The self-assembly of a hybrid photosensitizer for the synergistically enhanced photodynamic/photothermal therapy

Near-infrared hemicyanine photosensitizer for targeted mitochondrial viscosity imaging and efficient photodynamic therapy

As a severe threat to human health, cancer has always been one of the most significant challenges facing the medical field. However, there is currently no effective technology or method to diagnose and treat cancer simultaneously. Therefore, developing a new approach that integrates diagnosis and treatment holds promise as a means of achieving personalized and precise cancer therapy. In this study, we developed a novel dual-functional near-infrared mitochondrial-targeted photosensitizer, Hcy-I, which is capable of simultaneously monitoring cellular viscosity and specifically targeting mitochondria for photodynamic therapy. Compared with traditional hemicyanine dyes, the introduction of iodine atoms in Hcy-I enhanced spin-orbit coupling (SOC) and promoted the intersystem crossing (ISC) rate, thereby increasing the efficiency of singlet oxygen (1O2) generation. In vitro experiments demonstrated that Hcy-I exhibited high sensitivity to viscosity variations and efficiently generated 1O2 under 638 nm laser irradiation, with an 1O2 quantum yield of up to 48.9 %. Cell experiments further revealed that this photosensitizer could effectively target mitochondria for photodynamic therapy, disrupting mitochondrial membrane potential and inducing cell death. When treated with Hcy-I at a concentration of 0.8 µM, the survival rate of HepG-2 cells was only 13 %. These results suggested that Hcy-I had the potential to integrate cancer diagnosis and treatment. The research not only promotes the development of photodynamic thereby technology, but also opens up new avenues for the diagnosis and treatment of cancer.

Lutein-Based pH and Photo Dual-Responsive Novel Liposomes Coated with Ce6 and PTX for Tumor Therapy

Liposomes are considered the best nanocarrier for delivering cancer drugs such as chlorin e6 (Ce6) and paclitaxel (PTX). However, the poor stability and non-selectivity release of liposomes may severely limit their further applications. In this study, based on the characteristics of lutein (L) photo-response and orthoester (OE) acid-response, stable and dual-responsive liposomes (Dr-lips) have been prepared. The Dr-lips exhibited a spherical shape with a uniform size of approximately 58.27 nm. Moreover, they displayed a zeta potential ranging from -45.45 to -28.25 mV and showed excellent storage stability, indicating stable colloidal properties. Additionally, they achieved high drug encapsulation rates, with 92.27% for PTX and 90.34% for Ce6, respectively. Meanwhile, under near-infrared (NIR) light at 660 nm, Ce6 plays a key role in accelerating the photodegradation rate of lutein and PEG-OE-L while also enhancing tissue penetration ability. Additionally, Dr-lips loaded with Ce6 and PTX not only displayed excellent pH and photo dual-responsiveness for targeted delivering and releasing but also showed remarkable reactive oxygen species (ROS) generation capacity and impressive anti-tumor activity in vitro. Therefore, it provides a novel strategy for optimizing stability and enhancing their targeted drug delivery of liposome.

PpIX/IR-820 Dual-Modal Therapeutic Agents for Enhanced PDT/PTT Synergistic Therapy in Cervical Cancer

