Evaluation of the 2-(1-Hexyloxyethyl)-2-devinyl pyropheophorbide (HPPH) mediated photodynamic therapy by macroscopic singlet oxygen modeling [J. Biophotonics 9, No. 11-12, 1344-1354 (2016)].
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ABSTRACT:
SUBMITTER: Penjweini R
PROVIDER: S-EPMC5550318 | biostudies-other | 2017 Mar
REPOSITORIES: biostudies-other
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Project description:Oxygen vacancy (OV) engineering in semiconductors can greatly enhance the separation of photo-induced electron-hole pairs, thereby enhancing the photocatalytic activity. Taking inspiration from this, we prepared a novel BiOBr-H/Rub2d composite by functionalizing OV-rich BiOBr (named BiOBr-H) with a carboxyl functionalized ruthenium photosensitizer (Ru(bpy)2C-pyCl2, abbreviated as Rub2d), which was then successfully applied for photodynamic therapy (PDT). Density functional theory (DFT) calculations confirmed efficient electron transfer from the Rub2d complex to the intermediate energy level of BiOBr-H under visible light irradiation. In vitro and in vivo studies demonstrated that BiOBr-H/Rub2d was a superior agent for photodynamic therapy compared with the free ruthenium complex. The theoretical and experimental data presented thus reveal for the first time that abundant OVs in BiOBr-H can significantly improve the photocatalytic activity of a photosensitizer, resulting in the generation of more reactive oxygen species to enhance PDT. The findings of this study thus offer a new strategy for the development of highly efficient cancer therapies.
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Project description:Interstitial photodynamic therapy (iPDT) with 5-aminolevulinic acid (ALA) is a possible alternative treatment for malignant brain tumors. Further evaluation is, however, required before it can be clinically applied. Computational simulation of the photophysical process in ALA-iPDT can offer a quantitative tool for understanding treatment outcomes, which depend on various variables related to clinical treatment conditions. We propose a clinical simulation method of ALA-iPDT for malignant brain tumors using a singlet oxygen (O12) model and O12 threshold to induce cell death. In this method, the amount of O12 generated is calculated using a photosensitizer photobleaching coefficient and O12 quantum yield, which have been measured in several previous studies. Results of the simulation using clinical magnetic resonance imaging data show the need to specify the insertion positions of cylindrical light diffusers and the level of light fluence. Detailed analysis with a numerical brain tumor model demonstrates that ALA-iPDT treatment outcomes depend on combinations of photobleaching and threshold values. These results indicate that individual medical procedures, including pretreatment planning and treatment monitoring, will greatly benefit from simulation of ALA-iPDT outcomes.
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Project description:Singlet oxygen is a primary cytotoxic agent in photodynamic therapy. We show that CeF3 nanoparticles, pure as well as conjugated through electrostatic interaction with the photosensitizer verteporfin, are able to generate singlet oxygen as a result of UV light and 8 keV X-ray irradiation. The X-ray stimulated singlet oxygen quantum yield was determined to be 0.79 ± 0.05 for the conjugate with 31 verteporfin molecules per CeF3 nanoparticle, the highest conjugation level used. From this result we estimate the singlet oxygen dose generated from CeF3-verteporfin conjugates for a therapeutic dose of 60 Gy of ionizing radiation at energies of 6 MeV and 30 keV to be (1.2 ± 0.7) × 10(8) and (2.0 ± 0.1) × 10(9) singlet oxygen molecules per cell, respectively. These are comparable with cytotoxic doses of 5 × 10(7)-2 × 10(9) singlet oxygen molecules per cell reported in the literature for photodynamic therapy using light activation. We confirmed that the CeF3-VP conjugates enhanced cell killing with 6 MeV radiation. This work confirms the feasibility of using X- or γ- ray activated nanoparticle-photosensitizer conjugates, either to supplement the radiation treatment of cancer, or as an independent treatment modality.
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Project description:Clinical applications of current photodynamic therapy (PDT) agents are often limited by their low singlet oxygen ((1)O2) quantum yields, as well as by photobleaching and poor biocompatibility. Here we present a new PDT agent based on graphene quantum dots (GQDs) that can produce (1)O2 via a multistate sensitization process, resulting in a quantum yield of ~1.3, the highest reported for PDT agents. The GQDs also exhibit a broad absorption band spanning the UV region and the entire visible region and a strong deep-red emission. Through in vitro and in vivo studies, we demonstrate that GQDs can be used as PDT agents, simultaneously allowing imaging and providing a highly efficient cancer therapy. The present work may lead to a new generation of carbon-based nanomaterial PDT agents with overall performance superior to conventional agents in terms of (1)O2 quantum yield, water dispersibility, photo- and pH-stability, and biocompatibility.
