Long term storage of virus templated fluorescent materials for sensing applications

Cold-Responsive Nanoparticle Enables Intracellular Delivery and Rapid Release of Trehalose for Organic-Solvent-Free Cryopreservation

Conventional cryopreservation of mammalian cells requires the use of toxic organic solvents (e.g., dimethyl sulfoxide) as cryoprotectants. Consequently, the cryopreserved cells must undergo a tedious washing procedure to remove the organic solvents for their further applications in cell-based medicine, and many of the precious cells may be lost or killed during the procedure. Trehalose has been explored as a nontoxic alternative to traditional cryoprotectants. However, mammalian cells do not synthesize trehalose or express trehalose transporters in their membranes, and the lack of an approach for the efficient intracellular delivery of trehalose has been a major hurdle for its use in cell cryopreservation. In this study, a cold-responsive polymer (poly(N-isopropylacrylamide-co-butyl acrylate)) is utilized to synthesize nanoparticles for the encapsulation and intracellular delivery of trehalose. The trehalose-laden nanoparticles can be efficiently taken up by mammalian cells. The nanoparticles quickly and irreversibly disassemble upon cold treatment, enabling the controlled and rapid release of trehalose from the nanoparticles inside cells. The latter is confirmed by an evident increase in cell volume upon cold treatment. This rapid cold-triggered intracellular release of trehalose is crucial to developing a fast protocol to cryopreserve cells using trehalose. Cells with intracellular trehalose delivered using the nanoparticles show comparable postcryopreservation viability compared to that of cells treated with DMSO, eliminating the need for the tedious and cell-damaging washing procedure required for using the DMSO-cryopreserved cells in vivo. This cold-responsive nanoparticle may greatly facilitate the use of trehalose as a nontoxic cryoprotectant for banking cells and tissues to meet their high demand by modern cell-based medicine.

Application of Plant Viruses as a Biotemplate for Nanomaterial Fabrication

Viruses are widely used to fabricate nanomaterials in the field of nanotechnology. Plant viruses are of great interest to the nanotechnology field because of their symmetry, polyvalency, homogeneous size distribution, and ability to self-assemble. This homogeneity can be used to obtain the high uniformity of the templated material and its related properties. In this paper, the variety of nanomaterials generated in rod-like and spherical plant viruses is highlighted for the cowpea chlorotic mottle virus (CCMV), cowpea mosaic virus (CPMV), brome mosaic virus (BMV), and tobacco mosaic virus (TMV). Their recent studies on developing nanomaterials in a wide range of applications from biomedicine and catalysts to biosensors are reviewed.

Icosahedral plant viral nanoparticles - bioinspired synthesis of nanomaterials/nanostructures

Viral nanotechnology utilizes virus nanoparticles (VNPs) and virus-like nanoparticles (VLPs) of plant viruses as highly versatile platforms for materials synthesis and molecular entrapment that can be used in the nanotechnological fields, such as in next-generation nanoelectronics, nanocatalysis, biosensing and optics, and biomedical applications, such as for targeting, therapeutic delivery, and non-invasive in vivo imaging with high specificity and selectivity. In particular, plant virus capsids provide biotemplates for the production of novel nanostructured materials with organic/inorganic moieties incorporated in a very precise and controlled manner. Interestingly, capsid proteins of spherical plant viruses can self-assemble into well-organized icosahedral three-dimensional (3D) nanoscale multivalent architectures with high monodispersity and structural symmetry. Using viral genetic and protein engineering of icosahedral viruses with a variety of sizes, the interior, exterior and the interfaces between coat protein (CP) subunits can be manipulated to fabricate materials with a wide range of desirable properties allowing for biomineralization, encapsulation, infusion, controlled self-assembly, and multivalent ligand display of nanoparticles or molecules for varied applications. In this review, we discuss the various functional nanomaterials/nanostructures developed using the VNPs and VLPs of different icosahedral plant viruses and their nano(bio)technological and nanomedical applications.

