Following aptamer-thrombin binding by force measurements

The rupture forces between an aptamer (1)-functionalized AFM tip and a thrombin-modified Au surface are analyzed. The rupture force for a single aptamer/thrombin complex is determined as approximately 4.45 pN. The analysis of the system reveals that the rupture forces correspond to the melting of the G-quadruplex structure of the aptamer bound to the thrombin. This melting of the G-quadruplex leads to the dissociation of the aptamer/thrombin complex.     

Emerging Roles of 1D Vertical Nanostructures in Orchestrating Immune Cell Functions

Engineered nano–bio cellular interfaces driven by 1D vertical nanostructures (1D-VNS) are set to prompt radical progress in modulating cellular processes at the nanoscale. Here, tuneable cell–VNS interfacial interactions are probed and assessed, highlighting the use of 1D-VNS in immunomodulation, and intracellular delivery into immune cells—both crucial in fundamental and translational biomedical research. With programmable topography and adaptable surface functionalization, 1D-VNS provide unique biophysical and biochemical cues to orchestrate innate and adaptive immunity, both ex vivo and in vivo. The intimate nanoscale cell–VNS interface leads to membrane penetration and cellular deformation, facilitating efficient intracellular delivery of diverse bioactive cargoes into hard-to-transfect immune cells. The unsettled interfacial mechanisms reported to be involved in VNS-mediated intracellular delivery are discussed. By identifying up-to-date progress and fundamental challenges of current 1D-VNS technology in immune-cell manipulation, it is hoped that this report gives timely insights for further advances in developing 1D-VNS as a safe, universal, and highly scalable platform for cell engineering and enrichment in advanced cancer immunotherapy such as chimeric antigen receptor-T therapy.     

A Microfluidic 3D Endothelium-on-a-Chip Model to Study Transendothelial Migration of T Cells in Health and Disease

The recruitment of T cells is a crucial component in the inflammatory cascade of the body. The process involves the transport of T cells through the vascular system and their stable arrest to vessel walls at the site of inflammation, followed by extravasation and subsequent infiltration into tissue. Here, we describe an assay to study 3D T cell dynamics under flow in real time using a high-throughput, artificial membrane-free microfluidic platform that allows unimpeded extravasation of T cells. We show that primary human T cells adhere to endothelial vessel walls upon perfusion of microvessels and can be stimulated to undergo transendothelial migration (TEM) by TNFα-mediated vascular inflammation and the presence of CXCL12 gradients or ECM-embedded melanoma cells. Notably, migratory behavior was found to differ depending on T cell activation states. The assay is unique in its comprehensiveness for modelling T cell trafficking, arrest, extravasation and migration, all in one system, combined with its throughput, quality of imaging and ease of use. We envision routine use of this assay to study immunological processes and expect it to spur research in the fields of immunological disorders, immuno-oncology and the development of novel immunotherapeutics.     

Maximizing Transfection Efficiency of Vertically Aligned Silicon Nanowire Arrays

Vertically aligned silicon nanowire (VA‐SiNW) arrays are emerging as a powerful new tool for gene delivery by means of mechanical transfection. In order to utilize this tool efficiently, uncertainties around the required design parameters need to be removed. Here, a combination of nanosphere lithography and templated metal‐assisted wet chemical etching is used to fabricate VA‐SiNW arrays with a range of diameters, heights, and densities. This fabrication strategy allows identification of critical parameters of surface topography and consequently the design of SiNW arrays that deliver plasmid with high transfection efficiency into a diverse range of human cells whilst maintaining high cell viability. These results illuminate the cell‐materials interactions that mediate VA‐SiNW transfection and have the potential to transform gene therapy and underpin future treatment modalities.     

Confinement-guided shaping of semiconductor nanowires and nanoribbons: "writing with nanowires"

To fully exploit their full potential, new semiconductor nanowire building blocks with ab initio controlled shapes are desired. However, and despite the great synthetic advances achieved, the ability to control nanowire's geometry has been significantly limited. Here, we demonstrate a simple confinement-guided nanowire growth method that enables to predesign not only the chemical and physical attributes of the synthesized nanowires but also allows a perfect and unlimited control over their geometry. Our method allows the synthesis of semiconductor nanowires in a wide variety of two-dimensional shapes such as any kinked (different turning angles), sinusoidal, linear, and spiral shapes, so that practically any desired geometry can be defined. The shape-controlled nanowires can be grown on almost any substrate such as silicon wafer, quartz and glass slides, and even on plastic substrates (e.g., Kapton HN).     

Monitoring the activity of tyrosinase on a tyramine/dopamine-functionalized surface by force microscopy

Tyrosinase activity is monitored by pi-donor-acceptor force interactions between a bipyridinium-modified AFM tip and the biocatalytic reaction product generated on a tyramine- (or dopamine-) modified surface. Upon oxidation of the surface to dopaquinone as a result of tyrosinase activity, force interactions are switched "OFF". After reduction of the resulting surface with ascorbic acid, forces are quantitatively reestablished as a result of the formation of the dopamine-functionalized surfaces. The method provides a general approach to design biosensors using force interactions as the readout signal.     

Conformation,Coordination and Ion Selectivity of the Ionophore X206

The conformation and the cation coordination of the ionophore X206, which selectively transports potassium over sodium, are evaluated in an effort to correlate the structural features of the ionophore with its ion selectivity. For this purpose, the crystal structure of the Na⁺-complex of X206 has been determined by X-ray diffraction and is compared with those of the free acid form of X206, its Ag⁺-complex and the K⁺-complex of the closely related ionophore alborixin. The ionophore conformation is very similar in all four structures. The carboxylic acid end is essentially invariant, but small changes in torsion angles of up to 26° at the other end of the molecule, combined with differences in the positions of the cations, result in very different coordination geometries for the cations. The conformations of the Ag⁺- and K⁺-complexes resemble the free acid conformation more closely than does that of the Na⁺-complex. The K⁺ ion is 8 coordinate while the Ag⁺ and Na⁺ ions are 6 and 5 coordinate, respectively. Empirical calculations of the bond strength on the basis of the coordination bond lengths show a stronger binding of K⁺ than of Na⁺ which is consistent with the greater selectivity for binding of the former.