Blue-Light-Activated Water-Soluble Sn(IV)-Porphyrins for Antibacterial Photodynamic Therapy (aPDT) against Drug-Resistant Bacterial Pathogens.

Antimicrobial resistance has emerged as a global threat to the treatment of infectious diseases. Antibacterial photodynamic therapy (aPDT) is a promising alternative approach and is highly suitable for the treatment of cutaneous bacterial infections through topical applications. aPDT relies on light-responsive compounds called photosensitizer (PS) dyes, which generate reactive oxygen species (ROS) when induced by light, thereby killing bacterial cells. Despite several previous studies in this area, the molecular details of targeting and cell death mediated by PS dyes are poorly understood. In this study, we further investigate the antibacterial properties of two water-soluble Sn(IV) tetrapyridylporphyrins that were quaternized with methyl and hexyl groups (1 and 2). In this follow-up study, we demonstrate that Sn(IV)-porphyrins can be photoexcited by blue light (a 427 nm LED) and exhibit various levels of bactericidal activity against both Gram-(+) and Gram-(-) strains of bacteria. Using localization studies through fluorescence microscopy, we show that 2 targets the bacterial membrane more effectively than 1 and exhibits comparatively higher aPDT activity. Using multiple fluorescence reporters, we demonstrate that photoactivation of 1 and 2 results in extensive collateral damage to the bacterial cells including DNA cleavage, membrane damage, and delocalization of central systems necessary for bacterial growth and division. In summary, this investigation provides deep insights into the mechanism of bacterial killing mediated by the Sn(IV)-porphyrins. Moreover, our approach offers a new method for evaluating the activity of PS, which may inspire the discovery of new PS with enhanced aPDT activity.

The photodynamic activity properties of a series of structurally analogous tetraarylporphyrin, chlorin and N-confused porphyrin dyes and their Sn(IV) complexes.

A series of tetraarylporphyrin, -chlorin and N-confused porphyrin dyes with 4­methoxy­meso-aryl rings (1-Por, 1-Chl and 1-NCP) and their Sn(IV) complexes (1-SnPor, 1-SnChl and 1-SnNCP) have been synthesized and characterized. The heavy atom effect of the Sn(IV) ion results in relatively high singlet oxygen quantum yield values of 0.67, 0.71 and 0.85 for 1-SnPor, 1-SnChl and 1-SnNCP, respectively. The photodynamic activities of 1-Por, 1-Chl, 1-NCP, 1-SnPor, 1-SnChl and 1-SnNCP were determined against MCF-7 breast cancer cells through illumination with Thorlabs 625 or 660 nm (240 or 280 mW.cm-2) light emitting diodes (LEDs) for 20 min. The IC50 values for 1-SnChl and 1-SnNCP lie between 1.4 - 6.1 and 1.6 - 4.8 µM upon photoirradiation with the 660 and 625 nm LEDs, respectively, while higher values of >10 µM were obtained for 1-SnPor and the free base dyes. In a similar manner, 1-SnChl and 1-SnNCP were found to also have significantly higher photodynamic antimicrobial activity against planktonic Gram-(+) Staphylococcus aureus and Gram-(-) Escherichia coli bacteria than the other dyes studied. Upon illumination with Thorlabs 625 and 660 nm LEDs for 75 min, Log10 reduction values of 7.62 and > 2.40-3.69 were obtained with 1 and 5 µM solutions, respectively.

The Photodynamic Anticancer and Antibacterial Activity Properties of a Series of meso-Tetraarylchlorin Dyes and Their Sn(IV) Complexes.

