Geoffrey Bothun

University of Rhode Island | URI · Department of Chemical Engineering

Detecting ultralow concentrations of anionic analytes in solution by surface-enhanced Raman spectroscopy (SERS) remains challenging due to their low affinity for SERS substrates. Two strategies were examined to enable in situ, liquid phase detection using 5(6)-carboxyfluorescein (5(6)-FAM) as a model analyte: functionalization of a gold nanopillar...

The phospholipid lecithin (L) and the nonionic surfactant Tween 80 (T) are used together in various contexts, including in drug delivery and oil spill remediation. There is hence a need to elucidate the nanostructures in LT mixtures, which is the focus of this paper. We study these mixtures using cryogenic transmission electron microscopy (cryo-TEM...

Per- and polyfluoroalkyl substances (PFAS) are a class of environmental toxicants, and some, such as perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA), have been associated with hepatic steatosis in rodents and monkeys. It was hypothesized that perfluorosulfonic acids (C4, 6, 8), perfluorocarboxylic acids (C4–14), perfluoro(2-me...

Poly- and Perfluoroalkyl substances (PFASs) are pollutants of emerging concern that persist in nature and pose environmental health and safety risks. PFAS disrupt biological membranes resulting in cellular inhibition, but the mechanism of disruption and the role of lipid composition remain unclear. We examine the role of phospholipid saturation and...

Protein coronas are known to alter the physicochemical properties, colloidal stability, and biological fate of nanoparticles. Using human serum albumin (HSA) and polystyrene nanoparticles (NPs) with anionic or cationic surface chemistries, we show that protein coronas also govern the surface activity of PS nanoparticles as well as their interaction...

The accurate and fast measurement of nitrate in seawater is important for monitoring and controlling water quality to prevent ecologic and economic disasters. In this work we show that the in situ detection of nitrate in aqueous solution is feasible at nanomolar concentrations through surface enhanced Raman spectroscopy (SERS) using native nanostru...

Surface Enhanced Raman Scattering (SERS) is a powerful tool for detection of analytes at low concentrations. Because the electric field generated by surface plasmons decays exponentially with distance, the analyte must be in close proximity to the substrate to generate a measurable Raman signal. This often requires customization of the substrate fo...

Dispersants, used in the mitigation of oil spills, are mixtures of amphiphilic molecules (surfactants) dissolved in a solvent. The recent large-scale use of dispersants has raised environmental concerns regarding the safety of these materials. In response to these concerns, our lab has developed a class of eco-friendly dispersants based on blends o...

Biodegradation of oil by marine bacteria is a significant pathway to oil spill remediation. Marine hydrocarbon degrading bacteria are known to form biofilms consisting of exopolymer and interconnected bacterial cells. This work indicates that microbial biofilm aids in the stabilization of dispersed oil droplets through the formation of biofilm at t...

The permeation of liquid and supercritical CO2 and the organic solvents toluene, heptane, and 1-propanol were investigated in unmodified hydrophilic and modified hydrophobic mesoporous γ-alumina and titania tubular ceramic membranes. These ceramic membranes are solvent resistant, thermally stable, and hydrophilic in nature. Viscosity-corrected solv...

Proteins in physiological fluids rapidly bind to nanoparticles (NPs), forming a protein corona (PC) that ultimately determines the biological identity of a nanoparticle. It is generally believed that the protein corona is responsible for controlling the colloidal stability of NPs, the way in which NPs taken up by cells and how NPs biodistribute and...

Oil degrading bacteria adhere to and colonize dispersed oil droplets, leading to biofilm formation in the form of free-floating agglomerates with entrapped oil droplets. Using a range of microscopy techniques, we have observed that the size and apparent density of biofilm agglomerates is dependent upon droplet size, which is in turn dependent upon...

Liposome-Nanoparticle Assemblies (LNAs) are vital in the context of novel targeted drug delivery systems, in addition to investigating nanoparticle-lipid bilayer interactions. Quantifying membrane structural properties and dynamics in presence of nanoparticle inclusions provides a simple model to elucidate nanoparticle effects on membrane biophysic...

