Multifaceted applications of nanomaterials in cell engineering and therapy

Nanomaterials with superior physiochemical properties have been rapidly developed and integrated in every aspect of cell engineering and therapy for translating their great promise to clinical success. Here we demonstrate the multifaceted roles played by innovatively-designed nanomaterials in addressing key challenges in cell engineering and therapy such as cell isolation from heterogeneous cell population, cell instruction in vitro to enable desired functionalities, and targeted cell delivery to therapeutic sites for prompting tissue repair. The emerging trends in this interdisciplinary and dynamic field are also highlighted, where the nanomaterial-engineered cells constitute the basis for establishing in vitro disease model; and nanomaterial-based in situ cell engineering are accomplished directly within the native tissue in vivo. We will witness the increasing importance of nanomaterials in revolutionizing the concept and toolset of cell engineering and therapy which will enrich our scientific understanding of diseases and ultimately fulfill the therapeutic demand in clinical medicine.     

Texture perception through direct and indirect touch: An analysis of perceptual space for tactile textures in two modes of exploration

Considerable information about the texture of objects can be perceived remotely through a probe. It is not clear, however, how texture perception with a probe compares with texture perception with the bare finger. Here we investigate the perception of a variety of textured surfaces encountered daily (e.g., corduroy, paper, and rubber) using the two scanning modes—direct touch through the finger and indirect touch through a probe held in the hand—in two tasks. In the first task, subjects rated the overall pair-wise dissimilarity of the textures. In the second task, subjects rated each texture along three continua, namely, perceived roughness, hardness, and stickiness of the surfaces, shown previously as the primary dimensions of texture perception in direct touch. From the dissimilarity judgment experiment, we found that the texture percept is similar though not identical in the two scanning modes. From the adjective rating experiments, we found that while roughness ratings are similar, hardness and stickiness ratings tend to differ between scanning conditions. These differences between the two modes of scanning are apparent in perceptual space for tactile textures based on multidimensional scaling (MDS) analysis. Finally, we demonstrate that three physical quantities, vibratory power, compliance, and friction carry roughness, hardness, and stickiness information, predicting perceived dissimilarity of texture pairs with indirect touch. Given that different types of texture information are processed by separate groups of neurons across direct and indirect touch, we propose that the neural mechanisms underlying texture perception differ between scanning modes.     

An estuarine species of the alga Vaucheria (Xanthophyceae) displays an increased capacity for turgor regulation when compared to a freshwater species

Turgor regulation is the process by which walled organisms alter their internal osmotic potential to adapt to osmotic changes in the environment. Apart from a few studies on freshwater oomycetes, the ability of stramenopiles to turgor regulate has not been investigated. In this study, turgor regulation and growth were compared in two species of the stramenopile alga Vaucheria, Vaucheria erythrospora isolated from an estuarine habitat, and Vaucheria repens isolated from a freshwater habitat. Species were identified using their rbcL sequences and respective morphologies. Using a single cell pressure probe to directly measure turgor in Vaucheria after hyperosmotic shock, V. erythrospora was found to recover turgor after a larger shock than V. repens. Threshold shock values for this ability were >0.5 MPa for V. erythrospora and <0.5 MPa for V. repens. Recovery was more rapid in V. erythrospora than V. repens after comparable shocks. Turgor recovery in V. erythrospora was inhibited by Gd³⁺ and TEA, suggesting a role for mechanosensitive channels, nonselective cation channels, and K⁺ channels in the process. Growth studies showed that V. erythrospora was able to grow over a wider range of NaCl concentrations. These responses may underlie the ability of V. erythrospora to survive in an estuarine habitat and restrict V. repens to freshwater. The fact that both species can turgor regulate may indicate a fundamental difference between members of the Stramenopila, as research to date on oomycetes suggests they are unable to turgor regulate.     

Constitutive expression of fluorescent protein by Aspergillus var. niger and Aspergillus carbonarius to monitor fungal colonization in maize plants

Aspergillus niger and Aspergillus carbonarius are two species in the Aspergillus section Nigri (black-spored aspergilli) frequently associated with peanut (Arachis hypogea), maize (Zea mays), and other plants as pathogens. These infections are symptomless and as such are major concerns since some black aspergilli produce important mycotoxins, ochratoxins A, and the fumonisins. To facilitate the study of the black aspergilli–maize interactions with maize during the early stages of infections, we developed a method that used the enhanced yellow fluorescent protein (eYFP) and the monomeric red fluorescent protein (mRFP₁) to transform A. niger and A. carbonarius, respectively. The results were constitutive expressions of the fluorescent genes that were stable in the cytoplasms of hyphae and conidia under natural environmental conditions. The hyphal in planta distribution in 21-day-old seedlings of maize were similar wild type and transformants of A. niger and A. carbonarius. The in planta studies indicated that both wild type and transformants internally colonized leaf, stem and root tissues of maize seedlings, without any visible disease symptoms. Yellow and red fluorescent strains were capable of invading epidermal cells of maize roots intercellularly within the first 3 days after inoculation, but intracellular hyphal growth was more evident after 7 days of inoculation. We also tested the capacity of fluorescent transformants to produce ochratoxin A and the results with A. carbonarius showed that this transgenic strain produced similar concentrations of this secondary metabolite. This is the first report on the in planta expression of fluorescent proteins that should be useful to study the internal plant colonization patterns of two ochratoxigenic species in the Aspergillus section Nigri.     

