InP Nanowire Biosensor with Tailored Biofunctionalization: Ultrasensitive and Highly Selective Disease Biomarker Detection.

Electrically active field-effect transistors (FET) based biosensors are of paramount importance in life science applications, as they offer direct, fast, and highly sensitive label-free detection capabilities of several biomolecules of specific interest. In this work, we report a detailed investigation on surface functionalization and covalent immobilization of biomarkers using biocompatible ethanolamine and poly(ethylene glycol) derivate coatings, as compared to the conventional approaches using silica monoliths, in order to substantially increase both the sensitivity and molecular selectivity of nanowire-based FET biosensor platforms. Quantitative fluorescence, atomic and Kelvin probe force microscopy allowed detailed investigation of the homogeneity and density of immobilized biomarkers on different biofunctionalized surfaces. Significantly enhanced binding specificity, biomarker density, and target biomolecule capture efficiency were thus achieved for DNA as well as for proteins from pathogens. This optimized functionalization methodology was applied to InP nanowires that due to their low surface recombination rates were used as new active transducers for biosensors. The developed devices provide ultrahigh label-free detection sensitivities ∼1 fM for specific DNA sequences, measured via the net change in device electrical resistance. Similar levels of ultrasensitive detection of ∼6 fM were achieved for a Chagas Disease protein marker (IBMP8-1). The developed InP nanowire biosensor provides thus a qualified tool for detection of the chronic infection stage of this disease, leading to improved diagnosis and control of spread. These methodological developments are expected to substantially enhance the chemical robustness, diagnostic reliability, detection sensitivity, and biomarker selectivity for current and future biosensing devices.

Super-Droplet-Repellent Carbon-Based Printable Perovskite Solar Cells.

Despite attractive cost-effectiveness, scalability, and superior stability, carbon-based printable perovskite solar cells (CPSCs) still face moisture-induced degradation that limits their lifespan and commercial potential. Here, the moisture-preventing mechanisms of thin nanostructured super-repellent coating (advancing contact angle >167° and contact angle hysteresis 7°) integrated into CPSCs are investigated for different moisture forms (falling water droplets vs water vapor vs condensed water droplets). It is shown that unencapsulated super-repellent CPSCs have superior performance under continuous droplet impact for 12 h (rain falling experiments) compared to unencapsulated pristine (uncoated) CPSCs that degrade within seconds. Contrary to falling water droplets, where super-repellent coating serves as a shield, water vapor is found to physisorb through porous super-repellent coating (room temperature and relative humidity, RH 65% and 85%) that increase the CPSCs performance for 21% during ≈43 d similarly to pristine CPSCs. It is further shown that water condensation forms within or below the super-repellent coating (40 °C and RH 85%), followed by chemisorption and degradation of CPSCs. Because different forms of water have distinct effects on CPSC, it is suggested that future standard tests for repellent CPSCs should include rain falling and condensate formation tests. The findings will thus inspire the development of super-repellent coatings for moisture prevention.

N-acetylcysteine effects on extracellular polymeric substances of Xylella fastidiosa: A spatiotemporal investigation with implications for biofilm disruption.

BACKGROUND: The matrix of extracellular polymeric substances (EPS) present in biofilms greatly amplifies the problem of bacterial infections, protecting bacteria against antimicrobial treatments and eventually leading to bacterial resistance. The need for alternative treatments that destroy the EPS matrix becomes evident. N-acetylcysteine (NAC) is one option that presents diverse effects against bacteria; however, the different mechanisms of action of NAC in biofilms have yet to be elucidated. OBJECTIVES: In this work, we performed microscopy studies at micro and nano scales to address the effects of NAC at single cell level and early-stage biofilms of the Xylella fastidiosa phytopathogen. METHODS: We show the physical effects of NAC on the adhesion surface and the different types of EPS, as well as the mechanical response of individual bacteria to NAC concentrations between 2 and 20 mg/mL. RESULTS: NAC modified the conditioning film on the substrate, broke down the soluble EPS, resulting in the release of adherent bacteria, decreased the volume of loosely bound EPS, and disrupted the biofilm matrix. Tightly bound EPS suffered structural alterations despite no solid evidence of its removal. In addition, bacterial force measurements upon NAC action performed with InP nanowire arrays showed an enhanced momentum transfer to the nanowires due to increased cell mobility resulting from EPS removal. CONCLUSIONS: Our results clearly show that conditioning film and soluble EPS play a key role in cell adhesion control and that NAC alters EPS structure, providing solid evidence that NAC actuates mainly on EPS removal, both at single cell and biofilm levels.

