Tobacco mosaic virus adsorption on self-assembled and Langmuir-Blodgett monolayers studied by TIRF and SFM

A Novel Platform for Root Protection Applies New Root-Coating Technologies to Mitigate Soil-Borne Tomato Brown Rugose Fruit Virus Disease

Tomato brown rugose fruit virus (ToBRFV) is a soil-borne virus showing a low percentage of ca. 3% soil-mediated infection when the soil contains root debris from a previous 30–50 day growth cycle of ToBRFV-infected tomato plants. We designed stringent conditions of soil-mediated ToBRFV infection by increasing the length of the pre-growth cycle to 90–120 days, adding a ToBRFV inoculum as well as truncating seedling roots, which increased seedling susceptibility to ToBRFV infection. These rigorous conditions were employed to challenge the efficiency of four innovative root-coating technologies in mitigating soil-mediated ToBRFV infection while avoiding any phytotoxic effect. We tested four different formulations, which were prepared with or without the addition of various virus disinfectants. We found that under conditions of 100% soil-mediated ToBRFV infection of uncoated positive control plants, root-coating with formulations based on methylcellulose (MC), polyvinyl alcohol (PVA), silica Pickering emulsion and super-absorbent polymer (SAP) that were prepared with the disinfectant chlorinated-trisodium phosphate (Cl-TSP) showed low percentages of soil-mediated ToBRFV infection of 0%, 4.3%, 5.5% and 0%, respectively. These formulations had no adverse effect on plant growth parameters when compared to negative control plants grown under non ToBRFV inoculation conditions.

A Roadmap for Building Waterborne Virus Traps

Outbreaks of waterborne viruses pose a massive threat to human health, claiming the lives of hundreds of thousands of people every year. Adsorption-based filtration offers a promising facile and environmentally friendly approach to help provide safe drinking water to a world population of almost 8 billion people, particularly in communities that lack the infrastructure for large-scale facilities. The search for a material that can effectively trap viruses has been mainly driven by a top-down approach, in which old and new materials have been tested for this purpose. Despite substantial advances, finding a material that achieves this crucial goal and meets all associated challenges remains elusive. We suggest that the road forward should strongly rely on a complementary bottom-up approach based on our fundamental understanding of virus interactions at interfaces. We review the state-of-the-art physicochemical knowledge of the forces that drive the adsorption of viruses at solid-water interfaces. Compared to other nanometric colloids, viruses have heterogeneous surface chemistry and diverse morphologies. We advocate that advancing our understanding of virus interactions would require describing their physicochemical properties using novel descriptors that reflect their heterogeneity and diversity. Several other related topics are also addressed, including the effect of coadsorbates on virus adsorption, virus inactivation at interfaces, and experimental considerations to ensure well-grounded research results. We finally conclude with selected examples of materials that made notable advances in the field.

An automatic fluorescence phenotyping platform to evaluate dynamic infection process of Tobacco mosaic virus-green fluorescent protein in tobacco leaves

Tobacco is one of the important economic crops all over the world. Tobacco mosaic virus (TMV) seriously affects the yield and quality of tobacco leaves. The expression of TMV in tobacco leaves can be analyzed by detecting green fluorescence-related traits after inoculation with the infectious clone of TMV-GFP (Tobacco mosaic virus - green fluorescent protein). However, traditional methods for detecting TMV-GFP are time-consuming and laborious, and mostly require a lot of manual procedures. In this study, we develop a low-cost machine-vision-based phenotyping platform for the automatic evaluation of fluorescence-related traits in tobacco leaf based on digital camera and image processing. A dynamic monitoring experiment lasting 7 days was conducted to evaluate the efficiency of this platform using Nicotiana tabacum L. with a total of 14 samples, including the wild-type strain SR1 and 4 mutant lines generated by RNA interference technology. As a result, we found that green fluorescence area and brightness generally showed an increasing trend over time, and the trends were different among these SR1 and 4 mutant lines samples, where the maximum and minimum of green fluorescence area and brightness were mutant-4 and mutant-1 respectively. In conclusion, the platform can full-automatically extract fluorescence-related traits with the advantage of low-cost and high accuracy, which could be used in detecting dynamic changes of TMV-GFP in tobacco leaves.