High treatment accuracy is the key to efficient cancer treatment. Photodynamic therapy (PDT) and photothermal therapy (PTT) are two kinds of popular, precise treatment methods. The combination of photodynamic and photothermal therapy (PDT/PTT) can greatly enhance the precise therapeutic efficacy. In this work, protoporphyrin IX (PpIX) was selected as the PDT agent (photosensitizer), and new indocyanine green (IR-820) was selected as the PTT agent. Further, the two kinds of theranostic agents were encapsulated by biological-membrane-compatible liposomes to form PpIX-IR-820@Lipo nanoparticles (NPs), a new kind of PDT/PTT agent. The PpIX-IR-820@Lipo NPs exhibited good water solubility, a spherical shape, and high fluorescence peak emission in the near-infrared spectral region (700-900 nm, NIR). The cellular toxicity of PpIX-IR-820@Lipo NPs for human cervical cancer cells (HeLa) and human cervical epithelial cells (H8) was detected by the CCK-8 method, and low cytotoxicity was observed for the PpIX-IR-820@Lipo NPs. Then, the excellent cellular uptake of PpIX-IR-820@Lipo NPs was confirmed by laser scanning confocal microscopy. Moreover, the PDT/PTT property of PpIX-IR-820@Lipo NPs was illustrated via 2',7'-dichlorofluorescin diacetate (DCFH-DA) and annexin V-fluorescein isothiocyanate (annexin V-FITC), as indicator probes. The PDT/PTT synergistic efficiency of PpIX-IR-820@Lipo NPs on HeLa cells was verified, exhibiting a high efficiency of 70.5%. Thus, the novel theranostic PpIX-IR-820@Lipo NPs can be used as a promising PDT/PTT synergistic theranostic nanoplatform in future cervical cancer treatment.

Rational Modulation of BODIPY Photosensitizers to Design Metal-Organic Framework-Based NIR Nanocomposites for High-Efficiency Photodynamic Therapy in a Hypoxic Environment

Photodynamic therapy (PDT) is a promising noninvasive treatment that has drawn great attention. However, the hypoxic environment in tumors seriously limits the therapeutic effect of oxygen-dependent chemicals and PDT. Herein, a versatile nanocomposite DF-BODIPY@ZIF-8 with oxygen-generating ability was developed based on zeolitic imidazolate framework-8 (ZIF-8) by loading the near-infrared photosensitizer DF-BODIPY to overcome hypoxia-induced drug resistance in cancer therapy. ZIF-8 can catalyze the decomposition of hydrogen peroxide in tumors and increase the dissolved oxygen concentration, resulting in a significant improvement in PDT efficacy. Additionally, we found that enhancing the electronegativity of substituents can effectively reduce the energy level difference (ΔE_st) between the minimum singlet state (S₁) and the lowest triplet state (T₁), leading to the enhancement of the singlet oxygen quantum yield. In vitro experiments suggested that DF-BODIPY@ZIF-8 indeed had a higher singlet oxygen quantum yield and better tumor cell phototoxicity than free DF-BODIPY. In vivo experiments also demonstrated that DF-BODIPY@ZIF-8 could effectively eliminate 4T1 tumors under light irradiation. Thus, we conclude that increasing the electronegativity of substituents and introducing a ZIF-8 material can effectively improve the singlet oxygen quantum yield and overcome the hypoxia limitations for high-efficiency PDT.

The Use of the Thiol-Ene Addition Click Reaction in the Chemistry of Organosilicon Compounds: An Alternative or a Supplement to the Classical Hydrosilylation?

This review presents the main achievements in the use of the thiol-ene reaction in the chemistry of silicones. Works are considered, starting from monomers and ending with materials.The main advantages and disadvantages of this reaction are demonstrated using various examples. A critical analysis of the use of this reaction is made in comparison with the hydrosilylation reaction.

A Bacteria-Responsive Porphyrin for Adaptable Photodynamic/Photothermal Therapy

We report a cationic porphyrin 5,10,15,20-tetrakis-(4-N-methylpyridyl)-porphyrin (TMPyP) that can respond to specific bacteria, followed by adaptable photodynamic/photothermal therapy processes. TMPyP could be reduced to phlorin by facultative anaerobes with a strong reducing ability such as E. coli and S. typhimurium in hypoxic environments, possessing strong NIR absorption and remarkable photothermal conversion capacity, thus demonstrating excellent antimicrobial activity (>99 %) by photothermal therapy. While in an aerobic environment with aerobic bacteria, TMPyP functioned as a typical photosensitizer that killed bacteria effectively (>99.9 %) by photodynamic therapy. By forming a host-guest complex with cucurbit[7]uril, the biocompatibility of TMPyP significantly improved. This kind of bacteria-responsive porphyrin shows specificity and adaptivity in antimicrobial treatment and holds potential in non-invasive treatments of bacterial infections.

