Download KSEA Letters 40-3, Apr. 2012 [pdf] - Korean-American ...

FEATURED ARTICLES
NANO-BIO INTERFACING: LEVERAGING ADVANCES IN SEMICONDUCTOR TECHNOLOGY FOR
BIOLOGICAL RESEARCH
[Hongkun Park]
Professor, Chemistry and Chemical Biology and Physics
Harvard University
Silicon integrated circuits represent an enormously successful paradigm for electronics – they are mass-produced at low cost in silicon
foundries, and yet a chip with a footprint less than a square inch, is a highly integrated superstructure that contains hundreds of millions
of transistors and can process data at gigahertz rates. Moreover, they contain top-down fabricated nanostructures whose sizes are
comparable to important biological molecules and cells. As such, silicon nanostructures and integrated circuits have the potential to
become a unique tool for interrogating living cells and organisms when a proper interface is developed.
Over the past five years, a part of my group at Harvard has been working toward developing nano-bio interfaces that maximally utilize
the advantages offered by these silicon nanostructures. 1-4 Our efforts have been centered on one particular structure: vertical silicon
nanowire (SiNW) arrays. These nanoscale needles, which can be fabricated en masse using standard silicon processing technology,
penetrate through the cellular membrane without compromising cell viability or function, thus providing direct intracellular access to
a living cell. This unique capability, which is difficult to realize by any other means, provides an exciting opportunity for many branches
of biological research. In my laboratory, we have been employing these nanoscale needles (1) to investigate the intracellular circuits
that are responsible for the functions of immune cells, cancer cells, and stem cells by delivering various biological effectors 1-3 and (2) to
monitor and control activities of brain cells in complex neuronal networks and tissues. 4
SiNW nanoinjection for cell circuit perturbation: Efficient delivery of active biological effectors (DNAs, RNAs, peptides, proteins, or
small molecules) into living cells is central to biological research and pharmaceutical screening. For instance, achieving a mechanistic
understanding of intracellular molecular circuits requires systematic perturbation of circuit components and analysis of the resulting
changes in cellular behavior. The success of this strategy depends critically on delivering various biological perturbants into living cells
without compromising their viability or function.
Because many biological effectors do not spontaneously cross the plasma membrane, a host of methods have been developed to deliver
them into cells. Unfortunately, in a variety of primary cells, especially in resting immune cells, many of these techniques have proven
ineffective, inducing non-specific inflammation or cell death. These limitations have severely restricted the use of perturbations in
uncovering the ways in which these cells respond to extra- and intracellular signals, and have been a major obstacle to elucidating the
molecular biology that underlies many hematological cancers. Clearly,
the resistance of these cells to conventional means necessitates the development
of new approaches.
6
Over the past few years, we have developed a new SiNW-based nanoinjection
method that can serve as a minimally invasive and efficient
method for delivering a variety of biomolecules into hard-to-transfect
cells. 1-3 Specifically, we showed that the surface-coated SiNWs could efficiently
administer active biomolecules directly into the cytoplasm of
virtually any type of cell without impacting its viability or function (Figure
1). 1 We then used the method to discover new components of the
Toll-Like Receptor (TLR) network in mouse dendritic cells. 2 We also
applied the method to investigate patient heterogeneity in chronic lymphocytic
leukemia (CLL), the most common adult leukemia in North
America. 3 By perturbing CLL cells using SiNW-mediated siRNA delivery,
we identified three patient response groups, unclassifiable by known
criteria, that required distinctly different clinical treatment schedules.
These examples show that SiNWs can contribute greatly in cell circuit
studies of otherwise hard-to-transfect cells: starting from the cells taken
from a single blood draw, multiple different knockdowns could be used
to simultaneously probe the importance of multiple potential pathways,
enabling a detailed understanding of the intracellular circuitry critical
for cell function and also the development of patient-specific combinatorial
therapies.
Figure 1. SiNW nanoinjection. Upper Image: a confocal image
of a mouse dendritic cell on top of vertical SiNWs. Magenta: cell
membrane, blue: cell nucleus, whilte: SiNW. Lower diagram: a
model of the Polo-like-kinase-dependent pathway of the antiviral
response in mouse dendritic cells.
KSEA LETTERS Vol. 40 No. 3 April 2012