Comparison of a new nanoform of the photosensitizer chlorin e6, based on plant phospholipids, with its free form

Cyclic peptide conjugated photosensitizer for targeted phototheranostics of gram-negative bacterial infection

Antimicrobial photodynamic therapy (PDT) is a promising alternative to antibiotics for eradicating pathogenic bacterial infections. It holds advantage of not inducing antimicrobial resistance but is limited for the treatment of gram-negative bacterial infection due to the lack of photosensitizer (PS) capable of targeted permeating the outer membrane (OM) of gram-negative bacteria. To facilitate the targeted permeability of PS, cyclic polymyxin b nonapeptide that can specifically bind to the lipopolysaccharide on OM, is conjugated to an FDA approved PS chlorin e6 via variable linkers. Based on structure to activity study, C6pCe6 with aminohexanoic linker and P2pCe6 with amino-3, 6-dioxaoctanoic linker are identified to preferentially image gram-negative bacteria. These two conjugates also exhibit improved aqueous dispersity and enhanced ROS generation, consequently enabled their selective bactericidal activities against gram-negative bacteria upon 660 nm light irradiation. The effective photobactericidal ability of P2pCe6 is further validated on P. aeruginosa infected G. mellonella. Moreover, it is demonstrated to effectively treat the P. aeruginosa infection and accelerate the healing process at the wound site of mouse. Owing to the light irradiation triggered targeted imaging and enhanced bactericidal capacities, P2pCe6 hold great potential to serve as a potent PS for mediating the phototheranostics of gram-negative bacterial infection.

Response surface methodological approach for optimization of photodynamic therapy of onychomycosis using chlorin e6 loaded nail penetration enhancer vesicles

Antimicrobial photodynamic inactivation (aPDI) has a tremendous potential as an alternative therapeutic modality to conventional antifungals in treatment of onychomycosis, yet the nail barrier properties and the deep-seated nature of fungi within the nails remain challenging. Therefore, the aim of this study was to prepare, optimize, and characterize Chorin e6 (Ce6) nail penetration enhancer containing vesicles (Ce6-nPEVs) and evaluate their photodynamic mediated effect against Trichophyton rubrum (T.rubrum); the main causative agent of onychomycosis. Optimization of the particle size and encapsulation efficiency of nPEVs was performed using a four-factor two-level full factorial design. The transungual delivery potential of the selected formulation was assessed in comparison with the free drug. The photodynamic treatment conditions for T.rubrum aPDI by free Ce6 was optimized using response surface methodology based on Box-Behnken design, and the aPDI effect of the selected Ce6-nPEVs was evaluated versus the free Ce6 at the optimized condition. Results showed that formulations exhibited high encapsulation efficiency for Ce6 ranging from 79.4 to 98%, particle sizes ranging from 225 to 859 nm, positive zeta potential values ranging from +30 to +70 mV, and viscosity ranging from 1.26 to 3.43 cP. The predominant parameters for maximizing the encapsulation efficiency and minimizing the particle size of Ce6-nPEVs were identified. The selected formulation showed 1.8-folds higher nail hydration and 2.3 folds improvement in percentage of Ce6 up-taken by nails compared to the free drug. Results of the microbiological study confirmed the reliability and adequacy of the Box-Behnken model, and delineated Ce6 concentration and incubation time as the significant model terms. Free Ce6 and Ce6-nPEVs showed an equipotent in vitro fungicidal effect on T.rubrum at the optimized conditions, however Ce6-nPEVs is expected to show a differential effect at the in vivo level where the advantage of the enhanced nail penetration feature will be demonstrated.

Development of Novel Tetrapyrrole Structure Photosensitizers for Cancer Photodynamic Therapy

The effectiveness of photodynamic therapy (PDT) is based on the triad effects of photosensitizer (PS), molecular oxygen and visible light on malignant tumors. Such complex induces a multifactorial manner including reactive-oxygen-species-mediated damage and the killing of cells, vasculature damage of the tumor, and activation of the organism immunity. The effectiveness of PDT depends on the properties of photosensitizing drugs, their selectivity, enhanced photoproduction of reactive particles, absorption in the near infrared spectrum, and drug delivery strategies. Photosensitizers of the tetrapyrrole structure (porphyrins) are widely used in PDT because of their unique diagnostic and therapeutic functions. Nevertheless, the clinical use of the first-generation PS (sodium porfimer and hematoporphyrins) revealed difficulties, such as long-term skin photosensitivity, insufficient penetration into deep-seated tumors and incorrect localization to it. The second generation is based on different approaches of the synthesis and conjugation of porphyrin PS with biomolecules, which made it possible to approach the targeted PDT of tumors. Despite the fact that the development of the second-generation PS started about 30 years ago, these technologies are still in demand and are in intensive development, especially in the direction of improving the process of optimization split linkers responsive to input. Bioconjugation and encapsulation by targeting molecules are among the main strategies for developing of the PS synthesis. A targeted drug delivery system with the effect of increased permeability and retention by tumor cells is one of the ultimate goals of the synthesis of second-generation PS. This review presents porphyrin PS of various generations, discusses factors affecting cellular biodistribution and uptake, and indicates their role as diagnostic and therapeutic (theranostic) agents. New complexes based on porphyrin PS for photoimmunotherapy are presented, where specific antibodies are used that are chemically bound to PS, absorbing light from the near infrared part of the spectrum. Additionally, a two-photon photodynamic approach using third-generation photosensitizers for the treatment of tumors is discussed, which indicates the prospects for the further development of a promising method antitumor PDT.