A series of tetraarylchlorins with 3-methoxy-, 4-hydroxy- and 3-methoxy-4-hydroxyphenyl meso-aryl rings (1-3-Chl) and their Sn(IV) complexes (1-3-SnChl) were synthesized and characterized so that their potential utility as photosensitizer dyes for use in photodynamic therapy (PDT) and photodynamic antimicrobial chemotherapy (PACT) can be assessed. The photophysicochemical properties of the dyes were assessed prior to in vitro PDT activity studies against MCF-7 breast cancer cells through irradiation with Thorlabs 625 or 660 nm LED for 20 min (240 or 280 mW·cm-2). PACT activity studies were performed against both planktonic bacteria and biofilms of Gram-(+) S. aureus and Gram-(-) E. coli upon irradiation with Thorlabs 625 and 660 nm LEDs for 75 min. The heavy atom effect of the Sn(IV) ion results in relatively high singlet oxygen quantum yield values of 0.69-0.71 for 1-3-SnChl. Relatively low IC50 values between 1.1-4.1 and 3.8-9.4 µM were obtained for the 1-3-SnChl series with the Thorlabs 660 and 625 nm LEDs, respectively, during the PDT activity studies. 1-3-SnChl were also found to exhibit significant PACT activity against planktonic S. aureus and E. coli with Log10 reduction values of 7.65 and >3.0, respectively. The results demonstrate that the Sn(IV) complexes of tetraarylchlorins merit further in depth study as photosensitizers in biomedical applications.

Sn(IV)-porphyrinoids for photodynamic anticancer and antimicrobial chemotherapy.

Photodynamic therapy (PDT) is a mode of treatment for different types of cancers, which involves a nontoxic photosensitizer (PS), a light source to activate the PS, and ground-state molecular oxygen (3O2). Light activation of the PS leads to the generation of reactive oxygen species (ROS), which initiates a toxic effect on the surrounding cellular substrates, thereby destroying the cancerous cells. The commercially used PDT drug Photofrin® which is a tetrapyrrolic porphyrin-based photosensitizer has drawbacks such as aggregation in water, prolonged skin photosensitivity, variability in chemical compositions, and minimal absorbance in the red-light region. Metallation of the porphyrin core with diamagnetic metal ions aids the photogeneration of singlet oxygen (ROS). Metalating with Sn(IV) provides a six-coordination octahedral geometry with trans-diaxial ligands. This approach suppresses aggregation in aqueous media and increases ROS generation upon light exposure due to the heavy atom effect. Bulky trans-diaxial ligation hinders the approach of the Sn(IV) porphyrins, thereby suppressing aggregation effects. In this review, we document the recently reported Sn(IV) porphyrinoids and their photodynamic therapy (PDT) and photodynamic antimicrobial chemotherapy (PACT) activity properties. In a similar manner to PDT, the photosensitizer is used to kill the bacteria upon irradiation with light during PACT. Often, bacteria develop resistance against conventional chemotherapeutic drugs over time, decreasing their antibacterial properties. However, in the case of PACT, it is difficult to generate resistance against singlet oxygen produced by the photosensitizer.

GaIIItriarylcorroles with push-pull substitutions: synthesis, electronic structure and biomedical applications.

Two A2B type H3corroles and two GaIIItriarylcorroles with carbazole substitutions at 10-positions were synthesized and characterized. An analysis of structure-property relationships of the corroles has been carried out by investigating the optical spectroscopy of the dyes to trends predicted in DFT and TD-DFT calculations. Interestingly, the photodynamic therapy (PDT) and photodynamic antimicrobial chemotherapy (PACT) activity properties of the GaIIItriarylcorroles were determined against the MCF-7 breast cancer line, and Staphyloccocus aureus (S. aureus) and Escherichia coli (E. coli), respectively. The cationic G-2Q species exhibited the most favorable properties with an IC50 value of 7.8 µM against MCF-7 cells, and Log reduction values of 7.78 and 3.26 against planktonic S. aureus and E. coli at 0.5 and 10 µM, respectively.

Photodynamic Antitumor and Antimicrobial Activities of Free-Base Tetra(4-methylthiolphenyl)chlorin and Its Tin(IV) Complex.

