Probe Adsorption

1. *jennifer.gerasimov@huskers.unl.edu http://ellipsometry.unl.edu • The formation and function of biotechnologically relevant functional thin films was studied in real-time using tandem spectroscopic ellipsometry (SE) and quartz crystal microbalance (QCM). Simultaneously monitoring changes in film thickness given by each technique allows us to derive the porosity of the bioactive layer under investigation and gives clues about the morphology of the surface-confined biomolecules. A correlation of structural morphology with film function makes possible the directed optimization of bioactive films based on measurable parameters. We present the results of two investigations involving the formation of bioactive hybrid materials. In the study of DNA-incorporating monolayers for sequence-specific DNA detection, two DNA probes were analyzed for their ability to specifically recognize their complement in solution. The formation of protein layers on smooth and nanostructured surfaces was studied for its utility as a scaffold for whole-cell immobilization and future work in gene transfer studies. Instrument Theory liquid inlet liquid outlet • SE thickness (dSE) gives the thickness of adsorbed organic layer, excluding solvent. • QCM thickness is derived from total adsorbed mass • Assuming equivalence of solvent and adsorbate densities, porosity () may be expressed as a ratio of the thickness measured in SE to the thickness measured in QCM light source detector optical window optical window polarizer analyzers polarized light polarized light affected by sample surface gasket QCM-D control Electrochemical DNA Sensor Target Detection Probe Adsorption non-complement DNA complement target buffer buffer buffer eT S S unbound eT S S S S S S S S S S S S S S S S S S S S S S S S S dSE dSE dSE dQCM dQCM dQCM f0v bound Elevated Probe • Electron transfer (eT) to the labeled, surface-bound stem-loop DNA probe is greatly impeded upon hybridization with complementary target. • Decrease in eT efficiency is monitored using alternating current voltammetry • SE/QCM provides structural information about DNA layer formation non- complementary target complementary target buffer aligned S S S S S S S S S Flush Probe Titanium Nanocolumns on Gold • In the near future, we will add an electrochemistry module to the SE/QCM to study the relationship between electrochemical trends and film morphology. We will direct further efforts toward the following goals: Flat Surface 1.0 12 10 0.8 8 Structured Thin Film 0.6 6 Substrate 0.4 4 2 0.2 0 0 60 80 0 120 20 40 100 Fibronectin Study surface functionalization for cell adhesion and gene transfer Aptamer-based small molecule detectionº Nanostructured Surface S S S S S S S S S S S S S S S S S S • extracellular matrix protein • facilitates cell adhesion, spreading, and proliferation • diverse applications in biotechnology and engineering of hybrid materials Monitor conformational change in surface-confined proteinsºº Characterize peptide-based sensors for antibody detection º Helmholtz Association of German Research Centres (2009, April 7). Fitting Pieces For Biosensors. ScienceDaily. Retrieved August 7, 2011, from http://www.sciencedaily.com­ /releases/2009/04/090407105149.htm ººadapted from http://webs.wichita.edu/mschneegurt/biol103/lecture16/normal_rogue.gif