Comparative Study of Four Membranes for Evaluation of New Insect/Arthropod Repellents Using Aedes aegypti

Repellent use is one of the most effective personal protection measures in reducing bites of blood-sucking insects/ arthropods and preventing vectorborne disease transmission. Tmditionally. discovery of new repellents involves initial screening of thousands of candidates using various methods with very few successes. However. despite the obvious desirability of finding an effective mosquito repellent, no ideal repellent has been identified yet [Gupta 1994]. The process is even mor~ ~q.~_gli,~~ted because of the characteristics required in an ideal insect repellen~~-~~W:~i¥ffective against broad spectrum of species, long duration of prot~c#o~ •. rio toxicitY or side effects, resistant to· abrasion, greaseless and odoi:Ies's. In :~~diti_f?ri, _lack (£understanding of the_ mode .. of action of repell~ts brings (urther' complication to the process. Thus, a search for an ideal insect/ arthropod repellent continues. Presently, the U.S. military's most effective personal protection system [Armed Forces Pest Management Board 1996; McCabe et a/1964] utilizes a controlled-release formulation ofDEET (N,.N -diethyl-1,3-toluamide) as a topical repellent, which defends against several types of biting arthropods [Gupta 1994]. However, DEET has many short comings. As a repellent for .. human use, DEET is not equally effective against all insects and arthropod disease vectors. Moreover, it has several disagreeable cosmetic effects such as unpleasant odor and an oily feel. DEET's deep skin penetration can cause drug-drug interactions that could lead to potential toxicity in children and adults when used in high concentrations [Briassoulis, eta/2001]. DEETis a known plasticizer that reacts with certain plastics and synthetic rubber [Gupta 1994; Skinner and Johnson 1980; Watanabe eta/1993]. Finally, a growing segment of the consumer population is shying away from synthetic chemicals in favor of botanical products. W/e initiated a research effort to explore the feasibility of understanding the molecular mechanism of known repellents '\Vith the objective to stream line and expedite design and discovery of insect repellents using state-of-the-art technologies. We gained valuable insights on the molecular mechanism of repellents [Bhattacharjee et tt/1999; Bhattacharjee, Gupta and Karle 2000] and our efforts resulted in the development of a three dimensional (3D) pharmacophore to predict repellent potency of new compounds using in silica techniques [Bhattacharjce et a/2005]. However, during rapid screening of new potential repellent candidates in an in 1.ritro test system [Rutledge et a/1978] in the laboratory, we yet faced another challenge. The supplier of Baudruche membrane used in our i111•itro test system for years decided to retire from the market and had no plans to continuously provide the membranes. Thus, in an effort to find an alternative iu t•itro membrane test system, our initial literature search narrowed the available choices in a relatively short period of time to four membranes. They were: Baud ruche, 1-lemotek, Sausage, and a Siliconebased membrane.