Design of Pluronic-Based Formulation for Enhanced Redaporfin-Photodynamic Therapy against Pigmented Melanoma

Poloxamer-based drug delivery systems: Frontiers for treatment of solid tumors

Pluronics or poloxamers are a type of triblock copolymer. These non-ionic molecules consist of a hydrophobic block embedded in two hydrophilic parts. Pluronics have become favorite materials for use in the field of biomedical research due to having favorable physicochemical and biological properties such as amphiphilicity, solubility in ionic and non-ionic solutions, biocompatibility, biodegradability, self-assembly and low toxicity. The scope of these applications can vary from tissue engineering to drug delivery. One of the important uses of pluronics is to deliver drugs to various cancer cells. Herein we first provide an overview on variety of ploronic biomaterials. And then intensively evaluate their potential as drug delivery systems (DDSs) for treatment of solid tumors with special focus on breast cancers. After explaining the pros and cons of pluronics, the current status in clinical settings and future prospects are highlighted.

Pyrobacteriopheophorbide-a derivatives possessing various hydrophilic esterifying groups at the C17-propionate residues for photodynamic therapy

Aiming at the application to photodynamic therapy, natural bacteriochlorophyll-a was converted to chemically stable free-base derivatives possessing different kinds of hydrophilic C17-propionate residues. These semi-synthetic bacteriochlorins were found to have self-assembling ability in an aqueous environment and formed stable J-type aggregates in a cell culture medium containing 0.2% DMSO. The electronic absorption spectra of all the sensitizers showed Qy absorption maxima at 754 nm in DMSO as their monomeric states, while a drastic shift of the red-most bands to ca. 880 nm was observed in the aqueous medium. The circular dichroism spectra in the medium showed much intense signals compared to those measured in DMSO, supporting the formation of well-ordered supramolecular structures. By introducing hydrophilic side chains, the bacteriochlorin sensitizers could be dispersed in the aqueous medium as their J-aggregates without the use of any surfactants. Cellular uptake efficiencies as well as photodynamic activities were evaluated using human cervical adenocarcinoma HeLa cells. Among the 11 photosensitizers investigated, the best result was obtained for a charged derivative possessing trimethylammonium terminal (17-CH2CH2COOCH2CH2N+(CH3)3I-) and photocytotoxicity of EC50 = 0.09 μM was achieved by far-red light illumination of 35 J/cm2 from an LED panel (730 nm).

Cathepsin B Activatable Fluorescent Probe for Antitumor Efficiency Feedback: Attempt To Detect Certain Apoptotic Cells

As many treatments kill tumor cells by inducing apoptosis, fluorescent probes that can detect apoptosis are crucial for effective feedback regarding tumor therapy outcomes (in particular, activatable probes for better imaging). Cathepsins are enzymes that are released from lysosomes into the cytoplasm during lysosomal membrane permeabilization-induced apoptosis of many tumor cells, making them potential biomarkers of apoptotic cells. Despite their potential, to the best of our knowledge, no cathepsin-activatable fluorescent probes have been reported for this purpose. To fill this gap, we designed a cathepsin B (CTSB)-activatable fluorescent probe, A-DCO, which can distinguish tumor cells from normal cells in the free state and give feedback of enhanced fluorescence signal under drug stimulation when encapsulated into nanoparticles (NPs), enabling the evaluation of treatment efficacy. As a proof of concept, A-DCO NPs were employed rather than Annexin-V/PI double staining to detect apoptotic 4T1 and MCF-7 tumor cells via flow cytometry. In vivo experiments demonstrated that A-DCO NPs can rapidly detect apoptotic 4T1 tumor cells and are quickly metabolized after imaging, achieving timely, accurate, and safe feedback about tumor treatment effectiveness. The study offers a new tool for detecting the apoptosis of certain tumor cells and provides inspiration and direction for fluorescent probe design in the future.

NIR-activated multifunctional agents for the combined application in cancer imaging and therapy

Anticancer therapies that combine both diagnostic and therapeutic capabilities hold significant promise for enhancing treatment efficacy and patient outcomes. Among these, agents responsive to near-infrared (NIR) photons are of particular interest due to their negligible toxicity and multifunctionality. These compounds are not only effective in photodynamic therapy (PDT), but also serve as contrast agents in various imaging modalities, including fluorescence and photoacoustic imaging. In this review, we explore the photophysical and photochemical properties of NIR-activated porphyrin, cyanine, and phthalocyanines derivatives as well as aggregation-induced emission compounds, highlighting their application in synergistic detection, diagnosis, and therapy. Special attention is given to the design and optimization of these agents to achieve high photostability, efficient NIR absorption, and significant yields of fluorescence, heat, or reactive oxygen species (ROS) generation depending on the application. Additionally, we discuss the incorporation of these compounds into nanocarriers to enhance their solubility, stability, and target specificity. Such nanoparticle-based systems exhibit improved pharmacokinetics and pharmacodynamics, facilitating more effective tumor targeting and broadening the application range to photoacoustic imaging and photothermal therapy. Furthermore, we summarize the application of these NIR-responsive agents in multimodal imaging techniques, which combine the advantages of fluorescence and photoacoustic imaging to provide comprehensive diagnostic information. Finally, we address the current challenges and limitations of photodiagnosis and phototherapy and highlight some critical barriers to their clinical implementation. These include issues related to their phototoxicity, limited tissue penetration, and potential off-target effects. The review concludes by highlighting future research directions aimed at overcoming these obstacles, with a focus on the development of next-generation agents and platforms that offer enhanced therapeutic efficacy and imaging capabilities in the field of cancer treatment.

Tetramethyl Cucurbit[6]uril-Porphyrin Supramolecular Polymer Enhances Photosensitization

Porphyrins serve as photosensitizers (PS) in the realm of cancer photodynamic therapy (PDT). Upon excitation by laser light, porphyrins are capable of converting molecular oxygen into highly cytotoxic singlet oxygen (1O2). However, the rigid π-conjugated structure of porphyrins frequently results in the formation of aggregates in aqueous solutions, which leads to the self-quenching of the excited state. Cucurbit[n]urils exhibit the capacity to stably bind with porphyrins via host-guest interactions, effectively inhibiting their aggregation and potentially enhancing the therapeutic efficacy of PDT. In this study, water-soluble tetramethyl cucurbit[6]uril (TMeQ[6]) was selected as the host, while four propionic acid group-appended porphyrin cationic (TPPOR) was utilized as guests to construct a supramolecular photosensitizer (TPPOR-2TMeQ[6]) in a molar ratio of 2:1. Further experimental findings demonstrate that the presence of TMeQ[6] inhibits the aggregation of TPPOR through non-covalent interactions. This inhibition reduces the energy difference between the excited singlet and triplet states, thereby enhancing the conversion efficiency of 1O2. Moreover, TPPOR-2TMeQ[6] exhibits favorable biocompatibility and minimal dark toxicity against breast cancer cells (4T1). Upon intracellular excitation, the levels of reactive oxygen species (ROS) significantly increase, inducing oxidative stress in 4T1 cells and leading to apoptosis. Consequently, the findings of this study suggest that the enhanced photosensitization achieved through this supramolecular approach is likely to promote the anticancer therapeutic effects of PDT, thereby broadening the application prospects of porphyrins within PDT systems.

