Synthesis and gelation property of amino acids-based dendronised oligomers

<div><p>The first- and second-generation dendrons constructed from alanine and aspartic acids were synthesised and further modified with a polymerisable acrylamide group at the focal point (MG1 and MG2). The corresponding dendronised oligomers were obtained by polymerisation, and then hydrolysed to afford them with multi-carboxyl groups on the periphery of branched side chains (PG1-COOH and PG2-COOH). The structures of the oligomers were characterised by ¹H NMR, Fourier transform infrared and gel permeation chromatograph, and their gelation behaviour was examined. It was found that PG1-COOH and PG2-COOH could form two-component gels, especially, PG1-COOH showed better gelation property. For example, it could gel with aliphatic primary or secondary amines in dimethylformamide and with melamine in acidic aqueous solution. Transmission electron microscopy and atomic force microscopy images showed that the gelators self-assembled into the fibrous networks.</p></div

Dendrimer-Based Demulsifiers for Polymer Flooding Oil-in-Water Emulsions

Two polyamidoamine-based dendritic molecules, named here as benzyl-G3 and octyl-G3, were synthesized using H₂NCH₂CH₂NRCH₂CH₂NH₂ (where R is either rigid benzyl or flexible octyl hydrophobic tails that are linked to the central nitrogen atom). With consideration of factors, such as the settling time, demulsifier dosage, temperature, oil content, and kinds of surfactants, the synthesized molecules were systematically investigated as demulsifiers for breaking up polymer flooding oil-in-water emulsions. In comparison to traditional G3 polyamidoamine, both benzyl-G3 and octyl-G3 exhibited better demulsification efficiencies with a dosage of 200 mg/L at a relatively low temperature (30 °C) in short periods of time (40 min) and reached 99.3 and 99.8% oil removal rates as they were added to the low oil-containing emulsion (1500 mg/L), respectively. A series of measurement methods were then adopted to explore the demulsification mechanism of the two demulsifiers. The interfacial tension and ζ potential measurements indicated that the high demulsification efficiency of the two dendrimers could be due to electrostatic charge neutralization. Moreover, the dendrimers and surfactants showed strong interactions according to the turbidity measurements, the results of which demonstrated that the hydrophobic tails located at the center of the dendrimers also influenced the demulsification efficiency

Association of vitamin B6 intake with the risk and prognosis of diabetic retinopathy: a NHANES-based study

Investigating the role of dietary vitamin B6 intake in the risk and prognosis of diabetic retinopathy (DR) could facilitate the management of DR. This study aimed to assess the association between dietary vitamin B6 intake and the risk of DR and further explore the association between vitamin B6 intake and mortality in patients with DR. This retrospective cohort study gained data from the National Health and Nutrition Examination Survey (NHANES) 2005–2006 and 2007–2008. The intake of dietary vitamin B6 was assessed by two 24-h dietary recall interviews. Mortality information in the National Death Index was recorded from the date of survey participation through 31 December 2019. Multivariate regression analyses were employed to assess the association between vitamin B6 intake and the risk of DR, and the association between vitamin B6 intake and the risk of mortality in patients with DR. A total of 5559 subjects were included, of which 693 (12.47%) had DR. Among these patients with DR, 429 (61.90%) were survivors. Multivariate analyses showed that the intake of vitamin B6 was negatively associated with the risk of DR (odds ratio = 0.81, 95% confidence level: 0.69–0.95, p = 0.012), and patients with DR with an increased intake of vitamin B6 had a significantly decreased risk of all-cause death (hazard ratio = 0.81, 95% confidence level: 0.66–0.99, p = 0.041) or cardiovascular disease-related death (hazard ratio = 0.76, 95% confidence level: 0.58–0.98, p = 0.037). The intake of vitamin B6 was negatively associated with the risk of DR, and in patients with DR, a higher intake of vitamin B6 was associated with a lower risk of all-cause death and cardiovascular disease-related death, indicating the possible protective role of increased vitamin B6 intake.</p

Green Synthesis, Surface Activity, Micellar Aggregation, and Foam Properties of Amide Quaternary Ammonium Surfactants

A series of amide quaternary ammonium surfactants with the formula CnH2n+1CONH(CH2)2N+(CH3)3·CH3CO3– (n = 9, 11, 13, 15) were synthesized using a fatty acid, N,N-dimethylethylenediamine, and a green reagent dimethyl carbonate. A comparative study of the four surfactants in terms of surface activity, aggregation characteristics, and foam properties was conducted. The results show that these amide quaternary ammonium surfactants reduce the surface tension of water to a minimum value of 23.69 mN·m–1 at a concentration of 1.55 × 10–4 mol·L–1 and self-assemble spontaneously into aggregates, which are mostly vesicles. Furthermore, with increasing the alkyl chain length, their critical micelle concentration (CMC) values and surface tension values at the CMC (γCMC) decrease and then increase, and the degree of counterion binding (β) decreases. It is also found that these amide quaternary ammonium surfactants exhibit excellent foam ability and foam stability

