Magnetic Micro- and Nanospneres as Tools in Bio-Chip Incubation Processes

DNA microarrays represent a major technological leap in modern genetics. Generally, the target strands are transported to the probe spots during hybridization in classic DNA chip experiments by diffusion and Brownian motion only. Studies by different groups have shown that an agitation of the hybridization solution increases the efficiency of the binding between target and probe, which intensifies the measurable fluorescent signal level and raises the sensitivity. In this work, we introduce a new system for enhancing the signals and reducing the hybridization times required for bio-chip analysis. Additionally, the signal homogeneity across the microarray, which is often also an issue, is further improved. The presented system is based on active agitation within the hybridization buffer by the controlled movement of magnetic micro- and nano-particles inside the analyte. For this method no extra analyte volume is required. A remarkable gain in the specific fluorescence signals on a DNA chip for detecting and identifying specific bacteria (Enterococcus faecium) demonstrates the enhanced sensitivity of the device relative to standard reference experiments within the same hybridization time. While unspecific signals remain identical, the specific signals show an average fourfold increase, thus demonstrating the substantially higher sensitivity that can be achieved by the presented device. Moreover, the system can easily be implemented to existing biochip applications and allows universal operation in the field of molecular diagnostics.