Enzymatic outside-in cross-linking enables single-step microcapsule production for high-throughput three-dimensional cell microaggregate formation.

Cell-laden hydrogel microcapsules enable the high-throughput production of cell aggregates, which are relevant for three-dimensional tissue engineering and drug screening applications. However, current microcapsule production strategies are limited by their throughput, multistep protocols, and limited amount of compatible biomaterials. We here present a single-step process for the controlled microfluidic production of single-core microcapsules using enzymatic outside-in cross-linking of tyramine-conjugated polymers. It was hypothesized that a physically, instead of the conventionally explored biochemically, controlled enzymatic cross-linking process would improve the reproducibility, operational window, and throughput of shell formation. Droplets were flown through a silicone delay line, which allowed for highly controlled diffusion of the enzymatic cross-linking initiator. The microcapsules' cross-linking density and shell thickness is strictly depended on the droplet's retention time in the delay line, which is predictably controlled by flow rate. The here presented hydrogel cross-linking method allows for facile and cytocompatible production of cell-laden microcapsules compatible with the formation and biorthogonal isolation of long-term viable cellular spheroids for tissue engineering and drug screening applications.

Balloon-borne ultraviolet stellar echelle spectrograph.

During the nights of 19, 20 May 1976 and 16, 17 September 1976, an 800-kg astronomical payload, developed by the NASA Johnson Space Center at Houston and the Astronomical Institute at Utrecht, was floating at 40-km altitude and recorded high-resolution uv spectra of stars. The spectral region of 200-340 am was covered with a spectral resolution of 0.01 nm. The optical system consisted of a 40-cm diam telescope with 1-sec of arc pointing capabilities, an echelle spectrograph working in spectral orders 66 to 112 and a SEC-vidicon integrating detector. Due to the high spectral simultaneity gain of the system 53 complete spectra of thirty-three different stars, with spectral types between 09.5 and M2 and with visual magnitudes between 0 and 4.5, could be obtained during the two nights of observation. Ozone in the residual atmosphere above 40 km reduces the atmospheric transmission around 250 nm to approximately 0.1, but with suitable integration times also in this region stars can be studied spectroscopically from balloon altitudes.