Current clinical and preclinical photosensitizers for use in photodynamic therapy

Visible-to-NIR-Light Activated Release: From Small Molecules to Nanomaterials

Photoactivatable (alternatively, photoremovable, photoreleasable, or photocleavable) protecting groups (PPGs), also known as caged or photocaged compounds, are used to enable non-invasive spatiotemporal photochemical control over the release of species of interest. Recent years have seen the development of PPGs activatable by biologically and chemically benign visible and near-infrared (NIR) light. These long-wavelength-absorbing moieties expand the applicability of this powerful method and its accessibility to non-specialist users. This review comprehensively covers organic and transition metal-containing photoactivatable compounds (complexes) that absorb in the visible- and NIR-range to release various leaving groups and gasotransmitters (carbon monoxide, nitric oxide, and hydrogen sulfide). The text also covers visible- and NIR-light-induced photosensitized release using molecular sensitizers, quantum dots, and upconversion and second-harmonic nanoparticles, as well as release via photodynamic (photooxygenation by singlet oxygen) and photothermal effects. Release from photoactivatable polymers, micelles, vesicles, and photoswitches, along with the related emerging field of photopharmacology, is discussed at the end of the review.

NIR Photoregulated Theranostic System Based on Hexagonal-Phase Upconverting Nanoparticles for Tumor-Targeted Photodynamic Therapy and Fluorescence Imaging

Although photodynamic therapy (PDT) is an effective, minimally invasive therapeutic modality with advantages in highly localized and specific tumor treatments, large and deep-seated cancers within the body cannot be successfully treated due to low transparency to visible light. To improve the therapeutic efficiency of tumor treatment in deep tissue and reduce the side effects in normal tissue, this study developed a near-infrared (NIR)-triggered upconversion nanoparticle (UCNP)-based photosensitizer (PS) carrier as a new theranostics system. The NaYF4:Yb/Er UCNPs were synthesized by a hydrothermal method, producing nanoparticles of a uniformly small size (≈20 nm) and crystalline morphology of the hexagonal phase. These UCNPs were modified with folic acid-conjugated biocompatible block copolymers through a bidentate dihydrolipoic acid linker. The polymer modified hexagonal phase UCNPs (FA-PEAH-UCNPs) showed an improved dispersibility in the aqueous solution and strong NIR-to-vis upconversion fluorescence. The hydrophobic PS, pheophorbide a (Pha), was then conjugated to the stable vectors. Moreover, these UCNP-based Pha carriers containing tumor targeting folic acid ligands exhibited the significantly enhanced cellular uptake efficiency as well as PDT treatment efficiency. These results suggested that this system could extend the excitation wavelength of PDT to the NIR region and effectively improve therapeutic efficiency of PSs.

Ligand-Targeted Delivery of Photosensitizers for Cancer Treatment

Photodynamic therapy (PDT) is a promising cancer treatment which involves a photosensitizer (PS), light at a specific wavelength for PS activation and oxygen, which combine to elicit cell death. While the illumination required to activate a PS imparts a certain amount of selectivity to PDT treatments, poor tumor accumulation and cell internalization are still inherent properties of most intravenously administered PSs. As a result, common consequences of PDT include skin photosensitivity. To overcome the mentioned issues, PSs may be tailored to specifically target overexpressed biomarkers of tumors. This active targeting can be achieved by direct conjugation of the PS to a ligand with enhanced affinity for a target overexpressed on cancer cells and/or other cells of the tumor microenvironment. Alternatively, PSs may be incorporated into ligand-targeted nanocarriers, which may also encompass multi-functionalities, including diagnosis and therapy. In this review, we highlight the major advances in active targeting of PSs, either by means of ligand-derived bioconjugates or by exploiting ligand-targeting nanocarriers.

Application of a polyelectrolyte complex based on biocompatible polysaccharides for colorectal cancer inhibition

Strategies for incorporating water-insoluble photosensitisers (PS) in drug delivery systems have been extensively studied. In this work, we evaluate the formation, characterisation, drug sorption studies, and cytotoxicity of chitosan (CHT)/chondroitin sulphate (CS) polyelectrolyte complexes (PECs) coated with polystyrene-block-poly(acrylic acid) (PS-b-PAA) nanoparticles (NPs) loaded with chloroaluminum phthalocyanine (AlClPc). The PECs were characterised by infrared spectroscopy (FTIR), differential scanning calorimetric (DSC), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The PS-b-PAA NPs on the PEC surface was confirmed by scanning electron microscopy (SEM). Additionally, optical images distinguished the PEC structures containing PS-b-PAA or PS-b-PAA/AlClPc from the unloaded PEC. Kinetic and equilibrium studies investigate the sorption capacity of the PEC/PS-b-PAA toward AlClPc. The encapsulation efficiency reached 95% at 190 μg mL^-1 AlClPc after only 15 min. The Brunauer-Emmett-Teller (BET) isotherm and pseudo-second-order kinetic fitted well to the experimental data. The PS-b-PAA NPs on the PEC surfaces increase the AlClPc bioavailability and the PEC structure stabilizes the PS-b-PAA/AlClPc nanostructures. The materials were cytocompatible upon healthy VERO (kidney epithelial cells), and cytotoxic against colorectal cancerous cells (HT-29 cells). For the first time, we associate PS-b-PAA/AlClPc with a hydrophilic and cytocompatible polysaccharide matrix. We suggest the use of these materials in strategies to treat cancer by using photodynamic therapy.

