Nihal Aydogan

Effect of Operating Parameters on the Separation of Sugars by Nanofiltration

ABSTRACT Due to the complexity of fermentation mixtures, separation of solutes and secondary substrates has a special importance. Membrane processes such as nanofiltration may offer good alternatives for the separation of fermentation products or recovery of substrates. For an efficient separation, the membrane type and operating parameters such as feed flow rate, operating pressure, and feed should be optimized. In this study the separation and recovery of sugars were targeted. It was found that with an increase of the feed flow rate, permeate flux increased since the effect of concentration polarization was minimized. As a result, experiments were carried out at the highest possible flow rate. The effect of pressure was studied at five pressures (10–50 bar). It was found that there is a linear relationship between the pressure and permeate flux up to 30 bars. Beyond 30 bars the effect of pressure became less significant. Thus, 30 bars was chosen as the operating pressure. To investigate the effect of co...

Use of Specifically Tailored Chelating Polymers for Boron Removal from Aqueous Solutions by Polymer Enhanced Ultrafiltration

Two selective functional polychelatogens, namely hydroxyethylaminoglycerol functioned poly(glycidylmethacrylate (PNS) and Poly(4-Vinyl-1,3-dioxalan-2-one-co-vinyl acetate) (COP) were synthesized and utilized in polymer-enhanced ultrafiltration (PEUF) to remove boron from the aqueous solution. The effect of operating parameters on boron retention was investigated. PNS was synthesized in three molecular weights to observe the effect of molecular weight in borate retention. Increase in pH increased boron retention for all of the synthesized polymers. Decrease in loading resulted in an enhancement in retention values when COP, medium (PNSM) and the low molecular weight of PNS (PNSL) were used. No significant change was observed in the permeate flux with COP (41 L/m2 · h), PNSL (48 L/m2 · h) and PNSM (47 L/m2 · h). However, a decrease in the loading led to a decrease in the permeate flux for high molecular weight PNS (PNSH). Conformational changes in the polymer structure were examined using dynamic and static light-scattering. Retention results for all of the polymers were found to be remarkably higher than the literature, when polyvinyl alcohol was used as the chelating agent. Satisfactory retention results were obtained using both PNSL (R: ∼54%) and PNSM (R: ∼57%), showing that PEUF can be employed effectively for borate removal using the specifically tailored polymers.

Biophysical investigation of the interfacial properties of cationic fluorocarbon/hydrocarbon hybrid surfactant: mimicking the lung surfactant protein C.

The interfacial behavior of the newly designed Fluorocarbon Hydrocarbon Cationic Lipid (FHCL or CH(3)(CH(2))(17)N(+)(C(2)H(5))(2)(CH(2))(3)(CF(2))(7)CF(3)I(-)) and its mixtures with a phospholipid (DPPC, Dipalmitoylphosphatidylcholine) at different mole fractions were investigated. This new molecule was synthesized to mimic the selected properties of lung surfactant, which is a natural lipid-protein mixture which is known to play important roles in the process of respiration, by considering the structure/function relation of lung surfactant protein (SP-C). Each segment in the molecular structure was selected to affect the molecular level interaction at the interface whereas the keeping the overall structure as simple as possible. The surface pressure area isotherms obtained for the mixtures of DPPC/FHCL indicated that there was repulsive interaction between DPPC and FHCL molecules. Due to the molecular level interaction, specifically at mole fraction 0.3, the isotherm obtained from that mixture resembled the isotherm obtained from the DPPC monolayer in the presence of SP-C. High elasticity of the interface was one of the important parameters for the respiration process, therefore, shear and dilatational elasticities of two-component systems were determined and they were found to be similar to the case where SP-C protein is present. Fluorescence microscopy images were taken in order to investigate the monolayer in details. The FHCL was able to fluidize the DPPC monolayer even at high surface pressures effectively. In addition, the cyclic compression-expansion isotherms were obtained to understand the spreading and re-spreading ability of the pure FHCL and the mixed DPPC/FHCL monolayers. At a specific mole fraction, X(FHCL)=0.3, the mixture exhibited good hysteresis in area, compressibility, recruitment index and re-spreading ability at the interface. All these results point out that FHCL can fulfill the selected features of the lung surfactant that are attributed to the presence of SP-C protein when mixed with DPPC, even if the molecular structure of the FHCL is quite simple.