A Pilot Study of Fluorescence-Guided Resection of Pituitary Adenomas with Chlorin e6 Photosensitizer

Fluorescence diagnostics is one of the promising methods for intraoperative detection of brain tumor boundaries and helps in maximizing the extent of resection. This paper presents the results of a pilot study on the first use of the chlorin e6 photosensitizer and a two-channel video system for fluorescence-guided resection of pituitary adenomas. The study’s clinical part involved two patients diagnosed with hormonally inactive pituitary macroadenomas and one patient with a hormonally active one. All neoplasms had different sizes and growth patterns. The data showed accumulation of chlorin e6 in tumor tissues in high concentrations: Patient 1: 2 mg/kg, Patient 2: 5 mg/kg, and Patient 3: 4 mg/kg. For Patient 1, the residual part of the tumor was not resected since it was intimately attached to the anterior genu of the internal carotid artery. For Patients 2 and 3, no regions of increased Ce6 accumulation were detected in the tumor foci after resection. Therefore, the use of the Ce6 and a two-channel video system helped to achieve a high degree of tumor resection in each case.

Phototheranostics of Cervical Neoplasms with Chlorin e6 Photosensitizer

Simple Summary

Neoplasms of the cervix are the most common types of oncological pathology. Photodynamic therapy with intravenous administration of the photosensitizer chlorin e6 shows high efficiency in the treatment of precancerous lesions of the cervix with complete eradication of the human papillomavirus. The treatment method can reduce deaths from cervical cancer and preserve fertility in patients. Spectral and video fluorescence diagnostics allows intraoperatively assessing the degree of photosensitizer accumulation and photobleaching and visualizing the boundaries of pathologically altered tissues.

Abstract

(1) Purpose: Improving the treatment effectiveness of intraepithelial neoplasia of the cervix associated with human papillomavirus infection, based on the application of the method of photodynamic therapy with simultaneous laser excitation of fluorescence to clarify the boundaries of cervical neoplasms. (2) Methods: Examination and treatment of 52 patients aged 22 to 53 years with morphologically and cytologically confirmed mild to severe intraepithelial cervix neoplasia, preinvasive, micro-invasive, and squamous cell cervix carcinoma. All patients were carriers of human papillomavirus infection. The patients underwent photodynamic therapy with simultaneous laser excitation of fluorescence. The combined use of video and spectral fluorescence diagnostics for cervical neoplasms made it possible to control the photodynamic therapy process at all stages of the procedure. Evaluation of the photodynamic therapy of intraepithelial cervical neoplasms was carried out with colposcopic examination, cytological conclusion, and morphological verification of the biopsy material after the photodynamic therapy course. The success of human papillomavirus therapy was assessed based on the results of the polymerase chain reaction. (3) Results. The possibility of simultaneous spectral fluorescence diagnostics and photodynamic therapy using a laser source with a wavelength of 660 nm has been established, making it possible to assess the fluorescence index in real-time and control the photobleaching of photosensitizers in the irradiated area. The treatment of all 52 patients was successful after the first photodynamic therapy procedure. According to the PCR test of the discharge from the cervical canal, the previously identified HPV types were not observed in 48 patients. Previously identified HPV types were absent after repeated PDT in four patients (CIN III (n = 2), CIS (n = 2)). In 80.8% of patients, regression of the lesion was noted. (4) Conclusions. The high efficiency of photodynamic therapy with intravenous photosensitizer administration of chlorin e6 has been demonstrated both in relation to eradication therapy of human papillomavirus and in relation to the treatment of intraepithelial lesions of the cervix.