Alcanivorax borkumensis (AB) is a marine bacterium that dominates bacterial communities around many oil spills because it enzymatically degrades the oil while using it as a nutrient source. Several dispersants have been used to produce oil-in-water emulsions following a spill. Compared to surface slicks, the additional oil-water surface area produc...

Nanoparticles (NPs) in contact with biological fluids are immediately coated by a protein corona (PC), composed of hard (strongly bounded) and/or soft (loosely associated) protein layers. The PC governs the biological ‘identity’ of a NP and represents the actual nano-interface that is presented to and interacts with cellular membranes. Understandin...

We have investigated the surface activity of poly(ethylene glycol) (PEG)-coated silver nanoparticles (Ag-PEG) in the presence or absence of lipid monolayers comprised of mono-unsaturated dioleoylphosphocholine and dioleoylphosphoglycerol (DOPC/DOPG; 1:1 mole ratio). Dynamic measurements of surface pressure demonstrated that Ag-PEG were surface-acti...

We present an approach to tune the multifunctionality of iron oxide nanoparticles (IONs) using mixed self-assembled monolayers of cationic lipid and anionic polyethylene glycol (PEG) lipid. By forming stable, monodispersed lipid coated IONs (L-IONs) through a solvent exchange technique, we were able to demonstrate the relationship between surface c...

Langmuir monolayers formed by phospholipids deposited at air/water interfaces represent simple, but effective model biological membranes for studying interaction mechanisms between engineered nanoparticles and lipid membranes. This work describes the use of dynamic surface pressure measurements, coupled with optical and electron microscopy, to eluc...

Engineered nanoparticles (ENPs) can interact with cell membranes by adsorbing onto their surface and compromising their integrity, permeability, and function. Fundamental information on these interaction mechanisms can be used to create ENPs with minimal or controlled membrane activity. The surface activity of ENPs is an important parameter in dete...

This study investigates silver nanoparticle interactions with lipid monolayer and bilayer surfaces using Langmuir Blodget technique, hyperspectral and transmission electron microscopy.

Anionic liposomes coated with the cationic polyelectrolyte poly-l-lysine (PLL), or layersomes, were used as soft, self-assembled templates for synthesizing gold nanoshells that absorb near infrared radiation. The gold-nanoshells were formed using two techniques (a) direct reduction of tetrachloroauric acid on the layersomes, and (b) reduction of a...

We have examined the interactions between polymer-coated anionic (Ag-COOH) and cationic (Ag-NH) silver nanoparticles, and net-anionic lipid monolayers using dynamic surface pressure measurements. Monolayers composed of saturated or mono-unsaturated mixtures of anionic phosphatidylglycerol (PG) and zwitterionic phosphatidylcholine (PC) lipids (3:1 m...

This study investigates the effects of polyethylene glycol (PEG)-coated silver NPs on lipid packing using dynamic surface-pressure measurements and hyperspectral microscopy. PEG coated nanoparticles are generally considered to be inert, however, there have been a number of studies showing that PEG and PEG coated NPs are surface active. In the case...

Layer-by-layer deposition of polyelectrolytes (PEs) onto self-assembled liposomes represents an alternative to PE deposition on solid particles for the formation of hollow nanoscale capsules. This work examines how competition between PE-liposome and inter-PE interactions drives the structure and colloidal stability of layersomes. Unlike solid part...

This study investigates the effects of polyethylene glycol (PEG)-coated silver NPs on lipid packing using dynamic surface-pressure measurements and hyperspectral microscopy.

Recent studies have demonstrated that nanoparticle interactions with cellular membranes can lead to membrane disruption and changes in cellular function. While interaction mechanisms are still not well understood, results have shown that nanoparticles can partition into lipids can cause changes in the physical properties of membranes including lipi...

Effectiveness of oil spill dispersants containing lecithin/Tween 80 (L/T) blends in ethanol was measured as a function of L:T ratio, surfactant:solvent ratio, solvent composition, and dispersant:oil ratio (DOR) using baffled flask dispersion effectiveness tests. Optimal L:T ratios are between 60:40 and 80:20 (w/w); at higher L:T ratios, effectivene...