Removal of Heavy Metals from Multicomponent Metal Mixtures by Polymer Enhanced Ultrafiltration: Effects of pH, Ionic Strength and Conformational Changes in Polymer Structure

Fractional separation of industrially important heavy metals (cadmium, nickel, zinc) from binary and ternary metal mixtures by continuous mode polymer enhanced ultrafiltration was studied. Polyethyleneimine (PEI) was used as a complexation polymer. Effects of pH and ionic strength on process efficiency were investigated. To gain insight about the characteristics of binding between highly branched PEI and metal ions and effect of salt concentration on this binding were investigated by performing dynamic and static light scattering measurements. It was observed that with optimum pH and salt concentration, fractional separation of metals can be achieved.

A new strategy to form multicompartment micelles: fluorocarbon-hydrocarbon ion-pair surfactant.

The hydrophobic core of the multicompartment micelles consists of incompatible and clearly separated distinct subdomains which make them different from the classical micelles. Owing to these properties multicompartment micelles have a great potential to be used as solubilization agents and carriers for a wide variety of applications where it is important to prevent the uncontrolled interaction of the solubilizates before reaching the target and to convey them to the specified point simultaneously. Here we show that effective compartmentalization inside the micelle and high solubilization capacity for the two immiscible water-insoluble materials in cases of both simultaneous and separate solubilization can be achieved by newly designed ion-pair hybrid surfactant CH(3)(CH(2))(11)(OCH(2)CH(2))(23)N(+)(C(2)H(5))(3)SO(3)(-)(CF(2))(7)CF(3) (C(12)E(23)N(+)SO(3)(-)F(8)) through the agency of favorable molecular design. Molecular structure is tailored by the approach of using a balance of forces to obtain compartmentalization, which is without precedent. This new molecule also has the properties of quite low critical micelle concentration and an extensive surfactant concentration range for solubilization which are additional important advantageous features.

Stimuli-responsive lipid nanotubes in gel formulations for the delivery of doxorubicin

Lipid nanotubes (LNTs) are one of the most advantageous structures for drug delivery and targeting. LNTs formed by a specially designed molecule called AQUA (AQ-NH-(CH2)10COOH (AQ: anthraquinone group) is used for drug delivery, and doxorubicin (DOX) is the drug selected. DOX and AQUA have some similarities in their molecular structures, so a significant amount of DOX can be loaded to LNTs. The AQUA LNTs are pH responsive, and drug loading increased almost linearly by increasing the pH, reaching a maximum value (96%) at pH 9.0. In terms of drug release, lower pHs are preferred. Drug-loaded LNTs are also mixed with four different gels (chitosan, alginate, hydroxypropyl methylcellulose and polycarbophil) to use the advantages of these gels. The drug release efficiency is studied using a Franz diffusion cell in which sheep colon membranes and dialysis membranes are utilized. The amount of released DOX from the chitosan gel formulations was quite high. Sodium alginate gels had lower release and slower diffusion of DOX. The cytotoxic effect of DOX-loaded AQUA LNTs has also been determined on cell cultures. Our new lipid nanotubes are a non-toxic, effective, biodegradable, biocompatible, stable and promising system for drug delivery and can be used for colonic administration of DOX for the treatment of colorectal cancer (CRC).

Formation of chiral nanotubes by the novel anthraquinone containing-achiral molecule.

Self-assembled lipid nanotubes arouse lots of interest due to their exceptional properties such as very simple production procedures, large variety of applications and high biocompatibility. In this study, the new eccentric but simple molecule, AQua (AQ-NH-(CH(2))(10)COOH; where AQ is anthraquinone), which integrates redox-active and pH sensitive character with nanotube forming capability has been designed. AQua forms self-assembled nanotubes by the chiral symmetry-breaking mechanism, in a high yield in the presence of ethanolamine. The nanotubes obtained in AQua-ethanolamine mixture are stable with time and resistant against drying and dilution at constant pH. However, pH change with dilution (without pH control) causes the unfolding of the nanotubes indicating the pH sensitive character. Existence of redox active anthraquinone group along with the carboxylic acid moiety gives the probability of reversibly controllable character to our nanotubes. The effect of the base type which is used to adjust the pH of the dispersion has also been investigated, and helix-tube-ribbon mixture is obtained when NaOH is used instead of ethanolamine. Although there are limited number of studies particularly in the field of reversibly controllable and/or redox active lipid nanotubes, controlled self-assembly and disassembly of these appreciable aggregates are very important for their usage in special applications. Thus, this study is hoped to be one of the remarkable studies for the development of reversibly controllable, redox active self assembled nanotubes.