Acid-Activatable Transmorphic Peptide-Based Nanomaterials for Photodynamic Therapy

Inspired by the dynamic morphology control of molecular assemblies in biological systems, we have developed pH-responsive transformable peptide-based nanoparticles for photodynamic therapy (PDT) with prolonged tumor retention times. The self-assembled peptide-porphyrin nanoparticles transformed into nanofibers when exposed to the acidic tumor microenvironment, which was mainly driven by enhanced intermolecular hydrogen bond formation between the protonated molecules. The nanoparticle transformation into fibrils improved their singlet oxygen generation ability and enabled high accumulation and long-term retention at tumor sites. Strong fluorescent signals of these nanomaterials were detected in tumor tissue up to 7 days after administration. Moreover, the peptide assemblies exhibited excellent anti-tumor efficacy via PDT in vivo. This in situ fibrillar transformation strategy could be utilized to design effective stimuli-responsive biomaterials for long-term imaging and therapy.

Phototherapy Combined with Carbon Nanomaterials (1D and 2D) and their Applications in Cancer Therapy

Carbon-based materials have attracted research interest worldwide due to their physical and chemical properties and wide surface area, rendering them excellent carrier molecules. They are widely used in biological applications like antimicrobial activity, cancer diagnosis, bio-imaging, targeting, drug delivery, biosensors, tissue engineering, dental care, and skin care. Carbon-based nanomaterials like carbon nanotubes and graphene have drawn more attention in the field of phototherapy due to their unique properties such as thermal conductivity, large surface area, and electrical properties. Phototherapy is a promising next-generation therapeutic modality for many modern medical conditions that include cancer diagnosis, targeting, and treatment. Phototherapy involves the major administration of photosensitizers (PSs), which absorb light sources and emit reactive oxygen species under cellular environments. Several types of nontoxic PSs are functionalized on carbon-based nanomaterials and have numerous advantages in cancer therapy. In this review, we discuss the potential role and combined effect of phototherapy and carbon nanomaterials, the mechanism and functionalization of PSs on nanomaterials, and their promising advantages in cancer therapy.

Drug delivery systems based on CD44-targeted glycosaminoglycans for cancer therapy

The polysaccharide-based biomaterials hyaluronic acid (HA) and chondroitin sulfate (CS) have aroused great interest for use in drug delivery systems for tumor therapy, as they have outstanding biocompatibility and great targeting ability for cluster determinant 44 (CD44). In addition, modified HA and CS can self-assemble into micelles or micellar nanoparticles (NPs) for targeted drug delivery. This review discusses the formation of HA- and CS-based NPs, and various types of CS-based NPs including CS-drug conjugates, CS-polymer NPs, CS-small molecule NPs, polyelectrolyte nanocomplexes (PECs), CS-metal NPs, and nanogels. We then focus on the applications of HA- and CS-based NPs in tumor chemotherapy, gene therapy, photothermal therapy (PTT), photodynamic therapy (PDT), sonodynamic therapy (SDT), and immunotherapy. Finally, this review is expected to provide guidelines for the development of various HA- and CS-based NPs used in multiple cancer therapies.

New Design Strategy Toward NIR I Xanthene-Based Dyes

An effective design strategy with an efficient synthetic route to xanthene-based far-red to near-infrared dyes is reported. The dyes were prepared by the Suzuki cross-coupling of the electron-poor fluorescein ditriflate with the electron-rich boronic acid/ester-functionalized pyrrole (2C/3C) and indole (2D/3D) moieties. Upon treatment with trifluoroacetic acid, the closed nonfluorescent forms of the dyes (2C and 2D) ring-opened to their fluorescent forms (3C and 3D). The absorption maxima were 665 and 704 nm, while the emission maxima were 717 and 719 nm for 3C and 3D, respectively. The closed forms of the dyes were soluble in chloroform and acetonitrile. To test the efficacy of the dyes as probes, a turn-off fluoride ion probe was prepared from 3C, which consisted of a silyl ester receptor. The probe responded strongly to low concentrations of fluoride, carbonate, and acetate ions, weakly to phosphate ions, but not to the other halogens. Moreover, the probe can detect the minimum concentration of F^- in water.

