Preparation of fluorescein-modified polymer dots and their application in chiral discrimination of lysine enantiomers.

Fluorescein-functionalized fluorescent polymer dots (F-PDs) were prepared by a facile one-pot method by magnetic stirring under mild conditions based on carboxymethylcellulose (CMC) and fluorescein as the precursors. The obtained F-PDs exhibited a nanoscale size of 3.2 ± 1.1 nm, excellent water solubility, and bright yellow fluorescence emission with a fluorescence quantum yield of 12.0%. The fluorescent probe displays rapid and sensitive chiral discrimination for lysine focused on different complexation abilities between lysine enantiomers and Cu2+. The concentration of L-lysine in the range 4 to 14 mM (R2 = 0.997) was measured by the fluorescence intensity ratio (I513/I429); the exitation wavelength was set to λex = 365 nm. The detection limit was 0.28 mM (3σ/slope). Importantly, this sensor accurately predicted the enantiomeric excess (ee) of lysine enantiomers at the designed concentration (lysine: 20 mM; Cu2+: 10 mM) ranges. The proposed sensor was successfully applied to determine L-lys (recovery: 95.8-101%; RSD: 0.465-3.34%) and ee values (recovery: 98.5-102%; RSD: 2.61-3.21%) in human urine samples using the standard addition method.

Preparation of boronic acid-modified polymer dots under mild conditions and their applications in pH and glucose detection.

For the first time, boronic acid-modified polymer dots (B-PDs) were fabricated by a "synthesis-modification integration" route using polyethylenimine (PEI) and phenylboronic acid as precursors. Under optimized preparation conditions, the B-PDs exhibited an average size of 2.2 nm, good water solubility, and high fluorescence quantum yield of 8.69%. The B-PDs showed reversible fluorescence response in acid solutions (blue emissions) and alkaline solutions (green emissions). The fluorescence emissions of B-PDs demonstrated an obvious red shift with varying the pH value from 1 - 13. Moreover, glucose could assemble on the surface of B-PDs due to the reversible reaction between boronic acid and cis-diols, which resulted in a blue shift of emission wavelength and an obvious increase of FL intensity at λex = 380 nm based on the aggregation-induced enhancement effect. The glucose sensing method was thus developed in the range 0.0001 - 1.0 mol L-1. Applications to real human blood and glucose injection samples demonstrated satisfactory results. The B-PDs based on the analytical method display good selectivity, wide detection range, and simplicity in preparation and detection, implying promising applications as a practical platform for biosensing.

Kinetic, isotherm, and thermodynamic studies of the adsorption of dyes from aqueous solution by cellulose-based adsorbents.

In this study, a highly efficient and eco-friendly porous cellulose-based aerogel was synthesized by grafting polyethyleneimine onto quaternized cellulose (PQC) to remove the anionic dye Congo Red (CR). The prepared aerogel had a good flexibility and formability. The adsorbents were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy and elemental analysis. The results showed that there were many amino groups on CE/PQC aerogel and the structure was porous, which increased the adsorption capacity. The effects of initial concentration, adsorbent dose, contact time, temperature, and pH on the dye sorption were all investigated. The adsorption mechanism was also explored, including adsorption kinetics, adsorption isotherms and thermodynamic studies of adsorption. The results showed that the adsorption kinetics and isotherms fitted the pseudo-second-order kinetic model and Langmuir isotherm, respectively. The Langmuir isotherm revealed that the maximum theoretical adsorption capacity of the aerogels for CR was 518.403 mg g-1. The thermodynamic parameters including Gibbs free energy change (ΔG0), enthalpy change (ΔH0) and entropy change (ΔS0), showed the adsorption process was exothermic and spontaneous. These results imply that this new absorbent can be universally and effectively used for the removal of dyes from industrial textile wastewater.

[Effects of fluorescent labeling on cytotoxic characteristic and cell distribution of nanopolystyrene].

OBJECTIVE: To explore the feasibility that studied with fluorescent labeling nano-scale materials cell kinetics. METHODS: At the doses of 500, 250, 125, 63, 32 and 16 microg/ml and at the times of 48, 24, 16, 8, 4 and 1 h , MTT assay was applied to observe the inhibitory effects in BEAS-2B and THP-1 cell lines treated with fluorescent labeling nanopolystyrene and non-labeling nanopolystyrene. Confocal microscopy and transmission electron microscopy were applied to image the translocation of fluorescent labeling nanopolystyrene and non-labeling nano polystyrene into cells. Results The tendency of cell inhibitory rate both in fluorescent labeling nanopolystyrene and non-labeling nanopolystyrene was same, which increase with the dose increase. There were no significant differences in the same dose group for two kinds of materials (P > 0.05). The two kinds of materials were found to enter the BEAS-2B and THP-1 on 1 h, and localized within the cell nucleus on 4 h. CONCLUSION: There were no obvious influence on cytotoxicity and cell distribution for fluorescent labeling . Fluorescent labeling nanopolystyrene could apply to study cell kinetics equal to the same size nanopolystyrene.

Rapid microwave-assisted synthesis of molecularly imprinted polymers on carbon quantum dots for fluorescent sensing of tetracycline in milk.