Biodiesel-derived crude glycerol can be fermented to produce n-butanol, which is a platform chemical for biorefining and a biofuel. One limitation to crude glycerol fermentation is the presence of long-chain fatty acids (FAs) that can partition into cellular membranes, leading to membrane fluidization and interdigitation, which can inhibit cellular...

Recent studies have demonstrated that nanoparticle interactions with cellular membranes can lead to membrane disruption and changes in cellular function. While interaction mechanisms are still not well understood, results have shown that nanoparticles can partition into lipids can cause changes in the physical properties of membranes including lipi...

This work was conducted in order to design, characterize, and evaluate stable liposomes containing the hydrophobic drug raloxifene HCl (RAL) and hydrophilic doxycycline HCl (DOX), two potentially synergistic agents for treating osteoporosis and other bone lesions, in conjunction with a radio frequency-induced, hydrophobic magnetic nanoparticle-depe...

The self-assembly of polyelectrolyte layers on lipid bilayer surfaces is of great interest in the areas of biological device fabrication, drug delivery, and biomaterial design.The structure, function, and stability of these systems ultimately depend upon the interactions between the polyelectrolytes and lipid bilayers, and how these interactions ch...

Nano-differential scanning calorimetry (nano-DSC) is a powerful tool in the investigation of unilamellar (small unilamellar, SUVs, or large unilamellar, LUVs) vesicles, as well as lipids on supported bilayers, since it measures the main gel-to-liquid phase transition temperature (Tm), enthalpies and entropies. In order to assign these transitions i...

Adsorption of suspended particles to the interface of surfactant-dispersed oil droplets can alter emulsion phase and sedimentation behavior. This work examines the effects of model mineral aggregates (silica nanoparticle aggregates or SNAs) on the behavior of oil (octane)-water emulsions prepared using sodium bis(2-ethylhexyl) sulfosuccinate (DOSS)...

Clostridium pasteurianum ATCC 6013 achieves high n-butanol production when glycerol is used as the sole carbon source. In this study, the homeoviscous membrane response of C. pasteurianum ATCC 6013 has been examined through n-butanol challenge experiments. Homeoviscous response is a critical aspect of n-butanol tolerance and has not been examined i...

Centrifugation-based assays are commonly employed to study protein-membrane affinity or binding using lipid bilayer vesicles. An analogous assay has been developed to study nanoparticle-membrane interactions as a function of nanoparticle surface functionalization, membrane lipid composition, and monovalent salt concentration (NaCl). Anionic (carbox...

Nanotoxicity studies have shown that both carbon-based and inorganic engineered nanoparticles can be toxic to microorganisms. Although the pathways for cytotoxicity are diverse and dependent upon the nature of the engineered nanoparticle and the chemical environment, these studies have provided evidence that direct contact between nanoparticles and...

Peptide amphiphiles (PAs) are promising tools for the intracellular delivery of numerous drugs. PAs are known to be biodegradable systems. Here, four PA derivatives containing arginine and lysine conjugated with fatty acyl groups with different chain lengths, namely, PA1: R-K(C14)-R, PA2: R-K(C16)-R, PA3: K(C14)-R-K(C14), and PA4: K(C16)-R-K(C16),...

Nanoparticle-cell membrane interactions play an important role in nanotoxicology and nanomedicine. Changes in membrane structure, phase behavior, and permeability due to nanoparticle binding are dependent upon nanoparticle size and surface functionality. Knowledge of nanoparticle-membrane interaction mechanisms can be used for the a priori design n...

Cellular adaptation to elevated alcohol concentration involves altering membrane lipid composition to counteract fluidization. However, few studies have examined the biophysical response of biologically relevant heterogeneous membranes. Lipid phase behavior, molecular packing, and elasticity have been examined by surface pressure-area (π-A) analysi...

