Localized Photodynamic Therapy Using a Chlorin e6-Embedded Silicone-Covered Self-Expandable Metallic Stent as a Palliative Treatment for Malignant Esophageal Strictures

Localized photodynamic therapy (PDT) uses a polymeric-photosensitizer (PS)-embedded, covered self-expandable metallic stent (SEMS). PDT is minimally invasive and a noteworthy potential alternative for treating esophageal strictures, where surgery is not a viable option. However, preclinical evidence is insufficient, and optimized irradiation energy dose ranges for localized PDT are unclear. Herein, we validated the irradiation energy doses of the SEMS (embedded in a PS using chlorin e6 [Ce6] and covered in silicone) and PDT-induced tissue changes in a rat esophagus. Cytotoxicity and phototoxicity in the Ce6-embedded SEMS piece with laser irradiation were significantly higher than that of the silicone-covered SEMS with or without laser and the Ce6-embedded silicone-covered SEMS without laser groups (all p < 0.001). Moreover, surface morphology, atomic changes, and homogeneous coverage of the Ce6-embedded silicone-covered membrane were confirmed. The ablation range of the porcine liver was proportionally increased with the irradiation dose (all p < 0.001). The ablation region was identified at different irradiation energy doses of 50, 100, 200, and 400 J/cm2. The in vivo study in the rat esophagus comprised a control group and 100, 200, and 400 J/cm2 energy-dose groups. Finally, histology and immunohistochemistry (TUNEL and Ki67) confirmed that the optimized Ce6-embedded silicone-covered SEMS with selected irradiation energy doses (200 and 400 J/cm2) effectively damaged the esophageal tissue without ductal perforation. The polymeric PS-embedded silicone-covered SEMS can be easily placed via a minimally invasive approach and represents a promising new approach for the palliative treatment of malignant esophageal strictures.

Detection of Arsenic(V) by Fluorescence Sensing Based on Chlorin e6-Copper Ion

The high toxicity of arsenic (As) can cause irreversible harm to the environment and human health. In this study, the chlorin e6 (Ce6), which emits fluorescence in the infrared region, was introduced as the luminescence center, and the addition of copper ion (Cu2+) and As(V) provoked a regular change in fluorescence at 652 nm, whereas that of As(III) was 665 nm, which was used to optionally detect Cu2+, arsenic (As(III), and As(V)). The limit of detection (LOD) values were 0.212 μM, 0.089 ppm, and 1.375 ppb for Cu2+, As(III), and As(V), respectively. The developed method can be used to determine Cu2+ and arsenic in water and soil with good sensitivity and selectivity. The 1:1 stoichiometry of Ce6 with Cu2+ was obtained from the Job plot that was developed from UV-visible spectra. The binding constants for Cu2+ and As(V) were established to be 1.248 × 105 M-1 and 2.35 × 1012 M-2, respectively, using B-H (Benesi-Hildebrand) plots. Fluorescence lifetimes, B-H plots, FT-IR, and 1H-NMR were used to postulate the mechanism of Cu2+ fluorescence quenching and As(V) fluorescence restoration and the interactions of the two ions with the Ce6 molecule.

Novel Carrier-Free Nanodrug Enhances Photodynamic Effects by Blocking the Autophagy Pathway and Synergistically Triggers Immunogenic Cell Death for the Efficient Treatment of Breast Cancer

Photosensitizers have been widely used to cause intratumoral generation of reactive oxygen species (ROS) for cancer therapy, but they are easily disturbed by the autophagy pathway, a self-protective mechanism by mitigating oxidative damage. Hereby, we reported a simple and effective strategy to construct a carrier-free nanodrug, Ce6@CQ namely, based on the self-assembly of the photosensitizer chlorin e6 (Ce6) and the autophagy inhibitor chloroquine (CQ). Specifically, Ce6@CQ avoided the unexpected toxicity caused by the regular nanocarrier and also ameliorated its stability in different conditions. Light-activated Ce6 generated cytotoxic ROS and elicited part of the immunogenic cell death (ICD). Moreover, CQ induced autophagy dysfunction, which hindered self-healing in tumor cells and enhanced photodynamic therapy (PDT) to exert a more potent killing effect and more efficient ICD. Also, Ce6@CQ could effectively accumulate in the xenograft breast tumor site in a mouse model through the enhanced permeability and retention (EPR) effect, and the growth of breast tumors was effectively inhibited by Ce6@CQ with light. Such a carrier-free nanodrug provided a new strategy to improve the efficacy of PDT via the suppression of autophagy to digest ROS-induced toxic substances.

Targeted treatment of atherosclerosis with protein-polysaccharide nanoemulsion co-loaded with photosensitiser and upconversion nanoparticles

Macrophages are the most abundant cell group in atherosclerosis (AS) lesions and play a vital role in all stages of AS progression. Recent research has shown that reactive oxygen species (ROS) generation from photodynamic therapy (PDT) induces macrophage autophagy to improve abnormal lipid metabolism and inflammatory environment. Especially in macrophage-derived foam cells, which has become a potential strategy for the treatment of AS. In this study, we prepared the conjugate (DB) of dextran (DEX) and bovine serum albumin (BSA). The DB was used as the emulsifier to prepare nanoemulsion loaded with upconversion nanoparticles (UCNPs) and chlorin e6 (Ce6) (UCNPs-Ce6@DB). The DEX modified on the surface of the nanoemulsion can recognise and bind to the scavenger receptor class A (SR-A) highly expressed on macrophages and promote the uptake of macrophage-derived foam cells in AS plates through SR-A-mediated endocytosis. In addition, UCNPs-Ce6@DB-mediated PDT enhanced ROS generation and induced autophagy in macrophage-derived foam cells, enhanced the expression of ABCA1, a protein closely related to cholesterol efflux, and inhibited the secretion of pro-inflammatory cytokines. Ultimately, UCNPs-Ce6@DB was shown to inhibit plaque formation in mouse models of AS. In conclusion, UCNPs-Ce6@DB offers a promising treatment for AS.

Targeted and Oxygen-Enriched Nanoplatform for Enhanced Photodynamic Therapy: In Vitro 2D Cell and 3D Spheroid Model Evaluation

Hypoxic microenvironment and limited penetration of photosensitizers within solid tumors are two crucial factors that restrict photodynamic therapy (PDT) efficacy. Herein, a new fluorinated mixed micelle (M60@PFC-Ce6) is developed as a tumor-penetrating and oxygen-enriching nanoplatform, which consists of chlorin e6 (Ce6) and perfluorocarbons (PFCs) co-loaded into fluorinated micelles to relieve hypoxia conditions as well as folate as targeting ligand that facilitates the selective biodistribution within tumor solids. The incorporation of fluorinated copolymers into mixed micelles exhibits not only a great increase in the oxygen-loading capacity, but also improves the stability of liquid PFCs emulsion within micelles without leakage. M60@PFC-Ce6 shows excellent oxygen delivery capability, good intracellular reactive oxygen species (ROS) generation, and superior phototoxicity in vitro for both 2D monolayer of cells and 3D multicellular spheroid model. These results indicate the enriched oxygen delivery and increased cellular uptake resulting from folate-targeted ability to enhance ROS production and PDT efficacy. The penetration study of M60@PFC-Ce6 into a 3D spheroid confirms that small micellar size and folate-conjugation are beneficial for micelles to penetrate and accumulate within spheroids. Thus, a new nanoplatform with enriched oxygen-carrying amounts, better drug penetration, and stable micellar properties that relieve tumor hypoxia and improve PDT efficacy is provided.

Modular Nanotransporters Delivering Biologically Active Molecules to the Surface of Mitochondria

Treatment of various diseases, in particular cancer, usually requires the targeting of biologically active molecules at a selected subcellular compartment. We modified our previously developed modular nanotransporters (MNTs) for targeting mitochondria. The new MNTs are capable of binding to the protein predominantly localized on the outer mitochondrial membrane, Keap1. These MNTs possessing antiKeap1 monobody co-localize with mitochondria upon addition to the cells. They efficiently interact with Keap1 both in solution and within living cells. A conjugate of the MNT with a photosensitizer, chlorin e6, demonstrated significantly higher photocytotoxicity than chlorin e6 alone. We assume that MNTs of this kind can improve efficiency of therapeutic photosensitizers and radionuclides emitting short-range particles.

β-Cyclodextrin Nanophotosensitizers for Redox-Sensitive Delivery of Chlorin e6

The aim of this study is to prepare redox-sensitive nanophotosensitizers for the targeted delivery of chlorin e6 (Ce6) against cervical cancer. For this purpose, Ce6 was conjugated with β-cyclodextrin (bCD) via a disulfide bond, creating nanophotosensitizers that were fabricated for the redox-sensitive delivery of Ce6 against cancer cells. bCD was treated with succinic anhydride to synthesize succinylated bCD (bCDsu). After that, cystamine was attached to the carboxylic end of bCDsu (bCDsu-ss), and the amine end group of bCDsu-ss was conjugated with Ce6 (bCDsu-ss-Ce6). The chemical composition of bCDsu-ss-Ce6 was confirmed with 1H and 13C NMR spectra. bCDsu-ss-Ce6 nanophotosensitizers were fabricated by a dialysis procedure. They formed small particles with an average particle size of 152.0 ± 23.2 nm. The Ce6 release rate from the bCDsu-ss-Ce6 nanophotosensitizers was accelerated by the addition of glutathione (GSH), indicating that the bCDsu-ss-Ce6 nanophotosensitizers have a redox-sensitive photosensitizer delivery capacity. The bCDsu-ss-Ce6 nanophotosensitizers have a low intrinsic cytotoxicity against CCD986Sk human skin fibroblast cells as well as Ce6 alone. However, the bCDsu-ss-Ce6 nanophotosensitizers showed an improved Ce6 uptake ratio, higher reactive oxygen species (ROS) production, and phototoxicity compared to those of Ce6 alone. GSH addition resulted in a higher Ce6 uptake ratio, ROS generation, and phototoxicity than Ce6 alone, indicating that the bCDsu-ss-Ce6 nanophotosensitizers have a redox-sensitive biological activity in vitro against HeLa human cervical cancer cells. In a tumor xenograft model using HeLa cells, the bCDsu-ss-Ce6 nanophotosensitizers efficiently accumulated in the tumor rather than in normal organs. In other words, the fluorescence intensity in tumor tissues was significantly higher than that of other organs, while Ce6 alone did not specifically target tumor tissue. These results indicated a higher anticancer activity of bCDsu-ss-Ce6 nanophotosensitizers, as demonstrated by their efficient inhibition of the growth of tumors in an in vivo animal tumor xenograft study.

