Tunable Semiconducting Polymer Nanoparticles with INDT-Based Conjugated Polymers for Photoacoustic Molecular Imaging.

Photoacoustic imaging combines both excellent spatial resolution with high contrast and specificity, without the need for patients to be exposed to ionizing radiation. This makes it ideal for the study of physiological changes occurring during tumorigenesis and cardiovascular disease. In order to fully exploit the potential of this technique, new exogenous contrast agents with strong absorbance in the near-infrared range, good stability and biocompatibility, are required. In this paper, we report the formulation and characterization of a novel series of endogenous contrast agents for photoacoustic imaging in vivo. These contrast agents are based on a recently reported series of indigoid π-conjugated organic semiconductors, coformulated with 1,2-dipalmitoyl-sn-glycero-3-phosphocholine, to give semiconducting polymer nanoparticles of about 150 nm diameter. These nanoparticles exhibited excellent absorption in the near-infrared region, with good photoacoustic signal generation efficiencies, high photostability, and extinction coefficients of up to three times higher than those previously reported. The absorption maximum is conveniently located in the spectral region of low absorption of chromophores within human tissue. Using the most promising semiconducting polymer nanoparticle, we have demonstrated wavelength-dependent differential contrast between vasculature and the nanoparticles, which can be used to unambiguously discriminate the presence of the contrast agent in vivo

A comprehensive study of natural organic dyes in historical mediterranean textil by liquid chromatography with photodiode array and mass spectrometric detection

Thesis involves an optimized chromatographic and spectroscopic study of textiles, dyed with natural organic dyestuffs, aiming at the identification of chromophore constituents and their possible degradation products. Liquid chromatography - mass spectrometry coupled with photodiode array detection has been applied for the samples’ analyses after the selective extraction of chromophores from the substrate. The under investigation natural organic dyes are those with a particular cultural value since they have been widely used for textiles staining in the Mediterranean region since Antiquity. Improved “Mild Acid Hydrolysis” with methanol/formic acid enabled the observation of intact organic dyes from the silk textiles, while a water/ACN solvent system has also been employed for the pre treatment of dyestuffs from both reference and silk samples, which has successfully preserved the chemical information of dye compounds in order to create a comprehensive database for the characterization of natural organic dyes in further studies. Moreover, three different chromatographic programs were applied and compared in LC-PDA-MS, and the best separation result from Program B has been employed to the analysis of the real samples from Turkish silk textiles created by a historical dyeing recipes, and a certain amount of effective information in terms of qualitative analysis has been clarified; Περίληψη: Η παρούσα διπλωματική εργασία αφορά την βελτιστοποιημένη χρωματογραφική και φασματοσκοπική μελέτη κλωστοϋφαντουργικών προϊόντων βαμμένων με φυσικές οργανικές χρωστικές, με στόχο την ταυτοποίηση των έγχρωμων συστατικών τους καθώς και πιθανών προϊόντων αποικοδόμησης τους. Οι υπό διερεύνηση φυσικές οργανικές χρωστικές είναι ιδιαίτερης πολιτιστικής αξίας, δεδομένου ότι έχουν χρησιμοποιηθεί ευρέως για την βαφή υφασμάτων στην περιοχή της Μεσογείου από την Αρχαιότητα. Για την εκχύλιση των έγχρωμων ενώσεων των φυσικών οργανικών χρωστικών από τα δείγματα αναφοράς καθώς και από τα ιστορικά δείγματα μεταξιού, εφαρμόστηκε μία ήπια μέθοδος εκχύλισης με σύστημα διαλυτών νερού/ACN σε λουτρό υπερήχων. Επιπλέον, για την απόσπαση των χρωστικών από τα ιστορικά δείγματα προηγήθηκε στάδιο προκατεργασίας με μίγμα μεθανόλης/μυρμηκικού οξέος και θέρμανση σε ήπιες συνθήκες. Η εφαρμογή ήπιων συνθηκών εκχύλισης επέτρεψε την απόσπαση των έγχρωμων ενώσεων των φυσικών οργανικών χρωστικών, διατηρώντας επιτυχώς το σύνολο των χημικών πληροφορίων που θα μας επέτρεπαν τον απόλυτο χαρακτηρισμό των φυσικών χρωστικών. Για την ανάλυση των δειγμάτων μετά την εκλεκτική εκχύλιση των έγχρωμων ενώσεων από τα υποστρώματα, εφαρμόστηκε η υγρή χρωματογραφία – φασματοσκοπία μάζας, LCMS. Συνολικά εφαρμόστηκαν και συγκρίθηκαν τρία διαφορετικά προγράμματα LCMS, εκ των οποίων τα καλύτερα αποτελέσματα διαχωρισμού και ταυτοποίησης επιτεύχθηκαν με το Πρόγραμμα Β. Το πρόγραμμα αυτό εφαρμόστηκε και για την ανάλυση των ιστορικών δειγμάτων από τουρκικά μεταξωτά υφάσματα, βαμμένα βάσει ιστορικών συνταγών βαφής