Meso-tetra(4-methylthiolphenyl)chlorin (3) and its Sn(IV) complex (3-Sn) have been synthesized and characterized. The heavy atom effects of the Sn(IV) ion and sulfur atoms result in relatively high singlet oxygen quantum yield values of 0.40 and 0.48. The photodynamic activities against MCF-7 breast cancer cells were determined through irradiation with a Thorlabs 660 nm LED for 30 min (280 mW.cm-2 ). IC50 values of 7.8 and 3.9 µM were obtained, respectively. 3-Sn was found to have significant photodynamic antimicrobial activity against both gram-(+) S. aureus and gram-(-) E. coli bacteria upon irradiation with a Thorlabs 660 nm LED for 75 min.

Novel cationic-chalcone phthalocyanines for photodynamic therapy eradication of S. aureus and E. coli bacterial biofilms and MCF-7 breast cancer.

New tetrasubstituted zinc (II) and indium (III) phthalocyanines bearing dimethylamino chalcone group (complexes 3 and 4) as well as their quaternized analogs (3a and 4a) have been assessed for their photodynamic therapy (PDT) of cancer as well as photodynamic antimicrobial chemotherapy activities against biofilms and planktonic cultures of pathogenic bacteria of Staphylococcus aureus and Escherichia coli. Compared to the non-quaternized phthalocyanines 3 and 4, the cationic phthalocyanines 3a and 4a exhibit a higher photodynamic inactivation against the planktonic cells with log reduction values above 9 at a concentration of 1.25 µM. This was attributed to the positive charge which enhances cellular uptake. More interestingly, 3a and 4a show a higher photodynamic inactivation (less than 3% of S. aureus survived) on their biofilm counterparts thanks to their stronger affinity to these cells. 3a and 4a Pcs also exhibited interesting PDT activity against MCF-7 cancer cells giving IC50 values of 17.9 and 7.4 µM, respectively following 15 min irradiation. The obtained results in this work show that the positively charged phthalocyanines 3a and 4a are potential antibacterial photosensitizers that show some selectivity toward the Gram-positive and Gram-negative bacteria as well as MCF-7 breasts cancer cells.

Positively charged styryl pyridine substituted Zn(II) phthalocyanines for photodynamic therapy and photoantimicrobial chemotherapy: effect of the number of charges.

Cationic Zn phthalocyanine complexes were synthesized using Knoevenagel reaction starting from a Zn(ii) tetrakis(2-formylphenoxy)phthalocyanine (1) to form Zn(ii) tetrakis(1-butyl-4-(4-(tetraphenoxy)styryl)pyridin-1-ium) phthalocyanine (2) and Zn(ii) tetrakis(4-(4-(tetraphenoxy)styryl)-1-(4-(triphenylphosphonio)butyl)pyridin-1-ium)phthalocyanine (3). The photophysicochemical behaviours of the Pc complexes were assessed. The cationic complexes display high water-solubility and gave moderate singlet oxygen quantum yield in water. The cationic Pcs demonstrate good cellular uptake and photodynamic activity against MCF-7 cells with IC50 values of 8.2 and 4.9 µM for 2 and 3, respectively. The cationic Pcs also demonstrate high photoantimicrobial activity against Escherichia coli with log reductions of 5.3 and 6.0 for 2 and 3, respectively.

Photodynamic activity and photoantimicrobial chemotherapy studies of ferrocene-substituted 2-thiobarbituric acid.

A ferrocene-substituted thiobarbituric acid (FT) has been synthesized to explore its photophysical properties and photodynamic and photoantimicrobial chemotherapy activities. FT has an intense metal-to-ligand charge transfer (MLCT) band at ca. 575 nm. The ferrocene moiety of FT undergoes photooxidation to form a ferrocenium species which in turn produces hydroxyl radical in an aqueous environment, which was confirmed via the bleaching reaction of p-nitrosodimethylaniline (RNO). FT exhibits efficient PDT activity against MCF-7 cancer cells with an IC50 value of 5.6 µM upon irradiation with 595 nm for 30 min with a Thorlabs M595L3 LED (240 mW cm-2). Photodynamic inactivation of Staphylococcus aureus and Escherichia coli by FT shows significant activity with log reduction values of 6.62 and 6.16 respectively, under illumination for 60 min at 595 nm. These results demonstrate that ferrocene-substituted thiobarbituric acids merit further study for developing novel bioorganometallic PDT agents.