Vascular-targeted photodynamic therapy with glucose-conjugated chlorin e6 for dogs with spontaneously occurring tumours

BACKGROUND

Photodynamic therapy (PDT) using photosensitisers is a minimally invasive treatment for malignant tumours. However, ideal photosensitisers are not yet established. Recently, we developed a new photosensitiser, glucose-conjugated chlorin e6 (G-Ce6).

OBJECTIVES

To evaluate the clinical efficacy of vascular-targeted PDT (VTP), a type of PDT utilising a short drug-light interval, using G-Ce6 to treat spontaneously occurring tumours in dogs.

METHODS

Five dogs with spontaneously occurring tumours (malignant melanoma: three; haemangiopericytoma: two; and squamous cell carcinoma: one) were subjected to VTP. These dogs were intravenously injected with G-Ce6 at doses of 1-3 mg/kg 5 min before laser irradiation. Tumours were superficially or interstitially irradiated using a 677-nm diode laser.

RESULTS

Repeated VTP decreased tumour size, yielding complete remission in three dogs. Complications such as oedema surrounding normal tissues and fistulae were observed, and the oedema was self-limiting. The fistula was cured by debriding the necrotic tissues formed after VTP.

CONCLUSIONS

Our findings demonstrate that VTP using G-Ce6 had antitumour effects in dogs with spontaneously occurring tumours.

Chlorin E6-Curcumin-Mediated Photodynamic Therapy Promotes an Anti-Photoaging Effect in UVB-Irradiated Fibroblasts

Skin photoaging due to ultraviolet B (UVB) exposure generates reactive oxygen species (ROS) that increase matrix metalloproteinase (MMP). Chlorin e6-photodynamic therapy (Ce6-PDT), in addition to being the first-line treatment for malignancies, has been shown to lessen skin photoaging, while curcumin is well known for reducing the deleterious effects of ROS. In the current study, PDT with three novel Ce6-curcumin derivatives, a combination of Ce6 and curcumin with various linkers, including propane-1,3-diamine for Ce6-propane-curcumin; hexane-1,6-diamine for Ce6-hexane-curcumin; and 3,3'-((oxybis(ethane-2,1-diyl))bis(oxy))bis(propan-1-amine) for Ce6-dipolyethylene glycol (diPEG)-curcumin, were studied for regulation of UVB-induced photoaging on human skin fibroblast (Hs68) and mouse embryonic fibroblast (BALB/c 3T3) cells. We assessed the antiphotoaging effects of Ce6-curcumin derivatives on cell viability, antioxidant activity, the mechanism of matrix metalloproteinase-1 and 2 (MMP-2) expression, and collagen synthesis in UVB-irradiated in vitro models. All three Ce6-curcumin derivatives were found to be non-phototoxic in the neutral red uptake phototoxicity test. We found that Ce6-hexane-curcumin-PDT and Ce6-propane-curcumin-associated PDT exhibited less cytotoxicity in Hs68 and BALB/c 3T3 fibroblast cell lines compared to Ce6-diPEG-curcumin-PDT. Ce6-diPEG-curcumin and Ce6-propane-curcumin-associated PDT showed superior antioxidant activity in Hs68 cell lines. Further, in UVB-irradiated in vitro models, the Ce6-diPEG-curcumin-PDT greatly attenuated the expression levels of MMP-1 and MMP-2 by blocking mitogen-activated protein kinases (MAPKs), activator protein 1 (AP-1), and tumor necrosis factor-α (NF-κB) signaling. Moreover, Ce6-diPEG-curcumin effectively inhibited inflammatory molecules, such as cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) expression, while accelerating collagen synthesis. These results demonstrate that Ce6-diPEG-curcumin may be a potential therapy for treating skin photoaging.

Biosynthetic Melanin/Ce6-Based Photothermal and Sonodynamic Therapies Significantly Improved the Anti-Tumor Efficacy

Photothermal therapy (PTT) and sonodynamic therapy (SDT) are becoming promising therapeutic modalities against various tumors in recent years. However, the single therapeutic modality with SDT or PTT makes it difficult to achieve a satisfactory anti-tumor outcome due to their own inherent limitations, such as poor tissue penetration for the near-infrared (NIR) laser and the limited cytotoxic reactive oxygen species (ROS) generated from conventional sonosensitizers irradiated by ultrasound (US). Here, we successfully biosynthesized melanin with a controllable particle size with genetically engineered bacteria harboring a heat-inducible gene circuit. The biosynthetic melanin with 8 nm size and chlorin e6 (Ce6) was further encapsulated into liposomes and obtained SDT/PTT dual-functional liposomes (designated as MC@Lip). The resulting MC@Lip had an approximately 100 nm particle size, with 74.71% ± 0.54% of encapsulation efficiency for melanin and 94.52% ± 0.78% for Ce6. MC@Lip exhibited efficient 1O2 production and photothermal conversion capability upon receiving irradiation by US and NIR laser, producing significantly enhanced anti-tumor efficacy in vitro and in vivo. Especially, US and NIR laser irradiation of tumors received with MC@Lip lead to complete tumor regression in all tested tumor-bearing mice, indicating the great advantage of the combined use of SDT and PTT. More importantly, MC@Lip possessed good photoacoustic (PA) and fluorescence dual-modal imaging performance, making it possible to treat tumors under imaging guidance. Our study provides a novel approach to synthesize a melanin nanoparticle with controllable size and develops a promising combined SDT/PTT strategy to treat tumors.

Anti-Obesity Effect of Chlorin e6-Mediated Photodynamic Therapy on Mice with High-Fat-Diet-Induced Obesity

This study aimed to evaluate the efficacy of Chlorin e6 (Ce6)-based photodynamic therapy (PDT) for anti-obesity activities in high-fat-diet (HFD)-induced obesity mouse models. We induced obesity in C57BL/6 mice by HFD and administered Ce6 (2.5 or 5 mg/kg) orally with 3 h of incubation. The mice were then exposed to light of high fluence rate (4.96 mW/cm²) or low fluence rate (2.56 mW/cm²) in the designed LED mouse chamber 2-3 days a week for up to 8 weeks. The study also analyzed the pharmacokinetics and optimization of the drug by evaluating the absorption, distribution, metabolism, and excretion (ADME) of Ce6 in the rat models. Both low doses (2.5 mg/kg) and high doses (5 mg/kg) of Ce6 with high irradiation dose showed better anti-obesity effects than other groups with decreased body weight. The lipid accumulation in the liver and adipocyte size in epididymal adipose tissues were found to be decreased by Ce6-PDT in comparison to vehicle-treated HFD groups. We also observed increased levels of the lipidomic biomarkers, such as leptin and LDL cholesterol, while observing decreasing levels of total cholesterol and adiponectin in the Ce6-PDT-treated mice. These findings may provide valuable insight into Ce6-PDT as an alternative and non-invasive therapeutic methodology for obesity and obesity-related diseases.

Novel Chlorin e6-Curcumin Derivatives as a Potential Photosensitizer: Synthesis, Characterization, and Anticancer Activity

Novel series of chlorin e6-curcumin derivatives were designed and synthesized. All the synthesized compounds 16, 17, 18, and 19 were tested for their photodynamic treatment (PDT) efficacy against human pancreatic cancer cell lines: AsPC-1, MIA-PaCa-2, and PANC-1. The cellular uptake study was performed in the aforementioned cell lines using fluorescence-activated cell sorting (FACS). 17, among the synthesized compounds with IC₅₀ values of 0.27, 0.42, and 0.21 µM against AsPC-1, MIA PaCa-2, and PANC-1 cell lines, respectively, demonstrated excellent cellular internalization capability and exhibited higher phototoxicity relative to the parent Ce6. The quantitative analyses using Annexin V-PI staining revealed that the 17-PDT-induced apoptosis was dose-dependent. In pancreatic cell lines, 17 reduced the expression of the anti-apoptotic protein, Bcl-2, and increased the pro-apoptotic protein, cytochrome C, which indicates the activation of intrinsic apoptosis, the primary cause of cancer cell death. Structure-activity relationship studies have shown that the incorporation of additional methyl ester moiety and conjugation to the enone moiety of curcumin enhances cellular uptake and PDT efficacy. Moreover, in vivo PDT testing in melanoma mouse models revealed that 17-PDT greatly reduced tumor growth. Therefore, 17 might be an effective photosensitizer for PDT anticancer therapy.

