Search results for: Steven P. Wrenn

Items from 1 to 20 out of 28 results

article

Enhanced antimicrobial effect of ultrasound by the food colorant Erythrosin B

Luis J. Bastarrachea, Martin Walsh, Steven P. Wrenn, Rohan V. Tikekar

Food Research International > 2017 > 100 > P1 > 344-351

The synergistic combination of the food colorant Erythrosin B (E-B, FD&C 3) (0, 25, and 50μM) and low-frequency ultrasound (20kHz, 0.86–0.90WmL⁻¹) was evaluated against Listeria innocua. Although E-B was antibacterial by itself, the inactivation rate significantly increased in a concentration-dependent manner upon exposure to ultrasound and followed a sigmoidal behavior. The enhanced antimicrobial...

article

Investigating the spatial extent of acoustically activated echogenic liposomes

An T. Nguyen, Youhan Sunny, Christopher Bawiec, Peter A. Lewin, more

Ultrasonics > 2017 > 77 > C > 176-182

The purpose of this work was to investigate the ability of bubbles entrapped within echogenic liposomes (ELIP) to serve as foci for cavitational events that would cause leakage in neighboring non-echogenic liposomes (NELIP). Previous studies have shown that entrapping bubbles into liposomes increases ultrasound-mediated leakage of hydrophilic components at ultrasound settings known to induce inertial...

article

Hydrophobic drug concentration affects the acoustic susceptibility of liposomes

An T. Nguyen, Peter A. Lewin, Steven P. Wrenn

Biochimica et Biophysica Acta (BBA) - General Subjects > 2015 > 1850 > 4 > 667-672

The purpose of this study was to investigate the effect of encapsulated hydrophobic drug concentration on ultrasound-mediated leakage from liposomes. Studies have shown that membrane modifications affect the acoustic susceptibility of liposomes, likely because of changes in membrane packing. An advantage of liposome as drug carrier is its ability to encapsulate drugs of different chemistries. However,...

article

Size distribution of microbubbles as a function of shell composition

Stephen Dicker, Michał Mleczko, Georg Schmitz, Steven P. Wrenn

Ultrasonics > 2013 > 53 > 7 > 1363-1367

The effect of modifying the shell composition of a population of microbubbles on their size demonstrated through experiment. Specifically, these variations include altering both the mole fraction and molecular weight of functionalized polymer, polyethylene glycol (PEG) in the microbubble phospholipid monolayer shell (1–15mol% PEG, and 1000–5000g/mole, respectively). The size distribution is measured...

article

Influence of Shell Composition on the Resonance Frequency of Microbubble Contrast Agents

Stephen Dicker, Michał Mleczko, Monica Siepmann, Nicole Wallace, more

Ultrasound in Medicine & Biology > 2013 > 39 > 7 > 1292-1302

The effect of variations in microbubble shell composition on microbubble resonance frequency is revealed through experiment. These variations are achieved by altering the mole fraction and molecular weight of functionalized polyethylene glycol (PEG) in the microbubble phospholipid monolayer shell and measuring the microbubble resonance frequency. The resonance frequency is measured via a chirp pulse...

article

Bubble nucleation in lipid bilayers: A mechanism for low frequency ultrasound disruption

Steven P. Wrenn, Eleanor Small, Nily Dan

BBA - Biomembranes > 2013 > 1828 > 4 > 1192-1197

Recent experiments have shown that low frequency ultrasound (LFUS) induces leakage from lipid vesicles. However, the mechanism by which LFUS disrupts the lipid bilayer structure is not clear. In this paper we develop a theoretical model to test the possibility that gas molecule partitioning from the aqueous media into the lipid bilayer core can lead to the nucleation of microscale gas bubbles. If...

article

Mechanistic roles of lipoprotein lipase and sphingomyelinase in low density lipoprotein aggregation

Michael J. Walters, Steven P. Wrenn

Journal of Colloid And Interface Science > 2011 > 363 > 1 > 268-274

The initiation of atherosclerosis involves retention of colloidal atherogenic lipoproteins, primarily low density lipoprotein (LDL), in the arterial intima. This retention occurs when LDL binds to smooth muscle cell extracellular matrix (SMC ECM), and is enhanced by lipoprotein lipase (LpL) and sphingomyelinase (Smase). Here we use a fluorescence assay and dynamic light scattering to study the individual...

article

Ultrasound-induced transport across lipid bilayers: Influence of phase behavior

Eleanor F. Small, Michael C. Willy, Peter A. Lewin, Steven P. Wrenn

Colloids and Surfaces A: Physicochemical and Engineering Aspects > 2011 > 390 > 1-3 > 40-47