[The effect of lipid derivative of anti-tumor drug sarcolysin embedded in phospholipid nanoparticles in the experiments in vivo]

To improve the therapeutic properties of the antitumor agent Sarcolysin, we have previously developed and characterized a dosage form representing its ester conjugate with decanol embedded in ultra-small phospholipid nanoparticles less than 30 nm in size ("Sarcolysin-NP"). The effect of the resulting composition was investigated in vivo in comparison with the free substance of sarcolysin. The composition intravenous administration to mice showed an improvement in the pharmacokinetic parameters of sarcolysin associated with its initial higher (by 22%) level in the blood and prolonged circulation, which was also observed in mice with P388 tumor. In mice with three types of tumors - lymphocytic leukemia P388, lymphocytic leukemia L1210, and adenocarcinoma of the mammary gland Ca755 - administration of two doses of sarcolysin over a period of 7 days showed its predominant antitumor effect. The maximum tumor growth inhibition was noted for lymphocytic leukemia L1210 and adenocarcinoma of the mouse mammary gland Ca755 (at a dose of Sarcolysin-NP - 8,4 mg/kg), which was higher in comparison with free substance by more than 24% and 17%, respectively. Differences in the life span of the treated animals were revealed significantly at a dose of 10 mg/kg and amounted to 25% and 17,4% for lymphocytic leukemia P388 and L1210, respectively, and 11% for adenocarcinoma Ca755. In an experiment on rats, acute toxicity of Sarcolysin-NP administered intravenously showed that an average LD50 value 2-3 times exceeded a similar parameter for commercial preparations of free sarcolysin (Melphalan and Alkeran), which indicates its lower toxicity.

Nanoliposomes as drug delivery systems: safety concerns

The review highlights the safety issues of drug delivery systems based on liposomes. Due to their small sizes (about 80-120 nm, sometimes even smaller), phospholipid nanoparticles interact intensively with living systems during parenteral administration. This interaction significantly affects both their transport role and safety; therefore, special attention is paid to these issues. The review summarises the data on the basic factors affecting the safety of nanoliposomes: composition, size, surface charge, stability, the release of an incorporated drug, penetration into tissues, interaction with the complement system. Attention is paid to the authors' own research of unique phospholipid nanoparticles with a diameter of 20-30 nm. The influence of technological processes of nanoliposome production on their properties is considered. The article also discusses the modern safety assessment criteria contained in the preliminary regulatory documents of the manufacturing countries for new nanoliposome-based drugs being developed or used in the clinic.

MnO2-capped silk fibroin (SF) nanoparticles with chlorin e6 (Ce6) encapsulation for augmented photo-driven therapy by modulating the tumor microenvironment

Silk fibroin (SF), derived from Bombyx mori, is a category of fibrous protein with outstanding potential for applications in the biomedical and biotechnological fields. In spite of its many advantageous properties, the exploration of SF as a versatile nanodrug precursor for tumor therapy has still been restricted in recent years. Herein, a multifunctional SF-derived nanoplatform was facilely developed via encapsulating the photosensitizer chlorin e6 (Ce6) into MnO2-capped SF nanoparticles (NPs). SF@MnO2 nanocarriers were synthesized through a surface crystallization technique, using SF as a reductant and sacrificial template. Afterwards, Ce6 was covalently incorporated into the loose structure of the SF@MnO2 nanocarrier on the basis of adsorption to abundant peptide-binding sites. To modulate the tumor microenvironment (TME), SF@MnO2/Ce6 (SMC) NPs were capable of catalyzing the decomposition of H2O2 into O2, which can be converted into cytotoxic reactive oxygen species (ROS) during photodynamic therapy (PDT). Moreover, the MnO2 component was able to oxidize intracellular glutathione (GSH) into non-reducing glutathione disulfide (GSSG), and the consumption of GSH could significantly protect the local ROS from being reduced, which further augmented the therapeutic outcome of PDT. Via another angle, SMC NPs can produce strong hyperthermia under near-infrared (NIR) light activation, which was highly desirable for efficient photothermal therapy (PTT). Both in vitro and in vivo studies demonstrated the intense tumor inhibitory effects as a result of augmented PTT/PDT mediated by SMC NPs. We believe that this study may provide useful insights for employing SF-based nanocomposites for more medical applications in the near future.

