Function Of Hydrophobicity Research Articles

Affinity-controlled protein encapsulation into sub-30nm telodendrimer nanocarriers by multivalent and synergistic interactions.

Novel nanocarriers are highly demanded for the delivery of heterogeneous protein therapeutics for disease treatments. Conventional nanoparticles for protein delivery are mostly based on the diffusion-limiting mechanisms, e.g., physical trapping and entanglement. We develop herein a novel linear-dendritic copolymer (named telodendrimer) nanocarrier for efficient protein delivery by affinitive coating. This affinity-controlled encapsulation strategy provides nanoformulations with a small particle size (<30nm), superior loading capacity (>50% w/w) and maintained protein bioactivity. We integrate multivalent electrostatic and hydrophobic functionalities synergistically into the well-defined telodendrimer scaffold to fine-tune protein binding affinity and delivery properties. The ion strength and density of the charged groups as well as the structure of the hydrophobic segments are important and their combinations in telodendrimers are crucial for efficient protein encapsulation. We have conducted a series of studies to understand the mechanism and kinetic process of the protein loading and release, utilizing electrophoresis, isothermal titration calorimetry, Förster resonance energy transfer spectroscopy, bio-layer interferometry and computational methods. The optimized nanocarriers are able to deliver cell-impermeable therapeutic protein intracellularly to kill cancer cells efficiently. Invivo imaging studies revealed cargo proteins preferentially accumulate in subcutaneous tumors and retention of peptide therapeutics is improved in an orthotopic brain tumor, these properties are evidence of the improved pharmacokinetics and biodistributions of protein therapeutics delivered by telodendrimer nanoparticles. This study presents a bottom-up strategy to rationally design and fabricate versatile nanocarriers for encapsulation and delivery of proteins for numerous applications.

The Utilization of Hydrophobic Coatings on Insulative Skirts to Galvanically Decouple Mechanically-Fastened Aluminum Alloy and Carbon-Fiber Reinforced Polymer-Matrix Composites

In a quest to reduce weight and improve performance, aluminum (Al) alloys have been used in conjunction with lightweight materials such as carbon-fiber reinforced (CFR) polymer-matrix composites (PMCs). The mechanical contact of CFR PMCs (which serves as cathode) with Al alloys (which serves as anode) can result in galvanic corrosion of the Al alloys in a corrosive environment. The major objective of this research was on devising corrosion control strategies for couples of 6061-T6 Al that were mechanically fastened to CFR PMCs using Ti-6Al-4V bolts. A typical method used to mitigate galvanic corrosion when bolting Al to CFR PMCs is to insert an insulating layer (G-10 fiberglass or E-glass–reinforced PMC) between the members. Although the direct contact between the aluminum and CFR PMC is eliminated, the aluminum and the CFR PMC are still galvanically coupled through the Ti fastener, and galvanic corrosion on Al will occur if the electrolyte bridges over the insulating layer. Galvanic corrosion can be mitigated by increasing the IR loss across the skirt, which can be achieved by lengthening the skirt or breaking up the continuity of the salt bridge that forms on the skirt. The continuity of the salt bridge can be disrupted by applying hydrophobic coatings on the insulative skirt. In this study, galvanic corrosion rates were monitored for 6061-T6 Al—CFR PMC couples (with insulating skirts) subjected to the following conditions: 1) Insulting skirts having coatings (silane-based coating, epoxy, polyurethane, or latex) of various levels of hydrophobicity 2) Salt solutions of various concentrations (0, 10, 100, 1000, 10000, and 20000 ppm of chlorides) 3) Various insulating skirt lengths (0.25 inch or 0.5 inch), 4) Various exposure conditions (controlled humidity laboratory exposure, outdoor exposure with sheltered and unsheltered conditions). The effect on galvanic corrosion by the different coatings was studied as a function of hydrophobicity, as determined by the contact angle for wetting. The contact angle was measured on the coating surface before and after exposure to the outdoor test sites to study the effects of environmental degradation on hydrophobicity. The degradation of the coatings was also studied using other techniques such as Raman spectroscopy. The ingress of environmental constituents (i.e., chlorides, sodium ions, etc.,) towards the anode and cathode surfaces was analyzed using scanning electron microscopy (SEM) and energy dispersive-X-ray analysis (EDXA).