Synergistic Therapy of Melanoma by Co-Delivery of Dacarbazine and Ferroptosis-Inducing Ursolic Acid Using Biomimetic Nanoparticles

Melanoma is one of the most aggressive types of cancer and is prone to metastasis, making current clinical treatment quite difficult. The usage of the first-line medication dacarbazine (DTIC) for melanoma is limited due to harsh side effects, limited water solubility, and a short half-life. To tackle these disadvantages, polylactic acid-hydroxyacetic acid copolymer nanoparticles (NPs) loaded with dacarbazine and ursolic acid (NPs) were fabricated, which were further encapsulated with a red blood cell membrane (RNPs). MTT, apoptosis assay, wound healing assay, colony formation assay, and immunohistochemistry were used to assess the antitumor effect of NPs and RNPs. Ferroptosis evaluation was implemented using GSH detection and the malondialdehyde assay. We found that RNPs exhibited stability and biosafety in vitro and in vivo and achieved superior anticancer ability against xenograft tumors compared with single agents and NPs, which indicated the synergistic and biomimetic efficacy. Furthermore, ferroptotic activity was observed in RNPs-treated tumor cells, and ferroptosis inhibition could partially rescue melanoma cells from RNPs-induced cell death. Collectively, this study evaluated the potential of RNPs as a novel biomimetic nanomedicine for synergistic melanoma therapy by eliciting ferroptosis in tumor cells with both anticancer activity and biosafety.

Better in the Near Infrared: Sulfonamide Perfluorinated-Phenyl Photosensitizers for Improved Simultaneous Targeted Photodynamic Therapy and Real-Time Fluorescence Imaging

Tetraphenyloporphyrin derivatives are a useful scaffold for developing new pharmaceuticals for photodynamic therapy (PDT) and the photodiagnosis (PD) of cancer. We synthesized new sulfonamide fluorinated porphyrin derivatives and investigated their potential as photosensitizers and real-time bioimaging agents for cancer. We found that 5,10,15,20-tetrakis-[2',3',5',6'-tetrafluoro-4'-methanesulfamidyl)phenyl]bacteriochlorin (F4BMet) has intense absorption and fluorescence in the near-infrared, efficiently generates singlet oxygen and hydroxyl radicals, has low toxicity in the dark, and high phototoxicity. We increased its bioavailability with encapsulation in Pluronic-based micelles, which also improved the photodynamic effect. F4BMet exhibits pH-dependent properties (lower pH promoted its aggregation), and a GlyGly buffer was used to effectively solubilize the compound. In vitro findings with 2D cell culture were complemented with human-induced pluripotent stem cell (hiPSC)-derived organoids. F4BMet in P123 micelles showed enhanced efficacy compared to F4BMet in the GlyGly formulation. F4BMet was further evaluated in real-time bioimaging and PDT of BALB/c mice bearing CT26 tumors. After i.v. injection, the photosensitizer was visible in the tumor area 3 h after injection. The most successful therapeutic approach proved to be tumor-targeted PDT using P123-encapsulated F4BMet illuminated 24 h after administration with a light dose of 42 J/cm2, which led to a 30% long-term cure rate.

Synthesis, Photo-Characterizations, and Pre-Clinical Studies on Advanced Cellular and Animal Models of Zinc(II) and Platinum(II) Sulfonyl-Substituted Phthalocyanines for Enhanced Vascular-Targeted Photodynamic Therapy

Two phthalocyanine derivatives tetra-peripherally substituted with tert-butylsulfonyl groups and coordinating either zinc(II) or platinum(II) ions have been synthesized and subsequently investigated in terms of their optical and photochemical properties, as well as biological activity in cellular, tissue-engineered, and animal models. Our research has revealed that both synthesized phthalocyanines are effective generators of reactive oxygen species (ROS). PtSO2tBu demonstrated an outstanding ability to generate singlet oxygen (ΦΔ = 0.87-0.99), while ZnSO2tBu in addition to 1O2 (ΦΔ = 0.45-0.48) generated efficiently other ROS, in particular ·OH. Considering future biomedical applications, the affinity of the tested phthalocyanines for biological membranes (partition coefficient; log Pow) and their primary interaction with serum albumin were also determined. To facilitate their biological administration, a water-dispersible formulation of these phthalocyanines was developed using Pluronic triblock copolymers to prevent self-aggregation and improve their delivery to cancer cells and tissues. The results showed a significant increase in cellular uptake and phototoxicity when phthalocyanines were incorporated into the customizable polymeric micelles. Moreover, the improved distribution in the body and photodynamic efficacy of the encapsulated phthalocyanines were investigated in hiPSC-delivered organoids and BALB/c mice bearing CT26 tumors. Both photosensitizers exhibit strong antitumor activity. Notably, vascular-targeted photodynamic therapy (V-PDT) led to complete tumor eradication in 84% of ZnSO2tBu and 100% of PtSO2tBu-treated mice, and no recurrence has so far been observed for up to five months after treatment. In the case of PtSO2tBu, the effect was significantly stronger, offering a wider range of light doses suitable for achieving effective PDT.

Photodynamic Therapy in the Treatment of Cancer-The Selection of Synthetic Photosensitizers

Photodynamic therapy (PDT) is a promising cancer treatment method that uses photosensitizing (PS) compounds to selectively destroy tumor cells using laser light. This review discusses the main advantages of PDT, such as its low invasiveness, minimal systemic toxicity and low risk of complications. Special attention is paid to photosensitizers obtained by chemical synthesis. Three generations of photosensitizers are presented, starting with the first, based on porphyrins, through the second generation, including modified porphyrins, chlorins, 5-aminolevulinic acid (ALA) and its derivative hexyl aminolevulinate (HAL), to the third generation, which is based on the use of nanotechnology to increase the selectivity of therapy. In addition, current research trends are highlighted, including the search for new photosensitizers that can overcome the limitations of existing therapies, such as heavy-atom-free nonporphyrinoid photosensitizers, antibody-drug conjugates (ADCs) or photosensitizers with a near-infrared (NIR) absorption peak. Finally, the prospects for the development of PDTs are presented, taking into account advances in nanotechnology and biomedical engineering. The references include both older and newer works. In many cases, when writing about a given group of first- or second-generation photosensitizers, older publications are used because the properties of the compounds described therein have not changed over the years. Moreover, older articles provide information that serves as an introduction to a given group of drugs.

The fusion of light and immunity: Advancements in photoimmunotherapy for melanoma

Metastatic melanoma is an aggressive skin cancer with high mortality and recurrence rates. Despite the clinical success of recent immunotherapy approaches, prevailing resistance rates necessitate the continued development of novel therapeutic options. Photoimmunotherapy (PIT) is emerging as a promising immunotherapy strategy that uses photodynamic therapy (PDT) to unleash systemic immune responses against tumor sites while maintaining the superior tumor-specificity and minimally invasive nature of traditional PDT. In this review, we discuss recent advances in PIT and strategies for the management of melanoma using PIT. PIT can strongly induce immunogenic cell death, inviting the concomitant application of immune checkpoint blockade or adoptive cell therapies. PIT can also be leveraged to selectively remove the suppressive immune populations associated with immunotherapy resistance. The modular nature of PIT therapy design combined with the potential for patient-specific antigen selection or drug co-delivery makes PIT an alluring option for future personalized melanoma care.

