a result, a remarkable synergistic tumor chemo/photodynamic/photothermal therapy with hydrangea-structured TME responsive oxygen-self-generation nanoplatform is confirmed by both in vitro and in vivo studies, testifying its great potential for hypoxic tumor treatment in clinical application.

Fullerene-based delivery systems

With the development of new drugs, there have been many attempts to explore innovative delivery routes. Targeted delivery systems are a desired solution designed to overcome the deficiency of routine methods. To transform this idea into reality, a wide range of nanoparticles has been proposed and studied. These nanoparticles should interact well with biological environments and pass through cell membranes to deliver therapeutic molecules. One of the pioneer classes of carbon-based nanoparticles for targeted delivery is the fullerenes. Fullerenes have a unique structure and possess suitable properties for interaction with the cellular environment. This short review concentrates on newly developed fullerene derivatives and their potential as advanced delivery systems for pharmaceutical applications.

Self-quenching synthesis of coordination polymer pre-drug nanoparticles for selective photodynamic therapy

A novel “pre-photodynamic” nanoparticles (Fe-IBDP NPs) with a tumor microenvironment (TME)-activatable PDT and good biodegradability were synthesized by self-quenching strategy.

A H₂O₂-Responsive Boron Dipyrromethene-Based Photosensitizer for Imaging-Guided Photodynamic Therapy

In this study, we demonstrate a novel H₂O₂ activatable photosensitizer (compound 7) which contains a diiodo distyryl boron dipyrromethene (BODIPY) core and an arylboronate group that quenches the excited state of the BODIPY dye by photoinduced electron transfer (PET). The BODIPY-based photosensitizer is highly soluble and remains nonaggregated in dimethyl sulfoxide (DMSO) as shown by the intense and sharp Q-band absorption (707 nm). As expected, compound 7 exhibits negligible fluorescence emission and singlet oxygen generation efficiency. However, upon interaction with H₂O₂, both the fluorescence emission and singlet oxygen production of the photosensitizer can be restored in phosphate buffered saline (PBS) solution and PBS buffer solution containing 20% DMSO as a result of the cleavage of the arylboronate group. Due to the higher concentration of H₂O₂ in cancer cells, compound 7 even with low concentration is particularly sensitive to human cervical carcinoma (HeLa) cells (IC50 = 0.95 μM) but hardly damage human embryonic lung fibroblast (HELF) cells. The results above suggest that this novel BODIPY derivative is a promising candidate for fluorescence imaging-guided photodynamic cancer therapy.

2-Pyridone-functionalized Aza-BODIPY photosensitizer for imaging-guided sustainable phototherapy

To overcome irradiation-dependence of cancer phototherapy, a near infrared aza-BODIPY-based photothermogenic photosensitizer BDY with 2-Pyridone group has been synthesized for imaging-guided photothermal synergistic sustainable photodynamic therapy. Multifunctional water-soluble BDY nanoparticles (NPs), with high photothermal conversion efficiency of 35.7% and excellent singlet oxygen (¹O₂) generation ability, are prepared by self-assembling. The reversible transformation between 2-pyridone moiety and its endoperoxide form endows BDY with continuous ¹O₂ generation ability under illumination and non-illumination conditions. Simultaneously, BDY NPs exhibit excellent tumor targeting properties by enhanced permeability and retention (EPR) effect and photoacoustic imaging (PAI) ability. Furthermore, the photothermal assisted sustainable photodynamic therapy can significantly inhibit tumor growth (93.4% inhibition) with almost no side effects by intermittent laser illumination. The finding highlights that this photothermal synergistic sustainable phototherapy presents great potential for clinical applications.