Extraction of polar and nonpolar biomarkers from the martian soil using aqueous surfactant solutions

Abstract

The Life Marker Chip intends to use an aqueous surfactant solution to extract both polar AND nonpolar biomarkers from the martian soil for transport to an antibody-based detection system. Currently, a solution of 1.5 g l-1 polysorbate 80 in 20:80 (vol:vol) methanol:water is being considered and appears to be suitable. However, should this solution be shown to be unsuitable for the LMC or the martian environment, it will be necessary to use a different surfactant. Here, we have investigated the ability of a range of other surfactant solutions to extract a suite of eight standards spiked on the surfaces of the martian soil simulant JSC Mars-1 and tested the compatibility of the best two surfactants with a representative antibody assay for the detection of pyrene. The results show that using 20:80 (vol:vol) methanol:water as the solvent leads to greater recoveries of standards than using water alone. The poloxamer surfactants Pluronic® F-68 and F-108 are not effective at extracting the standards from JSC Mars-1 at any of the concentrations tested here. The fluorosurfactant Zonyl® FS- 300 is able to extract the standards, but not as efficiently as polysorbate 80 solutions. Most successful of the alternative surfactants was the siloxane-based surfactant poly[dimethylsiloxane-co-[3-(2-(2- hydroxyethoxy)ethoxy)propyl]methylsiloxane] (PDMSHEPMS) which is able to extract the standards from JSC Mars-1 about as efficiently as polysorbate 80 solutions. Enhanced recovery of the standards using polysorbate 80 solutions can be achieved by increasing the concentration of polysorbate 80, from 1.5 g l-1 to 10 g l-1, leading to an increase in the recovery of standards of about 50%; a similar increase in effectiveness is also apparent for PDMSHEPMS. Polysorbate 80 at concentrations of 1.5 g l-1 and 10 g l-1 and Zonyl® FS-300 and PDMSHEPMS (both at a concentration of 10 g l-1) are also compatible with the representative pyrene antibody ass