title: Isothermal microcalorimetry accurately detects bacteria, tumorous microtissues, and parasitic worms in a label-free well-plate assay.
abstract: Isothermal microcalorimetry is a label-free assay that allows monitoring of enzymatic and metabolic activities. The technique has strengths, but most instruments have a low throughput, which has limited their use for bioassays. Here, an isothermal microcalorimeter, equipped with a vessel holder similar to a 48-well plate, was used. The increased throughput of this microcalorimeter makes it valuable for biomedical and pharmaceutical applications. Our results show that the sensitivity of the instrument allows the detection of 3 × 10(4) bacteria per vial. Growth of P. mirabilis in Luria Broth medium was detected between 2 and 9 h with decreasing inoculum. The culture released 2.1J with a maximum thermal power of 76 μW. The growth rate calculated using calorimetric and spectrophotometric data were 0.60 and 0.57 h(-1) , respectively. Additional insight on protease activities of P. mirabilis matching the last peak in heat production could be gathered as well. Growth of tumor microtissues releasing a maximum thermal power of 2.1 μW was also monitored and corresponds to a diameter increase of the microtissues from ca. 100 to 428 μm. This opens new research avenues in cancer research, diagnostics, and development of new antitumor drugs. For parasitic worms, the technique allows assessment of parasite survival using motor and metabolic activities even with a single worm.
authors.affiliation: Center for Biomechanics and Biocalorimetry, c/o Biozentrum-Pharmazentrum, Basel, Switzerland; Department of Urology, University Hospital of Basel, Basel, Switzerland. Olivier.braissant@unibas.ch.
authors.forename: Olivier
authors.initials: O
authors.lastname: Braissant
authors.forename: Jennifer
authors.initials: J
authors.lastname: Keiser
authors.forename: Isabel
authors.initials: I
authors.lastname: Meister
authors.forename: Alexander
authors.initials: A
authors.lastname: Bachmann
authors.forename: Dieter
authors.initials: D
authors.lastname: Wirz
authors.forename: Beat
authors.initials: B
authors.lastname: Göpfert
authors.forename: Gernot
authors.initials: G
authors.lastname: Bonkat
authors.forename: Ingemar
authors.initials: I
authors.lastname: Wadsö
mesh_terms: D000818:Animals; D001419:Bacteria / Q000201:enzymology / Q000254:growth & development*; D002151:Calorimetry / Q000295:instrumentation* / Q000379:methods*; D056945:Hep G2 Cells; D006801:Humans; D008099:Liver / Q000469:parasitology; D008113:Liver Neoplasms / Q000473:pathology*; D051379:Mice; D012547:Schistosoma / Q000254:growth & development*; D012552:Schistosomiasis / Q000469:parasitology; D012680:Sensitivity and Specificity; D013053:Spectrophotometry / Q000379:methods
keywords: Analytical biotechnology; Cell biology; Diseases; Isothermal microcalorimetry; Metabolic flux analysis