In this paper, a novel, selective and eco-friendly sensor for the detection of tetracycline was developed by grafting imprinted polymers onto the surface of carbon quantum dots. A simple microwave-assisted approach was utilized to fabricate the fluorescent imprinted composites rapidly for the first time, which could shorten the polymerization time and simplify the experimental procedure dramatically. The novel composites not only demonstrated excellent fluorescence stability and special binding sites, but also could selectively accumulate target analytes. Under optimal conditions, the relative fluorescence intensity of the composites decreased linearly with increasing the concentration of tetracycline from 20 nM to 14 µM. The detection limit of tetracycline was 5.48 nM. The precision and reproducibility of the proposed sensor were also acceptable. Significantly, the practicality of this ultrasensitive sensor for tetracycline detection in milk was further validated, revealing the advantages of simplicity, sensitivity, selectivity and low cost. This approach combines the high selective adsorption property of molecular imprinted polymers and the sensitivity of fluorescence detection. It is envisioned that the development of fluorescent molecularly imprinted composites will offer a new way of thinking for rapid analysis in complex samples.

Determination triazine pesticides in cereal samples based on single-hole hollow molecularly imprinted microspheres.

Single-hole hollow molecularly imprinted microspheres (h-MIMs) were prepared by hard template method and applied to extract six triazine pesticides in cereal samples, followed by HPLC-MS/MS detection. The synthesis mechanism of the h-MIMs has been studied. The h-MIMs exhibited bigger specific surface area and much higher binding capacity than the molecularly imprinted polymers prepared by precipitation polymerization (p-MIPs) and surface polymerization (s-MIPs). Besides, the adsorption rate of h-MIMs to prometryn was significantly higher than that of p-MIPs and s-MIPs. Owing to the hollow structure of the h-MIMs, more binding cavities were located on the inner and outer surfaces of the h-MIMs, which could facilitate the removal of template molecules from the polymers and the rebinding of the target molecules to the polymers. Under the optimal conditions, the detection limits of triazines are in the range of 0.08-0.16ngg(-1). At the spiked level (5ngg(-1)), the recoveries of triazines are in the range of 81±4% to 96±4%. The proposed method was successfully applied to determine six triazines in five cereal samples. Atrazine was found in two rice samples and a wheat sample with the contents of 5.1, 6.7 and 5.6ngg(-1), respectively. Ametryn and prometryn were found in a maize sample with the contents of 7.6 and 7.3ngg(-1), respectively.

Enhanced healing of rabbit segmental radius defects with surface-coated calcium phosphate cement/bone morphogenetic protein-2 scaffolds.

Large osseous defects remain a difficult clinical problem in orthopedic surgery owing to the limited effective therapeutic options, and bone morphogenetic protein-2 (BMP-2) is useful for its potent osteoinductive properties in bone regeneration. Here we build a strategy to achieve prolonged duration time and help inducting new bone formation by using water-soluble polymers as a protective film. In this study, calcium phosphate cement (CPC) scaffolds were prepared as the matrix and combined with sodium carboxymethyl cellulose (CMC-Na), hydroxypropylmethyl cellulose (HPMC), and polyvinyl alcohol (PVA) respectively to protect from the digestion of rhBMP-2. After being implanted in the mouse thigh muscles, the surface-modified composite scaffolds evidently induced ectopic bone formation. In addition, we further evaluated the in vivo effects of surface-modified scaffolds in a rabbit radius critical defect by radiography, three dimensional micro-computed tomographic (µCT) imaging, synchrotron radiation-based micro-computed tomographic (SRµCT) imaging, histological analysis, and biomechanical measurement. The HPMC-modified CPC scaffold was regarded as the best combination for segmental bone regeneration in rabbit radius.

Bone regeneration using cell-mediated responsive degradable PEG-based scaffolds incorporating with rhBMP-2.

The treatment of large osseous defects remains a challenging clinical problem in orthopedic surgery. Particularly, strategies to control the appropriate degradation rate adapting to the tissue reconstruction are of essential for tissue regeneration. Here we report on a strategy to achieve adaptive degradation rate using cell-secreted protease as a switch. Disulfide-containing PEG-based scaffolds have been synthesized, and demonstrated to be responsive to the cell-secreted redox microenvironment. Thus, the cell-triggered degradation and liberation of growth factor are achieved. The osteoinductive growth factor, recombinant human bone morphogenetic protein-2 (rhBMP-2), is incorporated into the scaffold for bioactivity promotion. Degradations under the stimuli of reduced glutathione (GSH) at intracellular and extracellular concentrations was studied with the results of duration time ranging from 0.5 h to 22 days regulated by both concentrations of redox medium and polymer precursors. The rhBMP-2 loaded scaffolds evidently induced the ectopic bone formation in the mouse thigh muscles. In addition, we further investigated the in vivo effects of rhBMP-2-loaded scaffolds in a rabbit radius critical defect by radiography, three dimensional micro-computed tomographic (µCT) and synchrotron radiation-based micro-computed tomography (SRµCT) imaging, histological analysis, and biomechanical measurement. Scaffolds underwent gradual resorption and replacement by new bone and induced reunion of bone marrow cavity at 12 weeks, much better than the effect of self-repairing group. The results indicated that both osteoinduction and appropriate degradation played a crucial role in accelerating and promoting bone augmentation, as well as effective proangiogenesis. Such a strategy appears promising as 3D temporal scaffolds for potential orthopedic applications.