Photodynamic activity of Sn(IV) tetrathien-2-ylchlorin against MCF-7 breast cancer cells.

A new readily-synthesized Sn(iv) tetraarylchlorin with thien-2-yl substituents (SnC) has been prepared and fully characterized by various spectroscopic techniques and its photophysical and photochemical properties, such as the singlet oxygen quantum yield (ΦΔ), fluorescence quantum yield (ΦF), triplet lifetime (τT) and photostability, have been evaluated. SnC has an unusually high ΦΔ value of 0.89 in DMF. Studies on the photodynamic activity against MCF-7 breast cancer cells exhibited a very low IC50 value of 0.9 µM and high phototoxicity (dark versus light) indices of >27.8 after irradiation with a 660 nm Thorlabs LED (280 mW cm-2). The results demonstrate that Sn(iv) tetraarylchlorins of this type are suitable candidates for further in-depth PDT studies.

Photocytotoxicity of heavy-atom-free thiobarbituric acid functionalized pyrene derivatives against MCF-7 cancer cells.

Two thiobarbituric acid-functionalized pyrene derivatives (P1, P2) have been synthesized to explore the photophysical properties and photodynamic activity of dyes of this type. Both compounds exhibit an intense intramolecular charge transfer (ICT) band at ca. 470 nm, which is absent in the spectra of the precursor. P1 and P2 exhibit singlet oxygen generation on irradiation with light with moderate singlet oxygen yields of 0.36 and 0.32, respectively, in DMSO. P1 showed better photodynamic activity against MCF-7 cells with an IC50 value of 18.3 µM under illumination at 455 nm for 60 min with a Thorlabs M455L3 LED (330 mW.cm-2).

Sn(IV) N-confused porphyrins as photosensitizer dyes for photodynamic therapy in the near IR region.

The utility of Sn(iv) N-confused porphyrin (SnNCP) for use as photosensitizer dyes in photodynamic therapy is investigated. SnNCP has an unusually high singlet oxygen quantum yield of 0.72 in DMSO. IC50 values of 1.6 and 12.8 µM were obtained against MCF-7 cells upon irradiation with 660 and 780 nm LEDs.

An octabrominated Sn(iv) tetraisopropylporphyrin as a photosensitizer dye for singlet oxygen biomedical applications.

Two novel Sn(iv) tetraisopropylphenylporphyrins have been synthesized to explore the effect of octabromination at the ß-pyrrole positions on their photophysical properties and photodynamic activity. The lower energy Q band of an octabrominated complex lies at 675 nm well within the therapeutic window. The octabrominated dye has a relatively high singlet oxygen quantum yield of 0.78 in DMF and exhibits favorable photodynamic activity against MCF-7 cells with an IC50 value of 10.7 µM and a 5.74 log reduction value (5 µM) towards S. aureus under illumination at 660 nm for 60 min with a Thorlabs M660L3 LED (280 mW cm-2).

Preparation of NIR absorbing axial substituted tin(iv) porphyrins and their photocytotoxic properties.

Sn(iv) porphyrins ([Sn(iv)TTP(3PyO)2] (5) and [Sn(iv)TPP(3PyO)2] (6) [tetrathienylporphyrin (TTP), tetraphenylporphyrin (TPP), and pyridyloxy (PyO)]) were prepared and characterized and their photocytotoxicity upon irradiation with 625 nm light has been studied. The presence of the 3PyO axial ligands was found to limit the aggregation and enhance the solubility of 5 and 6 in DMF/H2O (1 : 1). The photophysical properties and photodynamic therapy (PDT) activity of the meso-2-thienyl and meso-phenyl-substituted Sn(iv) porphyrins are compared. 5 and 6 were found to be photocytotoxic in MCF-7 cancer cells when irradiated with a Thorlabs M625L3 LED at 625 nm but remained nontoxic in the dark. The PDT activity of Sn(iv) meso-tetra-2-thienylporphyrin 5 was found to be significantly enhanced relative to its analogous tetraphenylporphyrin 6. There is a marked red-shift of the Q00 band of 5 into the therapeutic window due to the meso-2-thienyl rings, and 5 has an unusually high singlet oxygen quantum yield value of 0.83 in DMF. The results demonstrate that readily synthesized axially ligated Sn(iv) meso-arylporphyrins are potentially suitable for use as singlet oxygen photosensitizers in biomedical applications and merit further in depth investigation in this context.

