Fluorinated dendritic amphiphiles, their stomatosome aggregates and application in enzyme encapsulation

Enzymes are more selective and efficient than synthetic catalysts but are limited by difficult recycling. This is overcome by immobilisation, namely through encapsulation, with the main drawback of this method being slow diffusion of products and reactants, resulting in effectively lowered enzyme activity. Fluorinated dendritic amphiphiles were reported to self-assemble into regularly perforated bilayer vesicles, so-called "stomatosomes". It was proposed that they could be promising novel reaction vessels due to their increased porosity while retaining larger biomolecules at the same time. Amphiphiles were synthesised and their aggregation was analysed by cryogenic transmission electron microscopy (cryo-TEM) and dynamic light scattering (DLS) in buffered conditions necessary for enzyme encapsulation. Urease and albumin were encapsulated using the thin-film hydration method and investigated by confocal and time-gated stimulated emission depletion microscopy (gSTED). Their release was then used to probe the selective retention of cargo by stomatosomes. Free and encapsulated enzyme activity were compared and their capacity to be reused was evaluated using the Berthelot method. Urease was successfully encapsulated, did not leak out at room temperature, and showed better activity in perforated vesicles than in closed vesicles without perforations. Encapsulated enzyme could be reused with retained activity over 8 cycles using centrifugation, while free enzyme had to be filtrated. These results show that stomatosomes may be used in enzyme immobilisation applications and present advantages over closed vesicles or free enzyme.

Polyethers Based on Short-Chain Alkyl Glycidyl Ethers: Thermoresponsive and Highly Biocompatible Materials

The polymerization of short-chain alkyl glycidyl ethers (SCAGEs) enables the synthesis of biocompatible polyethers with finely tunable hydrophilicity. Aliphatic polyethers, most prominently poly(ethylene glycol) (PEG), are utilized in manifold biomedical applications due to their excellent biocompatibility and aqueous solubility. By incorporation of short hydrophobic side-chains at linear polyglycerol, control of aqueous solubility and the respective lower critical solution temperature (LCST) in aqueous solution is feasible. Concurrently, the chemically inert character in analogy to PEG is maintained, as no further functional groups are introduced at the polyether structure. Adjustment of the hydrophilicity and the thermoresponsive behavior of the resulting poly(glycidyl ether)s in a broad temperature range is achieved either by the combination of the different SCAGEs or with PEG as a hydrophilic block. Homopolymers of methyl and ethyl glycidyl ether (PGME, PEGE) are soluble in aqueous solution at room temperature. In contrast, n-propyl glycidyl ether and iso-propyl glycidyl ether lead to hydrophobic polyethers. The use of a variety of ring-opening polymerization techniques allows for controlled polymerization, while simultaneously determining the resulting microstructures. Atactic as well as isotactic polymers are accessible by utilization of the respective racemic or enantiomerically pure monomers. Polymer architectures varying from statistical copolymers, di- and triblock structures to star-shaped architectures, in combination with PEG, have been applied in various thermoresponsive hydrogel formulations or polymeric surface coatings for cell sheet engineering. Materials responding to stimuli are of increasing importance for "smart" biomedical systems, making thermoresponsive polyethers with short-alkyl ether side chains promising candidates for future biomaterials.

Supramolecular Engineering of Alkylated, Fluorinated, and Mixed Amphiphiles

The rational design of perfluorinated amphiphiles to control the supramolecular aggregation in aqueous medium is still a key challenge for the engineering of supramolecular architectures. Here we present the synthesis and physical properties of six novel non-ionic amphiphiles. We also studied the effect of mixed alkylated and perfluorinated segments in a single amphiphile and compared it with only alkylated and perfluorinated units. To explore their morphological behavior in aqueous medium, we used dynamic light scattering (DLS) and cryo-TEM/EM measurements. We further confirmed their assembly mechanisms with theoretical investigations, using the Martini model to perform large-scale coarse-grained molecular dynamics simulations. These novel synthesized amphiphiles offer a greater and more systematic understanding of how perfluorinated systems assemble in aqueous medium and suggest new directions for rational designing of new amphiphilic systems and interpreting their assembly process. This article is protected by copyright. All rights reserved.

Stimuli-responsive non-ionic Gemini amphiphiles for drug delivery applications

This paper shows the synthesis of stimuli responsive Gemini amphiphiles sensitive to Glutathione and hydrolase.

Mechanism of the formation of microphase separated water clusters in a water-mediated physical network of perfluoropolyether tetraol

Perfluoropolyether tetraol (PFPE tetraol) possesses a hydrophobic perfluoropolyether chain in the backbone and two hydroxyl groups at each chain terminal, which facilitates the formation of hydrogen bonds with water molecules resulting in the formation an extended physical network. About 3 wt% water was required for the formation of the microphase separated physical network of PFPE tetraol. The mechanism responsible for the microphase separation of water clusters in the physical network was studied using a combination of techniques such as NMR spectroscopy, molecular dynamics (MD) simulations and DSC. MD simulation studies provided evidence for the formation of clusters in the PFPE tetraol physical network and the size of these clusters increased gradually with an increase in the extent of hydration. Both MD simulations and NMR spectroscopy studies revealed that these clusters position themselves away from the hydrophobic backbone or vice versa. The presence of intra- and inter-chain aggregation possibility among hydrophilic groups was evident. DSC results demonstrated the presence of tightly and loosely bound water molecules to the terminal hydroxyl groups of PFPE tetraol through hydrogen bonding. The data from all the three techniques established the formation of a physical network driven by hydrogen bonding between the hydrophilic end groups of PFPE tetraol and water molecules. The flexible nature of the PFPE tetraol backbone and its low solubility parameter favour clustering of water molecules at the terminal groups and result in the formation of a gel.

(E)-2,6-Di-bromo-4-{2-[1-(1H,1H,2H,2H-perfluoro-oct-yl)pyridinium-4-yl]ethen-yl}phenolate methanol disolvate, a fluoro-ponytailed solvatochromic dye

The title compound, C21H12Br2F13NO·2CH3OH, was obtained by condensation of 4-methyl-1-(1H,1H,2H,2H-perfluoro-oct-yl)pyridinium iodide and 3,5-di-bromo-4-hy-droxy-benzaldehyde, followed by deprotonation. It crystallizes as a methanol disolvate and exhibits short O-H⋯O hydrogen bonds and a disordered perfluoro-alkyl chain [occupancy ratio 0.538 (7):0.462 (7)]. Significant π-π stacking inter-actions are observed between the benzene and pyridine rings of neighbouring mol-ecules along the b-axis direction.