Photoresponsive Dendronized Copolymers of Styrene and Maleic Anhydride Pendant with Poly(amidoamine) Dendrons as Side Groups

A series of photoresponsive dendronized polymers <b>PG<i>n</i>-NB</b> (<i>n</i> = 1, 2, 3) were synthesized by attaching <i>o</i>-nitrobenzyl alcohol-terminated amidoamine dendrons (<b>G1</b>–<b>G3</b>) to the alternating styrene and maleic anhydride copolymer (PSt-<i>alt</i>-PMAh). The structures and the molecular weights of the obtained polymers were characterized by ¹H NMR and FTIR measurements. It is found that the coverage degrees of the dendrons are 74%, 42%, and 26%, respectively, indicating that the numbers of the appended dendrons decrease in the order of <b>G1</b> > <b>G2</b> > <b>G3</b> due to the steric hindrance of higher generation dendrons with more branches. The photocleavable behavior of <b>G1</b>–<b>G3</b> was detected by UV–vis and ¹H NMR measurements. As a result, <b>G2</b> showed a faster cleavage rate compared to <b>G1</b> and <b>G3</b>. The critical aggregation concentration (CAC) of <b>PG<i>n</i>-NB</b> (<i>n</i> = 1, 2, 3), measured by using pyrene as a fluorescence probe, were 0.05 mg/mL (<b>PG1-NB</b>), 0.01 mg/mL (<b>PG2-NB</b>), and 0.03 mg/mL (<b>PG3-NB</b>), which displayed that the structure of <b>PG2-NB</b> was in favor of forming aggregates at lower concentrations. Light scattering study indicated that both the apparent molecular weight and the chain density of the aggregates formed by <b>PG2-NB</b> decreased with the irradiation time. Atomic force microscope (AFM) measurements also showed that the size of the aggregates increased dramatically from 15 to 70 nm before and after UV irradiation, evidencing that the UV light induced structure change. Nile Reds, as the guest molecules, were loaded in the aggregates from <b>PG2-NB</b>, and the release profiles upon UV stimulus were monitored by the fluorescence spectroscopy

An Enzyme-Responsive Nanogel Carrier Based on PAMAM Dendrimers for Drug Delivery

G4 PAMAM dendrimer molecules were modified via covalently conjugating RGDC, RAADyC, and PEG chains on the periphery (<b>Mac-1</b>), by which a nanogel drug carrier with enzyme-sensitivity (<b>NG-1</b>) was constructed through an oxidation reaction by using NaIO₄ to initiate the chemical cross-link of the functional groups on the periphery of dendrimers. <b>Mac-1</b> and <b>NG-1</b> both had a spherelike shape with a relatively uniform size of 20 nm for <b>Mac-1</b> and 50 nm for <b>NG-1</b> as evidenced by TEM, SEM, and DLS measurements. <b>NG-1</b> showed much higher drug loading capacity as compared with that of <b>Mac-1</b> although the cavities in the dendritic structure were used to encapsulate drug molecules as reported in many literatures. In addition, the size of <b>NG-1</b> with embedded doxorubicin hydrochloride (DOX) decreased significantly to 15 nm in the presence of elastase, which indicated the decomposition of the nanogel triggered by enzyme, leading to drug release in a sustained manner <i>in vitro</i>. The <b>NG-1</b> carrier was noncytotoxic and biocompatible, and it achieved the same cytotoxicity as free DOX when the drug molecules were loaded inside. From confocal images, the penetrative process of DOX from nanogel could be clearly observed in 8 h. Such a dendrimer-based nanogel may be a potential nanocarrier for drug delivery in cancer therapy

A Single Crystal with Multiple Functions of Optical Waveguide, Aggregation-Induced Emission, and Mechanochromism

A novel single crystal, PyB, is produced in a high yield by the simple method of connecting a pyrene unit and a rhodamine B moiety together. PyB shows multiple functions of aggregation-induced emission, low-loss optical waveguiding, and tricolored mechanochromism. The crucial point for fabricating such a multifunctional single crystal is selecting the CN group as a spacer, which simplifies the synthetic procedure, confines the molecular conformation to develop single crystals, and allows one to dynamically observe the color variation in situ and quantitatively analyze the effect of applied pressures. Such a simple approach may be extended to other fluorophores, thus providing a new opportunity for the real world application of mechanochromic materials for mechanical sensors, optical encoding, and optoelectronic devices, etc