有机磷酸酯改性钛表面的蛋白质吸附行为

通过磷酸三乙酯对钛表面进行改性,使表面含有机磷并且具有一定的疏水性。考察了不同初始浓度、温度和pH值条件下,小牛血清白蛋白（BSA）在钛表面的吸附行为,通过紫外分光光度计表征了BSA吸附的动力学特征。研究发现,在与含磷钛表面接触的前40 min内,BSA发生迅速吸附,随后逐渐达到动态平衡。根据Langmiur理论计算获得吸附等温线和最大吸附量。通过红外光谱和X射线光电子能谱分析表明BSA化学吸附到表面。对BSA在改性钛表面的吸附机制进行了初步的分析。      

Nanodiamond as the pH‐Responsive Vehicle for an Anticancer Drug

Cis‐dichlorodiammineplatinum(II) (CDDP, cisplatin), a widely used anticancer drug, is successfully loaded onto nanodiamond (ND) by adsorption and complexation. The CDDP–ND composite is characterized by IR spectroscopy, atomic absorption spectroscopy, thermogravimetric analysis, energy‐dispersive X‐ray spectroscopy, and X‐ray photoelectron spectroscopy. CDDP is released from the composite in phosphate‐buffered saline (PBS) of pH 6.0 at a rate higher than in PBS of pH 7.4. Therefore, it is predicted that the ND vehicle would deliver low concentrations of CDDP in the blood, but release much more drug after integration into the acidic cytoplasm, thereby reducing toxic side effects. The complexation between CDDP and the carboxyl groups on the ND surface is responsible for the pH‐responsive release property. The drug released from the composite retains the same cytotoxicity as free CDDP against human cervical cancer cells.     

Protein adsorption on citrate modified magnetic nanoparticles

Magnetic iron oxide nanoparticles were prepared by chemical co-precipitation method and then modified with sodium citrate. These iron oxide nanoparticles were characterized by transmission electron microscopy (TEM), X-ray diffractometer (XRD), and vibrating sample magnetometer (VSM). BSA was adsorbed on these citrate modified nanoparticles using two types of buffers (acetate buffer, pH 4.0, 4.7 and phosphate buffer, pH 7.4). The results showed that the maximum adsorption of BSA was 83 mg/g at its isoelectric point (pH 4.7). Fourier-transform infrared spectroscopy (FTIR) was used to confirm the attachment of citrate groups and BSA on the prepared magnetic nanoparticles. BSA was desorbed from nanoparticles under alkaline conditions, which was confirmed by SDS-PAGE electrophoresis, UV-vis and fluorescence spectra. The desorbed BSA showed small changes in its structure. The adsorption results indicated that BSA adsorption on citrate modified iron oxide nanoparticles occurred mainly by electrostatic mechanism.     

Probing Albumin Adsorption onto Calcium Phosphates by XPS and ToF-SIMS

In this study the binding and assembly of bovine serum albumin (BSA) onto three different calcium phosphate phases (hydroxyapatite, dibasic calcium phosphate dihydrate, and β-tricalcium phosphate) was investigated using a combination of X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). XPS was used to record adsorption isotherms and to quantify the amount of BSA adsorbed onto the different CaP surfaces. On all three surfaces a monolayer of adsorbed BSA was formed. ToF-SIMS was then used to investigate how the structure of BSA changes upon surface binding. ToF-SIMS data from BSA films on the three CaP surfaces showed intensity differences of secondary ions originating from both hydrophobic and hydrophilic amino acids. For a more quantitative examination of structural changes, we developed a ratio comparing the sum of intensities of secondary ions from hydrophobic and hydrophilic residues. A small, but statistically significant, increase in the value of this ratio (7%) was observed between a BSA film on hydroxyapatite versus dibasic calcium phosphate dihydrate. From this ratio we can make some initial hypotheses about what specific changes in BSA structure relate to these differences observed in the ToF-SIMS data.     

Interaction of malachite green with bovine serum albumin: determination of the binding mechanism and binding site by spectroscopic methods

