Mao-Sen Yuan

Simple preparation of aminothiourea-modified chitosan as corrosion inhibitor and heavy metal ion adsorbent

By a simple and convenient method of using formaldehyde as linkages, two new chitosan (CS) derivatives modified respectively with thiosemicarbazide (TSFCS) and thiocarbohydrazide (TCFCS) were synthesized. The new compounds were characterized and studied by Fourier transform infrared spectroscopy, elemental analysis, thermal gravity analysis and differential scanning calorimetry, and their surface morphologies were determined via scanning electron microscopy. These CS derivatives could form pH dependent gels. The behavior of 304 steel in 2% acetic acid containing different inhibitors or different concentrations of inhibitor had been studied by potentiodynamic polarization test. The preliminary results show that the new compound TCFCS can act as a mixed-type metal anticorrosion inhibitor in some extent; its inhibition efficiency is 92% when the concentration was 60 mg/L. The adsorption studies on a metal ion mixture aqueous solution show that two samples TSFCS and TCFCS can absorb As (V), Ni (II), Cu (II), Cd (II) and Pb (II) efficiently at pH 9 and 4.

Antifouling properties of poly(dimethylsiloxane) surfaces modified with quaternized poly(dimethylaminoethyl methacrylate).

A quaternized poly(dimethylaminoethyl methacrylate)-grafted poly(dimethylsiloxane) (PDMS) surface (PDMS-QPDMAEMA) was successfully prepared in this study via solution-phase oxidation reaction and surface-initiated atom transfer radical polymerization (SI-ATRP) using dimethylaminoethyl methacrylate (DMAEMA) as initial monomer. PDMS substrates were first oxidized in H(2)SO(4)/H(2)O(2) solution to transform the SiCH(3) groups on their surfaces into SiOH groups. Subsequently, a surface initiator for ATRP was immobilized onto the PDMS surface, and DMAEMA was then grafted onto the PDMS surface via copper-mediated ATRP. Finally, the tertiary amino groups of PolyDMAEMA (PDMAEMA) were quaternized by ethyl bromide to provide a cationic polymer brush-modified PDMS surface. Various characterization techniques, including contact angle measurements, attenuated total reflection infrared spectroscopy, and X-ray photoelectron spectroscopy, were used to ascertain the successful grafting of the quaternized PDMAEMA brush onto the PDMS surface. Furthermore, the wettability and stability of the PDMS-QPDMAEMA surface were examined by contact angle measurements. Antifouling properties were investigated via protein adsorption, as well as bacterial and cell adhesion studies. The results suggest that the PDMS-QPDMAEMA surface exhibited durable wettability and stability, as well as significant antifouling properties, compared with the native PDMS and PDMS-PDMAEMA surfaces. In addition, our results present possible uses for the PDMS-QPDMAEMA surface as adhesion barriers and antifouling or functional surfaces in PDMS microfluidics-based biomedical applications.

Spatiotemporally controlled and multifactor involved assay of neuronal compartment regeneration after chemical injury in an integrated microfluidics.

Studies on the degeneration and regeneration of neurons as individual compartments of axons or somata can provide critical information for the clinical therapy of nervous system diseases. A controllable in vitro platform for multiple purposes is key to such studies. In the present study, we describe an integrated microfluidic device designed for achieving localized stimulation to neuronal axons or somata. We observed neuronal compartment degeneration after localized chemical stimulation and regeneration under the accessorial function of an interesting compound treatment or coculture with desired cells in controllable chambers. In a spatiotemporally controlled manner, this device was used to investigate hippocampal neuronal soma and axon degeneration after acrylamide stimulation, as well as subsequent regeneration after treatment with the monosialoganglioside GM1 or with cocultured glial cells (astrocytes or Schwann cells). To gain insight into the molecular mechanisms that mediate neuronal injury and regeneration, as well as to investigate whether acrylamide stimulation to neurons induces changes in Ca(2+) concentrations, the related neuronal genes and real-time Ca(2+) signal in neurons were also analyzed. The results showed that neuronal axons were more resistant to acrylamide injury than neuronal somata. Under localized stimulation, axons had self-destruct programs different from somata, and somatic injury caused the secondary response of axon collapse. This study provides a foundation for future in-depth analyses of spatiotemporally controlled and multifactor neuronal compartment regeneration after various injuries. The microfluidic device is also useful in evaluating potential therapeutic strategies to treat chemical injuries involving the central nervous system.

