Angelica L. Ottova

The lipid bilayer concept and its experimental realization: from soap bubbles, kitchen sink, to bilayer lipid membranes

Abstract The inspiration for lipid bilayer research, without question, comes from the biological world. Although self-assembled bilayer lipid membranes (BLMs) in vitro, were first reported in 1961, experimental scientists have been dealing with BLM-type interfacial adsorption phenomena since Robert Hooke’s time (1672). BLMs (of planar lipid bilayers) have been used in a number of applications ranging from basic membrane biophysics including transport, practical AIDS research, and ‘microchips’ studies, to the conversion of solar energy via water photolysis, to biosensor development using supported bilayer lipid membranes (s-BLMs), and to photobiology comprising apoptosis and photodynamic therapy. This paper presents an overview of the origin of the lipid bilayer concept and its experimental realization, as well as the studies of our laboratory and recent research of others on the use of BLMs as models of certain biomembranes. In addition, we describe briefly our present work on supported BLMs as biosensors and molecular devices; the experiments carried out in close collaboration with colleagues on s-BLMs are delineated.

Supported planar lipid bilayers (s-BLMs) as electrochemical biosensors

Abstract This paper presents a description of current research on the use of metal and hydrogel supported bilayer lipid membranes (s-BLMs and sb-BLMs) in the area of biosensor development. Simple and straight-forward experimental techniques for making these types of probes are given in some details. Emphasis is placed on the potential applications of these planar lipid bilayer-based probes. Among the topics covered include ion sensors, antigen–antibody interactions via electrical detection, probes for molecular species, supported BLMs doped with fullerenes and photoelectric effects in C 60 -containing BLMs.

Nanostructured platinum-lipid bilayer composite as biosensor.

The present work describes the preparation of supported bilayer lipid membrane (s-BLM) doped with metal nanoparticles for the design of biosensors. Platinum (Pt) nanoparticles were deposited through s-BLM to build a hybrid device of nanoscale electrode array by potential cycling in 1 mM K(2)PtCl(6) solution containing 0.1 M KCl. The properties of Pt nanoparticle-doped s-BLM composite were then characterized by cyclic voltammetry, electrochemical impedance spectroscopy (EIS) and atomic force microscopy (AFM). Our results showed that Pt nanoparticles grew in voids of the s-BLMs, through which the underlying glassy carbon (GC) electrode was connected, with maximum length extended out of the lipid membrane around 40 nm. Doping of Pt nanoparticles through s-BLM increased the membrane capacitance and decreased the membrane resistance of s-BLM. Pt nanoparticles array in s-BLM electrocatalyzed the reduction of oxygen (O(2)) in phosphate buffer solution (PBS). Practical application of Pt nanoparticle-doped s-BLM for the construction of glucose biosensor was also demonstrated in terms of its dose-response curve, stability and reproducibility. Thus, lipid membrane doped with Pt nanoparticles is a novel electrode system at nanoscale that can penetrate through the insulating membrane to probe molecular recognition and catalytic events at the lipid membrane-solution interface.

Biophysical aspects of agar-gel supported bilayer lipid nembranes: a new method for forming and studying planar bilayer lipid membranes

Abstract Conventional bilayer lipid membranes (BLMs), formed by either the painting method or the Langmuir-Blodgett technique, lack the desired stability. This paper presents a simple method for forming long-lived BLMs on agar-gel supports. The supported BLM reported has a greatly improved mechanical stability and also has desirable dynamic properties. These self-assembled BLMs are of significant interest, in view of their similarity of biological membranes, their molecular dimension and their spontaneous formation.

Electrochemical biosensor based on supported planar lipid bilayers for fast detection of pathogenic bacteria

This paper presents a new ion-channel biosensor based on supported bilayer lipid membrane for direct and fast detection of Campylobacter species. The sensing element of a biosensor is composed of a stainless-steel working electrode, which is covered by artificial bilayer lipid membrane (BLM). Antibodies to bacteria embedded into the BLM are used as channel forming proteins. The biosensor has a strong signal amplification effect, which is defined as the total number of ions transported across the BLM. The total number of (univalent) ions flowing through the channels is 1010 ions s−1. The biosensor showed a very good sensitivity and selectivity to Campylobacter species.