The interaction between malachite green (MG) and bovine serum albumin (BSA) under simulative physiological conditions was investigated by the methods of fluorescence spectroscopy, UV-vis absorption and circular dichroism (CD) spectroscopy. Fluorescence data showed that the fluorescence quenching of BSA by MG was the result of the formation of the MG-BSA complex. According to the modified Stern-Volmer equation, the effective quenching constants (K(a)) between MG and BSA at four different temperatures were obtained to be 3.734 x 10(4), 3.264 x 10(4), 2.718 x 10(4), and 2.164 x 10(4)L mol(-1), respectively. The enthalpy change (Delta H) and entropy change (DeltaS) were calculated to be -27.25 kJ mol(-1) and -11.23 J mol(-1)K(-1), indicating that van der Waals force and hydrogen bonds were the dominant intermolecular force in stabilizing the complex. Site marker competitive experiments indicated that the binding of MG to BSA primarily took place in sub-domain IIA. The binding distance (r) between MG and the tryptophan residue of BSA was obtained to be 4.79 nm according to F?rster theory of non-radioactive energy transfer. The conformational investigation showed that the presence of MG decreased the alpha-helical content of BSA (from 62.6% to 55.6%) and induced the slight unfolding of the polypeptides of protein, which confirmed some micro-environmental and conformational changes of BSA molecules.     

Competitive adsorption of bovine serum albumin and lysozyme on characterized calcium phosphates by polyacrylamide gel electrophoresis method

Characterizations of hydroxyapatite (HA), biphasic calcium phosphate (BCP) and beta tricalcium phosphate (β-TCP) ceramic particles were carried out using X-ray diffusion (XRD), Scanning electron micrograph (SEM), Particle Sizer and Zeta potential analyzer. Competitive adsorption of bovine serum albumin (BSA) and lysozyme (LSZ) on the three calcium phosphates were investigated by polyacrylamide gel electrophoresis (PAGE) method. The results showed that HA, BCP and β-TCP ceramic particles with irregular shapes and similar size distributions all had negative surface net charges in pH7.4 phosphate buffered saline (PBS) solution and exhibited alike behaviors of BSA and LSZ adsorption. LSZ had higher affinity for calcium phosphate ceramics than BSA and its adsorption on them didn’t be almost influenced by the increasing of BSA concentration in the solution. Electrostatic interaction played an important role on the competitive adsorption of BSA and LSZ on the surface of calcium phosphate ceramic particles.     

Adsorption profile of lead on Aspergillus versicolor: a mechanistic probing

The adsorption of lead on Aspergillus versicolor biomass (AVB) has been investigated in aqueous solution with special reference to binding mechanism in order to explore the possibilities of the biomass to address environmental pollution. AVB, being the most potent of all the fungal biomasses tested, has been successfully employed for reducing the lead content of the effluents of battery industries to permissible limit (1.0 mg L(-1)) before discharging into waterbodies. The results establish that 1.0 g of the biomass adsorbs 45.0 mg of lead and the adsorption process is found to depend on the pH of the solution with an optimum at pH 5.0. The rate of adsorption of lead by AVB is very fast initially attaining equilibrium within 3h following pseudo second order rate model. The adsorption process can better be described by Redlich-Peterson isotherm model compared to other ones tested. Scanning electron micrograph demonstrates conspicuous changes in the surface morphology of the biomass as a result of lead adsorption. Zeta potential values, chemical modification of the functional groups and Fourier transform infrared spectroscopy reveal that binding of lead on AVB occurs through complexation as well as electrostatic interaction.     

Dynamic Adsorption of Albumin on Nanostructured TiO(2)Thin Films

Spectroscopic ellipsometry was used to characterize the optical properties of thin (<5 nm) films of nanostructured titanium dioxide (TiO(2)). These films were then used to investigate the dynamic adsorption of bovine serum albumin (BSA, a model protein), as a function of protein concentration, pH, and ionic strength. Experimental results were analyzed by an optical model and revealed that hydrophobic interactions were the main driving force behind the adsorption process, resulting in up to 3.5 mg/m(2) of albumin adsorbed to nanostructured TiO(2). The measured thickness of the adsorbed BSA layer (less than 4 nm) supports the possibility that spreading of the protein molecules on the material surface occurred. Conformational changes of adsorbed proteins are important because they may subsequently lead to either accessibility or inaccessibility of bioactive sites which are ligands for cell interaction and function relevant to physiology and pathology.     

Encapsulation of albumin in self-assembled layer-by-layer microcapsules: comparison of co-precipitation and adsorption techniques

Objective: The objective of this study is to prepare and characterize polymeric self-assembled layer-by-layer microcapsules (LbL-MC) to deliver a model protein, bovine serum albumin (BSA). The aim is to compare the BSA encapsulation in LbL-MC using co-precipitation and adsorption methods.

Materials and methods: In co-precipitation method, BSA was co-precipitated with growing calcium carbonate particles to form a core template. Later, poly(styrene sulfonate) and poly(allylamine hydrochloride) were sequentially adsorbed onto the CaCO₃ templates. In adsorption method, preformed LbL-MC were incubated with BSA and encapsulation efficiency is optimized for pH and salt concentration. Free and BSA-encapsulated LbL-MC were characterized using Zetasizer, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy and differential scanning calorimeter. Later, in vitro release studies were performed using dialysis membrane method at pH 4, 7.4 and 9.