Nanomaterials-based photosensitizers and delivery systems for photodynamic cancer therapy

The increasing cancer morbidity and mortality requires the development of high-efficiency and low-toxicity anticancer approaches. In recent years, photodynamic therapy (PDT) has attracted much attention in cancer therapy due to its non-invasive features and low side effects. Photosensitizer (PS) is one of the key factors of PDT, and its successful delivery largely determines the outcome of PDT. Although a few PS molecules have been approved for clinical use, PDT is still limited by the low stability and poor tumor targeting capacity of PSs. Various nanomaterial systems have shown great potentials in improving PDT, such as metal nanoparticles, graphene-based nanomaterials, liposomes, ROS-sensitive nanocarriers and supramolecular nanomaterials. The small molecular PSs can be loaded in functional nanomaterials to enhance the PS stability and tumor targeted delivery, and some functionalized nanomaterials themselves can be directly used as PSs. Herein, we aim to provide a comprehensive understanding of PDT, and summarize the recent progress of nanomaterials-based PSs and delivery systems in anticancer PDT. In addition, the concerns of nanomaterials-based PDT including low tumor targeting capacity, limited light penetration, hypoxia and nonspecific protein corona formation are discussed. The possible solutions to these concerns are also discussed.

Graphene quantum dots-porphyrins/phthalocyanines multifunctional hybrid systems: from interfacial dialogue to applications

Engineered well-ordered hybrid nanomaterials are at a symbolically pivotal point, just ahead of a long-anticipated human race transformation. Incorporating newer carbon nanomaterials like graphene quantum dots (GQDs) with tetrapyrrolic porphyrins...

A heptamethine cyanine with meso-N-induced rearrangement for acid-activated tumour imaging and photothermal therapy

Photothermal therapy has been developed as one of the most attractive strategies for tumour therapy. However, most of the reported photothermal probes still suffer from poor selectivity or specificity for...

A carrier-free supramolecular nanoprodrug based on lactose-functionalized dimeric camptothecin via self-assembly in water for targeted and fluorescence imaging-guided chemo-photodynamic therapy

Most carrier-based nano drug delivery systems (nano-DDSs) are subjected to complex preparation or purification processes, metabolic instability and potential systemic toxicity. To overcome these issues, it is urgent to develop a multifunctional carrier-free nano-DDS that can be fabricated by a simple approach for enhanced anticancer efficacy. In this work, the carrier-free supramolecular nanoprodrug (CF SNPD) based on lactose (Lac) functionalized dimeric camptothecin (CPT) was developed, in which Lac and CPT were conjugated by the aromatized thioacetal (ATA, a reactive oxygen species (ROS)-responsive bond). The obtained Lac-ATA-CPT₂ prodrug and the photosensitizer Chlorin e6 (Ce6) formed CF SNPD (denoted as Ce6@Lac-ATA-CPT₂ NPs) in water by supramolecular self-assembly. The design of dimeric CPT endowed Ce6@Lac-ATA-CPT₂ NPs with ultrahigh drug-loading capacity (up to 94%) and excellent stability. The Lac-functionalized CF SNPD displayed active specific targetability to HepG2 cells resulting from the carbohydrate-protein interactions. Furthermore, the fluorescence signal of Ce6 facilitated the precise tracking and localization of Ce6@Lac-ATA-CPT₂ NPs within the cell. Meanwhile, the ROS generated by Ce6 not only cleaved ATA linker to trigger on-demand CPT release, but also exhibited a killing effect on tumor cells, enabling synergistic therapy via CPT-mediated chemotherapy (CT) and Ce6-induced photodynamic therapy (PDT). Therefore, the multifunctional CF SNPD may be one of the promising therapeutic options for liver cancer.

