High Singlet Oxygen Quantum Yield Research Articles

The new metal-free, zinc, magnesium, indium ball-type phthalocyanines and their hybrids with graphene oxide: Synthesis, investigation of photophysical, photochemical properties and theoretical studies

In this study, four ball-type phthalocyanines (BTPc-H2-4, BTPc-Zn-5, BTPc-Mg-6, BTPc-In-7) were synthesized from 3,3,′((3,5-di-tert-butyl-1,2-phenylene)bis(oxy)diphthalonitrile in a single reaction step. Non-covalent ball-type phthalocyanine (BTPc)-graphene oxide (GO) hybrids (BTPc-GO) were prepared by simple sonication method. The structures were confirmed by elemental analysis, ultraviolet–visible (UV–Vis), fourier-transform infrared (FT-IR), proton nuclear magnetic resonance (1H NMR), MALDI-TOF MS spectroscopies, elemental analysis and scanning electron microscope (SEM). The photophysical and photochemical properties of ball-type phthalocyanines were investigated in dimethyl sulfoxide (DMSO) and tetrahydrofuran (THF). In this way, the contribution of solution polarity to these properties was compared. The contribution of GO was examined by examining the singlet oxygen quantum yields of BTPc-GO hybrids in DMSO. In addition, the structural properties of ball-type phthalocyanines were examined through theoretical studies and the effect of structural properties on experimentally determined band gaps was examined. Interestingly, we also report that ball-type thalocyanines are both photostable and exhibit extremely high singlet oxygen quantum yields. In addition, we can state that hybrids of these compounds with GO also show the ability to increase the singlet oxygen quantum yield, depending on the degree of interaction.

1,4-Benzodioxane Substituted Aza-BODIPY: Towards Photostable yet Efficient Triplet Photosensitizer.

We report herein the synthesis of aza-BODIPY substituted with 1,4-benzodioxane-6-yl substituents at 3,5 positions of the chromophore system. Both pyrrole rings of the aza-BODIPY in question were substituted with bromine atoms in order to induce highly desirable photophysical properties, such as highly populated excited triplet state (T1) and long excited triplet-state lifetime (τT) of 21 μs. The photosensitized oxygenation of a model compounds, viz. DPBF, points to a high singlet oxygen and/or other ROS formation quantum yield of 0.42. The photosensitizer studied exhibited an absorption band within the so-called "therapeutic window", with λabs 678 nm. As estimated by CV/DPV measurements the 1,4-benzodioxane-6-yl substituted aza-BODIPYs studied exhibited a multi-electron oxidations at a relatively low potentials (Eox), pointing to the very good electron-donating properties of these molecules. High photostability and thermal stability was observed for all compounds studied. The good singlet oxygen quantum yield measured combined with an exceptional photostability makes this aza-BODIPY a promising candidate for applications such as photocatalysis and photodynamic therapy (PDT).

Hydrazone-Functionalized trans-A2B-Corroles: Effective Synergy in Photodynamic Therapy of Lung Cancer.

A synthetic route to trans-A2B-corroles combining the macrocyclic core with a hydrazone moiety, based on the reactivity of azoalkenes toward dipyrromethanes, has been established with the aim of developing a new class of photosensitizers for photodynamic therapy of lung cancer. The study of the photophysical properties of the novel macrocycles allowed the identification of photosensitizers with absorption within the phototherapeutic window and high singlet oxygen quantum yield. Relevant structure-photodynamic activity correlations were established by studying the new corroles-based photodynamic therapy (PDT) in human lung cancer cell lines (A549 and H1299). The methyl-hydrazone corroles were more active than phenyl-hydrazone corroles, with the N-Boc and N-Ts groups being key structural features to ensure high activity. The lead photosensitizers, with IC50 values below 100 nM and no cytotoxicity per se, were significantly more active than 5,10,15-triphenylcorrole, showing that the presence of the hydrazone functional group has a strong influence on PDT activity.

Silicon Phthalocyanines Functionalized with Axial Substituents Targeting PSMA: Synthesis and Preliminary Assessment of Their Potential for PhotoDynamic Therapy of Prostate Cancer.

