Applications of Fluorous Porphyrinoids: An Update.

Porphyrins and related macrocycles have been studied broadly for their applications in medicine and materials because of their tunable physicochemical, optoelectronic and magnetic properties. In this review article, we focused on the applications of fluorinated porphyrinoids and their supramolecular systems and summarized the reports published on these chromophores in the past 5-6 years. The commercially available fluorinated porphyrinoids: meso-perfluorophenylporphyrin (TPPF20 ) perfluorophthalocyanine (PcF16 ) and meso-perfluorophenylcorrole (CorF15 ) have increased photo and oxidative stability due to the presence of fluoro groups. Because of their tunable properties and robustness toward oxidative damage these porphyrinoid-based chromophores continue to gain attention of researchers developing advanced functional materials for applications such as sensors, photonic devices, component for solar cells, biomedical imaging, theranostics and catalysts.

Rapid and accurate nucleobase detection using FnCas9 and its application in COVID-19 diagnosis.

Rapid detection of DNA/RNA pathogenic sequences or variants through point-of-care diagnostics is valuable for accelerated clinical prognosis, as witnessed during the recent COVID-19 outbreak. Traditional methods relying on qPCR or sequencing are tough to implement with limited resources, necessitating the development of accurate and robust alternative strategies. Here, we report FnCas9 Editor Linked Uniform Detection Assay (FELUDA) that utilizes a direct Cas9 based enzymatic readout for detecting nucleobase and nucleotide sequences without trans-cleavage of reporter molecules. We also demonstrate that FELUDA is 100% accurate in detecting single nucleotide variants (SNVs), including heterozygous carriers, and present a simple web-tool JATAYU to aid end-users. FELUDA is semi-quantitative, can adapt to multiple signal detection platforms, and deploy for versatile applications such as molecular diagnosis during infectious disease outbreaks like COVID-19. Employing a lateral flow readout, FELUDA shows 100% sensitivity and 97% specificity across all ranges of viral loads in clinical samples within 1hr. In combination with RT-RPA and a smartphone application True Outcome Predicted via Strip Evaluation (TOPSE), we present a prototype for FELUDA for CoV-2 detection closer to home.

Comparing a thioglycosylated chlorin and phthalocyanine as potential theranostic agents.

Herein we describe the design, efficient synthesis, and photophysical properties of two macrocycle dyes for cancer theranostics. This study compares a glycosylated chlorin with a glycosylated phthalocyanine designed to specifically target cancer, wherein the photophysical properties enable both fluorescence imaging and the sensitization of the formation of reactive oxygen species (ROS) for photodynamic therapy. Both the compounds show low darktoxicity (IC50 > 100 µM). The glycosylated phthalocyanine showed low phototoxicity (IC50 > 100 µM) while glycosylated chlorin showed high phototoxicity (IC50 = 1-2 µM). ZnPcGlc8 has low solubility and also form aggregates in aqueous media, thus resulting in minimal uptake in two different human breast cancer cell lines: MDA-MB-231 and MCF-7. The glycosylated chlorin however was efficiently taken up by these two cell lines, thus allows fluorescence imaging in cells and in xenograft tumor model in mice. In this study, we find that the chlorin conjugate is the more promising theranostic agent.

Exocyst Subcomplex Functions in Autophagosome Biogenesis by Regulating Atg9 Trafficking.

During autophagy, double-membrane vesicles called autophagosomes capture and degrade the intracellular cargo. The de novo formation of autophagosomes requires several vesicle transport and membrane fusion events which are not completely understood. We studied the involvement of exocyst, an octameric tethering complex, which has a primary function in tethering post-Golgi secretory vesicles to plasma membrane, in autophagy. Our findings indicate that not all subunits of exocyst are involved in selective and general autophagy. We show that in the absence of autophagy specific subunits, autophagy arrest is accompanied by accumulation of incomplete autophagosome-like structures. In these mutants, impaired Atg9 trafficking leads to decreased delivery of membrane to the site of autophagosome biogenesis thereby impeding the elongation and completion of the autophagosomes. The subunits of exocyst, which are dispensable for autophagic function, do not associate with the autophagy specific subcomplex of exocyst.

Compromising the plasma membrane as a secondary target in photodynamic therapy-induced necrosis.

Photodynamic therapy (PDT) is a non-invasive treatment widely applied to different cancers. The goal of PDT is the photo-induced destruction of cancer cells by the activation of different cell death mechanisms, including apoptosis and/or necrosis. Recent efforts focusing on understanding the mechanisms of cell death activated by PDT find that it depends on the type of photosensitizer (PS), targeted organelles, and nature of the light used. It is generally accepted that very short incubation times are required to direct the PS to the plasma membrane (PM), while longer periods result in the accumulation of the PS in internal compartments such as the endoplasmic reticulum or mitochondria. Glycosylation of the PS targets cancer via saccharide receptors on the cell surface, and is generally assumed that these compounds rapidly internalize and accumulate, e.g. in the endoplasmic reticulum. Herein we demonstrate that a minor fraction of a glycosylated chlorin compound residing at the PM of cancer cells can activate necrosis upon illumination by compromising the PM independently of the length of the incubation period. The results presented here show that the PM can also be targeted by glycosylated PS designed to accumulate in internal organelles. PS activation to induce necrosis by compromising the plasma membrane has the benefits of fast cell death and shorter irradiation times. The findings described here expand our understanding of the cellular damage induced by phototherapies, presenting the possibility of activating another cell death mechanism based on the incubation time and type of light used.