Anti-Melanoma Activity of Single Intratumoral Injection of ZnPc Micelles Mixed With in situ Gel in B16 Bearing Mouse

Photodynamic therapy (PDT) is a potential treatment strategy for melanoma. As a second-generation photosensitizer, Zinc phthalocyanine (ZnPc) has many advantages for anti-tumor PDTs, such as strong absorption in the red and near infrared regions, high photo and chemical stability, etc. However, ZnPc has a poor water solubility and is apt to aggregate due to the π-π interaction between molecules, which limits its applications. In this study, various solvents and surfactants were screened for dissolving ZnPc and preparing ZnPc@SDC-TPGS micelle and thermosensitive in situ gel. After the cytotoxic effects of thermosensitive gels on PDT were tested, the antitumor effects on PDT of them in mice by intratumoral injection were evaluated, including body weight, and tumor weight, volume and morphology. The cell death pathway and the relationship of reactive oxygen species yield with apoptotic rate of tumor cells induced by ZnPc in situ gel were investigated. The results were that N-methyl-pyrrolidone (NMP) mixed with 2 % SDC and aqueous solution containing 2 % TPGS and 2 % SDC were used to synthesize ZnPc@SDC-TPGS micelle and the thermosensitive in situ gel. The cytotoxic effects of thermosensitive gels showed good tumor suppression of ZnPc@SDC-TPGS in situ gel and no toxicity of the blank gel. Intratumoral injection in situ gel containing 3 µg ZnPc under irradiation demonstrated good tumor inhibition in mice with melanoma. Apoptosis has been established as the primary pathway of cell death, and the production of reactive oxygen species (ROS) plays a crucial role in cellular apoptosis induced by ZnPc@SDC-TPGS in situ gel. In conclusion, the intratumoral injection of ZnPc@SDC-TPGS thermosensitive in situ gel provides a promising local treatment option for melanoma.

Antitumor Immunity Mediated by Photodynamic Therapy Using Injectable Chitosan Hydrogels for Intratumoral and Sustained Drug Delivery

Photodynamic therapy (PDT) is an anticancer therapy with proven efficacy; however, its application is often limited by prolonged skin photosensitivity and solubility issues associated with the phototherapeutic agents. Injectable hydrogels which can effectively provide intratumoral delivery of photosensitizers with sustained release are attracting increased interest for photodynamic cancer therapies. However, most of the hydrogels for PDT applications are based on systems with high complexity, and often, preclinical validation is not provided. Herein, we provide a simple and reliable pH-sensitive hydrogel formulation that presents appropriate rheological properties for intratumoral injection. For this, Temoporfin (m-THPC), which is one of the most potent clinical photosensitizers, was chemically modified to introduce functional groups that act as cross-linkers in the formation of chitosan-based hydrogels. The introduction of -COOH groups resulted in a water-soluble derivative, named PS2, that was the most promising candidate. Although PS2 was not internalized by the target cells, its extracellular activation caused effective damage to the cancer cells, which was likely mediated by lipid peroxidation. The injection of the hydrogel containing PS2 in the tumors was monitored by high-frequency ultrasounds and in vivo fluorescence imaging which confirmed the sustained release of PS2 for at least 72 h. Following local administration, light exposure was conducted one (single irradiation protocol) or three (multiple irradiation protocols) times. The latter delivered the best therapeutic outcomes, which included complete tumor regression and systemic anticancer immune responses. Immunological memory was induced as ∼75% of the mice cured with our strategy rejected a second rechallenge with live cancer cells. Additionally, the failure of PDT to treat immunocompromised mice bearing tumors reinforces the relevance of the host immune system. Finally, our strategy promotes anticancer immune responses that lead to the abscopal protection against distant metastases.

Advantages of Long-Wavelength Photosensitizer meso-Tetra(3-pyridyl) Bacteriochlorin in the Therapy of Bulky Tumors

This research presents a novel synthetic photosensitizer for the photodynamic therapy (PDT) of malignant tumors: meso-tetra(3-pyridyl) bacteriochlorin, which absorbs at 747 nm (in the long-wavelength region of the spectrum) and is stable when stored in the dark. H2Py4BC demonstrates pronounced photoinduced activity in vitro against tumor cells of various geneses (IC50 varies from 21 to 68 nM for HEp2, EJ, S37, CT26, and LLC cultured cells) and in vivo provides pronounced antitumor efficacy in the treatment of mice bearing small or large S37, Colo26, or LLC metastatic tumors, as well as in the treatment of rats bearing RS-1 liver cholangioma. As a result, total regression of primary tumor nodules and cure of 40 to 100% of the animals was proven by the experiment criteria, MRI, and histological analysis. Meso-tetra(3-pyridyl) bacteriochlorin quickly penetrates and accumulates in the tumor tissue and internal organs of mice, and after 24 h, 80% of the dye is excreted from the skin in addition to 87-92% from the liver, kidneys, and spleen.

Block Copolymer Encapsulation of Disarib, an Inhibitor of BCL2 for Improved Chemotherapeutic Potential

A chemical inhibitor of antiapoptotic protein, BCL2, known as Disarib, suffers poor solubility in aqueous environments; thereby limiting its potential as a chemotherapeutic agent. To overcome this limitation and enhance the therapeutic efficacy of Disarib, we have employed the encapsulation of this small molecule inhibitor within P123 copolymer matrix. Micelles were synthesized using a thin-film hydration technique, and a comprehensive analysis was undertaken to evaluate the resulting micelle properties, including morphology, particle size, intermolecular interactions, encapsulation efficiency, and in vitro release characteristics. This assessment utilized various physicochemical techniques including UV spectroscopy, FTIR spectroscopy, dynamic light scattering (DLS), transmission electron microscopy (TEM), and small-angle X-ray scattering (SAXS). Disarib-loaded P123 micelle formulation denoted as P123D exhibited a well-defined particle size of approximately 29.2 nm spherical core-shell morphology. Our investigations revealed a notable encapsulation efficiency of 75%, and we observed a biphasic release pattern for the encapsulated Disarib. Furthermore, our cytotoxicity assessment of P123D micelles against mouse breast adenocarcinoma, mouse lymphoma, and human leukemic cell lines showed 40-45% increase in cytotoxicity compared with the administration of Disarib alone in the breast adenocarcinoma cell line. Enhancement in the cytotoxicity of P123D was found to be higher or limited; however, it is important to observe that the encapsulation method significantly enhanced the aqueous solubility of Disarib as it has the best solubility in dimethyl sulfoxide (DMSO) in the unencapsulated state.

Folate Functionalized and Evodiamine-Loaded Pluronic Nanomicelles for Augmented Cervical Cancer Cell Killing

Evodiamine (Evo) is a natural, biologically active plant alkaloid with wide range of pharmacological activities. In the present study Evo-loaded folate-conjugated Pluronic F108 nano-micelles (ENM) is synthesized to enhance the therapeutic efficacy of Evo against cervical cancer. ENM are synthesized, physicochemically characterized and in vitro anticancer activity is performed. The study demonstrates that ENM have nanoscale size (50.33 ± 3.09 nm), monodispersity of 0.122 ± 0.072, with high drug encapsulation efficiency (71.30 ± 3.76%) and controlled drug release at the tumor microenvironment. ENM showed dose-dependent and time-dependent cytotoxicity against HeLa human cervical cancer cells. The results of in vitro anticancer studies demonstrated that ENM have significant anticancer effects and greatly induce apoptosis as compared to pure Evo. The cellular uptake study suggests that increased anticancer activity of ENM is due to the improved intracellular delivery of Evo through overexpressed folate receptors. Overall, the designed ENM can be a potential targeted delivery system for hydrophobic anticancer bioactive compound like Evo.