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Project description:Photodynamic therapy (PDT) is generally based on the generation of highly reactive singlet oxygen ((1)O(2)) through interactions of photosensitizer, light, and oxygen ((3)O(2)). These three components are highly interdependent and dynamic, resulting in variable temporal and spatial (1)O(2) dose deposition. Robust dosimetry that accounts for this complexity could improve treatment outcomes. Although the 1270 nm luminescence emission from (1)O(2) provides a direct and predictive PDT dose metric, it may not be clinically practical. We used (1)O(2) luminescence (or singlet oxygen luminescence (SOL)) as a gold-standard metric to evaluate potentially more clinically feasible dosimetry based on photosensitizer bleaching. We performed in vitro dose-response studies with simultaneous SOL and photosensitizer fluorescence measurements under various conditions, including variable (3)O(2), using the photosensitizer meta-tetra(hydroxyphenyl)chlorin (mTHPC). The results show that SOL was always predictive of cytotoxicity and immune to PDT's complex dynamics, whereas photobleaching-based dosimetry failed under hypoxic conditions. However, we identified a previously unreported 613 nm emission from mTHPC that indicates critically low (3)O(2) levels and can be used to salvage photobleaching-based dosimetry. These studies improve our understanding of PDT processes, demonstrate that SOL is a valuable gold-standard dose metric, and show that when used judiciously, photobleaching can serve as a surrogate for (1)O(2) dose.
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Project description:Therapeutic effects of photodynamic therapy (PDT) remain largely limited because of tumor hypoxia. Herein, we report safe and versatile nanocatalysts (NCs) for endogenous oxygen generation and imaging-guided enhanced PDT. The NCs (named as PSP) are prepared by coating Prussian blue (PB) with mesoporous silica to load photosensitizer (zinc phthalocyanine, ZnPc), followed by the modification of polyethylene glycol chains. The inner PB not only acts like a catalase for hydrogen peroxide decomposition but also serves as a photothermal agent to increase the local temperature and then speed up the oxygen supply under near-infrared irradiation. The loaded ZnPc can immediately transform the formed oxygen to generate cytotoxic singlet oxygen upon the same laser irradiation due to the overlapped absorption between PB and ZnPc. Results indicate that the PSP-ZnPc (PSPZP) NCs could realize the photothermally controlled improvement of hypoxic condition in cancer cells and tumor tissues, therefore demonstrating enhanced cancer therapy by the incorporation of PDT and photothermal therapy.
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Project description:Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus has been on a rampage for more than two years. Vaccines in combination with neutralizing antibodies (NAbs) against SARS-CoV-2 carry great hope in the treatment and final elimination of coronavirus disease 2019 (COVID-19). However, the relentless emergence of variants of concern (VOC), including the most recent Omicron variants, presses for novel measures to counter these variants that often show immune evasion. Hereby we developed a targeted photodynamic approach to neutralize SARS-CoV-2 by engineering a genetically encoded photosensitizer (SOPP3) to a diverse list of antibodies targeting the wild-type (WT) spike protein, including human antibodies isolated from a 2003 Severe acute respiratory syndrome (SARS) patient, potent monomeric and multimeric nanobodies targeting receptor-binding domain (RBD), and non-neutralizing antibodies (non-NAbs) targeting the more conserved N-terminal domain (NTD). As confirmed by pseudovirus neutralization assay, this targeted photodynamic approach significantly increased the efficacy of these antibodies, especially that of non-NAbs, against not only the WT but also the Delta strain and the heavily immune escape Omicron strain (BA.1). Subsequent measurement of infrared phosphorescence at 1270 nm confirmed the generation of singlet oxygen (1O2) in the photodynamic process. Mass spectroscopy assay uncovered amino acids in the spike protein targeted by 1O2. Impressively, Y145 and H146 form an oxidization "hotspot", which overlaps with the antigenic "supersite" in NTD. Taken together, our study established a targeted photodynamic approach against the SARS-CoV-2 virus and provided mechanistic insights into the photodynamic modification of protein molecules mediated by 1O2.
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