Elucidation of the Intersystem Crossing Mechanism in a Helical BODIPY for Low-Dose Photodynamic Therapy

Intersystem crossing (ISC) of triplet photosensitizers is a vital process for fundamental photochemistry and photodynamic therapy (PDT). Herein, we report the co-existence of efficient ISC and long triplet excited lifetime in a heavy atom-free bodipy helicene molecule. Via theoretical computation and time-resolved EPR spectroscopy, we confirmed that the ISC of the bodipy results from its twisted molecular structure and reduced symmetry. The twisted bodipy shows intense long wavelength absorption (ϵ=1.76×105  m-1  cm-1 at 630 nm), satisfactory triplet quantum yield (ΦT =52 %), and long-lived triplet state (τT =492 μs), leading to unprecedented performance as a triplet photosensitizer for PDT. Moreover, nanoparticles constructed with such helical bodipy show efficient PDT-mediated antitumor immunity amplification with an ultra-low dose (0.25 μg kg-1 ), which is several hundred times lower than that of the existing PDT reagents.

Photocontrolled activation of small molecule cancer therapeutics

Cancer remains one of the leading causes of death worldwide. Conventional treatment of the disease is comprised of chemotherapy, radiation and surgery among other treatment approaches. Chemotherapy is plagued by multiple side-effects caused due to non-specific drug action. Light-based therapies offer an alternative treatment approach that can be fine tuned to achieve the desired effect to treat the disease and address challenges posed by chemotherapeutic side-effects. Photodynamic therapy (PDT) is one of the light mediated treatment modalities that has been successfully applied to treat superficial malignancies with high-efficiency, although its dependence on normoxic conditions limits its efficiency to treat deep-seated tumors. On the other hand, light-sensitive drug-mimetics and drug-release platforms have been deemed efficient in preclinical settings to induce cancer cell death with minimal collateral damage. Drawing from about a decade's worth of examples, we highlight the application of photosensitive molecules as an alternative therapeutic option to PDT and describe their designs that influence the biology of the cancer cells, in turn affecting their viability with high spatio-temporal control.

3-Bromopyruvate-Conjugated Nanoplatform-Induced Pro-Death Autophagy for Enhanced Photodynamic Therapy against Hypoxic Tumor

Autophagy triggered by reactive oxygen species (ROS) in photodynamic therapy (PDT) generally exhibits an anti-apoptotic effect to promote cell survival. Herein, an innovative supramolecular nanoplatform was fabricated for enhanced PDT by converting the role of autophagy from pro-survival to pro-death. The respiration inhibitor 3-bromopyruvate (3BP), which can act as an autophagy promoter and hypoxia ameliorator, was integrated into photosensitizer chlorin e6 (Ce6)-encapsulated nanoparticles to combat hypoxic tumor. 3BP could inhibit respiration by down-regulating HK-II and GAPDH expression to significantly reduce intracellular oxygen consumption rate, which could relieve tumor hypoxia for enhanced photodynamic cancer therapy. More importantly, the autophagy level was significantly elevated by the combination of 3BP and PDT determined by Western blot, immunofluorescent imaging, and transmission electron microscopy. It was very surprising that excessively activated autophagy promoted cell apoptosis, leading to the changeover of autophagy from pro-survival to pro-death. Therefore, PDT combined with 3BP could achieve efficient cell proliferation inhibition and tumor regression. Furthermore, hypoxia-inducible factor-1α (HIF-1α) could be down-regulated after tumor hypoxia was relieved by 3BP. Tumor metastasis could then be effectively inhibited by eliminating primary tumors and down-regulating HIF-1α expression. These results provide an inspiration for future innovative approaches of cancer therapy by triggering pro-death autophagy.

Vascular Shutdown by Photodynamic Therapy Using Talaporfin Sodium

Photodynamic therapy (PDT) is an attractive cancer treatment modality. Talaporfin sodium, a second-generation photosensitizer, results in lower systemic toxicity and relatively better selective tumor destruction than first-generation photosensitizers. However, the mechanism through which PDT induces vascular shutdown is unclear. In this study, the in vitro effects of talaporfin sodium-based PDT on human umbilical vein endothelial cells (HUVECs) were determined through cell viability and endothelial tube formation assays, and evaluation of the tubulin and F-actin dynamics and myosin light chain (MLC) phosphorylation. Additionally, the effects on tumor blood flow and tumor vessel destruction were assessed in vivo. In the HUVECs, talaporfin sodium-based PDT induced endothelial tube destruction and microtubule depolymerization, triggering the formation of F-actin stress fibers and a significant increase in MLC phosphorylation. However, pretreatment with the Rho-associated protein kinase (ROCK) inhibitor, Y27632, completely prevented PDT-induced stress fiber formation and MLC phosphorylation. The in vivo analysis and pathological examination revealed that the PDT had significantly decreased the tumor blood flow and the active area of the tumor vessel. We concluded that talaporfin sodium-based PDT induces the shutdown of existing tumor vessels via the RhoA/ROCK pathway by activating the Rho-GTP pathway and decreasing the tumor blood flow.

