Ionic surfactants as assembly crosslinkers triggered supramolecular membrane with 2D↔3D conversion under multiple stimulus

HYPOTHESIS

General strategies leading to 2D assemblies promise a significant step forward in the development of supramolecular materials with diversity and superiority. Considering molecular packing parameter indicates a connection between molecular geometry and aggregate morphology, we predict the introduction of ionic surfactants as assembly crosslinker would be endowed to develop a methodology of 2D supramolecular assembles.

EXPERIMENTS

In this work, by introducing ionic surfactants such as sodium dodecylsulfate (SDS), the molecular packing parameter P in bolaamphiphile (A2G) system was increased, which successfully manipulated the transformation of the 3D vesicles into 2D membranes. This 2D membranes further showed excellent light and enzyme response, and thus 2D to 3D morphological conversion can be rationally controlled via UV/Vis light irradiation and alternate addition of β-CD and α-amylase. Significantly, the 2D feature revealed not only a remarkable fluorescence enhancement to luminescent molecules but also the ability to effectively remove pollutants from water through filtration.

FINDINGS

We report a general and facile strategy for the construction of 2D supramolecular membranes, initiated by introducing ionic surfactants as assembly crosslinker to increase P. In the existence of stimulus response factors, 2D↔3D morphological conversion can be further controlled in a flexible manner, which opens up a new paradigm leading to interconvertible supramolecular materials.

Synthesis and Evaluation of Chirally Defined Side Chain Variants of 7-Chloro-4-Aminoquinoline To Overcome Drug Resistance in Malaria Chemotherapy

A novel 4-aminoquinoline derivative [(S)-7-chloro-N-(4-methyl-1-(4-methylpiperazin-1-yl)pentan-2-yl)-quinolin-4-amine triphosphate] exhibiting curative activity against chloroquine-resistant malaria parasites has been identified for preclinical development as a blood schizonticidal agent. The lead molecule selected after detailed structure-activity relationship (SAR) studies has good solid-state properties and promising activity against in vitro and in vivo experimental malaria models. The in vitro absorption, distribution, metabolism, and excretion (ADME) parameters indicate a favorable drug-like profile.

Surface-Initiated Controlled Radical Polymerization: State-of-the-Art, Opportunities, and Challenges in Surface and Interface Engineering with Polymer Brushes

The generation of polymer brushes by surface-initiated controlled radical polymerization (SI-CRP) techniques has become a powerful approach to tailor the chemical and physical properties of interfaces and has given rise to great advances in surface and interface engineering. Polymer brushes are defined as thin polymer films in which the individual polymer chains are tethered by one chain end to a solid interface. Significant advances have been made over the past years in the field of polymer brushes. This includes novel developments in SI-CRP, as well as the emergence of novel applications such as catalysis, electronics, nanomaterial synthesis and biosensing. Additionally, polymer brushes prepared via SI-CRP have been utilized to modify the surface of novel substrates such as natural fibers, polymer nanofibers, mesoporous materials, graphene, viruses and protein nanoparticles. The last years have also seen exciting advances in the chemical and physical characterization of polymer brushes, as well as an ever increasing set of computational and simulation tools that allow understanding and predictions of these surface-grafted polymer architectures. The aim of this contribution is to provide a comprehensive review that critically assesses recent advances in the field and highlights the opportunities and challenges for future work.

Preparation of a silica stationary phase co-functionalized with Wulff-type phenylboronate and C12 for mixed-mode liquid chromatography

A silica stationary phase was designed and synthesized through the co-functionalization of silica with Wulff-type phenylboronate and C12 for mixed-mode liquid chromatography applications. The as-synthesized stationary phase was characterized by elemental analysis and Fourier Transform-InfraRed Spectroscopy (FT-IR). Retention mechanisms, including boronate affinity (BA), reversed-phase (RP) and anion-exchange (AE), were involved. Retention mechanism switching was easily realized by adjustment of the mobile phase constitution. Cis-diol compounds could be selectively captured under neutral conditions in BA mode and off-line separated in RP mode. Neutral, basic, acidic and amphiprotic compounds were chromatographed on the column in RP chromatography, while inorganic anions were chromatographed in AE chromatography to characterize the mixed-mode nature of the prepared stationary phase. In addition, the RP performance was compared with an octadecyl silica column in terms of column efficiency (N/m), asymmetry factor (A_f), retention factor (k) and resolution (Rs). The prepared stationary phase offered multiple interactions with analytes in addition to hydrophobic interactions under RP elution conditions. Based on the mixed-mode properties, off-line 2D-LC, for selective capture and separation of urinary nucleosides, was successfully realized on a single column, demonstrating its powerful application potential for complex samples.