Fighting viruses with materials science: Prospects for antivirus surfaces, drug delivery systems and artificial intelligence

OBJECTIVE

Viruses on environmental surfaces, in saliva and other body fluids represent risk of contamination for general population and healthcare professionals. The development of vaccines and medicines is costly and time consuming. Thus, the development of novel materials and technologies to decrease viral availability, viability, infectivity, and to improve therapeutic outcomes can positively impact the prevention and treatment of viral diseases.

METHODS

Herein, we discuss (a) interaction mechanisms between viruses and materials, (b) novel strategies to develop materials with antiviral properties and oral antiviral delivery systems, and (c) the potential of artificial intelligence to design and optimize preventive measures and therapeutic regimen.

RESULTS

The mechanisms of viral adsorption on surfaces are well characterized but no major breakthrough has become clinically available. Materials with fine-tuned physical and chemical properties have the potential to compromise viral availability and stability. Emerging strategies using oral antiviral delivery systems and artificial intelligence can decrease infectivity and improve antiviral therapies.

SIGNIFICANCE

Emerging viral infections are concerning due to risk of mortality, as well as psychological and economic impacts. Materials science emerges for the development of novel materials and technologies to diminish viral availability, infectivity, and to enable enhanced preventive and therapeutic strategies, for the safety and well-being of humankind.

Tuning fluorophore excitation in a total-internal-reflection-fluorescence microscopy

In a total-internal-reflection-fluorescence-microscopy method, there is anisotropy in the polarized evanescent wave. Since the evanescent wave is used as an excitation field, the mentioned anisotropy is a disadvantage in using the total-internal-reflection-fluorescence-microscopy technique. Therefore, by theoretical and analytical approaches, and based on the Fresnel coefficients, the effect of three dielectrics media on the anisotropy of the evanescent wave is investigated. Following that, a proper combination of the cover glass, oil immersion, and prism for both living and non-living samples is suggested that not only enhances the intensity of the evanescent wave, but also and importantly, decreases the essential anisotropy of the evanescent wave.

Virus-Like Particle Facilitated Deposition of Hydroxyapatite Bone Mineral on Nanocellulose after Exposure to Phosphate and Calcium Precursors

We produced and isolated tobacco mosaic virus-like particles (TMV VLPs) from bacteria, which are devoid of infectious genomes, and found that they have a net negative charge and can bind calcium ions. Moreover, we showed that the TMV VLPs could associate strongly with nanocellulose slurry after a simple mixing step. We sequentially exposed nanocellulose alone or slurries mixed with the TMV VLPs to calcium and phosphate salts and utilized physicochemical approaches to demonstrate that bone mineral (hydroxyapatite) was deposited only in nanocellulose mixed with the TMV VLPs. The TMV VLPs confer mineralization properties to the nanocellulose for the generation of new composite materials.

Aggregate Size Dependence of Amyloid Adsorption onto Charged Interfaces

Amyloid aggregates are associated with a range of human neurodegenerative disorders, and it has been shown that neurotoxicity is dependent on aggregate size. Combining molecular simulation with analytical theory, a predictive model is proposed for the adsorption of amyloid aggregates onto oppositely charged surfaces, where the interaction is governed by an interplay between electrostatic attraction and entropic repulsion. Predictions are experimentally validated against quartz crystal microbalance-dissipation experiments of amyloid beta peptides and fragmented fibrils in the presence of a supported lipid bilayer. Assuming amyloids as rigid, elongated particles, we observe nonmonotonic trends for the extent of adsorption with respect to aggregate size and preferential adsorption of smaller aggregates over larger ones. Our findings describe a general phenomenon with implications for stiff polyions and rodlike particles that are electrostatically attracted to a surface.