Septins are involved at the early stages of macroautophagy in S. cerevisiae.

Autophagy is a conserved cellular degradation pathway wherein double-membrane vesicles called autophagosomes capture long-lived proteins, and damaged or superfluous organelles, and deliver them to the lysosome for degradation. Septins are conserved GTP-binding proteins involved in many cellular processes, including phagocytosis and the autophagy of intracellular bacteria, but no role in general autophagy was known. In budding yeast, septins polymerize into ring-shaped arrays of filaments required for cytokinesis. In an unbiased genetic screen and in subsequent targeted analysis, we found autophagy defects in septin mutants. Upon autophagy induction, pre-assembled septin complexes relocalized to the pre-autophagosomal structure (PAS) where they formed non-canonical septin rings at PAS. Septins also colocalized with autophagosomes, where they physically interacted with the autophagy proteins Atg8 and Atg9. When autophagosome degradation was blocked in septin-mutant cells, fewer autophagic structures accumulated, and an autophagy mutant defective in early stages of autophagosome biogenesis (atg1Δ), displayed decreased septin localization to the PAS. Our findings support a role for septins in the early stages of budding yeast autophagy, during autophagosome formation.This article has an associated First Person interview with the first author of the paper.

A Structural Model of Nitro-Porphyrin Dyes Based on Spectroscopy and Density Functional Theory.

Nitro-porphyrins are an important class of commercial dyes with a range of potential applications. The nitro group is known to dramatically affect the photophysics of the porphyrin, but there are few systematic investigations of the contributing factors. To address this deficiency, we present spectroscopic studies of a series of nitro-porphyrins, accompanied by density functional theory calculations to elucidate their structures. In particular, we explore how the positions of the substituents affect the energy levels and nuclear geometry. As expected, nitro groups on the meso-phenyl rings cause small changes to the orbital energies by induction, while those at the ß-pyrrole positions more strongly conjugate into the aromatic system. In addition, however, we find evidence that ß-pyrrole nitro groups distort the porphyrin, creating two non-planar conformations with distinct properties. This unexpected result helps explain the anomalous photophysics of nitro-porphyrins reported throughout the literature, including inhomogeneous line broadening and biexponential fluorescence decay. © 2017 Wiley Periodicals, Inc.

Practical, high-yield synthesis of thiol-terminated diacetylenes for formation of conductive monolayers.

Self-assembled monolayers of thiol terminated conjugated diacetylenes can be cross-linked using ultraviolet light to form highly conjugated polydiacetylenic conductive monolayers1; however, the reported syntheses of the diacetylene monomers present numerous problems that prevent the wide spread application of these in functional materials. We report a redesigned four-step synthesis that proceeds in 75-80 % overall yields and allows gram scale production of an array of thiol terminated conjugated diacetylenes, thereby allowing examination and application of these low-dimensional conductive materials.

Synthesis and cell phototoxicity of a triply bridged fused diporphyrin appended with six thioglucose units.

A triply bridged fused diporphyrin appended with six thioglucose units is reported. This new, chemically and photochemically stable amphiphilic compound is taken up by breast cancer cells and causes cell death upon light exposure. Photophysical studies reveal absorption bands in the near IR region, and photosensitized formation of singlet oxygen in high quantum yields.

Photophysics of glycosylated derivatives of a chlorin, isobacteriochlorin and bacteriochlorin for photodynamic theragnostics: discovery of a two-photon-absorbing photosensitizer.

The photophysical properties of a chlorin, isobacteriochlorin and bacteriochlorin built on a core tetrapentafluorophenylporphyrin (TPPF20 ) and the nonhydrolyzable para thioglycosylated conjugates of these chromophores are presented. The photophysical characterization of these compounds was done in three different solvents to correlate with different environments in cells and tissues. Compared with TPPF20 other dyes have greater absorption in the red region of the visible spectrum and greater fluorescence quantum yields. The excited state lifetimes are from 3 to 11 ns. The radiative and nonradiative rate constants for deactivation of the excited state were estimated from the fluorescence quantum yield and excited state lifetime. The data indicate that the bacteriochlorin has strong absorption bands near 730 nm and efficiently enters the triplet manifold. The isobacteriochlorin has a 40-70% fluorescence quantum yield depending on solvent, so it may be a good fluorescent tag. The isobacteriochlorins also display enhanced two-photon absorption, thereby allowing the use of 860 nm light to excite the compound. While the two-photon cross section of 25 GM units is not large, excitation of low chromophore concentrations can induce apoptosis. The glycosylated compounds accumulate in cancer cells and a head and neck squamous carcinoma xenograft tumor model in mice. These compounds are robust to photobleaching.