Magnetic-Responsive Carbon Nanotubes Composite Scaffolds for Chondrogenic Tissue Engineering.

The demand for engineered scaffolds capable of delivering multiple cues to cells continues to grow as the interplay between cell fate with microenvironmental and external cues is revealed. Emphasis has been given to develop stimuli-responsive scaffolds. These scaffolds are designed to sense an external stimulus triggering a specific response (e.g., change in the microenvironment, release therapeutics, etc.) and then initiate/modulate a desired biofunction. Here, magnetic-responsive carboxylated multi-walled carbon nanotubes (cMWCNTs) are integrated into 3D collagen/polylactic acid (PLA) scaffold via a reproducible filtration-based method. The integrity and biomechanical performance of the collagen/PLA scaffolds are preserved after cMWCNT integration. In vitro safety assessment of cMWCNT/collagen/PLA scaffolds shows neither cytotoxicity effects nor macrophage pro-inflammatory response, supporting further in vitro studies. The cMWCNT/collagen/PLA scaffolds enhance chondrocytes metabolic activity while maintaining high cell viability and extracellular matrix (i.e., type II collagen and aggrecan) production. Comprehensive in vitro study applying static and pulsed magnetic field on seeded scaffolds shows no specific cell response in dependence with the applied field. This result is independent of the presence or absence of cMWCNT into the collagen/PLA scaffolds. Taken together, these findings provide additional evidence of the benefits to exploit the CNTs outstanding properties in the design of stimuli-responsive scaffolds.

Physiochemically Distinct Surface Properties of SU-8 Polymer Modulate Bacterial Cell-Surface Holdfast and Colonization.

SU-8 polymer is an excellent platform for diverse applications due to its high aspect ratio of micro/nanostructure fabrication and exceptional physicochemical and biocompatible properties. Although SU-8 polymer has often been investigated for various biological applications, how its surface properties influence the interaction of bacterial cells with the substrate and its colonization is poorly understood. In this work, we tailor SU-8 nanoscale surface properties to investigate single-cell motility, adhesion, and successive colonization of phytopathogenic bacteria, Xylella fastidiosa. Different surface properties of SU-8 thin films have been prepared using photolithography processing and oxygen plasma treatment. A more significant density of carboxyl groups in hydrophilic plasma-treated SU-8 surfaces promotes faster cell motility in the earlier growth stage. The hydrophobic nature of pristine SU-8 surfaces shows no trackable bacterial motility and 5-10 times more single cells adhered to the surface than its plasma-treated counterpart. In addition, plasma-treated SU-8 samples suppressed bacterial adhesion, with surfaces showing less than 5% coverage. These results not only showcase that SU-8 surface properties can impact the spatiotemporal bacterial behavior but also provide insights into pathogens' prominent ability to evolve and adapt to different surface properties.

Controlled spatial organization of bacterial growth reveals key role of cell filamentation preceding Xylella fastidiosa biofilm formation.

The morphological plasticity of bacteria to form filamentous cells commonly represents an adaptive strategy induced by stresses. In contrast, for diverse human and plant pathogens, filamentous cells have been recently observed during biofilm formation, but their functions and triggering mechanisms remain unclear. To experimentally identify the underlying function and hypothesized cell communication triggers of such cell morphogenesis, spatially controlled cell patterning is pivotal. Here, we demonstrate highly selective cell adhesion of the biofilm-forming phytopathogen Xylella fastidiosa to gold-patterned SiO2 substrates with well-defined geometries and dimensions. The consequent control of both cell density and distances between cell clusters demonstrated that filamentous cell formation depends on cell cluster density, and their ability to interconnect neighboring cell clusters is distance-dependent. This process allows the creation of large interconnected cell clusters that form the structural framework for macroscale biofilms. The addition of diffusible signaling molecules from supernatant extracts provides evidence that cell filamentation is induced by quorum sensing. These findings and our innovative platform could facilitate therapeutic developments targeting biofilm formation mechanisms of X. fastidiosa and other pathogens.