Modes of photodynamic vs. sonodynamic cytotoxicity

Design consideration of phthalocyanines as sensitizers for enhanced sono-photodynamic combinatorial therapy of cancer

Cancer remains one of the diseases with the highest incidence and mortality globally. Conventional treatment modalities have demonstrated threatening drawbacks including invasiveness, non-controllability, and development of resistance for some, including chemotherapy, radiation, and surgery. Sono-photodynamic combinatorial therapy (SPDT) has been developed as an alternative treatment modality which offers a non-invasive and controllable therapeutic approach. SPDT combines the mechanism of action of sonodynamic therapy (SDT), which uses ultrasound, and photodynamic therapy (PDT), which uses light, to activate a sensitizer and initiate cancer eradication. The use of phthalocyanines (Pcs) as sensitizers for SPDT is gaining interest owing to their ability to induce intracellular oxidative stress and initiate toxicity under SDT and PDT. This review discusses some of the structural prerequisites of Pcs which may influence their overall SPDT activities in cancer therapy.

Metal-organic framework-based advanced therapeutic tools for antimicrobial applications

The escalating concern over conventional antibiotic resistance has emphasized the urgency in developing innovative antimicrobial agents. In recent times, metal-organic frameworks (MOFs) have garnered significant attention within the realm of antimicrobial research due to their multifaceted antimicrobial attributes, including the sustained release of intrinsic or exogenous antimicrobial components, chemodynamically catalyzed generation of reactive oxygen species (ROS), and formation of photogenerated ROS. This comprehensive review provides a thorough overview of the synthetic approaches employed in the production of MOF-based materials, elucidating their underlying antimicrobial mechanisms in depth. The focal point lies in elucidating the research advancements across various antimicrobial modalities, encompassing intrinsic component release system, extraneous component release system, auto-catalytical system, and energy conversion system. Additionally, the progress of MOF-based antimicrobial materials in addressing wound infections, osteomyelitis, and periodontitis is meticulously elucidated, culminating in a summary of the challenges and potential opportunities inherent within the realm of antimicrobial applications for MOF-based materials. STATEMENT OF SIGNIFICANCE: Growing concerns about conventional antibiotic resistance emphasized the need for alternative antimicrobial solutions. Metal-organic frameworks (MOFs) have gained significant attention in antimicrobial research due to their diverse attributes like sustained antimicrobial components release, catalytic generation of reactive oxygen species (ROS), and photogenerated ROS. This review covers MOF synthesis and their antimicrobial mechanisms. It explores advancements in intrinsic and extraneous component release, auto-catalysis, and energy conversion systems. The paper also discusses MOF-based materials' progress in addressing wound infections, osteomyelitis, and periodontitis, along with existing challenges and opportunities. Given the lack of related reviews, our findings hold promise for future MOF applications in antibacterial research, making it relevant to your journal's readership.

Strategies to Reverse Hypoxic Tumor Microenvironment for Enhanced Sonodynamic Therapy

Sonodynamic therapy (SDT) has emerged as a highly effective modality for the treatment of malignant tumors owing to its powerful penetration ability, noninvasiveness, site-confined irradiation, and excellent therapeutic efficacy. However, the traditional SDT, which relies on oxygen availability, often fails to generate a satisfactory level of reactive oxygen species because of the widespread issue of hypoxia in the tumor microenvironment of solid tumors. To address this challenge, various approaches are developed to alleviate hypoxia and improve the efficiency of SDT. These strategies aim to either increase oxygen supply or prevent hypoxia exacerbation, thereby enhancing the effectiveness of SDT. In view of this, the current review provides an overview of these strategies and their underlying principles, focusing on the circulation of oxygen from consumption to external supply. The detailed research examples conducted using these strategies in combination with SDT are also discussed. Additionally, this review highlights the future prospects and challenges of the hypoxia-alleviated SDT, along with the key considerations for future clinical applications. These considerations include the development of efficient oxygen delivery systems, the accurate methods for hypoxia detection, and the exploration of combination therapies to optimize SDT outcomes.

Comparatively sonophotochemical and photochemical studies of phthalocyanines with cationic substituents on nonperipheral positions

The term sonophotodynamic therapy (SPDT) refers to a combination of sonodynamic therapy (SDT) and photodynamic therapy (PDT), in which the efficacy of the treatment is boosted by utilizing the proper amount of a sensitizer that is responsive to both light and ultrasound. Although it has been proven in photophysicochemical studies that SPDT enhances singlet oxygen production, related studies in the literature are very limited. Considering this situation, this study aims to investigate the efficacy of synthesized phthalocyanines in terms of PDT and SPDT. The singlet oxygen quantum values calculated as 0.13 for 5, 0.44 for 6, and 0.61 for 7 in photochemical (PDT) application increased to 0.18, 0.86, and 0.92, respectively, with sonophotochemical (SPDT) application. According to the results, singlet oxygen production was more efficient with SPDT. This work will add to the body of knowledge on employing the SPDT approach to increase singlet oxygen generation.