Photodynamic therapy (PDT) is a clinical modality based on the irradiation of different diseases, mostly tumours, with light following the selective uptake of a photosensitiser by the pathological tissue. In this study, two new silicon(IV)phtalocyanines (SiPcs) functionalized at both axial positions with a PSMA inhibitor are reported as candidate photosensitizers for PDT of prostate cancer, namely compounds SiPc-PQ(PSMAi)2 and SiPc-OSi(PSMAi)2. These compounds share the same PSMA-binding motif, but differ in the linker that connects the inhibitor moiety to the Si(IV) atom: an alkoxy (Si-O-C) bond for SiPc-PQ(PSMAi)2, and a silyloxy (Si-O-Si) bond for SiPc-OSi(PSMAi)2. Both compounds were synthesized by a facile synthetic route and fully characterized by 2D NMR, mass spectrometry and absorption/fluorescence spectrophotometry. The PDT agents showed a suitable solubility in water, where they essentially exist in monomeric form. SiPc-PQ(PSMAi)2 showed a higher singlet oxygen quantum yield ΦΔ, higher fluorescence quantum yields ΦF and better photostability than SiPc-OSi(PSMAi)2. Both compounds were efficiently taken up by PSMA(+) PC3-PIP cells, but not by PSMA(-) PC3-FLU cells. However, SiPc-PQ(PSMAi)2 showed a more specific photoinduced cytotoxicity in vitro, which is likely attributable to a better stability of its water solutions.

High Photocytotoxicity Iridium(III) Complex Photosensitizer for Photodynamic Therapy Induces Antitumor Effect Through GPX4-Dependent Ferroptosis.

The development of small molecule photosensitizers based on iridium complex is limited by the mismatch between therapeutic effect and systemic toxicity, as well as the incomplete understanding of the molecular mechanism underlying cell death induction. Herein, a small molecule iridium complex IrC with high photocytotoxicity is synthesized, with half maximal inhibitory concentration as low as 91 nm, demonstrating excellent anti-tumor, relief of splenomegaly, and negligible side effects. Starting from the factors of effective photosensitizers, the in-depth theoretical analysis on photon absorption efficiency, energy transfer level matching, and properties of the triplet excited state of IrC is conducted. This also elucidates the feasibility of generating the high singlet oxygen quantum yield. In addition, the death mechanism induced by IrC is focused, innovatively utilizing GPX4-overexpression and GPX4-knockout cells via CRISPR/Cas9 technique to comprehensively verify ferroptosis and its further molecular mechanism. The generation of ROS mediated by IrC, along with the direct inhibition of GPX4 and glutathione, synergistically increased cellular oxidative stress and the level of lipid peroxidation. This study provides an effective approach for small molecule complexes to induce GPX4-dependent ferroptosis at low-dose photodynamic therapy.

Accelerating the discovery of type Ⅱ photosensitizer: Experimentally validated machine learning models for predicting the singlet oxygen quantum yield of photosensitive molecule

Photodynamic therapy (PDT) is an emerging cancer treatment that mainly relies on photosensitizer (PS) to generate singlet oxygen for tumor destruction. Developing PSs with high singlet oxygen quantum yields (SO-QYs) requires extensive experimentation, limiting their rapid screening. Herein, to streamline this process, this study introduces several machine learning (ML) models that accurately predicts SO-QY across various experimental conditions. The models’ establishment is based on two feature matrices derived from Morgan fingerprints (MFPs) and descriptors (molecular descriptors and quantum chemical descriptors, MD_QCDs). Comparative and evaluative results indicate that the XGBoost model constructed with MFPs and the AdaBoost model constructed with MD_QCDs exhibit superior predictive performance, with R2 values of 0.8648 and 0.8460, respectively. Furthermore, by utilizing SHapley Additive exPlanations (SHAP) analysis and quantum chemistry, we analyzed that the iodine atoms and larger conjugated systems significantly influenced the SO-QY. Experimental validation, based on this analysis, demonstrates that our models not only possess excellent predictive capabilities but also exhibit strong interpretability. In summary, this work has established several interpretable models with outstanding predictive performance, which can aid in the more rapid screening of PSs, thus promoting their application in PDT.

Phenanthrene Appending Ruthenium Complexes: DNA Binding, Molecular Docking, TDDFT Calculation, and Photocytoxicity In Vitro

ABSTRACTPhotodynamic therapy (PDT) has been an effective tumor treatment to reduce the side effects of chemotherapy. Herein, we described the synthesis of two Ru (II) complexes by introducing a phenanthrene unit and their photocytotoxicity. Ru1 and Ru2 displayed high DNA affinities by intercalation. Under light, two complexes produced high singlet oxygen (1O2) quantum yields and cleaved DNA efficiently. Both high DNA affinities and 1O2 quantum yields of two complexes resulted in obvious photocytotoxicity towards Hela, A549, and A375 cells. Furthermore, low dark cytotoxicity was also observed for two complexes, which may promote them to act as potential PDT agents. TDDFT (Time‐dependent density functional theory) calculations also demonstrated two complexes that might display the PDT activities via 1O2 photogeneration.

