Looking into Living Cell Systems: Planar Waveguide Microfluidic NMR Detector for in Vitro Metabolomics of Tumor Spheroids.

The complex cell metabolism and its link to oncogenic signaling pathways have received huge interest within the last few years. But the lack of advanced analytical tools for the investigation of living cell metabolism is still a challenge to be faced. Therefore, we designed and fabricated a novel miniaturized microslot NMR detector with on-board heater integrated with a microfluidic device as NMR sample holder. For the first time, a tumor spheroid of 500 µm diameter and consisting of 9000 cells has been studied noninvasively and online for 24 h. The dynamic processes of production and degradation of 23 intra- and extracellular metabolites were monitored. Remarkably high concentrations of lactate and alanine were observed, being an indicator for a shift from oxidative to glycolytic metabolism. In summary, this methodical development has proven to be a successful analytical tool for the elucidation of cellular functions and their corresponding biochemical pathways. Additionally, the planar geometry of the microslot NMR detector allows the hyphenation with versatile lab-on-a chip (LOC) technology. This opens a new window for metabolomics studies on living cells and can be implemented into new application fields in biotechnology and life sciences.

Isolation and amplification of mRNA within a simple microfluidic lab on a chip.

The major modules for realizing molecular biological assays in a micro-total analysis system (µTAS) were developed for the detection of pathogenic organisms. The specific focus was the isolation and amplification of eukaryotic mRNA within a simple, single-channel device for very low RNA concentrations that could then be integrated with detection modules. The hsp70 mRNA from Cryptosporidium parvum was used as a model analyte. Important points of study were surface chemistries within poly(methyl methacrylate) (PMMA) microfluidic channels that enabled specific and sensitive mRNA isolation and amplification reactions for very low mRNA concentrations. Optimal conditions were achieved when the channel surface was carboxylated via UV/ozone treatment followed by the immobilization of polyamidoamine (PAMAM) dendrimers on the surface, thus increasing the immobilization efficiency of the thymidine oligonucleotide, oligo(dT)25, and providing a reliable surface for the amplification reaction, importantly, without the need for blocking agents. Additional chemical modifications of the remaining active surface groups were studied to avoid nonspecific capturing of nucleic acids and hindering of the mRNA amplification at low RNA concentrations. Amplification of the mRNA was accomplished using nucleic acid sequence-based amplification (NASBA), an isothermal, primer-dependent technique. Positive controls consisting of previously generated NASBA amplicons could be diluted 10(15) fold and still result in successful on-chip reamplification. Finally, the successful isolation and amplification of mRNA from as few as 30 C. parvum oocysts was demonstrated directly on-chip and compared to benchtop devices. This is the first proof of successful mRNA isolation and NASBA-based amplification of mRNA within a simple microfluidic device in relevant analytical volumes.