Xiaoxiao chen

    Levich Institute                       Maldarelli Group                 Chemical Eng. Dept.      

 

I am a Ph.D. candidate working with Prof. Charles Maldarelli. My research interest is biosensor application for pathogen detection in a microfluidic format. Platforms which can display cell membrane ligands and receptors as a microarray library of probes for screening against a target are essential tools in drug discovery, biomarker identification, and pathogen detection. Membrane receptors and ligands require their native bilayer environment to retain their selectivity and binding affinity, and this complicates displaying them in a microarray platform. In my research study, a design is developed in which the probes are first incoporated in supported lipid bilayers formed around micron-sized particles (lipobeads), and the microbeads themselves are then arrayed on a surface by hydrodynamic capture in a microfluidic obstacle course of traps (see in figure 1). Screening assays are undertaken directly in the device after assembly, by streaming a fluorescently labeled target through the device and detecting the bead fluorescence (see in figure 2). I have also demonstrated the use of the microfluidic bead array of membrane receptors as a sensor for the multiplexed detection of bacterial pathogens.




















Figure1. Lipobeads microarray assembled by hydrodynamic capture.



















Figure2. DMPC Lipobeads array displaying biotin (5 mol% relative to the DMPC) screening for NeutrAvidin-FITC



Kinetic and Diffusive Mass Transfer in the Binding of Targets to Probes


In the screening assay study, I am interested in the dynamic response of the microarray. Because the beads are localized in the traps, most of the streamlines, instead of passing through the gap between the traps, tend to go around the trap. This reduced convection increases the size of diffusion boundary layers. For this reason, diffusion can play an important role on the dynamic response of the microbeads array. We present the numerical simulation (COMSOL) for the surface density of bound targets as a function of time for different ratios of the surface reaction rate to the bulk diffusion (Damkohler number) and the convection of target to diffusion (Peclet number). Values for these numbers are determined for which the dynamic response is either diffusion or kinetically limited. The theory is compared to experiments in which the dynamic response of the microbead array is measured for the binding of the target NeutrAvidin to the probe biotin on the bead surface.

















Figure3. COMSOL simulation of the hydrodynamic flow through the unit cell of an open array of four traps, showing the limiting trajectory for capture (a), the streamlines (b) and the velocity along the midplane of the channel (c).


Some of the tools I use for my research include microfluidic devices, micro-scale fabrication techniques, confocal laser scanning microscopes (CLSM), optical microscopes, high-speedd cameras, dynamic light scattering (DLS).



PUBLICATIONS

                                                                       

  1. 1.“A Lipobead Microarray Assembled by Particle Entrapment in a Microfluidic Obstacle Course and Used For the Display of Cell Membrane Receptors,” Xiaoxiao Chen, Shahab Shojaei Zadeh, M. Lane Gilchrist, and Charles Maldarelli, Lab On a Chip, DOI 10.1039/C3LC50083G, 2013.


  1. 2.“Microfluidic Microbead Arrays for High Throughput Screening and Biosensing-Kinetic and Diffusive Mass Transfer in the Binding of Targets to Probes Displayed on the Bead Surface,” Xiaoxiao Chen, Thomas Leary and Charles Madarelli. Biomicrofluidics, submitted, 2013.


  1. 3.“A Lipobead Microarray For the Detection of Cholera Toxin,” Xiaoxiao Chen and Charles Madarelli. (in preparation, 2013).


4.“Experimental Study of Mass Transfer Limitations in A Bead-Based      Microfluidic Microarray Using Neutravidin Biotin Binding,” Xiaoxiao Chen and Charles Madarelli. (in preparation, 2013).









Levich Institute and

Dept. of Chemical Engineering

City College of New York

140th Street and Convent Avenue

New York, NY 10031

Email: xchen@che.ccny.cuny.edu

Phone: 212-650-7093