[Targeted drug delivery system for doxorubicin based on a specific peptide and phospholipid nanoparticles]

Doxorubicin is one of the widely known and frequently used chemotherapy drugs for the treatment of various types of cancer, the use of which is difficult due to its high cardiotoxicity. Targeted drug delivery systems are being developed to reduce side effects. One of the promising components as vector molecules (ligands) are NGR-containing peptides that are affinity for the CD13 receptor, which is expressed on the surface of many tumor cells and tumor blood vessels. Previously, a method was developed for preparing a composition of doxorubicin embedded in phospholipid nanoparticles with a targeted fragment in the form of an ultrafine emulsion. The resulting composition was characterized by a small particle size (less than 40 nm) and a high degree of incorporation of doxorubicin (about 93%) into transport nanoparticles. When assessing the penetrating ability and the degree of binding to the surface of fibrosarcoma cells (HT-1080), it was shown that when the composition with the targeted fragment was added to the cells, the level of doxorubicin was almost 2 times higher than that of the liposomal form of doxorubicin, i.e. the drug in the system with the targeted peptide penetrated the cell better. At the same time, on the control line of breast adenocarcinoma cells (MCF-7), which do not express the CD13 receptor on the surface, there was not significant difference in the level of doxorubicin in the cells. The data obtained allow us to draw preliminary conclusions about the prospects of targeted delivery of doxorubicin to tumor cells when using a peptide conjugate containing an NGR motif and the further need for its comprehensive study.

Chlorin e6 embedded in phospholipid nanoparticles equipped with specific peptides: Interaction with tumor cells with different aminopeptidase N expression

A promising direction in Biopharmaceuticals is the development of specific peptide-based systems to improve drug delivery. This approach may increase tumor specificity and drug penetration into the target cell. Similar systems have been designed for several antitumor drugs. However, for photodynamic therapy drugs, such studies are not yet enough. Previously, we have developed a method of inclusion of chlorin e6 (Ce6), a photosensitizer used in photodynamic therapy, in phospholipid nanoparticles with a diameter of up to 30 nm, and reported an increase in its effectiveness in the experiments in vivo. In this work, we propose to modify a previously developed delivery system for Ce6 by the addition of cell-penetrating (R7) and/or targeting NGR peptides. The interaction of the compositions developed with HepG2 and MCF-7 tumor cells is shown. The expression of CD13 protein with affinity to NGR on the surface of these cells has been studied using flow cytometry. The expression of this protein on the HepG2 cells and its absence on MCF-7 was demonstrated. After incubation of tumor cells with the resulting Ce6 compositions, we evaluated the cellular accumulation, photoinduced, and dark cytotoxicity of the drugs. After irradiation, the highest level of cytotoxicity was observed when R7 peptide was added to the system, either alone or in combination with NGR. In addition to R7, the NGR-motif peptide increased the internalization of Ce6 in HepG2 cells without affecting its photodynamic activity. In this work we also discuss possible mechanisms of action of the cell-penetrating peptide when attached to phospholipid nanoparticles.

Laser-Assisted aPDT Protocols in Randomized Controlled Clinical Trials in Dentistry: A Systematic Review

BACKGROUND

Antimicrobial photodynamic therapy (aPDT) has been proposed as an effective alternative method for the adjunctive treatment of all classes of oral infections. The multifactorial nature of its mechanism of action correlates with various influencing factors, involving parameters concerning both the photosensitizer and the light delivery system. This study aims to critically evaluate the recorded parameters of aPDT applications that use lasers as the light source in randomized clinical trials in dentistry.

METHODS

PubMed and Cochrane search engines were used to identify human clinical trials of aPDT therapy in dentistry. After applying specific keywords, additional filters, inclusion and exclusion criteria, the initial number of 7744 articles was reduced to 38.

RESULTS

Almost one-half of the articles presented incomplete parameters, whilst the others had different protocols, even with the same photosensitizer and for the same field of application.

CONCLUSIONS

No safe recommendation for aPDT protocols can be extrapolated for clinical use. Further research investigations should be performed with clear protocols, so that standardization for their potential dental applications can be achieved.

Photosensitizer-stabilized self-assembling nanoparticles potentiate chemo/photodynamic efficacy of patient-derived melanoma

Development of injectable nanoparticles for delivery of active anticancer compounds often requires complicated schemes that involve tedious synthetic protocols and nanoformulations. In particular, clinical translation of synergistic nanoparticles that can facilitate multimodal therapies remains a considerable challenge. Herein, we describe a self-assembling, small-molecule nanosystem with unique properties, including near-infrared (NIR) light-responsive drug activation, size transformability, combinatorial synergy, and substantially reduced toxicity. Ligation of anticancer cabazitaxel (CTX) drugs via a reactive oxygen species-activatable thioketal linkage generates a dimeric TKdC prodrug, and subsequent coassembly with a photosensitizer, chlorin e6 (Ce6), forms colloidal-stable nanoassemblies (termed psTKdC NAs). Upon NIR laser irradiation, psTKdC NAs are transformed into smaller size particles and facilitate production of pharmacologically active CTX. Importantly, reactive oxygen species yielded by coassembled Ce6 can synergize with chemotherapy to achieve potent combinatorial effects. In a preclinical orthotopic model of an aggressive, human melanoma patient-derived xenograft (PDX), we show that administration of psTKdC NAs followed by laser irradiation produced durable tumor regression, with the tumors being completely eradicated in three of six PDXs. Furthermore, low systemic toxicity of this smart, photo-activatable nanotherapy was observed in animals. The new self-deliverable combinatorial system addresses essential requirements for high efficacy, safety, and translational capacity and deserves further investigation.