Nucleolus-Targeted Photodynamic Anticancer Therapy Using Renal-Clearable Carbon Dots

Photodynamic therapy (PDT), which utilizes light excited photosensitizers (PSs) to generate reactive oxygen species (ROS) and consequently ablate cancer cells or diseased tissue, has attracted a great deal of attention in the last decades due to its unique advantages. In order to further enhance PDT effect, PSs are functionalized to target specific sub-cellular organelles, but most PSs cannot target nucleolus, which is demonstrated as a more efficient and ideal site for cancer treatment. Here, an effective carbon dots (C-dots) photosensitizer with intrinsic nucleolus-targeting capability, for the first time, is synthesized, characterized, and employed for in vitro and in vivo image-guided photodynamic anticancer therapy with enhanced treatment performance at a low dose of PS and light irradiation. The C-dots possess high ROS generation efficiency and fluorescence quantum yield, excellent in vitro and in vivo biocompatibility, and rapid renal clearance, endowing it with a great potential for future translational research.

Near-infrared-excited upconversion photodynamic therapy of extensively drug-resistant Acinetobacter baumannii based on lanthanide nanoparticles

Extensively drug-resistant Acinetobacter baumannii (XDR-AB) has raised considerable concerns due to its mortal damage to humans and its high transmission rate of infections in hospitals. However, current antibiotics not only show poor anti-infection effects in vivo but also frequently cause high nephrotoxicity and neurotoxicity. Herein, we report a near-infrared (NIR) light-initiated antimicrobial photodynamic therapy (aPDT) to effectively treat in vivo XDR-AB infections based on photosensitizer (PS) loaded upconversion nanoparticles (UCNPs, LiYF₄:Yb/Er). Such nanoagents feature robust NIR triggered UC luminescence and high-efficiency energy transfer from UCNPs to the loaded PS, thereby allowing NIR-triggered generation of reactive oxygen species (ROS) for destroying the bacterial cell membrane. This strategy permits a high antibacterial activity against XDR-AB, resulting in a decline of 4.72 log₁₀ in viability at a dose of 50 μg mL^-1 UCNPs-PVP-RB with 980 nm laser irradiation (1 W cm^-2). More significantly, we can achieve excellent therapeutic efficacy against deep-tissue (about 5 mm) XDR-AB infections without causing any side effects in the murine model. In brief, such NIR-activated aPDT may open up new avenues for treating various deep-tissue intractable infections.

Two-Dimensional Theranostic Nanomaterials in Cancer Treatment: State of the Art and Perspectives

As the combination of therapies enhances the performance of biocompatible materials in cancer treatment, theranostic therapies are attracting increasing attention rather than individual approaches. In this review, we describe a variety of two-dimensional (2D) theranostic nanomaterials and their efficacy in ablating tumors. Though many literature reports are available to demonstrate the potential application of 2D nanomaterials, we have reviewed here cancer-treating therapies based on such multifunctional nanomaterials abstracting the content from literature works which explain both the in vitro and in vivo level of applications. In addition, we have included a discussion about the future direction of 2D nanomaterials in the field of theranostic cancer treatment.

In Vivo Photodynamic Therapy With a Lipophilic Zinc(II) Phthalocyanine Inhibits Colorectal Cancer and Induces a Th1/CD8 Antitumor Immune Response

BACKGROUND AND OBJECTIVES

Photodynamic therapy (PDT) is an antitumor procedure clinically approved for the treatment of different cancer types. Despite strong efforts and promising results in this field, PDT has not yet been approved by any regulatory authority for the treatment of colorectal cancer, one of the most prevalent gastrointestinal tumors. In the search of novel therapeutic strategies, we examined the in vivo effect of PDT with a lipophilic phthalocyanine (Pc9) encapsulated into polymeric poloxamine micelles (T1107) in a murine colon carcinoma model.

STUDY DESIGN/MATERIALS AND METHODS

In vivo assays were performed with BALB/c mice challenged with CT26 cells. Pc9 tumor uptake was evaluated with an in vivo imaging system. Immunofluorescence, western blot, and flow cytometry assays were carried out to characterize the activation of apoptosis and an antitumor immune response.

RESULTS

Pc9-T1107 effectively delayed tumor growth and prolonged mice survival, without generating systemic or tissue-specific toxicity. The induction of an apoptotic response was characterized by a decrease in the expression levels of Bcl-X_L , Bcl-2, procaspase 3, full length Bid, a significant increment in the amount of active caspase-3 and the detection of PARP-1 cleavage. Infiltration of CD8⁺ CD107a⁺ T cells and higher levels of interferon-γ and tumor necrosis factor-α were also found in PDT-treated tumors.

CONCLUSIONS

Pc9-T1107 PDT treatment reduced tumor growth, inducing an apoptotic cell death and activating an immune response. Lasers Surg. Med. © 2020 Wiley Periodicals LLC.