Analytical methods for determination of anthraquinone dyes in historical textiles: a review

Historical and archaeological textiles are among the most crucial and vulnerable records of our social and cultural history. Analysis of organic colorants found in these materials is unquestionably one of the most powerful tools to understand historical developments, cultural exchanges, and progress in science and technology. Natural anthraquinones represent the most commonly used natural colorants for textile dyeing until the late 19th century. The identification of anthraquinones in cultural heritage objects is a challenging task due to the small size of historical samples, diversity of potential dye sources, variable extraction procedures and dyeing methods, complex chemical constitution, structurally analogous chromophores, and possible presence of degradation products and contaminants. Developments in dye analysis of historical interest have originated and expanded along with the general advances in analytical science. In the last few decades, a close cooperation between science and cultural heritage disciplines contributed enormously to this field. The topic of historical dyes and their analysis in textiles, artworks, archaeological objects and cultural heritage materials has been reviewed several times in the last fifteen years. However, no review has been published to-date exclusively on the analysis of anthraquinone colorants in historical and archaeological textiles. Overall, liquid chromatography (LC)-based techniques have been the most widely used method for anthraquinone dye analysis. Owing to increasing demand of minimally invasive/non-invasive techniques, recent developments of novel techniques have resulted in the availability of many alternative/complementary methods to LC-based analysis. This review begins with a short overview of sources, chemistry and importance of natural anthraquinone dyes found in historical textiles before turning to a detailed discussion on developments involving established and emerging analytical techniques of anthraquinone dye analysis for textile cultural heritage materials. To illustrate the state-of-the-art, representative examples of analytical techniques highlighting their advantages, limitations and applicability are also presented

Designing light-driven rotary molecular motors

The ability to induce and amplify motion at the molecular scale has seen tremendous progress ranging from simple molecular rotors to responsive materials. In the two decades since the discovery of light-driven rotary molecular motors, the development of these molecules has been extensive; moving from the realm of molecular chemistry to integration into dynamic molecular systems. They have been identified as actuators holding great potential to precisely control the dynamics of nanoscale devices, but integrating molecular motors effectively into evermore complex artificial molecular machinery is not trivial. Maximising efficiency without compromising function requires conscious and judicious selection of the structures used. In this perspective, we focus on the key aspects of motor design and discuss how to manipulate these properties without impeding motor integrity. Herein, we describe these principles in the context of molecular rotary motors featuring a central double bond axle and emphasise the strengths and weaknesses of each design, providing a comprehensive evaluation of all artificial light-driven rotary motor scaffolds currently present in the literature. Based on this discussion, we will explore the trajectory of research into the field of molecular motors in the coming years, including challenges to be addressed, potential applications, and future prospects.</p

Designing light-driven rotary molecular motors

The ability to induce and amplify motion at the molecular scale has seen tremendous progress ranging from simple molecular rotors to responsive materials. In the two decades since the discovery of light-driven rotary molecular motors, the development of these molecules has been extensive; moving from the realm of molecular chemistry to integration into dynamic molecular systems. They have been identified as actuators holding great potential to precisely control the dynamics of nanoscale devices, but integrating molecular motors effectively into evermore complex artificial molecular machinery is not trivial. Maximising efficiency without compromising function requires conscious and judicious selection of the structures used. In this perspective, we focus on the key aspects of motor design and discuss how to manipulate these properties without impeding motor integrity. Herein, we describe these principles in the context of molecular rotary motors featuring a central double bond axle and emphasise the strengths and weaknesses of each design, providing a comprehensive evaluation of all artificial light-driven rotary motor scaffolds currently present in the literature. Based on this discussion, we will explore the trajectory of research into the field of molecular motors in the coming years, including challenges to be addressed, potential applications, and future prospects

