A novel piezoelectric immunoagglutination assay technique with antibody-modified liposome

Platinum-based nanocomposites loaded with MTH1 inhibitor amplify oxidative damage for cancer therapy

Photodynamic therapy (PDT) is a promising therapeutic strategy for tumor ablation by generating highly toxic reactive oxygen species (ROS) to damage DNA and other biomacromolecules. However, the local hypoxic microenvironment of the tumor and the presence of ROS-defensing system, such as the mobilization of mutt homolog 1 (MTH1) to sanitize ROS-oxidized nucleotide pool, severely limit the efficiency of PDT. Therefore, a novel tumor ablation strategy was developed that not only focused on the enhancement of ROS generation but also weakened the ROS-defensing system by inhibiting MTH1 enzyme activity. In our work, a simple one-step reduction approach was applied to enable platinum nanoparticles (Pt NPs) with catalase activity to grow in situ in the nanochannels of mesoporous silica nanoparticles (MSNs). After physical encapsulation of photosensitizer chlorin e6 (Ce6) and MTH1 inhibitor TH588, the drug loading nanoplatform was modified with an arginine-glycine-aspartic acid (RGD) functionalized liposome shell, resulting in the fabrication of amplified oxidative damage nanoplatform MSN-Pt@Ce6/TH588 @Liposome-RGD (MPCT@Li-R). The prepared MPCT@Li-R NPs could continuously catalyze the decomposition of hydrogen peroxide (H₂O₂) into oxygen (O₂) in tumor, thus promoting the generation of singlet oxygen during PDT process for improved oxidative damage of bases. Simultaneously, acid responsive released TH588 hindered MTH1-mediated scavenging of oxidative bases, further aggravating DNA oxidative damage. Consequently, this cascade therapy strategy exhibited excellent tumor suppression efficiency both in vitro and in vivo.

Nano-biotinylated liposome-based immunoassay for the ultrasensitive detection of protein biomarker in urine

With the development of proteomics and the continuous discovery of biomarkers of trace proteins, it is important to accurately quantify low abundance protein, especially in urine for clinical diagnostics. In this paper, we reported a novel nano-biotinylated liposome-based immuno-loop-mediated isothermal amplification (LI-LAMP) for the ultrasensitive detection of REG1A (a biomarker for pancreatic ductal adenocarcinoma (PDAC) in urine) with high specificity. The detection range was 1µg/mL to 1fg/mL, with a detection limit of 1fg/mL, and no cross-reactivity was observed to occur in this assay. Compared with the amount of REG1A added, REG1A recovery using this method was 130% and 89%. Detection of REG1A concentrations using the LI-LAMP assay from real samples were in good agreement with those determined using ELISA, and relative deviations were not more than 10%. LI-LAMP shows good potential as a clinical diagnostic assay.

Magnetic-Immuno-Loop-Mediated Isothermal Amplification Based on DNA Encapsulating Liposome for the Ultrasensitive Detection of P-glycoprotein

Determination of proteins, especially low-abundance proteins with high sensitivity and specificity, is essential for characterizing proteomes and studying their biochemical functions. Herein, a novel Magnetic-Immuno-Loop-Mediated Isothermal Amplification (Im-LAMP) based on DNA-encapsulating liposomes (liposome-Im- LAMP), was developed for trace amounts of proteins. To the best of our knowledge, this is our first report about the magnetic Im-LAMP approach based on liposomes encapsulated template DNA as the detection reagent. The DNA template was released from liposomes and then initiated an Im-LAMP reaction, generating the fluorescence signal with high sensitivity and rapidity. This technique was applied for the determination of P-glycoprotein as a model protein. It was demonstrated that the technique exhibited a dynamic response to P-glycoprotein ranging from 1.6*10⁻² to 160 pg/ml with a greatly low detection limit of 5*10⁻³ pg/ml (5 fg/ml) which is substantially better than conventional enzyme-linked immunosorbent assays (ELISA). This ultra sensitivity was attributed to the LAMP reaction initiated by the enormous DNA targets encapsulated in liposomes. This magnetic liposome-Im–LAMP as an alternative approach is attractive for applications in other low-abundance proteins detection in clinical diagnostics.

