Article

Lensfree Fluorescent On-Chip Imaging of Transgenic Caenorhabditis elegans Over an Ultra-Wide Field-of-View

Electrical Engineering Department, University of California Los Angeles, Los Angeles, California, United States of America.
PLoS ONE (Impact Factor: 3.53). 01/2011; 6(1):e15955. DOI: 10.1371/journal.pone.0015955
Source: PubMed

ABSTRACT We demonstrate lensfree on-chip fluorescent imaging of transgenic Caenorhabditis elegans (C. elegans) over an ultra-wide field-of-view (FOV) of e.g., >2-8 cm(2) with a spatial resolution of ∼10 µm. This is the first time that a lensfree on-chip platform has successfully imaged fluorescent C. elegans samples. In our wide-field lensfree imaging platform, the transgenic samples are excited using a prism interface from the side, where the pump light is rejected through total internal reflection occurring at the bottom facet of the substrate. The emitted fluorescent signal from C. elegans samples is then recorded on a large area opto-electronic sensor-array over an FOV of e.g., >2-8 cm(2), without the use of any lenses, thin-film interference filters or mechanical scanners. Because fluorescent emission rapidly diverges, such lensfree fluorescent images recorded on a chip look blurred due to broad point-spread-function of our platform. To combat this resolution challenge, we use a compressive sampling algorithm to uniquely decode the recorded lensfree fluorescent patterns into higher resolution images, demonstrating ∼10 µm resolution. We tested the efficacy of this compressive decoding approach with different types of opto-electronic sensors to achieve a similar resolution level, independent of the imaging chip. We further demonstrate that this wide FOV lensfree fluorescent imaging platform can also perform sequential bright-field imaging of the same samples using partially-coherent lensfree digital in-line holography that is coupled from the top facet of the same prism used in fluorescent excitation. This unique combination permits ultra-wide field dual-mode imaging of C. elegans on a chip which could especially provide a useful tool for high-throughput screening applications in biomedical research.

Download full-text

Full-text

Available from: Ikbal Sencan, Aug 12, 2015
1 Follower
 · 
129 Views
  • Source
    • ", [19], [20] as the filter thickness is inversely correlated to the system's light collection and resolving power. Therefore, it is best to keep the filter thickness as low as possible. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Here, we report on the design, fabrication, and verification of a novel CMOS-imager-based contact imaging system. We acquired fluorescent images from live neurons by monitoring calcium changes with Fura-2 dye. Our current device consists of a removable absorption filter interfaced with a CMOS imaging sensor and an external DG-4 lamp for excitation. Fura-2 loaded Lymnaea stagnalis neurons were stimulated with dual excitation wavelengths of 340 and 380 nm; our image sensor detected 510-nm emission. We show that our system is capable of detecting intracellular calcium changes in Fura-2 loaded neurons. Further, this sensor also enabled viewing of multiple neurons over a large surface area simultaneously, an option that is not readily available in conventional light microscopy.
    IEEE Photonics Journal 02/2014; 6(1):1-15. DOI:10.1109/JPHOT.2014.2304554 · 2.33 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: On-chip lensless imaging in general aims to replace bulky lens-based optical microscopes with simpler and more compact designs, especially for high-throughput screening applications. This emerging technology platform has the potential to eliminate the need for bulky and/or costly optical components through the help of novel theories and digital reconstruction algorithms. Along the same lines, here we demonstrate an on-chip fluorescent microscopy modality that can achieve e.g., <4 μm spatial resolution over an ultra-wide field-of-view (FOV) of >0.6-8 cm(2) without the use of any lenses, mechanical-scanning or thin-film based interference filters. In this technique, fluorescent excitation is achieved through a prism or hemispherical-glass interface illuminated by an incoherent source. After interacting with the entire object volume, this excitation light is rejected by total-internal-reflection (TIR) process that is occurring at the bottom of the sample micro-fluidic chip. The fluorescent emission from the excited objects is then collected by a fiber-optic faceplate or a taper and is delivered to an optoelectronic sensor array such as a charge-coupled-device (CCD). By using a compressive-sampling based decoding algorithm, the acquired lensfree raw fluorescent images of the sample can be rapidly processed to yield e.g., <4 μm resolution over an FOV of >0.6-8 cm(2). Moreover, vertically stacked micro-channels that are separated by e.g., 50-100 μm can also be successfully imaged using the same lensfree on-chip microscopy platform, which further increases the overall throughput of this modality. This compact on-chip fluorescent imaging platform, with a rapid compressive decoder behind it, could be rather valuable for high-throughput cytometry, rare-cell research and microarray-analysis.
    Journal of Visualized Experiments 01/2011; DOI:10.3791/3181
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We present a lens-free optical tomographic microscope, which enables imaging a large volume of approximately 15 mm(3) on a chip, with a spatial resolution of < 1 μm × < 1 μm × < 3 μm in x, y and z dimensions, respectively. In this lens-free tomography modality, the sample is placed directly on a digital sensor array with, e.g., ≤ 4 mm distance to its active area. A partially coherent light source placed approximately 70 mm away from the sensor is employed to record lens-free in-line holograms of the sample from different viewing angles. At each illumination angle, multiple subpixel shifted holograms are also recorded, which are digitally processed using a pixel superresolution technique to create a single high-resolution hologram of each angular projection of the object. These superresolved holograms are digitally reconstructed for an angular range of ± 50°, which are then back-projected to compute tomograms of the sample. In order to minimize the artifacts due to limited angular range of tilted illumination, a dual-axis tomography scheme is adopted, where the light source is rotated along two orthogonal axes. Tomographic imaging performance is quantified using microbeads of different dimensions, as well as by imaging wild-type Caenorhabditis elegans. Probing a large volume with a decent 3D spatial resolution, this lens-free optical tomography platform on a chip could provide a powerful tool for high-throughput imaging applications in, e.g., cell and developmental biology.
    Proceedings of the National Academy of Sciences 05/2011; 108(18):7296-301. DOI:10.1073/pnas.1015638108 · 9.81 Impact Factor
Show more