Volume 23, Issue 6, September 2009

Harry Heinzelmann,¹ André Meister,¹ Philippe Niedermann,¹ Joanna Bitterli,¹ Jérôme Polesel-Maris,¹ Martha Liley,¹ Michael Gabi,² Pascal Behr,² Philipp Studer,² Janos Vörös,² and Tomaso Zambelli²
1. Swiss Center for Electronics and Microtechnology, CSEM SA, Neuchâtel, Switzerland. 2. Laboratory of Biosensors and Bioelectronics, Institute for Biomedical Engineering, ETH Zurich, Zurich, Switzerland
A nanodispenser (NADIS) has been developed, based on a standard AFM, which allows local microinjection into living cells. A key advantage is the precise controlling of the forces applied, so that damage to the sample is minimized. The heart of the system is an AFM-like cantilever with a hollow core and a tip with an aperture at the apex. The hollow cantilever acts as a microfluidic channel that connects external fluidics devices such as pumps and reservoirs to a dispensing tip located at the free end of the cantilever. In this article we describe the technology of NADIS and give some examples showing its use in injecting into individual living cells and subcellular structures.

Agneta Robertson¹ and Sandor Nietzsche² 1. Department of Pedodontics, Institute of Odontology at the Sahlgrenska Academy, University of Gothenburg, Göteborg, Sweden. 2. Centre of Electron Microscopy, Friedrich-Schiller-Universität Jena, Germany
The aim of this study was to investigate the presence, intensity, and location of bacterial penetration into the dentinal tubules, in traumatized primary teeth, using two techniques: light microscopy after Brown and Brenn staining and scanning electron microscopy. The material comprised ten traumatized primary teeth. The teeth were scanned for stainable bacteria at three positions, selected after findings in the light
microscopy. The results clearly indicate that the identification of bacteria was in good agreement between the two methods used. Scanning electron microscopy may be a good complement to the Brown and Brenn staining to describe the invasion of bacteria in dentinal tubules.