Photodynamic therapy changes tumour immunogenicity and promotes immune-checkpoint blockade response, particularly when combined with micromechanical priming

Photodynamic therapy (PDT) with redaporfin stimulates colon carcinoma (CT26), breast (4T1) and melanoma (B16F10) cells to display high levels of CD80 molecules on their surfaces. CD80 overexpression amplifies immunogenicity because it increases same cell (cis) CD80:PD-L1 interactions, which (i) disrupt binding of T-cells PD-1 inhibitory receptors with their ligands (PD-L1) in tumour cells, and (ii) inhibit CTLA-4 inhibitory receptors binding to CD80 in tumour cells. In some cancer cells, redaporfin-PDT also increases CTLA-4 and PD-L1 expressions and virtuous combinations between PDT and immune-checkpoint blockers (ICB) depend on CD80/PD-L1 or CD80/CTLA-4 tumour overexpression ratios post-PDT. This was confirmed using anti-CTLA-4 + PDT combinations to increase survival of mice bearing CT26 tumours, and to regress lung metastases observed with bioluminescence in mice with orthotopic 4T1 tumours. However, the primary 4T1 responded poorly to treatments. Photoacoustic imaging revealed low infiltration of redaporfin in the tumour. Priming the primary tumour with high-intensity (~ 60 bar) photoacoustic waves generated with nanosecond-pulsed lasers and light-to-pressure transducers improved the response of 4T1 tumours to PDT. Penetration-resistant tumours require a combination of approaches to respond to treatments: tumour priming to facilitate drug infiltration, PDT for a strong local effect and a change in immunogenicity, and immunotherapy for a systemic effect.

Trial watch: an update of clinical advances in photodynamic therapy and its immunoadjuvant properties for cancer treatment

Photodynamic therapy (PDT) is a medical treatment used to target solid tumors, where the administration of a photosensitizing agent and light generate reactive oxygen species (ROS), thus resulting in strong oxidative stress that selectively damages the illuminated tissues. Several preclinical studies have demonstrated that PDT can prime the immune system to recognize and attack cancer cells throughout the body. However, there is still limited evidence of PDT-mediated anti-tumor immunity in clinical settings. In the last decade, several clinical trials on PDT for cancer treatment have been initiated, indicating that significant efforts are being made to improve current PDT protocols. However, most of these studies disregarded the immunological dimension of PDT. The immunomodulatory properties of PDT can be combined with standard therapy and/or emerging immunotherapies, such as immune checkpoint blockers (ICBs), to achieve better disease control. Combining PDT with immunotherapy has shown synergistic effects in some preclinical models. However, the value of this combination in patients is still unknown, as the first clinical trials evaluating the combination of PDT with ICBs are just being initiated. Overall, this Trial Watch provides a summary of recent clinical information on the immunomodulatory properties of PDT and ongoing clinical trials using PDT to treat cancer patients. It also discusses the future perspectives of PDT for oncological indications.

RAFT Synthesis and Characterization of Poly(Butyl-co-2-(N,N-Dimethylamino)Ethyl Acrylates)-block-Poly(Polyethylene Glycol Monomethyl Ether Acrylate) as a Photosensitizer Carrier for Photodynamic Therapy

Polymer micelles are promising drug delivery systems for highly hydrophobic photosensitizers in photodynamic therapy (PDT) applications. We previously developed pH-responsive polymer micelles consisting of poly(styrene-co-2-(N,N-dimethylamino)ethyl acrylate)-block-poly(polyethylene glycol monomethyl ether acrylate) (P(St-co-DMAEA)-b-PPEGA) for zinc phthalocyanine (ZnPc) delivery. In this study, poly(butyl-co-2-(N,N-dimethylamino)ethyl acrylates)-block-poly(polyethylene glycol monomethyl ether acrylate) (P(BA-co-DMAEA)-b-PPEGA) was synthesized via reversible addition and fragmentation chain transfer (RAFT) polymerization to explore the role of neutral hydrophobic units in photosensitizer delivery. The composition of DMAEA units in P(BA-co-DMAEA) was adjusted to 0.46, which is comparable to that of P(St-co-DMAEA)-b-PPEGA. The size distribution of the P(BA-co-DMAEA)-b-PPEGA micelles changed when the pH decreased from 7.4 to 5.0, indicating their pH-responsive ability. The photosensitizers, 5,10,15,20-tetrakis(pentafluorophenyl)chlorin (TFPC), 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin (TFPP), protoporphyrin IX (PPIX), and ZnPc were examined as payloads for the P(BA-co-DMAEA)-b-PPEGA micelles. The encapsulation efficiency depended on the nature of the photosensitizer. TFPC-loaded P(BA-co-DMAEA)-b-PPEGA micelles exhibited higher photocytotoxicity than free TFPC in the MNNG-induced mutant of the rat murine RGM-1 gastric epithelial cell line (RGK-1), indicating their superiority for photosensitizer delivery. ZnPc-loaded P(BA-co-DMAEA)-b-PPEGA micelles also exhibited superior photocytotoxicity compared to free ZnPc. However, their photocytotoxicity was lower than that of P(St-co-DMAEA)-b-PPEGA. Therefore, neutral hydrophobic units, as well as pH-responsive units, must be designed for the encapsulation of photosensitizers.

Redaporfin Development for Photodynamic Therapy and its Combination with Glycolysis Inhibitors

Photodynamic therapy (PDT) remains an underutilized treatment modality in oncology. Many efforts have been dedicated to the development of better photosensitizers, better formulations and delivery methods, rigorous planning of light dose distribution in tissues, mechanistic insight, improvement of treatment protocols and combinations with other therapeutic agents. Hopefully, progress in all these fields will eventually expand the use of PDT. Here we offer a brief review of our own contribution to the development of a photosensitizer for PDT - redaporfin - currently in Phase II clinical trials, and present data on its combination with two glycolysis inhibitors: 2-deoxyglucose and 3-bromopyruvate. We show that 3-bromopyruvate is more cytotoxic to a carcinoma cell line (CT26) than to a normal fibroblast (3T3) cell line, and that this selectivity is maintained in the in vitro combination with redaporfin-PDT. This combination was investigated in BALB/c mice with large subcutaneous CT26 tumors and it is shown that the cure rate in the combination is higher (33% cures) than in PDT (11% cures) or in 3-bromopyruvate (no cures) alone. The combination of redaporfin-PDT with 3-bromopyruvate illustrates the potential of combination therapies and how PDT benefits can be enhanced by systemic drugs with complementary targets.

Development of Biotechnological Photosensitizers for Photodynamic Therapy: Cancer Research and Treatment-From Benchtop to Clinical Practice

Photodynamic therapy (PDT) is a noninvasive therapeutic approach that has been applied in studies for the treatment of various diseases. In this context, PDT has been suggested as a new therapy or adjuvant therapy to traditional cancer therapy. The mode of action of PDT consists of the generation of singlet oxygen (¹O₂) and reactive oxygen species (ROS) through the administration of a compound called photosensitizer (PS), a light source, and molecular oxygen (³O₂). This combination generates controlled photochemical reactions (photodynamic mechanisms) that produce ROS, such as singlet oxygen (¹O₂), which can induce apoptosis and/or cell death induced by necrosis, degeneration of the tumor vasculature, stimulation of the antitumor immune response, and induction of inflammatory reactions in the illuminated region. However, the traditional compounds used in PDT limit its application. In this context, compounds of biotechnological origin with photosensitizing activity in association with nanotechnology are being used in PDT, aiming at its application in several types of cancer but with less toxicity toward neighboring tissues and better absorption of light for more aggressive types of cancer. In this review, we present studies involving innovatively developed PS that aimed to improve the efficiency of PDT in cancer treatment. Specifically, we focused on the clinical translation and application of PS of natural origin on cancer.