Results and discussion: Results from Zetasizer and SEM showed free LbL-MC with an average size and zeta-potential of 2.0?±?0.6?μm and 8.1?±?1.9?mV, respectively. Zeta-potential of BSA-loaded LbL-MC was (–)7.4?±?0.7?mV and (–)5.7?±?1.0?mV for co-precipitation and adsorption methods, respectively. In adsorption method, BSA encapsulation in LbL-MC was found to be greater at pH 6.0 and 0.2?M NaCl. Co-precipitation method provided four-fold greater encapsulation efficiency (%) of BSA in LbL-MC compared with adsorption method. At pH 4, the BSA release from LbL-MC was extended up to 120?h. Polyacrylamide gel electrophoresis showed that BSA encapsulated in LBL-MC through co-precipitation is stable toward trypsin treatment.

Conclusion: In conclusion, co-precipitation method provided greater encapsulation of BSA in LbL-MC. Furthermore, LbL-MC can be developed as carriers for pH-controlled protein delivery.     

Preliminary study of adsorption behavior of bovine serum albumin(BSA) protein and its effect on antibacterial and corrosion property of Ti-3Cu alloy

The adsorption behavior,antibacterial,and corrosion properties of a Ti-3Cu alloy were studied in a phosphate-buffered saline solution containing 0,1,3,and 6 g L-1 bovine serum albumin protein at 37 ℃and pH =7.4 (±0.2).The protein adsorption behavior was examined via cyclic voltammetry,secondary ions mass spectroscopy (SIMS),and angle-resolved X-ray photoelectron spectroscopy (ARXPS).The cor-rosion property was analyzed by the open circuit potential (OCP),potentiodynamic polarization (PD),and electrochemical impedance spectroscopy (EIS) examinations.The antibacterial test was conducted according to the GB/T 21510 China Standard.It was observed that the surface charge density (Q～s) was directly proportional to the amount of the adsorbed BSA protein,signifying that the protein adsorption was accompanied by the charge transfer,pointing to chemisorptions phenomena.BSA amino groups and other organic species were observed in the surface analysis examinations.It was shown that the formation of barrier complexes between the TiO2 oxide-layer and PBS solution resulted in decreasing the release of Cu-ions,which consequently reduced the antibacterial activity.On the other hand,these barrier complexes improved the corrosion resistance by increasing the charge transfer resistance and double-layer capacitance of the Ti-3Cu alloy.     

The interfacial behaviour of single poly(N,N-dimethylacrylamide) chains as a function of pH

We have studied the pH-dependent conformational behaviour of poly(N,N-dimethylacrylamide) (PDMAc) at silicon and gold surfaces using single-molecule force spectroscopy and a quartz crystal microbalance (QCM). Despite the pH dependence, nuclear magnetic resonance and titration experiments demonstrate that PDMAc is not a weak polybase. The interaction between single chains and a silicon surface (with native oxide layer intact) in aqueous solution was investigated using force spectroscopy. Single-molecule force measurements were performed using thiol-functionalized PDMAc and gold-coated AFM cantilevers. The forces of interaction between PDMAc and the native oxide-coated silicon surface vary with the pH. The shape of the retraction curve for low pH solution includes a greater number of 'train' conformations, which suggests a stronger interaction with the surface relative to the surrounding media at low pH. The adsorption behaviour of PDMAc, from liquid onto silicon surfaces, was monitored using a QCM, which shows greater PDMAc adsorption onto silicon at low pH. The force spectroscopy and QCM investigations confirm that the PDMAc chain is more extended and stiffer in low pH solution. We attribute the pH-dependent behaviour to an increased number of hydrogen bonding sites on the silicon surface at low pH.     

Study on the Modification of Nanodiamond with DN-IO

Fourier transform infrared spectroscopy （FT-IR） and ζ-potential were introduced to study the effect of different modification parameters on the surface properties of nanodiamond （ND）. Results showed that under stirring grinding grinding conditions, ND hard aggregates were smashed and some active spots on them reacted with surfactant molecules, which led to the increase in its ζ-potential and stability. Different models of surface modification were also given in this study.     