Review: Organic nanoparticle based active targeting for photodynamic therapy treatment of breast cancer cells

Targeted Photodynamic therapy (TPDT) is a non-invasive and site-specific treatment modality, which has been utilized to eradicate cancer tumour cells with photoactivated chemicals or photosensitizers (PSs), in the presence of laser light irradiation and molecular tissue oxygen. Breast cancer is the commonest cancer among women worldwide and is currently treated using conventional methods such as chemotherapy, radiotherapy and surgery. Despite the recent advancements made in PDT, poor water solubility and non-specificity of PSs, often affect the overall effectivity of this unconventional cancer treatment. With respect to conventional PS obstacles, great strides have been made towards the application of targeted nanoparticles in PDT to resolve these limitations. Therefore, this review provides an overview of scientific peer reviewed published studies in relation to functionalized organic nanoparticles (NPs) for effective TPDT treatment of breast cancer over the last 10 years (2009 to 2019). The main aim of this review is to highlight the importance of organic NP active based PDT targeted drug delivery systems, to improve the overall biodistribution of PSs in breast cancer tumour's.

Radiolabeling, In Vitro Cell Uptake, and In Vivo Photodynamic Therapy Potential of Targeted Mesoporous Silica Nanoparticles Containing Zinc Phthalocyanine

Photodynamic therapy (PDT) is a noninvasive therapy based on the photodynamic effect. In this study, we sought to determine intracellular uptake and in vivo photodynamic therapy potential of Zn phthalocyanine-loaded mesoporous silica nanoparticles (MSNP5) against pancreatic cancer cells. MSNP5 were labeled with ¹³¹I; the radiolabeling efficiency was found to 95.5 ± 1.2% in pH 9 and 60 min reaction time. Besides, the highest intracellular uptake yields of ¹³¹I-MSNP5 nanoparticles in MIA PaCa-2, AsPC-1, and PANC-1 cells were determined as 43.9 ± 3.8%, 41.8 ± 0.2%, and 37.9 ± 1.3%, respectively, at 24 h incubation time. In vivo PDT studies were performed with subcutaneous xenograft cancer model nude mice with AsPC-1 pancreatic cancer cells. For photodynamic therapy, 685 nm red laser light 100 J/cm² light dose using and 5-20 μM ZnPc containing MSNP5 concentrations were applied. Histopathological studies revealed that the ratio of necrosis in tumor tissue was higher in the treatment group than the control groups.

Receptor-Targeted Photodynamic Therapy of Glucagon-Like Peptide 1 Receptor-Positive Lesions

Treatment of hyperinsulinemic hypoglycemia is challenging. Surgical treatment of insulinomas and focal lesions in congenital hyperinsulinism is invasive and carries major risks of morbidity. Medication to treat nesidioblastosis and diffuse congenital hyperinsulinism has varying efficacy and causes significant side effects. Here, we describe a novel method for therapy of hyperinsulinemic hyperglycemia, highly selectively killing β-cells by receptor-targeted photodynamic therapy (rtPDT) with exendin-4-IRDye700DX, targeting the glucagon-like peptide 1 receptor (GLP-1R). Methods: A competitive binding assay was performed using Chinese hamster lung (CHL) cells transfected with the GLP-1R. The efficacy and specificity of rtPDT with exendin-4-IRDye700DX were examined in vitro in cells with different levels of GLP-1R expression. Tracer biodistribution was determined in BALB/c nude mice bearing subcutaneous CHL-GLP-1R xenografts. Induction of cellular damage and the effect on tumor growth were analyzed to determine treatment efficacy. Results: Exendin-4-IRDye700DX has a high affinity for the GLP-1R, with a half-maximal inhibitory concentration of 6.3 nM. rtPDT caused significant specific phototoxicity in GLP-1R–positive cells (2.3% ± 0.8% and 2.7% ± 0.3% remaining cell viability in CHL-GLP-1R and INS-1 cells, respectively). The tracer accumulates dose-dependently in GLP-1R–positive tumors. In vivo, rtPDT induces cellular damage in tumors, shown by strong expression of cleaved caspase-3, and leads to a prolonged median survival of the mice (36.5 vs. 22.5 d, respectively; P < 0.05). Conclusion: These data show in vitro as well as in vivo evidence of the potency of rtPDT using exendin-4-IRDye700DX. This approach might in the future provide a new, minimally invasive, highly specific treatment method for hyperinsulinemic hypoglycemia.

Utility of Photodynamic Therapy in Dentistry: Current Concepts

The significant growth in scientific and technological advancements within the field of dentistry has resulted in a wide range of novel treatment modalities for dentists to use. Photodynamic therapy (PDT) is an emerging, non-invasive treatment method, involving photosensitizers, light of a specific wavelength and the generation of singlet oxygen and reactive oxygen species (ROS) to eliminate unwanted eukaryotic cells (e.g., malignancies in the oral cavity) or pathogenic microorganisms. The aim of this review article is to summarize the history, general concepts, advantages and disadvantages of PDT and to provide examples for current indications of PDT in various subspecialties of dentistry (oral and maxillofacial surgery, oral medicine, endodontics, preventive dentistry, periodontology and implantology), in addition to presenting some images from our own experiences about the clinical success with PDT.