Metal-Organic Frameworks (MOF)-Assisted Sonodynamic Therapy in Anticancer Applications

Sonodynamic therapy (SDT) has emerged as a promising therapeutic modality for anticancer treatments and is becoming a cutting-edge interdisciplinary research field. This review starts with the latest developments of SDT and provides a brief comprehensive discussion on ultrasonic cavitation, sonodynamic effect, and sonosensitizers in order to popularize the basic principles and probable mechanisms of SDT. Then the recent progress of MOF-based sonosensitizers is overviewed, and the preparation methods and properties (e.g., morphology, structure, and size) of products are presented in a fundamental perspective. More importantly, many deep observations and understanding toward MOF-assisted SDT strategies were described in anticancer applications, aiming to highlight the advantages and improvements of MOF-augmented SDT and synergistic therapies. Last but not least, the review also pointed out the probable challenges and technological potential of MOF-assisted SDT for the future advance. In all, the discussions and summaries of MOF-based sonosensitizers and SDT strategies will promote the fast development of anticancer nanodrugs and biotechnologies.

Comparison of sonodynamic, photodynamic and sonophotodynamic therapy activity of fluorinated pyridine substituted silicon phthalocyanines on PC3 prostate cancer cell line

BACKGROUND

Sonophotodynamic therapy (SPDT), a combination of photodynamic therapy (PDT) and sonodynamic therapy (SDT), may offer theraputic advantage. The therapeutic effects of sonodynamic, photodynamic, and sonophotodynamic of 5-(trifluoromethyl)-2-thiopyridine substituted silicon phthalocyanine (gy3) and its quaternized derivative (gy3q) were examined in vitro on prostate cancer using PC3 cells.

METHODS

The SDT, PDT and SPDT efficiency was determined by using MTT test.Apoptosis mechanism was evaluated by HOPI staining.

RESULTS AND DISCUSSIONS

According to MTT results, the phthalocyanines decreased cell viability when compared with a control group. Also, apoptosis measurement data represents that the phthalocyanines would produce much better therapeutic outcomes compare to PDT and SDT by utilizing SPDT. Further studies should be performed to understand the effectiveness of SPDT.

Antitumor Effect of Photodynamic Therapy/Sonodynamic Therapy/Sono-Photodynamic Therapy of Chlorin e6 and Other Applications

Chlorin e6 (Ce6) has been extensively researched and developed as an antitumor therapy. Ce6 is a highly effective photosensitizer and sonosensitizer with promising future applications in photodynamic therapy, dynamic acoustic therapy, and combined acoustic and light therapy for tumors. Ce6 is also being studied for other applications in fluorescence navigation, antibacterials, and plant growth regulation. Here we review the role and research status of Ce6 in tumor therapy and the problems and challenges of its clinical application. Other biomedical effects of Ce6 are also briefly discussed. Despite the difficulties in clinical application, Ce6 has significant advantages in photodynamic therapy (PDT)/sonodynamic therapy (SDT) against cancer and offers several possibilities in clinical utility.

Antibacterial Effect of Acoustic Cavitation Promoted by Mesoporous Silicon Nanoparticles

As-prepared mesoporous silicon nanoparticles, which were synthesized by electrochemical etching of crystalline silicon wafers followed by high-energy milling in water, were explored as a sonosensitizer in aqueous media under irradiation with low-intensity ultrasound at 0.88 MHz. Due to the mixed oxide-hydride coating of the nanoparticles' surfaces, they showed both acceptable colloidal stability and sonosensitization of the acoustic cavitation. The latter was directly measured and quantified as a cavitation energy index, i.e., time integral of the magnitude of ultrasound subharmonics. The index turned out to be several times greater for nanoparticle suspensions as compared to pure water, and it depended nonmonotonically on nanoparticle concentration. In vitro tests with Lactobacillus casei revealed a dramatic drop of the bacterial viability and damage of the cells after ultrasonic irradiation with intensity of about 1 W/cm² in the presence of nanoparticles, which themselves are almost non-toxic at the studied concentrations of about 1 mg/mL. The experimental results prove that nanoparticle-sensitized cavitation bubbles nearby bacteria can cause bacterial lysis and death. The sonosensitizing properties of freshly prepared mesoporous silicon nanoparticles are beneficial for their application in mild antibacterial therapy and treatment of liquid media.

Current status and future perspective of sonodynamic therapy for cancer

There is a tremendous need for prevention and effective treatment of cancer due to the associated morbidity and mortality. In this study, we introduce sonodynamic therapy (SDT), which is expected to be a new cancer treatment modality. SDT is a promising option for minimally invasive treatment of solid tumors and comprises three different components: sonosensitizers, ultrasound, and molecular oxygen. These components are harmless individually, but in combination they generate cytotoxic reactive oxygen species (ROS). We will explore the molecular mechanism by which SDT kills cancer cells, the class of sonosensitizers, drug delivery methods, and in vitro and in vivo studies. At the same time, we will highlight clinical applications for cancer treatment. The progress of SDT research suggests that it has the potential to become an advanced field of cancer treatment in clinical application. In this article, we will focus on the mechanism of action of SDT and its application to cancer treatment, and explain key factors to aid in developing strategies for future SDT development.