Unraveling the Pivotal Role of Atropisomerism for Cellular Internalization

The intrinsic challenge of large molecules to cross the cell membrane and reach intracellular targets is a major obstacle for the development of new medicines. We report how rotation along a single C-C bond, between atropisomers of a drug in clinical trials, improves cell uptake and therapeutic efficacy. The atropisomers of redaporfin (a fluorinated sulfonamide bacteriochlorin photosensitizer of 1135 Da) are separable and display orders of magnitude differences in photodynamic efficacy that are directly related to their differential cellular uptake. We show that redaporfin atropisomer uptake is passive and only marginally affected by ATP depletion, plasma proteins, or formulation in micelles. The α₄ atropisomer, where meso-phenyl sulfonamide substituents are on the same side of the tetrapyrrole macrocycle, exhibits the highest cellular uptake and phototoxicity. This is the most amphipathic atropisomer with a conformation that optimizes hydrogen bonding (H-bonding) with polar head groups of membrane phospholipids. Consequently, α₄ binds to the phospholipids on the surface of the membrane, flips into the membrane to adopt the orientation of a surfactant, and eventually diffuses to the interior of the cell (bind-flip mechanism). We observed increased α₄ internalization by cells of the tumor microenvironment in vivo and correlated this to the response of photodynamic therapy when tumor illumination was performed 24 h after α₄ administration. These results show that properly orientated aryl sulfonamide groups can be incorporated into drug design as efficient cell-penetrating motifs in vivo and reveal the unexpected biological consequences of atropisomerism.

Targeting Microenvironment of Melanoma and Head and Neck Cancers in Photodynamic Therapy

Background:

Photodynamic therapy (PDT), in comparison to other skin cancers, is still far less effective for melanoma, due to the strong absorbance and the role of melanin in cytoprotection. The tumour microenvironment (TME) has a significant role in tumour progression, and the hypoxic TME is one of the main reasons for melanoma progression to metastasis and its resistance to PDT. Hypoxia is also a feature of solid tumours in the head and neck region that indicates negative prognosis.

Objective:

The aim of this study was to individuate and describe systematically the main strategies in targeting the TME, especially hypoxia, in PDT against melanoma and head and neck cancers (HNC), and assess the current success in their application.

Methods:

PubMed was used for searching, in MEDLINE and other databases, for the most recent publications on PDT against melanoma and HNC in combination with the TME targeting and hypoxia.

Results:

In PDT for melanoma and HNC, it is very important to control hypoxia levels, and amongst the different approaches, oxygen self-supply systems are often applied. Vascular targeting is promising, but to improve it, optimal drug-light interval, and formulation to increase the accumulation of the photosensitiser in the tumour vasculature, have to be established. On the other side, the use of angiogenesis inhibitors, such as those interfering with VEGF signalling, is somewhat less successful than expected and needs to be further investigated.

Conclusion:

The combination of PDT with immunotherapy by using multifunctional nanoparticles continues to develop and seems to be the most promising for achieving a complete and lasting antitumour effect.

Photodynamic Therapy in Combination with Doxorubicin Is Superior to Monotherapy for the Treatment of Lung Cancer

We have previously shown that a radioactive (123I)-analog of methyl 3-(1'-(iodobexyloxy) ethyl-3-devinylpyropheophorbide-a (PET-ONCO), derived from chlorophyll-a can be used for positron emission tomography (PET) imaging of a variety of tumors, including those where 18F-FDG shows limitations. In this study, the photodynamic therapy (PDT) efficacy of the corresponding non-radioactive photosensitizer (PS) was investigated in a variety of tumor types (NSCLC, SCC, adenocarcinoma) derived from lung cancer patients in mice tumor models. The in vitro and in vivo efficacy was also investigated in combination with doxorubicin, and a significantly enhanced long-term tumor response was observed. The toxicity and toxicokinetic profile of the iodinated PS was also evaluated in male and female Sprague-Dawley rats and Beagle dog at variable doses (single intravenous injections) to assess reversibility or latency of any effects over a 28-day dose free period. The no-observed-adverse-effect (NOAEL) of the PS was considered to be 6.5 mg/kg for male and female rats, and for dogs, 3.45 mg/kg, the highest dose levels evaluated, respectively. The corresponding plasma Cmax and AYClast for male and female rats were 214,000 and 229,000 ng/mL and 3,680,000 and 3,810,000 h * ng/mL, respectively. For male and female dogs, the corresponding plasma Cmax and AYClast were 76,000 and 92,400 ng/mL and 976,000 and 1,200,000 h * ng/mL, respectively.

Synthesis and Characterization of Size- and Charge-Tunable Silver Nanoparticles for Selective Anticancer and Antibacterial Treatment

Advances in the research of nanoparticles (NPs) with controlled charge and size are driven by their potential application in the development of novel technologies and innovative therapeutics. This work reports the synthesis, characterization, and comprehensive biological evaluation of AgNPs functionalized by N,N,N-trimethyl-(11-mercaptoundecyl) ammonium chloride (TMA) and trisodium citrate (TSC). The prepared AgNPs were well characterized in terms of their morphological, spectroscopic and functional properties and biological activities. The implementation of several complementary techniques allowed not only the estimation of the average particle size (from 3 to 40 nm depending on the synthesis procedure used) but also the confirmation of the crystalline nature of the NPs and their round shape. To prove the usefulness of these materials in biological systems, cellular uptake and cytotoxicity in microbial and mammalian cells were determined. Positively charged 10 nm Ag@TMA2 revealed antimicrobial activity against Gram-negative bacteria with a minimum inhibitory concentration (MIC) value of 0.17 μg/mL and complete eradication of Escherichia coli (7 logs) for Ag@TMA2 at a concentration of 0.50 μg/mL, whereas negatively charged 10 nm Ag@TSC1 was effective against Gram-positive bacteria (MIC = 0.05 μg/mL), leading to inactivation of Staphylococcus aureus at relatively low concentrations. In addition, the largest 40 nm Ag@TSC2 was shown to exhibit pronounced anticancer activity against murine colon carcinoma (CT26) and murine mammary gland carcinoma (4T1) cells cultured as 2D and 3D tumor models and reduced toxicity against human HaCaT keratinocytes. Among the possible mechanisms of AgNPs are their ability to generate reactive oxygen species, which was further evaluated in vitro and correlates well with cellular accumulation and overall activity of AgNPs. Furthermore, we confirmed the anticancer efficacy of the most potent Ag@TSC2 in hiPSC-derived colonic organoids and demonstrated that the NPs are biocompatible and applicable in vivo. A pilot study in BALB/c mice evidenced that the treatment with Ag@TSC2 resulted in temporary (>60 days) remission of CT26 tumors.

Photodynamic inactivation (PDI) as a promising alternative to current pharmaceuticals for the treatment of resistant microorganisms

Although the whole world is currently observing the global battle against COVID-19, it should not be underestimated that in the next 30 years, approximately 10 million people per year could be exposed to infections caused by multi-drug resistant bacteria. As new antibiotics come under pressure from unpredictable resistance patterns and relegation to last-line therapy, immediate action is needed to establish a radically different approach to countering resistant microorganisms. Among the most widely explored alternative methods for combating bacterial infections are metal complexes and nanoparticles, often in combination with light, but strategies using monoclonal antibodies and bacteriophages are increasingly gaining acceptance. Photodynamic inactivation (PDI) uses light and a dye termed a photosensitizer (PS) in the presence of oxygen to generate reactive oxygen species (ROS) in the field of illumination that eventually kill microorganisms. Over the past few years, hundreds of photomaterials have been investigated, seeking ideal strategies based either on single molecules (e.g., tetrapyrroles, metal complexes) or in combination with various delivery systems. The present work describes some of the most recent advances of PDI, focusing on the design of suitable photosensitizers, their formulations, and their potential to inactivate bacteria, viruses, and fungi. Particular attention is focused on the compounds and materials developed in our laboratories that are capable of killing in the exponential growth phase (up to seven logarithmic units) of bacteria without loss of efficacy or resistance, while being completely safe for human cells. Prospectively, PDI using these photomaterials could potentially cure infected wounds and oral infections caused by various multidrug-resistant bacteria. It is also possible to treat the surfaces of medical equipment with the materials described, in order to disinfect them with light, and reduce the risk of nosocomial infections.