Competitive Coadsorption Dynamics of Viruses and Dissolved Organic Matter to Positively Charged Sorbent Surfaces

Adsorption onto solid-water interfaces is a key process governing the fate and transport of waterborne viruses. Although negatively charged viruses are known to extensively adsorb onto positively charged adsorbent surfaces, virus adsorption in such systems in the presence of negatively charged dissolved organic matter (DOM) as coadsorbate remains poorly studied and understood. This work provides a systematic assessment of the adsorption dynamics of negatively charged viruses (i.e., bacteriophages MS2, fr, GA, and Qβ) and polystyrene nanospheres onto a positively charged model sorbent surface in the presence of varying DOM concentrations. In all systems studied, DOM competitively suppressed the adsorption of the viruses and nanospheres onto the model surface. Electrostatic repulsion of the highly negatively charged MS2, fr, and the nanospheres impaired their adsorption onto DOM adlayers that formed during the coadsorption process. In contrast, the effect of competition on overall adsorption was attenuated for less-negatively charged GA and Qβ because these viruses also adsorbed onto DOM adlayer surfaces. Competition in MS2-DOM coadsorbate systems were accurately described by a random sequential adsorption model that explicitly accounts for the unfolding of adsorbed DOM. Consistent findings for viruses and nanospheres suggest that the coadsorbate effects described herein generally apply to systems containing negatively charged nanoparticles and DOM.

Viruses at Solid-Water Interfaces: A Systematic Assessment of Interactions Driving Adsorption

Adsorption to solid-water interfaces is a major process governing the fate of waterborne viruses in natural and engineered systems. The relative contributions of different interaction forces to adsorption and their dependence on the physicochemical properties of the viruses remain, however, only poorly understood. Herein, we systematically studied the adsorption of four bacteriophages (MS2, fr, GA, and Qβ) to five model surfaces with varying surface chemistries and to three dissolved organic matter adlayers, as a function of solution pH and ionic strength, using quartz crystal microbalance with dissipation monitoring. The viruses were selected to have similar sizes and shapes but different surface charges, polarities, and topographies, as identified by modeling the distributions of amino acids in the virus capsids. Virus-sorbent interactions were governed by long-ranged electrostatics and favorable contributions from the hydrophobic effect, and shorter-ranged van der Waals interactions were of secondary importance. Steric effects depended on the topographic irregularities on both the virus and sorbent surfaces. Differences in the adsorption characteristics of the tested viruses were successfully linked to differences in their capsid surface properties. Besides identifying the major interaction forces, this work highlights the potential of computable virus surface charge and polarity descriptors to predict virus adsorption to solid-water interfaces.

Directed Growth of Virus Nanofilaments on a Superhydrophobic Surface

The evaporation of single droplets of colloidal tobacco mosaic virus (TMV) nanoparticles on a superhydrophobic surface with a hexagonal pillar-pattern results in the formation of coffee-ring type residues. We imaged surface features by optical, scanning electron, and atomic force microscopies. Bulk features were probed by raster-scan X-ray nanodiffraction. At ∼100 pg/μL nanoparticle concentration, the rim of the residue connects to neighboring pillars via fibrous extensions containing flow-aligned crystalline domains. At ∼1 pg/μL nanoparticle concentration, nanofilaments of ≥80 nm diameter and ∼20 μm length are formed, extending normal to the residue-rim across a range of pillars. X-ray scattering is dominated by the nanofilament form-factor but some evidence for crystallinity has been obtained. The observation of sheets composed of stacks of self-assembled nanoparticles deposited on pillars suggests that the nanofilaments are drawn from a structured droplet interface.

Atomic force microscopy analysis of the Acinetobacter baumannii bacteriophage AP22 lytic cycle

Background

Acinetobacter baumannii is known for its ability to develop resistance to the major groups of antibiotics, form biofilms, and survive for long periods in hospital environments. The prevalence of infections caused by multidrug-resistant A. baumannii is a significant problem for the modern health care system, and application of lytic bacteriophages for controlling this pathogen may become a solution.

