Utilizing Cell Culture Assisted Anodization to Fabricate Aluminium Oxide with a Gradient Microstep and Nanopore Structure.

Anodic aluminum oxide (AAO) with a gradient microstep and nanopore structure (GMNP) is fabricated by inversely using cell culture to control the reaction areas in the electrochemical anodization, which shows a larger porosity than that of typical planar AAO. The figure of the microstep is influenced by the cell dehydration temperature which controls the cell shrinkage degree. A GMNP AAO with a diameter of 2.5 cm is achieved. Polymer with a gradient microstep and nanonipple structure is fabricated using the GMNP AAO as the template, which denotes that GMNP AAO could become a broad platform for the structural preparation of various materials with advanced functions.

Interaction of graphene oxide with lysozyme:Insights from conformational structure and surface charge investigations.

Lysozyme (Lyz) is an important antibacterial protein that exists widely in nature. In recent years, the application of graphene oxide (GO) in the field of biotechnology electronics, optics, chemistry and energy storage has been extensively studied. However, due to the unique properties of GO, the mechanism of its interaction with biomacromolecule proteins is very complex. To further explore the interaction between GO and proteins we explore the influence of different pH and heat treatment conditions on the interaction between GO and Lyz, the GO (0-20 µg/mL) was added at a fixed Lyz concentration (0.143 mg/mL) under different pHs. The structure and surface charge changes of Lyz were measured by spectroscopic analysis and zeta potential. The results showed that the interaction between GO and Lyz depends on temperature and pH, significant changes have taken place in its tertiary and secondary structures. By analyzing the UV absorption spectrum, it was found that lysozyme and GO formed a stable complex, and the conformation of the enzyme was changed. In acidic pH conditions (i.e., pH < pI), a high density of Lyz were found to adsorb on the GO surface, whereas an increase in pH resulted in a progressive decrease in the density of the adsorbed Lyz. This pH-dependent adsorption is ascribed to the electrostatic interactions between the negatively charged GO surface and the tunable ionization of the Lyz molecules. The secondary structure of Lyz adsorbed on GO was also found to be highly dependent on the pH. In this paper, we investigated the exact mechanism of pH-influenced GO binding to lysozyme, which has important guidance significance for the potential toxicity of GO biology and its applications in biomedical fields such as structure-based drug design.

The impact of fluoxetine and pH values on relaxation of the ternary lipid monolayers.

Fluoxetine (FLX), used in the clinic to treat depression, is a well-known cationic amphiphilic antidepressant. To get a deeper insight into the effect of FLX on Langmuir monolayers, in this study the stability and relaxation of 1,2-dioctadecanoyl-sn-glycero-3-phophocholine/1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine/cholesterol (DSPC/POPC/CHOL) monolayers without and with FLX at different pH values were studied. The experiments involved surface pressure-area (π-A) measurements, mean molecular area-time (A-t) measurements, and atomic force microscope (AFM) analysis. It was found that intermolecular interactions decreased after the addition of FLX in the subphase but increased with increasing pH values. The relaxation of the ternary lipid monolayers with FLX was dominated by dissolution steps, and the dissolution rates decreased with increasing pH values. These findings can be easily confirmed by the analysis of thermodynamic parameters calculated for the investigated films. The data obtained in this study help to understand the effect of drugs on the ternary lipid monolayers from the molecular point of view.

Physical field simulation of the ultrasonic radiation method: An investigation of the vessel, probe position and power.

In this paper, the effects of ultrasonic probe position, vessel shape, and ultrasonic input power on the sound pressure distribution in the reactor were investigated by solving the Helmholtz equation using COMSOL Multiphysis@ software. Three different types of glass containers were used in the study, which are beaker, Erlenmeyer flask, and round bottom flask. The maximum value of sound pressure in the three containers will gradually increase when the distance between the probe and the bottom of the container decreases. When the distance decreases, the area of the high acoustic pressure region in the round bottom flask does not change significantly, while the area of the high acoustic pressure region in the beaker and Erlenmeyer flask increases sharply, which means that the use of the round bottom flask can reduce the influence of the dead zone on the preparation of nanomaterials. In addition, the change in power increases the value of the peak negative acoustic pressure in the vessel, enhancing the response efficiency of ultrasonic cavitation.

The interaction of graphene oxide-silver nanoparticles with trypsin: Insights from adsorption behaviors, conformational structure and enzymatic activity investigations.

