Fluorosome^®–trans Principles

Fluorosome^®–trans are small unilamellar lipid vesicles (approx. 200 nm) with water soluble, drug-binding fluorescent polymers encapsulated in their aqueous interior. When drugs bind to these polymers, there is a change in the fluorescence signal. Fluorosomes^®–trans are designed to measure the passive diffusion of drugs through lipid bilayer membranes.

Fluorosome^®–trans: Principles of Operation

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1. Drug is injected into a suspension of Fluorosome^®–trans.
2. Drug molecules diffuse through the Fluorosome’s lipid bilayer membrane and enter the aqueous interior.
3. Drugs bind rapidly to the encapsulated polymer.
4. The fluorescent signal changes in proportion to the concentration of drug in the interior.

Permeability coefficients, P, are calculated from the first order time-dependent change in fluorescence signal resulting from diffusion of drugs into the Fluorosome^®–trans particle. The data are fitted to give a first order rate constant, k, which is used in conjunction with the Fluorosome diameter to calculate the permeability coefficient in cm/sec.  Permeability coefficients obtained for drugs using Fluorosome^®–trans correlate well with human intestinal drug absorption in vivo (see Data).