ABSTRACT: To impart effective cellular damage via photodynamic therapy (PDT), it is vital to deliver the appropriate light dose and photosensitizer concentration, and to monitor the PDT dose delivered at the site of interest. In vivo monitoring of photosensitizers has in large part relied on their fluorescence emission. Palladium-containing photosensitizers have shown promising clinical results by demonstrating near full conversion of light to PDT activity at the cost of having undetectable fluorescence. We demonstrate that, through the coupling of plasmonic nanoparticles with palladium-photosensitizers, surface-enhanced Raman scattering (SERS) provides both reporting and monitoring capability to otherwise quiescent molecules. Nano-enabled SERS reporting of photosensitizers allows for the decoupling of the therapeutic and imaging mechanisms so that both phenomena can be optimized independently. Most importantly, the design enables the use of the same laser wavelength to stimulate both the PDT and imaging features, opening the potential for real-time dosimetry of photosensitizer concentration and PDT dose delivery by SERS monitoring.
Project description:Translocator protein (TSPO) 18 kDa overexpression has been observed in a large variety of human cancers, especially breast cancers. PK 11195, an isoquinoline analogue, is one of the ligands of highest TSPO binding affinity. Due to the long biological half life of our photosensitizers, there is a need to label them with a long lived radioisotope, for example I-124. Our objectives are to find translocator protein targeted photosensitizers for both tumor imaging (PET) and photodynamic therapy (PDT). I-PK 11195 is conjugated with the tumor avid photosensitizer HPPH. We find that those two tumor avid components complement each other and make the conjugate molecule even more tumor avid; compared to the photosensitizer itself, the conjugate is found to show improved PDT efficacy. It is concluded that I-PK 11195 can be a good vehicle to deliver radionuclide and photosensitizer to TSPO overexpressed tumor regions. Such conjugates could be useful for both tumor imaging (PET) and PDT.
Project description:Elucidation of upconversion nanoparticles (UCNPs) that can be excited by near-infrared (NIR) light is an interesting topic in the field of photodynamic therapy (PDT). However, the PDT efficiency of conventional UCNPs is limited due to the low quantum yield and overheating effect of the 980 nm light source. In this study, a light source with a wavelength of 808 nm was used as an excitation source for Nd-doped UCNPs to solve the overheating effect. UCNPs with a core@shell structure (NaYF4:Yb,Er,Nd@NaYF4:Yb,Nd) were synthesized to increase the upconversion emission efficiency. Dual-color emitting Er-doped UCNPs and dual photosensitizers (Chlorin e6 and Rose Bengal) were used for enhanced PDT. Each photosensitizer could absorb red and green emissions of the UCNPs to generate reactive oxygen species (ROS), respectively. The ROS generation in a dual photosensitizer system is significantly higher than that in a single photosensitizer system. Additionally, PDT induces immunogenic apoptosis. In this study, by utilizing a highly efficient PDT agent, PDT-induced apoptosis was studied by biomarker analysis.
Project description:Photodynamic therapy (PDT) involves photosensitizing agents that, in the presence of oxygen and light, initiate formation of cytotoxic reactive oxygen species (ROS). PDT commonly induces both apoptosis and autophagy. Previous studies with murine hepatoma 1c1c7 cells indicated that loss of autophagy-related protein 7 (ATG7) inhibited autophagy and enhanced the cytotoxicity of photosensitizers that mediate photodamage to mitochondria or the endoplasmic reticulum. In this study, we examined two photosensitizing agents that target lysosomes: the chlorin NPe6 and the palladium bacteriopheophorbide WST11. Irradiation of wild-type 1c1c7 cultures loaded with either photosensitizer induced apoptosis and autophagy, with a blockage of autophagic flux. An ATG7- or ATG5-deficiency suppressed the induction of autophagy in PDT protocols using either photosensitizer. Whereas ATG5-deficient cells were quantitatively similar to wild-type cultures in their response to NPe6 and WST11 PDT, an ATG7-deficiency suppressed the apoptotic response (as monitored by analyses of chromatin condensation and procaspase-3/7 activation) and increased the LD(50) light dose by > 5-fold (as monitored by colony-forming assays). An ATG7-deficiency did not prevent immediate lysosomal photodamage, as indicated by loss of the lysosomal pH gradient. However, unlike wild-type and ATG5-deficient cells, the lysosomes of ATG7-deficient cells recovered this gradient within 4 h of irradiation, and never underwent permeabilization (monitored as release of endocytosed 10-kDa dextran polymers). We propose that the efficacy of lysosomal photosensitizers is in part due to both promotion of autophagic stress and suppression of autophagic prosurvival functions. In addition, an effect of ATG7 unrelated to autophagy appears to modulate lysosomal photodamage.