Nanoparticle-mediated intracellular delivery enables cryopreservation of human adipose-derived stem cells using trehalose as the sole cryoprotectant

In this study, pH responsive genipin-cross-linked Pluronic F127-chitosan nanoparticles (GNPs) was synthesized to encapsulate trehalose for intracellular delivery to cryopreserve primary human adipose-derived stem cells (hADSCs). Trehalose is a disaccharide of glucose used by lower organisms to survive extreme cold in nature and has been used to cryopreserve various biomacromolecules. However, it does not enter mammalian cells because of its highly hydrophilic nature, and has only been used in combination with other cell-penetrating cryoprotectants (such as dimethyl sulfoxide, DMSO) to cryopreserve mammalian cells. Our data show that trehalose can be efficiently encapsulated in our GNPs for intracellular delivery, which enables cryopreservation of primary hADSCs using the nontoxic sugar as the sole cryoprotectant. This capability is important because the conventional approach of cryopreserving mammalian cells using highly toxic (at body temperature) cell-penetrating cryoprotectants requires multistep washing of the cryopreserved cells to remove the toxic cryoprotectant for further use, which is time-consuming and associated with significant cell loss (∼10% during each washing step). By contrast, the trehalose-cryopreserved cells can be used without washing, which should greatly facilitate the wide application of the burgeoning cell-based medicine.

A programmable fluorescent viral nanoblock: sensing made easy in a single step

Viral nanoblock provides specific positioning of recognition moieties and dye molecules which can be used as a signal-generating element and enhance detection sensitivity. The methods described herein use a 30 nm viral nanoblock to couple a variety of proteins and peptides for the incorporation of recognition elements along with a large number of dye molecules (200). The bioconjugation techniques were adapted and optimized over the years to fabricate nanoparticles that exhibit high fluorescence output while maintaining the selectivity of the target receptors. These complexes can be used for the detection of pathogens and toxins in a single step since both receptor and reporter are in the same viral nanoblock. Its stability and nanometer size allows for its utilization in well-established sensing platforms like microarrays.

Virus hybrids as nanomaterials for biotechnology

The current review describes advances in the field of bionanotechnology in which viruses are used to fabricate nanomaterials. Viruses are introduced as protein cages, scaffolds, and templates for the production of biohybrid nanostructured materials where organic and inorganic molecules are incorporated in a precise and a controlled fashion. Genetic engineering enables the insertion or replacement of selected amino acids on virus capsids for uses from bioconjugation to crystal growth. The variety of nanomaterials generated in rod-like and spherical viruses is highlighted for tobacco mosaic virus (TMV), M13 bacteriophage, cowpea chlorotic mottle virus (CCMV), and cowpea mosaic virus (CPMV). Functional biohybrid nanomaterials find applications in biosensing, memory devices, nanocircuits, light-harvesting systems, and nanobatteries.

Viruses and their potential in bioimaging and biosensing applications

Successful development of ultrasensitive constructs for bioimaging and biosensing is a challenging task. Recently, viruses have drawn increasing attention due to their exquisite three-dimensional structures and unique properties, including multivalency, orthogonal reactivities, and responsiveness to genetic modifications. With such well-characterized structures, functional units, such as imaging and binding motifs, can be engineered on the surface of viruses in a programmable, polyvalent manner, which leads to novel nanosized sensing/imaging systems with enhanced signaling and targeting performance. This review highlights some recent progress in the applications of viruses in bioimaging and biosensing.

"Smart dust" biosensors powered by biomolecular motors

The concept of a microfabricated biosensor for environmental and biomedical monitoring applications which is composed of environmentally benign components is presented. With a built-in power source (the biological fuel ATP) and driven by biological motors (kinesin), sensing in the microdevice can be remotely activated and the presence of a target molecule or toxin remotely detected. The multifaceted progress towards the realization of such a device is described.