The development of antibacterial and hydrophobic functionalities in natural fibers for fiber-reinforced composite materials

Green surface modification of coconut fibers was performed using laccase biografting of eugenol for the development of antibacterial functionalities and fiber-reinforced polymer composites. Fourier transform infrared analysis, X-ray diffraction and surface morphology of grafted fibers were utilized to confirm the biografting of eugenol. Antibacterial, hydrophobicity and thermal properties were evaluated by colony forming unit (CFU) method, moisture absorption and thermogravimetric analysis, respectively. The grafted surfaces were found to be antibacterial, hydrophobic and thermally more stable. Grafted fibers were reinforced in a poly(butylene succinate) matrix to improve the mechanical properties of the biocomposites. The mechanical properties were improved even with a low content of biografted coconut fibers.

Selective agglomeration of fine coal using a water-in-oil emulsion

Fine coal may be separated from an aqueous suspension of coal and mineral particles through the application of a pure oil. The pure oil preferentially wets and agglomerates only the coal, forming a high quality, granular product. However, the use of the pure oil also comes at a relatively high cost and this cost prohibits commercial implementation of this process. In this work a new, economic binder, was introduced. This binder consisted of a high internal phase water-in-oil emulsion which was 95vol% water and 5vol% organic. This type of binder was selected as it possessed the hydrophobic surface functionality of oil while the space filling functionality of the binder was primarily satisfied by the dispersed water droplets within the emulsion. The application of this emulsion in the agglomeration process led to a 10-fold reduction in the organic liquid dosage required to achieve agglomeration as compared a pure oil binder. It was also observed that the agglomeration time required when using the emulsion binder was one order of magnitude less than required when using a pure oil binder. This variation was considered to result from the five orders of magnitude difference in the viscosity of the two binders.

Energetics of Transport through the Nuclear Pore Complex.

Molecular transport across the nuclear envelope in eukaryotic cells is solely controlled by the nuclear pore complex (NPC). The NPC provides two types of nucleocytoplasmic transport: passive diffusion of small molecules and active chaperon-mediated translocation of large molecules. It has been shown that the interaction between intrinsically disordered proteins that line the central channel of the NPC and the transporting cargoes is the determining factor, but the exact mechanism of transport is yet unknown. Here, we use coarse-grained molecular dynamics simulations to quantify the energy barrier that has to be overcome for molecules to pass through the NPC. We focus on two aspects of transport. First, the passive transport of model cargo molecules with different sizes is studied and the size selectivity feature of the NPC is investigated. Our results show that the transport probability of cargoes is significantly reduced when they are larger than ∼5 nm in diameter. Secondly, we show that incorporating hydrophobic binding spots on the surface of the cargo effectively decreases the energy barrier of the pore. Finally, a simple transport model is proposed which characterizes the energy barrier of the NPC as a function of diameter and hydrophobicity of the transporting particles.

Hydrophobic perfluoro-silane functionalization of porous silicon photoluminescent films and particles

Luminescent structures based on semiconductor quantum dots (QDs) are increasingly used in biomolecular assays, cell tracking systems, and in-vivo diagnostics devices. In this work we have carried out the functionalization of porous silicon (PSi) luminescent structures by a perfluorosilane (Perfluoro-octyltriethoxysilane, PFOS) self assembly. The PFOS surface binding (traced by X-ray photoelectron spectroscopy) and photoluminescence efficiency were analyzed on flat model PSi. Maximal photoluminescence intensity was obtained from PSi layers anodized at 110mA/cm2. Resistance to hydroxylation was assayed in H2O2:ethanol solutions and evidenced by water contact angle (WCA) measurements. PFOS-functionalized PSi presented systematically higher WCA than untreated PSi. The PFOS functionalization was found to slightly improve the aging of the PSi particles in water giving rise to particles with longer luminescent life. Confirmation of PFOS binding to PSi particles was derived from FTIR spectra and the preservation of luminescence was observed by fluorescence microscopy. Such functionalization opens the possibility of promoting hydrophobic-hydrophobic interactions between biomolecules and fluorescent QD structures, which may enlarge their biomedical applications catalogue.