In this work, we synthesized graphene oxide-silver nanoparticles (GO-AgNPs) hybrids by one-pot method. Since there are relatively few reports on whether GO-AgNPs bind and change the structure and function of trypsin, A variety of methods were employed to systematically characterize the molecular interaction between GO-AgNPs and trypsin. Results exhibited that GO-AgNPs bound with trypsin to form a ground state complex. GO-AgNPs had higher adsorption capacity for trypsin compared with single GO. Langmuir-Blodgett assembly method was used to confirm that AgNPs did not interfere with the adsorption of trypsin by GO. The secondary structure and the microenvironment of amino acid residues of trypsin were altered after interacting with GO-AgNPs. In addition, GO-AgNPs can enhance the activity of trypsin and promote the hydrolysis of bovine serum protein (BSA) by trypsin. These findings provide important support for the application of GO-based nanocomposites in the efficient immobilization of enzymes.

Fabrication of graphene oxide and sliver nanoparticle hybrids for fluorescence quenching of DNA labeled by methylene blue.

Since graphene oxide­silver nanoparticles (GO-AgNPs) have special affinities to DNA, it become increasingly important in fields of biological analysis in which GO-AgNPs nanocomposites universally functioned as a quencher. In this paper, GO-AgNPs nanocomposites with different GO to AgNPs ratios were synthesized as a fluorescence quencher to interact with DNA labeled by methylene blue (MB). The results showed that the fluorescence intensity of DNA-MB system decreased with the increasing of GO-AgNPs nanocomposites concentration. The quenching phenomenon of DNA-MB by AgNPs and GO was not a simple additive effect but a synergistic effect. The quenching efficiency of synthesized GO-AgNPs nanocomposites with different ratios (1:1, 1:3, 1:5, 1:10) increased with the decrease of GO/Ag ratio. Thermodynamic analysis was employed to investigate the interaction of GO-AgNPs and DNA-MB, it can be concluded that the intermolecular force between GO-AgNPs and DNA-MB was hydrogen bonding. Our works will provide important theoretical and experimental bases for fluorescence sensing of DNA.

Superhydrophobic-Superhydrophilic Hybrid Surface with Highly Ordered Tip-Capped Nanopore Arrays for Surface-Enhanced Raman Scattering Spectroscopy.

The designed superhydrophobic-superhydrophilic hybrid surface (SSHS) with highly ordered tip-capped nanopore arrays can be used as an intelligent and fast platform to realize different analyte solutions with different concentrations to be detected at the same time by surface-enhanced Raman spectroscopy. This surface is fabricated in a large area by a facile and low-cost method of programmed multistep anodization of aluminum and pore widening process followed by selective chemical modification. The highly ordered tip-capped nanopore arrays can induce the highly sensitive and reproducible Raman signal, whose enhanced factor for rhodamine 6G (R6G) at 1358 cm-1 is 4.46 × 106. The superhydrophobic-superhydrophilic hybrid property can realize the homogeneous distribution of the concentrated analyte in a droplet at the fixed place, which can avoid the diffusion-limit problem and further enhance the Raman signal. Surface-enhanced Raman spectroscopy of dried droplets with different concentrations of R6G or thiram is tested on SSHS, which show good reproducibility. The detection limits of R6G and thiram on SSHS are 10-10 and 10-7 M in 50 µL droplets, respectively. Due to the industrial compatibility of the fabrication technique, this smart surface has the potential to evolve into a general platform to develop various advanced chemical and biological sensors.

Effect of fluoxetine at different concentrations on the adsorption behavior of Langmuir monolayers.

Fluoxetine (FLX), approved for the treatment of depression and anxiety by the FDA in 2002, is an amphiphilic antidepressant. In general, amphiphilic drugs have high membrane permeability. Therefore, the interactions between these drugs and monolayers have been widely concerned. In this study, the adsorption of FLX on dipalmitoylphosphatidylcholine (DPPC) monolayers at different concentrations and surface pressures have been investigated by pressure-area isotherms (π-A), adsorption curves, compression-expansion curves, and atomic force microscopy (AFM). Our data showed that the adsorption behavior was related to the surface pressures and FLX concentrations in the subphase. The FLX that was added in the subphase under lower surface pressure (π = 10 mN/m) was easily adsorbed on DPPC monolayers. The stability of the monolayers was strong. The adsorption of FLX on DPPC monolayers and the stability decreased when π = 20 mN/m. In addition, the adsorption behavior and stability increased with increasing FLX concentrations. The AFM images of the monolayers confirmed the results of fitted adsorption curves. This study will be critical to our understanding of the interactions between drugs and lipid monolayers.

Studies on the interfacial behavior of DPPC/DPPG mixed monolayers in the presence of fluoxetine.