Efficacy of bilateral pectoralis nerve block for ultrafast tracking and postoperative pain management in cardiac surgery.

BACKGROUND: Good postoperative analgesia in cardiac surgical patients helps in early recovery and ambulation. An alternative to parenteral, paravertebral, and thoracic epidural analgesia can be pectoralis nerve (Pecs) block, which is novel, less invasive regional analgesic technique. AIMS: We hypothesized that Pecs block would provide superior postoperative analgesia for patients undergoing cardiac surgery through midline sternotomy compared to parenteral analgesia. MATERIALS AND METHODS: Forty adult patients between the age groups of 25 and 65 years undergoing coronary artery bypass grafting or valve surgeries through midline sternotomy under general anesthesia were enrolled in the study. Patients were randomly allocated into two groups with 20 in each group. Group 1 patients did not receive Pecs block, whereas Group 2 patients received bilateral Pecs block postoperatively. Patients were extubated once they fulfilled extubation criteria. Ventilator duration was recorded. Patients were interrogated for pain by visual analog scale (VAS) scoring at rest and cough. Inspiratory flow rate was assessed using incentive spirometry. RESULTS: Pecs group patients required lesser duration of ventilator support (P < 0.0001) in comparison to control group. Pain scores at rest and cough were significantly low in Pecs group at 0, 3, 6, 12, and 18 h from extubation (P < 0.05). At 24 h, VAS scores were comparable between two groups. Peak inspiratory flow rates were higher in Pecs group as compared to control group at 0, 3, 6, 12, 18, and 24 h (P < 0.05). Thirty-four episodes of rescue analgesia were given in control group, whereas in Pecs group, there were only four episodes of rescue analgesia. CONCLUSION: Pecs block is technically simple and effective technique and can be used as part of multimodal analgesia in postoperative cardiac surgical patients for better patient comfort and outcome.

AzaHx, a novel fluorescent, DNA minor groove and G·C recognition element: Synthesis and DNA binding properties of a p-anisyl-4-aza-benzimidazole-pyrrole-imidazole (azaHx-PI) polyamide.

The design, synthesis, and DNA binding properties of azaHx-PI or p-anisyl-4-aza-benzimidazole-pyrrole-imidazole (5) are described. AzaHx, 2-(p-anisyl)-4-aza-benzimidazole-5-carboxamide, is a novel, fluorescent DNA recognition element, derived from Hoechst 33258 to recognize G·C base pairs. Supported by theoretical data, the results from DNase I footprinting, CD, ΔT(M), and SPR studies provided evidence that an azaHx/IP pairing, formed from antiparallel stacking of two azaHx-PI molecules in a side-by-side manner in the minor groove, selectively recognized a C-G doublet. AzaHx-PI was found to target 5'-ACGCGT-3', the Mlu1 Cell Cycle Box (MCB) promoter sequence with specificity and significant affinity (K(eq) 4.0±0.2×10(7) M(-1)).

A comparative study of pharmacological myocardial protection between sevoflurane and desflurane at anaesthestic doses in patients undergoing off pump coronary artery bypass grafting surgery.

