A case study of distribution and characteristics of microplastics in surface water and sediments of the seas around Shenzhen, southern coastal area of China.

Microplastics (MPs), known to cause environmental pollution, is attracting a growing attention worldwide owing to their extensive existence and potential risks to biota. The marginal sea areas are suspected to be especially susceptible to MPs pollution. Unfortunately, data on MPs in the surface water and sediments ecosystems are still limited, particularly in the southern coastal areas of China. The study was successfully utilized to explore the distribution and characteristics of MPs below 5 mm collected from 14 sites in the seas around Shenzhen, a typical special economic zone of China. MPs were detected in both surface water and sediments with concentrations ranging from 3.8 to 7.8 items per liter and 2.6 × 103 to 10.0 × 103 items per kilogram, respectively. The highest abundance of MPs appeared in S5/S9 and S14 in surface water and sediments, respectively. Fiber and film with small particle size (<0.5 mm) were identified as typical and abundant MPs type among all samples. In addition, polyethylene (PE) was considered as dominant forms of MPs in surface water and sediment samples. Results from this study indicated a positive correlation with abundance of MPs and urbanization rate, which also showed an evident difference of MPs in different urban functional areas. Based on the types and quantity of detected MPs, we assessed the risk of MPs pollution in this study area, and the ecological risk category of MPs was at a high level. Importantly, our work might be employed as a potential information so as to better understand MPs pollution, source tracing and ecological risk assessment, which enhances the possibility of achieving effective control and supervision of MPs pollution in southern coastal aera of China.

Dual Enzyme-Like Performances of PLGA Grafted Maghemite Nanocrystals and Their Synergistic Chemo/Chemodynamic Treatment for Human Lung Adenocarcinoma A549 Cells.

In recent years, the emergence of non-toxic but catalytically active inorganic nanoparticles has attracted great attention for cancer treatment, but the therapeutic effect has been affected by the limited reactive oxygen species in tumors. Therefore, the combination of chemotherapy and chemodynamic therapy is regarded as a promising therapeutic strategy. In this paper, we reported the preparation and bioactivity evaluation of poly(lactic acid-co-glycolic acid) (PLGA) grafted-γ-Fe2O3 nanoparticles with dual response of endogenous peroxidase and catalase like activities. Our hypothesis is that PLGAgrafted γ-Fe2O3 nanoparticles could be used as a drug delivery system for the anti-tumor drug doxorubicin to inhibit the growth of lung adenocarcinoma A549 cells; meanwhile, based on its mimic enzyme properties, this kind of nanoparticles could be combined with doxorubicin in the treatment of A549 cells. Our experimental results showed that the PLGAgrafted γ-Fe2O3 nanoparticles could simulate the activity of catalase and decompose hydrogen peroxide into H2O and oxygen in neutral tumor microenvironment, thus reducing the oxidative damage caused by hydrogenperoxide to lung adenocarcinoma A549 cells. In acidic microenvironment, PLGA grafted γ-Fe2O3 nanoparticles could simulate the activity of peroxidase and effectively catalyze the decomposition of hydrogen peroxide to generate highly toxic hydroxyl radicals, which could cause the death of A549 cells. Furthermore, the synergistic effect of peroxidase-like activity of PLGA-grafted γ-Fe2O3 nanoparticles and doxorubicin could accelerate the apoptosisand destruction of A549 cells, thus enhancing the antitumor effect of doxorubicin-loaded PLGA-grafted γ-Fe2O3 nanoparticles. Therefore, this study provides an effective nanoplatform based on dual inorganic biomimetic nanozymes for the treatment of lung cancer.

Application of response surface methodology to the modeling of alpha-amylase purification by aqueous two-phase systems.

Mathematical models concerning the purification of alpha-amylase from the cultivation supernatant of Bacillus subtilis in a polyethylene glycol-citrate aqueous two-phase system (ATP) are established with response surface methodology. The PEG3350, citrate and sodium chloride concentrations were selected as variables to evaluate the purification impact factors in aqueous two-phase system, including partition coefficients of alpha-amylase, total protein, purification factor and alpha-amylase yield. An experimental space with two-fold purification and over 90% yield of alpha-amylase is achieved through the optimized condition basing on the model. Two systems with low viscosity within said space were further selected to perform alpha-amylase purification and the experimental results coincide well with the calculation of the models, which indicates that the model provides a promising tool for experimental design of protein purification by aqueous two-phase system.