Bacteria adjust their membrane lipid composition to counteract the fluidizing effects of alcohol and to adapt to elevated alcohol concentrations during fermentation. Bacterial membranes are rich in anionic phosphatidylglycerols (PG), but little is known regarding alcohol partitioning into anionic membranes, particularly for n-butanol. This work exa...

Responsive Ultrafiltration Cellulose Acetate Membranes Containing N-Isopropylacrylamide (NIPAAm) and Superparamagnetic Iron Oxide (SPIO) Nanoparticles Sneha Chede1, Geoffrey D. Bothun2 and Isabel C. Escobar1 1Chemical and Environmental Engineering, The University of Toledo, Toledo, OH 2Department of Chemical Engineering, University of Rhode I...

Development of new drug formulations is plagued by high attrition rates. Only about 11% of new promising therapeutic compounds in clinical development are eventually approved. Nearly 70% of drug failures are attributed to poor pharmacokinetics, efficacy, toxicology, clinical safety, and formulation.[1] Liposome-nanoparticle assemblies (LNAs) can he...

Clostridium pasteurianum has been shown to ferment pure and partially purified biodiesel-derived crude glycerol into butanol at higher yields than obtained when sugars are used as the carbon source. n-Butanol is an attractive biofuel with favorable physicochemical properties. However, n-butanol is lipophilic and, when produced by fermentation, flui...

Interest in butanol as a biofuel is increasing due to its physicochemical properties (high energy density, low vapor pressure, hydrophobicity) and the ability to use it directly in gasoline engines. However, there are barriers to producing butanol cost-effectively at the industrial scale. Butanol production via fermentation is limited to low bacter...

Superparamagnetic iron oxide nanoparticles have been given much consideration for their applications for both drug delivery and gene therapy. In the presence of an inhomogeneous magnetic field it has been shown that cationic lipid coated magnetic nanoparticles (L-MNPs) may be used to deliver nucleic acids to mammalian cells, making this an ideal mo...

High-surface-area nanoparticles often cluster, with unknown effects on their cellular uptake and environmental impact. In the presence of vesicles or cell membranes, lipid adsorption can occur on the nanoparticles, resulting in the formation of supported lipid bilayers (SLBs), which tend to resist cellular uptake. When the amount of lipid available...

Title: Responsive Ultrafiltration Membranes Composed of N-isopropylacrylamide (NIPAAM) and Cellulose Acetate Abstract: The purpose of this study is to develop stimuli responsive membranes to control fouling using membrane casting dopes made of cellulose acetate with N-isopropylacrylamide (NIPAAM). NIPAAM is a stimuli-responsive polymer, which...

The structure and stability of hybrid lipid vesicles containing bilayer-encapsulated hydrophobic nanoparticles is dependent upon lipid phase behavior. By embedding stearylamine-stabilized gold nanoparticles in dipalmitoylphosphatidylcholine/dipalmitoylphosphatidylglycerol vesicles, we show that encapsulation at lipid to nanoparticle ratios from 10,...

Membrane phase behavior and fluidization have been examined in heterogeneous membranes composed of dipalmitoylphosphatidylcholine (DPPC, a saturated lipid) and dioleoylphosphatidylcholine (DOPC, an unsaturated lipid) at n-butanol concentrations below and above the interdigitation threshold of DPPC. Our results show that the presence of DOPC did not...

During the production of biodiesel, crude glycerol is produced as a byproduct at 10% (w/w). Clostridium pasteurianum has the inherent potential to grow on glycerol and produce 1,3-propanediol and butanol as the major products. Growth and product yields on crude glycerol were reported to be slower and lower, respectively, in comparison to the result...

Butanol has been identified by the US Department of Energy as an alternative fuel and a platform chemical for biorefining. When produced by fermentation, butanol concentrations are often low because of the low butanol tolerance of microorganisms. Low tolerance is attributed in part to butanol fluidization of cell membranes. One mechanism by which m...

The binding of hydrophilic nanoparticles to biomembranes is important for designing drug delivery systems as well as studying nanoparticle toxicity. Lipid bilayer vesicles or liposomes provide a simplified model to understand the fundamental mechanisms governing this binding. In this study, the effect of temperature and electrolytes on the binding...

