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The controlled rotation of individual cells plays a crucial role in enabling three-dimensional multi-angle observation of cellular structure, function, and dynamic processes. Reported cell rotation techniques often struggle to strike a balance between high precision and simple control, and they exhibit limited control flexibility, typically achieving only uniaxial cell rotation. In this study, we propose a cell rotation technique in three dimensions based on optofluidics, which utilizes optical tweezers to immobilize the cell and exploits the asymmetry of the surrounding flow to drive cell rotation. By adjusting the focal position of the optical tweezers, cells can be positioned within various flow profiles, enabling control of the rotation speed, rotation direction, and rotation axis of cells. This approach simplifies the manipulation procedure, achieving desirable control precision and greater rotation flexibility. Using our approach, multi-angle surface imaging projections of target cells can be rapidly obtained, followed by capturing the cell contour data from the images. By combining the cell contour data with corresponding angular position information, we have reconstructed the 3D surface of the target cell. We have employed this technique in experiments for the analysis of red blood cell morphology. Based on the constructed 3D surface images of diverse-shaped red blood cells, we quantified structural parameters including cell surface area, volume, sphericity, and surface roughness, which demonstrates the potential application of this cell rotation technique for cellular morphological analysis. [ABSTRACT FROM AUTHOR]

Optical tweezers are ideal tools for cell manipulation in vivo due to their non-contact trapping ability. In the current studies, the optical trapping of cells can only be achieved in light-permeable organs. It is important to expand the application of optical tweezers to opaque tissues and organs, where biological activities are the primary focus of biomedical research. However, the optical manipulation of cells in these opaque organs cannot be imaged using a conventional transillumination microscope due to the opacity of these organs. Here, we use optical tweezers to trap erythrocytes and measure the cell deformability in mouse liver, which are imaged with oblique back-illumination microscopy (OBM). In the microscope system, two fibers are fixed at the same oblique angle on both sides of the microscopic objective, illuminating the trapping target asymmetrically. The dual-wavelength OBM strategy allows for obtaining a differential phase contrast image in a single-shot by color channel separation. The OBM can image the flowing and trapped erythrocytes in vivo in real-time. Furthermore, the erythrocyte deformability in vivo is evaluated with optical tweezers. The spring stiffness in vivo is 8.2 ± 2.1 μN m−1, which is obtained by stretching the trapped cells with blood drag flow. Our works make it possible to utilize optical tweezers to study the live cell dynamics in opaque organs, which will expand the application of optical tweezers in the fields of biomechanical studies. [ABSTRACT FROM AUTHOR]