One-step purification of alpha-amylase from the cultivation supernatant of recombinant bacillus subtilis by high-speed counter-current chromatography with aqueous polymer two-phase systems.

Purification of alpha-amylase from the cultivation supernatant of recombinant Bacillus subtilis by high-speed counter-current chromatography (HSCCC) in polyethylene glycol (PEG) 4000-inorganic salt aqueous polymer two-phase systems was studied. The effects of sodium chloride concentration on the partition coefficients of alpha-amylase and total protein were respectively tested in PEG4000-phosphate and PEG4000-citrate aqueous polymer two-phase systems to find the proper range of sodium chloride concentration for the HSCCC purification of alpha-amylase. Alpha-amylase was purified from the cultivation supernatant by HSCCC in PEG4000-phosphate system containing 2% (w/w) sodium chloride, yet with considerable loss of activity. PEG4000-citrate aqueous polymer two-phase system containing 2% (w/w) sodium chloride and supplemented with 0.56% (w/w) CaCl2 as protective agent was then successfully applied to purify alpha-amylase from cultivation supernatant by HSCCC to homogeneity and significantly increased the recovery of alpha-amylase activity from around 30 to 73.1%.

[Separation of proteins in aqueous two-phase systems with high-speed counter-current chromatography].

High-speed counter-current chromatography (HSCCC) is a continuous liquid-liquid partition chromatography, with remarkable advantages of high separation efficiency and no adsorption or denaturation by solid phase. The retention of stationary phase and the separation of proteins in polyethylene glycol 1000 (PEG1000)-phosphate aqueous two-phase system (ATPs) were studied with a multi-column high speed-counter-current chromatograph. The flow direction and speed of the mobile phase, and the rotation direction and speed of the apparatus showed different effects on the retention of the stationary phase, which reached the maximum at 33.3% with a flow rate of 0.6 mL/min and a rotation speed of 900 r/min in 14.0% PEG1000-16.0% phosphate ATPs. Distinct differences in partition coefficients among cytochrome C, lysozyme and hemoglobin were found at pH 9.2 and these three proteins were successfully separated in 14.0% PEG1000-16.0% phosphate ATPs at pH 9.2 by HSCCC with the apparatus rotating at 850 r/min and the mobile phase flow rate of 1.0 mL/min. The major protein components in hen egg white, including ovaltransferrin, ovalbumin and lysozyme also show distinct differences of partition coefficients in PEG1000-phosphate ATPs at pH 9.2. Ovalbumin and lysozyme were successfully purified to homogeneity and ovaltransferrin to ca 60% purity from the hen egg white sample with yields over 90% in 15.0% PEG1000-17.0% phosphate ATPs at pH 9.2 with the apparatus rotating at 850 r/min and mobile phase flow rate of 1.0 mL/min.

Partial purification of alpha-amylase from culture supernatant of Bacillus subtilis in aqueous two-phase systems.

A study was made of the partition and purification of alpha-amylase from a culture supernatant of Bacillus subtilis in the polyethylene glycol (PEG)--citrate aqueous two-phase system (ATPS). Factors that influenced the partition of the protein in this system, including the molecular weight of the PEG, the tie line length of ATPS, the pH value and the sodium chloride concentration, were investigated. Purification of alpha-amylase was attained with a purification factor (PF) of 1.8 and 90% yield at pH 6.0 in a PEG1000-citrate ATPS with short tie line length. By utilizing the salt-out effect of neutral salt, the purification of alpha-amylase was further improved to 2.0 of PF and 80% yield in a PEG3350-citrate ATPS with 4% sodium chloride.

Biooxidation of ferrous iron by immobilized Acidithiobacillus ferrooxidans in poly(vinyl alcohol) cryogel carriers.

PVA-cryogels entrapping about 10(9) cells of Acidithiobacillus ferrooxidans per ml of gel were prepared by freezing-thawing procedure, and the biooxidation of Fe2+ by immobilized cells was investigated in a 0.365 l packed-bed bioreactor. Fe2+ oxidation fits a plug-flow reaction model well. A maximum oxidation rate of 3.1 g Fe2+ l(-1) h(-1) was achieved at the dilution rate of 0.4 h(-1) or higher, while no obvious precipitate was determined at this time. In addition, cell-immobilized PVA-cryogels packed in bioreactor maintained their oxidative ability for more than two months under non-sterile conditions.