1. ^*Department of Chemistry, Rutgers University, Newark College of Arts and Sciences, Newark, New Jersey, USA
2. ^†International Specialty Products, Wayne, New Jersey, USA
3. ^‡Reheis, Berkeley Heights, New Jersey, USA

Correspondence: Richard Mendelsohn, Department of Chemistry, Rutgers University, 73 Warren Street, Newark, New Jersey 07102, USA. Email: mendelso@andromeda.rutgers.edu

Received 10 June 2004; Revised 21 September 2004; Accepted 27 October 2004.

Abstract

The feasibility of monitoring the permeation of chain perdeuterated 1,2-dipalmitoylphosphatidylcholine (DPPC-d₆₂) and 1-palmitoyl-d₃₁, 2-oleoylphosphatidylcholine (P-d₃₁OPC) vesicles into pigskin using infrared (IR) microscopic imaging and confocal Raman microscopy was demonstrated. The former technique permits the examination of the relative concentration of molecular species (e.g., endogenous and exogenous lipids and proteins) over spatial areas, 1 mm, with a spatial resolution of 10–12 m. In contrast, Raman microscopy allows the confocal examination of tissue at depths up to 100 m with a pixel size of about 2–3 m³. Spectral signal/noise, however, is reduced from IR and significantly smaller areas are generally monitored. The permeation of the gel phase DPPC-d₆₂ was limited to 5–15 m, whereas the liquid-crystalline phase P-d₃₁OPC permeated to substantially greater depths (35–100 m), at times ranging up to 24 h after application. The results are generally in accord with literature values. In addition, the state of the P-d₃₁OPC (intact vesicles or molecularly dispersed with skin constituents) was evaluated from the spatial dependence of the deuteriopalmitate chain conformational order. Upon permeation, the chains became more ordered. The advantages and limitations of these imaging technologies are discussed.