The assembly and complexation of oppositely charged colloids are important phenomena in many natural and synthetic processes. Liposome-nanoparticle assemblies (LNAs) represent an interesting hybrid system that combines "soft" and "hard" colloidal materials. This work describes the formation and characterization of gel-phase LNAs formed by the bindi...

Introduction: Nanoscale assemblies are needed that achieve multiple therapeutic objectives, including cellular targeting, imaging, diagnostics and drug delivery. These must exhibit high stability, bioavailability and biocompatibility, while maintaining or enhancing the inherent activity of the therapeutic cargo. Liposome-nanoparticle assemblies (L...

When zwitterionic lipids fuse onto substrates such as silica (SiO 2), the water of hydration between the two approaching surfaces must be removed, giving rise to an effective hydration repulsion. Removal of water around the polar headgroups of the lipid and the silanols (SiOH) of SiO 2 allows supported lipid bilayer (SLB) formation, although an int...

This is a report on the design of tailored functional groups which mimic the repulsive forces at work in the natural-joint boundary lubricant known as lubricin. Lubricin, an amphiphilic polyelectrolyte biomolecule, decreases friction and cellular adhesion by exhibiting surface force fields based on steric hindrance, Debye electrostatic double layer...

Short cationic linear peptide analogs (LPAs, prepared as Arg-Cn -Arg-Cn -Lys, where Cn represents an alkyl linkage with n = 4, 7 or 11) were synthesized and tested in human breast carcinoma BT-20 and CCRF-CEM leukemia cells for their application as targeting ligands. With constant LPA charge (+4), increasing the alkyl linkage increases the hydropho...

Unlabelled: Folate-targeted cationic magnetoliposomes (FTMLs) have been prepared with coencapsulated doxorubicin (DOX) and anionic superparamagnetic iron oxide (SPIO) nanoparticles (NPs) with 5 nm γ-Fe(2)O(3) cores and 16 nm hydrodynamic diameters. NP encapsulation (89%) was confirmed by cryogenic transmission electron microscopy (TEM), and the pr...

Temperature measurements have been made within magnetite (Fe(3)O(4)) nanoparticle-liposome dispersions subjected to electromagnetic field at radiofrequency (RF) heating based on the fluorescence anisotropy of diphenylhexatriene (DPH) embedded within the bilayer. Incorporating cholesterol within dipalmitoylphosphatidylcholine (DPPC) bilayers broaden...

Peptide-amphiphiles (PAs) can self-assemble into a variety of lamellar and non-lamellar structures depending on their chemical structures, surface activities, and molecular packing parameters. When bioactive amino acids are employed, these structures can serve as therapeutic agents and delivery vehicles. To facilitate the assembly of cationic vesic...

The biodiesel industry is growing at a rapid rate in the US. The process of biodiesel production also results in the production of glycerol (10% w/w), a byproduct, which contains methanol, salts and fatty acids. Typically, crude glycerol cannot be used for chemical conversions, therefore requiring purification steps. But unfortunately, the purifica...

Cell penetrating peptides can traverse plasma cell membranes, which allows them to act as delivery vehicles for therapeutic molecules and as scaffolds for developing new antibiotics. We have previously introduced a series of linear peptide analogs (LPAs) comprising of three amino acids, arginine, arginine and lysine, linked through hydrophobic alky...

Supercritical carbon dioxide (scCO(2)) processing of drug/polymer mixtures is an environmentally friendly means of creating an impregnated polymeric carrier to enhance the aqueous dissolution rate of drugs that exhibit poor water solubility or are thermally labile. However, the role of drug solubilization and its interaction with the polymer during...

Nanoscale assemblies that can be activated and controlled through external stimuli represent a next stage in multifunctional therapeutics. We report the formation, characterization, and release properties of bilayer-decorated magnetoliposomes (dMLs) that were prepared by embedding small hydrophobic SPIO nanoparticles at different lipid molecule to...