Deep-Tissue Activation of Photonanomedicines: An Update and Clinical Perspectives

Simple Summary

Photodynamic therapy (PDT) is a light-activated treatment modality, which is being clinically used and further developed for a number of premalignancies, solid tumors, and disseminated cancers. Nanomedicines that facilitate PDT (photonanomedicines, PNMs) have transformed its safety, efficacy, and capacity for multifunctionality. This review focuses on the state of the art in deep-tissue activation technologies for PNMs and explores how their preclinical use can evolve towards clinical translation by harnessing current clinically available instrumentation.

Abstract

With the continued development of nanomaterials over the past two decades, specialized photonanomedicines (light-activable nanomedicines, PNMs) have evolved to become excitable by alternative energy sources that typically penetrate tissue deeper than visible light. These sources include electromagnetic radiation lying outside the visible near-infrared spectrum, high energy particles, and acoustic waves, amongst others. Various direct activation mechanisms have leveraged unique facets of specialized nanomaterials, such as upconversion, scintillation, and radiosensitization, as well as several others, in order to activate PNMs. Other indirect activation mechanisms have leveraged the effect of the interaction of deeply penetrating energy sources with tissue in order to activate proximal PNMs. These indirect mechanisms include sonoluminescence and Cerenkov radiation. Such direct and indirect deep-tissue activation has been explored extensively in the preclinical setting to facilitate deep-tissue anticancer photodynamic therapy (PDT); however, clinical translation of these approaches is yet to be explored. This review provides a summary of the state of the art in deep-tissue excitation of PNMs and explores the translatability of such excitation mechanisms towards their clinical adoption. A special emphasis is placed on how current clinical instrumentation can be repurposed to achieve deep-tissue PDT with the mechanisms discussed in this review, thereby further expediting the translation of these highly promising strategies.

Sonodynamic therapy for gliomas

INTRODUCTION

Glioma remains incurable and a life limiting disease with an urgent need for effective therapies. Sonodynamic therapy (SDT) involves systemic delivery of non-toxic chemical agents (sonosensitizers) that accumulate in tumor cells or environment and are subsequently activated by exposure to low-frequency ultrasound to become cytotoxic agents. Herein, we discuss proposed mechanisms of action of SDT and provide recommendation for future research and clinical applications of SDT for gliomas.

METHODS

Review of literature of SDT in glioma cell cultures and animal models published in Pubmed/MEDLINE before January, 2021.

RESULTS

Different porphyrin and xanthene derivatives have proven to be effective sonosensitizers. Generation of reactive oxygen species and free radicals from water pyrolysis or sonosensitizers, or physical destabilization of cell membrane, have been identified as mechanisms of SDT leading to cell death. Numerous studies across glioma cell lines using various sonosensitizers and ultrasound parameters have documented tumoricidal effects of SDT. Studies in small animal glioma xenograft models have also consistently documented that SDT is associated with improved tumor control and longer survival of animals treated with SDT while avoiding damage of surrounding brain. There are no clinical trials completed to date regarding safety and efficacy of SDT in patients harboring gliomas, but some are beginning.

CONCLUSIONS

Pre-clinical studies cell cultures and animal models indicate that SDT is a promising treatment approach for gliomas. Further studies should define optimal sonication parameters and sonosensitizers for gliomas. Clinical trials of SDT in patients harboring gliomas and other malignant brain tumors are currently underway.

K. PK, Lee J, Kim CH, You DG, Park JH. Recent advances in nanomaterial-based augmented sonodynamic therapy of cancer

This review focuses on recent advances in augmented sonodynamic therapy (SDT) using engineered nanomaterials, and the mechanism of SDT for discussing future perspectives.

Development and characteristics of novel sonosensitive liposomes for vincristine bitartrate

The aim of drug delivery is to increase therapeutic efficacy. Externally triggered drug delivery systems enable site-specific and time-controlled drug release. To achieve this goal, our strategy was based on ultrasound-triggered release of an anticancer agent from sonosensitive liposomes (SL). To realize the ultrasound-triggered drug release, a lipophilic sonosensitizer, hematoporphyrin monomethyl ether (HMME) was incorporated into the lipid bilayer of liposomes. Once irradiated by the ultrasound in tumor tissues, the sonodynamic effect generated by HMME could lead to an efficient disruption of the lipid bilayer in the SL. After encapsulating vincristine bitartrate (VIN) as the model drug, the ultrasound-triggered lipid bilayer breakdown can trigger the instant release of VIN, enabling ultrasound-controlled chemotherapy with great specificity. In the in vitro and in vivo studies, by integrating tumor-specific targeting and stimuli-responsive controlled release into one system, VIN-loaded SL showed excellent antitumor efficacy. The SL could potentially produce viable clinical strategies for improved targeting efficiency of VIN for the treatment of related cancer. More importantly, this report provides an example of controlled release by means of a novel class of ultrasound triggering system.