Cationic Phenosafranin Photosensitizers Based on Polyhedral Oligomeric Silsesquioxanes for Inactivation of Gram-Positive and Gram-Negative Bacteria

The high photodynamic effect of the Newman strain of the S. aureus and of clinical strains of S. aureus MRSA 12673 and E. coli 12519 are observed for new cationic light-activated phenosafranin polyhedral oligomeric silsesquioxane (POSS) conjugates in vitro. Killing of bacteria was achieved at low concentrations of silsesquioxanes (0.38 µM) after light irradiation (λ_{em. max} = 522 nm, 10.6 mW/cm²) for 5 min. Water-soluble POSS-photosensitizers are synthesized by chemically coupling a phenosafranin dye (PSF) (3,7-diamino-5-phenylphenazine chloride) to an inorganic silsesquioxane cage activated by attachment of succinic anhydride rings. The chemical structure of conjugates is confirmed by ¹H, ¹³C NMR, HRMS, IR, fluorescence spectroscopy and UV-VIS analyzes. The APDI and daunorubicin (DAU) synergy is investigated for POSSPSFDAU conjugates. Confocal microscopy experiments indicate a site of intracellular accumulation of the POSSPSF, whereas iBuPOSSPSF and POSSPSFDAU accumulate in the cell wall or cell membrane. Results from the TEM study show ruptured S. aureus cells with leaking cytosolic mass and distorted cells of E. coli. Bacterial cells are eradicated by ROS produced upon irradiation of the covalent conjugates that can kill the bacteria by destruction of cellular membranes, intracellular proteins and DNA through the oxidative damage of bacteria.

Multifunctional BODIPY for effective inactivation of Gram-positive bacteria and promotion of wound healing

Bacterial infectious diseases and antimicrobial resistance seriously endanger human health, so alternative therapies for bacterial infections are urgently needed. Recently, photodynamic therapy against bacteria has shown great potential because of its high efficiency and low acquired resistance. Here, we design and synthesize a dipyrromethene boron difluoride (BODIPY) photosensitizer containing a guanidine group LIBDP for combating bacterial infections. The positively charged guanidine can destroy the bacterial membrane and inhibit the proliferation of bacteria to a certain extent. Upon light irradiation, LIBDP can produce reactive oxygen species (ROS), which can destroy the pre-formed biofilm and induce potent antibacterial activity. In addition, the guanidine of LIBDP can be oxidized to nitric oxide (NO) by the generated ROS, which can not only improve the antibacterial effect, but also promote wound healing. The strategy in this work paves the way for synthesizing high-performance antibacterial materials.

Amphiphilic Diketopyrrolopyrrole Derivatives for Efficient Near-Infrared Fluorescence Imaging and Photothermal Therapy

The design and synthesis of single-molecule amphiphilic and multifunctional phototherapeutic agents are important to cancer diagnosis and therapy. In this work, we developed three amphiphilic diketopyrrolopyrrole derivatives (TPADPP, DTPADPP, and TPADDPP) with different donor-acceptor structures and poly(ethylene glycol) side chains. The corresponding nanoparticles (NPs) were obtained via a self-assembly from three amphiphilic DPP derivatives and used as smart phototherapeutic agents for tumor diagnosis and treatment. The three amphiphilic DPP NPs exhibited near-infrared (NIR) emissions and good biocompatibility. Thus, they could be used as fluorescence (FL) imaging agents for guided therapy. DTPADPP NPs and TPADDPP NPs also displayed excellent photothermal performance and high accumulation in the tumor. Owing to these beneficial features, the DTPADPP NPs and TPADDPP NPs synthesized herein are suitable for NIR FL imaging and effective photothermal therapy against the tumor in vivo.