Polydiacetylene liposome-encapsulated alginate hydrogel beads for Pb2+ detection with enhanced sensitivity

The development of a novel and simple method to trace lead ions (Pb2+) has received great attention due to its high toxicity to human health and the environment. In this paper, we describe a new polydiacetylene (PDA)-based liposome sensor for the colorimetric and fluorometric detection of Pb2+ in aqueous solution and in alginate hydrogel microbeads. In the sensor system, a dopamine group was rationally introduced into a diacetylene monomer to work as a strong binding site for Pb2+. The dopamine-functionalized monomer and 10,12-pentacosadiynoic acid (PCDA) were then incorporated into PDA liposomes in aqueous solution. After UV light-induced polymerization, deep blue colored liposome solutions were obtained. Upon the addition of various metal ions into the liposome solution, only Pb2+ could cause a distinct color change from blue to red and a dramatic fluorescence enhancement. To further improve its sensitivity and address its intrinsic aggregation, we then developed a liposome-immobilized detection system by encapsulating PDA–DA liposomes into alginate hydrogel beads through a microfluidic droplet-based method. The results showed that the PDA–DA liposome-containing hybrid hydrogel beads possessed excellent stability and high sensitivity. These interesting findings demonstrated that the PDA liposome system developed in the current study may offer a new method for Pb2+ recognition in a more efficient manner.

Synthesis of polyethylene glycol- and sulfobetaine-conjugated zwitterionic poly(L-lactide) and assay of its antifouling properties.

A new antifouling polyester monomethoxy-poly(ethylene glycol)-b-poly(L-lactide)-b-poly(sulfobetaine methacrylate) (MPEG-PLA-PSBMA) was obtained by ring-opening polymerization of L-lactide, and subsequent click chemistry to graft the azide end-functionalized poly(sulfobetaine methacrylate) (polySBMA) moieties onto the alkyne end-functionalized MPEG-PLA (MPEG-PLA-alkyne). The chemical structure of the polymer was characterized using (1)H nuclear magnetic resonance and Fourier-transform infrared spectroscopy, and its physical properties (including molecular weight, glass transition temperature, and melting point) were determined using gel permeation chromatography and differential scanning calorimetry. To investigate its hydrophilicity and stability, as well as its antifouling properties, the polymer was also prepared as a surface coating on glass substrates. The wettability and stability of this polyester was examined by contact angle measurements. Furthermore, its antifouling properties were investigated via protein adsorption, cell adhesion studies, and bacterial attachment assays. The results suggest that the prepared zwitterionic polyester exhibits durable wettability and stability, as well as significant antifouling properties. The new zwitterionic polyester MPEG-PLA-PSBMA could be developed as a promising antifouling material with extensive biomedical applications.

Synthesis and Biological Evaluation of Apigenin Derivatives as Antibacterial and Antiproliferative Agents

Two series of apigenin [5,7-dihydroxy-2-(4-hydroxyphenyl)-4H-chromen-4-one] derivatives, 3a–3j and 4a–4j, were synthesized. The apigenin and alkyl amines moieties of these compounds were separated by C2 or C3 spacers, respectively. The chemical structures of the apigenin derivatives were confirmed using 1H-NMR, 13C-NMR, and electrospray ionization mass spectroscopy. The in vitro antibacterial and antiproliferative activities of all synthesized compounds were determined. Among the tested compounds, 4a–4j displayed significant antibacterial activity against the tested strains (Staphylococcus aureus, Bacillus subtilis, Escherichia coli, and Pseudomonas aeruginosa). Additionally, 4i showed the best inhibitory activity with minimum inhibitory concentrations of 1.95, 3.91, 3.91, and 3.91 μg/mL against S. aureus, B. subtilis, E. coli, and P. aeruginosa, respectively. The antiproliferative activity of the apigenin derivatives was evaluated by an MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] assay. We determined that 4a–4j displayed better growth inhibition activity against four human cancer cell lines, namely, human lung (A549), human cervical (HeLa), human hepatocellular liver (HepG2), and human breast (MCF-7) cancer cells, than the parent apigenin. Compound 4j was found to be the most active antiproliferative compound against the selected cancer cells. Structure-activity relationships were also discussed based on the obtained experimental data.

Effects of poly(L-lysine)-modified Fe3O4 nanoparticles on endogenous reactive oxygen species in cancer stem cells.

Intracellular reactive oxygen species (ROS) have been extensively shown to play an important role in the regulation of cell proliferation and cell cycle progression. The effects of endogenous ROS on the proliferation and differentiation of cancer stem cells (CSCs) have received increasing attention because of the unique properties of these cells that allow them to drive tumor growth and evade conventional cancer therapies. In this study, poly(L-Lysine) (PLL)-modified Fe(3)O(4) nanoparticles were synthesized to label CSCs derived from U251 glioblastoma multiform. A featured peroxidase-like activity within PLL-modified Fe(3)O(4) nanoparticles that could greatly reduce intracellular H(2)O(2) activity was identified. We also found that PLL-modified Fe(3)O(4) nanoparticles could accelerate the progression of CSC cell cycle, probably due to the impaired activity of endogenous ROS in CSCs. These results show that growth and proliferation of CSCs could be promoted by Fe(3)O(4) nanocarriers in an ROS-dependent manner, and Fe(3)O(4) nanocarriers may be suitable for certain tumor therapies as a drug delivery system.