Studies on the formation of Langmuir monolayer and Langmuir–Blodgett films of octadecyl amine-bromocresol purple dye complex

Properties of the monolayer of octadecyl amine (ODA) molecules on aqueous solution of bromocresol purple (Bcp) dye have been studied over a wide range of pH by measuring the surface pressure-area isotherms. A strong interaction of ODA molecule was observed with the dye molecule in the pH range of 4–9. Under the present study, the dye molecules were adsorbed on the ODA monolayer at the water surface and subsequently a Langmuir–Blodgett (LB) film of ODA–dye complex was transferred from the air–water interface onto a solid substrate. Alternatively, dye molecules were incorporated into LB film by immersing the predeposited LB film of pure ODA into the dye solution, i.e. by adsorption of dye molecule at the solid–liquid interface. The adsorption behavior of ODA–Bcp dye complexes obtained through these two different routes was characterised with the help of UV–Visible spectroscopy. The nature of the ODA–dye complex deposited from air–water interface using the LB technique was found to be quite different from that of the complex formed by the adsorption of the dye into the pure ODA LB film. The adsorption spectra of the ODA–dye complex obtained from the air–water interface did not change with pH, while those of the ODA–dye complex formed from the solid–liquid interface showed pH dependence.     

Self-assembled monolayer of carboxyl-terminated poly(amido amine) dendrimer

Adlayer formation and adsorption structure of 2.5th-generation poly(amido amine) dendrimer with carboxyl-terminated groups on solid substrates were investigated by atomic force microscopy, surface plasmon resonance spectroscopy, and surface enhanced infrared absorption spectroscopy. Dendrimer molecules are not uniformly adsorbed on solid surface but form aggregates with a width of approximately 100 nm and a height less than 1 nm. Adsorption reaches in equilibrium at 100-1000 sec, depending on the dendrimer concentration. The adsorption-desorption process is considerably reproducible and repeatable. Although the adsorption at equilibrium increases with dendrimer concentration and reaches maximum at neutral pH, monolayer is always maintained after the desorption with solvent. This indicates the formation of self-assembled monolayer. Such monolayer is preserved even at the variation of pH. Although most carboxylates are protonated at acidic pH, small amount of carboxylate remains even at acidic pH. The adsorption structure of dendrimer was illustrated.     

Characterization of surfactant coatings in capillary electrophoresis by atomic force microscopy

This paper describes the adsorption mechanisms and aggregation properties of cetyltrimethylammonium bromide (CTAB) and didodecyldimethylammonium bromide (DDAB) surfactants that are used for dynamic coatings in capillary electrophoresis (CE). Atomic force microscopy is used to directly visualize surfactant adsorption on fused silica. It was found that the single-chained surfactant CTAB forms spherical aggregates on silica while the double-chained surfactant DDAB forms a bilayer. Aggregation at the surface occurs at approximately the same surfactant concentration in which EOF reversal is observed in CE. The nearest-neighbor distance between CTAB aggregates varies inversely with buffer pH and becomes constant at the point when the silanol groups are fully ionized. DDAB forms a flat, uniform coating independent of pH. Increasing the buffer ionic strength changes the morphology of the CTAB aggregates from spherical to cylindrical. The change in morphology can alter the surface coverage, which is related to the "normalized" EOF measured in identical buffers. The morphology of a surfactant coating is also shown to affect its ability to inhibit protein adsorption to the capillary wall. Specifically, the full surface coverage provided by DDAB proved superior in a head-to-head comparison with CTAB.     

四(4-磺酸苯基)-卟啉在聚4-乙烯基吡啶接枝的乙烯-乙烯醇膜表面的吸附和自组装行为

四(4-磺酸苯基)-卟啉(TPPS)是一种水溶性卟啉,在一定条件下可以自组装形成超分子聚集体,将这种超分子聚集体与膜材料相结合,可以形成超分子负载膜。文中以乙烯-乙烯醇共聚物(EVAL)为膜材料,4-乙烯基吡啶(4VP)为单体,采用紫外辐照表面接枝法制备了表面带有P4VP接枝链的EVAL-P4VP接枝膜,利用非共价键作用将TPPS负载于EVAL原膜及EVAL-P4VP接枝膜上,研究了p H值、离子强度、接枝率等因素对TPPS吸附过程以及TPPS在膜表面存在形态和自组装行为的影响。结果表明,TPPS溶液中自身聚集及离子强度的增加对其在膜上的吸附产生不利影响;吸附过程可用Langmuir等温吸附模型进行描述;接枝率的增加、p H值的减小和吸附量的增加有利于TPPS在接枝膜表面形成J-聚集体。     

Chemical reactivity of mineral aggregates in aqueous solution: relationship with bitumen emulsion breaking