A compound CP-31398 suppresses excitotoxicity-induced neurodegeneration

Neurodegeneration causes dysfunction and degeneration of neurons and is triggered by various factors including genetic defects, free radicals, injury, and glutamate excitotoxicity. Among those, glutamate excitotoxicity is implicated in chronic disorders including AD and ALS, and in acute insults in the CNS including traumatic brain injury. Neurological disorders show hallmark morphological abnormalities such as axon degeneration and cell body death. The molecular mechanisms underlying excitotoxicity-induced neurodegeneration are complex and deciphering a molecular mechanism from one angle is beneficial to understand the process, however, still difficult to develop strategies to suppress excitotoxicity-induced degeneration due to existence of other mechanisms. Thus, directly identifying compounds that can modulate excitotoxicity-induced neurodegeneration and subsequently clarifiying the molecular mechanism is a valid approach to develop effective strategies to suppress neurodegeneration. We searched for compounds that can suppress excitotoxicity-induced neurodegeneration and found that CP-31398, a known compound that can rescue the structure and function of the tumor suppressor protein p53 mutant form and stabilize the active conformation of the p53 wild-type form, suppresses excitotoxicity-induced axon degeneration and cell body death. Moreover, CP-31398 suppresses mitochondrial dysfunction which has a strong correlation with excitotoxicity. Thus, our findings identify a compound that can serve as a novel modulator of neurodegeneration induced by glutamate excitotoxicity.     

Imaging of jasmonic acid binding sites in tissue

Hormones regulate the mechanism of plant growth and development, senescence, and plants’ adaptation to the environment; studies of the molecular mechanisms of plant hormone action are necessary for the understanding of these complex phenomena. However, there is no measurable signal for the hormone signal transduction process. We synthesized and applied a quantum dot-based fluorescent probe for the labeling of jasmonic acid (JA) binding sites in plants. This labeling probe was obtained by coupling mercaptoethylamine-modified CdTe quantum dots with JA using N-hydroxysuccinimide (NHS) as a coupling agent. The probe, CdTe–JA, was characterized by transmission electron microscopy, dynamic light scattering, and fluorescent spectrum and applied in labeling JA binding sites in tissue sections of mung bean seedlings and Arabidopsis thaliana root tips. Laser scanning confocal microscopy (LSCM) revealed that the probe selectively labeled JA receptor. The competition assays demonstrated that the CdTe–JA probe retained the original bioactivity of JA. An LSCM three-dimensional reconstruction experiment demonstrated excellent photostability of the probe.     

Phenanthroimidazole-based thiobenzamide as an effective sensor for highly selective detection of mercury(II)

Based on highly selective and irreversible Hg²⁺-promoted desulfurization reaction, a new and simple phenanthroimidazole-type sensor was prepared and exhibited high selectivity towards Hg²⁺ ion over other metal ions, accompanied by transformation of a weakly fluorescent thioamide moiety (colorless) to a highly fluorescent amide one (blue), with a 136-fold increase in fluorescent intensity in aqueous solution with a pH span 2.57–9.12.     

8-Aminoquinoline-based ratiometric zinc probe: Unexpected binding mode and its application in living cells

PMQA, an 8-aminoquinoline-based ratiometric fluorescent sensor, demonstrates the Zn²⁺-induced red-shift of emission (85 nm), and was successfully applied to image zinc in living cells. Compared to 2:1 stoichiometry in PMQA–Zn²⁺, PMQA–Cu²⁺ shows 1:1 composition. Both nitrogen atoms from the aminoquinoline are missing in binding of zinc, while they are critically involved in Cu²⁺ chelation. The structure difference between PMQA–Zn²⁺ and PMQA–Cu²⁺ might shed light in designing novel zinc probes without suffering from copper interference.     

Midgut aminopeptidase N isoforms from Ostrinia nubilalis: Activity characterization and differential binding to Cry1Ab and Cry1Fa proteins from Bacillus thuringiensis

Aminopeptidase N (APN) isoforms from Lepidoptera are known for their involvement in the mode of action of insecticidal Cry proteins from Bacillus thuringiensis. These enzymes belong to a protein family with at least eight different members that are expressed simultaneously in the midgut of lepidopteran larvae. Here, we focus on the characterization of the APNs from Ostrinia nubilalis (OnAPNs) to identify potential Cry receptors. We expressed OnAPNs in insect cells using a baculovirus system and analyzed their enzymatic activity by probing substrate specificity and inhibitor susceptibility. The interaction with Cry1Ab and Cry1Fa proteins (both found in transgenic insect-resistant maize) was evaluated by ligand blot assays and immunocytochemistry. Ligand blots of brush border membrane proteins showed that both Cry proteins bound mainly to a 150 kDa-band, in which OnAPNs were greatly represented. Binding analysis of Cry proteins to the cell-expressed OnAPNs showed that OnAPN1 interacted with both Cry1Ab and Cry1Fa, whereas OnAPN3a and OnAPN8 only bound to Cry1Fa. Two isoforms, OnAPN2 and OnAPN3b, did not interact with any of these two proteins. This work provides the first evidence of a differential role of OnAPN isoforms in the mode of action of Cry proteins in O. nubilalis.