This paper examines the role of lipid membrane phase behavior on the kinetics and mechanism of ultrasound-induced transport. We present a quantitative study of low frequency ultrasound (LFUS)-induced release of calcein from the aqueous core of large unilamellar vesicles (LUVs) comprising a wide range of lipid compositions. The LUVs comprise of the lipids 1,2-dioleoyl-phosphocholine (DOPC), 1,2-dipalmitoyl-phosphocholine...

article

Size-selective uptake of colloidal low density lipoprotein aggregates by cultured white blood cells

Michael J. Walters, Steven P. Wrenn

Journal of Colloid And Interface Science > 2010 > 350 > 2 > 494-501

This paper illustrates how principles of colloid science are useful in studying atherosclerosis. Accumulation of foam cells in the arterial intima is a key step in atherogenesis. The extent of foam cell formation is enhanced by low density lipoprotein (LDL) aggregates, and we have previously shown that the size of sphingomyelinase (Smase)-hydrolysis-induced aggregates depends directly on the concentration...

article

Phospholipid-stabilized microbubbles: Influence of shell chemistry on cavitation threshold and binding to giant uni-lamellar vesicles

Steven P. Wrenn, Michał Mleczko, Georg Schmitz

Applied Acoustics > 2009 > 70 > 10 > 1313-1322

We demonstrate the feasibility of covalently linking a single microbubble to a single, giant uni-lamellar vesicle (GUV). Such a combination of GUV plus microbubble might prove useful as a new drug delivery vehicle involving microbubble cavitation-induced sonoporation of the vesicle bilayer as a release mechanism. We therefore applied the well known methodology of passive cavitation detection to measure...

article

Gender Differences in Cholesterol Nucleation in Native Bile: Estrogen Is a Potential Contributory Factor

Angela C. Brown, Steven P. Wrenn, Nandita Suresh, William C. Meyers, more

The Journal of Membrane Biology > 2009 > 232 > 1-3 > 35-45

The incidence of gallstone disease is two to three times higher in women than in men, and female sex hormones, particularly estrogens, have been implicated as contributory factors. Cholesterol nucleation is the initial step in gallstone pathogenesis and proceeds from cholesterol-rich phospholipid vesicles. The aim of this study was to investigate if there is a difference in cholesterol nucleation...

article

Effect of Sphingomyelinase-Mediated Generation of Ceramide on Aggregation of Low-Density Lipoprotein

Michael J. Walters, Steven P. Wrenn

Langmuir > 2008 > 24 > 17 > 9642 - 9647

article

Measuring Raft Size as a Function of Membrane Composition in PC-Based Systems: Part 1 − Binary Systems

Angela C. Brown, Kevin B. Towles, Steven P. Wrenn

Langmuir > 2007 > 23 > 22 > 11180 - 11187

article

Measuring Raft Size as a Function of Membrane Composition in PC-Based Systems: Part II Ternary Systems

Angela C. Brown, Kevin B. Towles, Steven P. Wrenn

Langmuir > 2007 > 23 > 22 > 11188 - 11196

article

Effect of Membrane Microheterogeneity and Domain Size on Fluorescence Resonance Energy Transfer

Kevin B. Towles, Angela C. Brown, Steven P. Wrenn, Nily Dan

Biophysical Journal > 2007 > 93 > 2 > 655-667

Studies of multicomponent membranes suggest lateral inhomogeneity in the form of membrane domains, but the size of small (nanoscale) domains in situ cannot be determined with current techniques. In this article, we present a model that enables extraction of membrane domain size from time-resolved fluorescence resonance energy transfer (FRET) data. We expand upon a classic approach to the infinite...

article

In vitro ultrasound-mediated leakage from phospholipid vesicles

Mona Pong, Sumet Umchid, Andrew J. Guarino, Peter A. Lewin, more

Ultrasonics > 2006 > 45 > 1-4 > 133-145

Interest in using ultrasound energy in wound management and intracellular drug delivery has been growing rapidly. Development and treatment optimization of such non-diagnostic applications requires a fundamental understanding of interactions between the acoustic wave and phospholipid membranes, be they cell membranes or liposome bilayers. This work investigates the changes in membrane permeation (leakage...

article

A Time-Resolved Fluorescence Diphenylhexatriene (DPH) Anisotropy Characterization of a Series of Model Lipid Constructs for the Sperm Plasma Membrane

