The Roper laboratory develops new methods and techniques in order to investigate biological signaling. Our main biological interest is how the secretion and coupling of islets of Langerhans contribute to proper glucose clearance in the body. The reason why we are interested in the biology of glucose handling is that defects in this process are associated with metabolic diseases, such as type 2 diabetes.
We have developed multiplexed electrophoretic immunoassays to simultaneously measure the release of insulin, glucagon, and islet amyloid polypeptide from islets of Langerhans. We are now incorporating these assays on microfluidic devices using novel optical detection tools to increase the temporal resolution of peptide release. Figure 1 shows a microfluidic device used to measure secretion of peptides from islets of Langerhans. A blue and red laser are incident on the device giving it the purple color.
To investigate how the numerous islets within a pancreas can synchronize their output to produce pulses of hormones in the bloodstream, we are developing microfluidic devices that produce complex temporal gradients of stimulants. These waveforms are delivered to populations of islets to test their ability to synchronize. Figure 2 shows a contour map of the responses from multiple islets to a glucose wave. During the last 20 minutes of the experiment, the islets begin to synchronize together as seen by the vertical stripes.
Other projects in the lab are ongoing and include the use of finite element analysis to model the microfluidic devices and biological cells, interfacing digital microfluidic devices which use droplets instead of continuous flow streams (Figure 3) to an electrospray ionization interface, synthetic reactions within microfluidic devices, and infrared-mediated PCR amplification of DNA.
C. A. Baker, M. G. Roper Online coupling of digital microfluidic devices with mass spectrometry detection using an eductor with electrospray ionization Anal. Chem.2012, DOI: 10.1021/ac300100b
Y. Yu, B. Li, C. A. Baker, X. Zhang, M. G. Roper Quantitative polymerase chain reaction using infrared heating on a microfluidic chip Anal. Chem.2012, DOI: 10.1021/ac203307h
C. T. Duong, M. G. Roper A microfluidic device for the automated derivatization of free fatty acids to fatty acid methyl esters Analyst2012, 137, 840-846
X. Zhang, A. Daou, T. M. Truong, R. Bertram, M. G. Roper Synchronization of mouse islets of Langerhans by glucose waveforms Am. J. Physiol. Endocrinol. Metab.2011, 301, E742-E747
C. Guillo, T. M. Truong, M. G. Roper Simultaneous capillary electrophoresis competitive immunoassay for insulin, glucagon, and islet amyloid polypeptide secretion from mouse islets of Langerhans J. Chromatogr. A2011, 1218, 4059-4064