Sulphur doped carbon dots enhance photodynamic therapy via PI3K/Akt signalling pathway

OBJECTIVES

Photodynamic therapy (PDT) is a promising approach for cancer treatment, and the underlying signalling pathway changes has been carried out for studying the PDT mechanisms, but is majorly limited to organic photosensitizers (PSs). For the emerging nano-PSs typically possessing higher 1 O2 quantum yield, few mechanistic studies were carried out, which limited their further applications in clinical therapeutics. PI3K/Akt signalling pathway, a most frequently activated signalling network in cancers, could promote cancer cell survival, but was seldom reported in previous PDT studies mediated by nano-PSs.

MATERIALS AND METHODS

Sulphur doped carbon dots (S-CDs) was prepared via a hydrothermal synthetic route and was characterized by transmission electron microscopy, X-ray photoelectron spectroscopy and so on. CCK-8 assay and Annexin V/PI staining were performed to demonstrate the death of cancer cells, Western blot, RT-PCR and immunofluorescence were employed to explore the underlying mechanism, and variation of PI3K/Akt and other signalling pathways was detected by Western blot.

RESULTS

S-CDs was successfully synthesized, and it was much more efficient compared with classic organic PSs. S-CDs could induce cancer cell death through mitochondria mediated cell apoptosis with the imbalance of Bcl-2 family proteins and caspase cascade via several signalling pathways. Low concentration of S-CDs could effectively inhibit PI3K/Akt pathway and promote p38/JNK pathway, on one way inhibiting cancer cell survival and on the other way promoting cell apoptosis.

CONCLUSIONS

Herein, we found that S-CDs acted as an inhibitor of the PI3K/Akt pathway for efficient cancer cell killing, thus yielding in a higher PDT performance over the existing photosensitizers.

Polydopamine Coated PB-MnO2 Nanoparticles as an Oxygen Generator Nanosystem for Imaging-Guided Single-NIR-Laser Triggered Synergistic Photodynamic/Photothermal Therapy

Exploring a combined phototherapeutic strategy to overcome the limitations of a single mode therapy and inducing high anticancer efficiency is highly promising for precision cancer nanomedicine. However, a single-wavelength laser activates dual photothermal/photodynamic therapy (PTT/PDT) treatment is still a formidable challenge. Herein, we strategically design and fabricate a multifunctional theranostic nanosystem based on chlorin e6-functionalized polydopamine (PDA) coated prussian blue/manganese dioxide nanoparticles (PB-MnO₂@PDA-Ce6 NPs). Interestingly, the obtained PB-MnO₂@PDA NPs not only offer an effective delivery system for Ce6 but also provide strong optical absorption in the near-infrared range, endowing high antitumor efficacy of PTT. More importantly, the as-prepared PB-MnO₂@PDA-Ce6 nanoagents exhibit an effective oxygen generation, superior reactive oxygen species (ROS), and outstanding photothermal conversion ability to greatly improve PTT and PDT treatments. As a result, both in vitro and in vivo treatments guided by MR imaging on liver cancer cells reveal the complete cell/tumor eradication under a single wavelength of 660 nm laser irradiation, implying the simultaneous synergistic PDT/PTT effects triggered by PB-MnO₂@PDA-Ce6 nanoplatform, which are much higher than individual treatment. Taken together, our phototherapeutic nanoagents exhibit an excellent therapeutic performance, which may act as a nanoplatform to find safe and clinically translatable routes to accelerate cancer therapeutics.

A non-aggregated silicon(IV) phthalocyanine-lactose conjugate for photodynamic therapy

To develop a highly efficient photosensitizer for photodynamic therapy (PDT), we have designed and synthesized a phthalocyanine-lactose conjugate (Pc-Lac) through axial modification of silicon(IV) phthalocyanine with lactose moieties. With the lactose substituents, Pc-Lac is highly hydrophilic and non-aggregated with efficient reactive oxygen species (ROS) generation in aqueous media. With these desirable properties, Pc-Lac shows high photocytotoxicity and cellular uptake toward HepG2 cells. In addition, in vivo fluorescence imaging shows that Pc-Lac could selectively remain at tumor site, leading to its enhanced photodynamic efficacy against H22 tumor-bearing mice. Therefore, Pc-Lac shows a great potential as a highly efficient molecular photosensitizer for PDT.

A promising anticancer drug: a photosensitizer based on the porphyrin skeleton

Photodynamic therapy (PDT) is a minimally invasive combination of treatments that treat tumors and other diseases by using photosensitizers, light and oxygen to produce cytotoxic reactive oxygen species (ROS) inducing tumor cell apoptosis. Photosensitizers are the key part of PDT for clinical application and experimental research, and most of them are porphyrin compounds at present. Due to their unique affinity for tumor tissues, porphyrins are not only excellent photosensitizers, but also good carriers to transport other active drugs into tumor tissues, which can exert synergistic anticancer effects of PDT and chemotherapy. This article reviews the clinical development of porphyrin photosensitizers and the research status of porphyrin containing bioactive groups. Finally, future perspectives and the current challenges of photosensitizers based on the porphyrin skeleton are discussed.

