Review of recent developments in stimulated emission depletion microscopy: applications on cell imaging

Stimulated emission depletion (STED) microscopy is one type of far-field optical technique demonstrated to provide subdiffraction resolution. STED microscopy utilizes a donut-shaped depletion beam to limit the probe volume to be much smaller than a diffraction-limited spot. Resolutions as small as a few tens of nanometers laterally are reported for cell analysis. The different versions of STED microscopes are described and contrasted in terms of their applicability for biological imaging. Finally, we suggest likely avenues for improving the performance and increasing the utility of STED microscopy

Harnessing Plasmon-Induced Hot Carriers at the Interfaces With Ferroelectrics

This article reviews the scientific understanding and progress of interfacing plasmonic particles with ferroelectrics in order to facilitate the absorption of low-energy photons and their conversion to chemical fuels. The fundamental principles of hot carrier generation and charge injection are described for semiconductors interfaced with metallic nanoparticles and immersed in aqueous solutions, forming a synergistic juncture between the growing fields of plasmonically-driven photochemistry and semiconductor photocatalysis. The underlying mechanistic advantages of a metal-ferroelectric vs. metal-nonferroelectric interface are presented with respect to achieving a more optimal and efficient control over the Schottky barrier height and charge separation. Notable recent examples of using ferroelectric-interfaced plasmonic particles have demonstrated their roles in yielding significantly enhanced photocurrents as well as in the photon-driven production of molecular hydrogen. Notably, plasmonically-driven photocatalysis has been shown to occur for photon wavelengths in the infrared range, which is at lower energies than typically possible for conventional semiconductor photocatalysts. Recent results thus demonstrate that integrated ferroelectric-plasmonic systems represent a potentially transformative concept for use in the field of solar energy conversion

Near Infrared Light Activates Molecular Nanomachines to Drill Into and Kill Cells

Using two-photon excitation (2PE), molecular nanomachines (MNMs) are able to drill through cell membranes and kill the cells. This avoids the use of the more damaging ultraviolet (UV) light that has been used formerly to induce this nanomechanical cell-killing effect. Since 2PE is inherently confocal, enormous precision can be realized. The MNMs can be targeted to specific cell surfaces through peptide addends. Further, the efficacy was verified through controlled opening of synthetic bilayer vesicles using the 2PE excitation of MNM that had been trapped within the vesicles

Molecular machines open cell membranes

Beyond the more common chemical delivery strategies, several physical techniques are used to open the lipid bilayers of cellular membranes. These include using electric and magnetic fields, temperature, ultrasound or light to introduce compounds into cells, to release molecular species from cells or to selectively induce programmed cell death (apoptosis) or uncontrolled cell death (necrosis). More recently, molecular motors and switches that can change their conformation in a controlled manner in response to external stimuli have been used to produce mechanical actions on tissue for biomedical applications. Here we show that molecular machines can drill through cellular bilayers using their molecular-scale actuation, specifically nanomechanical action. Upon physical adsorption of the molecular motors onto lipid bilayers and subsequent activation of the motors using ultraviolet light, holes are drilled in the cell membranes. We designed molecular motors and complementary experimental protocols that use nanomechanical action to induce the diffusion of chemical species out of synthetic vesicles, to enhance the diffusion of traceable molecular machines into and within live cells, to induce necrosis and to introduce chemical species into live cells. We also show that, by using molecular machines that bear short peptide addends, nanomechanical action can selectively target specific cell-surface recognition sites. Beyond the in vitroapplications demonstrated here, we expect that molecular machines could also be used in vivo, especially as their design progresses to allow two-photon, near-infrared and radio-frequency activation

Single Cell Optical Imaging and Spectroscopy

In his 1665 treatise, Micrographia, Robert Hooke described the many observations he had made using a microscope, including compartment-like structures in cork samples that he termed “cells

A dual wavelength-activatable gold nanorod complex for synergistic cancer treatment

A multifunctional gold nanorod complex was formulated for synergistic anticancer treatment upon ultraviolet (UV) and infrared (IR) light dual irradiations