| Molecular recognition is observed in all biological systems, governing essential interactions between cells and biomolecules. My thesis work, consisting of two sub-projects, capitalizes on select recognition events replicated in vitro for developing microfluidic biosensors capable of detecting trace analytes within complex matrices such as liquid food or whole blood. Specifically, I have focused on (1) rapid and reliable detection of a poisonous biowarfare agent, botulinum neurotoxin (BoNT), and (2) the capture of rare circulating tumor cells (CTCs) present in the peripheral blood of breast and prostate cancer patients. Both detection platforms required the creation of a solid phase specific for the analyte of interest, whether it be a biomolecule (BoNT) or a cell (CTC) and produced outputs with different implications depending on the molecular recognition event.;For BoNT sensors, peptide substrates mimicking in vivo neuronal proteins were synthesized and attached to hydrogels, gold surfaces, or beads. The versatility of bioconjugation chemistry permitted exploration of various sensing modalities such that the optimal platform could be developed for sensing as little as 3 pg/mL BoNT type A in 3 h or positively identifying BoNT type B in milk in only one hour. The development and implementation of each microfluidic BoNT sensor will be introduced and discussed separately to highlight individual methods, advantages, and results.;In the second study, antibody-laden surfaces were explored as a means of isolating CTCs in microchannels for downstream analysis. It was hypothesized that the use of antibodies specific for epithelial cells would recognize and capture the CTCs, allowing other non-epithelial cells to be eluted. Various surface compositions were tested in addition to two macroscale sample pre-processing steps (density gradient centrifugation and magnetic bead selection) in order to optimize CTC capture efficiency and purity. |