Photodynamic therapy in a patient with perianal extramammary Paget's disease

Extramammary Paget's disease is a rare neoplasm of apocrine gland-bearing areas of the skin. One of the most common localizations of such a tumor is the perianal area. Surgery is the most frequently reported therapy. However, it is invasive and complicated by a high recurrence rate. An alternative to surgical treatment may be non-invasive photodynamic therapy. We describe in this article the case of a 69-year-old patient with extramammary Paget's disease (a large tumor in the perianal area 22 × 18 cm) successfully treated with chlorin e6 photodynamic therapy.

Near-infrared phototheranostics of tumors with protoporphyrin IX and chlorin e6 photosensitizers

BACKGROUND

The study aims to develop a method for phototheranostics of tumors in the near-infrared (NIR) range using protoporphyrin IX (PpIX) and chlorin e6 (Ce6) photosensitizers (PSs) MATERIALS AND METHODS: Phototheranostics includes spectral fluorescence diagnostics of PS distribution and photodynamic therapy (PDT) using a single laser in the red spectral range. PpIX and Ce6 fluorescence were registered in the NIR range. PpIX and Ce6 photobleaching was determined during PDT by the change in PS fluorescence. NIR phototheranostics with PpIX and Ce6 were performed on optical phantoms and tumors of patients with oral leukoplakia and basal cell carcinoma.

RESULTS

NIR spectral fluorescence diagnostics of optical phantoms with PpIX or Ce6 is possible when fluorescence is excited by 635 or 660 nm lasers. Fluorescence intensity of PpIX and Ce6 was measured in the range of 725-780 nm. The highest values of signal-to-noise in the case of phantoms with PpIX were observed at λ_exc=635 nm, and for phantoms with Ce6 at λ_exc=660 nm. NIR phototheranostics provides the detection of tumor tissues with PpIX or Ce6 accumulation. The PSs photobleaching in the tumor during PDT occurs according to a bi-exponential law.

CONCLUSION

Phototheranostics of tumors containing PpIX or Ce6 allows fluorescent monitoring of PS distribution in the NIR range and measuring PSs photobleaching during light exposure that provides personalization of the photodynamic exposure duration to deeper tumors. Using a single laser for fluorescence diagnostics and PDT reduces patient treatment time.

Dissecting the Interactions between Chlorin e6 and Human Serum Albumin

Chlorin e6 (Ce6) is among the most used sensitizers in photodynamic (PDT) and sonodynamic (SDT) therapy; its low solubility in water, however, hampers its clinical exploitation. Ce6 has a strong tendency to aggregate in physiological environments, reducing its performance as a photo/sono-sensitizer, as well as yielding poor pharmacokinetic and pharmacodynamic properties. The interaction of Ce6 with human serum albumin (HSA) (i) governs its biodistribution and (ii) can be used to improve its water solubility by encapsulation. Here, using ensemble docking and microsecond molecular dynamics simulations, we identified the two Ce6 binding pockets in HSA, i.e., the Sudlow I site and the heme binding pocket, providing an atomistic description of the binding. Comparing the photophysical and photosensitizing properties of Ce6@HSA with respect to the same properties regarding the free Ce6, it was observed that (i) a red-shift occurred in both the absorption and emission spectra, (ii) a maintaining of the fluorescence quantum yield and an increase of the excited state lifetime was detected, and (iii) a switch from the type II to the type I mechanism in a reactive oxygen species (ROS) production, upon irradiation, took place.

Heat Shock Protein Inhibitors Show Synergistic Antibacterial Effects with Photodynamic Therapy on Caries-Related Streptococci In Vitro and In Vivo

Caries are chronic infections in which the cariogenic biofilm plays a critical role in disease occurrence and progression. Photodynamic therapy (PDT) is a new effective treatment that is receiving wide attention in the antibacterial field, but it can lead to the upregulation of heat shock proteins (HSPs), which enhances bacterial resistance. Herein, we incorporated HSP inhibitors with PDT to evaluate the effect on Streptococcus mutans, Streptococcus sobrinus, and Streptococcus sanguinis under planktonic conditions and on cariogenic biofilms. Additionally, a model of caries was established in 2-week-old rats, and anticaries properties were evaluated by Keyes' scoring. Importantly, the combination of HSP inhibitors and PDT had outstanding efficiency in inhibiting the growth of tested Streptococcus strains and the formation of either monomicrobial or multispecies biofilms in vitro. In addition, the quantity of colonized streptococci and the severity of carious lesions were also distinctly suppressed in vivo. Overall, the synergistic application of HSP inhibitors and PDT has promising potential in the prevention and treatment of dental caries. IMPORTANCE Effective therapies for the prevention and control of caries are urgently needed. Cariogenic streptococci play a key role in the occurrence and progression of caries. Recently, photodynamic therapy has been demonstrated to have good antibacterial efficiency, but it can cause a heat shock response in bacteria, which may weaken its practical effects. We indicate here an effective therapeutic strategy of combining heat shock protein inhibitors and photodynamic therapy, which shows excellent inhibition toward three dominant streptococci related to caries and suppression of carious progression in a rat model. Further development for clinical application is promising.

Chlorin e6: A Promising Photosensitizer in Photo-Based Cancer Nanomedicine

Conventional cancer treatment modalities are often associated with major therapeutic limitations and severe side effects. Photodynamic therapy is a localized noninvasive mode of treatment that has given a different direction to cancer research due to its effectivity against a wide range of cancers and minimal side effects. A photosensitizer is the key component of photodynamic therapy (PDT) that generates cytotoxic reactive oxygen species to eradicate cancer cells. As the therapeutic effectivity of PDT greatly depends upon the photosensitizer, great efforts have been made to search for an ideal photosensitizer. Chlorin e6 is a FDA approved second generation photosensitizer that meets the desired clinical properties for PDT. It is known for its high reactive oxygen species (ROS) generation ability and anticancer potency against many types of cancer. Hydrophobicity is a major drawback of Ce6 that leads to its poor biodistribution and rapid clearance from the circulatory system. To overcome this drawback, researchers have designed and fabricated several types of nanosystems, which can enhance Ce6 solubility and thereby enhance its bioavailability. These nanosystems also improve tumor accumulation of Ce6 by selectively targeting the cancer cells through passive and active targeting. In addition, Ce6 has been employed in many combination therapies like chemo-photodynamic therapy, photoimmunotherapy, and combined photodynamic-photothermal therapy. A combination therapy is more curative than a single therapy due to the synergistic effects of individual therapies. Ce6-based nanosystems for combination therapies have shown excellent results in various studies and provide a promising platform for cancer treatment.

Nanoparticles of N-Vinylpyrrolidone Amphiphilic Copolymers and Pheophorbide a as Promising Photosensitizers for Photodynamic Therapy: Design, Properties and In Vitro Phototoxic Activity

A series of nanoparticles (NPs) with a hydrodynamic radius from 20 to 100 nm in PBS was developed over the solubilization of hydrophobic dye methyl pheophorbide a (chlorin e₆ derivative) by amphiphilic copolymers of N-vinylpyrrolidone with (di)methacrylates. Photophysical properties and biological activity of the NPs aqueous solution were studied. It was found that the dye encapsulated in the copolymers is in an aggregated state. However, its aggregation degree decreases sharply, and singlet oxygen quantum yield and the fluorescence signal increase upon the interaction of these NPs with model biological membranes-liposomes or components of a tissue homogenate. The phototoxic effect of NPs in HeLa cells exceeds by 1.5-2 times that of the reference dye chlorin e₆ trisodium salt-one of the most effective photosensitizers used in clinical practice. It could be explained by the effective release of the hydrophobic photosensitizer from the NPs into biological structures. The demonstrated approach can be used not only for the encapsulation of hydrophobic photosensitizers for PDT but also for other drugs, and N-vinylpyrrolidone amphiphilic copolymers show promising potential as a modern platform for the design of targeted delivery vehicles.

[Intraoperative photodynamic therapy in complex treatment of malignant gliomas]

Treatment of malignant gliomas is an extremely difficult objective associated with difficult choice of correct strategy. Photodynamic therapy is still not the treatment standard in these patients although this approach significantly improves treatment outcomes in surgery of gliomas.

OBJECTIVE

To demonstrate the possibilities of chlorin e6-mediated photodynamic therapy for malignant glial tumors.

MATERIAL AND METHODS

There were 161 patients with malignant supratentorial glial tumors who were treated at the Polenov Russian Neurosurgery Institute between 2009 and 2016. Eighty patients comprised the main group (photodynamic therapy), 81 ones - control group (without photodynamic therapy).

RESULTS

Photodynamic therapy in complex treatment of malignant brain gliomas significantly increases overall survival in patients with Grade III gliomas up to 39.1±5.5 months (control group - 22.8±3.3 months) and Grade IV gliomas up to 20.7±4.7 months (control group - 13.5±2.3 months) (p=0.0002). This method also increases relapse-free period in patients with Grade III gliomas up to 21.7±3.4 months (control group - 15.8±3.1 months) (p=0.0002) and Grade IV gliomas up to 11.1±2.1 months (control group - 8.0±2.3 months) (p=0.0001).

[Comparison of three commercial photosensitizers for efficiency of inducing immunogenic cell death in anti-tumor immunotherapy]

OBJECTIVE

To compare 3 commercial immunogenic cell death (ICD) inducers, namely Chlorin e6 (Ce6), Neutral Red (NR), and Rose Bengal Sodium salt (RB), for their photosensitive properties, efficacy for photodynamic therapy (PDT) and ICD induction efficiency in antitumor immunotherapy.