Project description:Photodynamic therapy (PDT) has emerged as an alternative and promising noninvasive treatment for cancer as well as non-cancer diseases, which involves the uptake of photosensitizers (PSs) by cancer cells followed by irradiation. The use of nanomaterials as carriers of PSs is a very promising approach to improve the development of PDT in clinical medicine. In this study, a novel folic acid-conjugated graphene oxide (GO) was strategically designed and prepared as targeting drug delivery system to achieve higher specificity. The second generation photosensitizer (PS) Chlorin e6 (Ce6) was effectively loaded into the system via hydrophobic interactions and ?-? stacking. The nanocarriers can significantly increase the accumulation of Ce6 in tumor cells and lead to a remarkable photodynamic efficacy on MGC803 cells upon irradiation. These suggested that folic acid-conjugated GO loaded Ce6 had great potential as effective drug delivery system in targeting PDT.
Project description:Photodynamic therapy (PDT) involves the uptake of photosensitizers by cancer cells and the irradiation of a light with a specific wavelength to trigger a series of photochemical reactions based on the generation of reactive oxygen, leading to cancer cell death. PDT has been widely used in various fields of biomedicine. However, the molecular events of the cancer cell nucleus during the PDT process are still unclear. In this work, a nuclear-targeted gold nanorod Raman nanoprobe combined with surface-enhanced Raman scattering spectroscopy (SERS) was exploited to investigate the dynamic intranuclear molecular changes of B16 cells (a murine melanoma cell line) treated with a photosensitizer (Chlorin e6) and the specific light (650 nm). The SERS spectra of the cell nucleus during the PDT treatment were recorded in situ and the spectroscopic analysis of the dynamics of the nucleus uncovered two main events in the therapeutic process: the protein degradation and the DNA fragmentation. We expect that these findings are of vital significance in having a better understanding of the PDT mechanism acting on the cancer cell nucleus and can further help us to design and develop more effective therapeutic platforms and methods.
Project description:Photosensitizer fluorescence excited by photodynamic therapy (PDT) treatment light can be used to monitor the in vivo concentration of the photosensitizer and its photobleaching. The temporal integral of the product of in vivo photosensitizer concentration and light fluence is called PDT dose, which is an important dosimetry quantity for PDT. However, the detected photosensitizer fluorescence may be distorted by variations in the absorption and scattering of both excitation and fluorescence light in tissue. Therefore, correction of the measured fluorescence for distortion due to variable optical properties is required for absolute quantification of photosensitizer concentration. In this study, we have developed a four-channel PDT dose dosimetry system to simultaneously acquire light dosimetry and photosensitizer fluorescence data. We measured PDT dose at four sites in the pleural cavity during pleural PDT. We have determined an empirical optical property correction function using Monte Carlo simulations of fluorescence for a range of physiologically relevant tissue optical properties. Parameters of the optical property correction function for Photofrin fluorescence were determined experimentally using tissue-simulating phantoms. In vivo measurements of photosensitizer fluorescence showed negligible photobleaching of Photofrin during the PDT treatment, but large intra- and inter-patient heterogeneities of in vivo Photofrin concentration are observed. PDT doses delivered to 22 sites in the pleural cavity of 8 patients were different by 2.9 times intra-patient and 8.3 times inter-patient.
Project description:Photodynamic therapy (PDT) represents a minimally invasive and highly localized treatment strategy to ablate tumors with few side effects. In PDT, photosensitizers embedded within tumors are activated by light and undergo intersystem crossing, followed by energy transfer to molecular oxygen, resulting in the production of toxic singlet oxygen (1O2). Previously, we reported a robust, linear tetrapyrrole palladium(II) complex, Pd[DMBil1], characterized by its facile and modular synthesis, broad absorption profile, and efficient 1O2 quantum yield of ΦΔ = 0.8 in organic media. However, the insolubility of this porphyrinoid derivative in aqueous solution prevents its use under biologically relevant conditions. In this work, we report the synthesis of Pd[DMBil1]-PEG750, a water-soluble dimethylbiladiene derivative that is appended with a poly(ethylene) glycol (PEG) functionality. Characterization of this complex shows that this PEGylated biladiene architecture maintains the attractive photophysical properties of the parent complex under biologically relevant conditions. More specifically, the absorption profile of Pd[DMBil1]-PEG750 closely matches that of Pd[DMBil1] and obeys the Beer-Lambert Law, suggesting that the complex does not aggregate under biologically relevant conditions. Additionally, the emission spectrum of Pd[DMBil1]-PEG750 retains the fluorescence and phosphorescence features characteristic of Pd[DMBil1]. Importantly, the PEGylated photosensitizer generates 1O2 with ΦΔ = 0.57, which is well within the range to warrant interrogation as a potential PDT agent for treatment of cancer cells. The Pd[DMBil1]-PEG750 is biologically compatible, as it is taken up by MDA-MB-231 triple negative breast cancer (TNBC) cells and has an effective dose (ED50) of only 0.354 μM when exposed to λex > 500 nm light for 30 min. Impressively, the lethal dose (LD50) of Pd[DMBil1]-PEG750 without light exposure was measured to be 1.87 mM, leading to a remarkably high phototoxicity index of ∼5300, which is vastly superior to existing photosensitizers that form the basis for clinical PDT treatments. Finally, through flow cytometry experiments, we show that PDT with Pd[DMBil1]-PEG750 induces primarily apoptotic cell death in MDA-MB-231 cells. Overall these results demonstrate that Pd[DMBil1]-PEG750 is an easily prepared, biologically compatible, and well-tolerated photochemotherapeutic agent that can efficiently drive the photoinduced apoptotic death of TNBC cells.
