Application of Ganglioside-Sensitized Liposomes in a Flow Injection Immunoanalytical System for the Determination of Cholera Toxin

Advanced in developmental organic and inorganic nanomaterial: a review

With the unique properties such as high surface area to volume ratio, stability, inertness, ease of functionalization, as well as novel optical, electrical, and magnetic behaviors, nanomaterials have a wide range of applications in various fields with the common types including nanotubes, dendrimers, quantum dots, and fullerenes. With the aim of providing useful insights to help future development of efficient and commercially viable technology for large-scale production, this review focused on the science and applications of inorganic and organic nanomaterials, emphasizing on their synthesis, processing, characterization, and applications on different fields. The applications of nanomaterials on imaging, cell and gene delivery, biosensor, cancer treatment, therapy, and others were discussed in depth. Last but not least, the future prospects and challenges in nanoscience and nanotechnology were also explored.

Fluorescent immunoliposomal nanovesicles for rapid multi-well immuno-biosensing of histamine in fish samples

Scombroid poisoning in fish-based and other food products has raised concerns due to toxicity outbreaks and incidences associated with histamine, thus measuring the amount of histamine toxic molecule is considered crucial quality indicator of food safety and human health. In this study, liposome-based measurement of histamine was performed via rupturing mechanism of sulforhodamine B dye encapsulated anti-histamine antibody conjugated liposomal nanovesicles. The immunosensing ability of immuno-liposomal format was assessed by monitoring the fluorescence at excitation/emission wavelength of 550/585 nm. Immuno-liposomal format assays were considered, one based on single wash procedure (Method 1), which had a detection limit of 10 ppb and quantification limit 15-80 ppb. While Method 2 based on one-by-one wash procedure had a detection limit of 2-3 ppb and quantification limit 8.5 ppb-200 ppm that required 2 h 30 min to perform. In view of better quantification limit, Method 2 was chosen for further tests required to validate its applicability in real samples. The feasibility of Method 2 was reconfirmed in fresh mackerel fish, and canned fish (tuna and salmon) with a similar detection limits but with low amplified fluorescence signals and sufficient levels of histamine recovery from fresh mackerel (73.50-99.98%), canned tuna (79.08-103.74%) and salmon (74.56-99.02%). The specificity and method accuracy were expressed as % CV in the range 5.34%-8.48%. Overall, the developed multi-well sensing system (Method 2) showed satisfactory specificity, cost effectiveness, rapidity, and stability for monitoring histamine toxicity as a practical food diagnostic device.

Aptamer lateral flow assays for rapid and sensitive detection of cholera toxin

Aptamers are envisioned to serve as powerful synthetic substitutes to antibodies in a variety of bioanalytical assay formats. However, lateral flow assays (LFAs) remain dominated by antibody-based strategies. In this study, a LFA for the detection of cholera toxin as a model analyte is developed and optimized using a synthetic aptamer and a naturally occurring receptor as biorecognition elements and directly compared with solely aptamer and aptamer and antibody-based alternative approaches. The aptamer (CT916) recently selected by our group, GM1 receptors and an anti-cholera toxin antibody were evaluated. Relying solely on molecules that can easily be synthesized while aiming for high sensitivity, we applied a novel combination of capture aptamer and GM1 cell receptor-labeled liposomes for cholera toxin detection, achieving a limit of detection (LOD) of 2 ng ml-1 (3σ)/10 ng ml-1 (visual) in ∼15 min. To put our novel aptasensor into perspective, we developed a competitive lateral flow assay, exploiting the competition of cholera toxin in solution with immobilized cholera toxin for binding of aptamer-coated gold nanoparticles (AuNPs) (LOD = 51 ng ml-1 (3σ)/100 ng ml-1 (visual), assay time ∼10 min). As dual simultaneously binding aptamers were not available, we designed aptamer antibody pair-based lateral flow assays using aptamer-coated AuNPs which yielded a LOD of 5 ng ml-1 (by the 3σ rule)/10 ng ml-1 (visual) in a 10 min assay and an even better LOD of 0.6 ng ml-1 (3σ)/1 ng ml-1 (visual), with an ∼20 min total assay time. All set-ups are highly specific and provide an excellent alternative for cholera toxin detection in places where professional knowledge and sophisticated equipment are not readily available and cost efficient, simple, and rapid tests are needed, while the combination of GM1 cell receptor-labeled liposomes and aptamers is clearly the most promising.