Liposome-amplified photoelectrochemical immunoassay for highly sensitive monitoring of disease biomarkers based on a split-type strategy

Liposomes are an excellent candidate component for biosensors to transduce and amplify detection signals due to their outstanding ability in encapsulating signal marker compounds. However, the use of liposomes for photoelectrochemical (PEC) signal transduction has not yet been achieved due the lack of appropriate sensing strategy. Herein, we report on a novel liposomes-amplified PEC immunoassay (LAPIA) method for sensitive HIV-p24 antigen (p24) detection based on a split-type strategy. Initially, liposomes were encapsulated with alkaline phosphatase (ALP) in their hydrophilic chamber and conjugated with secondary antibody on the surface to form the ALP-encapsulated liposomes (ALP-Ls) based PEC signal label. Sandwiched immunoassay based on the ALP-Ls label was then carried out in microwell plate. Upon addition of tween 20, the ALP molecules were released and catalyzed the hydrolysis of ascorbic acid 2-phosphate (AA-p) to produce ascorbic acid (AA). The latter then donated electron to the graphene/g-C₃N₄ nanohybrids based photoelectrode, arousing an increased photocurrent signal. The separation of immunoreaction step and PEC signal excitation (i.e. split-type) not only enabled the realization of liposomes based amplification strategy, but also could eliminate the PEC-caused biomolecules damage. The developed PEC method possessed a wide calibration range from 1.0pgmL^-1 to 50ngmL^-1 and a low detection limit of 0.63pgmL^-1. Its practicability was demonstrated by assaying human serum samples. Moreover, the universality of the liposomes-amplified PEC sensing strategy was also demonstrated by developing it into a sensitive microRNA detection method.

Miniaturized bioanalytical systems: enhanced performance through liposomes

Biorecognition-element labeled liposomes are simple and versatile tools used to amplify signals for the detection of analytes of environmental, clinical, food safety, and national security interest. Relying on measurement of encapsulated species via electrochemical or spectroscopic techniques, or properties inherent to liposomes themselves (such as mass, refractive index, or charge), many advances have been made in both bench-scale and microfluidic applications. Some of these measurement techniques are inherently sensitivity limited, but through the inclusion of liposomes, reduced limits of detection potentially broaden the utility towards otherwise challenging levels of analytes. Other advances took advantage of the hydrophobic environment required by many biorecognition elements to expand the target selectivity range or utilized the amphipathic nature of the lipid bilayer to provide enhanced separation capabilities. Novel handling approaches included wavelength-specific release of contents encapsulated within thermosensitive liposomes or application of electric fields to move, concentrate, and strategically lyse liposomes. These and other topics are discussed in terms of either present incorporation or adaptation to microfluidic devices.

Immunoglobulin immobilized liposomal constructs for transmucosal vaccination through nasal route

The aim of the present investigation was to evaluate the prospective of surface-engineered vesicular carriers for mucosal immunization via the nasal route. IgG antibody was immobilized on the surface of hepatitis B surface antigen (HBsAg) antigen-loaded liposomes. The developed formulations were characterized on the basis of physicochemical parameters, such as morphology, particle size, polydispersity index, entrapment efficiency, and zeta potential. Liposomal formulations were then evaluated for in-process antigen stability and storage stability. In vivo studies were conducted to visualize targeting potential, localization pattern, and immunogenicity. In addition, immune response was compared with alum-HBsAg vaccine injected intramuscularly. The serum anti-HBsAg titer, obtained from the postnasal administration of IgG-coupled liposomes, was significantly higher than plain liposomes. Moreover, IgG-coupled liposomes generated both humoral (i.e., systemic and mucosal) and cellular immune responses upon nasal administration, while the alum-adsorbed antigen displayed neither cellular (cytokine level) nor mucosal (IgA) response. The formulation also displayed enhanced transmucosal transport, improved in vitro stability, and effective immunoadjuvant property. To conclude, IgG antibody-coupled liposomes may serve as novel carriers to augment the secretory immune response of antigen encapsulated in the liposomes, apparently by escalating liposome uptake via M cells, thereby rationalizing their use as a carrier adjuvant for nasal subunit vaccines.