Gregory M. Troup, Steven P. Wrenn, Meirav Apel-Paz, Gustavo F. Doncel, more

Industrial & Engineering Chemistry Research > 2006 > 45 > 21 > 6939 - 6945

article

Sphingomyelinase-to-LDL molar ratio determines low density lipoprotein aggregation size: biological significance

Andrew J. Guarino, Thomas N. Tulenko, Steven P. Wrenn

Chemistry and Physics of Lipids > 2006 > 142 > 1-2 > 33-42

The subendothelial retention of low density lipoproteins (LDL) is believed to be the central pathogenic event in atherosclerosis, as stated by the response-to-retention hypothesis. Sphingomyelinase, an enzyme present in the arteries, has been proven to promote LDL aggregation. This study investigates the hypothesis that the extent of LDL aggregation is determined by the molar ratio of sphingomyelinase...

article

Interactions between sphingomyelin and cholesterol in low density lipoproteins and model membranes

Andrew J. Guarino, Sum P. Lee, Steven P. Wrenn

Journal of Colloid And Interface Science > 2006 > 293 > 1 > 203-212

This work examines three related, but previously unexplored, aspects of membrane biophysics and colloid science in the context of atherosclerosis. First, we show that sphingomyelinase (SMase)-induced aggregation of low density lipoproteins (LDLs), coupled with LDL exposure to cholesterol esterase (CEase), results in nucleation of cholesterol crystals, long considered the hallmark of atherosclerosis...

article

Combined Interaction of Phospholipase C and Apolipoprotein A-I with Small Unilamellar Lecithin-Cholesterol Vesicles: Influence of Apolipoprotein A-I Concentration and Vesicle Composition ^†

Manasa V. Gudheti, Sum P. Lee, Dganit Danino, Steven P. Wrenn

Biochemistry > 2005 > 44 > 19 > 7294 - 7304

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Journal of Colloid And Interface Science (4)
Langmuir (3)
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Chemistry and Physics of Lipids (2)
Colloids and Surfaces B: Biointerfaces (2)
Applied Acoustics (1)
BBA - Biomembranes (1)
Biochimica et Biophysica Acta (BBA) - General Subjects (1)
Biophysical Journal (1)
Colloids and Surfaces A: Physicochemical and Engineering Aspects (1)
FEBS Letters (1)
Food Research International (1)
Industrial & Engineering Chemistry Research (1)
The Journal of Membrane Biology (1)
Ultrasound in Medicine & Biology (1)
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INFONA - science communication portal

Search results for: Steven P. Wrenn

Enhanced antimicrobial effect of ultrasound by the food colorant Erythrosin B

Investigating the spatial extent of acoustically activated echogenic liposomes

Hydrophobic drug concentration affects the acoustic susceptibility of liposomes

Size distribution of microbubbles as a function of shell composition

Influence of Shell Composition on the Resonance Frequency of Microbubble Contrast Agents

Bubble nucleation in lipid bilayers: A mechanism for low frequency ultrasound disruption

Mechanistic roles of lipoprotein lipase and sphingomyelinase in low density lipoprotein aggregation

Ultrasound-induced transport across lipid bilayers: Influence of phase behavior

Size-selective uptake of colloidal low density lipoprotein aggregates by cultured white blood cells

Phospholipid-stabilized microbubbles: Influence of shell chemistry on cavitation threshold and binding to giant uni-lamellar vesicles

Gender Differences in Cholesterol Nucleation in Native Bile: Estrogen Is a Potential Contributory Factor

Effect of Sphingomyelinase-Mediated Generation of Ceramide on Aggregation of Low-Density Lipoprotein

Measuring Raft Size as a Function of Membrane Composition in PC-Based Systems: Part 1 − Binary Systems

Measuring Raft Size as a Function of Membrane Composition in PC-Based Systems: Part II Ternary Systems

Effect of Membrane Microheterogeneity and Domain Size on Fluorescence Resonance Energy Transfer

In vitro ultrasound-mediated leakage from phospholipid vesicles

A Time-Resolved Fluorescence Diphenylhexatriene (DPH) Anisotropy Characterization of a Series of Model Lipid Constructs for the Sperm Plasma Membrane

Sphingomyelinase-to-LDL molar ratio determines low density lipoprotein aggregation size: biological significance

Interactions between sphingomyelin and cholesterol in low density lipoproteins and model membranes

Combined Interaction of Phospholipase C and Apolipoprotein A-I with Small Unilamellar Lecithin-Cholesterol Vesicles: Influence of Apolipoprotein A-I Concentration and Vesicle Composition ^†

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