Virus assay using antibody-functionalized peptide nanotubes

Designer peptides as versatile building blocks for functional materials

Peptides and pseudopeptides show distinct self-assembled nanostructures such as fibers, nanotubes, vesicles, micelles, toroids, helices and rods. The formation of such molecular communities through the collective behavior of molecules is not fully understood at a molecular level. All these self-assembled nanostructured materials have a wide range of applications such as drug delivery, gene delivery, biosensing, bioimaging, catalysis, tissue engineering, nano-electronics and sensing. Self-assembly is one of the most efficient and a simple strategy to generate complex functional materials. Owing to its significance, the last few decades witnessed a remarkable advancement in the field of self-assembling peptides with a plethora of new designer synthetic systems being discovered. These systems range from amphiphilic, cyclic, linear and polymeric peptides. This article presents only selected examples of such self-assembling peptides and pseudopeptides.

Short peptide based self-assembled nanostructures: implications in drug delivery and tissue engineering

Self-assembling peptides with many potential biomedical applications.

Multifunctional electrochemical aptasensor for aptamer clones screening, virus quantitation in blood and viability assessment

A novel attempt was made to develop a disposable multifunctional sensor for analysis of vaccinia virus (VACV), a promising oncolytic agent that can replicate in and kill tumor cells. Briefly, we developed aptamers specific to VACV that were negatively selected against human serum as well as human and mouse blood to be further utilized for viral analysis directly in serum and blood. In addition, the aptamers were negatively selected against heat-inactivated VACV to enable them to distinguish between viable and nonviable virus particles. The selected aptamers were integrated onto an electrochemical aptasensor to perform multiple functions, including quantification of VACV, viability assessment of the virus, and estimation of the binding affinity between the virus and the developed aptamers. The aptasensor was fabricated by self-assembling a hybrid of a thiolated ssDNA primer and a VACV-specific aptamer onto a gold nanoparticles modified screen-printed carbon electrode (GNPs-SPCE). Square wave voltammetry was employed to quantify VACV in serum and blood within the range of 150-900 PFU, with a detection limit of 60 PFU in 30 μL. According to the electrochemical affinity measurements, three virus specific aptamer clones, V-2, V-5, and V-9 exhibited the highest affinity to VACV. Furthermore, flow cytometry was employed to estimate the dissociation constants of the clones which were found to be 26.3, 40.9, and 24.7 nM, respectively. Finally, the developed aptasensor was able to distinguish between the intact virus and the heat-inactivated virus thanks to the tailored selectivity of the aptamers that was achieved via negative selection.

Fabrication of ellagic acid incorporated self-assembled peptide microtubes and their applications

Ellagic acid (EA), a plant polyphenol known for its wide-range of health benefits was encapsulated within self-assembled threonine based peptide microtubes. The microtubes were assembled using the synthesized precursor bolaamphiphile bis(N-α-amido threonine)-1,5-pentane dicarboxylate. The self-assembly of the microstructures was probed at varying pH. In general, tubular formations were observed at a pH range of 4-6. The formed microtubes were then utilized for fabrication with EA. We probed the ability of the microtubes as drug release vehicles for EA as well as for antibacterial applications. It was found that the release of EA was both pH and concentration dependent. The biocompatibility as well as cytotoxicity of the EA-fabricated microtubes was examined in the presence of mammalian normal rat kidney (NRK) cells. Finally the antibacterial effects of the EA incorporated peptide microtubes was examined against Escherichia coli and Staphylococcus aureus.

Antibody-mediated self-limiting self-assembly for quantitative analysis of nanoparticle surfaces by atomic force microscopy

Quantification of very low density molecular coatings on large (60 nm) gold nanoparticles (AuNPs) is demonstrated via the use of antibody-mediated self-limiting self-assembly of small and large AuNPs into raspberry-like structures subsequently imaged by atomic force microscopy (AFM). AFM imaging is proposed as an automated, lower-cost, higher-throughput alternative to immunostaining and imaging by transmission electron microscopy. Synthesis of large AuNPs, containing one of three ligand molecules in one of three stoichiometries (1, 2, or 10 ligands per AuNP), and small probe AuNPs with one of three antibody molecules in a one antibody per AuNP ratio, enabled a range of predicted self-limiting self-assembled structures. A model predicting the probability of observing a given small to large AuNP ratio based on a topography measurement such as AFM is described, in which random orientational deposition is assumed and which accounts for the stochastic synthesis method of the library AuNPs with varied ligand ratios. Experimental data were found to agree very well with the predictive models when using an established AFM sample preparation method that avoids drying-induced aggregation.

Assemblies of Functional Peptides and Their Applications in Building Blocks for Biosensors

We highlight our recent applications of functional peptide nanotubes, self-assembled from short peptides with recognition elements, as building blocks to develop sensors. Peptide nanotubes with high aspect ratios are excellent building blocks for directed assembly into device configurations, and their combining structures with the nanometric diameters and the micrometric lengths enables to bridge the nano-world and the micro-world.

Challenges for physical characterization of silver nanoparticles under pristine and environmentally relevant conditions

The reported size distribution of silver nanoparticles (AgNPs) is strongly affected by the underlying measurement method, agglomeration state, and dispersion conditions. A selection of AgNP materials with vendor-reported diameters ranging from 1 nm to 100 nm, various size distributions, and biocompatible capping agents including citrate, starch and polyvinylpyrrolidone were studied. AgNPs were diluted with either deionized water, moderately hard reconstituted water, or moderately hard reconstituted water containing natural organic matter. Rigorous physico-chemical characterization by consensus methods and protocols where available enables an understanding of how the underlying measurement method impacts the reported size measurements, which in turn provides a more complete understanding of the state (size, size distribution, agglomeration, etc.) of the AgNPs with respect to the dispersion conditions. An approach to developing routine screening is also presented.

Bioaffinity detection of pathogens on surfaces

The demand for improved technologies capable of rapidly detecting pathogens with high sensitivity and selectivity in complex environments continues to be a significant challenge that helps drive the development of new analytical techniques. Surface-based detection platforms are particularly attractive as multiple bioaffinity interactions between different targets and corresponding probe molecules can be monitored simultaneously in a single measurement. Furthermore, the possibilities for developing new signal transduction mechanisms alongside novel signal amplification strategies are much more varied. In this article, we describe some of the latest advances in the use of surface bioaffinity detection of pathogens. Three major sections will be discussed: (i) a brief overview on the choice of probe molecules such as antibodies, proteins and aptamers specific to pathogens and surface attachment chemistries to immobilize those probes onto various substrates, (ii) highlighting examples among the current generation of surface biosensors, and (iii) exploring emerging technologies that are highly promising and likely to form the basis of the next generation of pathogenic sensors.