METHODS

Reactive oxygen species (ROS) probes were used to evaluate the photosensitivity of the 3 ICD inducers, and their capacity for inducing intracellular ROS production was evaluated using a DCFH-DA probe. The cytotoxicity and biocompatibility of the 3 photosensitizers were compared using a CCK-8 kit, and their ICD-inducing efficiency was assessed by detecting the levels of surface-exposed calreticulin (ecto-CRT), high mobility group protein 1 (HMGB1) and adenosine triphosphate (ATP). In the animal experiment, BALB/c mouse models bearing 4T1 cellderived subcutaneous tumor were given intratumoral injection of Ce6 or NR solution (30 μL, 5 mg/mL), followed 2 h later by white light irradiation for 10 min (400 mW/cm²). Body weight and tumor size changes of the mice were monitored, and the percentage of CD8⁺ T cells in the tumor and IFN-γ⁺ CD8⁺ T cells in the spleen were analyzed by flow cytometry 14 days after the treatment. HE and TUNEL staining was used to analyze tumor cell apoptosis in the mice.

RESULTS

Among the 3 photosensitizers, Ce6 exhibited the strongest ROS-inducing capability and killing effect on the tumor cells. The results of ectoCRT, HMGB1 and ATP level detection all demonstrated a stronger ICD induction ability of Ce6. In the tumor-bearing mice, the tumor growth in Ce6 and NR groups was significantly inhibited after the treatment. The percentages of CD8⁺ T cells and IFN-γ⁺ CD8⁺ T cells were 12.7% and 7.1% in Ce6 group, respectively, significantly higher than those in NR group (6.1% and 2.8%, respectively; P < 0.05). HE and TUNEL staining revealed obvious tumor cell apoptosis in the tumor tissues in both Ce6 and NR groups, but the therapeutic effect was more prominent in Ce6 group.

CONCLUSION

Among the 3 photosensitizers, Ce6 has the highest efficiency for inducing ROS production with the strongest PDT efficacy and ICD induction capability. Ce6 can also increase the number and function of CD8⁺ T cells in anti-tumor immunotherapy to initiate robust adaptive immune response.

MMP-2 Inhibitor-Mediated Tumor Microenvironment Regulation Using a Sequentially Released Bio-Nanosystem for Enhanced Cancer Photo-Immunotherapy

Combining photodynamic therapy (PDT) with natural killer (NK) cell-based immunotherapy has shown great potential against cancers, but the shedding of NK group 2, member D ligands (NKG2DLs) on tumor cells inhibited NK cell activation in the tumor microenvironment. Herein, we assembled microenvironment-/light-responsive bio-nanosystems (MLRNs) consisting of SB-3CT-containing β-cyclodextrins (β-CDs) and photosensitizer-loaded liposomes, in which SB-3CT was considered to remodel the tumor microenvironment. β-CDs and liposomes were linked by metalloproteinase 2 (MMP-2) responsive peptides, enabling sequential release of SB-3CT and chlorin e6 triggered by the MMP-2-abundant tumor microenvironment and 660 nm laser irradiation, respectively. Released SB-3CT blocked tumor immune escape by antagonizing MMP-2 and promoting the NKG2D/NKG2DL pathway, while liposomes were taken up by tumor cells for PDT. MLRN-mediated photo-immunotherapy significantly induced melanoma cell cytotoxicity (83.31%), inhibited tumor growth (relative tumor proliferation rate: 1.13% of that of normal saline) in the xenografted tumor model, and enhanced tumor-infiltrating NK cell (148 times) and NKG2DL expression (9.55 and 16.52 times for MICA and ULBP-1, respectively), achieving a synergistic effect. This study not only provided a simple insight into the development of new nanomedicine for programed release of antitumor drugs and better integration of PDT and immunotherapy but also a novel modality for clinical NK cell-mediated immunotherapy against melanoma.

Combined Photothermal and Photodynamic Therapy for Cancer Treatment Using a Multifunctional Graphene Oxide

Graphene oxide (GO) is one of the most studied nanomaterials in many fields, including the biomedical field. Most of the nanomaterials developed for drug delivery and phototherapies are based on noncovalent approaches that lead to an unspecific release of physisorbed molecules in complex biological environments. Therefore, preparing covalently functionalized GO using straightforward and versatile methods is highly valuable. Phototherapies, including photothermal therapy (PTT) and photodynamic therapy (PDT), have shown great potential as effective therapeutic approaches against cancer. To overcome the limits of a single method, the combination of PTT and PDT can lead to a combined effect with a higher therapeutic efficiency. In this work, we prepare a folic acid (FA) and chlorin e6 (Ce6) double-functionalized GO for combined targeted PTT/PDT. This conjugate can penetrate rapidly into cancer cells and macrophages. A combined effect of PTT and PDT is observed, leading to a higher killing efficiency toward different types of cells involved in cancer and other diseases. Our work provides a simple protocol to prepare multifunctional platforms for the treatment of various diseases.

Preliminary low-dose photodynamic exposure to the skin cancer with chlorin e6 photosensitizer

BACKGROUND

The study was aimed to investigate the chlorin e6 photosensitizer distribution in the tumor and tumor border (5 mm) during low-dose photodynamic treatment and to increase the effectiveness of the therapy for skin neoplasms.

METHODS

Sensitized boundaries of neoplasms were evaluated by video fluorescence imaging. The study of changes in the chlorin e6 distribution before/after photodynamic therapy and in the process of low-dose photodynamic exposure was carried out by the method of spectral fluorescence diagnostics.

RESULTS

All 19 patients with basal-cell skin cancer had a contrast of chlorin e6 accumulation compared to normal tissues. 3 hours after intravenous administration of the photosensitizer at a dose of 1 mg/kg, the chlorin e6 concentration was: in normal tissues - 0.18 mg/kg, in the tumor - 1.26 mg/kg, in the tumor border - 0.63 mg/kg. In most cases, the fluorescence indices of chlorin e6 in tumor tissues after low-dose photodynamic therapy increased and exceeded the values before light exposure.

CONCLUSION

Low-dose photodynamic therapy seems to be the optimal method for treating neoplasms, which does not cause severe pain in patients during the light exposure and allows locally increasing of the photosensitizer concentration in tumor tissues. This method of photodynamic therapy can improve the effectiveness of thе treatment.

CD44 Receptor-Mediated/Reactive Oxygen Species-Sensitive Delivery of Nanophotosensitizers against Cervical Cancer Cells

Stimulus-sensitive, nanomedicine-based photosensitizer delivery has an opportunity to target tumor tissues since oxidative stress and the expression of molecular proteins, such as CD44 receptors, are elevated in the tumor microenvironment. The aim of this study is to investigate the CD44 receptor- and reactive oxygen species (ROS)-sensitive delivery of nanophotosensitizers of chlorin e6 (Ce6)-conjugated hyaluronic acid (HA) against HeLa human cervical cancer cells. For the synthesis of nanophotosensitizers, thioketal diamine was conjugated with the carboxyl group in HA and then the amine end group of HA-thioketal amine conjugates was conjugated again with Ce6 (Abbreviated as HAthCe6). The HAthCe6 nanophotosensitizers were of small diameter, with sizes less than 200. Their morphology was round-shaped in the observations using a transmission electron microscope (TEM). The HAthCe6 nanophotosensitizers responded to oxidative stress-induced changes in size distribution when H₂O₂ was added to the nanophotosensitizer aqueous solution, i.e., their monomodal distribution pattern at 0 mM H₂O₂ was changed to dual- and/or multi-modal distribution patterns at higher concentrations of H₂O₂. Furthermore, the oxidative stress induced by the H₂O₂ addition contributed to the disintegration of HAthCe6 nanophotosensitizers in morphology, and this phenomenon accelerated the release rate of Ce6 from nanophotosensitizers. In a cell culture study using HeLa cells, nanophotosensitizers increased Ce6 uptake ratio, ROS generation and PDT efficacy compared to free Ce6. Since HA specifically bonds with the CD44 receptor of cancer cells, the pretreatment of free HA against HeLa cells decreased the Ce6 uptake ratio, ROS generation and PDT efficacy of HAthCe6 nanophotosensitizers. These results indicated that intracellular delivery of HAthCe6 nanophotosensitizers can be controlled by the CD44 receptor-mediated pathway. Furthermore, these phenomena induced CD44 receptor-controllable ROS generation and PDT efficacy by HAthCe6 nanophotosensitizers. During in vivo tumor imaging using HeLa cells, nanophotosensitizer administration showed that the fluorescence intensity of tumor tissues was relatively higher than that of other organs. When free HA was pretreated, the fluorescence intensity of tumor tissue was relatively lower than those of other organs, indicating that HAthCe6 nanophotosensitizers have CD44 receptor sensitivity and that they can be delivered by receptor-specific manner. We suggest that HAthCe6 nanophotosensitizers are promising candidates for PDT in cervical cancer.