The chain length dependence of the interaction of PFOA, a persistent environmental contaminant, with dimyristoyl- (DMPC), dipalmitoyl- (DPPC) and distearoylphosphatidylcholine (DSPC) was investigated using steady-state fluorescence anisotropy spectroscopy, differential scanning calorimetry (DSC) and dynamic light scattering (DLS). PFOA caused a lin...

Quantum dot (QD) nanocrystals provide highly efficient and photostable spectral emission for medical imaging and diagnostics.1-3 However, QDs have also exhibited cytotoxicity4,5 and are natively hydrophobic, as a result of the synthesis process, which requires that they be surface modified with biocompatible hydrophilic coatings to be dispersed in...

Bilayer-decorated magnetoliposomes have been designed with hydrophobic superparamagnetic iron oxide (SPIOs) nanoparticles using reverse phase evaporation. The ability to embed the nanoparticles (5 nm, oleic acid surface coating) within dipalmitoylphosphatidylcholine (DPPC) bilayers was examined as a function of the lipid to nanoparticle ratio. This...

The permeability of liquid and super critical CO2, and some selected organic solvents were examined in unmodified and surface-modified 5 and 10 nm titania, 5 nm -alumina ceramic membranes. The unmodified ceramic membranes are hydrophilic in nature. By surface modification, these membranes were made hydrophobic. The hydrophilic behavior of the oxide...

The effects of a series of low molecular weight water-soluble cationic linear peptide analogs (LPAs, <1000 MW) with increasing hydrophobic/hydrophilic balance on lipid bilayer phase behavior and permeability were examined using liposomes composed of zwitterionic dipalmitoylphosphatidylcholine (DPPC) and mixed zwitterionic/anionic DPPC/dipalmitoylph...

Cationic multifluorescent quantum dot liposomes (QD-Ls) have been prepared with both hydrophobic and hydrophilic CdSe/ZnS quantum dots by reverse phase evaporation. QD incorporation was confirmed by fluorescence and confocal microscopy. Incorporation did not affect QD photoactivity or damage bilayer or liposome structure. Cell uptake was examined i...

Lipid assemblies provide a biocompatible approach for preparing aqueous nanoparticles. In this work, dipalmitoylphosphatidylcholine (DPPC) was used to assist in the formation and dispersion of C(60) and nano-C(60) aggregates using a modified reverse phase evaporation (REV) method. This method led to the rapid formation of aqueous nano-C(60) at DPPC...

Solvent-dependent transport and the role of surface interactions were examined in commercial mesoporous ceramic membranes using permeability and thermoporometry measurements. The membranes chosen were titania (TiO2) with tortuous interconnected pores (1, 5, and 50 kDa, corresponding to pore diameters of ca. 8.2, 18.3, and 33.2 nm, respectively) and...

Lipid-based dispersion of nanoparticles provides a biologically inspired route to designing therapeutic agents and a means of reducing nanoparticle toxicity. Little is currently known on how the presence of nanoparticles influences lipid vesicle stability and bilayer phase behavior. In this work, the formation of aqueous lipid/nanoparticle assembli...

Purpose. Supercritical CO2 (scCO2) processing of drug/polymer mixtures is a favorable means of enhancing the aqueous dissolution rate of drugs that exhibit poor water solubility. However, the role of drug solubilization and its interaction with the polymer during processing on the extent and rate of dissolution has been ambiguous. In this study, we...

In this study we evaluate the use of dipalmitoylphosphatidylcholine (DPPC) as a biomolecular dispersing agent to aid in the formation aqueous C60 fullerene nanoparticles. Fullerenes are candidates for widespread application in, for example, the fields of cosmetics, drug delivery and energy conversion. However, the instability and potential toxicity...

In the past few years, the ability to traverse the plasma membrane of mammalian cells has been investigated with a wide range of cell permeating peptides. An understanding of the underlying non-endocytic mechanisms of these interactions may lead to the design of efficient peptide based therapeutic delivery systems. While the exact mechanism is poor...