In this study, the interfacial behavior of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine/1,2-dipalmitoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (DPPC/DPPG) mixed monolayers with fluoxetine (FLX) in the subphase was investigated by a combination of the Langmuir-Blodgett technique and atomic force microscopy (AFM). It was found that DPPC/DPPG mixed monolayers showed different interfacial behaviors before and after addition of FLX in the subphase. The electrostatic interaction between FLX and lipids molecules destroys the homogeneity of the mixed monolayers and changes the arrangement of lipids molecules at the interface after addition of FLX in the subphase, thereby leading to an increase of compressibility and miscibility and a decrease in the stability of the mixed monolayers. The surface morphology of the mixed monolayers observed by AFM was different between without and with FLX in the subphase, indicating the penetration of FLX into the mixed monolayers. The present study has provided detailed information for further understanding the interactions of drugs with membrane lipids in other lipid monolayers.

Bovine hemoglobin adsorption onto modified silica nanoparticles: Multi-spectroscopic measurements based on kinetics and protein conformation.

Herein, the effects of bovine hemoglobin (BHb) binding to hydrophilic silica nanoparticles (SN1) and hydrophobic silica nanoparticles (SN2) were explored under physiological conditions. SEM and XRD were used to characterize silica nanoparticles (SNs). Zeta potential and DLS confirmed the formation of protein corona (PC), and SN2 showed more increase in their size after PC formation comparing with SN1. The adsorption isotherms were fitted well by the Freundlich model, and the kinetics tended to follow pseudo-second-order kinetics. Then, the second structure of BHb has been analyzed by UV-vis and FT-IR spectroscopy, which implied the impact of SN2 on the secondary structure of BHb was greater than that of SN1 on BHb. Moreover, fluorescence spectroscopy and Raman spectroscopy showed that SNs may induce heme degradation to form fluorescent heme product, resulting in increased fluorescence intensity. This investigation will be significant in exploring the toxicity profile of SNs for their in vivo.

Modulation of membrane properties by DNA in liposomes: A spectroscopic study.

Liposome mediated DNA transport possesses a number of preventing diseases in clinical trials, thus, the study of interaction between DNA and liposomes has become a hot research direction. In this paper, the adsorption behavior of DNA onto two representative lipids had been studied by the fluorescence spectrum measurement, Ultraviolet absorption spectrum and Langmuir-Blodgett technology. The results of fluorescence spectrum measurement indicated that the fluorescence liposomes were quenched statically by DNA at all three temperatures. Thermodynamic analysis displayed that the intermolecular forces between DNA and liposomes were van der Waals forces and Hydrogen bonding. The experimental results of Ultraviolet absorption spectrum and Langmuir-Blodgett technology further verified these mechanisms. This work provides useful theoretical basis for the development of novel DNA delivery materials.

Carbon quantum dots (CQDs) modified ZnO/CdS nanoparticles based fluorescence sensor for highly selective and sensitive detection of Fe(III).

A simple and fast spectrofluorimetric method coupled with carbon quantum dots (CQDs) modified ZnO/CdS nanoparticles was developed for the detection of Ferric iron (Fe(III)). The fluorescence of CQDs/ZnO/CdS NPs was effectively quenched by Fe(III) due to the strong interaction between the CQDs/ZnO/CdS NPs and Fe(III). In addition, the detection limit of Fe(III) was about 1.72×10-7M. The effect of foreign ions on the fluorescence intensity of CQDs/ZnO/CdS NPs showed that the interference response in detecting of Fe(III) ions was low. Moreover, the quenching of Fe(III) and CQDs/ZnO/CdS NPs was discussed to be a static quenching procedure, which was proved by quenching constant KSV and fluorescence lifetime τ. The study of thermodynamics showed that the values of entropy change (ΔS) and enthalpy change (ΔH) were both positive, and the value of free energy (ΔG) was negative, which implied that the weak interaction of the molecular between CQDs/ZnO/CdS NPs and Fe(III) was hydrophobic force, and the quenching process was endothermic and spontaneous.

Studied on sonocatalytic degradation of Rhodamine B in aqueous solution.