A Label-Free Photoluminescence Genosensor Using Nanostructured Magnesium Oxide for Cholera Detection

Nanomaterial-based photoluminescence (PL) diagnostic devices offer fast and highly sensitive detection of pesticides, DNA, and toxic agents. Here we report a label-free PL genosensor for sensitive detection of Vibrio cholerae that is based on a DNA hybridization strategy utilizing nanostructured magnesium oxide (nMgO; size >30 nm) particles. The morphology and size of the synthesized nMgO were determined by transmission electron microscopic (TEM) studies. The probe DNA (pDNA) was conjugated with nMgO and characterized by X-ray photoelectron and Fourier transform infrared spectroscopic techniques. The target complementary genomic DNA (cDNA) isolated from clinical samples of V. cholerae was subjected to DNA hybridization studies using the pDNA-nMgO complex and detection of the cDNA was accomplished by measuring changes in PL intensity. The PL peak intensity measured at 700 nm (red emission) increases with the increase in cDNA concentration. A linear range of response in the developed PL genosensor was observed from 100 to 500 ng/μL with a sensitivity of 1.306 emi/ng, detection limit of 3.133 ng/μL and a regression coefficient (R(2)) of 0.987. These results show that this ultrasensitive PL genosensor has the potential for applications in the clinical diagnosis of cholera.

Resuscitation Using Liposomal Vasopressin in an Animal Model of Uncontrolled Hemorrhagic Shock

Background

Current research suggests that administration of vasopressin to patients with uncontrolled hemorrhagic shock (UHS) can avoid the detrimental effects associated with aggressive fluid resuscitation. However, vasopressin has a short half-life of 10~35 minutes in in vivo use and precludes its use in the pre-hospital setting. To increase the half-life of vasopressin, we proposed to synthesize liposome-encapsulated vasopressin and test it in a rat model of UHS.

Methods

The film hydration method was used to prepare liposomal vasopressin consisting of: Dipalmitoylphosphatidylcholine, cholesterol, and dipalmitoyl phosphatidylethanolamine (20:20:1 mole ratio). 42 rats were subjected to UHS and randomly received 5 different treatments (vasopressin, liposomal vasopressin, lactate ringer (LR), liposome only and sham). Outcome of UHS were measured using 4 common prognostic tests: mean arterial pressure (MAP), serum lactate level, inflammatory profile and pulmonary edema.

Results

The dynamic light scattering results confirmed that we had prepared a successful liposomal vasopressin complex. Comparing the serum vasopressin concentration of liposomal vasopressin and vasopressin treated animals by ELISA, we found that the concentration of vasopressin for the liposomal vasopressin treated group is higher at 60 minutes. However, there was no significant difference between the MAP profile of rats treated with vasopressin and liposomal vasopressin in UHS. We also observed that animals treated with liposomal vasopressin performed indifferently to vasopressin treated rats in serum lactate level, inflammatory profile and edema profile. For most of our assays, the liposome only control behaves similarly to LR resuscitation in UHS rats.

Conclusion

We have synthesized a liposomal vasopressin complex that can prolong the serum concentration of vasopressin in a rat model of UHS. Although UHS rats treated with either liposomal vasopressin or vasopressin showed no statistical differences, it would be worthwhile to repeat the experiments with different liposomal compositions.

Membrane adhesion and the formation of heterogeneities: biology, biophysics, and biotechnology

Membrane adhesion is essential to many vital biological processes. Sites of membrane adhesion are often associated with heterogeneities in the lipid and protein composition of the membrane. These heterogeneities are thought to play functional roles by facilitating interactions between proteins. However, the causal links between membrane adhesion and membrane heterogeneities are not known. Here we survey the state of the field and indicate what we think are understudied areas ripe for development.

Advanced techniques for detection and identification of microbial agents of gastroenteritis

Gastroenteritis persists as a worldwide problem, responsible for approximately 2 million deaths annually. Traditional diagnostic methods used in the clinical microbiology laboratory include a myriad of tests, such as culture, microscopy, and immunodiagnostics, which can be labor intensive and suffer from long turnaround times and, in some cases, poor sensitivity. [corrected]. This article reviews recent advances in genomic and proteomic technologies that have been applied to the detection and identification of gastrointestinal pathogens. These methods simplify and speed up the detection of pathogenic microorganisms, and their implementation in the clinical microbiology laboratory has potential to revolutionize the diagnosis of gastroenteritis.