BACKGROUND AND AIMS: Perioperative myocardial ischaemia (PMI) is one of the known complications during off pump coronary artery bypass (OPCAB) surgeries. The length of hospital stay is considerably prolonged in patients with PMI. Myocardial protection is an area which is being widely researched currently to prevent or reduce the incidence of PMI. Over the last decade it has become clear that volatile anaesthetic agents are protective in the setting of PMI and reperfusion. Hence, we planned to study the effect of two different volatile anaesthetics as myocardial protective agents in OPCAB surgery. METHODS: A total of 40 patients were enrolled for the study; Group A (sevoflurane, n = 20) and Group B (desflurane, n = 20). All patients had a baseline measurement of Trop-T, creatine phosphokinase-MB (CPKMB) and myocardial performance index (MPI) pre-operatively, which was repeated 4 h after the surgery. Chi-square/Fisher test was used to find the significance of the differences between the two agents. RESULTS: Patients were comparable in demographic, baseline, biochemical and echo criteria. Post-operative CPKMB levels (desflurane - 30.85 ± 2.69 u/L; sevoflurane - 29.05 ± 5.26 u/L, P = 0.7) and number of Trop-T positive patients (Sevoflurane - 9; desflurane - 6, P ≥ 0.05) were comparable. Post-operative MPI indicated decreased left ventricular function in sevoflurane group as compared to desflurane group (P ≤ 0.03). CONCLUSION: Desflurane exerts better cardioprotective effect than sevoflurane as indicated by better MPI in OPCAB surgeries.

Conformational modulation of DNA by polyamide binding: structural effects of f-Im-Py-Im based derivatives on 5'-ACGCGT-3'.

The DNA sequence 5'-ACGCGT-3' is in the core site of the Mlu 1 cell-cycle box, a transcriptional element in the promoter region of human Dbf4 gene that is highly correlated with a large number of aggressive solid cancers. The polyamide formamido-imidazole-pyrrole-imidazole-amine(+) (f-Im-Py-Im-Am(+) ) can target the minor groove of 5'-ACGCGT-3' as an antiparallel stacked dimer and has shown good activity in inhibiting transcription factor binding. Recently, f-Im-Py-Im-Am(+) derivatives that involve different orthogonally positioned substituents were synthesized to target the same binding site, and some of them have displayed improved binding and pharmacological properties. In this study, the gel electrophoresis-ligation ladders assay was used to evaluate the conformational effects of f-Im-Py-Im-Am(+) and derivatives on the target DNA, an essential factor for establishing the molecular basis of polyamide-DNA complexes and their transcription factor inhibition. The results show that the ACGCGT site in DNA has a relatively wide minor groove and a B-form like overall structure. After binding with f-Im-Py-Im-Am(+) derivatives, the DNA conformation is changed as indicated by the different mobilities in the gel. These conformational effects on DNA will at least help to point to the mechanism for the observed Mlu 1 inhibition activity of these polyamides. Therefore, modulating DNA transcription by locking the DNA shape or altering the minor groove geometry to affect the binding affinity of certain transcription factors is an attractive possible therapeutic mechanism for polyamides. Some of the substituents are charged with electrostatic interactions with DNA phosphate groups, and their charge effects on DNA gel mobility have been observed.

Affinity and kinetic modulation of polyamide-DNA interactions by N-modification of the heterocycles.

Synthetic N-methyl imidazole and N-pyrrole containing polyamides (PAs) that can form "stacked" dimers can be programmed to target and bind to specific DNA sequences and control gene expression. To accomplish this goal, the development of PAs with lower molecular mass which allows for the molecules to rapidly penetrate cells and localize in the nucleus, along with increased water solubility, while maintaining DNA binding sequence specificity and high binding affinity is key. To meet these challenges, six novel f-ImPy*Im PA derivatives that contain different orthogonally positioned moieties were designed to target 5'-ACGCGT-3'. The synthesis and biophysical characterization of six f-ImPy*Im were determined by CD, ΔTM, DNase I footprinting, SPR, and ITC studies, and were compared with those of their parent compound, f-ImPyIm. The results gave evidence for the minor groove binding and selectivity of PAs 1 and 6 for the cognate sequence 5'-ACGCGT-3', and with strong affinity, Keq = 2.8 × 10(8) M(-1) and Keq = 6.2 × 10(7) M(-1), respectively. The six novel PAs presented in this study demonstrated increased water solubility, while maintaining low molecular mass, sequence specificity, and binding affinity, addressing key issues in therapeutic development.