Peptide materials in dye sensitized solar cells

In September 2015, the ONU approved the Global Agenda for Sustainable Development, by which all countries of the world are mobilized to adopt a set of goals to be achieved by 2030. Within these goals, the aim of having a responsible production and consumption, as well as taking climate action, made is necessary to design new eco-friendly materials. Another important UN goal is the possibility for all the countries in the world to access affordable energy. The most promising and renewable energy source is solar energy. Current solar cells use non-biodegradable substrates, which generally contribute to environmental pollution at the end of their life cycles. Therefore, the production of green and biodegradable electronic devices is a great challenge, prompted by the need to find sustainable alternatives to the current materials, particularly in the field of dye-sensitized solar cells. Within the green alternatives, biopolymers extracted from biomass, such as polysaccharides and proteins, represent the most promising materials in view of a circular economy perspective. In particular, peptides, due to their stability, good self-assembly properties, and ease of functionalization, may be good candidates for the creation of dye sensitized solar cell (DSSC) technology. This work shows an overview of the use of peptides in DSSC. Peptides, due to their unique self-assembling properties, have been used both as dyes (mimicking natural photosynthesis) and as templating materials for TiO2 morphology. We are just at the beginning of the exploitation of these promising biomolecules, and a great deal of work remains to be done

Sonogashira cross-couplings of dehydroamino acid derivatives and phenylacetylenes

Several phenylacetylenes were coupled under Sonogashira cross coupling conditions with the methyl esters of N-(tert-butoxycarbonyl)-(E)-beta-bromo or beta, beta-dibromodehydroalanine to give respectively beta-substituted or beta,beta-bis-substituted dehydroalanines. The beta-substituted dehydroalanines were obtained in good to high yields (60-90%) under the usual Sonogashira conditions (1 equiv. of the phenylacetylene, 1 mol% Pd(PPh3)4, 2 mol% CuI 18 equiv. NEt3 in acetonitrile, 24h at rt) with maintenance of the stereochemistry. The beta,beta-bis-substituted dehydroalanines were in turn obtained in moderate to good yields (44-63%) requiring modified Sonogashira conditions (4 equiv. of the phenylacetylene,10 mol% PdCl2(PPh3)2, 20 mol% CuI, 1.4 equiv. Cs2CO3, 2h at reflux of acetonitrile). In the latter reactions some phenylacetylene dimer and the (E)-isomer of the mono substituted coupled products were also isolated in some extent. The Sonogashira products which were obtained from the 4-bromophenylacetylene were reacted with functionalized benzo[b]thiophenes under C-C or C-N palladium-catalyzed cross-coupling conditions. Preliminary fluorescence studies were performed for mono and disubstituted 4-aminophenylacetylenic dehydroamino acids and for the benzo[b]thiophene derivatives. The results showed that some of the dehydroalanines prepared can be used as fluorescent probes.Fundação para a Ciência e Tecnologia - POCTI/99/QUI/32689, SFRH/BD/4709/2001

Dissecting the intracellular signalling and fate of a DNA nanosensor by super-resolution and quantitative microscopy

DNA nanodevices have been developed as platforms for the manipulation of gene expression, delivery of molecular payloads, and detection of various molecular targets within cells and in other complex biological settings. Despite efforts to translate DNA nanodevices from the test tube (in vitro) to living cells, their intracellular trafficking and functionality remain poorly understood. Herein, quantitative and super-resolution microscopy approaches were employed to track and visualise, with nanometric resolution, the molecular interactions between a synthetic DNA nanosensor and transcription factors in intracellular compartments. Specifically, fluorescence resonance energy transfer microscopy, fluorescence correlation spectroscopy, fluorescence lifetime imaging microscopy and multicolour single-molecule localisation microscopy were employed to probe the specific binding of the DNA nanosensor to the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kappa B). We monitored the mobility, subcellular localisation and degradation of the DNA nanosensor inside living prostate cancer PC3 cells. Super-resolution imaging enabled the direct visualisation of the molecular interactions between the synthetic DNA nanosensors and the NF-kappa B molecules in cells. This study represents a significant advance in the effective detection as well as understanding of the intracellular dynamics of DNA nanosensors in a complex biological milieu

Porphyrins Through the Looking Glass: Spectroscopic and Mechanistic Insights in Supramolecular Chirogenesis of New Self-Assembled Porphyrin Derivatives

The solvent driven aggregation of porphyrin derivatives, covalently linked to a L- or D-prolinate enantiomer, results in the stereospecific formation of species featuring remarkable supramolecular chirality, as a consequence of reading and amplification of the stereochemical information stored in the proline-appended group. Spectroscopic, kinetic, and topographic SEM studies gave important information on the aggregation processes, and on the structures of the final chiral architectures. The results obtained may be the seeds for the construction of stereoselective sensors aiming at the detection, for example, of novel emergent pollutants from agrochemical, food, and pharmaceutical industry

