Xichen Zhang

PhD Student

E-mail: x.zhang-4@utwente.nl
+31 53 489 2456
+31 53 489 3511
Faculty of Science and Technology
Medical Cell BioPhysics (MCBP)
CR4429, Drienerlolaan 5
P.O. Box 217, 7500 AE
Enschede, the Netherlands

Project background

The “InstantCount” project develops printed microfluidic cell counting chambers for point-of-care blood tests, with the goal to provide diagnostics to resource-poor settings that do not have access to lab testing. The concept of the test is based on the release of cell staining reagents from hydrogels to realize on-chip sample preparation. Based on this principle, we have demonstrated a simple and affordable CD4 count, a test that is used for HIV staging, and are currently developing printing techniques to fabricate these tests in an affordable and reproducible way. At the same time, new assays, such as a malaria test and a differential white blood cell count based on the same principle are developed and new materials for the release of reagents on microfluidic chips are tested.

Research Goals

As part of “InstantCount project”, my research goal is to enable on-chip sample preparation in the cell counting chamber by integrating reagent loaded hydrogel films in the chamber. My work includes screening and characterizing of hydrogel materials capable of releasing DNA stains and antibody in the chamber within a required time window. The goal is to better understand the interplay of swelling, release and matrix dissolution on the stability of the film during sample inflow and on the availability of reagent during incubation time. Optimizing the preparation of hydrogel films (film composition, deposition method, film drying, film storage, etc.) in the chamber is the final step for desired on-chip release profiles.

On-chip reagent release

A flow system shown in Fig. 1 is established to realize real-time and in situ monitoring of on-chip antibody release from gelatin films. Fig. 2 illustrates the kinetics of antibody release from gelatin, which complies with diffusion controlled mechanism.

D:\Profiles\ZhangX4\Desktop\Figure\chapter 2\schematic drawing\PhD project.tif
Figure 1. Schematic of the fluidic chip. The medium passes through the chamber and the imaging setup monitors the fluorescence change of the film.

Figure 2. Measured release kinetics of antibody from film fit to Mt/Mtotal=(t/τ)1/2 (solid line)

Available student Project: On-chip release from swollen hydrogel

We have identified several alternatives to gelatin with potential to achieve on-chip sample preparation in the counting chamber. The goal of this project is to reveal the release kinetics of antibody and DNA stain from chitosan, and understand how the characteristics (thickness, content of acetic acid, storage time etc) of chitosan films can influence the release of antibody and DNA stain. With this information, preparing chitosan films releasing antibody and DNA stain in desired kinetics for “InstantCount” application will be the final goal.

We are looking for a skilled and innovative student interested in working on an applied subject with a high relevance for point-of-care diagnostics. Especially students with a background (or interest) in analytic chemistry or material chemistry would be a good match. Programming skills for image analysis (ImageJ) would be a plus.

Please feel free to contact me @ x.zhang-4@utwente.nl for further discussion.