Water-Soluble NIR Absorbing and Emitting Indolizine Cyanine and Indolizine Squaraine Dyes for Biological Imaging

Organic dyes that absorb and emit in the near-infrared (NIR) region are potentially noninvasive, high-resolution, and rapid biological imaging materials. Indolizine donor-based cyanine and squaraine dyes with water-solubilizing sulfonate groups were targeted in this study due to strong absorptions and emissions in the NIR region. As previously observed for nonwater-soluble derivatives, the indolizine group with water-solubilizing groups retains a substantial shift toward longer wavelengths for both absorption and emission with squaraines and cyanines relative to classically researched indoline donor analogues. Very high quantum yields (as much as 58%) have been observed with absorption and emission >700 nm in fetal bovine serum. Photostability studies, cell culture cytotoxicity, and cell uptake specificity profiles were all studied for these dyes, demonstrating exceptional biological imaging suitability.

Near-Infrared Photoactive Aza-BODIPY: Thermally Robust and Photostable Photosensitizer and Efficient Electron Donor

We report herein the synthesis of aza-BODIPY substituted with strongly electron-donating p-(diphenylamino)phenyl substituents (p-Ph₂ N-) at 3,5-positions. The presence of p-Ph₂ N- groups lowers the energy of the singlet excited state (E_s ) to 1.48 eV and induces NIR absorption with λ_abs at 789 nm in THF. The compound studied is weakly emissive with the emission band (λ_f ) at 837 nm and with the singlet lifetime (τ_S ) equal to 100 ps. Nanosecond laser photolysis experiments of the aza-BODIPY in question revealed T₁ →T_n absorption spanning from ca. 350-550 nm with the triplet lifetime (τ_T ) equal to 21 μs. By introducing a heavy atom (Br) into the structure of the aza-BODIPY, we managed to turn it into a NIR operating photosensitizer. The photosensitized oxygenation of the model compound-diphenylisobenzofuran (DPBF)-proceedes via Type I and/or Type III mechanism without formation of singlet oxygen (¹ O₂ ). As estimated by CV/DPV measurements, the p-Ph₂ N- substituted aza-BODIPYs studied exhibits oxidation processes at relatively low oxidation potentials (E_ox ¹ ), pointing to the very good electron-donating properties of these molecules. Extremely high photostability and thermal robustness up to approximately 300 °C are observed for the p-Ph₂ N- substituted aza-BODIPYs.

A Dinuclear Ruthenium(II) Complex Excited by Near-Infrared Light through Two-Photon Absorption Induces Phototoxicity Deep within Hypoxic Regions of Melanoma Cancer Spheroids

The dinuclear photo-oxidizing Ru^II complex [{Ru(TAP₂)}₂(tpphz)]⁴⁺ (TAP = 1,4,5,8- tetraazaphenanthrene, tpphz = tetrapyrido[3,2-a:2′,3′-c:3″,2′′-h:2‴,3′′′-j]phenazine), 1⁴⁺, is readily taken up by live cells localizing in mitochondria and nuclei. In this study, the two-photon absorption cross section of 1⁴⁺ is quantified and its use as a two-photon absorbing phototherapeutic is reported. It was confirmed that the complex is readily photoexcited using near-infrared, NIR, and light through two-photon absorption, TPA. In 2-D cell cultures, irradiation with NIR light at low power results in precisely focused phototoxicity effects in which human melanoma cells were killed after 5 min of light exposure. Similar experiments were then carried out in human cancer spheroids that provide a realistic tumor model for the development of therapeutics and phototherapeutics. Using the characteristic emission of the complex as a probe, its uptake into 280 μm spheroids was investigated and confirmed that the spheroid takes up the complex. Notably TPA excitation results in more intense luminescence being observed throughout the depth of the spheroids, although emission intensity still drops off toward the necrotic core. As 1⁴⁺ can directly photo-oxidize DNA without the mediation of singlet oxygen or other reactive oxygen species, phototoxicity within the deeper, hypoxic layers of the spheroids was also investigated. To quantify the penetration of these phototoxic effects, 1⁴⁺ was photoexcited through TPA at a power of 60 mW, which was progressively focused in 10 μm steps throughout the entire z-axis of individual spheroids. These experiments revealed that, in irradiated spheroids treated with 1⁴⁺, acute and rapid photoinduced cell death was observed throughout their depth, including the hypoxic region.

