Abstract
The Franz diffusion cell (FDC), widely used for measuring drug absorption across the skin, is usually operated manually. However, manual operation is not only labour-intensive and time-consuming, but inevitably introduces human errors and inter-operator variability. The requirement to perform regular sampling around the clock also presents a significant logistical challenge for researchers. Commercial FDC automation solutions are costly and require proprietary/bespoke FDC designs. To overcome these challenges, we have developed Otto as a customisable and affordable, aftermarket FDC automation solution, to be retrofitted to existing FDCs of generic specifications. Otto uses a modified cartesian 3D-printer as a gantry and adds liquid-handling capabilities using 3D-printed components and common, inexpensive laboratory consumables. Liquid samples are collected into standard autosampler vials. Capable of handling 100 samples per run, Otto supports a high throughput and integrates well with downstream analytical equipment, without modifying the FDC or the analytical equipment. Its programming is facilitated by OttoMate, a companion software application with a graphical user interface designed to generate human-readable code for Otto. Here, we describe the design, construction, operation and characterisation of Otto. To our knowledge, this is the first open-source, retrofittable FDC autosampler with such throughput.