Fast determination of sulfonamides and their acetylated metabolites from environmental water based on magnetic molecularly imprinted polymers.

Group-selective magnetic molecularly imprinted polymers (MMIPs) that can extract four widely used sulfonamide antibiotics and their acetylated metabolites from environmental water were synthesized in this study. The MMIPs with saturation magnetization value of 16.7 emu g(-1) could be separated from the environmental water samples easily by the application of an adscititious magnetic field, reducing the time consumption of pretreatment. The extraction conditions were evaluated, and optimal extraction conditions were as follows: extraction time, 25 min; amount of polymers, 90 mg; washing solvent, 30 % methanol aqueous solution; and elution solvent, methanol-acetic acid (95:5, v/v). The target analytes were detected by liquid chromatography-tandem mass spectrometry, and the detection limits of the method are in the range of 0.38-1.32 ng L(-1). The relative standard deviations of intra- and inter-day are in the range of 1.3-6.8 % and 1.7-9.1 %, respectively. The proposed method is suitable for the analysis of environmental water samples.

Comparison of humic acid rejection and flux decline during filtration with negatively charged and uncharged ultrafiltration membranes.

Increasingly stringent regulations for drinking water quality have stimulated the ultrafiltration (UF) to become one of the best alternatives replacing conventional drinking water treatment technologies. However, UF is not very effectively to remove humic acid due to the comparatively larger pore size compared to the size of humic acid. Fouling issue is another factor that restricts its widespread application. In this study, rejection of humic acid and flux decline were compared with essentially neutral, negatively charged version of a regenerated cellulose membrane, in which electrostatic interaction was explored for a better humic acid removal and less fouling. Solution environment, including ionic strength, pH and calcium ion concentration, affecting humic acid removal and flux decline on negatively charged and neutral membranes was also compared. Results indicated that the appropriate charge modification on the neutral UF membrane could be an effective way for better removal of NOM and reduction of the membrane fouling due to the electrostatic interactions with the combination effect of membrane pore size. Electrostatic interactions are significant important to achieve high humic acid removal and less fouling, and to improve the water quality and protect people's health.

[Comparison of the effect of solution environment on humic acid removal behavior with charged and traditional neutral ultrafiltration membranes].

Experiments were performed to evaluate the effect of solution environment (pH value, ionic strength and Ca2+) on humic acid removal and membrane fouling during filtration of humic acid through charge-modified regenerated (RC) ultrafiltration (UF) membrane and traditional unmodified neutral RC UF membrane. Results showed that: (1) the pH value changed the net charge on humic acid molecule and charged membrane through protonation effect, which further influenced the ultrafiltration behavior. When the solution pH value decreased from 7.5 to 3.5, the rejection coefficient of HA decreased from 92% to 79%, and the flux decline increased from 26% to 36% at 4 h filtration time on charged UF membrane; (23) the ionic strength influenced the ultrafiltration behavior through the change of humic acid molecule property and electrostatic shielding effect. In each solution with ionic strength of 0 mmol/L, 3 mmol/L and 100 mmol/L, the rejection coefficient decreased with the value of 92%, 87% and 48% respectively, and the flux decline increased with the value of 26%, 35% and 63% respectively at 4 h filtration time on charged membranes; (3) the effect of Ca2+ concentration on ultrafiltration behavior was due to the complementary effects of electrostatic shielding, Ca2+ bridge and the compact property of the cake layer. (4) the effect of pH value, ionic strength and Ca2+ concentration on the neutral membrane was similar to that on the charged membrane, but in different degrees. Results provide important guidance on the choice of appropriate solution environment when using charged ultrafiltration technology.

[Effect of charged ultrafiltration membrane on natural organic matter removal and membrane fouling].

With the deterioration of water pollution and stringency of water standards, ultrafiltration (UF) has become one of the best alternatives replacing conventional drinking water treatment technologies. However, UF is not very effectively to remove natural organic matter (NOM) due to the comparatively large pore size compared to the size of NOM. Fouling issue is another factor that restricts its widespread application. The rejection coefficient and flux decline during ultrafiltration of humic acid (HA) and raw water through neutral unmodified and negatively charge-modified regenerated cellulose (RC) membranes were investigated, and the analysis for membrane resistance was provided. The initial removal rate for HA is 59% and the flux decline is 32% on neutral unmodified RC membrane with MWCO of 100 x 10(3), while the initial removal rate for HA increases to 92% and the flux decline decreases to 25% on negatively charge-modified RC membrane. Compared to neutral unmodified RC membrane, the removal rate for NOM on negatively charge-modified RC membrane increases 20% and the flux decline decreases 12%. Results indicated that charged UF membrane could be an effective way for better removal of NOM and reduction of the membrane fouling due to the electrostatic interaction with the combination effect of membrane pore size.