Glutathione-sensitive IPI-549 nanoparticles synergized with photodynamic Chlorin e6 for the treatment of breast cancer

We combined phosphoinositol-3-kinin inhibitor IPI-549 and photodynamic Chlorin e6 (Ce6) on carboxymethyl chitosan to develop a novel drug delivery nanoparticle (NP) system (Ce6/CMCS-DSP-IPI549) and evaluate its glutathione (GSH) sensitivity and targeting ability for breast cancer treatment. The NPs were spherical with a uniform size of 218.8 nm, a stable structure over 7 days. The maximum encapsulation efficiency was 64.42%, and NPs drug loading was 8.05%. The NPs released drugs within tumor cells due to their high GSH concentration, while they maintained structural integrity in normal cells, which have low GSH concentration. The cumulative release rates of IPI-549 and Ce6 at 108 h were 70.67% and 40.35% (at GSH 10 mM) and 8.11% and 2.71% (at GSH 2μM), respectively. The NPs showed a strong inhibitory effect on 4T1 cells yet did not affect human umbilical vein endothelial cells (HUVECs). After irradiation by a 660 nm infrared laser for 72 h, the survival rate of 4T1 cells was 15.51%. Cellular uptake studies indicated that the NPs could accurately release drugs into tumor cells. In addition, the NPs had a good photodynamic effect and promoted the release of reactive oxygen species to damage tumor cells. Overall, the combination therapy of IPI-549 and Ce6 is safe and effective, and may provide a new avenue for the treatment of breast cancer.

Reactive Oxygen Species-Sensitive Nanophotosensitizers of Methoxy Poly(ethylene glycol)-Chlorin e6/Phenyl Boronic Acid Pinacol Ester Conjugates Having Diselenide Linkages for Photodynamic Therapy of Cervical Cancer Cells

The aim of this study is to fabricate nanophotosensitizers composed of methoxy poly(ethylene glycol) (mPEG), chlorin e6 (Ce6), and phenylboronic acid pinacol ester (PBAP) with diselenide linkages for reactive oxygen species (ROS)-sensitive photodynamic therapy (PDT) of cervical cancer cells. To fabricate nanophotosensitizers, Ce6 was conjugated with mPEG via selenocystamine linkage and then remaining carboxylic acid groups of Ce6 was attached to PBAP (mPEGseseCe6PBAP conjugates). Nanophotosensitizers of mPEGseseCe6PBAP conjugates were prepared by dialysis method. In transmission electron microscope (TEM) observation, nanophotosensitizers of mPEGseseCe6PBAP conjugates have spherical shapes and their diameters were less than 150 nm. The average diameter of mPEGseseCe6PBAP nanophotosensitizers was 92.7 ± 9.6 nm in particle size analysis. When H₂O₂ was added to the nanophotosensitizer solution, nanophotosensitizers were sensitively disintegrated according to the H₂O₂ concentration and then changed from monomodal distribution to multimodal distribution in particle size distribution. Furthermore, Ce6 release from nanophotosensitizers also increased according to the H₂O₂ concentration. When H₂O₂ was added to cell culture of HeLa human cervical cancer cells, intracellular Ce6 uptake of nanophotosensitizers were gradually increased according to the H₂O₂ concentration, indicating that nanophotosensitizers showed ROS-sensitive delivery of Ce6 against cancer cells.As well as free Ce6, nanophotosensitizers in the absence of light irradiation have low intrinsic cytotoxicity against RAW264.7 cells and HeLa cells. However, nanophotosensitizers induced cell death dose-dependently under light irradiation. Especially, nanophotosensitizers showed significantly higher ROS generation and phototoxicity against HeLa cells in vitro. When nanophotosensitizers were intravenously administered to animal tumor xenograft model of HeLa cells, tumor tissues revealed stronger fluorescence intensity than other tissues by light irradiation while absence of light irradiation induced relatively lower fluorescence intensity in tumor tissues, indicating that nanophotosensitizers have sensitivity against oxidative stress in tumor tissues. We suggest that nanophotosensitizers of mPEGseseCe6PBAP conjugates are promising vehicle for PDT of cervical cancer cells.

Chlorin e6-Biotin Conjugates for Tumor-Targeting Photodynamic Therapy

To improve the tumor-targeting efficacy of photodynamic therapy, biotin was conjugated with chlorin e6 to develop a new tumor-targeting photosensitizer, Ce6-biotin. The Ce6-biotin had good water solubility and low aggregation. The singlet-oxygen generation rate of Ce6-biotin was slightly increased compared to Ce6. Flow cytometry and confocal laser scanning microscopy results confirmed Ce6-biotin had higher binding affinity toward biotin-receptor-positive HeLa human cervical carcinoma cells than its precursor, Ce6. Due to the BR-targeting ability of Ce6-biotin, it exhibited stronger cytotoxicity to HeLa cells upon laser irradiation. The IC50 against HeLa cells of Ce6-biotin and Ce6 were 1.28 µM and 2.31 µM, respectively. Furthermore, both Ce6-biotin and Ce6 showed minimal dark toxicity. The selectively enhanced therapeutic efficacy and low dark toxicity suggest that Ce6-biotin is a promising PS for BR-positive-tumor-targeting photodynamic therapy.

The Enhancement of the Photodynamic Therapy and Ciprofloxacin Activity against Uropathogenic Escherichia coli Strains by Polypodium vulgare Rhizome Aqueous Extract

Antibiotic therapy and photodynamic therapy (PDT) are commonly used to treat bacterial infections. Unfortunately, these methods are often ineffective. Therefore, agents that could effectively support antibiotic therapy and PDT in the inactivation of pathogens are being sought. Phytotherapy seems to be a good solution. The aim of the current research was to examine whether Polypodium vulgare extract (PvE) would improve the effectiveness of PDT and ciprofloxacin (CIP), an antibiotic that is commonly used to treat urinary tract infections in humans. UHPLC-MS analysis was performed to establish the PvE content. Chlorin e6 has been used as a photosensitizer in the PDT method. Biofilm production was established using the spectrophotometric method. The live cell count in planktonic and biofilm consortia was determined with the microdilution method and DAPI staining. The decrease of the bacterial survival, biofilm mass synthesis, and morphological changes of the bacteria under the combined treatments: PDT+PvE and CIP+PvE was noted. The results clearly indicate that the PvE can be used as a good agent for improving the efficacy of both PDT and the CIP activity to inactivate uropathogenic Escherichia coli strains. The obtained results are of particular value in the era of widespread and still-increasing drug resistance among bacterial pathogens.

Biocompatible Mesoporous Silica-Polydopamine Nanocomplexes as MR/Fluorescence Imaging Agent for Light-Activated Photothermal-Photodynamic Cancer Therapy In Vivo

Conventional cancer phototherapy with single modality suffers from low therapeutic efficacy and undesired posttreatment damage for adjacent normal tissues. Therefore, the lower NIR laser irradiation power is vital to the reduction or preclusion of risk of scalds and burns in normal tissues. Herein, we rationally proposed a novel multifunctional nanocomplex, which enabled good magnetic resonance (MR) imaging contrast effect and promising photothermal conversion efficacy. The prepared core/shell nanocomplexes [MSN-Ce6@PDA (Mn)] were composed of chlorin e6-embedded mesoporous silica/nanoparticle composites as the cores, and then polydopamine and manganese ions were conjugated on the cores to form protective shells. The MSN-Ce6@PDA (Mn) nanocomplexes revealed superior properties in colloidal stability, photothermal conversion, reaction oxygen species generation, magnetic resonance imaging, etc. Under the guidance of MR and fluorescence imaging, these MSN-Ce6@PDA (Mn) nanocomplexes were found to be primarily accumulated in the MDA-MB-231 tumor area. Furthermore, the combined photodynamic and photothermal therapy exhibited strong inhibition to the growth of MDA-MB-231 tumor in vitro and in vivo. Besides, the MSN-Ce6@PDA (Mn) nanocomplexes also exhibited excellent biocompatibility and low damage to the healthy animals. Hence, the results demonstrated that the prepared MSN-Ce6@PDA (Mn) nanocomplex would be a promising potential for multimodal imaging-guided phototherapy.

[Morphological evaluation of the effectiveness of fluorescence navigation with chlorin e6 in surgery for malignant gliomas]

OBJECTIVE

To evaluate the effectiveness of fluorescence navigation with chlorin e6 in surgery for malignant gliomas based on surgical material morphological and immunohistochemical data.

MATERIAL AND METHODS

The surgical material obtained from patients with high-grade (Grade III-IV) anaplastic glioma was examined. Along with histological examination, the proliferation marker Ki-67, the cell cycle transcription factor protein p53, and vascular endothelial growth factor (VEGF) were determined.

RESULTS

A significant direct correlation was found between the expression of Ki-67, p53, and VEGF and the fluorescence intensity of tumor tissues (p<0.05).

CONCLUSION

The technique of fluorescence navigation using chlorin e6 in comparative morphopathological analysis has confirmed its effectiveness in surgery for malignant gliomas.

Efficient Delivery of Chlorin e6 by Polyglycerol-Coated Iron Oxide Nanoparticles with Conjugated Doxorubicin for Enhanced Photodynamic Therapy of Melanoma

Chlorin e6 (Ce6) is a promising photosensitizer for tumor photodynamic therapy (PDT). However, the efficacy of Ce6 PDT is limited by Ce6's poor water solubility, rapid blood clearance, and inadequate accumulation in the tumor tissue. This problem is tackled in this work, wherein functionalized superparamagnetic iron oxide nanoparticles (IO-NPs) were used as carriers to deliver Ce6 to melanoma. The IO-NPs were coated with polyglycerol (PG) to afford good aqueous solubility. The chemotherapeutic agent doxorubicin (DOX) was attached to the PG coating via the hydrazone bond to afford affinity to the cell membrane and thereby promote the cell uptake. The hydrophobic nature of DOX also induced the aggregation of IO-NPs to form nanoclusters. Ce6 was then loaded onto the IO nanoclusters through physical adsorption and coordination with surface iron atoms, yielding the final composites IO-PG-DOX-Ce6. In vitro experiments showed that IO-PG-DOX-Ce6 markedly increased Ce6 uptake in mouse melanoma cells, leading to much-enhanced photocytotoxicity characterized by intensified reactive oxygen species production, loss of viability, DNA damage, and stimulation of tumor cell immunogenicity. In vivo experiments corroborated the in vitro findings and demonstrated prolonged blood clearance of IO-PG-DOX-Ce6. Importantly, IO-PG-DOX-Ce6 markedly increased the Ce6 distribution and retention in mouse subcutaneous melanoma grafts and significantly improved the efficacy of Ce6-mediated PDT. No apparent vital organ damage was observed at the same time. In conclusion, the IO-PG-DOX NPs provide a simple and safe delivery platform for efficient tumor enrichment of Ce6, thereby enhancing antimelanoma PDT.