This paper describes experimental results of degradation of Rhodamine B (RB) by vortex scattering ultrasound in aqueous solution. Vortices are produced by a high-speed agitator. The effects of different factors on the degradation of RB solution were studied, such as different reaction container, the initial concentration of RB, stirring speed and ultrasonic frequencies. Ultraviolet-visible spectrophotometer (UV) was used to measure the absorbance value of RB to assess degradation rate. The optimal experimental condition was three-necked bottle, stirring speed of 700 r/min, initial concentration of 10 mg/L and ultrasonic frequency of 40 kHz. The optimal degradation rate of RB can reach 98% within one hour. The combination of ultrasonic irradiation and mechanical stirring was discovered that can degrade the RB efficiently in aqueous solution. The investigation of mechanism demonstrates that the cavitation bubbles produced by agitation play a major role in promoting degradation. COMSOL Multiphysics (Version 5.3a) software was used to simulate this process. And the method of combination of ultrasonic irradiation and mechanical stirring has also been shown to be effective in degrading methylene blue, bromophenol blue and Congo red. So the combination of ultrasonic irradiation and mechanical stirring can be used as an option for treating organic wastewater in the future. This study established a new way to degrade other organic pollutants.

Effect of Fe3O4 Nanoparticles on Mixed POPC/DPPC Monolayers at Air-Water Interface.

Fe3O4 nanoparticles (NPs) as a commonly used carrier in targeted drug delivery are widely used to carry drugs for the treatment of diseases. However, the mechanism of action of between Fe3O4 NPs and biological membranes is still unclear. Therefore, this article reports the influence of hydrophilic and hydrophobic Fe3O4 NPs on mixed 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) that were studied using the Langmuir-Blodgett (LB) film technique and an atomic force microscope (AFM). From surface pressure-area (π-A) isotherms, we have calculated the compression modulus. The results showed that hydrophobic Fe3O4 NPs enlarged the liquid-expanded (LE) and liquid-condensed (LC) phase of the mixed POPC/DPPC monolayers. The compressibility modulus of the mixed POPC/DPPC monolayer increases for hydrophilic Fe3O4 NPs, but the opposite happens for the hydrophobic Fe3O4 NPs. The adsorption of hydrophobic Fe3O4 NPs in mixed POPC/DPPC monolayers was much more than the hydrophilic Fe3O4 NPs. The interaction of hydrophilic Fe3O4 NPs with the head polar group of the mixed lipids increased the attraction force among the molecules, while the interaction of hydrophobic Fe3O4 NPs with the tail chain of the mixed lipids enhanced the repulsive force. The morphology of the monolayers was observed by AFM for validating the inferred results. This study is of great help for the application of Fe3O4 NPs in biological systems.

Studied on the dynamic adsorption process of Lycium barbarum polysaccharide in the POPC/DPPC monolayers.

In this study, the interaction between Lycium barbarum polysaccharide (LBP) and unsaturated 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) or saturated 1, 2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) was explored using the Langmuir films technique and atomic force microscopy (AFM). Comparing the pure lipid monolayer with the mixed monolayers, the π-A isotherms of the mixed monolayers shifted to larger molecular areas when LBP was added to the subphase. The compression modulus showed that the compressibility of the monolayer films decreased with the addition of LBP. Adsorption curves revealed that the variation in the surface pressure of LBP with POPC was larger than that with DPPC. This phenomenon was verified by the AFM images and the number of each lipid molecule combining with polysaccharide molecules in the mixed monolayer (Ap value), indicating that hydrophobic interactions between LBP and POPC are stronger than those of DPPC. These findings lay the foundation for exploring the pharmacological mechanism of LBP as an in vivo therapeutic.

Adsorption behavior of DNA on phosphatidylcholine at the air-water interface.

In this paper, the adsorption behavior of DNA on 1,2-dipalmitoyl-sn-glycero-3- phosphocholine (DPPC) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) mixed lipid monolayers had been studied at the air-water interface through the surface pressure-area curves (π-A), adsorption curves (π/π0-t), excess mean area (∆Aexc), excess Gibbs free energy (∆Gex) and the atomic force microscopy (AFM). π-A isotherms showed that the curves moved to larger mean molecular area after DNA added into subphase, however, the curves shifted to smaller mean molecular area when the concentration of DNA was higher than 1.2 µg/mL. The result of adsorption curves indicated that DNA molecules were spread by combining with polar head groups of lipids except the concentration of DNA was 0.4 µg/mL. ∆Aexc and ∆Gex demonstrated that DNA enlarged the interval between DPPC and POPC, and the strongest position happened at the concentration of DNA was 1.2 µg/mL. These phenomena might be the steric hindrance between DNA molecules. Morphology of surface observed by AFM was agreement with the results above, which verified our conclusion from a more intuitive aspect. This work provides useful theoretical basis for the development of novel DNA delivery materials.

Interaction of graphene oxide with bovine serum albumin: A fluorescence quenching study.

