PALO ALTO, Calif.—Although a variety of HTP assays (e.g., PAMPA, Caco-2) have been developed to determine the permeability of drug candidates, the throughput of techniques used to monitor compound permeability (e.g., LC-MS) has remained comparatively low. Recently, however, Hugh Daniels of Nanosys adapted Bruker Daltonics' nano-assisted laser desorption/ionization (NALDI) platform to work with Caco-2 assays, removing the sample preparation step that typically slows the detection process.
As he describes in an application note, Daniels added two doses of five well characterized drugs to the apical chamber of a multiwell Caco-2 plate and following incubation, spotted samples from the basolateral chamber onto multiple NALDI plates. The drugs were then allowed to adsorb to the hydrophobic surface of the plates for different time intervals before being washed, dried, and analyzed by MALDI-TOF MS.
Daniels noted that the permeability values he identified in the NALDI test were comparable to literature values. He also noted that compound adsorption to the plate hit a plateau after 20 minutes incubation, suggesting that sample cross-contamination during washing should not be a factor after this point.