Construction of supported lipid membrane modified piezoelectric biosensor for sensitive assay of cholera toxin based on surface-agglutination of ganglioside-bearing liposomes

A novel piezoelelctric biosensor has been developed for cholera toxin (CT) detection based on the analyte-mediated surface-agglutination of ganglioside (GM1)-functionalized liposomes. To achieve a CT-specific agglutination at the surface, the gold electrode is modified by a GM1-functionalized supported lipid membrane via spontaneous spread of the liposomes on a self-assembled monolayer of a long-chain alkanethiol. In the presence of CT, the GM1-incorporated liposomes in assay medium will rapidly specifically agglutinate at the electrode surface through the binding of CT to GM1 on the electrode surface and the liposome interface. This results in an enormous mass loading on the piezoelelctric crystal as well as a significant increase of density and viscosity at the interface, thereby generating a decrease in frequency of the piezoelelctric crystal. The combination of mass loading with interfacial change in the surface-agglutination reaction allows the developed piezoelelctric biosensor to show substantial signal amplification in response to the analyte CT. The detection limit can be achieved as low as 25 ng mL(-1) CT. This is the first demonstration on CT detection based on specific surface-agglutination of GM1-modified liposomes. The supported lipid layer based sensing interface can be prepared readily and renewably, making the developed technique especially useful for simple, reusable and sensitive determination of proteins.

A multipurpose capacitive biosensor for assay and quality control of human immunoglobulin G

We report a flow-injection biosensor system with a capacitive transducer for assay and quality control of human immunoglobulin G (hIgG). The sensing platform is based on self-assembled monolayers (SAMs) of carboxylic acid terminated alkyl-thiols with covalently attached concanavalin A. The electrochemical characteristics of the sensor surface were assessed by cyclic voltammetry using a permeable redox couple (potassium ferricyanide). The developed biosensor proved capable of performing a sensitive label-free assay of hIgG with a detection limit of 1.0 microg mL(-1). The capacitance response depended linearly on hIgG concentration over the range from 5.0 to 100 microg mL(-1), in a logarithmic plot. Typical measurements were performed in 15 min and up to 18 successive assays were achieved without significant loss of sensitivity using a single electrode. In addition, the biosensor can detect hIgG aggregates with concentrations as low as 0.01% of the total hIgG content (5.0 microg mL(-1)). Hence, it represents a potential post-size-exclusion chromatography-UV (post-SEC-UV) binding assay for in-process quality control of hIgG, which cannot be detected by SEC-UV singly at concentrations below 0.3% of the total hIgG content.

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).

Nanomaterial labels in electrochemical immunosensors and immunoassays

This article reviews recent advances in nanomaterial labels in electrochemical immunosensors and immunoassays. Various nanomaterial labels are discussed, including colloidal gold/silver, semiconductor nanoparticles, and markers loaded nanocarriers (carbon nanotubes, apoferritin, silica nanoparticles, and liposome beads). The enormous signal enhancement associated with the use of nanomaterial labels and with the formation of nanomaterial-antibody-antigen assemblies provides the basis for ultrasensitive electrochemical detection of disease-related protein biomarkers, biothreat agents, or infectious agents. In general, all endeavors cited here are geared to achieve one or more of the following goals: signal amplification by several orders of magnitude, lower detection limits, and detecting multiple targets.