Nanoscale Measurements of Water Loss during Desiccation of Biological Cell Suspensions
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Nanoscale Measurements of Water Loss during Desiccation of Biological Cell Suspensions S. Mittal and R.V. Devireddy Bioengineering Laboratory, Department of Mechanical Engineering, Louisiana State University, Baton Rouge, LA 70803, U.S.A.
ABSTRACT There is an urgent need to protect and conserve the endangered species of the world. Desiccation, or the phenomenon of anhydrobiosis, offers the attractive possibility of low cost, long term storage of reproductive tissues and cells from endangered species at ambient temperatures. Biophysical optimization of anhydrobiosis procedures requires dynamic and accurate quantification of the rate of moisture loss during a prescribed desiccation protocol. Engineered microstructures can serve as a multifunctional and highly sensitive method to measure the rate of moisture loss. This study presents a novel ultrasound based (resonant) mass sensor to quantify water loss during a drying process by measuring the corresponding shift in the resonant frequency of a micromachined vibrating structure. To model the proposed ultrasound based sensor, we performed a static (stress) and dynamic (frequency change with change in imposed mass) analysis. The results suggest that by tailoring the dimension of the vibrating element appropriate sensitivity can be achieved.
INTRODUCTION The conventional method of breeding and maintaining endangered species in captivity is not only very difficult but also expensive, limiting the genetic diversity of an endangered species. The current methodology for long-term storage protocols is using low temperatures or cryopreservation. Cryopreservation protocols are fairly complex, they require high concentrations of toxic cryoprotectants and costly freezing equipment, and suffer from the inflexibility of storage associated with liquid nitrogen. Preservation by desiccation is an alternative that attempts to reproduce a naturally occurring preservative technique, namely, the phenomenon of anhydrobiosis [1]. In anhydrobiosis, organisms survive extremes of dehydration by imbibing large intracellular concentrations of sugars. Previous studies have demonstrated that intracellular loading of minimally toxic sugars, such as trehalose or sucrose, have a positive effect on the preservation of biological material under conditions of low moisture. 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. The efforts of the current study are aimed to develop an ultrasound based resonant sensor to dynamically quantify the water loss in a cell suspension during a prescribed drying (or desiccation) process. The ultimate aim is to improve desiccation protocols for the long-term preservation of reproductive cells from endangered species and other clinically relevant biological tissues and cells. Currently available methods to measure the loss of moisture during a prescribed desiccation protocol include the use of a gravimetric analysis using an analytical balance [2]. In this metho
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