Viral plaque analysis on a wide field-of-view, time-lapse, on-chip imaging platform

Cost-efficient boundary-free surface patterning achieves high effective-throughput of time-lapse microscopy experiments

Time-lapse microscopy plays critical roles in the studies of cellular dynamics. However, setting up a time-lapse movie experiments is not only laborious but also with low output, mainly due to the cell-losing problem (i.e., cells moving out of limited field of view), especially in a long-time recording. To overcome this issue, we have designed a cost-efficient way that enables cell patterning on the imaging surfaces without any physical boundaries. Using mouse embryonic stem cells as an example system, we have demonstrated that our boundary-free patterned surface solves the cell-losing problem without disturbing their cellular phenotype. Statistically, the presented system increases the effective-throughput of time-lapse microscopy experiments by an order of magnitude.

Phage susceptibility testing and infectious titer determination through wide-field lensless monitoring of phage plaque growth

The growing number of drug-resistant bacterial infections worldwide is driving renewed interest in phage therapy. Based on the use of a personalized cocktail composed of highly specific bacterial viruses, this therapy relies on a range of tests on agar media to determine the most active phage on a given bacterial target (phage susceptibility testing), or to isolate new lytic phages from an environmental sample (enrichment of phage banks). However, these culture-based techniques are still solely interpreted through direct visual detection of plaques. The main objective of this work is to investigate computer-assisted methods in order to ease and accelerate diagnosis in phage therapy but also to study phage plaque growth kinetics. For this purpose, we designed a custom wide-field lensless imaging device, which allows continuous monitoring over a very large area sensor (3.3 cm2). Here we report bacterial susceptibility to Staphylococcus aureus phage in 3 hr and estimation of infectious titer in 8 hr 20 min. These are much shorter time-to-results than the 12 to 24 hours traditionally needed, since naked eye observation and counting of phage plaques is still the most widely used technique for susceptibility testing prior to phage therapy. Moreover, the continuous monitoring of the samples enables the study of plaque growth kinetics, which enables a deeper understanding of the interaction between phage and bacteria. Finally, thanks to the 4.3 μm resolution, we detect phage-resistant bacterial microcolonies of Klebsiella pneumoniae inside the boundaries of phage plaques and thus show that our prototype is also a suitable device to track phage resistance. Lensless imaging is therefore an all-in-one method that could easily be implemented in cost-effective and compact devices in phage laboratories to help with phage therapy diagnosis.

Oncolytic herpes simplex virus and temozolomide synergistically inhibit breast cancer cell tumorigenesis in vitro and in vivo

The oncolytic herpes simplex virus (HSV) G47Δ can selectively eliminate glioblastoma cells via viral replication and temozolomide (TMZ) has been clinically used to treat glioblastoma. However, the combined effect of G47Δ and TMZ on cancer cells, particularly on breast cancer cells, remains largely unknown. The objective of the present study was to investigate the role and underlying mechanism of G47Δ and TMZ, in combination, in breast cancer cell tumorigenesis. The human breast cancer cell lines SK-BR-3 and MDA-MB-468 were treated with G47Δ and TMZ individually or in combination. Cell viability, flow cytometry, reverse transcription quantitative-PCR and western blotting were performed to investigate the synergy between G47Δ and TMZ in regulating breast cancer cell behavior in vitro. The role of G47Δ and TMZ in suppressing tumorigenesis in vivo was investigated in a xenograft mouse model. G47Δ and TMZ served a synergistic role resulting in decreased breast cancer cell viability, induction of cell cycle arrest, promotion of tumor cell apoptosis and enhancement of DNA damage response in vitro. The combined administration of G47Δ and TMZ also effectively suppressed breast cancer cell-derived tumor growth in vivo, compared with the administration of G47Δ or TMZ alone. Synergy between G47Δ and TMZ was at least partially mediated via TMZ-induced acceleration of G47Δ replication, and such a synergy in breast cancer cells in vitro and in vivo provides novel insight into the future development of a therapeutic strategy against breast cancer.

Real-time bacterial microcolony counting using on-chip microscopy

Observing microbial colonies is the standard method for determining the microbe titer and investigating the behaviors of microbes. Here, we report an automated, real-time bacterial microcolony-counting system implemented on a wide field-of-view (FOV), on-chip microscopy platform, termed ePetri. Using sub-pixel sweeping microscopy (SPSM) with a super-resolution algorithm, this system offers the ability to dynamically track individual bacterial microcolonies over a wide FOV of 5.7 mm × 4.3 mm without requiring a moving stage or lens. As a demonstration, we obtained high-resolution time-series images of S. epidermidis at 20-min intervals. We implemented an image-processing algorithm to analyze the spatiotemporal distribution of microcolonies, the development of which could be observed from a single bacterial cell. Test bacterial colonies with a minimum diameter of 20 μm could be enumerated within 6 h. We showed that our approach not only provides results that are comparable to conventional colony-counting assays but also can be used to monitor the dynamics of colony formation and growth. This microcolony-counting system using on-chip microscopy represents a new platform that substantially reduces the detection time for bacterial colony counting. It uses chip-scale image acquisition and is a simple and compact solution for the automation of colony-counting assays and microbe behavior analysis with applications in antibacterial drug discovery.

Lensless Imaging and Sensing

High-resolution optical microscopy has traditionally relied on high-magnification and high-numerical aperture objective lenses. In contrast, lensless microscopy can provide high-resolution images without the use of any focusing lenses, offering the advantages of a large field of view, high resolution, cost-effectiveness, portability, and depth-resolved three-dimensional (3D) imaging. Here we review various approaches to lensless imaging, as well as its applications in biosensing, diagnostics, and cytometry. These approaches include shadow imaging, fluorescence, holography, superresolution 3D imaging, iterative phase recovery, and color imaging. These approaches share a reliance on computational techniques, which are typically necessary to reconstruct meaningful images from the raw data captured by digital image sensors. When these approaches are combined with physical innovations in sample preparation and fabrication, lensless imaging can be used to image and sense cells, viruses, nanoparticles, and biomolecules. We conclude by discussing several ways in which lensless imaging and sensing might develop in the near future.

Compact Wireless Microscope for In-Situ Time Course Study of Large Scale Cell Dynamics within an Incubator

Imaging of live cells in a region of interest is essential to life science research. Unlike the traditional way that mounts CO2 incubator onto a bulky microscope for observation, here we propose a wireless microscope (termed w-SCOPE) that is based on the “microscope-in-incubator” concept and can be easily housed into a standard CO2 incubator for prolonged on-site observation of the cells. The w-SCOPE is capable of tunable magnification, remote control and wireless image transmission. At the same time, it is compact, measuring only ~10 cm in each dimension, and cost-effective. With the enhancement of compressive sensing computation, the acquired images can achieve a wide field of view (FOV) of ~113 mm² as well as a cellular resolution of ~3 μm, which enables various forms of follow-up image-based cell analysis. We performed 12 hours time-lapse study on paclitaxel-treated MCF-7 and HEK293T cell lines using w-SCOPE. The analytic results, such as the calculated viability and therapeutic window, from our device were validated by standard cell detection assays and imaging-based cytometer. In addition to those end-point detection methods, w-SCOPE further uncovered the time course of the cell’s response to the drug treatment over the whole period of drug exposure.