Jung Woo Hong

Quantitatively controlled fabrication of uniaxially aligned nanofibrous scaffold for cell adhesion

In light of tissue engineering, development of a functional and controllable scaffold which can promote cell proliferation and differentiation is crucial. In this study, we introduce a controllable collection method of the electrospinning process for regularly-distributed and uniaxially oriented nanofiber scaffold and evaluate the effects of aligned nanofiber density on adhesion of dermal fibroblasts. The suggested spinning collector features an inclined void gap, which allows easy transfer of uniformly aligned fibers onto other surfaces. By undergoing multiple transfers, the density of the nanofibers can be quantitatively controlled. The resultant polycaprolactone (PCL) nanofibers had well-defined nanotopography in a 400-600nm range. Human dermal fibroblasts were seeded on aligned nanofiber scaffolds of different densities achieved by varying the number of transfers. Cell morphology and actin stress fiber formation was accessed after seven days. The experimental results indicate that the contact guidance of the cells along the fiber alignment can be more activated with more than one guidance feature on a cell; that is, the high density of fiber is attained in so much that fiber spacing gets below the cell size.

Comparative study on the differential mechanical properties of human liver cancer and normal cells

Abstract Although cancerous cells and normal cells are known to have different elasticity values, there have been inconsistent reports in terms of the actual and relative values for these two cell types depending on the experimental conditions. This paper investigated the mechanical characterization of normal hepatocytes (THLE-2) and hepatocellular carcinoma cells (HepG2) using atomic force microscopy indentation experiments and the Hertz–Sneddon model, and the results were confirmed by an independent de-adhesion assay. To improve the reliability of the data, we considered the effects of tip geometry and indentation depth on the measured elasticity of the cells. This study demonstrated that THLE-2 cells had a higher elastic modulus compared with the HepG2 cells and that this difference was more significant when a conical tip was used. The inhibitor study indicated that this difference in the mechanical properties of THLE-2 and HepG2 cells was mainly attributed to differential arrangements in the cytoskeletal networks of actin filaments. An independent de-adhesion assay also confirmed that THLE-2 cells had a higher elastic modulus compared with the HepG2 cells, which resulted in a shorter time constant for cellular contractility.

Quantitative analysis of bacterial preference for cancer secreting proteins

We present a robust microfluidic platform for stable generation of multiple chemical gradients simultaneously using in situ self-assembly of microparticles in microchannels and show the potential of the proposed system for analysis of bacterial preference for cancer cell secreting proteins. We demonstrate the proof of concept as a preferential chemotaxis assay of bacteria toward multiple chemical sources. Aspartate induces the most preferential chemotaxis over galactose and ribose. The microfluidic device can be easily fabricated with simple and cost effective process based on capillary pressure and evaporation for particle assembly. The assembled particles create uniform porous membranes in microchannels and its porosity can be easily controlled with different size particles. Moreover, the membrane is biocompatible and more robust than hydrogel based porous membranes. The proposed system is expected to be a useful tool for characterization of bacterial responses to various chemical sources, screening of bacterial cells, synthetic biology, and understanding many cellular activities.