Sporesat: A Nanosatellite Platform Lab-on-a-Chip System for Investigating Gravity Threshold of Fern Spore Single-Cell Calcium Currents

Abstract

SporeSata lab-on-a-chip (LOC) centrifuge platform designed for integration as the payload of a small (5.5 kg), freeflying satellitehas been developed to determine the gravitational thresholds for calcium-ion channel activation of a single-cell spore from the fern Ceratopteris richardii. This fern is an important model system for gravity-directed plant-cell development during variable-gravity conditions attainable only in space flight. Calcium-ion channel activity is measured by photolithographically defined calcium ion-selective electrodes (ISEs) at opposite ends of each spore. Artificial gravity is created by rotating a disk-like platform that contains the spores in wells along with the calcium ISEs.Ground experiments reveal a maximum calcium concentration ratio at 2.2xg, between micro-ion-selective electrodes near the "top" and "bottom" ends of the spore, indicating an increasing calcium concentration at one "end" of the fern spore with respect to the other. Confocal micrographs of rhizoid formation confirm the light-induced germination. SporeSat is a spaceflight experiment that will take ~ 4 days; data will be telemetered to Earth over ~ 100 days.

Nanosatellites for Biology in Space: In Situ Measurement of Bacillus subtilis Spore Germination and Growth after 6 Months in Low Earth Orbit on the O/OREOS Mission

“…The shorter durations of most studies were due to two factors. First, the primary goal of the initial studies was to understand microgravity effects [9][10][11][14][15][16], for which there was no reason to delay growth and analysis beyond the time at which spacecraft stabilization occurred (several hours to a few days after deployment). Second, the first two missions, GeneSat-1 and PharmaSat, traversed the steep part of the learning curve for biological nanosat missions-among other things, a very intimate proximity of salty water and electronics-meaning that longevity of the growth-and-measurement system in space for many weeks was far from guaranteed.…”

“…SporeSat-1 was deployed en route to the ISS at an altitude of 325 km and an inclination of 51.6 • ; it re-entered Earth's atmosphere 47 days later. The mission's science objective was to measure germination of fern spores (Ceratopteris richardii) as a function of gravity level using differential pairs of calcium ion-sensitive electrodes [15,16]. The experiment was initiated by increasing temperature to 29 • C and establishing artificial gravity via its two 50-mm microcentrifuges.…”

Space Biology Research and Biosensor Technologies: Past, Present, and Future

“…Four years later, SporeSat was launched, employing unique lab-on-a-chip devices termed biology compact discs (bioCDs). These devices utilized ion-sensitive electrodes to measure concentrations of calcium in fern spores, and were rotated to simulate artificial gravity using miniaturized centrifuges, validating novel CubeSat technologies for biological experiments in space [ 29 ]. EcAMSat launched in 2017 as the largest biological satellite thus far, and was the first 6U CubeSat to be deployed from the ISS [ 8 ].…”

Developing Technologies for Biological Experiments in Deep Space

“…Four years later, SporeSat was launched, employing unique lab-on-a-chip devices termed biology compact discs (bioCDs). These devices utilized ion-sensitive electrodes to measure concentrations of calcium in fern spores and were rotated to simulate artificial gravity using miniaturized centrifuges, validating novel CubeSat technologies for biological experiments in space [16]. EcAMSat launched in 2017 as the largest biological nanosatellite thus far, and as the first 6U CubeSat to be deployed from the ISS [5].…”