Imaging assessment of photosensitizer emission induced by radionuclide-derived Cherenkov radiation using charge-coupled device optical imaging and long-pass filters

BACKGROUND Radionuclides produce Cherenkov radiation(CR),which can potentially activate photosensitizers(PSs)in phototherapy.Several groups have studied Cherenkov energy transfer to PSs using optical imaging;however,cost-effectively identifying whether PSs are excited by radionuclide-derived CR and detecting fluorescence emission from excited PSs remain a challenge.Many laboratories face the need for expensive dedicated equipment.AIM To cost-effectively confirm whether PSs are excited by radionuclide-derived CR and distinguish fluorescence emission from excited PSs.METHODS The absorbance and fluorescence spectra of PSs were measured using a microplate reader and fluorescence spectrometer to examine the photo-physical properties of PSs.To mitigate the need for expensive dedicated equipment and achieve the aim of the study,we developed a method that utilizes a chargecoupled device optical imaging system and appropriate long-pass filters of different wavelengths(manual sequential application of long-pass filters of 515,580,645,700,750,and 800 nm).Tetrakis(4-carboxyphenyl)porphyrin(TCPP)was utilized as a model PS.Different doses of copper-64(^(64)CuCl_(2))(4,2,and 1 mCi)were used as CR-producing radionuclides.Imaging and data acquisition were performed 0.5 h after sample preparation.Differential image analysis was conducted by using ImageJ software(National Institutes of Health)to visually evaluate TCPP fluorescence.RESULTS The maximum absorbance of TCPP was at 390-430 nm,and the emission peak was at 670 nm.The CR and CRinduced TCPP emissions were observed using the optical imaging system and the high-transmittance long-pass filters described above.The emission spectra of TCPP with a peak in the 645-700 nm window were obtained by calculation and subtraction based on the serial signal intensity(total flux)difference between^(64)CuCl_(2)+TCPP and^(64)CuCl_(2).Moreover,the differential fluorescence images of TCPP were obtained by subtracting the^(64)CuCl_(2)image from the^(64)CuCl_(2)+TCPP image.The experimental results considering different^(64)CuCl_(2)doses showed a dosedependent trend.These results demonstrate that a bioluminescence imaging device coupled with different longpass filters and subtraction image processing can confirm the emission spectra and differential fluorescence images of CR-induced TCPP.CONCLUSION This simple method identifies the PS fluorescence emission generated by radionuclide-derived CR and can contribute to accelerating the development of Cherenkov energy transfer imaging and the discovery of new PSs.

Photoactivated Activities on Spodoptera litura Cell, Singlet Oxygen and Photostability of Photosensitizers

[Objective ]The aim of this study was to improve the photostability of pho-tosensitizers. [Method] 2,5-Diphenylthiophene and 2,5-dithienylethynylthiophene were synthesized by replacing thiophene rings of α-terthienyl （α-T） with benzene rings. Photoactivated activities on Spodoptera litura （SL） cells, singlet oxygen with UV and photostability of photosensitizers were investigated. [Result] The cytotoxicity of pho-tosensitizer 2,5-diphenylthiophene on SL cells was 0.22 and 0.16 μg/ml after treat-ment for 24 and 48 h, respectively, while that of 2,5-dithienylethynylthiophene on SL cells was 0.06 and 0.04 μg/ml. Singlet oxygen of 2,5-diphenylthiophene and 2,5-dithienylethynylthiophene was 1.047 5, 1.529 4 μg/mmol under UV, respectively. Degradation dynamic equations of 2,5-diphenylthiophene and 2,5-dithienylethynylthio-phene in methanol were Ct= 5.227 1e-0.006 1t, Ct= 5.084 2e-0.097 3t and half life was 111.79, 7.12 h. [Conclusion] Photosensitizer 2,5-diphenylthiophene has high singlet oxygen production ability, and high photoactivated cytotoxicity on SL cells under UV. Moreover, 2,5-diphenylthiophene has overcome the deficiency of photoactivated in-secticides, which is not applied directly in field because it degrades quickly in the environment.

