ABSTRACT
In clinical applications, such as PhotoDynamic Therapy, direct singlet-oxygen detection through its luminescence in the near-infrared range (1270 nm) has been a challenging task due to its low emission probability and the lack of suitable single-photon detectors. Here, we propose a practical setup based on a negative-feedback avalanche diode detector that is a viable alternative to the current state-of-the art for different clinical scenarios, especially where geometric collection efficiency is limited (e.g. fiber-based systems, confocal microscopy, scanning systems etc.). The proposed setup is characterized with Rose Bengal as a standard photosensitizer and it is used to measure the singlet-oxygen quantum yield of a new set of photosensitizers for site-selective photodynamic therapy.
ABSTRACT
A tripeptide-perylene diimide (PDI) conjugate self-assembles into PDI@ß-sheet nanohelices, whose local conformations are sensitive to the external stimuli of concentration, heating and ultrasound, showing stimulus-responsive supramolecular chirality.
Subject(s)
Imides/chemistry , Nanoparticles/chemistry , Oligopeptides/chemistry , Perylene/analogs & derivatives , Microscopy, Electron, Scanning , Microscopy, Electron, Transmission , Models, Molecular , Molecular Conformation , Molecular Structure , Nanoparticles/ultrastructure , Perylene/chemistry , Spectroscopy, Fourier Transform Infrared , X-Ray DiffractionABSTRACT
We report that two molecular building blocks differ only by two protons, yet they form totally different nanostructures. The protonated one self-organized into hollow nanospheres (~200 nm), whereas the one without the protons self-assembled into rectangular plates. Consequently, the geometrically defined nanoassemblies exhibit radically different properties. As self-assembly directing units, protons impart ion-pairing and hydrogen-bonding probabilities. The plate-forming nanosystem fluoresces weakly, probably due to energy transfer among chromophores (Φ < 0.2), but the nanospheres emit strong yellow fluorescence (Φ ≈ 0.58-0.85).
ABSTRACT
In this paper, we report that a 1,7-bis-pyridinoyl perylene diimide amphiphile undergoes distinctly different self-assembly in methanol compared to ethanol. This amphiphile forms hollow nanospheres in methanol, whereas in ethanol, it self-assembles into microrose flowers which consist of several soft nanoplates packing like rose petals. Studies of the concentration-dependent absorption spectra confirmed this solvent effect. The most distinct spectral features were the A(0-0)/A(0-1) and A(0-0)/A(S)(0-)(S)(2) values. These spectral changes were explained in terms of the Franck-Condon factors.
ABSTRACT
Herein, we report the ultrasound-induced modulations of the morphologies and underlying molecular structures of tetrapeptide 1-D self-assembly. The self-assembly of the tetrapeptide (TTR108-111) precipitating out of the 1:1 mixed methanol/water is modulated from microtapes into nanotapes, nanofibers, and then bundles of nanorods when subjected to sonication for a period. The sonication-treated and untreated self-assemblies all give a set of equatorial pattern and a series of meridional pattern, indications of a typical "cross-beta-structure" as the core structural motif. FTIR data indicate that all the assemblies contain a mixed pattern of beta-sheets (dominant) and unstructured conformations (minor), and the relative proportion of unbound structures to beta-sheets is as a function of sonication time, suggesting an ultrasound-induced modulation of beta-sheet interactions. Accordingly, a possible model regarding a dynamic equilibrium between re-dissolution and re-assembling processes, e.g., a typical sonocrystallization process was proposed for such ultrasound-induced modulations of morphologies and underlying molecular structures.
