Table 1.

The most commonly used in vitro diffusion investigation devices.

Name	Application	Direction of Diffusion	Volume and Measurement Conditions
μFLUX™ diffusion cell—in situ UV monitoring optical system (Pion Inc., Billerica, Massachusetts, United States) [17]	Diffusion measurement with artificial membrane	Horizontal	Both phases: 10–13 mL Real-time analysis is possible
Navicyte Vertical Diffusion Chamber System (Harvard Apparatus, Holliston, Massachusetts, United States)	Cells, ex vivo tissue investigation Intestinal and nasal permeability	Vertical	Both phases: variable Real-time analysis is possible
Navicyte Horizontal Diffusion Chamber System (Harvard Apparatus, Holliston, Massachusetts, United States) [18,19]	Tissues contacting with air (nasal, pulmonary, dermal) permeability	Horizontal	Both phases: variable Real-time measurement is possible
In-Line Cell (PermeGear Inc., Hellertown, Pennsylvania, United States) [20,21]	Permeability of transdermal and buccal formulations	Vertical	Acceptor phase: variable Donor phase: 100 mL Real-time analysis is possible
Franz vertical diffusion cell (Hanson Research, Chatsworth, California, USA) [16,22]	Permeability of transdermal formulations	Vertical	Donor phase: 300 µL Acceptor phase: 7 mL No real-time analysis
Side-Bi-Side™ horizontal diffusion cell (PermeGear Inc., Hellertown, Pennsylvania, United States) [23,24]	Blood–brain barrier investigations Permeability of nasal formulations	Horizontal	Both phases: 3 mL Real-time analysis is possible