[Preparation of a block copolymer-based temperature-responsive affinity chromatography stationary phase for antibody separation and purification].

Antibodies play an essential role in cancer diagnosis and treatment because of the specificity for target biomolecules and reduction of side effects. However, antibodies separation and purification still face some challenges. Antibody elution from columns using a low-pH aqueous solution leads to aggregation or loss of activity of the antibody drugs. In this paper, a block copolymer-based temperature-responsive affinity chromatography (TRAC) stationary phase, SiO2-P[NIPAM-b-4VP]-MEP using the block temperature-responsive copolymer poly(N-isopropylacrylamide-b-4-vinylpyridine) (P[NIPAM-b-4VP]) as the space arms and 4-mercaptoethyl pyridine (MEP) as the ligand was prepared for antibody separation. The TRAC column was tested using bovine serum albumin (BSA) and γ-globulin as model proteins, and the effects of salt concentration in the mobile phase and temperature on their separation were studied in detail. At 40 ℃, the TRAC stationary phase only selectively retained γ-globulin due to the specific affinity interaction between antibodies and the ligand MEP. At 5 ℃, γ-globulin can be eluted from the column with a mass recovery of 92.7% using a Tris-HCl buffer (pH 8.0) solution containing 0.6 mol/L NaCl. The adsorption capacity of γ-globulin on this stationary phase was (71.5 ±2.1) mg/g (n=3), which was twice that of a traditional temperature-sensitive affinity chromatography stationary phase SiO2-PNIPAM-MEP. The stationary phase was also used to separate and purify immunoglobulin (IgG) in human serum in one step by altering the temperature and ion strength of the mobile phase, resulting in a purity of 97.4%±0.7%. Thus, this new technology has specific selectivity for antibodies, as well as mild and green elution conditions, ultimately resolving the problem of traditional affinity chromatography using acid elution, which can lead to the antibodies aggregation/inactivation. This technology has great application potential for the industrial production of antibody drugs.

Chalcogen and Pnictogen Bonding-Modulated Multiple-Constituent Chiral Self-Assemblies.

Chalcogen and pnictogen-based σ-hole interactions have shown limited applications in controlling supramolecular chirality. In this work, we employed chalcogen and pnictogen bonding to control supramolecular chirality in a multiple-constituent system with modulate chiral optics. Phenyl phosphonium-selenium conjugates with electrophilic σ-hole regions were allowed to coassemble with the π-conjugated deprotonated amino acids. Control experimental and computational results evidenced that the chalcogen and pnictogen bonding formed with carboxylates induced morphological transformation from achiral membranes to chiral helical nanotubes with emerging supramolecular chirality. Also, the chiral helical architectures accomplished inverted handedness and chiroptical activities, including circular dichroism and circularly polarized luminescence. Finally, synergistic chalcogen and pnictogen bonding was employed to stabilize the charge-transfer complexation to afford ternary chiral co-assemblies with evolved chiral optics and luminescence. This work, showing the role of chalcogen and pnictogen bonding in manipulating supramolecular chirality and optics, will expand the toolbox in the fabrication and property-tuning of chiral materials containing elements of Group VA and VIA.

Moving Beyond Lewis: Employment and Wage Trends in China's High- and Low-Skilled Industries and the Emergence of an Era of Polarization: Presidential Address for the 2020 Association for Comparative Economic Studies Meetings.

One of the defining features of China's economy over the two decades between 1995 and 2015 was the persistent rise of wages for workers and professionals in nearly every segment of the economy-with wage rates for labor-intensive jobs in manufacturing, construction, and the informal service sector rising the fastest. Recently, however, the economic environment in China has begun to change, including changes in both employment and wages. We identify recent employment/wage trends throughout China's economy and postulate the sources of these trends as well as possible future consequences if they continue. We use official, nationally aggregated data to examine employment and wages in multiple sectors and industries. Our findings indicate that China may have entered a new phase of economic development in the mid-2010s. According to the data, in recent years, wage growth has begun to polarize: Rising for professionals employed in formal skill-intensive industries; and falling for workers in the informal labor-intensive service sector. We attribute this increase in skill-intensive wages to an increase in demand for skill-intensive employment, due to the emergence of a large middle class in China, for whom the demand for high technology, finance, banking, health, and higher education industries is increasing while, at least in the recent short term, the supply of experienced, high-skilled professionals has not kept up. The employment/wage trend in the informal (low-wage) service sector, however, is following a different pattern. While there is a rising demand for services in China's economy, the growth, due to a number of factors (e.g., large shares of GDP targeted by policymakers to investment; high rates of savings by consumers), is relatively slow. In contrast, due to a number of economic forces, including globalization and automation, the supply of labor into the service sector of the informal economy is being fueled by the flow of labor out of manufacturing and construction (two industries that that have experienced employment declines since 2013). These supply and demand trends, in turn, are leading to the fall in the growth rate of wages in the informal service sector. We conclude by discussing the possible longer-term consequences of these emerging polarization trends based on an examination of recent experience with wage polarization occurring in both middle- and high-income countries, as well as its consequences. We also present policy recommendations for greater investment in education and human capital, as well as for the development of a more comprehensive set of social safety nets for different segments of China's population.

