China Women's University

About: China Women's University is a education organization based out in Beijing, China. It is known for research contribution in the topics: China & Tourism. The organization has 145 authors who have published 146 publications receiving 1626 citations.

Breathing polymersomes: CO2-tuning membrane permeability for size-selective release, separation, and reaction.

Abstract: Selective substance channels and confined reaction spaces that span scales ranging from the macroscopic world down to nanometer-sized structures are abundant in biological systems. A basic entity is a cell, the membrane of which offers a confining boundary to control substance exchange and to compartmentalize complex biochemical processes. To comprehend the selective permeation mechanism of lipid membranes and to imitate their working principles, biomimetic cellular models have been explored. Several artificial liposome systems with membrane selectivity have been successfully developed. Within the last few years, a polymer-based equivalent, the polymersome, has come to be regarded as a promising candidate for such a system. By tailoring the polymer structure and altering the polymer composition, one can endow these polymersomes with tunable permeability. For example, Meier et al. studied the use of channel proteins and block copolymer bioconjugated membranes to selectively filter guest molecules. Recently, an effective method based on the self-assembly of stimuli-responsive block copolymers was used to build intelligent vesicles. This approach allows the bilayer gates to turn on and off when an external stimulus is given. Herein, to enrich the scope of responsive polymersomes and improve polymeric membrane selectivity, we propose a new method to tune the permeability of polymersome membranes by means of carbon-dioxide-responsive copolymers. Utilizing CO2 levels to control the size of nanopores in the membrane, these nanocontainers can attain the goal of releasing and separating globular nanoparticles of different sizes. Furthermore, they have the potential to act as nanoreactors that can insulate different catalytic reactions with the aid of CO2-regulated transmembrane traffic. We have synthesized a series of amphiphilic block copolymers, consisting of biocompatible and nonimmunogenic poly(ethylene glycol) (PEG) for the hydrophilic portion, and CO2-sensitive poly(N-amidino)dodecyl acrylamide (PAD) as the hydrophobic portion. The target diblock copolymers, PEG-b-PAD, were prepared by atom transfer radical polymerization (Scheme 1a). Owing to their amphiphilicity, the copolymers can self-assemble into vesicular nanostructures in aqueous solution, and, most importantly, the polymersomes can continuously self-expand in a CO2 atmosphere. Once vesicular shape changes, the membrane structure and permeability must alter. On the basis of this concept, we wondered if we could make use of CO2 as a stimulus to tune polymersome membrane permeability over a broad range. We first tested the self-assembly behavior of the PEG-bPAD in aqueous solution. The critical aggregation concentration (CAC) is ca. 0.12 mgmL 1 (Supporting Information, Figure S3). Transmission electron microscopy (TEM) showed that the average size of the initial vesicles was (112 6.0) nm, which is consistent with the hydrodynamic radius (Rh) of 59.8 nm determined by dynamic light scattering (DLS; Figure 1a and d) analysis. As expected, these vesicles started to expand when CO2 passed through the solution at a rate of 1.0 mLmin . As shown in Figure 1b, much larger intact vesicles with diameters of (151 28) nm were found after 10 min of CO2 treatment. Under these conditions, the Rh of these aggregates increased to 83.5 nm, which corresponds to the TEM results. When the CO2 aeration time was prolonged to 30 min, the polymersomes finally extended to a maximum diameter of (238 26) nm (Figure 1c), which is close to the value of 137.2 nm determined by DLS analysis. The change in vesicle size is proportional to the gas stimulation time, and their radii grow at a constant rate of ca. 2.5 nmmin 1 Scheme 1. a) Gas-switchable chemical structural change of the PEG-bPAD block copolymer. b) The self-assembly of the copolymer into polymersomes and reversible gas-controlled breathing behavior in aqueous media.

Food-related hazards in China : consumers' perceptions of risk and trust in information sources

Abstract: This paper identifies segments of Chinese consumers based on their perception of personal risk, how worried they are and their subjective knowledge about seven possible food-related hazards: additives, residues, counterfeit, inferior, genetically modified, deteriorated and nutritionally imbalanced food. Data were collected through a consumer survey conducted in Beijing (534 participants) and in Baoding (437 participants). Three clusters were identified: worried and knowledgeable consumers (60.1%), worried and ignorant consumers (21.7%) and moderately worried consumers (18.2%). The first two groups reported a high level of worry and high perception of personal risk about food-related hazards in China. The two hazards they were most worried about were counterfeit food and inferior quality food. Television, internet and personal communication were the three information channels most frequently used by participants to obtain information about food safety. Worried and ignorant consumers reported less frequent use of magazines, books and brochures compared with other consumers. Medical doctors, personal experience and research institutes were the three most trusted information sources for the first two groups of consumers. Moderately worried consumers only placed high levels of trust in medical doctors and themselves. Consumers' perceptions about the knowledge, honesty and concern of different information sources significantly and positively affected their trust in those sources. The study concludes by making recommendations as to how to improve communications with the different identified consumer segments and identifies future research required to expand its validity.