Methodology/Principal Findings

In this study, using atomic force microscopy (AFM) and microbiological assessment we have investigated A. baumannii bacteriophage AP22, which has been recently described. AFM has revealed the morphology of bacteriophage AP22, adsorbed on the surfaces of mica, graphite and host bacterial cells. Besides, morphological changes of bacteriophage AP22-infected A. baumannii cells were characterized at different stages of the lytic cycle, from phage adsorption to the cell lysis. The phage latent period, estimated from AFM was in good agreement with that obtained by microbiological methods (40 min). Bacteriophage AP22, whose head diameter is 62±1 nm and tail length is 88±9 nm, was shown to disperse A. baumannii aggregates and adsorb to the bacterial surface right from the first minute of their mutual incubation at 37°C.

Conclusions/Significance

High rate of bacteriophage AP22 specific adsorption and its ability to disperse bacterial aggregates make this phage very promising for biomedical antimicrobial applications. Complementing microbiological results with AFM data, we demonstrate an effective approach, which allows not only comparing independently obtained characteristics of the lytic cycle but also visualizing the infection process.

Inducible site-selective bottom-up assembly of virus-derived nanotube arrays on RNA-equipped wafers

Tobacco mosaic virus (TMV) is a tube-shaped, exceptionally stable plant virus, which is among the biomolecule complexes offering most promising perspectives for nanotechnology applications. Every viral nanotube self-assembles from a single RNA strand and numerous identical coat protein (CP) subunits. Here we demonstrate that biotechnologically engineered RNA species containing the TMV origin of assembly can be selectively attached to solid surfaces via one end and govern the bottom-up growth of surface-linked TMV-like nanotubes in situ on demand. SiO(2) wafers patterned by polymer blend lithography were modified in a chemically selective manner, which allowed positioning of in vitro produced RNA scaffolds into predefined patches on the 100-500 nm scale. The RNA operated as guiding strands for the self-assembly of spatially ordered nanotube 3D arrays on the micrometer scale. This novel approach may promote technically applicable production routes toward a controlled integration of multivalent biotemplates into miniaturized devices to functionalize poorly accessible components prior to use. Furthermore, the results mark a milestone in the experimental verification of viral nucleoprotein complex self-assembly mechanisms.

Determining Surface Plasmon Resonance Response Factors for Deposition onto Three-Dimensional Surfaces

Intrinsic sorption rates of ligand/receptor binding have been measured by surface plasmon resonance (SPR) using response factors for deposition of proteins or smaller molecules on planar surfaces. In this study generalized expressions for SPR response factor and effective refractive index are developed to measure rates of analyte sorption onto 3-D surfaces. The expressions are specialized for two limiting cases of immediate practical interest and broad applicability: analyte deposition onto a homogeneous anisotropic porous media and deposition onto close-packed solid spheres adjacent to the sensor surface. These new equations specify media capacity, characteristic size and analyte concentration that are necessary to obtain identifiable responses from interaction with anisotropic porous media or chromatographic resin. These developments are illustrated by comparing response factors for Adenovirus Type 5 on planar surfaces, porous media and adsorptive spheres.

Adenovirus type 5 intrinsic adsorption rates measured by surface plasmon resonance

Intrinsic adsorption rates of whole adenovirus type 5 (Ad5) onto a diethylaminoethyl (DEAE) anion exchange surface are measured for the first time by surface plasmon resonance (SPR). Fitting SPR sensorgrams to a two-compartment mass transport reaction model distinguishes intrinsic adsorption rates from slow diffusive Ad5 mass transport. Ad5 is a widely used viral vector for gene therapy that binds electrostatically to surfaces of cells and synthetics such as membranes, chromatographic resins, and glass. Increasing NaCl concentration from 4.8 to 14.4mM shifts binding of whole Ad5 from diffusion control to a regime where both sorption and diffusion affect binding. Intrinsic adsorption rates for Ad5-DEAE interaction are 16 times faster than intrinsic adsorption rates for Ad5 fiber knob interacting with soluble extracellular domain of coxsackievirus adenovirus receptors (s-CAR).