Ag-Conjugated graphene quantum dots with blue light-enhanced singlet oxygen generation for ternary-mode highly-efficient antimicrobial therapy

The increasing prevalence of antibiotic resistance highlights the need for new antibacterial drugs and, in particular, the development of alternative approaches such as photodynamic therapy (PDT) and photothermal therapy (PTT) to manage this growing issue. In the present study, a broad-spectrum antibacterial system was produced in which Ag nanoparticle-conjugated graphene quantum dots (GQD-AgNP) were utilised as a blue light-enhanced nanotherapeutic for efficient ternary-mode antimicrobial therapy. The successful conjugation of AgNPs onto the surface of GQDs can significantly improve the production of reactive oxygen species in light-activatable GQDs and the transformation of light energy to hyperthermia with high efficiency. There was a remarkable increase in the sample temperature of nearly 40 °C via photoexcitation after only 10 min of 450 nm laser exposure (14.2 mW cm^-2). The hybrids exhibited much more efficient bactericidal capability against both Gram-negative and Gram-positive bacteria compared with GQDs alone, using 450 nm light irradiation. This is likely a consequence of their enhanced PDT, concomitant PTT, and the synergistic function of AgNPs. The antibacterial mechanism of the new-style nanocomposites was found to irreversibly destroy the bacterial membrane structure, leading to the leaking out of the cytoplasmic contents and the death of the bacteria. At low doses, the biocompatible GQD-AgNP hybrids promoted healing in bacteria-infected rat wounds, with negligible adverse impact to the normal tissue, indicating a promising future for combined photodynamic and photothermal antibacterial applications in clinical medicine.

Smart use of “ping-pong” energy transfer to improve the two-photon photodynamic activity of an Ir(iii) complex

A two-photon excited “Ping-Pong” type energy transfer process is for the first time disclosed for enhancing two-photon PDT.

Peroxynitrite (ONOO−) generation from the HA-TPP@NORM nanoparticles based on synergistic interactions between nitric oxide and photodynamic therapies for elevating anticancer efficiency

Due to biological safety and negligible toxicity, nitric oxide (NO) therapy has gained increasing interest in the field of cancer therapy during the past few years.

Fe-TCPP@CS nanoparticles as photodynamic and photothermal agents for efficient antimicrobial therapy

Photodynamic and photothermal agents for efficient antimicrobial therapy.

A New Optical Method for Online Monitoring of the Light Dose and Dose Profile in Photodynamic Therapy

BACKGROUND AND OBJECTIVES

Photodynamic therapy (PDT) has gained widespread popularity in the last decades because of its distinctive advantages over the other commonly used cancer treatments. PDT dosimetry is a crucial factor in achieving a good optimization of PDT treatment planning. PDT dosimetry is a complex task since light dose as well as photosensitizer and oxygen concentrations in tissue need to be measured (ideally continuously) to be able to fully characterize the biological response. Light dose in PDT is routinely measured by the optical fibers that provide dose data at a limited number of discrete points and are not able to capture spatial dose profiles. The objective of this study is to propose and develop a new optical method for online monitoring of the dose profile data for PDT.

STUDY DESIGN/MATERIALS AND METHODS

Using the digital holography technique, first, the general sketch of an experimental setup for PDT light dosimetry is provided. The theory behind the proposed method for using the experimental setup in PDT light dosimetry is fully described, and its limits of validity are determined. In a proof of principle study, the ability of the method for online monitoring of the absorbed light dose profile in PDT is evaluated by a simple experimental setup.

RESULTS

The experimental results confirm the usefulness of the proposed method in providing continuous online dose profiles. The absorbed light dose profiles from an infrared light source in a quartz cell containing water are measured and shown. The depth-dose curves are extracted and it is shown that how these dosimetric data can be used for assisting the physicians in determining the appropriate spatiotemporal characteristics for treating the infected tissues and solid tumors with the required light dose amounts. A conversion relation is also derived for transforming the measured light dose with the proposed method to the most frequently used dose values by PDT practitioners, in terms of light power per square area.

CONCLUSIONS

There is no restriction in using the method with other commonly used light sources in PDT, like light-emitting diodes and filtered lamps, with different wavelengths in visible or infrared regions of the spectrum. More complex experimental setups can be used in future studies to study the role of accumulated photosensitizers in malignant tissues. The proposed method in this study can also be used for light dose monitoring in other biomedical applications, where light is used for treating special diseases, and patients must receive sufficient amounts of light dose. Lasers Surg. Med. © 2019 Wiley Periodicals, Inc.

Chloromethyl-modified Ru(ii) complexes enabling large pH jumps at low concentrations through photoinduced hydrolysis

Photo-induced hydrolysis of benzyl chlorides was first utilized to fabricate PAGs with high photoacid quantum yields and large photoacid capacities.

Photoacid generators (PAGs) are finding increasing applications in spatial and temporal modulation of biological events in vitro and in vivo. In these applications, large pH jumps at low PAG concentrations are of great importance to achieve maximal expected manipulation but minimal unwanted interference. To this end, both high photoacid quantum yield and capacity are essential, where the capacity refers to the proton number that a PAG molecule can release. Up to now, most PAGs only produce one proton for each molecule. In this work, the hydrolysis reaction of benzyl chlorides was successfully leveraged to develop a novel type of PAG. Upon visible light irradiation, Ru(ii) polypyridyl complexes modified with chloromethyl groups can undergo full hydrolysis with photoacid quantum yield as high as 0.6. Depending on the number of the chloromethyl groups, the examined Ru(ii) complexes can release multiple protons per molecule, leading to large pH jumps at very low PAG concentrations, a feature particularly favorable for bio-related applications.