DEVELOPMENT OF INNOVATIVE ANALYTICAL PROCEDURES FOR THE IDENTIFICATION OF ORGANIC COLORANTS OF INTEREST IN ART AND ARCHAEOLOGY

Organic colorants obtained from natural sources such as plants and insects have been widely used as textile dyes or lake pigments for paintings, sculptures and other kinds of polychrome works of art since ancient times until the second half of the 19th century, when the industrial production of synthetic dyes had begun. Chemical investigation of such materials is of great interest to art historians, restorers and art conservators. In fact, the analysis of ancient dyes can be of help in revealing what kind of substances were available in particular periods and geographical areas, providing valuable data about the historical context of a work of art, the lifestyle and the technical knowledge reached by a certain population in a given historical age, shedding light on the possible interactions between different cultures as well as the trade routes and commercial transactions which may have allowed the usage of a particular colorant far from its geographical source. Moreover, discovering nature and origin of the coloring substances employed in the production of a work of art can provide precious information regarding its original color and appearance, thus offering new insights into the artist\u2019s choices and original intention, the techniques used and the dates ante quem and post quem the art object was produced, possibly leading to the uncovering of falsifications and forgeries. Furthermore, scientific analysis applied to the study of art materials and, specifically, of pigments and dyes, may contribute to assess suitable conservation and restoration procedures to be applied to paint defects and degraded pigments in works of art of any kind; in fact, time, environmental conditions and several other circumstances unavoidably cause damage and deterioration to art objects and artifacts, which therefore require careful conservation to be safeguarded as important elements of our cultural heritage. The identification of historical dyes is currently one of the most challenging tasks in the chemical investigation of art materials, for three main reasons. First of all, colorants in works of art and archaeological textiles are usually included in complex matrixes such as paint layers or cloth fibers, where they are present in mixture with other substances, such as binding media or mordants, and in very low concentrations due to their high tinting power. Besides, sampling of art objects is always limited to microscopic fragments, when at all allowed. An additional analytical challenge is posed by the remarkable susceptibility to deterioration of organic materials, which can undergo a number of chemical degradation processes leading to the formation of specimens with a different molecular structure in comparison to the primary organic dye. Several instrumental techniques, of both chromatographic and spectroscopic type, have been employed for the detection of colorants over the years. In recent times, the great potential of SERS has been appreciated, as the adsorption of the analyte on nanosized metal surfaces, resulting in a significant enhancement of the Raman scattering intensity and strong fluorescence quenching, leads to obtaining a specific fingerprint for many organic substances, markedly reducing the amount of sample that would be otherwise required for analysis. However, on the other hand, SERS poses a whole set of challenges, as only a small number of molecules have been studied so far and the necessity of searchable databases of reference materials is still to be fulfilled; moreover, SERS is not a separation technique, and therefore it often suffers from spectral interferences due to the presence of impurities or matrix components. In this context, the present doctoral thesis work aims to the improvement of pre-existing analytical methods as well as to the development of innovative procedures for the identification of organic dyes of artistic and archaeological interest, with special attention being devoted to SERS. The scientific results here reported are the fruit of a research activity carried out both at Universit\ue0 degli Studi di Milano and in the Department of Scientific Research of the Metropolitan Museum of Art (New York, USA). First of all, an effective experimental protocol for SERS analyses on silver colloids aggregated by NaClO4 was optimized and a wide spectral database of historical natural colorants was thus assembled, containing among the others the spectra of several dyes never studied before. The SERS procedure developed, in association with complementary analytical investigations of different kind, was then successfully applied to the identification of a yellow dye in ancient wool threads from the Libyan Sahara and to the detection of several colorants in Kaitag textiles, a unique embroidered textile art form from Caucasus. Work carried out at the Metropolitan Museum of Art comprises a comparative study of the most relevant SERS approaches recently introduced in art analysis: relative merits and drawbacks of HF hydrolysis and non-hydrolysis methodologies were evaluated, and a two-step procedure for the investigation of organic dyes in works of art was proposed. Results obtained from reference dyes were compared with those achieved on samples taken from a number of artworks and ancient objects, including masterpiece oil paintings, musical instruments, archaeological textiles and lake pigments. Watercolors from a historical Winsor & Newton handbook dating to 1887 were then characterized using SERS and ordinary Raman spectroscopies, and a database of original art materials was acquired, to be used for dating as well as in authentication and identification studies. Also, coupling of TLC and SERS was investigated and tested as a promising tool for the separation and identification of the main alkaloid constituents of Syrian rue dye. Finally, a comprehensive Raman study of monobromoindigo, component of the historical colorant Tyrian purple, was performed, together with a detailed assignment of the spectral lines observed by comparison with density functional theory (DFT) quantum mechanical calculations