Profiling lipid-protein interactions using nonquenched fluorescent liposomal nanovesicles and proteome microarrays

Fluorescent liposomal nanovesicles (liposomes) are commonly used for lipid research and/or signal enhancement. However, the problem of self-quenching with conventional fluorescent liposomes limits their applications because these liposomes must be lysed to detect the fluorescent signals. Here, we developed a nonquenched fluorescent (NQF)1 liposome by optimizing the proportion of sulforhodamine B (SRB) encapsulant and lissamine rhodamine B-dipalmitoyl phosphatidylethanol (LRB-DPPE) on a liposomal surface for signal amplification. Our study showed that 0.3% of LRB-DPPE with 200 μm of SRB provided the maximal fluorescent signal without the need to lyse the liposomes. We also observed that the NQF liposomes largely eliminated self-quenching effects and produced greatly enhanced signals than SRB-only liposomes by 5.3-fold. To show their application in proteomics research, we constructed NQF liposomes that contained phosphatidylinositol 3,5-bisphosphate (PI(3,5)P2) and profiled its protein interactome using a yeast proteome microarray. Our profiling led to the identification of 162 PI(3,5)P2-specific binding proteins (PI(3,5)P2-BPs). We not only recovered many proteins that possessed known PI(3,5)P2-binding domains, but we also found two unknown Pfam domains (Pfam-B_8509 and Pfam-B_10446) that were enriched in our dataset. The validation of many newly discovered PI(3,5)P2-BPs was performed using a bead-based affinity assay. Further bioinformatics analyses revealed that the functional roles of 22 PI(3,5)P2-BPs were similar to those associated with PI(3,5)P2, including vesicle-mediated transport, GTPase, cytoskeleton, and kinase. Among the 162 PI(3,5)P2-BPs, we found a novel motif, HRDIKP[ES]NJLL that showed statistical significance. A docking simulation showed that PI(3,5)P2 interacted primarily with lysine or arginine side chains of the newly identified PI(3,5)P2-binding kinases. Our study showed that this new tool would greatly benefit profiling lipid-protein interactions in high-throughput studies.

Signal-enhancer molecules encapsulated liposome as a valuable sensing and amplification platform combining the aptasensor for ultrasensitive ECL immunoassay

An innovatory ECL immunoassay strategy was proposed to detect the newly developing heart failure biomarker N-terminal pro-brain natriuretic peptide (NT-proBNP). Firstly, this strategy used small molecules encapsulated liposome as immune label to construct a sandwich immune sensing platform for NT-proBNP. Then the ECL aptasensor was prepared to collect and detect the small molecules released from the liposome. Finally, based on the ECL signal changes caused by the small molecules, the ECL signal indirectly reflected the level of NT-proBNP antigen. In this experiment, the cocaine was chosen as the proper small molecule that can act as signal-enhancer to enhance the ECL of Ru(bpy)(3)(2+). The cocaine-encapsulated liposomes were successfully characterized by TEM. The quantificational calculation proved the ∼5.3×10(3) cocaine molecules per liposome enough to perform the assignment of signal amplification. The cocaine-binding ECL aptasensor further promoted the work aimed at amplifying signal. The performance of NT-proBNP assay by the proposed strategy exhibited high sensitivity and high specificities with a linear relationship over 0.01-500 ng mL(-1) range, and a detection limit down to 0.77 pg mL(-1).

Nanoscale labels: nanoparticles and liposomes in the development of high-performance biosensors

Technology for the detection of biological species has generated considerable interest in a variety of fields including healthcare, defense, food and environmental monitoring. In a biosensor, labeled specific binding partners are used to emit a detectable signal. Owing to their unique properties, nanomaterials have been proposed as a novel label category and have led to the development of new assays and new transduction mechanisms. In this article, the role of three major types of nanoscale labels (metallic, semiconductor and liposome nanoparticles) in the development of a new generation of optical, electrochemical or gravimetric biosensors will be presented. The underlying transduction principles will be briefly explained and assay strategies relying on the use of these ‘nanolabels’ will be described. The contribution to increased assay performance and sensitivity will be highlighted. Approaches towards simple, cost efficient and sensitive assays are essential to meet the demands of a growing number of applications.

Toxin detection by surface plasmon resonance

Significant efforts have been invested in the past years for the development of analytical methods for fast toxin detection in food and water. Immunochemical methods like ELISA, spectroscopy and chromatography are the most used in toxin detection. Different methods have been linked, e.g. liquid chromatography and mass spectrometry (LC-MS), in order to detect as low concentrations as possible. Surface plasmon resonance (SPR) is one of the new biophysical methods which enables rapid toxin detection. Moreover, this method was already included in portable sensors for on-site determinations. In this paper we describe some of the most common methods for toxin detection, with an emphasis on SPR.