Nanofibers of hydrogen-bonded two-component gel with closely connected p- and n-channels and photoinduced electron transfer

An D-A-D gelator (DTCQ) was designed and synthesized using 2,3-dimethyl-5,8-di(thiophen-2-yl)quinoxaline and N-alkyl 3-aminocarbazole units as acceptor and donor, respectively, which were linked by a single bond. The compound could gelate several solvents, such as benzyl alcohol, aniline, acetophenone, and o-dichlorobenzene, as well as self-assemble into one-dimensional (1D) nanofibers in gel phase. The absorption and infrared spectra of the gels indicated that π-π interactions between aromatic moieties, intermolecular hydrogen bonds between amide units, and van der Waals forces were the driving forces for the formation of 1D self-assemblies and gel. DTCQ gel was red and emits red fluorescence because it has a strong absorption band at 487 nm and an emissive band at 620 nm. Moreover, DTCQ and a fullerene carboxylic acid formed two-component gel, in which the two compounds developed a hydrogen bond complex and self-assembled into 1D nanofibers with closely connected p- and n-channels. The nanofibrous xerogel film can rapidly generate a photocurrent under visible-light radiation through electron transfer from the gelator to fullerene, and then, the excellent exciton separation and charge transfer to two electrodes.

Amplifying emission enhancement and proton response in a two-component gel

A glutamide gelator, 1, was synthesized, and a weak emission enhancement was observed during its gelation. In addition, 1 could be an excellent scaffold for successfully embedding an energy acceptor, 2, into its aggregate to obtain highly efficient energy transfer. An amplification of the emission enhancement was observed in the two-component gels compared to that of the neat gel of 1 during gel formation. For example, 1 induced only a 2.5-fold increase in emission intensity, whereas a 23-fold enhanced emission could be observed in the two-component gel with only 1.6 mol % 2. Furthermore, two-component gels had an excited proton response. In systems with low acceptor concentrations, the hot solution red-shifted the fluorescence from blue to yellow upon the addition of a proton, which continuously blue-shifted with decreasing temperature to form the gel given that the binding of the gelator to the proton is weakened during coassembly. Moreover, the casting film formed by the two-component wet gel had an excellent response to volatile acids such as hydrochloric acid, trifluoroacetic acid, and so on and could be reversibly recovered by exposure to NH(3).

Silica nanoparticles functionalized via click chemistry and ATRP for enrichment of Pb(II) ion

Silica nanoparticles have been functionalized by click chemistry and atom transfer radical polymerization (ATRP) simultaneously. First, the silanized silica nanoparticles were modified with bromine end group, and then the azide group was grafted onto the surface via covalent coupling. 3-Bromopropyl propiolate was synthesized, and then the synthesized materials were used to react with azide-modified silica nanoparticles via copper-mediated click chemistry and bromine surface-initiated ATRP. Transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis were performed to characterize the functionalized silica nanoparticles. We investigated the enrichment efficiency of bare silica and poly(ethylene glycol) methacrylate (PEGMA)-functionalized silica nanoparticles in Pb(II) aqueous solution. The results demonstrated that PEGMA-functionalized silica nanoparticles can enrich Pb(II) more quickly than pristine silica nanoparticles within 1 h.

Preparation of imidazole-functionalized silica by surface-initiated atom transfer radical polymerization and its application for hydrophilic interaction chromatography

A novel imidazole-functionalized stationary phase for hydrophilic interaction chromatography (HILIC) was prepared via surface-initiated atom transfer radical polymerization (SI-ATRP). 1-Vinylimidazole as a monomer was polymerized on the surface of initiator-immobilized silica by SI-ATRP using CuCl and 2,2'-bipyridyl as a catalyst. The graft chain length and polymer grafting density were controlled by varying the ratio of monomer to initiator. The resulting materials were characterized by elemental analysis and thermogravimetric analysis. Then, high-performance liquid chromatography separation of eight nucleobases/nucleosides was performed on the imidazole-functionalized chromatographic column in HILIC mode. The effects of mobile phase composition, buffer pH, and column temperature on the separation of nucleobases/nucleosides were investigated, and the retention mechanisms were studied. Chromatographic parameters were calculated, and the results showed that surface adsorption through hydrogen bonding and electrostatic interaction dominated the retention behavior of the solutes in HILIC mode. Lastly, the stationary phase was successfully used to determine the nucleobases and nucleosides from Cordyceps militaris.