Rational design of a zinc phthalocyanine binding protein.

Phthalocyanines have long been used as primary donor molecules in synthetic light-powered devices due to their superior properties when compared to natural light activated molecules such as chlorophylls. Their use in biological contexts, however, has been severely restricted due to their high degree of self-association, and its attendant photoquenching, in aqueous environments. To this end we report the rational redesign of a de novo four helix bundle di-heme binding protein into a heme and Zinc(II) phthalocyanine (ZnPc) dyad in which the ZnPc is electronically and photonically isolated. The redesign required transformation of the homodimeric protein into a single chain four helix bundle and the addition of a negatively charge sulfonate ion to the ZnPc macrocycle. To explore the role of topology on ZnPc binding two constructs were made and the resulting differences in affinity can be explained by steric interference of the newly added connecting loop. Singular binding of ZnPc was verified by absorption, fluorescence, and magnetic circular dichroism spectroscopy. The engineering guidelines determined here, which enable the simple insertion of a monomeric ZnPc binding site into an artificial helical bundle, are a robust starting point for the creation of functional photoactive nanodevices.

Adaptive organic nanoparticles of a teflon-coated iron (III) porphyrin catalytically activate dioxygen for cyclohexene oxidation.

Self-organized organic nanoparticles (ONP) are adaptive to the environmental reaction conditions. ONP of fluorous alkyl iron(III) porphyrin catalytically oxidize cyclohexene to the allylic oxidation products. In contrast, the solvated metalloporphyrin yields both allylic oxidation and epoxidation products. The ONP system facilitates a greener reaction because about 89% reaction medium is water, molecular oxygen is used in place of synthetic oxidants, and the ambient reaction conditions used require less energy. The enhanced catalytic activity of these ONP is unexpected because the metalloporphyrins in the nanoaggregates are in the close proximity and the TON should diminish by self-oxidative degradation. The fluorous alkyl chain stabilizes the ONP toward self-oxidative degradation.

Synthesis and photophysics of an octathioglycosylated zinc(II) phthalocyanine.

A water soluble zinc(II) phthalocyanine symmetrically appended with eight thioglucose units was synthesized from commercially available hexadecafluorophthalocyaninatozinc(II) by controlled nucleophilic substitution of the peripheral fluoro groups. The photophysical properties and cancer cell uptake studies of this nonhydrolyzable thioglycosylated phthalocyanine are reported. The new compound has amphiphilic character, is chemically stable, and can potentially be used as a photosensitizer in photodynamic therapy.

Hierarchical organization of a robust porphyrin cage self-assembled by hydrogen bonds.

Porphyrins appended with four rigid hydrogen bonding motifs on the meso positions were synthesized and self-assembled into a cofacial cage with four complementary bis(decyl)melamine units in dry solvents. The hydrocarbon chains on the melamine mediate the formation of nanofilms on surfaces as the solvent slowly evaporates.

Synthesis and photophysical properties of thioglycosylated chlorins, isobacteriochlorins, and bacteriochlorins for bioimaging and diagnostics.

The facile synthesis and photophysical properties of three nonhydrolyzable thioglycosylated porphyrinoids are reported. Starting from meso-perfluorophenylporphyrin, the nonhydrolyzable thioglycosylated porphyrin (PGlc4), chlorin (CGlc4), isobacteriochlorin (IGlc4), and bacteriochlorin (BGlc4) can be made in 2-3 steps. The ability to append a wide range of targeting agents onto the perfluorophenyl moieties, the chemical stability, and the ability to fine-tune the photophysical properties of the chromophores make this a suitable platform for development of biochemical tags, diagnostics, or as photodynamic therapeutic agents. Compared to the porphyrin in phosphate buffered saline, CGlc4 has a markedly greater absorbance of red light near 650 nm and a 6-fold increase in fluorescence quantum yield, whereas IGlc4 has broad Q-bands and a 12-fold increase in fluorescence quantum yield. BGlc4 has a similar fluorescence quantum yield to PGlc4 (<10%), but the lowest-energy absorption/emission peaks of BGlc4 are considerably red-shifted to near 730 nm with a nearly 50-fold greater absorbance, which may allow this conjugate to be an effective PDT agent. The uptake of CGlc4, IGlc4, and BGlc4 derivatives into cells such as human breast cancer cells MDA-MB-231 and K:Molv NIH 3T3 mouse fibroblast cells can be observed at nanomolar concentrations. Photobleaching under these conditions is minimal.

Self-organized nanofibers and nanorods of porphyrins bearing hydrogen bonding motifs.

Porphyrins bearing uracyl motifs at the four meso positions self-organize via homo-complementary hydrogen bonds and pi-stacking into nanofibers, nanorods and thin films on mica and glass surfaces depending on deposition conditions.