Optical density measurement has been used for decades to determine the microorganism concentration and more rarely for mammalian cells. Although this measurement can be carried out at any wavelength, studies report a limited number of measurement wavelengths, mainly around 600 nm, and no consensus seems to be emerging to propose an objective method for determining the optimum measurement wavelength for each microorganism. In this article, we propose a method for analyzing the absorbance spectra of ESKAPEE bacteria and determining the optimum measurement wavelength for each of them. The method is based on the analysis of the signal-to-noise ratio of the relationships between concentrations and optical densities when the measurement wavelength varies over the entire spectral range of the absorbance spectra measured for each bacterium. These optimum wavelengths range from 612 nm for Enterococcus faecium to 705 nm for Acinetobacter baumannii. The method can be directly applied to any bacteria, any culture method, and also to any biochemical substance with an absorbance spectrum without any particular feature such as an identified maximum.

The work described here concerns the fabrication of cost-effective biosensors that permit to amplify a fluorescence signal without a complex nano-structuration of the surface. The idea is to put to profit the natural pseudo nano-structuring that is observed when depositing metallic layers by various micro-fabrication techniques. This new architecture consists of a glass substrate. A gold film is deposited on the top of it and a silica layer onto the gold. A dye (Cy5) is then absorbed onto the surface and the fluorescence intensity is measured. This intensity depends on the distance between the dye and the metal. It also depends on the properties of the metallic film. The goal of the work is to determine which gold deposition method leads to the highest fluorescence amplification and which silica thickness is required to achieve this amplification.

During intracytoplasmic sperm injection (ICSI) attempts, oocytes reaching metaphase II are microinjected. A morphological examination under a microscope is the usual method for determining oocyte maturity. The level of oocyte maturity is based on the meiotic status (Germinal Vesicle, metaphase I and metaphase II) of the oocytes with respect to their increasing maturity. In this letter, we summarize the studies conducted to analyze cytoplasm maturity using various microsystems and image processing. Optical microsystems are used to measure the transmission spectra and refractive index of the oocytes. We compared the transmission spectra measurements to the transmission electron microscopy results. Karhunen–Loeve transform is also used to evaluate the maturity of the oocytes. To summarize, optical analysis techniques are a minimally invasive technology allowing cytoplasm maturity to be assessed. Oocytes should not only be qualified in terms of GV, MI or MII, but also regarding their temporal evolution over the course of these maturation stages. The ultimate aim of this work is to describe the maturation of the oocytes by a trajectory in a multidimensional space and to determine when would be the best time for successful fertilization.

There are various difficulties which reduce the percentage of success in human in vitro fertilization (IVF). One of them concerns the choice of the oocyte to be fertilized. Up to now, the selection of the mature cell to be employed essentially relies on subjective criteria. Most biologists visually estimate the morphological properties of the oocyte. Some of the microsystems we are currently developing in our laboratory propose a solution to the objective determination of some of the oocyte properties, with the ulterior motive of grouping the microsystems in a single Lab-On-Chip (LOC). In this paper, we present these microsystems or techniques (microfluidic platform, microoptics, micromechanics, and image processing) together with the first experimental results that have been achieved. To conclude, we would like to say that the systems we describe are unique and that the results we have obtained up to now cannot be achieved using any other IVF techniques. Also, these studies have been approved by the local ethics committee.