Photosensitizer Nanoparticles Boost Photodynamic Therapy for Pancreatic Cancer Treatment

Patients with pancreatic cancer(PCa)have a poor prognosis apart from the few suitable for surgery.Photodynamic therapy(PDT)is a minimally invasive treatment modality whose efficacy and safety in treating unresectable localized PCa have been corroborated in clinic.Yet,it suffers from certain limitations during clinical exploitation,including insufficient photosensitizers(PSs)delivery,tumor-oxygenation dependency,and treatment escape of aggressive tumors.To overcome these obstacles,an increasing number of researchers are currently on a quest to develop photosensitizer nanoparticles(NPs)by the use of a variety of nanocarrier systems to improve cellular uptake and biodistribution of photosensitizers.Encapsulation of PSs with NPs endows them significantly higher accumulation within PCa tumors due to the increased solubility and stability in blood circulation.A number of approaches have been explored to produce NPs co-delivering multi-agents affording PDT-based synergistic therapies for improved response rates and durability of response after treatment.This review provides an overview of available data regarding the design,methodology,and oncological outcome of the innovative NPs-based PDT of PCa.

Advances in photosensitizer-related design for photodynamic therapy

Photodynamic therapy(PDT)is highly effective in treating tumors located near body surface,offering strong tumor suppression and low damage to normal tissue nearby.PDT is also effective for treating a number of other conditions.PDT not only provide a precise and selective method for the treatment of various diseases by itself,it can also be used in combination with other traditional therapies.Because PDT uses light as the unique targeting mechanism,it has simpler and more direct targeting capability than traditional therapies.The core material of a PDT system is the photosensitizer which converts light energy to therapeutic factors/substances.Different photosensitizers have their distinct characteristics,leading to different advantages and disadvantages.These could be enhanced or compensated by using proper PDT system.Therefore,the selected type of photosensitizer would heavily influence the overall design of a PDT system.In this article,we evaluated major types of inorganic and organic PDT photosensitizers,and discussed future research directions in the field.

Photocyanine:A novel and effective phthalocyanine-based photosensitizer for cancer treatment

As one of the three key components of photodynamic therapy(PDT),photosensitizers(PSs)greatly influence the photodynamic efficiency in the treatment of tumors.Photosensitizers with tetrapyrrole structure,such as porphyrins,chlorins and phthalocyanines,have been extensively investigated for PDT and some of them have already received clinical approval.However,only a few of porphyrin-based photosensitizers are available for clinical applications,and PDT has not received wide recognition in clinical practice.In this regard,PSs remain a limiting factor.Our research focuses on the rational design of new PSs.Photocyanine,a Zinc(Ⅱ)phthalo-cyanine(ZnPc)type photosensitizer with low dark toxicity and high single oxygen quantum yield,is one of the promising PSs candidates and currently being tested in clinical trials.Here,we present an overview on the development of Photocyanine,including its design,synthesis,purification,characterization and preclinical studies,wishing to contribute to the research of more promising PSs.

Doping [Ru(bpy)3]^(2+ )into metal-organic framework to facilitate the separation and reuse of noble-metal photosensitizer during CO2 photoreduction

It is desirable to develop highly efficient and sustainable catalytic systems for CO_(2) photoreduction using efficient heterogeneous photosensitizers(PSs);however,this remains a great challenge.In this study,we doped[Ru(bpy)3]^(2+) into UiO-metal-organic frameworks(MOFs)to facilitate the separation and reuse of noble metal PS.By simply adjusting the loading amount,a series of heterogeneous photoactive MOFs,namely,UiO-Ru-1,UiO-Ru-2,and UiO-Ru-3,were constructed to act as heterogeneous PSs to drive the efficient CO_(2) photoreduction under visible-light irradiation.Remarkably,UiO-Ru-2 exhibited the best photosensitizing ability among the prepared MOFs in sensitizing the iron quarterpyridine catalyst(C-l),and the CO yield reached as high as 171 mmol/g with ca.100%selectivity,which is a record value among all the MOF-based photocatalysts.This photoactive MOF can be recycled and reused three times without any obvious activity loss,signifying its good photochemical stability.Experimental investigations confirmed that the strong visible absorption,long-lived excited state,appropriate redox potential,good photocatalytic stability,and excellent collaboration with C-l were attributable to the superior catalytic activity.This work highlights an avenue for constructing heterogeneous PSs with excellent recyclability using MOF as the platform for efficient CO_(2) reduction.

