Piezoelectrically driven vertical cavity acoustic transducers for the convective transport and rapid detection of DNA and protein binding to DNA microarrays with SPR imaging--a parametric study.

Mixing within the microdomain is limited because convective mixing cannot be achieved since diffusion dominates as the main form of transport. Hence microassays can take on the order of 1 to 72 h, without the aid of a passive or active mixer to shorten the time of transport of a target molecule to a probe (Lai et al., 2004). Liu et al. (2002, 2003) developed a low cost cavitation microstreaming based mixer which is easy to implement and use, but no comprehensive study has been done to optimize such a mixer for various applications. We present a study of the effects of various frequencies and cavity parameters on mixing using dye and surface based assays with protein, DNA, and nanoparticles to obtain an optimum mixing frequency and configuration for a wide range of assay applications. We present a novel method to monitor real time binding using surface plasmon resonance imaging (SPRI) coupled with a vertical cavity acoustic transducer (VCAT) micromixer for various biomolecule surface assays. The combination of VCAT and SPRI allows assay signal saturation within one minute while conserving reagent volume. The kinetic rate constant for adsorption (k(a)) and desorption (k(d)) as well as the limit of detection (LOD) of 5 nM for the DNA duplex formation are reported using this VCAT micromixer.