Synergetic antimicrobial effect of chlorin e6 and hydrogen peroxide on multi-species biofilms

Antimicrobial photodynamic therapy (aPDT) has been considered as a potential alternative to antibiotics for the treatment of biofilm infections. There is evidence that an additional H₂O₂ enhances the antimicrobial efficacy of aPDT. However, the minimum H₂O₂ concentration to achieve this synergistic effect is unclear. A saliva-derived multi-species biofilm was treated with the photosensitizer chlorin e6 (Ce6, 50 µM), H₂O₂ (0.3, 3.3, 33.3 mM), or their combination for 5 min, followed by no irradiation or irradiation at 15 J (cm²)^-1 (λ = 450 nm or 660 nm), with or without oxygen. Biofilm viability and metabolic activity were evaluated. The combination of 33.3 mM H₂O₂ and Ce6-aPDT strongly enhanced antimicrobial efficacy compared with either component alone, irrespective of oxygen availability and irradiation wavelength. In particular, the combination resulted in a 6.6-log colony forming unit (CFU) reduction anaerobically under blue irradiation. This combination is a promising treatment for biofilm infections, especially those thriving in an anaerobic microenvironment.

Targeted and oxygen-enriched polymeric micelles for enhancing photodynamic therapy

Photodynamic therapy (PDT) has been emerged as an alternative therapeutic modality in treatment of several malignant tumors. However, the therapeutic efficacy of PDT is often limited by the solubility of photosensitizers, tumor hypoxia and lack of target specificity to cancer cells. In this study, we developed a folate-conjugated fluorinated polymeric micelle (PFFA) to deliver the hydrophobic photosensitizer (chlorin e6, Ce6) to overcome these limitations. The fluorinated micelles exhibit the low critical micelle concentration, good long-term stability, higher oxygen-carrying capacity and better singlet oxygen generation efficiency compared to non-fluorinated micelles, indicating the potential to improve the PDT efficacy in hypoxic conditions. Cytotoxicity of PDT effect and cellular uptake demonstrate the higher cell growth inhibition to HeLa cells upon irradiation attributed to the selective internalization of Ce6-loaded PFFA micelles (PFFA-Ce6). All results demonstrate the PFFA-Ce6 micelles with targeting function and oxygen-carrying capacity can serve as a promising drug delivery system for hydrophobic photosensitizers and improvement on PDT efficacy.

Modeling the binding of protoporphyrin IX, verteporfin, and chlorin e6 to SARS-CoV-2 proteins

In this work, we analyze the latest data on the molecular docking of a range of SARS-CoV-2 proteins to protoporphyrin IX, verteporfin, and chlorin e6, as well as consider the prospects for using chlorins and porphyrins as agents for photoinactivation of the SARS2 virus.

An effective method to generate controllable levels of ROS for the enhancement of HUVEC proliferation using a chlorin e6-immobilized PET film as a photo-functional biomaterial

Reactive oxygen species (ROS) are byproducts of cellular metabolism; they play a significant role as secondary messengers in cell signaling. In cells, high concentrations of ROS induce apoptosis, senescence, and contact inhibition, while low concentrations of ROS result in angiogenesis, proliferation, and cytoskeleton remodeling. Thus, controlling ROS generation is an important factor in cell biology. We designed a chlorin e6 (Ce6)-immobilized polyethylene terephthalate (PET) film (Ce6-PET) to produce extracellular ROS under red-light irradiation. The application of Ce6-PET films can regulate the generation of ROS by altering the intensity of light-emitting diode sources. We confirmed that the Ce6-PET film could effectively promote cell growth under irradiation at 500 μW/cm2 for 30 min in human umbilical vein endothelial cells. We also found that the Ce6-PET film is more efficient in generating ROS than a Ce6-incorporated polyurethane film under the same conditions. Ce6-PET fabrication shows promise for improving the localized delivery of extracellular ROS and regulating ROS formation through the optimization of irradiation intensity.

Self-assembly supramolecular drug delivery system for combination of photodynamic therapy and chemotherapy

AIMS

To construct a self-assembly supramolecular drug delivery system (DDS) to co-deliver chlorin e6 (Ce6) and tripeptide tyroseroleutide (YSL) and evaluate the anti-tumour effects.

METHODS

A supramolecular DDS was constructed via self-assembly of Ce6 and YSL based on π-π stacking and hydrogen-bond interaction. The size, morphology, stability, in vitro drug release, cellular uptake, cytotoxicity, pharmacokinetics analysis and pharmacodynamics analysis were respectively studied.

RESULTS

Ce6-YSL nanoparticles with a uniform size of 75 ± 3.5 nm (PDI = 0.128) and monodispersed spherical morphology were constructed. The nanoparticles exhibited good stability with zeta potential -21.2 ± 1.73 mV. Under the weak acidic conditions, the accumulative drug release was 82.8% (w/w) (pH = 6.0) and 91.5% (w/w) (pH = 5.0), respectively, indicating that nanoparticles performed smart responsive properties and achieved controlled release characteristics in acidic tumour microenvironment. In addition, nanoparticles could easily enter the tumour cells and induce ROS production and inhibit cell proliferation in SMMCC-7721 cells with IC50 value 3.4 ± 0.023 μg/mL under laser irradiation. Furthermore, the nanoparticles could retain a much higher blood concentration in vivo and displayed excellent antitumor effect in tumour-bearing mice, showing no influence on body weight.

CONCLUSIONS

This self-assembly supramolecular DDS can be used for combination of photodynamic therapy and chemotherapy in future research.

A Multifunctional Nanosystem Based on Bacterial Cell-Penetrating Photosensitizer for Fighting Periodontitis Via Combining Photodynamic and Antibiotic Therapies

Photodynamic therapy (PDT), an emerging approach that involves photosensitizers, light, and molecular oxygen, has shown promise for fighting periodontitis. However, PDT does not always acquire the desired therapeutic outcomes since some photosensitizers have strong hydrophobic properties and are difficult to absorb efficiently by periodontal pathogenic bacteria. Here, a hydrophobic photosensitizer chlorin e6 (Ce6) was hydrophilically modified via conjugation with TAT peptide, a cationic cell-penetrating peptide, to improve its solubility and enhance its bacterial adsorption by promoting its interaction with the negatively charged cell walls and penetration through the cell membranes. The obtained TAT-Ce6 conjugate (TAT-Ce6) was used to prepare self-assembled nanoparticles (NPs) for loading tinidazole (TDZ), a clinically used antibiotic agent, thus hoping to achieve synergistic antiperiodontitis effects through combining PDT and antibiotic therapy. Compared to free Ce6, TAT-Ce6 nanoparticles (TAT-Ce6 NPs) had greatly enhanced adsorption and penetration abilities for periodontal pathogen bacteria and also exhibited significantly increased PDT efficiencies in both periodontal pathogen bacteria and monocyte macrophages. Upon 635 nm laser irradiation, TDZ-loaded TAT-Ce6 (TAT-Ce6/TDZ) NPs exerted remarkable synergistic antiperiodontitis effects of PDT and antibiotic therapy, reflecting in the effective killing of periodontal pathogenic bacteria in vitro and the reduced adsorption of alveolar bone in the Sprague-Dawley rat model of periodontitis. Altogether, this study develops a novel photosensitizer that can be efficiently absorbed by the periodontal pathogenic bacteria and also provides a potent combination strategy of PDT with antibiotic therapy for clinical periodontitis treatment.

In Vitro Photodynamic Effects of the Inclusion Nanocomplexes of Glucan and Chlorin e6 on Atherogenic Foam Cells

Macrophage-derived foam cells play critical roles in the initiation and progression of atherosclerosis. Activated macrophages and foam cells are important biomarkers for targeted imaging and inflammatory disease therapy. Macrophages also express the dectin-1 receptor, which specifically recognizes β-glucan (Glu). Here, we prepared photoactivatable nanoagents (termed Glu/Ce6 nanocomplexes) by encapsulating hydrophobic chlorin e6 (Ce6) within the triple-helix structure of Glu in aqueous condition. Glu/Ce6 nanocomplexes generate singlet oxygen upon laser irradiation. The Glu/Ce6 nanocomplexes were internalized into foam cells and delivered Ce6 molecules into the cytoplasm of foam cells. Upon laser irradiation, they induced significant membrane damage and apoptosis of foam cells. These results suggest that Glu/Ce6 nanocomplexes can be a photoactivatable material for treating atherogenic foam cells.