Green Synthesis of New Tetra Schiff Bases and Bis-Azo Bis-Schiff Bases Derived from 2,6-Diaminopyridine as Promising Photosensitizers

Nine new tetra Schiff bases (M2 - M9) were prepared in moderate yields via the condensation of different aromatic amines and bis-Schiff base (M1) in microwave synthesizer. Also five new azo-Schiff bases (M16 - M20) were prepared by the condensation of (M1) with the azo-salicylaldehyde (M11 - M15) using the same method. The green synthesis by microwave irradiation was chosen as route due to its novelty, cleanliness, efficiency, time and solvent saving properties compared with the conventional methods which lack these advantages;such as time consume and wasting environment polluting organic solvents to achieve the same efficiency in synthesis. The prepared compounds which are believed by us to be competent as photosensitizers in photochemical systems were identified by IR and NMR spectroscopy besides elemental analysis.

Plant extracts as natural photosensitizers in photodynamic therapy:in vitro activity against human mammary adenocarcinoma MCF-7 cells

Objective: To examine three plant extracts [Lumnitzera racemosa(Combretaceae)(L.racemosa), Albizia procera(Fabaceae)(A.procera) and Cananga odorata(Annonaceae)] for their potential as source of photosensitizers in photodynamic therapy.Methods: Human mammary adenocarcinoma(MCF-7) cells were treated with the plant extracts, which were irradiated with 5.53 m W and 0.553 mW broadband light.Cell viability was assessed using MTT assay and induction of apoptosis was determined using terminal deoxynucleotidyl transferase-dUTP nick end labeling assay.Results: The crude ethanolic extracts, independently, were nontoxic against cancer and non-cancer cells but when irradiated with 5.53 mW broadband light, L.racemosa and A.procera extracts were cytotoxic against MCF-7 with IC_(50) of 11.63 mg/mL and10.73 mg/mL, respectively.With 0.553 mW broadband light, the IC_(50) values were higher at 17.14 mg/mL and 19.59 mg/mL, respectively.Photoactivated L.racemosa and A.procera extracts were found to be more cytotoxic against MCF-7 than the non-cancer cell line, human dermal fibroblast-neonatal.Moreover, the cytotoxicity of the extracts was mediated by apoptosis.Conclusions: Two of the plant extracts used, L.racemosa and A.procera were toxic and induced apoptosis to mammary cell adenocarcinoma, MCF-7 when photoactivated.These extracts were also more toxic to human cancer than non-cancer cell lines.

Change of photosensitizer fluorescence at its diffusion in viscous liquid flow

In this paper,the mathematical model of distribution of the injected compound in biological liquid flow has been described.It is considered that biological liquid contains a few phases such as water,peptides and cells.The injected compound(for example,photosensitizer)can interact with peptides and cells.At the time,viscosity of the biological liquid depends on pathology present in organism.The obtained distribution of the compound connects on changes of its fluorescence spectra which are registered during fluorescent diagnostics of tumors.It is obtained that the curves do not have monotonic nature.There is a sharp curves decline in the first few seconds after injection.Intensivity of curves rises after decreasing.It is especially pronounced for wavelength 590 nm and 580 nm(near the"transparency window"of biological tissues).Time of inflection point shifts from 8.4 s to 6.9 s for longer wavelength.However,difference between curves is little for di®erent viscosity means of the biological liquid.Thus,additional pathology present in organism does not impact to the results of in vivo biomedical investigations.

PEGylated liposomal photosensitizers as theranostic agents for dual-modal photoacoustic andffuorescence imaging-guided photodynamic therapy

The photosensitizer(PS)as photodynamic therapy(PDT)agent,can also serve as the contrast agent for dual-modalffuorescence imaging(FLI)and photoacoustic imaging(PAI)for precise cancer theranostics.In this study,the PAI capability of commercial PS,benzoporphyrin derivative monoacid ring-A(BPD)were examined and compared with that from the other PSs and dyes such as TPPS_(4),Cy5 dye and ICG.We discovered that BPD exhibited its advantage as contrast agent for PAI.Meanwhile,BPD can also serve as the contrast agent for enhanced FLI.In particular,the PEGylated nanoliposome(PNL)encapsulated BPD(LBPD)was produced for contrast enhanced dual-modal FLI and PAI and imaging-guided high-efficiency PDT.Enhanced FLI and PAI results demonstrated the significant accumulation of LBPD both within and among individual tumor during 24 h monitoring for in vivo experiment tests.In-vitro and in-vivo PDT tests were also performed,which showed that LBPD have higher PDT efficiency and can easily break the blood vessel of tumor tissues as compared to that from BPD.It was discovered that LBPD has great potentials as a diagnosis and treatment agent for dual-modal FLI and PAI-guided PDT of cancer.

Photoswitchable semiconducting polymer dots with photosensitizer molecule and photochromic molecule loading for photodynamic cancer therapy

Photodynamic therapy(PDT)is a new and rapidly developing treatment modality for dinical cancer therapy.Semiconductor polymer dots(Pdots)doped with photosensitizers have been successfully applied to PDT,and have made progress in the field of tumor therapy.However,the problems of severe photosensitivity and limited tisue penetration depth are needed to be solved during the implementation process of PDT.Here we developed the Pdots doped with photosensitizer molecule Chlorin e6(Ce6)and photochromic molecule 1,2-bis(2,4-dimethy1-5 phenyl-3-thiophene)-3,3,4,5-hexafuoro-1-cyclopentene(BTE)to construct a photoswitchable nanoplatform for PDT.The Ce6-BTE-doped Pdots were in the green region,and the tissue penetration depth was increased compared with most Pdots in the blue region.The reversible conversion of BTE under different light irradiation was utilized to regulate the photodynamic effect and solve the problem of photosensitivity.The prepared Ce6-BTE-doped Pdots had small size,excellent optical property,efficient ROS generation and good photoswitchable ability.The cellular uptake,cytotoxicity,and photodynamic effect of the Pdots were detected in human colon tumor cells.The experiments in vitro indicated that Ce6-BTE-doped Pdots could exert excellent photodynamic effect in ON state and reduce photosensitivity in OFF state.These results demonstrated that this nanoplatform holds the potential to be used in clinical PDT.

Orthogonal Aza-BODIPY–BODIPY dyad as heavy-atom free photosensitizer for photo-initiated antibacterial therapy

Photodynamic antibacterial therapy shows great potential in bacterial infection and the reactive oxygen species(ROS)production of the photosensitizers is crucial for the therapeutic e®ect.Introducing heavy atoms is a common strategy to enhance photodynamic performance,while dark toxicity can be induced to impede further clinical application.Herein,a novel halogen-free photosensitizer Aza-BODIPY-BODIPY dyad NDB with an orthogonal molecular conguration was synthesized for photodynamic antibacterial therapy.The absorption and emission peaks of NDB photosensitizer in toluene were observed at 703 nm and 744 nm,respectively.The°uorescence(FL)lifetime was measured to be 2.8 ns in toluene.Under 730 nm laser illumination,the ROS generation capability of NDB was 3-fold higher than that of the commercial ICG.After nanoprecipitation,NDB NPs presented the advantages of high photothermal conversion e±ciency(39.1%),good photostability,and excellent biocompatibility.More importantly,in vitro antibacterial assay conrmed that the ROS and the heat generated by NDB NPs could extirpate methicillin-resistant S.aureus e®ectively upon exposure to 730 nm laser,suggesting the potential application of NDB NPs in photo-initiated antibacterial therapy.

Photochemical Degradation of Phenols in Water Using Flavin-based Photosensitizers

A slightly modified method for 10-ethyl flavin was developed in the present study. The synthetic product was characterized by nuclear magnetic resonance(NMR) and mass spectrometry, and used to catalyze the photocatalytic degradation of phenol, 2, 4-dichlorophenoxyacetic acid, p-nitrophenol, 4-chlorophenol, 4-methoxyphenol, 4-chloro-2-methyl-phenoxyacetic acid and2, 4, 5-trichloro-phenoxyacetic acid. Both HPLC(high performance liquid chromatography) and GC-MS data suggested that all phenols were degraded in the presence of either flavin at micromolar concentrations under direct sun light. A rapid breakdown of the phenols was observed. The degradation efficiency was clearly dependent on phenol type. In a decreasing order of degradation efficiency over a 2-h period, the phenols were 4-chlorophenol and 4-methoxyphenol(-80%) > phenoxyacetic acids(60%-65%) > nitrophenol and phenol(-35%).