Pyridinethiolate-Capped CdSe Quantum Dots for Red-Light-Driven H2 Production in Water.

The utilization of low-energy sunlight to produce renewable fuels is a subject of great interest. Here we report the first example of metal chalcogenide quantum dots (QDs) capped with a pyridinethiolate carboxylic acid (pyS-COOH) for red-light-driven H2 production in water. The precious-metal-free system is robust over 240 h, and achieves a turnover number (TON) of 43910±305 (vs Ni) with a rate of 31570±1690 μmol g-1 h-1 for hydrogen production. In contrast to the inactive QDs capped with other thiolate ligands, the CdSe-pyS-COOH QDs give a significantly higher singlet oxygen quantum yield [ΦΔ (1O2)] in solution.

Advancements of Porphyrin-Derived Nanomaterials for Antibacterial Photodynamic Therapy and Biofilm Eradication.

The threat posed by antibiotic-resistant bacteria and the challenge of biofilm formation has highlighted the inadequacies of conventional antibacterial therapies, leading to increased interest in antibacterial photodynamic therapy (aPDT) in recent years. This approach offers advantages such as minimal invasiveness, low systemic toxicity, and notable effectiveness against drug-resistant bacterial strains. Porphyrins and their derivatives, known for their high molar extinction coefficients and singlet oxygen quantum yields, have emerged as crucial photosensitizers in aPDT. However, their practical application is hindered by challenges such as poor water solubility and aggregation-induced quenching. To address these limitations, extensive research has focused on the development of porphyrin-based nanomaterials for aPDT, enhancing the efficacy of photodynamic sterilization and broadening the range of antimicrobial activity. This review provides an overview of various porphyrin-based nanomaterials utilized in aPDT and biofilm eradication in recent years, including porphyrin-loaded inorganic nanoparticles, porphyrin-based polymer assemblies, supramolecular assemblies, metal-organic frameworks (MOFs), and covalent organic frameworks (COFs). Additionally, insights into the prospects of aPDT is offered, highlighting its potential for practical implementation.

Lu, Sm, and Y-based double-decker phthalocyanines with enhanced photodynamic therapy performance

This paper focuses on the preparation of 3,5-di-tert-butylphenoxy substituted Lu, Sm, and Y-based double-decker phthalocyanines (Pcs), and investigation of their PDT properties. Briefly, 1,8,15,22-tetra-(3,5-di-tert-butylphenoxy) bisphthalocyanine derivatives (denoted LuPc2-3, SmPc2-4, YPc2-5) were synthesized by a two-step process. First, metal-free 1,8,15,22-tetra-(3,5-di-tert-butylphenoxy)phthalocyanine was prepared by tetramerization of 3,5-di-tert-butylphenoxy phthalonitrile, which is followed by reaction of different lanthanide salts with 1,8,15,22-tetra-(3,5-di-tert-butylphenoxy)bisphthalocyanine. The resultant double-decker Pcs were characterized in detail by UV–Vis, FT-IR, 1H NMR, fluorescence spectroscopy, MALDI-TOF MS, and elemental analysis. Strikingly, we report that double-decker phthalocyanines are not only photostable, but also exhibit relatively high singlet oxygen quantum yields of 0.96 (LuPc2-3), 0.91 (SmPc2-4) 0.87 (YPc2-5) and in THF.

Boosting the in-vitro effectiveness of photodynamic therapy on MCF-7 breast cancer cells with encapsulated malachite green by silica nanoparticles

Photodynamic therapy (PDT) is a promising cancer treatment strategy utilizing photosensitizers (PS) and light to generate singlet oxygen, with Malachite Green (MG) showing high singlet oxygen quantum yield. Effective delivery of MG to the target tissue remains a key challenge. Encapsulation techniques have been investigated to improve PS delivery, minimize PS leakage, inhibit diaphorase-induced reduction, and mitigate PS-related toxicity. Silica nanoparticles (SiNPs) offer favorable characteristics for drug delivery in PDT and serve as promising delivery carriers. In this study, SiNPs were synthesized and employed as carriers for MG. The size and shape of nanoparticles were determined using Transmission Electron Microscopy (TEM). A range of concentrations of MG were applied to MCF-7 breast cancer cells in order to evaluate the cytotoxicity of both naked and encapsulated MG. This helped identify the most effective concentrations and exposure durations required to induce damage under red laser light (Intensity ∼110 mW/cm2). The results indicated that SiNPs-encapsulated MG exhibited superior efficacy compared to naked MG, with a concentration efficacy increase of +50 % and an exposure time efficacy increase of +45 %. This underlines the enhanced capability of encapsulated MG to eliminate MCF-7 cells when compared to naked MG. The application of synthesized SiNPs for MG delivery improved the effectiveness of photodynamic therapy by augmenting MG bioavailability in target cells.