Mild Open-Shell Character of BODIPY and Its Impact on Singlet and Triplet Excitation Energies

This study describes and rationalizes the electronic structure of BODIPY combining a large variety of quantum chemistry methods and computational tools. Examination of the obtained results using state-of-the-art electronic structure analyses provides a new and complete interpretation of the nature of low-lying electronic states in BODIPY and elucidates the limitations of excited-state methods in the computation of T₁ and S₁ energies, that is, systematic under- and overestimation of time-dependent density functional theory energies, respectively, and a large overestimation of the T₁/S₁ energy gap. Our analysis identifies the important role and physical origin of the mild open-shell character in the BODIPY ground state, that is, strong highest occupied and lowest unoccupied molecular orbital exchange interactions. The study provides guidelines for the accurate quantification of the T₁/S₁ gap, which is extremely relevant for the computational investigation of the photophysical properties of BODIPY and its derivatives. These conclusions should be taken into consideration in order to predict and interpret conspicuous photoactivated phenomena such as intersystem crossing, singlet fission, and triplet-triplet annihilation. Moreover, we believe that our study might provide new ideas and strategies for the analysis of other molecular chromophores.

FeSe2 nanosheets as a bifunctional platform for synergistic tumor therapy reinforced by NIR-II light

Multi-functionality has been a constant pursuit in the development of next-generation drug carriers, as it will bring the potential for combination therapy by integrating diverse therapeutic modes. In this work, FeSe₂ nanosheets (NSs) have been prepared as a bifunctional platform to investigate their use in synergistic cancer therapy. Bifunctional FeSe₂ NSs exhibit exceptional Fenton-like activity that generates cytotoxic hydroxyl radical (˙OH) and strong broad photothermal performance including the second-infrared (NIR-II) spectral range, wherein the ˙OH production can be enhanced by NIR-II light irradiation. Furthermore, doxorubicin (DOX) was conjugated onto NSs via a pH-responsive hydrazone bond to achieve preferential drug release in an acidic microenvironment. Upon intratumoral administration, these bifunctional drug-carrying FeSe₂ NSs showed an NIR-II irradiation-reinforced strong tumor suppression effect, and no obvious toxicity to normal tissues was observed. This study provides a new paradigm for the design of advanced drug carriers relying on their inherent physicochemical properties.

Functionalization of Photosensitized Silica Nanoparticles for Advanced Photodynamic Therapy of Cancer

BODIPY dyes have recently attracted attention as potential photosensitizers. In this work, commercial and novel photosensitizers (PSs) based on BODIPY chromophores (haloBODIPYs and orthogonal dimers strategically designed with intense bands in the blue, green or red region of the visible spectra and high singlet oxygen production) were covalently linked to mesoporous silica nanoparticles (MSNs) further functionalized with PEG and folic acid (FA). MSNs approximately 50 nm in size with different functional groups were synthesized to allow multiple alternatives of PS-PEG-FA decoration of their external surface. Different combinations varying the type of PS (commercial Rose Bengal, Thionine and Chlorine e6 or custom-made BODIPY-based), the linkage design, and the length of PEG are detailed. All the nanosystems were physicochemically characterized (morphology, diameter, size distribution and PS loaded amount) and photophysically studied (absorption capacity, fluorescence efficiency, and singlet oxygen production) in suspension. For the most promising PS-PEG-FA silica nanoplatforms, the biocompatibility in dark conditions and the phototoxicity under suitable irradiation wavelengths (blue, green, or red) at regulated light doses (10-15 J/cm2) were compared with PSs free in solution in HeLa cells in vitro.

NIR-triggered upconversion nanoparticles@thermo-sensitive liposome hybrid theranostic nanoplatform for controlled drug delivery

A novel hybrid photothermal theranostic nanoplatform UCNPs@Bi@SiO2@GE HP-lips is developed. Upon NIR irradiation, the nanoplatform could photothermally trigger controlled drug release and present bright upconversion luminescence.