1. 제 목 : Enabling technologies in micro- and nanoscales for biological applications

2. 연 사 : Dr. Nakwon Choi
             (Center for BioMicrosystems, Brain Science Institute, KIST)

3. 일 시 : 2013년 3월 15일 (금) 16:30-17:30

4. 장 소 : 301동 105호

5. 내 용 :
   Rapidly emerging tissue engineering, which is interdisciplinary medical science and
technology, has gained attention to develop implantable tissue constructs via in vitro culture of cells
seeded in three-dimensional (3-D) scaffolds formed in biomaterials. Micro-/nano-engineering
techniques have demonstrated promising proof-of- concept in developing potentially valuable in vitro
culture systems. First, we present the development of microfluidic scaffolds that are formed by
embedding microfluidic networks directly within biomaterials. Experiments with chondrocytes in
calcium alginate demonstrated that these embedded microchannels enable the maintenance of a
uniform metabolic environment within the bulk of the scaffold and the creation of distinct soluble
environments experienced by cells in their 3-D environment. The generalization of the process into
type I collagen allows for the embedded microchannels to serve as a template for microvascular
endothelialization within a matrix that can support cellular remodeling. In the new experimental
context offered by these microfluidic scaffolds, we present detailed mass transport considerations in
microfluidic biomaterials. Such considerations include quantitative measurements of 1) diffusion of
non-reactive solutes and 2) metabolic activity of reactive solutes such as oxygen, which should be
also used in designing and operating microfluidic biomaterials. In addition, it has become more
important to monitor cellular microenvironment and to analyze biomolecules in both physiological and
pathological processes. Emerging interdisciplinary science/engineering fields allow for the
development of micro-/nano-scale sensing and detection technologies that can serve as enabling
tools for such applications. We present the development of polymeric nanoparticles loaded with an
oxygen-sensitive phosphor to perform quantitative measurements of the concentration of oxygen
within three-dimensional (3-D) tissue cultures in vitro and blood vessels in vivo. We synthesized a
customized ruthenium (Ru)-phosphor and incorporated it into poly(urethane acrylate nonionomer)
(PUAN) nanoparticles via self-assembly. We demonstrate that the encapsulated phosphor is nontoxic
with and without illumination. We evaluated two distinct modes of employing the
phosphorescent nanoparticles for the measurement of concentrations of oxygen: 1) in vitro, in a 3-D
microfluidic tumor model via ratiometric measurements of intensity with an oxygen-insensitive
fluorophore as a reference, and 2) in vivo, in mouse vasculature using measurements of
phosphorescence lifetime. With both methods, we demonstrated micrometer-scale resolution and
absolute calibration to the dissolved oxygen concentration. Finally, we present the quantification of
unmodified full length-transcripts using poly(ethylene) glycol diacrylate (PEGDA) hydrogel
microparticles synthesized via Stop Flow Lithography (SFL). We show that PEG600 serves as an
effective porogen to allow for the capture of large (~1,000 to 3,700 nt-long) mRNAs. Our relatively
simple hydrogel-based mRNA detection scheme uses a multi-biotinylated universal label probe and
provides assay performance (limit of detection ~6 amol of an in vitro transcribed model target)
comparable to an existing commercial bead-based technology which uses branched DNA (bDNA)
signal amplification. We demonstrate a 3-plex mRNA detection, without cross-reactivity, using
Shapeencoded “intraplex” hydrogel microparticles.

6. 연사약력 :
[학력]
 08.2004-12.2009  Ph.D. in Chemical Engineering, M.S. in Chemical Engineering
                         School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, NY
 03.1997-02.2004  B.S. in Chemical Engineering, Seoul National University, Korea

[약력]
 01.2012-present  Senior Research Scientist, Center for BioMicrosystems, Brain Science Institute, KIST
 06.2010-12.2011  Presidential Postdoctoral Fellow, Novartis Institutes for Biomedical Research (NIBR)   
                         Cambridge, MA
 01.2010-05.2010  Postdoctoral Associate, School of Chemical and Biomolecular Engineering,
                         Cornell University, Ithaca, NY

7. 문 의 : 기계항공공학부 김호영 교수(hyk@snu.ac.kr)