Fluorescence properties of dissolved organic matter as a function of hydrophobicity and molecular weight: case studies from two membrane bioreactors and an oxidation ditch

This study explores possible linkages between the fluorescence properties and hydrophobicity/molecular weight of dissolved organic matter, through case studies from three wastewater treatment plants.

Strong Surface Treatment Effects on Reinforcement Efficiency in Biocomposites Based on Cellulose Nanocrystals in Poly(vinyl acetate) Matrix.

In this work, the problem to disperse cellulose nanocrystals (CNC) in hydrophobic polymer matrices has been addressed through application of an environmentally friendly chemical modification approach inspired by clay chemistry. The objective is to compare the effects of unmodified CNC and modified CNC (modCNC) reinforcement, where degree of CNC dispersion is of interest. Hydrophobic functionalization made it possible to disperse wood-based modCNC in organic solvent and cast well-dispersed nanocomposite films of poly(vinyl acetate) (PVAc) with 1-20 wt % CNC. Composite films were studied by infrared spectroscopy (FT-IR), UV-vis spectroscopy, dynamic mechanical thermal analysis (DMTA), tensile testing, and field-emission scanning electron microscopy (FE-SEM). Strongly increased mechanical properties were observed for modCNC nanocomposites. The reinforcement efficiency was much lower in unmodified CNC composites, and specific mechanisms causing the differences are discussed.

Electrospun Ultrafine Fiber Composites Containing Fumed Silica: From Solution Rheology to Materials with Tunable Wetting.

Fumed silica (FS) particles with hydrophobic (R805) or hydrophilic (A150) surface functionalities are incorporated in polyacrylonitrile (PAN) fibers by electrospinning to produce mats with controlled wettability. Rheological measurements are conducted to elucidate the particle-polymer interactions and characterize the system while microscopic and analytic tools are used to examine FS location within both fibers and films to aid in the fundamental understanding of wetting behavior. Unlike traditional polymers, we find these systems to be gel-like, yet electrospinnable; the fumed silica networks break down into smaller aggregates during the electrospinning process and disperse both within and on the surface of the fibers. Composite nanofiber mats containing R805 FS exhibit an apparent contact angle over 130° and remain hydrophobic over 30 min, while similar mats with A150 display rapid surface-wetting with a static contact angle of ∼30°. Wicking experiments reveal that the water absorption properties can be further manipulated, with R805 FS-impregnated mats taking up only 8% water relative to mat weight in 15 min. In contrast, PAN fibers containing A150 FS absorb 425% of water in the same period, even more than the pure PAN fiber (371%). The vastly different responses to water demonstrate the versatility of FS in surface modification, especially for submicron fibrous mats. The role of fumed silica in controlling wettability is discussed in terms of their surface functionality, placement on nanofibers and induced surface roughness.

Effect of Micellization on the Thermoresponsive Behavior of Polymeric Assemblies.