This paper reports a study on chemical reactivity of gneiss, diorite and limestone aggregates in aqueous solution. The originality of this study is that it extended to very short times (less than 1440 min). Rise in pH tests was implemented and dissolution kinetics was analysed. The results showed that calcium was the major element released by the aggregates. It has also been found that dissolution had an influence on the final morphology of aggregates. Polyamine emulsifier adsorption onto aggregates has been assessed using electrophoresis. Finally, the rise in pH and electrophoretic tests were compared to the breaking test traditionally performed to characterise bitumen emulsions. It was found that breaking values were controlled by both the surface area and the surface charge of the particles. Results may be correlated to polyamine adsorption on aggregates. Adsorption seemed to be efficient for gneiss and diorite: at pH 2, their charge turned from slightly negative to highly positive. At this pH value, limestone particles were dissolved and polyamine adsorption must be less efficient than with gneiss and diorite, for which the emulsion breaking was facilitated by the high attraction of particles for the emulsifier, due to their negative surface charge.     

In Vitro Adsorption-Desorption of Papaverine Hydrochloride by Montmorillonite

Abstract

In an attempt to obtain the basic data necessary in research into the possible use of papaverine in sustained action formulas in the form of complexes with Montmorillonite, the “in vitro” adsorption and desorption of the drug as a function of different factor was studied.

The study of the interaction and adsorption mechanisms was carried out by adsorption isotherms, X-ray diffraction and I.R. spectroscopy.

The adsorption of papaverine by Montmorillonite increases with the rise in pH of the solution, within the pH range studied (2-4) in agreement with the solubility of the compound. According to the isotherms, adsorption increases with the concentration of the solution up to 79.16 mEq/100 g (very close to the exchange capacity of the clay). The data fulfill Langmuir's equation, implying a chemical adsorption mechanism.

The results of the X-ray diffraction and I.R. spectroscopy studies confirm the intercalation of the organic cation into the interlayer space of montmorillonite, forming a complex of defined spacing (17.66 Å (DL = 8.06 Å)). The studies revealed that cation exchange is the mechanism responsible for this interaction.

The “in vitro” desorption studies showed that the amount of papaverine desorbed from the complex depends on the pH of the solution, on its ionic strength, on the presence of free drug and on the elimination rate of the desorbed complex; in all cases, desorption was seen to be very low.

In general, release of the drug follows a single first order kinetic process with a rapid initial desorption of the drug.     

Probing Adsorption Behaviors of BSA onto Chiral Surfaces of Nanoparticles

Chiral properties of nanoscale materials are of importance as they dominate interactions with proteins in physiological environments; however, they have rarely been investigated. In this study, a systematic investigation is conducted for the adsorption behaviors of bovine serum albumin (BSA) onto the chiral surfaces of gold nanoparticles (AuNPs), involving multiple techniques and molecular dynamic (MD) simulation. The adsorption of BSA onto both L‐ and D‐chiral surfaces of AuNPs shows discernible differences involving thermodynamics, adsorption orientation, exposed charges, and affinity. As a powerful supplement, MD simulation provides a molecular‐level understanding of protein adsorption onto nanochiral surfaces. Salt bridge interaction is proposed as a major driving force at protein–nanochiral interface interaction. The spatial distribution features of functional groups (? COO^?, ? NH₃⁺, and ? CH₃) of chiral molecules on the nanosurface play a key role in the formation and location of salt bridges, which determine the BSA adsorption orientation and binding strength to chiral surfaces. Sequentially, BSA corona coated on nanochiral surfaces affects their uptake by cells. The results enhance the understanding of protein corona, which are important for biological effects of nanochirality in living organisms.     

Sonochemical synthesis of (3-aminopropyl)triethoxysilane-modified monodispersed silica nanoparticles for protein immobilization

3-Aminopropyltriethoxysilane modified monodispersed silica nanoparticles were synthesized by a rapid sonochemical co-condensation synthesis procedure. The chemical nature of surface organic modifier on the obtained modified silica nanoparticle was characterized by ¹³C and ²⁹Si MAS Nuclear Magnetic Resonance (NMR) spectroscopies, Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA)- differential scanning calorimetry (DSC). Due to the strengthened positive surface charge of the silica nanoparticles by the modification with aminopropyl groups, the capability for bovine serum albumin (BSA) adsorption was significantly increased as compared with bare silica nanoparticles. 80 mg/g BSA was adsorbed on modified silica nanoparticles, whereas only 20 mg/g BSA could be loaded on pure silica nanoparticles. The enhanced positive surface charge repelled proteins with net positive charge and the modified silica nanoparticles exhibited negligible adsorption of lysozyme, thus a selective adsorption of proteins could be achieved.