Scale-up of an intensified bioprocess for the expansion of bovine adipose-derived stem cells (bASCs) in stirred tank bioreactors

Cultivated meat is an emerging field, aiming to establish the production of animal tissue for human consumption in an in vitro environment, eliminating the need to raise and slaughter animals for their meat. To realise this, the expansion of primary cells in a bioreactor is needed to achieve the high cell numbers required. The aim of this study was to develop a scalable, microcarrier based, intensified bioprocess for the expansion of bovine adipose-derived stem cells as precursors of fat and muscle tissue. The intensified bioprocess development was carried out initially in spinner flasks of different sizes and then translated to fully controlled litre scale benchtop bioreactors. Bioprocess intensification was achieved by utilising the previously demonstrated bead-to-bead transfer phenomenon and through the combined addition of microcarrier and medium to double the existing surface area and working volume in the bioreactor. Choosing the optimal time point for the additions was critical in enhancing the cell expansion. A significant fold increase of 114.19 ± 1.07 was obtained at the litre scale in the intensified bioprocess compared to the baseline (**p < .005). The quality of the cells was evaluated pre- and post-expansion and the cells were found to maintain their phenotype and differentiation capacity

Photoluminescence Investigations of Cubic Boron Nitride Doped with Neodymium during High-Pressure Synthesis

International audienceMicropowders of cubic boron nitride doped with neodymium are prepared under high-pressure and high-temperature conditions. The phase composition of the micropowders is studied using X-ray diffractometry and X-ray fluorescence analysis. The photoluminescence, photoluminescence excitation spectra, and the life-time of the 4F3/2 excited state of Nd ions introduced into cubic boron nitride are investigated. In photoluminescence spectra of the micropowders, structured bands are recorded in the range of the 4F3/2→4I9/2 and 4F3/2 4I11/2 electronic transitions. A higher intensity of the first structured band indicates that the corresponding photoluminescence in cubic boron nitride doped with neodymium is excited by the “three-level scheme.” It is demonstrated that an increase in the concentration of the neodymium compound in the growth batch leads to the formation of two luminescence centers Nd1 and Nd2 formed by neodymium ions located in different low-symmetry crystal fields in the micropowders. This is confirmed by X-ray diffraction investigations and the study of the photoluminescence decay curves. The 4F3/2 short-lived state is assigned to the Nd ions forming the Nd1 centers, and the long-lived state is attributed to the Nd ions forming the Nd2 centers

Vertical multilayer structures based on porous silicon layers for mid-infrared applications

International audienceIn this work, the fabrication of a porous silicon Bragg reflector and vertical cavity on P+ silicon substrate is investigated for applications in spectroscopic sensing in the mid-infrared (Mid-IR) wavelength range. The complex refractive index of porous silicon layers is measured. Optical vertical devices are then fabricated and characterized by Fourier transform infrared (FTIR) spectrophotometry. This work demonstrates the use of electrochemically prepared Bragg reflectors with reflectance as high as 99% and vertical cavity based on porous silicon layers operating in the mid-IR spectral region (up to 8 µm). Experimental reflectance spectra of the vertical cavity structures are recorded as a function of air exposure duration after thermal annealing under nitrogen flux (N2) and results demonstrate that these structures could be used for spectroscopic sensing applications in the mid-IR (2-8 µm) by grafting specific biomolecules on the porous silicon internal surface