To develop hydrophobic ceramic membranes, the permeability of liquids (water, ethanol, hexane, and CO2(l)) and gases (CO2 and N2) were examined in unmodified and surface-modified 1 kDa titania and 5 nm γ-alumina membranes. Octyltrichlorosilane (Cl3SiC8H17) and its fluorinated analog trichloroperfluorooctylsilane (Cl3SiC2H4C6F13) were chosen as modi...

Dehydrated and partially hydrated liquid carbon dioxide (>70 bar, 298 K) transport was examined in mesoporous ceramic membranes with γ-alumina (5 nm) and titania (1 and 5 kDa) separation layers. Liquid carbon dioxide, a green solvent alternative, is an apolar solvent with pressure-dependent physicochemical properties. Viscosity-corrected volumetric...

Perfluorooctane-1-sulfonic acid (PFOS) is emerging as an important persistent environmental pollutant. To gain insight into the interaction of PFOS with biological systems, the mixing behavior of dipalmitoylphosphatidylcholine (DPPC) with PFOS was studied using differential scanning calorimetry (DSC) and fluorescence anisotropy measurements. In the...

The morphology of the polymer produced during continuous precipitation polymerization of acrylic acid in supercritical carbon dioxide (scCO2) varied significantly with reaction conditions. Three different morphologies were observed:  a coagulum of primary particles with diameters of 100−200 nm, irregular particles with diameters of 5−20 μm, and sph...

Water‐in‐CO2 (W/CO2) reverse microemulsions stabilized with 1100 Da poly(ethylene glycol)‐poly(propylene glycol)‐poly(ethylene glycol) block copolymer were recovered using an ultrafiltration ceramic membrane in a custom high‐pressure cross‐flow separation unit. Viscosity‐corrected liquid CO2 flux (298 K) through the membrane was investigated as a f...

Fluidization and melting point depression of aqueous dipalmitoylphosphatidylcholine (DPPC, Tm ≈ 315 K) liposomes by compressed/supercritical n-alkanes (C2 and C3; 0.8–20.7 MPa) was quantified and compared to fluidization by liquid n-alkanes (C5–C10) using fluorescence anisotropy. The adsorption of ethane and propane into DPPC bilayers resulted in s...

The surface activities of lysozyme and dipalmitoyl phosphatidylcholine (DPPC) vesicles at aqueous/compressed fluid interfaces are examined via high-pressure interfacial tension measurements using the pendant drop technique. The density and interfacial tension in compressible fluid systems vary significantly with pressure, providing a versatile medi...

The influence of CO2 on the bilayer fluidity of liposomes, which are representative of model cellular membranes, was examined for the first time at the elevated pressures (up to 13.9 MPa) associated with CO2-based processing of liposomes and microbial sterilization. Fluidization and melting point depression of aqueous dipalmitoylphosphatidylcholine...

A novel continuous high-pressure biphasic bioreactor was designed to investigate the toxicity of compressed and supercritical fluids on the thermophilic bacterium Clostridium thermocellum. Cultures were conducted at 1.8 and 7.0 MPa hydrostatic pressure and in the presence of compressed N(2) (7.0 MPa), gaseous (1.8 MPa) and supercritical ethane (7.0...

The continuous culture of Clostridium thermocellum, a thermophilic bacterium capable of producing ethanol from cellulosic material, is demonstrated at elevated hydrostatic pressure (7.0 MPa, 17.3 MPa) and compared with cultures at atmospheric pressure. A commercial limitation of ethanol production by C. thermocellum is low ethanol yield due to the...

Ethanol and acetone were extracted from aqueous feed streams (10 wt.% solute) at ambient temperature using compressed propane (34.5 bar) and CO2 (69 bar) in a polypropylene hollow fiber membrane contactor (HFC). Overall mass transfer coefficients were determined and related to tubeside, membrane, and shellside mass transfer by varying the aqueous v...

The feasibility of extracting aqueous ethanol and acetone within a hollow fiber membrane contactor (HFC) has been examined using compressed CO2 (69 bar), ethane (69 bar), and propane (34.5 bar) at ambient temperature. Ethanol and acetone were chosen as ‘model’ fermentation products to further examine the potential for extractive fermentation with c...