Fluorescence quenching was used to elucidate the binding interaction mechanism between bovine serum albumin (BSA) and graphene oxide (GO). By analyzing the values of Stern-Volmer quenching constant (KSV) and binding constant (KA) which were affected by temperature, we supposed that the quenching process between GO and BSA was mainly determined by static quenching, combined with dynamic quenching. The study of thermodynamics showed that the values of enthalpy change (∆H), entropy change (∆S) and Free Energy (∆G) were all negative, which implied that the weak interaction of the molecular between BSA and GO was Van der Waals interaction or hydrogen bond, and the quenching process was exothermic and spontaneous. The red shift in the synchronous fluorescence spectra suggested that the conformation of tryptophan was changed in the presence of GO. According to Förster's non-radiative energy transfer theory, the distance r between BSA (donor) and GO (acceptor) was calculated and indicated the occurrence of energy transfer from BSA to GO had high probability. The AFM observation and Raman spectroscopy revealed that the interaction between BSA and GO has occurred. Compared with other literatures, the explosion of surface topography about BSA and GO was paid more attention on in this study.

A Bioinspired, Highly Transparent Surface with Dry-Style Antifogging, Antifrosting, Antifouling, and Moisture Self-Cleaning Properties.

Transparent coatings with antireflection, antifogging, antifrosting, antifouling, and moisture self-cleaning properties can dramatically improve the efficiency and convenience of optical elements and thus are highly desirable for practical applications. Here, it is demonstrated that a bionic nanocone surface (BNS) fabricated by a facile, low-cost process consisting of template-assisted prepolymer curing followed by surface modification can possess the multiple functions listed above. The polymer coating firmly adheres to a glass substrate due to bonding agents. After SiO2 nanoparticle deposition and low-surface-energy fluorosilane modification, the coating shows low microdroplet adhesion. As a result, the as-prepared BNS exhibits a high transmittance when exposed to fog and good clarity even when the temperature decreases to -20 °C in a humid environment. Dipping the BNS into exemplified graphite powder has almost no influence on the transparency, and the BNS can realize self-cleaning of moisture when the surface is covered with a thick layer of man-made contaminants.

Influence of modified silica nanoparticles on phase behavior and structure properties of DPPC monolayers.

In this work, the effect of silica nanoparticles (NPs) adding to DPPC monolayer and the interaction between DPPC and silica nanoparticles are studied. Silica nanoparticles are prepared by microemulsion, meanwhile, DMDCS and APTES are used to modify silica NPs to get three types of modified silica NPs. These samples are mixed with DPPC to form mixed monolayer. By using the atomic force microscope (AFM), surface pressure-area and pressure-time isotherms, the effects of different hydrophilic-hydrophobic silica nanoparticles on the interface of lipid monolayer is analyzed. The data shows that the addition of silica nanoparticles changes the phase behavior, the collapse time and the structure of monolayer. Hydrophilic silica NPs decreases the collapse pressure and rigidity of DPPC monolayer, and makes monolayer collapse earlier since the steric hindrance leads to the resistance to compression, while hydrophobic silica NPs have less effect on monolayer in collapse pressure or rigidity but the texture of monolayer, and the addition of hydrophobic NPs causes the appearance of holes in the monolayer. We suppose that there are several possible locations of hydrophobic and hydrophilic silica nanoparticles in the air-water interface, which leads to different effects on the structure and rheological behavior of monolayer. This study can deepen the understanding on how nanoparticles affect human body since industries of nanoparticles on drug delivery, oil recovery and floatation are developing rapidly and getting more and more outside interest on a daily basis.

The interaction between BSA and DOTAP at the air-buffer interface.

In this article, the interaction between bovine serum albumin (BSA) and the cationic 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) at the air-buffer interface was investigated at different subphase's pH values (pH = 3, 5 and 10). Surface pressure measurements (π - A) and penetration kinetics process (π - t) were carried out to reveal the interaction mechanism and the dynamical behavior. The data showed that π - A isotherms moved towards larger mean molecular area when the concentration of BSA ([BSA]) increased, the amount of BSA adsorbed onto DOTAP monolayer reached a threshold value at a [BSA] of 5 × 10-8 M, and BSA desorbed from the lipid monolayer as time goes by. The results revealed that the association of BSA with DOTAP at the air-buffer interface was affected by the subphase's pH value. When pH = 10, the interaction mechanism between them was a combination of hydrophobic interaction and electrostatic attraction, so BSA molecules could be well separated and purified from complex mixtures. AFM images demonstrated that pH value and [BSA] could affect the morphology feature of DOTAP monolayer and the adsorption and desorption processes of BSA. So the study provides an important experimental basis and theoretical support for learning the interaction mechanism among biomolecules in separation and purification of biomolecules and biosensor.