Microfluidic Cell Culture Analog Devices
to Mimic Animal Exposures to Toxins and Drugs
Our group has developed microfluidic in vitro devices that mimic
the response of humans or animals to drugs, toxins, or
nanoparticles. Each device, or cell culture analog (CCA),
contains an array of pseudo tissues that are interconnected by
microfluidic channels. The recirculation of blood surrogate
through the microchannels allows us to study tissue-tissue
interactions, such as the breakdown of a parent compound in
the liver and subsequent transport and reaction in the lung. We
combine these in vitro device experiments with physiologicallybased pharmacokinetic model simulations to predict toxin and
drug dynamics in humans.
We have used micro cell culture analogs (μCCAs) to test the
toxicity of nanoparticles. Because of their small size and surface
to volume ratio, nanoparticles possess unique properties, which
can be utilized in diagnostics and drug delivery. However, little
is known of the particle’s fate within the body and tissues. We
have recently developed a μCCA that combines cell culture
models of the liver and the intestinal epithelium of the
gastrointestinal tract in a physiologically realistic way to
simulate the oral uptake of nanoparticles and other drugs. To
obtain more detailed information from simulations with first pass
metabolism μCCAs, we have developed a microfabricated
gastrointestinal tract model that incorporates an on-chip
membrane and integrated electrodes for transepithelial
resistance measurements.
M. Esch, M. Shuler, Cornell University
Work performed at Cornell NanoScale Facility
Figure 1: Schematic of the μCCA concept. The human body can be
described as a series of interconnected compartments. On a μCCA
device, microfluidic chambers physically represented these compartments
in physiologically relevant order and with physiologically relevant fluid flow
rates and residence times.
The Evolutionary Dynamics of Drug Resistance by
Drug-induced Stress Gradients
Emergence of resistance to antibiotics by bacteria is a growing
problem, yet not well understood. In a microfluidic device
designed to mimic naturally occurring bacterial niches. Evolution
proceeds most rapidly with just the right combination of a large
number of mutants and rapid fixation of the mutants (Goldilocks
point). Using a two-dimensional micro-ecology it is possible to fix
resistance to the powerful antibiotic ciprofloxacin (Cipro) in wildtype E. coli in 10 hours through a combination of extremely high
population gradients, which generate rapid fixation, convolved
with the “just right” level of antibiotic which generates a large
number of mutants and the motility of the organism. The design
of the micro-ecology is unique in that it provides two overlapping
gradients, one an emergent and self generated bacterial
population gradient due to food restriction and the other a
mutagenic antibiotic gradient. Further, it exploits the motility of
the bacteria moving across these gradients, to drive the rate of
resistance to Cipro to extraordinarily high rates. Whole genome
sequencing of the resistant organisms revealed four functional
single nucleotide polymorphisms attained fixation. Rapid
emergence of antibiotic resistance in the heterogeneous
conditions prevailing in the mammalian body may also apply to
the emergence of drug resistance during cancer chemotherapy.
G. Lambert, R. H. Austin, Princeton University
Work performed at Cornell NanoScale Facility
(A) An overview of the entire micro-ecology, showing the flow of the
nutrient streams and the nutrient+Cipro containing streams. The
nutrient stream is x1 LB broth, while the nutrient+Cipro stream is x1 LB
broth + 10 μg/mL Cipro. (B) Image of the expected Cipro concentration
using the dye fluorescein as a marker. The asymmetry of the pattern at
the Goldilocks points is due to the direction of the flow. (C) Scanning
electron microscope (SEM) image of the area of the array in (A)
outlined by the box. Each hexagon is etched down 10 microns, the
interconnecting channels are 10 microns deep and 10 microns wide.
(D) SEM image of the nanoslits at the micro-ecology periphery. The
nanoslits are etched down 100 nm and are 6 microns wide and 10
microns long.
Proc. of SPIE Vol. 7929 (2011)