The single particle orientation and rotational tracking (SPORT) techniques have seen rapid development in the past 5 years. Recent technical advances have greatly expanded the applicability of SPORT in biophysical studies. In this feature article, we survey the current development of SPORT and discuss its potential applications in biophysics, including cellular membrane processes and intracellular transport.

Researchers rely on a variety of microscopic techniques for observing and tracking anisotropic nanoparticles in real time experiments. This technical note focuses on the optical behavior exhibited by gold nanorods at nonplasmonic wavelengths under differential interference contrast microscopy (DIC). Intense diffraction patterns appear at nonplasmonic wavelengths, and the behavior of these patterns can be altered by adjusting the surrounding medium or the polarizer setting. Such patterns are absent when linear and crossed polarizations are utilized. Making polarization adjustments is important in DIC microscopy, because it affects bias retardation and image contrast. The nonplasmonic diffraction bands that were observed could potentially be exploited for rotational tracking, but more importantly, researchers should exhibit care in selecting a nanorod sample and the polarization setting when working with DIC microscopy.

Dumbbell-shaped nanoparticles are similar in size to their nanorod counterparts, but their optical properties have not been studied as extensively as the nanorod. In this paper, the spectra of a single dumbbell, several dumbbell dimers, and a pentamer were collected experimentally and compared with simulated spectra. Surface charge density plots were also obtained in order to elucidate the nature of the plasmonic modes. The dumbbell is shown to be a particle that acts as a transition from the nanorod to the nanosphere. Because the dumbbell shape allows adjacent particles to interlock like puzzle pieces, dumbbells can be thought of as optical building blocks that can combine into designs that are capable of supporting localized hot spots, Fano resonance, and tunable plasmon peaks.