Self-assembled BLMs: biomembrane models and biosensor applications

Abstract In the last few years, there have been a number of research papers on self-assemblies of molecules as ‘advanced’ or ‘smart’ materials. The inspiration for this exciting research, without question, comes from the biological world, where, for example, the lipid bilayer of the cell membrane is the most important self-assembling system. Although the first report on self-assembled bilayer lipid membranes (BLMs) in vitro was published in 1962, interface science, including surface and colloid science, has been dealing with these interfacial self-assemblies of amphiphilic molecules since Robert Hookes time (1672). BLMs have been used in a number of applications, ranging from basic membrane biophysics studies to the conversion of solar energy via water photolysis, and to biosensor development using supported bilayer lipid membranes (s-BLMs and sb-BLMs). This paper briefly summarizes the past research on the use of BLMs as models of biological membranes and describes some details of our current work on supported BLMs as practical biosensors. Additionally, experiments carried out in close collaboration with others on s-BLMs and sb-BLMs are presented.

Electrochemistry of supported bilayer lipid membranes: background and techniques for biosensor development

Abstract Biomembranes play a pivotal role in signal transduction and information processing. This is due to the fact that most physiological activities involve some kind of lipid bilayer-based receptor-ligand contact interactions. There are many outstanding examples such as ion sensing, antigen-antibody binding, and ligand-gated channels, to name a few. One approach to study these interactions in vitro has been facilitated by employing self-assembled bilayer lipid membranes (BLMs). Our efforts have been focused on ion and/or molecular selectivity and specificity using easy-to-prepare self-assembled BLMs on solid support (i.e., s-BLMs and sb-BLMs) which, with their enhanced stability, greatly aid in research areas of membrane biophysics, biochemistry, and cell biology as well as in biosensor designs and molecular devices development. In this paper, our current work along with the experiments done in close collaboration with others on supported BLMs towards biosensor development will be discussed.

Self-assembled bilayer lipid membranes: from mimicking biomembranes to practical applications

Abstract Since their introduction in the early 1960s, bilayer lipid membranes (BLMs) along with liposomes a few years later, are the most widely used experimental models of biomembranes. The biomembranes enclosing cells and organelles are highly organized, structurally complex, dynamic systems that are the sites of energy conversion, material transport, biosensing, and signal transduction. The major cell membrane constituents are phospholipids, along with proteins, carbohydrates and their complexes, that spontaneously self-assemble into lipid bilayers. Hence, BLMs have been used from basic membrane biophysics studies to the conversion of solar energy. More recently, planar BLMs on various supports have gained considerable importance in the development of biosensors and molecular devices. These supported or s-BLMs have been deposited on a number of substrates such as SnO2, platinum, stainless steel, cooper, gels, and in microporous filters for practical applications. This paper summarizes the past research of our laboratory and others since 1973 on the use of BLMs as models of biological membranes. Further, the paper describes in some detail our current work on s-BLMs as potential biosensors and molecular devices.

From self-assembled bilayer lipid membranes (BLMs) to supported BLMs on metal and gel substrates to practical applications

Abstract The inspiration for lipid bilayer research, without question, comes from the biological world. Although the first report on self-assembled bilayer lipid membranes (BLMs) in vitro was reported in 1961, experimental scientists including surface, colloid, and bioscientists have been dealing with these interfacial phenomena since Robert Hookes time (1672). BLMs have been used in a number of applications ranging from basic membrane biophysics studies to the conversion of solar energy via water photolysis, and to biosensor development using supported bilayer lipid membranes (s-BLMs). This paper briefly summarizes the past research of our laboratory since 1974 on the use of BLMs as models of certain biological membranes. Further, we describe in some details our present work on supported BLMs as practical biosensors. The experiments carried out in close collaboration with others on s-BLMs are also presented. Supported BLMs provide the foundation for a variety of lipid bilayer-based molecular sensors that are sensitive, versatile, inexpensive (i.e. disposable) and open to all sorts of experimentation.

A combined AC-DC method for investigating supported bilayer lipid membranes

Abstract The basic electrical parameters of supported bilayer lipid membranes (s-BLMs) are resistance, capacitance, current, and voltage. Experimentally, either alternating current (AC) or direct current (DC) has been used for their measurements. We describe a simple setup for measurements of electrical properties of s-BLMs, using a complementary AC and DC method. The results obtained have demonstrated the usefulness of such an approach for studying s-BLMs. The frequency dependence of resistance and capacitance results obtained on s-BLMs make them possible to compare different published data obtained by AC at different frequencies or DC. In some experiments capacitance increases more sharply with the lowering of frequency. As demonstrated, certain s-BLMs modified by AQS or TCNQ can transfer electrons readily from the bathing solution via the BLM to the supporting Pt surface. The chances for biotechnological applications may be advanced by suitable modifications of s-BLMs.