Reversible luminescence color switching in the crystal polymorphs of 2,7-bis(2′-methyl-[1,1′-biphenyl]-4-yl)-fluorenone by thermal and mechanical stimuli

Smart organic luminescence materials that exhibit a reversible stimuli-responsive change of luminescence color in the solid state without changing the chemical structure of their component molecules have attracted increasing interest. We employed the design strategy of introducing different weak interactions into the same molecular system to synthesize 2,7-bis(2′-methyl-[1,1′-biphenyl]-4-yl)-fluorenone (MPF). Two crystal polymorphs of MPF, green-yellow crystal G-MPF and orange crystal O-MPF, were obtained through culturing the single crystal under the different crystallization conditions of diffusing diethyl ether into its respective tetrahydrofuran or CH2Cl2 solution. Both of the two crystal polymorphs exhibit high luminous efficiency and reversible stimuli-responsive solid-state luminescence color switching. Upon heating the green crystal G-MPF or grinding the orange crystal O-MPF, their emission reversibly changes between green at 530 nm and orange at 570 nm. The X-ray single-crystal structures, characterization of the photophysical properties, powder X-ray diffraction and differential scanning calorimetry provide insight into the phase transformation and the luminescence behavior. The results indicate that the green emission of G-MPF originates from molecular J-aggregation and the orange emission of O-MPF originates from static excimers. This work discusses the relationship between the molecular stacking mode and the photophysical properties, and demonstrates a molecular design strategy to obtain stimuli-responsive organic solid-state luminescence switching materials.

Au nanoparticles/poly(caffeic acid) composite modified glassy carbon electrode for voltammetric determination of acetaminophen.

An Au nanoparticles/poly(caffeic acid) (AuNPs/PCA) composite modified glassy carbon (GC) electrode was prepared by successively potentiostatic technique in pH 7.4 phosphate buffer solution containing 0.02mM caffeic acid and 1.0mM HAuCl4. Electrochemical characterization of the AuNPs/PCA-GC electrode was investigated by electrochemical impedance spectroscopy and cyclic voltammetry. The electrochemical behavior of acetaminophen (AP) at the AuNPs/PCA-GC electrode was also studied by cyclic voltammetry. Compared with bare GC and poly(caffeic acid) modified GC electrode, the AuNPs/PCA-GC electrode was exhibited excellent electrocatalytic activity toward the oxidation of AP. The plot of catalytic current versus AP concentration showed two linear segments in the concentration ranges 0.2-20µM and 50-1000µM. The detection limit of 14 nM was obtained by using the first range of the calibration plot. The AuNPs/PCA-GC electrode has been successfully applied and validated by analyzing AP in blood, urine and pharmaceutical samples.

Click synthesis of neutral, cationic, and zwitterionic poly(propargyl glycolide)-co-poly(ɛ-caprolactone)-based aliphatic polyesters as antifouling biomaterials.

With the development of polymer-based biomaterials, aliphatic polyesters have attracted considerable interest because of their non-toxicity, non-allergenic property, and good biocompatibility. However, the hydrophobic nature and the lack of side chain functionalities of aliphatic polyesters limit their biomedical applications. In this study, we prepared four new polyesters: poly(sulfobetaine methacrylate)-, poly(2-methacryloyloxyethyl phosphotidylcholine)-, poly(ethylene glycol)-, and quaternized poly[(2-dimethylamino)ethyl methacrylate]-grafted poly(propargyl glycolide)-co-poly(ɛ-caprolactone). Their synthesis was conducted through ring-opening polymerization of acetylene-functionalized lactones and subsequent graft of bioactive units using click chemistry. The chemical structures of the polyesters were characterized through nuclear magnetic resonance and Fourier-transform infrared spectroscopy, and their physical properties (including molecular weight, glass transition temperature, and melting point) were determined using gel permeation chromatography and differential scanning calorimetry. For studies on their hydrophilicity, stability, and anti-bioadhesive property, a series of polymeric surfaces of these polyesters was prepared by coating them onto glass substrates. The hydrophilicity and stability of these polyester surfaces were examined by contact angle measurements and attenuated total reflection Fourier-transform infrared spectroscopy. Their anti-bioadhesive property was investigated through protein adsorption, as well as cellular and bacterial adhesion assays. The prepared polyesters showed good hydrophilicity and long-lasting stability, as well as significant anti-fouling property. The newly prepared polyesters could be developed as promising anti-fouling materials with extensive biomedical applications.