Self-assembled peptido-nanomicelles as an engineered formulation for synergy-enhanced combinational SDT, PDT and chemotherapy to nasopharyngeal carcinoma

A formulation of self-assembled peptido-nanomicelles has been developed for a combinational treatment of SDT, PDT and chemotherapy to nasopharyngeal carcinoma. In vitro cellular tests and in vivo mice therapy proved effective for targeted tumor growth inhibition. These merits provided a novel approach to non-invasive cancer treatments.

Micro/Nanoparticle-Augmented Sonodynamic Therapy (SDT): Breaking the Depth Shallow of Photoactivation

The fast development of photoactivation for cancer treatment provides an efficient photo-therapeutic strategy for cancer treatment, but traditional photodynamic or photothermal therapy suffers from the critical issue of low in vivo penetration depth of tissues. As a non-invasive therapeutic modality, sonodynamic therapy (SDT) can break the depth barrier of photoactivation because ultrasound has an intrinsically high tissue-penetration performance. Micro/nanoparticles can efficiently augment the SDT efficiency based on nanobiotechnology. The state-of-art of the representative achievements on micro/nanoparticle-enhanced SDT is summarized, and specific functions of micro/nanoparticles for SDT are discussed, from the different viewpoints of ultrasound medicine, material science and nanobiotechnology. Emphasis is put on the relationship of structure/composition-SDT performance of micro/nanoparticle-based sonosensitizers. Three types of micro/nanoparticle-augmented SDT are discussed, including organic and inorganic sonosensitizers and micro/nanoparticle-based but sonosensitizer-free strategies to enhance the SDT outcome. SDT-based synergistic cancer therapy augmented by micro/nanoparticles and their biosafety are also included. Some urgent critical issues and potential developments of micro/nanoparticle-augmented SDT for efficient cancer treatment are addressed. It is highly expected that micro/nanoparticle-augmented SDT will be quickly developed as a new and efficient therapeutic modality which will find practical applications in cancer treatment. At the same time, fundamental disciplines regarding materials science, chemistry, medicine and nanotechnology will be advanced.

Study of the mechanism of sonodynamic therapy in a rat glioma model

Purpose

The study reported here examined the effect of hematoporphyrin monomethyl ether (HMME)-mediated sonodynamic therapy (SDT) on C6 gliomas implanted in rat brains.

Methods

Two weeks after inoculation, glioma development was evaluated by measuring tumor volume using a 1.5 T magnetic resonance imager. Rats that had a well-developed C6 glioma (usually when the tumor diameter reached 3–5 mm) were used to test SDT, ultrasound-alone, and HMME-alone treatments. Rats both administered and not administered intravenous HMME 10 μg/mL were insonated by a 1 MHz ultrasound at a dose of 0.5 W/cm².

Results

SDT treatment could effectively inhibit the expansion of intracranial gliomas in vivo. The treatment with ultrasound alone could inhibit glioma growth within 1 week; however, 1 week later, the tumor started growing again. In contrast, the effect of SDT could last at least 2 weeks. Injection of HMME alone had no effects on inhibiting glioma growth, suggesting the sonosensitizer HMME has no antitumor effect. Both SDT and ultrasound-alone treatment could extend the survival of rats implanted with a C6 glioma. Pathological and electron microscopic examinations suggested SDT and ultrasound-alone treatment could induce glioma necrosis by way of triggering glioma-cell apoptosis, which was confirmed by immunohistological examination with cytochrome-c and caspase-3 antibodies. Most importantly, we found that the sonosensitizer HMME could enhance the ultrasound-induced antitumor effect by selectively assisting ultrasound targeting of glioma angiogenesis inhibition.

Conclusion

This study with a rat C6 glioma experimental model showed that SDT can potentially be useful in the treatment of deep-seated malignant gliomas.

The effects of Ce6-mediated sono-photodynamic therapy on cell migration, apoptosis and autophagy in mouse mammary 4T1 cell line

PURPOSE

Sono-Photodynamic therapy (SPDT) is an alternative therapy which claims to enhance the anti-cancer effects by combining sonodynamic therapy (SDT) with photodynamic therapy (PDT). In the present study, we investigated the effects of chlorin e6 (Ce6) mediated SPDT on migration, apoptosis and autophagy in mouse mammary 4T1 cancer cells, and its underlying mechanisms.

MATERIALS

Cell migration was determined by wound healing assay. Apoptosis was analyzed using annexin V-PE/7-ADD staining as well as Hoechst 33342 staining. Changes of mitochondria membrane potential (MMP) was evaluated by flow cytometry. Formation of acidic vesicular organelles (AVOs) during autophagy was observed with fluorescence microscope by MDC staining. Immunofluorescence assays were performed to detect the co-localization of LC3 and Lamp2. Western blotting was employed to analyze the activity of the apoptosis related proteins Caspase-3, PARP, Bax and Bcl-2, as well as the autophagy associated processing of LC3-I to LC3-II and Beclin-1 expression.

