Detection of organic agent exposure using L-[alpha]-dipalmitoleoylphosphatidylcholine phospholipid film biosensor

Inhalation exposure to aerosolized organic agents results in significant damage to normal pulmonary function in mammalian lungs. Yet, only modest study has been devoted to developing potential bioanalytical devices to detect these harmful agents. The goals of this study were to investigate the utility of a visible light spectrophotometer (400-850 nm) for detecting and measuring optical thickness changes in 900-1200 Å thick L-α-dipalmitoleoylphosphatidylcholine (DPPC) phospholipid film induced by hydrocarbon and organic agent exposure. In this study, DPPC films were exposed to N2 flows saturated with the following test agents: JP-8 jet fuel, semiconductor grade acetone, 0.85% NaCl saline, and ultrapure de-ionized water. Exposure durations were 5-minutes, followed by 2-minute 100% pure N2 flow recovery periods. A total of six trials were preformed for each test agent. The DPPC film's response, defined as the optical Δ-thickness, was the difference between the DPPC film's mean exposure thickness and the film's mean recovery thickness. DPPC film responded to all exposure agents. Saline solution produced a mean Δ-thickness of 190.4 (19.0) Å (N=6). Semi-conductor grade acetone produced a mean Δ-thickness of 172.9 (38.4) Å (N=6). JP-8 jet fuel produced an mean Δ-thickness of 68.8 (17.5) Å (N=6). Ultra-pure deionized water produced a mean Δ-thickness of 186.8 (10.7) Å (N=6). Additionally, simultaneous exposure to 0.85% saline and JP-8 jet fuel saturated N2 flows, which followed a 2.5-minute 0.85% saline exposure, produced an Δ-thickness of 110.8 (3.6) Å (N=10). This study demonstrated that the DPPC film response to test agent exposure, in the form of an optical thickness increase, was measurable using the visible light spectrophotometer designed for thin-film measurement. This method was both robust and repeatable for observing these films' physical alterations. This study elucidated the capability of visible light spectroscopy for measuring a dynamic surfactant film's thickness. Despite the DPPC film's wide-ranging response to such chemically different molecules as JP-8 hydrocarbons and ultra-pure deionized water, its distinctive thickness response to JP-8 in a saline-saturated model suggests that a DPPC-based apparatus may have an eventual application as a biosensor. This study is supported by AFOSR grant F9620-00-1-0217 and the UA Undergraduate Biology Research Project.