Preparation and Photodynamic Anti-tumor Activity of Magnetic Polylactic Acid Nanoparticles Loaded with Photosensitizer

A novel magnetic nanocarrier was strategically designed and successfully prepared.Photosensitizer 2,7,12,18-tetramethyl-3,8-di-(1-propoxyethyl)-13,17-bis-(3-hydroxypropyl)porphyrin(PHPP)was encapsulated into polylactic acid(PLA)-coated Fe3O4 nanoparticles.The diameter of nanocarrier is 30-50 nm by transmission electron micrograph(TEM).The encapsulation efficiency of photosensitizer is 27.98% calculated from UV-vis absorption spectra.The nanocarrier shows obvious photocytotoxic activity to Hela299 tumor cells in vitro.

Photochemical Degradation of Phenols in Water Using Flavin-Based Photosensitizers

Both flavin derivatives were successfully synthesized and characterized by NMR （nuclear magnetic resonance） and mass spectrometry. A slightly modified method for 10-ethyl flavin was developed. Both HPLC （high performance liquid chromatography） and GC-MS data suggested that all phenols were degraded in the presence of either flavin at micromolar concentrations under direct sun light. A rapid breakdown of the phenols with 35-80% degradation over the course of 2 h was observed. The degradation efficiency was clearly dependent on the phenol type. The rank order for the degradation efficiency over 2 h was 4-chlorophenol and 4-methoxyphenol （-80%） 〉 phenoxyacetic acids （60-65%） 〉 nitrophenol and phenol （-35%）.

A NEW PHOTOSENSITIZER SULFONATED ALUMINUM PHTHALOCYANINE:IN VITRO STUDY ON ITS PHOTODYNAMIC ACTION

The photosensitizing effects of sulfonated aluminum phthalocyanine on human liver cancer cells were studied by determining the kinetics of its cellular uptake, its state of aggregation therein and its photocytotoxicitic effect on these cells. Fluorescence methods were used to measure the cellular uptake in cell extracts and intact cells in monolayer. Results exhibited that the cellular uptake increases with the incubation time of sulfonated aluminum phthalocyanine (Alspc) and saturates at 24 hours. This relation was in coincidence with that between Alspc's photocytotoxic effect and the Alspc incubation time. Although the average Alspc concentration in cells is higher than the incubation concentration of Alspc, laser fluorescence experiments showed that the fluorescence peak of Alspc in cells incubated in higher concentration coincides with that of its aqueous solution of low concentration, suggesting that Alspc in cancer cells exists in monomer state. The results that lipid peroxidation in cells is enhanced by Alspc photosensitization reflected that it may be one of the mechanisms of cell damage. The photodamage on cells was also studied with 3T3 mouse cells (conversion), showing agreeable results to that with liver cancer cells, which suggests that Alspc's photocytotoxic effect is nonselective to cell types.

A Spin-orbit Coupling Study on the Quinoline-and Porphyrin-based Photosensitizers

The spin-orbit coupling（SOC） of four porphyrin- and quinoline-based compounds has been studied using Pauli-Breit SOC operator with one- and two-electron terms. The results revealed that the yield of singlet oxygen is affected by the spin-orbit coupling matrix element involving the emitting triplet and the perturbing singlet state. Investigated quinoline-based compounds have more high SOC values than those porphyrin-based compounds due to spin parallel electron pairs of oxygen. The open shell d8 of metal Pt can induce the stronger exchange interactions than the closed shell p6 of metal Mg, resulting in bigger SOC matrix element in quinoline-based Pt complex than in the quinoline-based Mg complex. Simultaneously, potential energy curves of the first excited sate and the first triplet sate have been calculated, which proves that all investigated complexes can induce singlet oxygen. These computational findings support quinolin-based compounds have high singlet oxygen yields and provide a rigorous basis for predicting the probability of singlet oxygen yields in plane-type molecules.