RESULTS

Ce6 mediated SPDT further enhanced cell migration inhibition, significantly triggered cell apoptosis, nuclear condensation and MMP drop. Cleaved Caspase-3 and PARP increased dramatically after Ce6-SPDT, accompanied by decreased Bcl-2 expression, while the expression of Bax remained stable. Additionally, AVOs formation, co-localization of LC3 and Lamp2 occurred following Ce6-SPDT and simultaneously accompanied by LC3-II processing and increased Beclin-1 expression.

CONCLUSIONS

Ce6-SPDT could enhance cell migration inhibition, and induce mitochondria-dependent apoptosis as well as autophagy in 4T1 cells.

Efficacy of chlorin e6-mediated sono-photodynamic therapy on 4T1 cells

PURPOSE

The present study aims to investigate the antitumor effect and possible mechanisms of chlorin e6 (Ce6)-mediated sono-photodynamic therapy (Ce6-SPDT) on murine 4T1 mammary cancer cells in vitro.

MATERIALS

Cellular uptake and intracellular distribution of Ce6 in 4T1 cells were detected by flow cytometry and confocal microscope. Cells after loading with 1 μg/mL Ce6 were exposed to ultrasound at 1.0 MHz for up to 1 minute with an intensity of 0.36 W/cm2 and laser light with total radiation dose of 1.2 J/cm2. Cell viability and clonogenicity were determined by MTT assay and colony formation assay. Apoptosis was analyzed by DAPI staining, Western blots were used to detect the activity of Caspase-3. DNA damage, mitochondrial membrane potential (MMP), and intracellular reactive oxygen species (ROS) of 4T1 cells were also evaluated by flow cytometry. FD500 was employed to detect changes of membrane permeability after ultrasound.

RESULTS

Ce6 rapidly entered 4T1 cells within 4 hours after it has been added and displayed a mitochondria-localization pattern. Compared with sonodynamic therapy (SDT) and photodynamic therapy (PDT) alone, the combined SPDT treatment further enhanced cell viability loss, DNA damage, and clonogenicity inhibition. DAPI staining and western blots analysis reflected that cells with apoptotic morphological characteristics and the activity of Caspase-3 were apparently increased in the combined group. Besides, SPDT caused obvious MMP loss and intracellular ROS generation at early 1 hour post treatment. Interestingly, the SPDT induced cell viability loss and cell apoptosis was greatly inhibited by pre-treatment with ROS scavenger N-acetylcysteine and Caspase inhibitor z-VAD-fmk. FD500 detection showed that ultrasound enhanced cell membrane permeability, implying much higher uptake of Ce6 might be involved in PDT therapy by pre-ultrasound treatment.

CONCLUSIONS

The findings demonstrated that Ce6-mediated SPDT enhanced the antitumor efficacy on 4T1 cells compared with SDT and PDT alone, a Caspase-dependent apoptosis and loss of MMP, generation of ROS may be involved.

Ultrasound enhances the efficacy of chlorin E6-mediated photodynamic therapy in MDA-MB-231 cells

Sono-photodynamic therapy (SPDT) is a new modality for cancer treatment. Some studies have reported enhanced tumor cytotoxicity when sonodynamic therapy (SDT) is combined with photodynamic therapy (PDT). In this study, we investigated the cytotoxic effect of SPDT-activated chlorin e6 (Ce6) on MDA-MB-231 cells. Ce6 was found to localize mainly in mitochondria, with maximal uptake within 4 h. Cell survival was estimated by MTT (3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltertrazolium bromide tetrazolium) assay 24 h after irradiation; the combined therapy enhanced cytotoxicity to a greater extent. Apoptosis was analyzed using annexin V-PE/7-ADD (7-aminoactinomycin D) staining as well as DAPI (4', 6-diamidino-2-phenylindole) staining, and the results indicated that the cells with apoptotic characteristics were significantly increased in groups given combined therapy. Rhodamine-123 staining and cytochrome c release revealed more serious damage of mitochondria after combined treatment. The generation of reactive oxygen species detected by flow cytometry was greatly increased in cells treated with the combination therapy, and the loss in cell viability could be effectively rescued with the reactive oxygen species inhibitor N-acetylcysteine. Moreover, enhancement of cell membrane permeability after ultrasound treatment was evaluated using FD-500, and it was found that the much higher uptake of Ce6 might be involved in PDT therapy with pre-treatment ultrasound. These results suggest that ultrasound enhances the cytotoxicity of Ce6-mediated PDT, possibly because of the increased intracellular Ce6 level and ROS formation by ultrasound pre-treatment.