Disposable electrochemical immunosensor for carcinoembryonic antigen using ferrocene liposomes and MWCNT screen-printed electrode

Disposable electrochemical immunosensor for the detection of carcinoembryonic antigen (CEA) in saliva and serum was developed. Monoclonal anti-CEA antibodies (alphaCEA) were covalently immobilized on polyethyleneimine wrapped multiwalled carbon nanotubes screen-printed electrode. A sandwich immunoassay was performed with CEA and alphaCEA tagged ferrocene carboxylic acid encapsulated liposomes (alphaCEA-FCL). The square wave voltammetry (SWV) was employed to analyze faradic redox responses of the released ferrocene carboxylic acid from the immunoconjugated liposomes on the electrode surface. The magnitude of the SWV peak current was directly related to the concentration of CEA. The calibration curve for CEA concentration was in the range of 5 x 10(-12) to 5 x 10(-7)gmL(-1) with a detection limit of 1 x 10(-12)gmL(-1) (S/N=3). This method provides a high precise and sensitive determination of CEA in human blood serum and saliva samples.

An ultrasensitive chemiluminescence biosensor for cholera toxin based on ganglioside-functionalized supported lipid membrane and liposome

A novel chemiluminescence biosensor based on a supported lipid layer incorporated with ganglioside GM1 was developed for the detection of cholera toxin. The planar supported lipid membrane was prepared as biosensing interface via spontaneous spread of ganglioside-incorporated phospholipid vesicles on the octadecanethiol-coated gold surface. The specific interaction of multivalent CT by ganglioside GM1 molecules enables the biosensor to be implemented via a sandwiched format using a liposome probe functionalized with GM1 and horseradish peroxidase (HRP). Then, the presence of the target CT could be determined via the HRP-catalyzed enhanced chemiluminescence reaction. The developed strategy offers several unique advantages over conventional biosensors in that it allows for an easy construction and renewal of the sensing interface, a small background signal due to low non-specific adsorption of serum constituents on the lipid membrane, and effective immobilization of multiple biocatalytic amplifiers and recognition components via common phospholipid reagents. The developed biosensor was shown to give chemiluminescence signal in linear correlation to CT concentration within the range from 1pgmL(-1) to 1ngmL(-1) with readily achievable detection limit of 0.8pgmL(-1).

A hand-held surface plasmon resonance biosensor for the detection of ricin and other biological agents

There is an ongoing need for field-deployable biosensor devices. We have constructed a fully self-contained, hand-held biosensor, based on the surface plasmon resonance technique. The dimensions of the sensor unit are 15 x 8 cm, the weight is 600 g and it is powered by a 9 V battery. We have characterised the responsiveness of the sensor using calibrated sucrose solutions and were able to measure changes as small as 3.3 x 10(-6) refractive index units. To demonstrate functionality of the sensor, we have prepared surfaces with an antibody fragment specific for the biological toxin ricin. We were able to detect ricin at 200 ng/mL in 10 min, which is approximately 2500 times less than the minimum lethal dose. We were also able to verify positive binding within a second 10 min window. This sensor demonstrates important steps required for the development of fully integrated, hand-held sensor devices and will form the basis of a multi-analyte system, to be developed in the near future. It also represents the first completely hand-held SPR device, not requiring external power or a computer connection to operate.

GM1-functionalized liposomes in a microtiter plate assay for cholera toxin in Vibrio cholerae culture samples

Vibrio cholerae, the causative agent for cholera, infects its host by expressing a protein consisting of two subunits: the pentameric cholera toxin B (CTB) and cholera toxin A (CTA). CTB frequently is used as an indicator of the presence of pathogenic V. cholerae and typically is detected using enzyme-linked immunosorbent assays (ELISAs). In lieu of an enzyme-linked detection method, we have developed GM(1) ganglioside-functionalized fluorescent dye-encapsulating liposomes for the detection of CTB produced by V. cholerae in a simple microtiter plate assay. Liposomes were compared with fluorescein-labeled antibodies and enzyme-linked secondary antibodies for quantification of purified CTB. A limit of detection for CTB using the liposomes was 340pg/ml, which was comparable to that using the ELISA but 18 times lower than that using the fluorescein-labeled anti-CTB antibodies for the same purpose. The sensitivity of the assay provided by the liposomes was substantial, and the working range improved when compared with that of the fluorescein-labeled antibodies and the ELISA. In addition, the liposomes required shorter assay times, exhibited greater precision, and were less expensive compared with the ELISA. The liposomes were optimized with respect to phospholipid and ganglioside concentrations. The optimized liposomes were then used to probe culture supernatants from V. cholerae El Tor C6706 grown in Dulbecco's modified Eagle's medium and AKI medium for the presence of CTB.