Design, Synthesis, and Antitumor Activity of 4-Halocolchicines and Their Pro-drugs Activated by Cathepsin B

Novel colchicine derivatives possessing various substituents at the C4 position were prepared. Among them, 4-halo derivatives 3-6 were found to exhibit higher activity against cancer cell lines (A549, HT29, HCT116) as well as on mice transplanted with the HCT116 human colorectal carcinoma cell line than colchicine (1). Further, utilizing the 4-substituted colchicines, we prepared pro-drugs having a dipeptide side chain and demonstrated that these pro-drugs were activated by cathepsin B, an enzyme overexpressed in tumor cells, and exhibited selective toxicity to the tumor cells.

Pharmaceutical organogels prepared from aromatic amino acid derivatives

Organogels are semi-solid systems in which an organic liquid phase is immobilized by a 3-dimensional network composed of self-assembled gelator molecules. Although there is a large variety of organogel systems, relatively few have been investigated in the field of drug delivery, owing mostly to the lack of information on their biocompatibility and toxicity. In this work, organogelator-biocompatible structures based on aromatic amino acids, namely, tyrosine, tryptophan, and phenylalanine were synthesized by derivatization with aliphatic chains. Their ability to gel an injectable vegetable oil (i.e. safflower oil) and to sustain the release of a model anti-Alzheimer drug (i.e. rivastigmine) was then evaluated. Organogels and molecular packing were characterized by differential scanning calorimetry, rheology analysis, Fourier-transform infrared spectroscopy and X-ray crystallography. The amino acid derivatives were able to gel safflower oil through van der Waals interactions and H-bonds. Tyrosine-derivatives produced the strongest gels while tryptophan was associated with poor gelling properties. The superior gelling ability of tyrosine derivatives could be explained by their well-structured 2-dimensional packing in the network. The addition of an optimal N-methyl-2-pyrrolidone amount to tyrosine gels fluidized the network and allowed their injection through conventional needles. Upon contact with an aqueous medium, the gels formed in situ and released entrapped rivastigmine in a sustained fashion.

Evaluation of selectivity for L-glutamide-derived highly ordered assemblies in reversed-phase high-performance liquid chromatography

Two dioctadecyl L-glutamic acid derivatives with amide and ester type bondings have been synthesized and immobilized from 3-aminopropyltrimethoxysilane (APS) grafted silica (Sil-APS) to be used in reversed-phase high-performance liquid chromatography (RP-HPLC). Subsequent studies showed that dioctadecyl-L-glutamide derivative (GLN) can self-assemble into highly ordered structures by forming three-dimensional fibrillar aggregates as observed in scanning and transmission electron microscopes (SEM and TEM). Variable temperature (1)H NMR and FT-IR spectra of organogel revealed that the special aggregation morphology shown by GLN was stabilized by inter and or intra molecular hydrogen bonding among amide moieties. However, such ordered aggregated or self-assembled structures were not observed for the dioctadecyl-L-glutamate (GLU) derivative. The stationary phases Sil-GLN and Sil-GLU were characterized by DRIFT, elemental analysis, TGA, and (13)C and (29)Si CP-MAS NMR spectroscopic measurements. The chromatographic selectivity for both stationary phases was evaluated from the retention studies of different size and shape polycyclic aromatic hydrocarbons (PAHs). The chromatographic experiment for PAHs and geometrical isomers in RP-HPLC showed that Sil-GLN demonstrated extremely enhanced selectivity than Sil-GLU. The higher selectivity attributed by Sil-GLN has been brought by multiple pi-pi interactions among the pi-electrons of the grafted organic phase and pi-electrons of the guest PAHs molecules. Thermodynamic studies for linear and nonlinear PAHs revealed that the retention behavior does not change over a temperature range from 10 to 60 degrees C for both stationary phases.