In vitro study of low intensity ultrasound combined with different doses of PDT: Effects on C6 glioma cells

The aim of this study was to study the effects of killing C6 glioma cells induced by hematoporphyrin monomethyl ether (HMME)-mediated sonodynamic therapy combined with photodynamic therapy (SPDT). In the SPDT group, the cells were treated with sonication at an intensity of 0.5 W/cm² and a frequency of 1 MHz, followed by different doses of light irradiation. The growth inhibition rate following treatment was determined by MTT assay. The apoptotic rate was examined by a flow cytometry. Cleavage of caspase 3, 8 and 9 was investigated by immunoblotting. Reactive oxygen species (ROS) were measured by a fluorescence microplate reader. The effect of SPDT on the glioma cells was also studied in the absence or presence of various ROS scavengers. The growth inhibition rate of C6 glioma cells treated with SPDT was significantly higher compared with sonodynamic therapy (SDT) or photodynamic therapy (PDT) alone at light doses <200 J/cm². The growth inhibition rate of C6 glioma cells treated with SPDT did not rise significantly when the light dose increased to >120 J/cm². The apoptosis rate was the highest in the SPDT group, when the light dose was at 80 J/cm². A greater amount of ROS were generated in the SPDT group than in the groups treated with SDT or PDT alone. The addition of NaN₃ or mannitol resulted in a decrease in the growth inhibition rate with SPDT. In conclusion, our data indicate that SPDT powerfully kills C6 glioma cells in vitro through the synergistic effects of SDT and PDT. The pathway of PDT inducing C6 glioma cell apoptosis includes both the mitochondrial and death receptor pathways. Furthermore, ROS may play an important role in SPDT.

Use of a novel sonosensitizer in sonodynamic therapy of U251 glioma cells in vitro

The aim of the present study was to investigate the effect of ZnPcS(2)P(2)-meditated sonodynamic therapy (SDT) on U251 human glioma cells and to identify its underlying biological mechanism. The growth inhibition rate was determined by MTT assay. The apoptotic rate was examined by flow cytometry. Fine structures were observed with transmission electron microscopy (TEM). Generation of reactive oxygen species (ROS) was detected spectrophotometrically. Caspase-3, -8 and -9 expression was detected by Western blot analysis. The growth inhibition rate of U251 human glioma cells indicated that ZnPcS(2)P(2)-meditated SDT had a better growth inhibition rate of tumor cells at a concentration of 5.0 μg/ml ZnPcS(2)P(2), at a 4-h incubation time with ZnPcS(2)P(2), and at 6 h re-incubation following SDT. At 6 h after SDT, the growth inhibition rate of cells was significantly higher compared to other groups, apoptosis could be detected in SDT by flow cytometry. TEM examination revealed morphological features of apoptosis or necrosis. Furthermore, caspase-3, -8 and -9 expression following SDT was found to be increased by Western blot analysis. Finally, generation of ROS in cells was also elevated. In conclusion, ZnPcS(2)P(2)-SDT is capable of inducing U251 cell apoptosis or necrosis and has satisfying antitumor effects. The mechanism of ZnPcS(2)P(2)-meditated SDT involves ROS generation in U251 cells, which initiates subsequent apoptosis through the mitochondrial and death receptor pathways.

Sonodynamic therapy using water-dispersed TiO2-polyethylene glycol compound on glioma cells: comparison of cytotoxic mechanism with photodynamic therapy

Sonodynamic therapy is expected to be a novel therapeutic strategy for malignant gliomas. The titanium dioxide (TiO(2)) nanoparticle, a photosensitizer, can be activated by ultrasound. In this study, by using water-dispersed TiO(2) nanoparticles, an in vitro comparison was made between the photodynamic and sonodynamic damages on U251 human glioblastoma cell lines. Water-dispersed TiO(2) nanoparticles were constructed by the adsorption of chemically modified polyethylene glycole (PEG) on the TiO(2) surface (TiO(2)/PEG). To evaluate cytotoxicity, U251 monolayer cells were incubated in culture medium including 100 μg/ml of TiO(2)/PEG for 3h and subsequently irradiated by ultraviolet light (5.0 mW/cm(2)) or 1.0MHz ultrasound (1.0 W/cm(2)). Cell survival was estimated by MTT assay 24h after irradiation. In the presence of TiO(2)/PEG, the photodynamic cytotoxic effect was not observed after 20 min of an ultraviolet light exposure, while the sonodynamic cytotoxicity effect was almost proportional to the time of sonication. In addition, photodynamic cytotoxicity of TiO(2)/PEG was almost completely inhibited by radical scavenger, while suppression of the sonodynamic cytotoxic effect was not significant. Results of various fluorescent stains showed that ultrasound-treated cells lost their viability immediately after irradiation, and cell membranes were especially damaged in comparison with ultraviolet-treated cells. These findings showed a potential application of TiO(2)/PEG to sonodynamic therapy as a new treatment of malignant gliomas and suggested that the mechanism of TiO(2)/PEG mediated sonodynamic cytotoxicity differs from that of photodynamic cytotoxicity.