Restoration of the interfacial properties of lung surfactant with a newly designed hydrocarbon/fluorocarbon lipid.

Serum proteins, especially fibrinogen, inactivate the lung surfactant mixture by adsorbing quickly and irreversibly to the alveolar air/aqueous interface. As a consequence of the inactivation, the surfactant becomes dysfunctional, and respiration cannot be maintained properly. Preventing the adsorption of surface active serum proteins to the air/water interface is important because this phenomenon causes fatal diseases such as acute respiratory distress syndrome (ARDS). Although some treatments exist, improvements in synthetic surfactants that can resist this inactivation are still expected. In this context, a novel ion pair lipid (IPL, CF3(CF2)7SO3(-)(CH2CH3)3N(+)(CH2OCH2)10(CH2)15CH3) has been designed and synthesized. This surfactant reduces the inhibitory effect of fibrinogen by selectively interacting with DPPC (dipalmitoylphosphatidylcholine) and mimicking some of the interfacial properties of the pulmonary surfactant protein B (SP-B). Surface pressure-area isotherms and fluorescence microscopy images demonstrate that IPL can mix and interact synergistically with DPPC due to its unique molecular structure. Hysteresis behaviors of the monolayers, which are composed of mixtures of DPPC and IPL at different molar ratios, indicate that with increasing amounts of IPL, the lipid losses from the interface induced by the presence of fibrinogen significantly decrease. It is also found that IPL is able to adsorb to monolayers formed in the presence of fibrinogen, whereas fibrinogen cannot penetrate the monolayers formed in the presence of IPL. These results indicate that by mimicking some of the interfacial properties of SP-B, this novel hybrid molecule is promising in terms of preventing fibrinogen adsorption and therefore resisting surfactant inactivation.

Treatment by nanofiltration of the bleed stream of a continuous alcohol fermentor

Abstract In continuous ethanol fermentation processes, which include product removal and recovery steps, to limit the concentration of secondary products, a bleed stream may be used. This stream contains several small molecular weight organic fermentation products and substrate sugars. To recover sugars and to minimize the amount of waste, the bleed stream is treated by nanofiltration. Three types of membranes were used in these experiments: 500 and 200 mwco (molecular weight cut off) polyamide and a thin‐film composite membrane with 99.2% NaCl rejection. Separation was achieved in two stages. First, separation of sugars was studied with 500 and 200 mwco membranes, and 84% total sugar rejection was obtained. Second, by‐products, which constitute the high total organic carbon (TOC) of the wastewater, were separated from the bleed stream by using the thin‐film composite membrane. The 95.1% of organics leading to TOC could be removed from the bleed by this method. Based on these results, a waste process, consisting of two nanofiltration units with a 500 mwco membrane and a thin‐film composite membrane, were suggested for the recovery of sugars and water.

Enhancing the Spreading Behavior on Pulmonary Mucus Mimicking Subphase via Catanionic Surfactant Solutions: Toward Effective Drug Delivery through the Lungs

Effective and efficient spreading of drug formulations on the pulmonary mucosal layer is key to successful delivery of therapeutics through the lungs. The pulmonary mucus layer, which covers the airway surface, acts as a barrier against therapeutic agents, especially in the case of chronic lung diseases due to increased thickness and viscosity of the mucus. Therefore, spreading of the drug formulations on the airways gets harder. Although spreading experiments have been conducted with different types of formulations on mucus-mimicking subphases, a highly effective formulation is yet to be discovered. Adding surfactant to such formulations decreases the surface tension and triggers the Marangoni forces to enhance the spreading behavior. In this study, catanionic (cationic + anionic) surfactant mixtures composed of dodecyltrimethylammonium bromide (DTAB) and dioctyl sulfosuccinate sodium salt (AOT) mixed at various mole ratios are prepared and their spreading behavior on both mucin and cystic fibrosis (CF) mucus models is investigated for the first time in the literature. Synergistic interaction is obtained between the components of the DTAB/AOT mixtures, and this interaction has enhanced the spreading of the formulation drop on both the mucin and CF mucus models when compared with the spreading performances of selected conventional surfactants. It is proposed that the catanionic surfactant mixtures, especially when mixed at the molar ratios of 8/2 and 7/3 (DTAB/AOT), improve the spreading even on the cystic fibrosis sputum model. As it is vital to transport a sufficient amount of drug to the targeted region for the treatment of diseases, this study presents an important application of the fundamentals of colloidal science to pharmaceutical nanotechnology.