<i>In Vitro</i>Effects of Photodynamic Therapy with Three Photosensitizers on <i>Candida</i>spp from Complicated Vulvovaginitis and Asymptomatic Women

Aim: To evaluate photodynamic therapy (PDT) in vitro to reduce the growth of Candida spp, and its synergy with the antifungals fluconazole and ketoconazole for inhibition of resistant, DDS and susceptible isolates from asymptomatic carriers and with complicated vulvovaginitis. Methods: Between 2017 and 2020, we evaluated 230 women with vulvovaginal candidiasis and 400 asymptomatic. We obtained 130 positive cultures for Candida spp from vulvovaginitis and 94 asymptomatic. Yeasts were characterized by classical and molecular tests. Sensitivity to fluconazole and ketoconazole was evaluated by E-test. We used photodynamic light through blue LED, wavelengths between 450 to 470 nm, power of 260 mW, energy fluence of 270 J/cm2, for 15 minutes over all colonies of Candida spp. Methylene blue (MB) at 450 mg/mL, 2% gentian violet (VG) and 50 μM curcumin (CR) were used in association or not with LED irradiation. Suspensions of Candida spp of 106 CFU/mL, subjected to the different assays, were introduced in 96-well microplates, incubated for 48 hours at 35˚C and the readings at 530 nm. The samples were finally cultivated in Petri plates containing Sabouraud dextrose agar to assess the growth inhibition. All procedures were in triplicate. Results: C. albicans was prevalent in vulvovaginal candidiasis, however, we also isolated non-albicans species such as C. glabrata, C. tropicalis and C. parapsilosis. There was a substantial reduction (66.6% to 83.8%) of the CFU/mL of the isolates treated with FDT. Gentian violet at 2% alone reduced the growth of CFU/ml of Candida spp from 69% to 75%. Among isolates of vaginitis and asymptomatic carriers, after using FDT, we found a reduction in resistant phenotypes and DDS for fluconazole in percentages from 20% to 100% for C. albicans, from 50% to 100% C. glabrata, 33.3% to 100% C. parapsilosis and 100% C. tropicalis. For ketoconazole in the same isolates, there was a reduction in phenotypes with MIC > 16 μg/mL of up to 50% in C. albicans, 50% to 100% C. glabrata, 50% to 100% C. tropicalis. Conclusions: PDT with MB, GV and CR revealed efficacy in vitro in reducing the growth of C. albicans and non-albicans, especially due to chronic recurrent vulvovaginitis.

Wavelength-sensitive photocatalytic H2 evolution from H2S splitting over g-C3N4 with S,N-codoped carbon dots as the photosensitizer

Photocatalytic splitting of hydrogen sulfide(H2S) for hydrogen evolution is a promising method to solve the energy and environmental issues.In this work,S,N-codoped carbon dots(S,N-CDs)/graphitic carbon nitride(g-C3N4) nanosheet is synthesized by hydrothermal method as an efficient photocatalyst for the decomposition of H2S.In addition to the characterization of the morphology and structure,chemical state,optical and electrochemical performances of S,N-CDs/g-C3N4,hydrogen evolution tests show that the activity of g-C3N4 is improved by introducing S,N-CDs,and the enhancement depends strongly on the wavelength of incident light.The photocatalytic hydrogen production rate of S,N-CDs/g-C3N4 composite reaches 832 μmol g-1h-1, which is 38 times to that of g-C3N4 under irradiation at 460 nm.Density functional theory calculations and electron paramagnetic resonance as well as photoluminescence technologies have altogether authenticated that the unique wavelength-dependent photosensitization of S,N-CDs on g-C3N4;meanwhile,a good match between the energy level of S,N-CDs and g-C3N4 is pivotal for the effective photocatalytic activity.Our work has unveiled the detailed mechanism of the photocatalytic activity enhancement in S,N-CDs/g-C3N4 composite and showed its potential in photocatalytic splitting of H2S for hydrogen evolution.