Cancer treatment using an optically inert Rose Bengal derivative combined with pulsed focused ultrasound

Pulsed high intensity focused ultrasound (HIFU) has been combined with a photo-insensitive Rose Bengal derivative (RB2) to provide a synergistic cytotoxicity requiring the presence of both ultrasonic cavitation and drug. In vitro tests have shown that a short treatment (less than 30 s) of pulsed HIFU with peak negative pressure >7 MPa (~27 W acoustic power at 1.4 MHz) destroys >95% of breast cancer cells MDA-MB-231 in suspension with >10 μM of the compound. Neither the pulsed HIFU nor the RB2 compound was found to have any significant impact on the viability of the cells when used alone. Introducing an antioxidant (N-acetylcysteine) reduced the effectiveness of the treatment. In vivo tests using these same cells growing as a xenograft in nu/nu mice were also done. An ultrasound contrast agent (Optison) and lower frequency (1.0 MHz) was used to help initiate cavitation at the tumor site. We were able to demonstrate tumor regression with cavitation alone, however, addition of RB2 compound injected i.v. yielded a substantial synergistic improvement.

Toxicity and Cytopathogenic Properties Toward Human Melanoma Cells of Activated Cancer Therapeutics in Zebra Fish

There is an increasing body of data showing that activated cancer therapy—the synergistic effect of “preloaded” molecules and a tuned energy source to produce cytopathogenic moieties—is a promising new modality for cancer treatment.The key activated therapies are photodynamic therapy (PDT), which involves the synergy between light and photosensitizer molecules, and ultrasound activated therapy (USAT; also referred to as sonodynamic therapy), which involves the synergy between ultrasound and sonosensitizer molecules. PDT is a well-known activated therapy with roots dating back to 1900. However, minimal data exist on USAT. One reason is the lack of suitable sonosensitizers for clinical USAT use. The authors present both LC50 toxicity and cancer cell cytotoxicity studies on 2 dual activation agents. These compounds function as both sonosensitizers and photosensitizers, and are referred to as SonneLux agents, designated SF1 and SF2. The sensitizers are derived from chlorophyll and are metal centered porphyrins known to specifically accumulate in hyperproliferating tissue. LC50 studies on both SF1 and SF2 as determined in zebra fish reveal that both are essentially nontoxic to zebra fish. In the worst case, 5% zebra fish death is noted at the maximum soluble concentration of the sensitizer. In the cytotoxicity studies, melanoma cell line WM-266-4, derived from a metastatic site of a malignant melanoma, was tested against SF1 and SF2. Both sensitizer systems showed marked efficacy in the destruction of the implanted melanoma cells. They show great promise for clinical use in the future.

Comparisons among sensitivities of different tumor cells to focused ultrasound in vitro

This study is to test the sensitivities of different tumor cells to ultrasound irradiation at the frequency of 2.2 MHz for 60 s duration, and investigate the potential mechanism underlying different sensitivities. Three murine tumor models with distinct aggressiveness (S180, H-22 and EAC) were exposed to ultrasound to evaluate their sonodynamic efficiencies, and several biological parameters such as cell membrane permeability, lipid peroxidation (LPO), ultra-structure observation, intracellular reactive oxygen species (ROS) and mitochondria membrane potential (MMP) were analyzed after exposures. The results showed that cellular responses of different cells were distinct, of interest to note, the aggressive S180 cells were much more sensitive than others, whereas EAC cells were relatively more resistant to ultrasound irradiation. The direct comparisons among different types of cells indicate that the sono-sensitization seems to depend on the physiological and chemical properties of tumor cells. Perhaps sections of cell membrane became destabilized following the initial radical attack and LPO reaction, which caused S180 cells more susceptible to mechanical stresses during sonolysis. This study provides important implications for cancer therapy.

In vitro study of haematoporphyrin monomethyl ether-mediated sonodynamic effects on C6 glioma cells

OBJECTIVES

To study the cytotoxicity induced by haematoporphyrin monomethyl ether (HMME)-mediated sonodynamic therapy (SDT) on C6 glioma cells.

METHODS

The potent photosensitizer HMME was used as the sensitizer. Rat C6 glioma cells were incubated with HMME (10 microg/mL) in the dark for 2 h and then subjected to ultrasound treatment at 1.0 MHz and 0.5 W/cm2 for 2 min. The growth inhibition rate at different time points after SDT was determined by MTT assay. The apoptotic rate and cell circle profiles were examined with flow cytometry. Fine structures were observed with transmission electron microscope (TEM). The sonodynamic effect on the glioma cells was also studied in the absence or presence of various reactive oxygen species (ROS) scavengers.

RESULTS

The growth inhibition rate of C6 glioma cells after SDT significantly increased. SDT also increased the apoptosis and proliferation rate (APR). TEM examination showed the morphological features of apoptosis or necrosis. The addition of NaN(3) showed a strong protective effect again SDT.

CONCLUSIONS

Our data indicated that SDT could kill C6 glioma cells in vitro and possibility through induction of apoptosis and necrosis. Singlet oxygen ((1)O2) may play an important role in SDT.

Adventures in photodynamic therapy: 1976-2008

While the concept of photodynamic therapy dates from 1900, and there have been periodic re-discoveries, the clinical era really began with the studies by Dougherty and associates in the early 1970s. This report relates my encounter with the field of PDT, along with experimental approaches to the elucidation of pertinent phototoxic mechanisms.