The chain density of polymer micelles, dictated by their aggregation number (Nagg), is an often overlooked parameter that governs the macroscopic behavior of responsive assemblies. Using a combination of variable-temperature light scattering, turbidimetry, and microcalorimetry experiments, the cloud point and thermal collapse of micellar poly(N-isopropylacrylamide) (pNIPAM) corona chains at lower temperatures than the cloud point were found to be largely independent of the micelle's Nagg. By controlling the core composition, the degree of hysteresis associated with the thermal transition was found to increase as a function of core hydrophobicity. We performed this study on well-characterized micelles with tunable Nagg values, composed of a thermoresponsive corona (pNIPAM) and a nonresponsive core block poly(n-butyl acrylate-co-N,N-dimethylacrylamide) (p(nBA-co-DMA)), which were synthesized using reversible addition-fragmentation chain transfer (RAFT) polymerization. This allowed for a distinction to be made between thermoresponsive behavior at both the molecular and macroscopic level. The study of the subtle differences between these behaviors was made possible using a combination of complementary techniques. These results highlight the critical need for consideration of the effect that self-assembly plays on the responsive behavior of polymer chains when compared with free unimers in solution.

Click chemistry-based synthesis of water-dispersible hydrophobic magnetic nanoparticles for use in solid phase extraction of non-steroidal anti-inflammatory drugs

Magnetic nanoparticles (MNPs), prepared via thiol-ene click chemistry and containing both diol and octadecyl groups, are shown to possess both hydrophobic and hydrophilic functionalities. They display excellent dispersibility in water and also are capable of extracting non-steroidal anti-inflammatory drugs (NSAIDs) from water samples. The MNPs can be magnetically separated, and the NSAIDs eluted with acetonitrile-water (9:1, v:v) and submitted to high performance liquid chromatographic analysis. Extraction variables, such as the kind of ion-pairing reagents, amount of MNPs, pH of sample solution, extraction and desorption time, volume of desorption solvent and salt addition, were optimized. Under optimum conditions, the method has a wide analytical range (from 5 to 800 ng∙mL‾1), good reproducibility with intra-day and inter-day relative standard deviations of <19.2 % (for n = 6), and low detection limits of 0.32 to 1.44 ng∙mL‾1 for water samples. The results demonstrate that the material possesses good water compatibility, thus warranting ease of operation and good reproducibility.

Modeling confinement in polymer nanocomposites from linear viscoelasticity data

The ability of the time-dependent diffusion–double-reptation (TDD-DR) theory to predict the molecular structure and dynamics of polymer nanocomposites is investigated for poly(butylene succinate) blended with fumed silica particles with contrasting surface treatments (unmodified and modified with silanes). Structural and dynamic parameters such as confined polymer fraction (ϕ s) and relaxation time are extracted from fitting the experimental curves for relaxation modulus G(t) by the TDD-DR model with fluctuation effects included. A good fit of experimental data over seven time decades is obtained after modification of the TDD-DR model to account for Rouse relaxation on the short time scale. The fraction of confined polymer extracted from model fitting is in quantitative agreement with the value obtained from the specific reversing heat capacity for poly(butylene succinate) (PBS)/fumed silica nanocomposites. Based on parameters deduced from rheological data, we study the influence of surface functionality on the microstructure of polymer matrix. We conclude that increasing the polymer–particle compatibility through introduction of a hydrophobic functionality on the surface of the particles results in increased amount of confined PBS chains and strong immobilization of the PBS molecules. These interface effects are discussed for the first time in terms of TDD-DR model that takes into account the dynamics of bound polymer chains, allowing prediction of the universal nature of the confinement effect and its role in polymer nanocomposite processing and bulk physical properties.

Solid-Phase Synthesis, Hybridizing Ability, Uptake, and Nuclease Resistant Profiles of Position-Selective Cationic and Hydrophobic Phosphotriester Oligonucleotides.