New approaches to diagnostics and treatment of cholangiocellular cancer based on photonics methods

Cholangiocellular cancer (CCC) is an oncological disease of the bile ducts characterized by a high mortality rate. To date, the use of standard methods for the diagnosis and treatment of CCC has not been able to reduce mortality from this disease. This work presents the results of fluorescence diagnostics (FD), which consists in using a modified optical fiber and photodynamic therapy (PDT) using a therapeutic laser instead of a low-intensity laser. This technique was tested on 43 patients in a clinical setting. The results obtained indicate a direct correlation between spectroscopic and video FD methods. Furthermore, a direct correlation was found between the photobleaching of a chlorin e6-based photosensitizer, with the commercial names of Photolon Radachlorin and Photoran and stricture regression. Our findings demonstrate the possibility of using a therapeutic laser with a wavelength of 660 nm for both diagnosis and treatment of bile ducts cancer, which results in a significant reduction of the operation time without decreasing its effectiveness.

Multifunctional nanoparticle PEG‑Ce6‑Gd for MRI‑guided photodynamic therapy

Gliomas are one of the most common types of primary brain tumors. Despite recent advances in the combination of surgery, radiotherapy, systemic therapy (chemotherapy, targeted therapy) and supportive therapy in the multimodal treatment of gliomas, the overall prognosis remains poor and the long‑term survival rate is low. Thus, it is crucial to develop a novel glioma management method. Due to its relatively non‑invasive, selective and repeatable characteristics, photodynamic therapy (PDT) has been investigated for glioma therapy in the past decade, exhibiting higher selectivity and lower side effects compared with those of conventional therapy. However, most of the photosensitizers (PSs) are highly hydrophobic, leading to poor water solubility, rapid degradation with clearance in blood circulation and ultimately, low bioavailability. In the present study, hydrophilic polyethylene glycol (PEG)‑chlorin e6 (Ce6) chelated gadolinium ion (Gd3+) nanoparticles (PEG‑Ce6‑Gd NPs) were synthesized via a chelation and self‑assembly process. Initially, the cell cytotoxicity of PEG‑Ce6‑Gd NPs was evaluated with or without laser irradiation. The in vitro study demonstrated the lack of toxicity of PEG‑Ce6‑Gd NPs to tumor cells in the absence of laser irradiation. However, its toxicity was enhanced under laser irradiation. Moreover, the size and weight of brain tumors were significantly decreased in mice with glioma xenografts, which was further confirmed via histological analysis. Subsequently, the results indicated that the PEG‑Ce6‑Gd NPs had a favorable T1‑weighted contrast performance (0.43 mg ml‑1 s‑1) and were observed to have significant contrast enhancement at the tumor site from 0.25 to 1 h post‑injection in vivo. The favorable MRI, as well as the synergetic photodynamic antitumor effect and antineoplastic ability of PEG‑Ce6‑Gd NPs was identified. It was suggested that PEG‑Ce6‑Gd NPs had great potential in the diagnosis and PDT treatment of gliomas, and possibly other cancer types, with prospects of clinical application in the near future.

A few-layer graphene/chlorin e6 hybrid nanomaterial and its application in photodynamic therapy against Candida albicans

The global emergence of multidrug resistance of fungal infections and the decline in the discovery of new antibiotics are increasingly prevalent causes of hospital-acquired infections, among other major challenges in the global health care sector. There is an urgent need to develop noninvasive, nontoxic, and new antinosocomial approaches that work more effectively and faster than current antibiotics. In this work, we report on a biocompatible hybrid nanomaterial composed of few-layer graphene and chlorin e6 (FLG-Ce6) for the photodynamic treatment (PDT) of Candida albicans. We show that the FLG-Ce6 hybrid nanomaterial displays enhanced reactive oxygen species (ROS) generation compared with Ce6. The enhancement is up to 5-fold when irradiated for 15 min at 632 nm with a red light-emitting diode (LED). The viability of C. albicans in the presence of FLG-Ce6 was measured 48 h after photoactivation. An antifungal effect was observed only when the culture/FLG-Ce6 hybrid was exposed to the light source. C. albicans is rendered completely unviable after exposure to ROS generated by the excited FLG-Ce6 hybrid nanomaterial. An increased PDT effect was observed with the FLG-Ce6 hybrid nanomaterial by a significant reduction in the viability of C. albicans, by up to 95%. This is a marked improvement compared to Ce6 without FLG, which reduces the viability of C. albicans to only 10%. The antifungal action of the hybrid nanomaterial can be activated by a synergistic mechanism of energy transfer of the absorbed light from Ce6 to FLG. The novel FLG-Ce6 hybrid nanomaterial in combination with the red LED light irradiation can be used in the development of a wide range of antinosocomial devices and coatings.

Antimicrobial Photodynamic Therapy with Chlorin e6 Is Bactericidal against Biofilms of the Primary Human Otopathogens

Otitis media (OM), or middle ear disease, is the most prevalent bacterial infection in children and the primary reason for antibiotic use and surgical intervention in the pediatric population. Biofilm formation by the major bacterial otopathogens, Moraxella catarrhalis, Streptococcus pneumoniae, and nontypeable Haemophilus influenzae, has been shown to occur within the middle ears of OM patients and is a key factor in the development of recurrent disease, which may result in hearing impairment and developmental delays. Bacterial biofilms are inherently impervious to most antibiotics and present a significant challenge to the immune system. In this study, we demonstrate that antimicrobial photodynamic therapy (aPDT) using the photosensitizer chlorin e6 elicits significant bactericidal activity versus planktonic and biofilm-associated otopathogens and supports further analyses of this novel, efficacious, and promising technology as an adjunctive treatment for acute and recurrent OM.

Moraxella catarrhalis, Streptococcus pneumoniae, and nontypeable Haemophilus influenzae (NTHi) are ubiquitous upper respiratory opportunistic pathogens. Together, these three microbes are the most common causative bacterial agents of pediatric otitis media (OM) and have therefore been characterized as the primary human otopathogens. OM is the most prevalent bacterial infection in children and the primary reason for antibiotic administration in this population. Moreover, biofilm formation has been confirmed as a primary mechanism of chronic and recurrent OM disease. As bacterial biofilms are inherently metabolically recalcitrant to most antibiotics and these complex structures also present a significant challenge to the immune system, there is a clear need to identify novel antimicrobial approaches to treat OM infections. In this study, we evaluated the potential efficacy of antibacterial photodynamic therapy (aPDT) with the photosensitizer chlorin e6 (Ce6) against planktonic as well as biofilm-associated M. catarrhalis, S. pneumoniae, and NTHi. Our data indicate aPDT with Ce6 elicits significant bactericidal activity against both planktonic cultures and established biofilms formed by the three major otopathogens (with an efficacy of ≥99.9% loss of viability). Notably, the implementation of a novel, dual-treatment aPDT protocol resulted in this disinfectant effect on biofilm-associated bacteria and, importantly, inhibited bacterial regrowth 24 h posttreatment. Taken together, these data suggest this novel Ce6-aPDT treatment may be a powerful and innovative therapeutic strategy to effectively treat and eradicate bacterial OM infections and, significantly, prevent the development of recurrent disease.

IMPORTANCE Otitis media (OM), or middle ear disease, is the most prevalent bacterial infection in children and the primary reason for antibiotic use and surgical intervention in the pediatric population. Biofilm formation by the major bacterial otopathogens, Moraxella catarrhalis, Streptococcus pneumoniae, and nontypeable Haemophilus influenzae, has been shown to occur within the middle ears of OM patients and is a key factor in the development of recurrent disease, which may result in hearing impairment and developmental delays. Bacterial biofilms are inherently impervious to most antibiotics and present a significant challenge to the immune system. In this study, we demonstrate that antimicrobial photodynamic therapy (aPDT) using the photosensitizer chlorin e6 elicits significant bactericidal activity versus planktonic and biofilm-associated otopathogens and supports further analyses of this novel, efficacious, and promising technology as an adjunctive treatment for acute and recurrent OM.

Effective Photodynamic Therapy for Colon Cancer Cells Using Chlorin e6 Coated Hyaluronic Acid-Based Carbon Nanotubes

Colon cancer is the third major cancer contributor to mortality worldwide. Nanosized particles have attracted attention due to their possible contribution towards cancer treatment and diagnosis. Photodynamic therapy (PDT) is a cancer therapeutic modality that involves a light source, a photosensitizer and reactive oxygen species. Carbon nanotubes are fascinating nanocarriers for drug delivery, cancer diagnosis and numerous potential applications due to their unique physicochemical properties. In this study, single walled carbon nanotubes (SWCNTs) were coupled with hyaluronic acid (HA) and chlorin e6 (Ce6) coated on the walls of SWCNTs. The newly synthesized nanobiocomposite was characterized using ultraviolet-visible spectroscopy, Fourier transform electron microscopy (FTIR), X-ray diffraction analysis (XRD), particle size analysis and zeta potential. The loading efficiency of the SWCNTs-HA for Ce6 was calculated. The toxicity of the nanobiocomposite was tested on colon cancer cells using PDT at a fluence of 5 J/cm² and 10 J/cm². After 24 h, cellular changes were observed via microscopy, LDH cytotoxicity assay and cell death induction using annexin propidium iodide. The results showed that the newly synthesized nanobiocomposite enhanced the ability of PDT to be a photosensitizer carrier and induced cell death in colon cancer cells.