Connexin Hemichannel Activation by S-Nitrosoglutathione Synergizes Strongly with Photodynamic Therapy Potentiating Anti-Tumor Bystander Killing

Simple Summary

Bystander effects depend on direct cell-cell communication and/or paracrine signaling mediated by the release of soluble factors into the extracellular environment and may greatly influence therapy outcome. Although the limited data available suggest a role for intercellular gap junction channels, far less is known about the role of connexin hemichannels. Here, we investigated bystander effects induced by photodynamic therapy in syngeneic murine melanoma models in vivo. We determined that (i) photoactivation of a photosensitizer triggered calcium-dependent cell death pathways in both irradiated and bystander tumor cells; (ii) hemichannel activity and adenosine triphosphate release were key factors for the induction of bystander cell death; and (iii) bystander cell killing and antitumor response elicited by photodynamic therapy were greatly enhanced by combination treatment with S-nitrosoglutathione, which promoted hemichannel opening in these experimental conditions. Therefore, these findings in a preclinical model have important translational potential.

Abstract

In this study, we used B16-F10 cells grown in the dorsal skinfold chamber (DSC) preparation that allowed us to gain optical access to the processes triggered by photodynamic therapy (PDT). Partial irradiation of a photosensitized melanoma triggered cell death in non-irradiated tumor cells. Multiphoton intravital microscopy with genetically encoded fluorescence indicators revealed that bystander cell death was mediated by paracrine signaling due to adenosine triphosphate (ATP) release from connexin (Cx) hemichannels (HCs). Intercellular calcium (Ca²⁺) waves propagated from irradiated to bystander cells promoting intracellular Ca²⁺ transfer from the endoplasmic reticulum (ER) to mitochondria and rapid activation of apoptotic pathways. Combination treatment with S-nitrosoglutathione (GSNO), an endogenous nitric oxide (NO) donor that biases HCs towards the open state, greatly potentiated anti-tumor bystander killing via enhanced Ca²⁺ signaling, leading to a significant reduction of post-irradiation tumor mass. Our results demonstrate that HCs can be exploited to dramatically increase cytotoxic bystander effects and reveal a previously unappreciated role for HCs in tumor eradication promoted by PDT.

Nanocarriers for Photodynamic Therapy Intended to Cutaneous Tumors

Photodynamic Therapy (PDT) is a therapeutic modality used for several malignant and premalignant skin disorders, including Bowen's disease skin cancers and Superficial Basal Cell Carcinoma (BCC). Several photosensitizers (PSs) have been explored for tumor destruction of skin cancers, after their activation by a light source of appropriate wavelength. Topical release of PSs avoids prolonged photosensitization reactions associated with systemic administration; however, its clinical usefulness is influenced by its poor tissue penetration and the stability of the active agent. Nanotechnology-based drug delivery systems are promising tool to enhance the efficiency for PDT of cancer. This review focuses on PSs encapsulated in nanocarriers explored for PDT of skin tumors.

Curcumin-loaded Pluronic® F-127 Micelles as a Drug Delivery System for Curcumin-mediated Photodynamic Therapy for Oral Application

Antimicrobial photodynamic therapy (aPDT) is promising for oral decontamination. Curcumin has been used as photosensitizer; however, the hydrophobic properties can negatively affect aPDT. This study evaluated the aPDT efficacy using Cur-loaded Pluronic^® F-127 micelles against Streptococcus mutans and Candida albicans biofilms. Micelles characterization was performed by zeta potential, dynamic light scattering, transmission electron microscopy, absorption and fluorescence spectroscopy. Cur concentrations, cell viability by CFU mL^-1 and confocal microscopy were determined. Data were analyzed by parametric and nonparametric tests under 5%. Cur-loaded Pluronic^® F-127 exhibited spherical shape, suitable particle size (≤100 nm), adequate polydispersity index, best stability, lower photodegradation and autoaggregation compared to unloaded-Cur. Both microorganisms were sensitive to Cur-loaded Pluronic^® F-127 micelles aPDT, with minimum inhibitory concentration (MIC) of 270 μm and 2.1093 μm for S. mutans and C. albicans suspended culture, respectively. Cur-loaded Pluronic^® F-127 aPDT exhibited antibacterial/antifungal effect against the biofilms (~3 log₁₀ reduction; P ≤ 0.05); however, similar to unloaded (P ≥ 0.05). Confocal images confirmed these results. Cur-loaded Pluronic^® F-127 micelles exhibited good photo-chemical properties and may be a viable alternative to deliver Cur and to improve aPDT effect during the treatment of dental caries. Moreover, Pluronic^® micelles can enhance the solubility, stability, permeability and control the release of Cur.

Pluronic-based nanovehicles: Recent advances in anticancer therapeutic applications

Pluronics are a class of amphiphilic tri-block copolymers with wide pharmaceutical applicability. In the past decades, the ability to form biocompatible nanosized micelles was exploited to formulate stable drug nanovehicles with potential use in antitumor therapy. Due to the great potential for tuning physical and structural properties of Pluronic unimers, a panoply of drug or polynucleotide-loaded micelles was prepared and tested for their antitumoral activity. The attractive inherent antitumor properties of Pluronic polymers in combination with cell targeting and stimuli-responsive ligands greatly improved antitumoral therapeutic effects of tested drugs. In spite of that, the extraordinary complexity of biological challenges in the delivery of micellar drug payload makes their therapeutic potential still not exploited to the fullest. In this review paper we attempt to present the latest developments in the field of Pluronic based nanovehicles and their application in anticancer therapy with an overview of the chemistry involved in the preparation of these nanovehicles.

Optical clearing agent increases effectiveness of photodynamic therapy in a mouse model of cutaneous melanoma: an analysis by Raman microspectroscopy

Melanoma is the most aggressive type of skin cancer and a relevant health problem due to its poor treatment response with high morbidity and mortality rates. This study, aimed to investigate the tissue changes of an improved photodynamic therapy (PDT) response when combined with optical clearing agent (OCA) in the treatment of cutaneous melanoma in mice. Photodithazine (PDZ) was administered intraperitoneally and a solution of OCA was topically applied before PDT irradiation. Due to a resultant refractive index matching, OCA-treated tumors are more optically homogenous, improving the PDT response. Raman analysis revealed, when combined with OCA, the PDT response was more homogenous down to 725 µm-depth in thickness.

Co-delivery of IR-768 and daunorubicin using mPEG-b-PLGA micelles for synergistic enhancement of combination therapy of melanoma

Malignant melanoma is an emerging problem worldwide due to the high degree of lethalness. Its aggressiveness and the ability to metastasize along with the heterogeneity at the molecular and cellular levels, limit the overall therapeutic efficacy. Despite significant advances in melanoma treatment over the last decade, there is still a need for improved therapeutic modalities. Thus, we demonstrate here a combinatorial approach that targets multiple independent therapeutic pathways, in which polymeric micelles (PMs) were used as efficacious colloidal nanocarriers loaded with both daunorubicin (DRB) as a cytotoxic drug and IR-768 as a photosensitizer. This afforded the dual drug loaded delivery system IR-768 + DRB in PMs. The fabricated mPEG-b-PLGA micelles (hydrodynamic diameters ≈ 25 nm) had a relatively narrow size distribution (PdI > ca. 0.3) with uniform spherical shapes. CLSM study showed that mPEG-b-PLGA micelles were uptaken by mitochondria, which further contributed to excellent singlet oxygen generation capacity for PDT in A375 melanoma cells. Furthermore, the PMs were efficiently internalized by tested cells through endocytosis, resulting in much higher cellular uptake comparing to the free drug. As a result of these properties, IR-768 + DRB in PMs exhibited very potent and synergistically enhanced anticancer activity against A375 cells. Additionally, this combination approach allowed to reduce drug doses and provided low side effects towards normal HaCaT. This study indicates excellent properties of mPEG-b-PLGA micelles resulting in great therapeutic potential possessed by the developed nanoscale drug delivery system for combined chemo-photodynamic therapy of melanoma.