Analogues of oligonucleotides and mononucleotides with hydrophobic and/or cationic phophotriester functionalities often generate an improvement in target affinity and cellular uptake. Here we report the synthesis of phosphotriester oligodeoxyribonucleotides (ODNs) that are stable to the conditions used for their preparation. The method has been demonstrated by introducing phosphoramidite synthons where N-benzyloxycarbonyl (Z) protected amino alcohols replace the cyanoethyl group. After synthesis these ODNs were found to be stable to the condition required to remove base labile protecting groups and the ODNs from the solid support. Moreover the use of 1-(4,4-dimethyl-2, 6-dioxocyclohex-1-ylidene) ethyl (Dde) in place of Z protection on the amino alcohol has allowed us to introduce cationic aminoethyl phosphotriester modifications into ODNs. Melting temperatures of duplexes containing cationic or hydrophobic Z modified ODNs indicate that the backbone-phosphotriester modifications minimally affect duplex stability. Nuclease stability assays demonstrate that these phosphotriesters are resistant toward 5'- and 3'-exonucleases. Fluorescently labeled 23-mer ODNs modified with four cationic or hydrophobic Z phosphotriester linkages show efficient cellular uptake during passive transfection in HeLa and Jurkat cells.

Effect of Hydrophilic Treatment of Cathode Channel on Liquid Water Transport through Gas Diffusion Layer and Performance of PEFC

Water flooding and plugging on cathode side of polymer electrolyte fuel cells (PEFCs) lead to severe concentration overpotential due to oxygen transport limitation. To alleviate these issues, it is necessary to elucidate liquid water transport through cathode gas diffusion layer (GDL) and design the optimum structure of GDL and gas channel. In the previous works, many experimental efforts to visualize two-phase flow in operating PEFCs have been carried out by neutron [1], X-ray [2] and optical [3] techniques. However, most of the conventional visualization studies investigated only the water behavior along the flow direction of a PEFC. The through-plane behaviors of liquid droplets inside the cathode channel, including the emergence, growth and coalescence of droplets on the GDL surface and the attachment to the channel sidewall, cannot be exactly grasped. Turhan et al. [4] analyzed the through-plane liquid storage, transport and flooding mechanism as a function of channel wall hydrophobicity with the use of high-resolution neutron imaging. Results revealed that the channel wettability significantly affects the water transport from the diffusion media to the gas flow channels. Hydrophilic channel walls enhance the liquid water suction from under-the-land locations into the channels. In this study, the dynamic behaviors of liquid droplets inside the cathode channel are directly observed using a cross-sectional visualization cell, and the effect of hydrophilic treatment of cathode channel on the water transport through the GDL and the cell performance is investigated under operating conditions. The cross-sectional visualization technique is very useful to evaluate the growth and attachment behaviors of liquid droplets and the channel blockage owing to liquid water in the gas channel. In the experiment, the cell voltage and differential pressure between the cathode inlet and outlet are simultaneously measured, and the correlation between the liquid water behavior and the performance characteristics is discussed. Fig. 1 presents the time-series variation of the cell voltage and differential pressure of an operating PEFC for two different wettabilities of cathode channel wall. The contact angles of water of uncoated and hydrophilized channels are 76o and 17o, respectively. The fuel cell operation is performed at 0.5 A/cm2 for 1000 s. In the case of uncoated channel, the cell voltage remarkably decreases for the first 350 s at low air stoichiometry, because water flooding proceeds inside the cathode catalyst layer (CL) and GDL. Subsequently, both the voltage and pressure frequently fluctuate due to water plugging in the channels. On the other hand, the hydrophilic treatment of the cathode channels reduces the voltage drop due to flooding. Water droplets emerged from the GDL surface immediately attach to the hydrophilized channel sidewall and spread out on the wall surface. Therefore, the liquid water removal through the GDL is accelerated, and the water accumulation at the CL/GDL interface is alleviated. In addition, since the hydrophilic treatment of channels does not cause water plugging frequently, it drastically reduces the amplitude of voltage fluctuation. Hydrophilization of cathode channel effectively controls through-plane water transport and decreases both water flooding and plugging.