Nanophotosensitizers for Folate Receptor-Targeted and Redox-Sensitive Delivery of Chlorin E6 against Cancer Cells

In this study, FA-PEG₃₅₀₀-ss-Ce6tri copolymer was synthesized to deliver photosensitizers via redox-sensitive and folate receptor-specific manner. Folic acid (FA) was attached to amine end of poly (ethylene glycol) (PEG₃₅₀₀) (FA-PEG₃₅₀₀ conjugates) and cystamine-conjugated chlorin e6 (Ce6) (Ce6-cystamine conjugates). FA-PEG₃₅₀₀ was further conjugated with Ce6-cystamine to produce FA-PEG₃₅₀₀-ss-Ce6 conjugates. To the remaining amine end group of Ce6-cystamine conjugates, Ce6 was attached to produce FA-PEG₃₅₀₀-ss-Ce6tri. Nanophotosensitizers of FA-PEG₃₅₀₀-ss-Ce6tri copolymer were smaller than 200 nm. Their shapes were disintegrated by treatment with GSH and then Ce6 released by GSH-dependent manner. Compared to Ce6 alone, FA-PEG₃₅₀₀-ss-Ce6tri copolymer nanophotosensitizers recorded higher Ce6 uptake ratio, reactive oxygen species (ROS) production and cellular cytotoxicity against KB and YD-38 cells. The in vitro and in vivo study approved that delivery of nanophotosensitizers is achieved by folate receptor-sensitive manner. These results indicated that FA-PEG₃₅₀₀-ss-Ce6tri copolymer nanophotosensitizers are superior candidate for treatment of oral cancer.

Hydrogen Peroxide-Activatable Nanoparticles for Luminescence Imaging and In Situ Triggerable Photodynamic Therapy of Cancer

Abnormally increased reactive oxygen species (ROS) are intimately related to the development and metastasis of cancer. Since hydrogen peroxide (H₂O₂) is a major component of ROS, molecular imaging and selective treatment in response to high H₂O₂ are intriguing for the management of cancers. Herein, we report novel self-assembly luminescent nanoparticles, which can be activated by H₂O₂, thereby serving as an effective nanotheranostics for luminescence imaging and in situ photodynamic therapy (PDT) of tumors with high H₂O₂. This functional nanomedicine was assembled from an amphiphilic conjugate (defined as CLP) based on chlorin e6 (Ce6) simultaneously conjugated with luminol and poly(ethylene glycol), exhibiting a well-defined core-shell nanostructure. Upon triggering by pathologically relevant levels of H₂O₂, CLP nanoparticles produced luminescence due to the luminol unit and simultaneous excitation of Ce6 by chemiluminescence resonance energy transfer, enabling in vitro and in vivo imaging of tumors with highly expressed H₂O₂. In addition, excited Ce6 can produce singlet oxygen (¹O₂) for in situ PDT of H₂O₂-high tumors and inhibiting lung metastasis, which was demonstrated by in vitro and in vivo experiments. Furthermore, preliminary studies revealed the biosafety of CLP nanoparticles. Consequently, the self-illuminating nanoparticles are promising for noninvasive imaging and therapy of tumors with high expression of H₂O₂.

Hypoxia-Targeting Multifunctional Nanoparticles for Sensitized Chemotherapy and Phototherapy in Head and Neck Squamous Cell Carcinoma

Purpose

Chemotherapy in head and neck squamous cell carcinoma (HNSCC) has many systemic side effects, as well as hypoxia-induced chemoresistance. To reduce side effects and enhance chemosensitivity are urgently needed.

Methods

We synthesized a drug delivery system (named CECMa NPs) based on cisplatin (CDDP) and metformin (chemotherapeutic sensitizer), of which chlorin e6 (Ce6) and polyethylene glycol diamine (PEG) were synthesized as the shell, an anti-LDLR antibody (which can target to hypoxic tumor cells) was modified on the surface to achieve tumor targeting.

Results

The NPs possessed a great synergistic effect of chemotherapy and phototherapy. After laser stimulation, both CDDP and metformin can be released in situ to achieve anti-tumor effects. Meanwhile, PDT and PTT triggered by a laser have anticancer effects. Furthermore, compared with free cisplatin, CECMa exhibits less systemic toxicity with laser irradiation in the xenograft mouse tumor model.

Conclusion

CECMa effectively destroyed the tumors via hypoxia targeting multimodal therapy both in vitro and in vivo, thereby providing a novel strategy for targeting head and neck squamous cell carcinoma.

[Chlorine e6 in phospholipid nanoparticles with specific targeting and penetrating peptides as prospective composition for photodynamic therapy of malignant neoplasms]

Cytotoxic and photoinduced activity of chlorine e6 (Ce6) in phospholipid nanoparticles with specific tumor targeting and cell-penetrating peptides was studied in vitro using human fibrosarcoma cells HT-1080. It was shown, that the binding of cell-penetrating peptide R7 - alone or combined with the peptide containing specific targeting motif NGR (Asn-Gly-Arg) - resulted in 3-fold decrease of Ce6 photoinduced activity as compared with that in nanoparticles without peptides (IC50 values were 0.7 μg/ml and 2.1 μg/ml, respectively). The NGR influence was unexpectedly low - less than 20% (IC50 1.7 μg/ml). This suggests the more importance of Ce6 cell penetration in this case, than of NGR-mediated targeting. The effect of inclusion of both peptides on the total cytotoxicity of Ce6 was minimal (10-16 times less than on the specific photoinduced activity). The obtained results - together with earlier shown effects on improvement of the pharmacokinetics of Ce6 in vivo after its embedding into phospholipid nanoparticles - indicate the prospects of using the obtained phospholipid nanoparticles system for photodynamic therapy.

Degradable Calcium Phosphate-Coated Upconversion Nanoparticles for Highly Efficient Chemo-Photodynamic Therapy

The development of a stimulus-responsive nanosystem provides an effective method for improving the accuracy and efficiency of chemotherapy. Meanwhile, traditional photodynamic therapy (PDT) has been substantially restricted by the low dosage of photosensitizer and limited penetration depth of the ultraviolet (UV) or visible light used for excitation. Here, we designed a smart multifunctional nanoplatform by coating core-shell composite mesoporous silica-encapsulated upconversion nanoparticles and chlorin e6 (Ce6) with degradable calcium phosphate, followed by the loading of doxorubicin (DOX). In our structure, the as-synthesized nanoplatform exhibits high responsiveness to a low pH value and degrades rapidly in the weakly acidic tumor microenvironment, allowing the quick release of loaded DOX in tumor sites. Interestingly, the loaded DOX, whose release depends on the pH value and positively correlates with the calcium-ion concentration, enables drug release to be monitored in real time. Combined with photosensitizer Ce6-induced PDT triggered by an 808 nm near-infrared light, synergistic chemo-photodynamic therapy is achieved, thus leading to a highly efficient anticancer treatment in vitro and in vivo. Importantly, the inherent properties of rare earth ions (Gd³⁺, Yb³⁺, and Nd³⁺) make the nanoplatform possess UCL, MRI, and CT trimode imaging capabilities, thus achieving a multiple imaging modality-guided synergistic therapy.

Trials of a Fluorescent Endoscopic Video System for Diagnosis and Treatment of the Head and Neck Cancer

This article presents the results of intraoperative fluorescent diagnostics via the endoscopic system for assessing the quality of photodynamic therapy (PDT) of head and neck cancer. The diagnosis and PDT procedures were performed on the five patients with malignant neoplasms of the vocal cords, lateral surface of the tongue, and trachea and cancer of the left parotid salivary gland. Molecular form of chlorin E6 (Ce6) was intravenously administered with a 1.0–1.1 mg/kg concentration for PDT. Fluorescent diagnostics (FD) was conducted before PDT and after PDT procedures. Control of PDT efficiency was carried out by evaluating the photobleaching of the drug (photosensitizer). The method of intraoperative fluorescent imaging allows determining the exact location of the tumor and its boundaries. The assessment of photosensitizer photobleaching in real time regime allows making quick decisions during PDT procedure, which helps improving the quality of patients’ treatment. The results showed the convenience of endoscopic fluorescent video system in various nosologies of head and neck cancer. Therefore, this diagnostic approach will improve the effectiveness of cancer treatment.

Programmable Ce6 Delivery via Cyclopamine Based Tumor Microenvironment Modulating Nano-System for Enhanced Photodynamic Therapy in Breast Cancer

Photodynamic therapy (PDT) has shown great promise in breast cancer treatment. However, simplex target ligand modification or stimuli release cannot meet the requirement of effective drug delivery to solid tumor tissue. To overcome continuous bio-barriers existing in the tumor microenvironment, multi-stage response drug delivery was desirable. Herein, we developed a unique tumor microenvironment tailored nanoplatform for chlorin e6 (Ce6) delivery. We chose bovine serum albumin (BSA) as “mother ships” material for effective tumor periphery resident, cyclopamine (CYC) as extracellular matrix (ECM) inhibitor and synergistic anti-tumor agent, and diselenide containing amphiphilic hyaluronic acid-chlorin e6 polymers (HA-SeSe-Ce6) synthesized as “small bombs” for internal tissue destruction. The above three distinct function compositions were integrated into an independent CYC and HA-SeSe-Ce6 co-delivery albumin nano-system (ABN@HA-SeSe-Ce6/CYC). The obtained nano-system presents good biocompatible, long circulation and effective tumor accumulation. After entering tumor microenvironment, CYC gradually releases to disrupt the ECM barrier to open the way for further penetration of HA-SeSe-Ce6. Subsequently, targeted tumor cell internalization and intracellular redox response release of Ce6 would achieve. Moreover, CYC could also make up the deficiency of Ce6 in hypoxia area, owing to its anti-tumor effect. Improved therapeutic efficacy was verified in a breast cancer cell line and tumor-bearing mice model.