longitudinal-morphological-physiological-monitoring-three-dimensional

Longitudinal Morphological and Physiological Monitoring of Three-dimensional Tumor Spheroids Using Optical Coherence Tomography

Tumor spheroids have been developed as a three-dimensional (3D) cell culture model in cancer research and anti-cancer drug discovery. However, currently, ...

Lehigh University

We develop a multiphysics model to study the contribution of electrokinetics on the biomolecular detection process and provide a physical explanation of the two to three orders of magnitude difference in detection time between experimental results and theoretical predications at ultralow concentration. The electrokinetic effects, including electrophoretic force and electroosmotic flow, have been systematically studied under various sensor design and test conditions. In a typical single nanowire-based sensor, it is found that electrokinetic effects could result in a reduction of detection time over 90 times, compared with that induced by pure biomolecular diffusion. The detection time difference is further enhanced by increasing the applied gate voltage or the number of nanowires. It is proposed that accelerated biomolecular detection at ultralow concentration could be achieved by appropriate combinations of electrokinetic effects and nanowire sensor design.

Electrokinetic effects on detection time of nanowire biosensor.

The inflammatory response in endothelial cells (ECs) leads to an increase in vascular permeability through the formation of gaps. However, the dynamic nature of vascular permeability and external factors involved is still elusive. In this work, we use a biomimetic blood vessel (BBV) microfluidic model to measure in real-time the change in permeability of the EC layer under culture in physiologically relevant flow conditions. This platform studies the dynamics and characterizes vascular permeability when the EC layer is triggered with an inflammatory agent using tracer molecules of three different sizes, and the results are compared to a transwell insert study. We also apply an analytical model to compare the permeability data from the different tracer molecules to understand the physiological and bio-transport significance of endothelial permeability based on the molecule of interest. A computational model of the BBV model is also built to understand the factors influencing transport of molecules of different sizes under flow. The endothelial monolayer cultured under flow in the BBV model was treated with thrombin, a serine protease that induces a rapid and reversible increase in endothelium permeability. On analysis of permeability data, it is found that the transport characteristics for fluorescein isothiocyanate (FITC) dye and FITC Dextran 4k Da molecules are similar in both BBV and transwell models, but FITC Dextran 70k Da molecules show increased permeability in the BBV model as convection flow (Peclet number > 1) influences the molecule transport in the BBV model. We also calculated from permeability data the relative increase in intercellular gap area during thrombin treatment for ECs in the BBV and transwell insert models to be between 12% and 15%. This relative increase was found to be within range of what we quantified from F-actin stained EC layer images. The work highlights the importance of incorporating flow in  vascular models, especially in studies involving transport of large size objects such as antibodies, proteins, nano/micro particles, and cells.

Characterization of vascular permeability using a biomimetic microfluidic blood vessel model.

A wavy-herringbone (wavy-HB) structured microfluidic device was used to effectively and selectively capture and release circulating tumor cells (CTCs) by using immunoaffinity and magnetic force. This device was designed to create passive turbulence and increase the possibility of tumor cells colliding with the device wall. Under an external magnetic field, magnetic particles (MPs) coated with anti-EpCAM against a tumor cell surface protein (EpCAM) were immobilized over the wavy-HB surface to capture tumor cells. After removing the magnetic field, the captured cells with surplus MPs were released from the device and collected; thus, these cells could be re-cultured for further analysis. Under optimized conditions, the capture efficiency of the tumor cells can be as high as 92% ± 2.8%. Capture experiments were also performed on whole blood samples, and the capture efficiency was in a high range of 81-95%, at different tumor cell concentrations. Such a method can potentially be used for CTC sorting from patient blood samples, CTC concentration monitoring, therapeutic guidance and drug dosage choice, and further study of tumors, such as drug screening and tumor mutations.

Magnetic particles assisted capture and release of rare circulating tumor cells using wavy-herringbone structured microfluidic devices.

Three-dimensional (3D) tumor spheroid models have gained increased recognition as important tools in cancer research and anticancer drug development. However, currently available imaging approaches used in high-throughput screening drug discovery platforms, for example, bright-field, phase contrast, and fluorescence microscopies, are unable to resolve 3D structures deep inside (>50 μm) tumor spheroids. In this study, we established a label-free, noninvasive optical coherence tomography (OCT) imaging platform to characterize 3D morphologic and physiologic information of multicellular tumor spheroids (MCTS) growing from approximately 250 to 600 μm in height over 21 days. In particular, tumor spheroids of two cell lines, glioblastoma (U-87MG) and colorectal carcinoma (HCT116), exhibited distinctive evolutions in their geometric shapes at late growth stages. Volumes of MCTS were accurately quantified using a voxel-based approach without presumptions of their geometries. In contrast, conventional diameter-based volume calculations assuming perfect spherical shape resulted in large quantification errors. Furthermore, we successfully detected necrotic regions within these tumor spheroids based on increased intrinsic optical attenuation, suggesting a promising alternative of label-free viability tests in tumor spheroids. Therefore, OCT can serve as a promising imaging modality to characterize morphologic and physiologic features of MCTS, showing great potential for high-throughput drug screening. .

Article	Year
Electrokinetic effects on detection time of nanowire biosensor. Applied physics letters\| PubMed ID: 22550358	2012
Characterization of vascular permeability using a biomimetic microfluidic blood vessel model. Biomicrofluidics\| PubMed ID: 28344727	2017
Magnetic particles assisted capture and release of rare circulating tumor cells using wavy-herringbone structured microfluidic devices. Lab on a chip\| PubMed ID: 28840927	2017
Optical Coherence Tomography Detects Necrotic Regions and Volumetrically Quantifies Multicellular Tumor Spheroids. Cancer research\| PubMed ID: 28904062	2017

Shunqiang Wang

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