Dual-Agent Photodynamic Therapy with Optical Clearing Eradicates Pigmented Melanoma in Preclinical Tumor Models

Treatment using light-activated photosensitizers (photodynamic therapy, PDT) has shown limited efficacy in pigmented melanoma, mainly due to the poor penetration of light in this tissue. Here, an optical clearing agent (OCA) was applied topically to a cutaneous melanoma model in mice shortly before PDT to increase the effective treatment depth by reducing the light scattering. This was used together with cellular and vascular-PDT, or a combination of both. The effect on tumor growth was measured by longitudinal ultrasound/photoacoustic imaging in vivo and by immunohistology after sacrifice. In a separate dorsal window chamber tumor model, angiographic optical coherence tomography (OCT) generated 3D tissue microvascular images, enabling direct in vivo assessment of treatment response. The optical clearing had minimal therapeutic effect on the in control, non-pigmented cutaneous melanomas but a statistically significant effect (p < 0.05) in pigmented lesions for both single- and dual-photosensitizer treatment regimes. The latter enabled full-depth eradication of tumor tissue, demonstrated by the absence of S100 and Ki67 immunostaining. These studies are the first to demonstrate complete melanoma response to PDT in an immunocompromised model in vivo, with quantitative assessment of tumor volume and thickness, confirmed by (immuno) histological analyses, and with non-pigmented melanomas used as controls to clarify the critical role of melanin in the PDT response. The results indicate the potential of OCA-enhanced PDT for the treatment of pigmented lesions, including melanoma.

Recent advances in strategies for overcoming hypoxia in photodynamic therapy of cancer

The selectivity of photodynamic therapy (PDT) derived from the tailored accumulation of photosensitizing drug (photosensitizer; PS) in the tumor microenvironment (TME), and from local irradiation, turns it into a "magic bullet" for the treatment of resistant tumors without sparing the healthy tissue and possible adverse effects. However, locally-induced hypoxia is one of the undesirable consequences of PDT, which may contribute to the emergence of resistance and significantly reduce therapeutic outcomes. Therefore, the development of strategies using new approaches in nanotechnology and molecular biology can offer an increased opportunity to eliminate the disadvantages of hypoxia. Emerging evidence indicates that wisely designed phototherapeutic procedures, including: (i) ROS-tunable photosensitizers, (ii) organelle targeting, (iii) nano-based photoactive drugs and/or PS delivery nanosystems, as well as (iv) combining them with other strategies (i.e. PTT, chemotherapy, theranostics or the design of dual anticancer drug and photosensitizers) can significantly improve the PDT efficacy and overcome the resistance. This mini-review addresses the role of hypoxia and hypoxia-related molecular mechanisms of the HIF-1α pathway in the regulation of PDT efficacy. It also discusses the most recent achievements as well as future perspectives and potential challenges of PDT application against hypoxic tumors.

Oxidative Stress and Photodynamic Therapy of Skin Cancers: Mechanisms, Challenges and Promising Developments

Ultraviolet radiation is one of the most pervasive environmental interactions with humans. Chronic ultraviolet irradiation increases the danger of skin carcinogenesis. Probably, oxidative stress is the most important mechanism by which ultraviolet radiation implements its damaging effects on normal cells. However, notwithstanding the data referring to the negative effects exerted by light radiation and oxidative stress on carcinogenesis, both factors are used in the treatment of skin cancer. Photodynamic therapy (PDT) consists of the administration of a photosensitiser, which undergoes excitation after suitable irradiation emitted from a light source and generates reactive oxygen species. Oxidative stress causes a condition in which cellular components, including DNA, proteins, and lipids, are oxidised and injured. Antitumor effects result from the combination of direct tumour cell photodamage, the destruction of tumour vasculature and the activation of an immune response. In this review, we report the data present in literature dealing with the main signalling molecular pathways modified by oxidative stress after photodynamic therapy to target skin cancer cells. Moreover, we describe the progress made in the design of anti-skin cancer photosensitisers, and the new possibilities of increasing the efficacy of PDT via the use of molecules capable of developing a synergistic antineoplastic action.

Pluronic F-127: An Efficient Delivery Vehicle for 3-(1'-hexyloxy)ethyl-3-devinylpyropheophorbide-a (HPPH or Photochlor)

To determine the impact of delivery vehicles in photosensitizing efficacy of HPPH, a hydrophobic photosensitizer was dissolved in various formulations: 1% Tween 80/5% dextrose, Pluronic P-123 and Pluronic F-127 in 0.5%, 1% and 2% phosphate buffer solutions (PBS). HPPH was also conjugated to Pluronic F-127, and the resulting conjugate (PL-20) was formulated in PBS. Among the different delivery vehicles, only Pluronic P-123 displayed significant vehicle cytotoxicity, whereas Pluronic F127 was nontoxic. Compared to PL-20, HPPH formulated in Tween80 and Pluronic F-127 showed higher cell-uptake, but lower long-term retention in Colon26 cell compared to PL-20. The higher retention of PL-20 was similarly observed during in vivo uptake with BALB/c mice baring Ct26 tumors. In contrast to the in vitro uptake experiments, PL-20 showed slightly higher uptake compared to HPPH formulated in Tween or Pluronic-F127. A significant difference in pharmacokinetic profile was also observed between the HPPH-Pluronic formulation and PL-20. Under similar in vivo treatment parameters (drug dose 0.47 µmol kg^-1 , light dose: 135 J cm^-2 at 24 h post-injection of PS), HPPH formulated either in Tween or Pluronic F-127 formulation showed similar in vivo PDT efficacy (20-30% tumor cure on day 60), whereas PL-20 showed 40% tumor cure (day 60).

Enhanced Cellular Uptake and Photodynamic Effect with Amphiphilic Fluorinated Porphyrins: The Role of Sulfoester Groups and the Nature of Reactive Oxygen Species

A class of amphiphilic photosensitizers for photodynamic therapy (PDT) was developed. Sulfonate esters of modified porphyrins bearing-F substituents in the ortho positions of the phenyl rings have adequate properties for PDT, including absorption in the red, increased cellular uptake, favorable intracellular localization, low cytotoxicity, and high phototoxicity against A549 (human lung adenocarcinoma) and CT26 (murine colon carcinoma) cells. Moreover, the role of type I and type II photochemical processes was assessed by fluorescent probes specific for various reactive oxygen species (ROS). The photodynamic effect is improved not only by enhanced cellular uptake but also by the high generation of both singlet oxygen and oxygen-centered radicals. All of the presented results support the idea that the rational design of photosensitizers for PDT can be further improved by better understanding the determinants affecting its therapeutic efficiency and explain how smart structural modifications can make them suitable photosensitizers for application in PDT.