Project description:A major challenge in photodynamic therapy (PDT) is the development of new tumor-targeting photosensitizers. The tumor-specific activation is considered to be an effective strategy for designing these photosensitizers. Herein, we describe a novel tumor-pH-responsive supramolecular photosensitizer, LDH-ZnPcS8, which is not photoactive under neutral conditions but is precisely and efficiently activated in a slightly acidic environment (pH 6.5). LDH-ZnPcS8 is prepared by using a simple coprecipitation method based on the electrostatic interaction between negatively charged octasulfonate-modified zinc(II) phthalocyanine (ZnPcS8) and cationic hydroxide layers of layered double hydroxide (LDH). The in vitro photodynamic activities of LDH-ZnPcS8 in cancer cells are dramatically enhanced relative to those of ZnPcS8 alone. The results of in vivo fluorescence imaging demonstrate that the nanohybrid is activated in tumor tissues, where it displays an excellent PDT effect resulting in 95.3% tumor growth inhibition. Furthermore, the minimal skin phototoxicity of LDH-ZnPcS8 highlights its high potential as a novel photosensitizer for activatable PDT.
Project description:We present a novel high-throughput microfluidic platform that enables the evaluation of the anticancer efficacy of photodynamic therapy (PDT) drugs over multiple microenvironmental factors. PDT is uniquely complex, originating from its dependence on three separate but essential elements: drug (also called photosensitizer), oxygen, and light. Thus, obtaining a reliable evaluation of PDT efficacy is highly challenging, requiring considerable effort and time to evaluate all three interdependent parameters. In this paper, we report a high-throughput efficacy screening platform that we implemented by developing microfluidic components that individually control basic PDT elements (photosensitizer concentrations, oxygen levels, and light fluence) and then integrating them into a single triple-layer device. The integrated microfluidic chip consists of an array of small compartments, each corresponding to a specific combination of these three variables. This allows for more than 1000 different conditions being tested in parallel. Cancer cells are cultured within the device, exposed to different PDT conditions, and then monitored for their viability using live/dead fluorescence staining. The entire screening assay takes only 1 hour, and the collected PDT outcomes (cell viability) for combinatorial screening are analysed and reported as traditional dose-response curves or 3D bubble charts using custom software. As a proof of concept, methylene blue is adopted as a photosensitizer and its drug efficacy on C6 glioma cells has been successfully evaluated for a total of 324 PDT conditions using the fabricated chip. This platform can facilitate not only the development of new photosensitizers but also the optimization of current PDT protocols.
Project description:We examined a series of selenorhodamines with amide and thioamide functionality at the 5-position of a 9-(2-thienyl) substituent on the selenorhodamine core for their potential as photosensitizers for photodynamic therapy (PDT) in P-glycoprotein (P-gp) expressing cells. These compounds were examined for their photophysical properties (absorption, fluorescence, and ability to generate singlet oxygen), for their uptake into Colo-26 cells in the absence or presence of verapamil, for their dark and phototoxicity toward Colo-26 cells, for their rates of transport in monolayers of multidrug-resistant, P-gp-overexpressing MDCKII-MDR1 cells, and for their colocalization with mitochondrial specific agents in Colo-26 cells. Thioamide derivatives 16b and 18b were more effective photosensitizers than amide derivatives 15b and 17b. Selenorhodamine thioamides 16b and 18b were useful in a combination therapy to treat Colo-26 cells in vitro: a synergistic therapeutic effect was observed when Colo-26 cells were exposed to PDT and treatment with the cancer drug doxorubicin.