Mechanism of Porphyrin-Induced Sonodynamic Effect: Possible Role of Hyperthermia

The biological effects of ultrasound have been investigated vigorously for various applications including the thermal coagulation of tissues, the opening of tight junctions, and localized gene or drug introduction. The synergistic cell killing effect of ultrasound and porphyrin derivatives, the so-called sonodynamic effect, holds promise for cancer treatment. Although several models to explain the sonodynamic effect have been proposed, its exact mechanism, especially in vivo, remains unknown. We examined the effect of a porphyrin derivative, protoporphyrin IX, on ultrasound-induced killing of HeLa cells. In some experiments, the intracellular protoporphyrin IX concentration was increased by 5-aminolevulinic acid treatment of the cells. Although extracellular protoporphyrin IX showed an enhanced cell killing effect by microbubble-enhanced ultrasound, intracellular protoporphyrin IX did not. On the other hand, intracellular protoporphyrin IX enhanced the cell killing effect of hyperthermia, which can be produced by ultrasound exposure, in a moderately acidic environment (pH 6.6). Because porphyrin derivatives are generally imported into the intracellular component in vivo, our results suggest that hyperthermia caused by ultrasound may play an important role in the sonodynamic effect induced by porphyrin derivatives.

Sonodynamic therapy--a review of the synergistic effects of drugs and ultrasound

Sonodynamic therapy, the ultrasound dependent enhancement of cytotoxic activities of certain compounds (sonosensitizers) in studies with cells in vitro and in tumor bearing animals, is reviewed. The attractive features of this modality for cancer treatment emerges from the ability to focus the ultrasound energy on malignancy sites buried deep in tissues and to locally activate a preloaded sonosensitizer. Possible mechanisms of sonodynamic therapy include generation of sonosensitizer derived radicals which initiate chain peroxidation of membrane lipids via peroxyl and/or alkoxyl radicals, the physical destabilization of the cell membrane by the sonosensitizer thereby rendering the cell more susceptible to shear forces or ultrasound enhanced drug transport across the cell membrane (sonoporation). Evidence against the role of singlet oxygen in sonodynamic therapy is discussed. The mechanism of sonodynamic therapy is probably not governed by a universal mechanism, but may be influenced by multiple factors including the nature of the biological model, the sonosensitizer and the ultrasound parameters. The current review emphasizes the effect of ultrasound induced free radicals in sonodynamic therapy.

Combination effect of photodynamic and sonodynamic therapy on experimental skin squamous cell carcinoma in C3H/HeN mice

We studied a combination of photodynamic therapy (PDT) and sonodynamic therapy (SDT) for improving tumoricidal effects in a transplantable mouse squamous cell carcinoma (SCC) model. Two sensitizers were utilized: the pheophorbide-a derivative PH-1126, which is a newly developed photosensitizer, and the gallium porphyrin analogue ATX-70, a commonly used sonosensitizer. Mice were injected with either PH-1126 or ATX-70 i.p. at doses of 5 or 10 mg/kg.bw. At 24 (ATX-70) or 36 hr (PH-1126) (time of optimum drug concentration in the tumor) after injection, SCCs underwent laser light irradiation (88 J/cm2 of 575 nm for ATX-70; 44J/cm2 of 650 nm for PH-1126) (PDT), ultrasound irradiation (0.51 W/cm2 at 1.0 MHz for 10 minutes) (SDT), or a combination of the two treatments. The combination of PDT and SDT using either PH-1126 or ATX-70 as a sensitizer resulted in significantly improved inhibition of tumor growth (92-98%) (additive effect) as compared to either single treatment (27-77%). The combination using PH-1126 resulted in 25% of the treated mice being tumor free at 20 days after treatment. Moreover, the median survival period (from irradiation to death) of PDT + SDT-treated mice (> 120 days) was significantly greater than that in single treatment groups (77-95 days). Histological changes revealed that combination therapy could induce tumor necrosis 2-3 times as deep as in either of the single modalities. The combination of PDT and SDT could be very useful for treatment of non-superficial or nodular tumors.

The biology of photodynamic therapy

The subcellular, cellular and tissue/tumour interactions with non-toxic photosensitizing chemicals plus non-thermal visible light (photodynamic therapy (PDT) are reviewed. The extent to which endothelium/vasculature is the primary target is discussed, and the biochemical opportunities for manipulating outcome highlighted. The nature of tumour destruction by PDT lends itself to imaging outcome by MRI and PET.

Effects of sonodynamic and photodynamic treatment on cellular thiol levels

Exposure of murine leukemia L1210 cells to ultrasound in vitro resulted in cell fragmentation; cells which survived this treatment were 100% viable and showed a transient decrease in intracellular thiol pools (expressed as glutathione equivalents). Depletion of thiol pools became progressively greater with increasing exposure of cells to ultrasound; this was not associated with leakage of thiols into the medium. Biochemically elevating glutathione levels or sonication in the presence of the anti-oxidant trolox offered only a minor degree of protection against sonotoxicity. Photodynamic therapy also resulted in depletion of intracellular thiol levels, and loss of cell viability. In the presence of trolox, both effects were reversed, although elevation of intracellular thiol levels did not protect cell from phototoxicity.