Chiral selectivity of porphyrin-ZnO nanoparticle conjugates

Recognition of enantiomers is one of the most arduous challenges in chemical sensor development. Although several chiral systems exist, their effective exploitation as the sensitive layer in chemical sensors is hampered by several practical implications that hinder stereoselective recognition in solid state. In this paper, we report a new methodology to efficiently prepare chiral solid films, by using a hybrid material approach where chiral porphyrin derivatives are grafted onto zinc oxide nanoparticles. Circular dichroism (CD) evidences that the solid-state film of the material retains supramolecular chirality due to porphyrin interactions, besides an additional CD feature in correspondence of the absorbance of ZnO (375 nm), suggesting the induction of chirality in the underlying zinc oxide nanoparticles. The capability of hybrid material to detect and recognize vapors of enantiomer pairs was evaluated by fabricating gas sensors based on quartz microbalances. Chiral films of porphyrin on its own were used for comparison. The sensor based on functionalized nanostructures presented a remarkable stereoselectivity in the recognition of limonene enantiomers, whose ability to intercalate in the porphyrin layers makes this terpene an optimal chiral probe. The chiroptical and stereoselective properties of the hybrid material confirm that the use of porphyrin-capped ZnO nanostructures is a viable route for the formation of chiral selective surfaces. © 2019 American Chemical Society

Tunable supramolecular chirogenesis in the self-assembling of amphiphilic porphyrin triggered by chiral amines

Supramolecular chirality is one of the most important issues in different branches of science and technology, as stereoselective molecular recognition, catalysis, and sensors. In this paper, we report on the self-assembly of amphiphilic porphyrin derivatives possessing a chiral information on the periphery of the macrocycle (i.e., D- or L-proline moieties), in the presence of chiral amines as co-solute, such as chiral benzylamine derivatives. The aggregation process, steered by hydrophobic effect, has been studied in aqueous solvent mixtures by combined spectroscopic and topographic techniques. The results obtained pointed out a dramatic effect of these ligands on the morphology and on the supramolecular chirality of the final self-assembled structures. Scanning electron microscopy topography, as well as fluorescence microscopy studies revealed the formation of rod-like structures of micrometric size, different from the fractal structures formerly observed when the self-assembly process is carried out in the absence of chiral amine co-solutes. On the other hand, comparative experiments with an achiral porphyrin analogue strongly suggested that the presence of the prolinate moiety is mandatory for the achievement of the observed highly organized suprastructures. The results obtained would be of importance for unraveling the intimate mechanisms operating in the selection of the homochirality, and for the preparation of sensitive materials for the detection of chiral analytes, with tunable stereoselectivity and morphology

Seeding chiral ensembles of prolinated porphyrin derivatives on glass surface: simple and rapid access to chiral porphyrin films

An easy and fast method to achieve chiral porphyrin films on glass is herein reported. The on-surface formation of organized supramolecular architectures with distinctive and remarkable chiroptical features strictly depends on the macrocycles used, the solvent chosen for the casting deposition, and most importantly, on the roughness of the glass slide. Dynamic light scattering studies performed on 10−4–10−6 M porphyrin solutions revealed the presence of small porphyrin aggregates, whose size and number increase depending on the initial concentration. Once transferred on surface, these protoaggregates act as nucleation seeds for the following, self-assembling into larger structures upon solvent evaporation, with a process driven by a fine balance between intermolecular and molecule–substrate interactions. The described method represents a straightforward way to fabricate porphyrin-based chiral surfaces onto a transparent and economic substrate in few minutes. The results obtained can be particularly promising for the development of sensors based on stereoselective optical active films, targeting the detection of chiral analytes of practical relevance, such as the so-called emerging pollutants released in the environment from agrochemical, food, and pharmaceutical manufacturing

Alginate Microsponges as a Scaffold for Delivery of a Therapeutic Peptide against Rheumatoid Arthritis

The quest for biocompatible drug-delivery devices that could be able to open new administration routes is at the frontier of biomedical research. In this contribution, porous polysaccharide-based microsponges based on crosslinked alginate polymers were developed and characterized by optical spectroscopy and nanoscopic microscopy techniques. We show that macropores with a size distribution ranging from 50 to 120 nm enabled efficient loading and delivery of a therapeutic peptide (CIGB814), presently under a phase 3 clinical trial for the treatment of rheumatoid arthritis. Alginate microsponges showed 80% loading capacity and sustained peptide release over a few hours through a diffusional mechanism favored by partial erosion of the polymer scaffold. The edible and biocompatible nature of alginate polymers open promising perspectives for developing a new generation of polysaccharide-based carriers for the controlled delivery of peptide drugs, exploiting alternative routes with respect to intravenous administration

Aggregation properties of a therapeutic peptide for rheumatoid arthritis: a spectroscopic and molecular dynamics study

The biological properties of therapeutic peptides, such as their pharmacokinetics and pharmacodynamics, are correlated with their structure and aggregation properties. Herein, we studied the aggregation properties of a therapeutic peptide (CIGB-814), currently in phase 2 clinical trial, for the treatment of rheumatoid arthritis over a wide range of concentrations (μM–mM). We applied spectroscopic techniques (fluorescence, circular dichro- ism, resonance, and dynamic light scattering), atomic force microscopy, and molecular dynamics simulations to determine the aggregation mechanism of CIGB-814. We found that the hierarchical aggregation of CIGB-814 at micromolar concentrations was initiated by the formation of peptide oligomers. Subsequently, the peptide oligomers trigger the nucleation and growth of peptide nanostructures (cac = 123 μM), ultimately leading to the fibrillization of CIGB-814 (cac’ = 508 μM). These results pave the way for a deeper understanding of the CIGB-814 therapeutic activity and may give important insights on its pharmacokinetics