ABSTRACT
To navigate through diverse tissues, migrating cells must balance persistent self-propelled motion with adaptive behaviors to circumvent obstacles. We identify a curvature-sensing mechanism underlying obstacle evasion in immune-like cells. Specifically, we propose that actin polymerization at the advancing edge of migrating cells is inhibited by the curvature-sensitive BAR domain protein Snx33 in regions with inward plasma membrane curvature. The genetic perturbation of this machinery reduces the cells' capacity to evade obstructions combined with faster and more persistent cell migration in obstacle-free environments. Our results show how cells can read out their surface topography and utilize actin and plasma membrane biophysics to interpret their environment, allowing them to adaptively decide if they should move ahead or turn away. On the basis of our findings, we propose that the natural diversity of BAR domain proteins may allow cells to tune their curvature sensing machinery to match the shape characteristics in their environment.
Subject(s)
Actins , Adaptation, Psychological , Cell Membrane , Cell Movement , BiophysicsABSTRACT
SIGNIFICANCE: Highly sensitive detection is crucial for all-optical photoacoustic (PA) imaging. However, free-space optical detectors are prone to optical aberrations, which can degrade the pressure sensitivity and result in deteriorated image quality. While spatial mode-filtering has been proposed to alleviate these problems in Fabry-Pérot-based pressure sensors, their real functional advantage has never been properly investigated. AIM: We rigorously and quantitatively compare the performance of free-space and fiber-coupled detectors for Fabry-Pérot-based pressure sensors. APPROACH: We develop and characterize a quantitative correlative setup capable of simultaneous PA imaging using a free space and a fiber-coupled detector. RESULTS: We found that fiber-coupled detectors are superior in terms of both signal level and image quality in realistic all-optical PA tomography settings. CONCLUSIONS: Our study has important practical implications in the field of PA imaging, as for most applications and implementations fiber-coupled detectors are relatively easy to employ since they do not require modifications to the core of the system but only to the peripherally located detector.
Subject(s)
Tomography, OpticalABSTRACT
Optical resonators are some of the most promising optical devices for manufacturing high-performance pressure sensors for photoacoustic imaging. Among these, Fabry-Perot (FP)-based pressure sensors have been successfully used for a multitude of applications. However, critical performance aspects of FP-based pressure sensors have not been studied extensively, including the effects that system parameters such as beam diameter and cavity misalignment have on transfer function shape. Here, we discuss the possible origins of the transfer function asymmetry, ways to correctly estimate the FP pressure sensitivity under practical experimental conditions, as well as show the importance of proper assessments for real-world applications.
ABSTRACT
Zernike polynomials are one of the most widely used mathematical descriptors of optical aberrations in the fields of imaging and adaptive optics. Their mathematical orthogonality as well as isomorphisms with experimentally observable aberrations make them a very powerful tool in solving numerous problems in beam optics, most notably the recent developments of adaptive optics for correcting beam aberrations. However, Zernike aberrations show cross coupling between individual modes when used in combination with Gaussian beams, which are ubiquitous in most practical applications, an effect that has not been extensively studied. Here we propose a novel framework that is capable of explaining the fundamental cross-compensation of Zernike type aberrations, in both low-aberration and high-aberration regimes. Our approach is based on analyzing the coupling between Zernike modes and different classes of Laguerre-Gauss modes, which allows investigating aberrated beams not only on a single transverse plane but also during their 3D propagation.
ABSTRACT
All-optical ultrasound detection bears a number of unique advantages for photoacoustic tomography, including the ability for high resolution sampling of the acoustic field and its compatibility with a wide variety of other optical modalities. However, optical schemes based on miniaturized cavities are sensitive to optical aberrations as well as manufacturing-induced cavity imperfections which degrade sensor sensitivity and deteriorate photoacoustic image quality. Here we present an experimental method based on adaptive optics that is capable of enhancing the overall sensitivity of Fabry-Pérot based photoacoustic sensors. We experimentally observe clear improvements in photoacoustic signal detection as well as overall image quality after photoacoustic tomography reconstructions when applied to mammalian tissues in vivo.