Synthesis and Characterization of Piperazinium Polyelectrolytes Carrying Hydrophobic Functionalities: Effect of Counter Ion and Charge Density on Flocculation

Following our recent synthesis and characterization of three new cationic polyelectrolytes with subtle hydrophobic variability, this paper reports their physical and chemical properties in aqueous media in relation to their chemical structure. Aryl substituted cationic polyelectrolytes varying with their charge density are reported for the first time. Viscosity studies show that these polymers display typical polyelectrolytic behavior. The flocculation efficiency of the polyelectrolytes was investigated with different counter ions. The zeta potential of the polyelectrolytes indicates the charge of the mono and diquaternary ammonium salts which is supported by chloride analysis. The morphology of polymer before and after flocculation was investigated. The introduction of methylene group and quaternary nitrogen play an important role in the flocculation process. It was shown that increasing the hydrophobicity and charge density of the aryl substituted polymer affects the flocculation in the industrial tannery effluent and bentonite suspension.

Hydrophobic surface functionalization of lignocellulosic jute fabrics by enzymatic grafting of octadecylamine

Enzymatic grafting of synthetic molecules onto lignins provides a mild and eco-friendly alternative for the functionalization of lignocellulosic materials. In this study, laccase-mediated grafting of octadecylamine (OA) onto lignin-rich jute fabrics was investigated for enhancing the surface hydrophobicity. First, the lignins in jute fabrics were isolated and analyzed in the macromolecular level by MALDI–TOF MS, 1H NMR, 13C NMR, and HSQC-NMR. Then, the surface of jute fabrics was characterized by FT-IR, XPS, and SEM. Subsequently, the nitrogen content of jute fabrics was determined by the micro-Kjeldahl method, and the grafting percentage (Gp) and grafting efficiency (GE) of the enzymatic reaction were calculated. Finally, the surface hydrophobicity of the jute fabrics was estimated by contact angle and wetting time measurements. The results indicate that the OA monomers were successfully grafted onto the lignin moieties on the jute fiber surface by laccase with Gp and GE values of 0.712% and 10.571%, respectively. Moreover, the modified jute fabrics via OA-grafting showed an increased wetting time of 18.5min and a contact angle of 116.72°, indicating that the surface hydrophobicity of the jute fabrics increased after the enzymatic grafting modification with hydrophobic OA molecules.

The effect of TiO 2 as a pigment in a polyurethane/polysiloxane hybrid coating/aluminum interface based on damage evolution

Abstract The effect of titanium oxide as an additive on the performance of a polyurethane/polysiloxane hybrid coating was characterized by an electrochemical approach. The performance evolution was quantified by exposing the hybrid coating on an aluminum substrate to NaCl solution at pH 5 over time. Real-time measurements were performed to quantify and correlate the mechanisms that occur at the coating/substrate interface. Electrochemical impedance spectroscopy (EIS) quantified the hybrid coating/substrate interface performance over the course of the 263 days of exposure, and electrically passive elements described and characterized the degradation/performance stages upon exposure to the acidic NaCl solution. The addition of TiO2 produced hydrophobicity functionality, and TiO2 acted as a physical barrier layer that influenced the initial damage stage. Different exposure times were associated the different stages of damage evolution for the hybrid coating and coating/substrate interfaces. Electrochemical testing with high-resolution techniques such as AFM (atomic force microscope) and IFM (infinite focus microscope) characterized the coating surface and the interface performance and resolved the surface and defect formation observed with different levels of TiO2 content. Of the systems tested, the system with 10 wt% TiO2 provided the best corrosion inhibition.

Nanostructured Biointerfaces: Nanoarchitectonics of Thermoresponsive Polymer Brushes Impact Protein Adsorption and Cell Adhesion.