Asymmetric heptamethine cyanine dye for viscosity detection and photodynamic therapy

In this work, we disclose the new optical property of Cy7-TCF, an asymmetric heptamethine cyanine in which the indole donor is coupled to the 2-dicyanomethylene-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran (TCF) acceptor, as an effective PDT rendering it responsive to near-infrared (NIR) light at 850 nm. Upon activation, Cy7-TCF exhibits a remarkably high singlet oxygen quantum yield (ΦΔ = 1.84 in a 50 % glycerol/PBS system), producing both fluorescence and singlet oxygen for effective PDT. Additionally, Cy7-TCF displays cancer cell specificity, leveraging viscosity changes, while showing negligible dark cytotoxicity. Flow cytometry analysis confirms PDT-induced cell apoptosis. Under NIR light activation, Cy7-TCF emerges as a promising dual-functional agent, serving as a theranostic tool for NIR imaging-guided PDT.

Antibacterial Properties of Rose Bengal Conjugated to Hyaluronic Acid.

Dental diseases, including conditions affecting oral structures, have become more common due to unhealthy lifestyle choices. Traditional antibiotic treatments face challenges related to the development of antibiotic resistance in bacteria. Photodynamic antibacterial chemotherapy is emerging as a promising alternative using photosensitizers to generate reactive oxygen species upon exposure to light. This article examines the photosensitizer Rose Bengal (RB) immobilized in hyaluronic acid (HA) for prolonged antibacterial action. The RB-HA conjugate demonstrated a molar ratio of approximately three RB residues to each of the ten units of HA. RB-HA exhibited a high singlet oxygen quantum yield (ΔΦ = 0.90), suggesting its efficacy in photodynamic treatment. A photostability analysis revealed slower photobleaching of RB-HA, which is essential for prolonged application. Under visible light and ultrasonic treatment, RB-HA exhibited effective antibacterial activity against Gram-positive S. aureus and Gram-negative E. coli bacteria for at least 80 days. The gradual release of RB ensured sustained bactericidal concentration. The study establishes RB-HA as a promising candidate for antimicrobial photodynamic and sonodynamic therapy in dental and other medical fields, providing enhanced stability and prolonged antibacterial efficacy.

Cationized orthogonal triad as a photosensitizer with enhanced synergistic antimicrobial activity

Single-molecule-based synergistic phototherapy holds great potential for antimicrobial treatment. Herein, we report an orthogonal molecular cationization strategy to improve the reactive oxygen species (ROS) and hyperthermia generation of heptamethine cyanine (Cy7) for photodynamic and photothermal treatments of bacterial infections. Cationic pyridine (Py) is introduced at the meso‑position of the asymmetric Cy7 with intramolecular charge transfer (ICT) to construct an atypical electron-transfer triad, which reduces ΔES1-S0, circumvents rapid charge recombination, and simultaneously enhances intersystem crossing (ISC) based on spin-orbit charge-transfer ISC (SOCT-ISC) mechanism. This unique molecular construction produces anti-Stokes luminescence (ASL) because the rotatable CN bond enriched in high vibrational-rotational energy levels improves hot-band absorption (HBA) efficiency. The obtained triad exhibits higher singlet oxygen quantum yield and photothermal conversion efficiency compared to indocyanine green (ICG) under irradiation above 800 nm. Cationization with Py enables the triad to target bacteria via intense electrostatic attractions, as well as biocidal property against a broad spectrum of bacteria in the dark. Moreover, the triad under irradiation can enhance biofilm eradication performance in vitro and statistically improve healing efficacy of MRSA-infected wound in mice. Thus, this work provides a simple but effective strategy to design small-molecule photosensitizers for synergistic phototherapy of bacterial infections. Statement of SignificanceWe developed an orthogonal molecular cationization strategy to enhance the reactive oxygen species and thermal effects of heptamethine cyanine (Cy7) for photodynamic and photothermal treatments of bacterial infections. Specifically, cationic pyridine (Py) was introduced at the meso‑position of the asymmetric Cy7 to construct an atypical electron-transfer triad, which reduced ΔES1-S0, circumvented rapid charge recombination, and simultaneously enhanced intersystem crossing (ISC). This triad, with a rotatable CN bond, produced anti-Stokes luminescence due to hot-band absorption. The triad enhanced antimicrobial performance and statistically improved the healing efficacy of MRSA-infected wounds in mice. This site-specific cationization strategy may provide insights into the design of small molecule-based photosensitizers for synergistic phototherapy of bacterial infections.

