A non‐gassing electroosmotic pump with sandwich of poly(2‐ethyl aniline)‐Prussian blue nanocomposite and PVDF membrane

Low voltage, non‐gassing electroosmotic pump (EOP) was assembled with poly(2‐ethyl aniline) (EPANI)‐Prussian blue nanocomposite electrode and commercially available hydrophilic PVDF membranes. The nanocomposite material combines excellent oxidation/reduction capacity of EPANI with exceptional stability by shuttling of proton between Prussian blue nanoparticles and EPANI redox matrix. The flow rate was highly dependent on the electrode composition but it was linear with applied voltage. The flow rate at 5 V for different nanocomposite, EPANI, EPANI‐A, EPANI‐B, and EPANI‐C were 127.29, 187.41, 148.51, and 95.47 µL/min cm², respectively, which increases substantially with increase in the Prussian blue content. The obtained best electro osmotic flux was 43 µL/min/V/cm² for EPANI‐A. It was higher than most of the EOP assembled using polyquinone and polyanthraquinone redox polymers. The assembled EOP remained exceptionally stable until the electrode charge capacity was fully utilized. The best EOP produces a maximum stall pressure of 1.2 kPa at 2 V. These characteristics make it suitable for a variety of microfluidic/device applications.     

Fluorescent protein barrel fluctuations and oxygen diffusion pathways in mCherry

Fluorescent proteins (FPs) are valuable tools as biochemical markers for studying cellular processes. Red fluorescent proteins (RFPs) are highly desirable for in vivo applications because they absorb and emit light in the red region of the spectrum where cellular autofluorescence is low. The naturally occurring fluorescent proteins with emission peaks in this region of the spectrum occur in dimeric or tetrameric forms. The development of mutant monomeric variants of RFPs has resulted in several novel FPs known as mFruits. Though oxygen is required for maturation of the chromophore, it is known that photobleaching of FPs is oxygen sensitive, and oxygen-free conditions result in improved photostabilities. Therefore, understanding oxygen diffusion pathways in FPs is important for both photostabilites and maturation of the chromophores. In this paper, we use molecular dynamics calculations to investigate the protein barrel fluctuations in mCherry, which is one of the most useful monomeric mFruit variant. We employ implicit ligand sampling to determine oxygen pathways from the bulk solvent into the mCherry chromophore in the interior of the protein. We also show that these pathways can be blocked or altered and barrel fluctuations can be reduced by strategic amino acid substitutions.     

Stereoselective synthesis of 3,4,5,6-tetrahydroxycyclohexyl β-amino acid derivatives

Stereoselective syntheses of racemic (1S,2R,3R,4R,5S,6R)- and (1S,2R,3R,4S,5S,6R)-3,4,5,6-tetrahydroxy derivatives of 2-aminocyclohexanecarboxylic acid have been achieved by a stereospecific Diels-Alder reaction between furan and maleic anhydride, a Curtius rearrangement and hydroxylation reactions.     

A cyclodextrin-based nanoassembly with bimodal photodynamic action

We have developed a supramolecular nanoassembly capable of inducing remarkable levels of cancer cell mortality through a bimodal action based on the simultaneous photogeneration of nitric oxide (NO) and singlet oxygen ((1)O(2)). This was achieved through the appropriate incorporation of an anionic porphyrin (as (1)O(2) photosensitizer) and of a tailored NO photodonor in different compartments of biocompatible nanoparticles based on cationic amphiphilic cyclodextrins. The combination of steady-state and time-resolved spectroscopic techniques showed the absence of significant intra- and interchromophoric interaction between the two photoactive centers embedded in the nanoparticles, with consequent preservation of their photodynamic properties. Photodelivery of NO and (1)O(2) from the nanoassembly on visible light excitation was unambiguously demonstrated by direct and real-time monitoring of these transient species through amperometric and time-resolved infrared luminescence measurements, respectively. The typical red fluorescence of the porphyrin units was essentially unaffected in the bichromophoric nanoassembly, allowing its localization in living cells. The convergence of the dual therapeutic action and the imaging capacities in one single structure makes this supramolecular architecture an appealing, multifunctional candidate for applications in biomedical research.     

Photoinduced Fluorescence Activation and Nitric Oxide Release with Biocompatible Polymer Nanoparticles

A viable strategy to encapsulate a fluorophore/photochrome dyad and a nitric oxide photodonor within supramolecular assemblies of a cyclodextrin‐based polymer in water was developed. The two photoresponsive guests do not interact with each other within their supramolecular container and can be operated in parallel under optical control. Specifically, the dyad permits the reversible switching of fluorescence on a microsecond timescale for hundreds of cycles, and the photodonor enables the irreversible release of nitric oxide. Furthermore, these supramolecular assemblies cross the membrane of human melanoma cancer cells and transport their cargo in the cytosol. The fluorescence of one component allows the visualization of the labeled cells, and its switchable character could, in principle, be used to acquire super‐resolution images, while the release of nitric oxide from the other induces significant cell mortality. Thus, our design logic for the construction of biocompatible nanoparticles with dual functionality might evolve into the realization of valuable photoresponsive probes for imaging and therapeutic applications.     

A Host–Guest Supramolecular Complex with Photoregulated Delivery of Nitric Oxide and Fluorescence Imaging Capacity in Cancer Cells

Herein we report the design, preparation, and properties of a supramolecular system based on a tailored nitric oxide (NO) photodonor and a rhodamine‐labeled β‐cyclodextrin conjugate. The combination of spectroscopic and photochemical experiments shows the absence of significant interchromophoric interactions between the host and the guest in the excited states. As a result, the complex is able to release NO under the exclusive control of visible light, as unambiguously demonstrated by direct detection of this transient species through an amperometric technique, and exhibits the typical red fluorescence of the rhodamine appendage. The supramolecular complex effectively internalizes in HeLa cancer cells as proven by fluorescence microscopy, shows a satisfactory biocompatibility in the dark, and induces about 50 % of cell mortality upon irradiation with visible light. The convergence of all these properties in one single complex makes the present host–guest ensemble an appealing candidate for further delevopment of photoactivatable nanoscaled systems addressed to photostimulated NO‐based therapy.