Controlling the reversibility, quantity, and extent of biomolecule interaction at interfaces has a significant relevance for biomedical and biotechnological applications, because protein adsorption is always the first step when a solid surface gets in contact with a biological fluid. Polymer brushes, composed of end-tethered linear polymers with sufficient grafting density, are very promising to control and alter interactions with biological systems because of their unique structure and distinct collaborative response to environmental changes. We studied protein adsorption and cell adhesion at polymer brush substrates which consisted of poly(N-isopropylacrylamide) (PNIPAAm), having a lower critical solution temperature (LCST), to control bioadsorptive processes by changing the environmental temperature. Preparing the PNIPAAm brushes by the "grafting-to"-method two differently synthesized PNIPAAm polymers were used, at which one possessed an additional hydrophobic terminal headgroup. It is known that hydrophobic moieties can influence protein adsorption significantly. The films were comprehensively analyzed by in situ spectroscopic ellipsometry, contact angle measurements, streaming potential, and atomic force microscopy. Our study was mainly focused on the investigation of the fibrinogen (FGN) adsorption responsiveness both on homo polymer PNIPAAm brushes with and without the hydrophobic terminal functionalization, and further on binary brushes made of the polyelectrolyte poly(acrylic acid) (PAA) and one of the prior described two PNIPAAm species. The results show that the terminal hydrophobic modification of PNIPAAm has a considerable impact on wettability, LCST, and morphology of the homo and the binary brush systems, which consequently led to an alteration of FGN adsorption. By using binary PNIPAAm-PAA brushes with different composition it was possible to induce stimuli dependent FGN adsorption with a considerable amplified switching effect by introducing a hydrophobic terminal residue to PNIPAAm. Cell adhesion studies with human mesenchymal stem cells reflected the results of the FGN adsorption.

Preparation of a weak anion exchange/hydrophobic interaction dual-function mixed-mode chromatography stationary phase for protein separation using click chemistry.

In this study, 3-diethylamino-1-propyne was covalently bonded to the azide-silica by a click reaction to obtain a novel dual-function mixed-mode chromatography stationary phase for protein separation with a ligand containing tertiary amine and two ethyl groups capable of electrostatic and hydrophobic interaction functionalities, which can display hydrophobic interaction chromatography character in a high-salt-concentration mobile phase and weak anion exchange character in a low-salt-concentration mobile phase employed for protein separation. As a result, it can be employed to separate proteins with weak anion exchange and hydrophobic interaction modes, respectively. The resolution and selectivity of the stationary phase were evaluated in both hydrophobic interaction and ion exchange modes with standard proteins, respectively, which can be comparable to that of conventional weak anion exchange and hydrophobic interaction chromatography columns. Therefore, the synthesized weak anion exchange/hydrophobic interaction dual-function mixed-mode chromatography column can be used to replace two corresponding conventional weak anion exchange and hydrophobic interaction chromatography columns to separate proteins. Based on this mixed-mode chromatography stationary phase, a new off-line two-dimensional liquid chromatography technology using only a single dual-function mixed-mode chromatography column was developed. Nine kinds of tested proteins can be separated completely using the developed method within 2.0 h.

Dissipative particle dynamics study on self-assembled platycodin structures: The potential biocarriers for drug delivery

Platycodin, as a kind of plant based biosurfactants, are saponins which derived from the root of Platycodon grandiflorum A. DC. It has been confirmed that platycodin have the potential to enhance the solubility of hydrophobic drugs and function as the drug carrier, which depends on their micellization over critical micelle concentration (CMC) in aqueous solutions. With the purpose of investigating the effects of influencing factors on the micellization behavior of platycodin and obtaining the phase behavior details at a mesoscopic level, dissipative particle dynamics (DPD) simulations method has been adopted in this study. The simulations reveal that a rich variety of aggregates morphologies will appear with changes of structure or the concentration of saponins, including spherical, ellipse and oblate micelles and vesicles, multilamellar vesicles (MLVs), multicompartment vesicles (MCMs), tubular and necklace-like micelle. They can be formed spontaneously from a randomly generated initial state and the result has been represented in the phase diagrams. Furthermore, deeper explorations have been done on the concentration-dependent structure variation of spherical vesicles as well as the formation mechanism of MLVs. This work provides insight into the solubilization system formed by platycodin, and may serve as guidance for further development and application in pharmaceutical field of platycodin and other saponins.