Supramolecular engineering cascade regulates NIR-II J-aggregates to improve photodynamic therapy.

Rational design of small organic molecule-based NIR-II photosensitizers (PSs) with high singlet oxygen quantum yield in aqueous solution for deep tissue imaging and cancer therapy still presents challenges. Herein, we devised a general synthesis strategy to obtain six NIR-II region PSs with tunable aggregation states by adjusting the steric effect, and all PSs possess longer NIR absorption/emission wavelengths with tails extending beyond 1200 nm. Notably, ATX-6 possessed a singlet oxygen quantum yield of 38.2% and exhibited concentration-dependent J-aggregation properties upon self-assembly in an aqueous solution. What's more, supramolecular engineering with DSPE-PEG2000 further enhanced its degree of J-aggregation, which was attributed to the dimer-excited reduction of the energy levels of the single-linear/triple-linear states and the facilitation of intersystem crossover processes. In addition, ATX-6 NPs showed superior photodynamic therapy effects and great potential in high-contrast in vivo bioimaging of the NIR-II region. These results provide valuable insights for achieving the diagnostic and therapeutic integration of tumors.

Exploring improved strategies for therapeutic studies and biological activities of novel zinc and indium phthalocyanines.

This study investigates novel zinc and indium phthalocyanines with Schiff base and sulphur moieties, focusing on their potential for cancer therapy and antimicrobial applications. It explores the effectiveness of photochemical and sono-photochemical methods to enhance singlet oxygen production, which is crucial for photodynamic therapy. The synthesized complexes in this study demonstrated high singlet oxygen quantum yields, with D3 (ZnPc) and D4 (InPc) showing ΦΔPDT values of 0.71 and 0.75, and ΦΔSPDT values of 0.91 and 0.94, respectively. Furthermore, the evaluation for biological properties revealed that both D3 and D4 exhibit significant antidiabetic properties, DPPH radical scavenging activity, DNA cleavage, antimicrobial activity, biofilm inhibition, and microbial cell viability impacts, both with and without photodynamic therapy. Notably, D3 and D4 achieved antimicrobial cell viability inhibition rates of 84.67 ± 4.67% and 98.32 ± 5.96%, respectively, showcasing their effectiveness in photodynamic antimicrobial therapy. Overall, the study highlights the potential of these phthalocyanine complexes as advanced photosensitizers, with strong singlet oxygen generation and promising biological activities, paving the way for future therapeutic applications.

Theoretical study on the photophysical properties of thiophene-fused-type BODIPY series molecules in fluorescence imaging and photodynamic therapy.

As a class of photosensitizers (PSs) with dual functions of photodynamic therapy (PDT) and fluorescence imaging, the relationship between the structure and dual-function of thiophene-fused-type BODIPY dyes has not been studied in depth before. We found that the thiophene-fused-type BODIPY triplet photosensitizer is produced according to the energy level matching rule and the introduction of the thiophene ring significantly reduces the energy gap ΔEST between singlet and triplet states, as revealed by our investigation of the excited state structures and energies of thieno-fused BODIPY dyes. At the same time, a tiny ΔEST also results in a greatly enhanced intersystem crossing (ISC) rate, kISC. The kISC value of MeO-BODIPY, having the highest singlet oxygen quantum yield (ΦΔ), is the largest. Substitution with a strong electron donor N,N-dimethylaminophenyl (DMA) leads to the vertical configuration in the T1 state. The small ΔE (0.0029 eV) between the HOMO and HOMO-1 triggers the photo induced electron transfer (PET) of inhibiting ISC and fluorescence. When thieno-fused BODIPYs react with pyrrole, the increase of π-conjugation and smaller ΔEHOMO-LUMO explain the redshift in emission wavelength of thieno-pyrrole-fused BODIPY. The more planar configuration of the S1 state and the stronger oscillator intensity reflect a higher fluorescence quantum yield (ΦF). The extension of π-conjugation can cause molecules to transition to higher-level singlet excited states (Sn states, n ≥ 1) after absorbing energy and reduce the energy level of the excited state, resulting in multiple channels and favoring 1O2 production for thieno-pyrrole-fused BODIPYs with electron-withdrawing groups at the para-position of the phenyl groups. Due to ΔES0-T1 < 0.980 eV, the substitution of electron-donating groups cannot produce 1O2. In this work, we have revealed the mechanism of ISC and the fluorescence emission process in the thiophene-fused-type BODIPY dye, which has provided a theoretical foundation and guidance for the future design of BODIPY-based heavy-atom-free PSs for molecular applications in PDT.