Peptide-Directed Supramolecular Self-Assembly of N-Substituted Perylene Imides

Synthetic peptides offer enormous potential to encode the assembly of molecular electronic components, provided that the complex range of interactions is distilled into simple design rules. Herein is reported a spectroscopic investigation of aggregation in an extensive series of peptide-perylene imide conjugates designed to interrogate the effect of structural variations. Throughout the course of this study, the self-assembly and photophysical properties of the compounds are explored to better understand the behavior and application of these materials. Three principal avenues of inquiry are applied: (1) the evaluation of structure-property relationships from a thermodynamic perspective, (2) the examination of peptide chiral effects upon properties and self-assembly, and (3) an application of the understanding gained from rationally designed systems to effectively utilize naturally optimized peptides in bio-organic electronics. By fitting different contributions to temperature-dependent optical absorption spectra, this study quantifies both the thermodynamics and the nature of aggregation for peptides with incrementally varying hydrophobicity, charge density, length, amphiphilic substitution with a hexyl chain, and stereocenter inversion. Coarse effects like hydrophobicity and hexyl substitution are seen to have the greatest impact on binding thermodynamics, which are evaluated separately as enthalpic and entropic contributions. Moreover, significant peptide packing effects are resolved via stereocenter inversion studies, particularly when examining the nature of aggregates formed and the coupling between π-electronic orbitals. Peptide chirality overall is seen to influence the self-assembly of the perylene imide cores into chiral nanofibers, and peptide stereogenic positions, stereochemical configurations, amphiphilic substitution, and perylene core modification are evaluated with respect to chiral assembly. Stereocenters in peptide residue positions proximal to the perylene core (1-5 units) are seen to impart helical chirality to the perylene core, while stereocenters in more distal residue positions do not exert a chiral influence. Diastereomers involving stereocenter inversions within the proximal residues consequently manifest spectroscopically as pseudo-enantiomers. Increased side-chain steric demand in the proximal positions gives a similar chiral influence but exhibits diminished Cotton Effect intensity with additional longer wavelength features attributed to interchain excimers. Amphiphilic substitution of a peptide with an alkyl chain disrupts chiral self-assembly, while an amphiphilic structure achieved through the modification of the perylene imide core with a bisester moiety prompts strongly exciton-coupled, chiral, solvent-responsive self-assembly into long nanofilaments. Informed by rationally designed sequences, and capitalizing upon the optimization seen in many natural systems, specific peptide sequences designed by inspection of protein-protein interfaces have been identified and used as tectons in hybrid functional materials. An 8-mer peptide derived from an interface of the peroxiredoxin family of self-assembling proteins is exploited to encode the assembly of perylene imide-based organic semiconductor building blocks. By augmenting the peptide with additional functionality to trigger aggregation and manipulate the directionality of peptide-semiconductor coupling, a series of hybrid materials based on the natural peptide interface is presented. Using spectroscopic probes, the mode of self-assembly and the electronic coupling between neighboring perylene units is shown to be strongly affected by the number of peptides attached, and by their backbone directionality. The disubstituted material with peptides extending in the N-C direction away from the perylene core exhibits strong coupling and long-range order, which are both attractive properties for electronic device applications. A bio-organic field-effect transistor is fabricated using this material, highlighting the possibilities of exploiting natural peptide tectons to encode self-assembly in other functional materials and devices. These results advance the development of a quantitative framework for establishing structure-function relationships that will underpin the design of self-assembling peptide electronic materials. The results further advance a model for adapting natural peptide sequences resident in β-continuous interfaces as tectons for bio-organic electronics