Synthesis of a novel biomedical poly(ester urethane) based on aliphatic uniform-size diisocyanate and the blood compatibility of PEG-grafted surfaces.

The purpose of this study is to offer a novel kind of polyurethane with improved surface blood compatibility for long-term implant biomaterials. In this work, the aliphatic poly(ester-urethane) (PEU) with uniform-size hard segments was prepared and the PEU surface was grafted with hydrophilic poly(ethylene glycol) (PEG). The PEU was obtained by chain-extension of poly(ɛ-caprolactone) (PCL) with isocyanate-terminated urethane triblock. Free amino groups were introduced onto the surface of PEU film via aminolysis with hexamethylenediamine, and then the NH2-grafted PEU surfaces (PEU-NH2) were reacted with isocyanate-terminated monomethoxyl PEG (MPEG-NCO) to obtain the PEG-grafted PEU surfaces (PEU-PEG). Analysis by nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, and gel permeation chromatography were performed to confirm the chemical structures of the chain extender, PCL, PEU, and PEU-PEG. Additionally, the influence of aminolysis on the physical-mechanical properties of PEU films was investigated. Two glass transition temperatures and a broad endothermic peak were observed in the differential scanning calorimetry curves of PEU, which demonstrated a microphase-separated and semicrystalline structure, respectively. The PEU-PEG film exhibited excellent mechanical properties with an ultimate stress of ∼39 MPa and an elongation at break of ∼1190%, which was slightly lower than that of PEU, indicating that the aminolysis has little influence on the tensile properties. Evaluation of the blood compatibility of the films by bovine serum albumin adsorption and the platelet adhesion test revealed that the PEG-grafted surface had improved resistance to protein adsorption and excellent resistance to platelet adhesion. In vitro degradation tests showed that the PEU-PEG film could maintain its mechanical properties for more than six months and only lost ∼25% weight after 18 months. Due to the excellent mechanical properties, good blood compatibility and slow degradability, this novel kind of polyurethane hold significant promise for long-term implant biomaterials, especially soft tissue augmentation and regeneration.

Preparation and properties of biomedical segmented polyurethanes based on poly(ether ester) and uniform-size diurethane diisocyanates.

This study describes the preparation and properties of a novel aliphatic cost-effective segmented polyurethanes (SPUs) based on poly(ether ester) (poly-(ε-caprolactone-co-l-lactide)-poly(ethylene glycol)-poly-(ε-caprolactone-co-l-lactide), PECLA) and uniform-size diurethane diisocyanates (HDI-BDO-HDI). PECLA was synthesized via bulk ring-opening polymerization with poly(ethylene glycol) (PEG) as an initiator and ε-caprolactone, l-lactide as monomers. By chain extension of PECLA diol with HDI-BDO-HDI, three SPUs with different hydrophilic segments content and hard segments content were obtained. The chemical structures of the chain extender, PECLA and SPUs were confirmed by 1H NMR, 13C NMR, FT-IR, HR-TOF-MS and GPC. The influences of PEG content and uniform-size hard segments on in vitro degradability and mechanical properties of SPU films were researched. Similar thermostability observed in TGA curves of SPU films indicated that the hard segments and PEG content had little influence on the thermostability. The formation of microsphase-separated morphologies, which were demonstrated by the results of DSC and XRD, and physical-linking (H-bonds) network structures led to better mechanical properties of SPU films (ultimate stress: 23.1-17.9 MPa; elongation at break: 840-1130%). The results of water absorption and water contact angle showed that the bulk and surface hydrophilicity were closely related with the hydrophilic PEG content in SPU backbone. And the water absorption being less than 10 wt% indicated that the SPU films had low swelling property. In vitro hydrolytic degradation studies showed that the time of the SPU films becoming fragments was 34-19 days and the degradation rate increased with the increasing content of hydrophilic segments in SPUs, indicating that the degradation rate of SPU films could be controlled by adjusting PEG content. Cytotoxicity test of film extracts were conducted using L929 cells, and the relative growth rate exceeded 90% after incubation for 24, 48 and 72 h, showing excellent cytocompatibility. The acceptable mechanical properties, controllable biodegradability and excellent cytocompatibility of the polyurethanes can make them good candidates for further biomedical applications.

A new method for evaluating the dissolution of orodispersible films.

The aim of this research was to develop and assess a new dissolution apparatus for orodispersible films (ODFs). The new apparatus was based on a flow-through cell design which requires only a limited amount of dissolution medium and can automatically collect samples in short-time intervals. Compared with the dissolution method in Chinese Pharmacopeia, our method simulated the flow condition of the oral cavity and resulted in reproducible dissolution data and remarkably discriminating capability. Therefore, we concluded that the proposed dissolution method was particularly suitable for evaluating the dissolution of ODFs and should also be applicable to other fast-dissolving solid dosage forms.