Background information

Over the last decade, space missions have increased over tenfold, driven by advances in technology that support exploration. However, safety concerns, particularly related to space radiation, pose significant challenges. Space radiation can lead to both immediate adverse effects and long-term chronic conditions in healthy tissues, making it a critical barrier to the expansion of space exploration.

According to the 2020 NASA Technology Taxonomy ,importance of radiation protection was also emphasised in Human Health Life Support and Habitation Systems. Multilayer materials are most commonly used for radiation protection such as polyethylene and aluminum. The thickness of the material shows significant increase the radiation protection, therefore thick radiation protection layer often been used in both space suit and space craft.

Figure 2:  Relative dose reduction in the water detector behind different thicknesses of shielding materials, plotted as a function of thickness (a) and areal density (b) (normalization is to the dose to the detector in the no shielding case).

Every item sent into space must adhere to specifications ,however these materials often fail to fully meet the strict criteria for weight, durability, resilience, and multi-functionality required for space. Thus, the growing demand brings great opportunities in the market which also trigger enormous research interest from many laboratories

Figure 3:  AI-generated illustration of scientists in discussion.

In response to the increasing challenges faced by space exploration, the use of melanin as a radiation shield has garnered attention. Melanin is a natural pigment widely found in organisms, known for its unique ability to absorb electromagnetic radiation and protect against ionizing radiation. This characteristic makes it a prime candidate for use in space, where harmful radiation from solar and cosmic sources poses significant risks.

A key advantage of melanin is its lightweight nature, which addresses the strict weight limitations in space missions. Unlike heavier materials like lead or aluminum, melanin provides effective radiation shielding without generating harmful secondary radiation, making it an ideal candidate for long-term missions such as Mars exploration.

Synthetic biology methods play a crucial role in space exploration due to their reproducibility and ease of product manipulation. Here, we try develop a novel hydrogel system encupsled with genetically modifide microorganisms to counter space radiation by following the criteria for the desired radiation protection material.

Hydrogels, through the regulation of their physical and chemical properties, can maintain stable humidity and environmental conditions, continuously supply nutrients, and create optimal conditions to support bacterial proliferation. These qualities not only foster bacterial growth but also make hydrogels more efficient for long-term bacterial culture experiments, thereby enhancing their overall application in bacterial culture.

Figure 4:  AI-generated illustration of hydrogel.

How to prevent harmful effect from radiation by live organism?

Melanin:

This natural pigment, found in various species including humans, absorbs a broad range of radiation and converts it into harmless heat. For the first time ,NASA sent melanin to out space ,which test the ability of melanin to protect against space radiation and withstand the extreme environment in space. By engineering E. coli to upregulate the hppD gene, melanin production was enhanced in E.coli , boosting its radiation protection capabilities.

Figure 5:  AI-generated cartoon representation of melanin.

Hydrogel:

Hydrogels provide a suitable environment for culturing modified microorganisms, offering nutrients and containment.Two hydrogel has been used in this system with two different cross-link reaction for different purpose. Their high water content (over 90%) also serves as a secondary barrier against ionizing radiation, enhancing overall protection.

Figure 6:  AI-generated illustration of melanin production using hydrogel.

The construction of an algal-bacterial symbiotic system:

We co-cultivate melanin-producing Pseudomonas (Pseudomonas sp. QDLY50 0GRS) with algae (Gloeocapsa) in a hydrogel matrix, utilizing Pseudomonas to supply CO2 and nutrients to the algae, while Gloeocapsa provides O2 to support the bacteria. The melanin produced by Pseudomonas may help protect the algae from radiation. Upon fluorescence exposure, red fluorescence in the hydrogel indicates robust algal growth. Observations show that melanin expression in the algal-bacterial co-culture is more pronounced compared to Pseudomonas cultures alone, suggesting a synergistic relationship in the hydrogel environment.

Figure 7:  AI-generated algal-bacterial symbiotic cultivation system.

reference

Martin, N. et al. (2021) ‘Synthetic algal-bacteria consortia for space-efficient microalgal growth in a simple hydrogel system’, Journal of Applied Phycology, 33(5), pp. 2805–2815. doi:10.1007/s10811-021-02528-7.

Naito, M. et al. (2020) ‘Investigation of shielding material properties for effective space radiation protection’, Life Sciences in Space Research, 26, pp. 69–76. doi:10.1016/j.lssr.2020.05.001.

Song, W. et al. (2023) ‘Melanin: Insights into structure, analysis, and biological activities for future development’, Journal of Materials Chemistry B, 11(32), pp. 7528–7543. doi:10.1039/d3tb01132a.

Tang, T.-C. et al. (2021) ‘Hydrogel-based biocontainment of bacteria for continuous sensing and computation’, Nature Chemical Biology, 17(6), pp. 724–731. doi:10.1038/s41589-021-00779-6.

Vasileiou, T. and Summerer, L. (2021) ‘Correction: A biomimetic approach to shielding from ionizing radiation: The case of melanized fungi’, PLOS ONE, 16(8). doi:10.1371/journal.pone.0257068.

Vuolo, M. et al. (2017) ‘Exploring innovative radiation shielding approaches in space: A material and design study for a wearable radiation protection spacesuit’, Life Sciences in Space Research, 15, pp. 69–78. doi:10.1016/j.lssr.2017.08.003.