Nanoscale Measurements of Water Loss During Desiccation of Biological Cell Suspensions: There is an urgent need to protect and conserve the endangered species of the world. Traditional programs of breeding and maintaining endangered species in captivity are not only very difficult but are also very expensive. Thus, limiting the genetic diversity of an endangered species. Desiccation, or the phenomenon of anhydrobiosis, offers the attractive possibility of storage at ambient temperature simplifying the logistics of storage and transportation thereby significantly reducing the cost. Cell stasis is achieved in nature by anhydrobiotic organisms through desiccation at ambient temperatures, and the pharmaceutical industry has made significant strides in storing proteinaceous drugs, membranes, and viral particles in dry state using various small sugar molecules as stabilizers. Although some success have been demonstrated in desiccation preservation of mammalian cells in the presence of sugars, the process has not been optimized due to a lack in understanding of the fundamental mechanism(s) by which sugars protect the cells. Current techniques of desiccation use a convective drying stage, an approach that has advantages both in terms of cost as well as ease of use operation. To dynamically quantify the rate of moisture loss during a prescribed desiccation protocol, we have modeled and characterized a novel micromembrane ultrasound (resonant) sensor. To model the sensor, we performed a static (stress) and dynamic (frequency change with change in imposed mass) analysis of the membrane. Rectangular membranes were selected for their structural/directional rigidity. Static analysis of the membrane was used to relate the stress induced in the membrane to the weight of the cell suspension. To prevent failure (rupture) of the membrane during the initial loading process, analytical and finite element techniques were utilized to determine the minimum dimensions of the membrane for a predetermined membrane material (silicon) and the loading weight (i.e. volume of the cell suspension). Dynamic analysis encompassed effects of the mechanical vibration i.e. the ultrasound vibrations, on the membrane with respect to time and change in loaded mass (i.e. loss of moisture content). Although the characterized device was found to have a sensitivity of ~1 nanogram/millisecond, limitations in fabrication techniques and measurement/frequency analysis suggest that the fabricated device will only be able measure weigh loss in 10’s of nanograms. Aim is to fabricate the sensor using microfabrication techniques, and to quantify the rate of water (moisture) loss during the drying protocol in the presence and absence of sugars. The results will be used to develop and perfect a computational model of water loss during drying of cells loaded with sugars.  It is expected that these studies will form the basis for developing a desiccation protocol, for an easy and flexible solution for banking and storage of sperm cells from endangered species.

Publications & Presentations:

Journal Papers:

 "Dessication Tolerance of Adult Stem Cells in the Presence of Trehalose and Glycerol", S. Mittal and R.V. Devireddy.The Open Biotechnology Journal;  2:211-218 (2008)

Refereed Conference Papers: