# Lab-on-Chip Culturing System for Fungi--Towards Nanosatellite Missions
## 2 Materials and Methods  
### Biomedical Experimentation in Space--Tools  
Most astrobiological research is generally carried out on the International Space Station (ISS). Apart from the cell cultivation experiments, concerning basically stem and cancer cells proliferation and differentiation [34; 41; 44], along with some interesting research on colloidal chemistry, protein crystallisation and drug delivery has been performed [45]. Nevertheless, experimentation done on the ISS has some substantial limitations. The lack of an experiment control, long waiting time, IP ownership issues and relatively high costs determines the development of novel technical means for astrobiological investigation, such as microgravity simulators (e.g., Rotary Wall Vessel--RWV, Random Positioning Machine--RPM) and CubeSat-type nanosatellites. Ground-based facilities are important first approaches to define baselines and enable thorough testing of the biological system to address gravity-related issues prior to space experiments. CubeSats in turn may provide space-based tests in a way that is fully controlled by the user.  
CubeSat-type nanosatellites [46] have been used for space exploration for circa 10 years. Technically, the primary application of these miniaturised instruments is Earth observation and telecommunication, however, a new trend of their utility in the field of biomedicine has already arisen. As one of the basic features that characterises CubeSats is their limited space for experimentation, covering typically 1U-3U (1U = 10 cm\({}^{3}\)). However, these and other requirements of nanosatellite systems (low power, low weight, high-level integrity, short response time, automation, etc.) can be perfectly matched by microfluidic platforms which have the capacity to ultimately bring some new functionalities for biomedical laboratory payloads. Remote-controlled, miniaturised instrumentation with on-board results reading and LOCs easily adapted per specific research needs can open the way towards novel, universal solutions applicable for high range biomedical tests in outer space. The only problem that is at present commonly faced by the scientists engaged in this field is the limited access to timely rocket launches, which is highly important in the case of biomedical samples and their potential time-dependent stability. Typically, a 3-month waiting period is required and during this period, the nanosatellite cannot be operated, even in standby mode. Prior to launch, the CubeSats are kept in ambient temperature (17-22 \({}^{\circ}\)C) in the satellite hangar and only the \"late access\" option (additionally paid) provides the opportunity to launch the rocket within circa 24 h after nanosatellite integration. On that basis, biomedical experimentation conducted on a CubeSat board in low-Earth orbit (LEO) requires special protectants and/or specific sample preparation methods. One of the solutions herein may be lyophilisation, which for bacteria, nucleic acids and proteins is a standardised procedure [47], but cells and more specialised structures are still a serious problem [48].  
In this paper, our microfluidic platform has been designed for simulated and space-based microgravity research to study long-term culturing of microscopic fungi--_F. culmorum_. For the purpose of these experiments, a simplified method to obtain powdered fungi has been employed, based on drying the sample in elevated temperature conditions. These and other issues related to the development of the LOC platform are described in detail in the following sections of the article.