Upconversion Nanoparticle-Induced Multimode Photodynamic Therapy Based on a Metal-Organic Framework/Titanium Dioxide Nanocomposite

Photodynamic therapy (PDT) possesses two pathways depending on the type of high-toxicity reactive oxygen species (ROS), superoxide anion radical (O₂^·-) and hydroxyl radical (^·OH) generated through Type I and singlet oxygen (¹O₂) generated through Type II, inducing cancer cell apoptosis. However, the low efficiency of ROS generation and poor biocompatibility are the limitations of the traditional photosensitizers for PDT. Herein, inspired by photochemical reactions of titanium dioxide and porphyrin-based metal-organic frameworks, we developed a nanoplatform by covering ultrasmall titanium dioxide nanoparticles on a heterodimer made up of upconversion nanoparticles and metal-organic frameworks, realizing a multimode PDT through Type I and Type II mechanisms. Once irradiated by a near-infrared light, upconversion nanoparticles could generate ultraviolet and visible lights, which were not only able to stimulate different photochemical reactions of titanium dioxide and porphyrin but also accomplish deep penetration photodynamic therapy. Our photosensitive agent exhibited good biocompatibility and an effective multimode PDT performance, which could meet the needs of different situations of photodynamic therapy in the future.

Photodynamic Therapy for Cancer: What's Past is Prologue

Thomas J Dougherty from Roswell Park Cancer Center played a major role in the progress of photodynamic therapy (PDT) from a laboratory science into a real-world clinical therapy to treat patients with cancer. Nevertheless over the succeeding 45 years, it is fair to say that the overall progress of clinical PDT for cancer has been somewhat disappointing. The goal of this perspective article is to summarize some of the clinical trials run by various companies using photosensitizers with different structures that have been conducted for different types of cancer. While some have been successful, others have failed, and several are now ongoing. I will attempt to touch on some factors, which have influenced this checkered history and look forward to the future of clinical PDT for cancer.

Anticancer potency of novel organometallic Ir(iii) complexes with phosphine derivatives of fluoroquinolones encapsulated in polymeric micelles

A 3D model of cell culturing (spheroids) was explored and the anticancer potential of the selected novel organometallic Ir(iii) complex encapsulated in Pluronic p-123 micelles was clearly proved.

Lipophilicity of Bacteriochlorin-Based Photosensitizers as a Determinant for PDT Optimization through the Modulation of the Inflammatory Mediators

: Photodynamic therapy (PDT) augments the host antitumor immune response, but the role of the PDT effect on the tumor microenvironment in dependence on the type of photosensitizer and/or therapeutic protocols has not been clearly elucidated. We employed three bacteriochlorins (F2BOH, F2BMet and Cl2BHep) of different polarity that absorb near-infrared light (NIR) and generated a large amount of reactive oxygen species (ROS) to compare the PDT efficacy after various drug-to-light intervals: 15 min. (V-PDT), 3h (E-PDT) and 72h (C-PDT). We also performed the analysis of the molecular mechanisms of PDT crucial for the generation of the long-lasting antitumor immune response. PDT-induced damage affected the integrity of the host tissue and developed acute (protocol-dependent) local inflammation, which in turn led to the infiltration of neutrophils and macrophages. In order to further confirm this hypothesis, a number of proteins in the plasma of PDT-treated mice were identified. Among a wide range of cytokines (IL-6, IL-10, IL-13, IL-15, TNF-α, GM-CSF), chemokines (KC, MCP-1, MIP1α, MIP1β, MIP2) and growth factors (VEGF) released after PDT, an important role was assigned to IL-6. PDT protocols optimized for studied bacteriochlorins led to a significant increase in the survival rate of BALB/c mice bearing CT26 tumors, but each photosensitizer (PS) was more or less potent, depending on the applied DLI (15 min, 3 h or 72 h). Hydrophilic (F2BOH) and amphiphilic (F2BMet) PSs were equally effective in V-PDT (>80 cure rate). F2BMet was the most efficient in E-PDT (DLI = 3h), leading to a cure of 65 % of the animals. Finally, the most powerful PS in the C-PDT (DLI = 72 h) regimen turned out to be the most hydrophobic compound (Cl2BHep), allowing 100 % of treated animals to be cured at a light dose of only 45 J/cm2.

Extremely Effective Chemoradiotherapy by Inducing Immunogenic Cell Death and Radio-Triggered Drug Release under Hypoxia Alleviation

Local hypoxia in solid malignancies often results in resistance to radiotherapy (RT) and chemotherapy (CT), which may be one of the main reasons for their failure in clinical application. Especially, oxygen is an essential element for enhancing DNA damage caused by ionizing radiation in radiotherapy. Here, two biomimetic oxygen delivery systems were designed by encapsulating hemoglobin (Hb) alone into a liposome (Hb-Lipo) or co-encapsulating Hb and doxorubicin (DOX) into a liposome (DOX-Hb-Lipo). Our data indicated that both Hb-Lipo and DOX-Hb-Lipo could effectively alleviate hypoxia in tumors. We demonstrated that RT plus tumor-targeting delivery of oxygen mediated by Hb-Lipo could significantly overcome the tolerance of hypoxic cancer cells to RT, showing significantly enhanced cancer-cell killing and tumor growth inhibition ability, mainly attributing to hypoxia alleviation and increased reactive oxygen species production under RT in cancer cells. Furthermore, a melanoma model that was quite insensitive to both RT and CT was used to test the efficacy of chemoradiotherapy combined with hypoxia alleviation. RT plus Hb-Lipo only caused a limited increase in antitumor activity. However, extremely strong tumor inhibition could be obtained by RT combined with DOX-Hb-Lipo-mediated CT, attributed to radio-triggered DOX release and enhanced immunogenic cell death induced by RT under an oxygen supplement. Our study provided a valuable reference for overcoming hypoxia-induced radioresistance and a useful therapeutic strategy for cancers that are extremely insensitive to chemo- or radiotherapy.

Bioinspired multifunctional biomaterials with hierarchical microstructure for wound dressing

Developing multifunctional wound dressing with desired mechanical strength is of great significance for the treatment of different types of skin wounds. Inspired by the close relationship between strength and hierarchical structure of nacre, hierarchical and porous graphene oxide-chitosan-calcium silicate (GO-CTS-CS) film biomaterials are fabricated by a combination of vacuum filtration-assisted assembly and freeze-drying methods. The bioinspired hierarchical materials emulate an orderly porous lamellar micron-scale structure and the "brick-and-mortar"-layered nanostructure. The hierarchical microstructure endows the GO-CTS-CS biomaterials with good tensile strength, compatible breathability, and water absorption. Furthermore, the hierarchical GO-CTS-CS biomaterials exhibit ideal photothermal performance, leading to significant photothermal antibacterial and antitumor efficacy. Further, the hierarchical GO-CTS-CS biomaterials show stimulatory effect on in vivo chronic wound healing. Therefore, such a high performance and multifunctional biomaterial is believed to offer a promising alternative to traditional wound dressing in future. STATEMENT OF SIGNIFICANCE: Although it is an effective strategy to prepare high-performance materials by mimicking the hierarchical microstructure of nacre, the preparation of nacre-inspired materials in tissue engineering fields still needs to be investigated. In this work, we prepared a nacre-inspired multifunctional graphene oxide-chitosan-calcium silicate (GO-CTS-CS) biomaterial with a hierarchical microstructure. The hierarchical microstructure endows the biomaterials with desired properties of strength, breathability, and water absorption. Further, the hierarchical GO-CTS-CS biomaterial showed good photothermal antibacterial/antitumor and wound healing effects. This work may provide an approach to combine the preparation of multifunctional biomaterials with bioinspired engineering by constructing a hierarchical microstructure, indicating that the assembling hierarchical microstructure in biomaterials is of great importance for tissue engineering and regenerative medicine.