A Naturally Derived Carrier for Photodynamic Treatment of Squamous Cell Carcinoma: In Vitro and In Vivo Models

Photodynamic therapy (PDT) is a non-invasive treatment strategy that includes the combination of three components-a photosensitizer, a light source, and tissue oxygen. PDT can be used for the treatment of skin diseases such as squamous cell carcinoma. The photosensitizer used in this study is the naturally derived chlorophyll derivative chlorin e6 (Ce6), which was encapsulated in ultradeformable ethosomes. Singlet oxygen production by Ce6 upon laser light irradiation was not significantly affected by encapsulation into ethosomes. PDT of squamous cell carcinoma cells treated with Ce6 ethosomes triggered increased mitochondrial superoxide levels and increased caspase 3/7 activity, resulting in concentration- and light-dose-dependent cytotoxicity. Ce6 ethosomes showed good penetration into 3D squamous cell carcinoma spheroids, which upon laser light irradiation exhibited reduced size, proliferation, and viability. The PDT effect of Ce6 ethosomes was specific and showed higher cytotoxicity against squamous cell carcinoma spheroids compared to normal skin fibroblast spheroids. In addition, PDT treatment of squamous cell carcinoma xenografts grown on chorioallantoic membranes of chick eggs (CAM) exhibited reduced expression of Ki-67 proliferation marker and increased terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL) staining, indicating reduced proliferation and activation of apoptosis, respectively. The results demonstrate that Ce6-loaded ethosomes represent a convenient formulation for photodynamic treatment of squamous cell carcinoma.

Coupling Chlorin e6 to the surface of Nanoscale Gas Vesicles strongly enhance their intracellular delivery and photodynamic killing of cancer cells

Protein-based nanobubbles such as halophilic archaeabacterial gas vesicles (GVs) represent a new class of stable, homogeneous nanoparticles with acoustic properties that allow them to be visualized by ultrasound (US) waves. To design GVs as theranostic agents, we modified them to respond to light, with a view to locally generate reactive oxygen species that can kill cancer cells. Specifically, up to 60,000 photoreactive chlorin e6 (Ce6) molecules were chemically attached to lysine ε-amino groups present on the surface of each purified Halobacterium sp. NRC-1 GV. The resulting fluorescent NRC-1 Ce6-GVs have dimensions comparable to that of native GVs and were efficiently taken up by human breast [MCF-7] and human hypopharyngeal [FaDu-GFP] cancer cells as monitored by confocal microscopy and flow cytometry. When exposed to light, internalized Ce6-GVs were 200-fold more effective on a molar basis than free Ce6 at killing cells. These results demonstrate the potential of Ce6-GVs as novel and promising nanomaterials for image-guided photodynamic therapy.

[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.

Photosensitizer Chlorin e6 Internalization into Tumor Cells in Phospholipid Nanoparticles Conjugated with Peptide Containing the NGR Sequence

The possibility of increased internalization of the photosensitizer chlorin e6 in tumor cells was investigatedusing soy phosphatidylcholine nanoparticles 20-30 nm with or without attached peptide containing Asn-Gly-Arg (NGR) motif was studied. This amino acid sequence exhibits affinity to aminopeptidase N (CD13), wich is overexpressed in a number of tumor cells and vessels. Nanoparticles with chlorin e6 were prepared with added of distearoylphosphatidylcholine (DSPE) conjugated through PEG with a hexapeptide containing the NGR sequence, and then were incubated with tumor cells НерG2 and MCF-7. Chlorin e6 accumulation in СD13-negative cells (MCF-7) did not depend on the presence of peptide NGR in nanoparticles. However, for НерG2 cells a twofold increase of chlorine e6 internalization was observed as compared with the same particles without NGR. Differences in the response of these two cell lines, differed in expression of aminopeptidase N (APN), suggest the possibility of this protein using for targeted delivery. The prospectivity of usage of phospholipids nanoparticles conjugated with targeting peptide for photodynamic therapy is discussed, taking into account possible variation of APN expression, inherent for many solid tumors.