Wan W. Amani Wan Salim
Purdue University, USA
Wan W. Amani Wan Salim received her B.Sc. (2001) and M.Sc. (2003) degrees in Electrical Engineering from the University of Minnesota and her Ph.D. (2009) in Biomedical Engineering from Purdue University. In 2009, she joined the School of Engineering Education at Purdue University as a Postdoctoral Researcher and was appointed as a Faculty Fellow. In 2011, she joined the Department of Agricultural and Biological Engineering, also at Purdue University, as a Postdoctoral Researcher in the field of micro/nanofabrication and biosensing. Her current research interests are the design and development of micro-electro-chemical sensors for applications in astrobiology, biomedicine, and agriculture. She is currently the Principal Investigator for a NASA-funded nanosatellite mission called SporeSat.
Ceratopteris richardii fern spores are an ideal model system for studying single cell graviresponse due the ability to synchronize the development of the spores during culture. Previous work with the self referencing probe and cellelectrophysiology lab on achip (CELC) technologies documented an asymmetric and directional transcellular Ca2+ concentration that is influenced by gravity. To further investigate the threshold of Ca2+ channel activation that generates the Ca2+ polarity in C. richardii spores, we have adapted the CELC device into a disk version called the bioCD. When the bioCD rotates in microgravity, different gravity thresholds can be experienced by individual fern spores. The fusedsilica bioCD consists of thirty two wells; each well houses a single spore. A pair of allsolidstate ionselective electrodes in each well provides dual electrode differential coupling (DEDC) measurement of Ca2+ concentration at both sides of the spore. Our preliminary 1g experiments reveal a DEDC signal of 0.4 V when the spore is repeatedly oriented at 180° to the gravity vector during the peak germination period which occurs at 69 hours from initiation of germination. This translates to a 22fold change in calcium concentration between the two sides of the spores. However, when rotations were conducted after the germination period ended, no change in voltage was observed. The results imply that polarity development in fern spores is directed by gravity and that there is a fixed period of gravity responsiveness from the fern spore. The bio CD technology is intended for the NASA SporeSat mission, an autonomous free flying 3U spacecraft unit that utilizes flight proven technologies of previous nanosatellite missions.