Dependence of Plasmonic Properties on Electron Densities for Various Coupled Au Nanostructures

Noble metallic nanostructures have great potential in optical sensing application in visible and near-infrared frequencies. Their plasmonic properties can be manipulated by <i>in situ</i> controlling their electron densities for isolated nanostructures. However, the effect of charging remains underexplored for coupled systems. In this work, we theoretically investigated the dependence of their far-field and near-field properties on their electron densities for various coupled gold structures. With increasing electron densities, their enhancement factors increase while their plasmonic resonance peaks are blue-shifted. The resonance peak position of ellipsoid-ellipsoid dimers shows the highest sensitivity in response to the charging effects with the slope of −2.87. The surface-averaged electric field of ellipsoid monomer shows largest enhancement ratio of 1.13 with 16% excess electrons. These results can be well explained by an effective dipole moment model. In addition, we also studied the sphere-on-substrate nanostructure which can be precisely fabricated. This system shows low sensitivity to the charging effect with the slope of −1.46 but remarkable enhancement ratio of 1.13 on near field response with 16% excess electrons

Electric Communication between the Inner Part of a Cell and an Electrode: The Way To Look inside a Cell

A strategy to assemble cells on a solid support surface, here the surface of a gold electrode, is developed by transfecting cells with thiolated DNA molecules which have been immobilized on the gold electrode surface in advance. This strategy to assemble cells can present a general and convenient method for cell assembly on a solid support surface. What is more interesting, since efficient electric communication via the thiolated DNA between the electroactive species inside the cells and the substrate electrode can be achieved, an approach to “look” into the inner part of the cells is proposed. For the test in this work, one drug, kaempferol, and one dye molecule, methylene blue, inside the cells have been detected by the commonly used electrochemical method linear scan voltammetry, and satisfactory results have been obtained

Electrochemical Approach To Detect Apoptosis

This paper reports an electrochemical approach for detection of apoptosis. Here we prepare a gold electrode modified with a helix peptide ferrocene (Fc)−GDGDEVDGC. Fc is used as an electroactive reporter and the peptide as a recognition and cleavage site of caspase-3, which is a special proteinase to apoptosis. Results show that this method may sensitively and specifically detect apoptotic cells with signal decline of 85%. This approach is different from the previous methods for apoptosis detection, because it does not need any fluorescent materials, expensive biological instruments, or complicated procedures

3D Printed Programmable Release Capsules

The development of methods for achieving precise spatiotemporal control over chemical and biomolecular gradients could enable significant advances in areas such as synthetic tissue engineering, biotic–abiotic interfaces, and bionanotechnology. Living organisms guide tissue development through highly orchestrated gradients of biomolecules that direct cell growth, migration, and differentiation. While numerous methods have been developed to manipulate and implement biomolecular gradients, integrating gradients into multiplexed, three-dimensional (3D) matrices remains a critical challenge. Here we present a method to 3D print stimuli-responsive core/shell capsules for programmable release of multiplexed gradients within hydrogel matrices. These capsules are composed of an aqueous core, which can be formulated to maintain the activity of payload biomolecules, and a poly­(lactic-<i>co</i>-glycolic) acid (PLGA, an FDA approved polymer) shell. Importantly, the shell can be loaded with plasmonic gold nanorods (AuNRs), which permits selective rupturing of the capsule when irradiated with a laser wavelength specifically determined by the lengths of the nanorods. This precise control over space, time, and selectivity allows for the ability to pattern 2D and 3D multiplexed arrays of enzyme-loaded capsules along with tunable laser-triggered rupture and release of active enzymes into a hydrogel ambient. The advantages of this 3D printing-based method include (1) highly monodisperse capsules, (2) efficient encapsulation of biomolecular payloads, (3) precise spatial patterning of capsule arrays, (4) “on the fly” programmable reconfiguration of gradients, and (5) versatility for incorporation in hierarchical architectures. Indeed, 3D printing of programmable release capsules may represent a powerful new tool to enable spatiotemporal control over biomolecular gradients

3D Printed Programmable Release Capsules

The development of methods for achieving precise spatiotemporal control over chemical and biomolecular gradients could enable significant advances in areas such as synthetic tissue engineering, biotic–abiotic interfaces, and bionanotechnology. Living organisms guide tissue development through highly orchestrated gradients of biomolecules that direct cell growth, migration, and differentiation. While numerous methods have been developed to manipulate and implement biomolecular gradients, integrating gradients into multiplexed, three-dimensional (3D) matrices remains a critical challenge. Here we present a method to 3D print stimuli-responsive core/shell capsules for programmable release of multiplexed gradients within hydrogel matrices. These capsules are composed of an aqueous core, which can be formulated to maintain the activity of payload biomolecules, and a poly­(lactic-<i>co</i>-glycolic) acid (PLGA, an FDA approved polymer) shell. Importantly, the shell can be loaded with plasmonic gold nanorods (AuNRs), which permits selective rupturing of the capsule when irradiated with a laser wavelength specifically determined by the lengths of the nanorods. This precise control over space, time, and selectivity allows for the ability to pattern 2D and 3D multiplexed arrays of enzyme-loaded capsules along with tunable laser-triggered rupture and release of active enzymes into a hydrogel ambient. The advantages of this 3D printing-based method include (1) highly monodisperse capsules, (2) efficient encapsulation of biomolecular payloads, (3) precise spatial patterning of capsule arrays, (4) “on the fly” programmable reconfiguration of gradients, and (5) versatility for incorporation in hierarchical architectures. Indeed, 3D printing of programmable release capsules may represent a powerful new tool to enable spatiotemporal control over biomolecular gradients