Synthesis of phenanthroline substituted five-nuclear phthalocyanine zinc complex and exploring of photochemical and sono-photochemical properties

Sono-photodynamic therapy (SPDT) which is the combination of photodynamic therapy (PDT) and sonodynamic therapy (SDT) is an alternative and efficient method among cancer treatments achieving high singlet oxygen quantum yield. This study aimed to synthesize Schiff base substituted Zn phthalocyanine containing phenanthroline group to obtain suitable sono-photosensitizer. The target phthalocyanine (4) was obtained by cyclotetramerization reaction of phenanthroline-Zn(II) complex substituted phthalonitrile (3) with zinc acetate. The synthesized compounds were characterized by various spectroscopic techniques including FT-IR, Mass, UV–Vis, and 1H NMR spectroscopy. The singlet oxygen quantum yield was calculated in both photochemical and sono-photochemical method for compound 4. While the ΦΔ value was calculated as 0.72 for photochemical method, the ΦΔ value reached to 0.98 for sono-photochemical method.

Versatile phototheranostic system: Aza-BODIPY-based nanoparticles with B,O-chelated core and diiodine

The heavy atom effect is widely recognized for its ability to enhance the photodynamic effect, but it also gives rise to concerns about fluorescence quenching and low photothermal conversion efficiency. In this study, we introduced iodine atoms into B,O-chelated aza-BODIPY and coated them with DSPE-PEG2000 to achieve high singlet oxygen quantum yields (64.9 %), while simultaneously maintaining excellent fluorescence emission (Φ = 0.94 %) and photothermal conversion capability (PCE = 33.8 %). The B,O-chelated aza-BODIPY derivative shows a remarkable synergistic and improved phototherapy therapeutic performance mainly by the innovative enhancement of the π-conjugated structure from the B,O-chelated structure and partial weakening of intermolecular π-π stacking from the steric hindrance of iodine atoms, which was validated through in vivo and in vitro tumor diagnosis and elimination experiments, utilizing state-of-the-art fluorescence imaging, photoacoustic imaging, and photothermal imaging for multimodal imaging-guided photodynamic therapy and photothermal therapy. This groundbreaking approach effectively overcomes the limitations of the traditional heavy atom effect, and presents a pioneering perspective on constructing a versatile phototheranostic system for precise and efficient tumor treatment. By effectively addressing the challenges posed by the heavy atom effect and maximizing the capabilities of the photosensitizer, we pave the way for more accurate and effective approaches in combating tumors.

Photodynamic antimicrobial chemotherapy activities of phthalocyanine-antibiotic conjugates against bacterial biofilms and interactions with extracellular polymeric substances

This study sheds light on how to rationally design efficient photodynamic antimicrobial chemotherapy (PACT) agents by covalently linking phthalocyanines (Pcs) as photosensitizers with an antibiotic: Ciprofloxacin (CIP). Pcs used are zinc (II) 3-(4-((3,17,23-tris(4-(Benzo(d)thiazol-2-yl] thiol) phthalocyanine-9-yl) oxy) phenyl) propanoic acid (1) and zinc (II) 3-(4-(3,17,23-tris(3-(4-(triphenylphosphine) butyl) benzo[d]thiazol-3-ium bromide phthalocyanine-9-yl) oxy) phenyl) propanoic acid (2). High singlet oxygen quantum yields are observed in the presence of CIP. Square wave voltammetry was used to analyse the Pc-CIP uptake by bacteria biofilms of Streptococcus pneumoniae (S. pneumonia) and Escherichia coli (E. coli). Electrochemical impedance spectroscopy and scanning electron spectroscopy were used to study the stability of the biofilms in the presence Pc-CIP complexes and when exposed to light. Raman and time of flight-secondary ion mass spectrometry (TOF-SIMS) are used to identify the breakdown of cellular components of the biofilm and penetration of the Pc-CIP into the biofilms, respectively.