Abstract
Laboratory in vitro permeation processes require the use of modified Franz type diffusion cells which are conventionally fabricated from glass. Fragility and high cost are frequently associated with this type of laboratory apparatus. The purpose of our present research was to develop a simple, economical and versatile approach to manufacture Franz type cells using additive manufacturing (AM). Graphical Franz diffusion cell designs were reproduced with a stereolithography (SLA) 3D printer and assessed over a minimum period of 24 h. The surface morphology of AM printouts was analysed before and after compatibility studies using scanning electron microscopy (SEM). Comparative permeation studies in both glass and AM Franz type diffusion cells were conducted using a caffeine solution (1.5 mg mL-1 ), applied to a model silicone membrane. Testing of the 3D printed scaffolds confirmed similar recovery of the permeant when compared to glass cells: 1.49 ± 0.01 and 1.50 ± 0.01 mg mL-1 , respectively, after 72 h. No significant differences were visible from the SEM micrographs demonstrating consistent, smooth and non-porous surfaces of the AM Franz cells' core structure. Permeation studies using transparent 3D printed constructs resulted in 12.85 ± 0.53 µg cm-2 caffeine recovery in the receptor solution after 180 min with comparable permeant recovery, 11.49 ± 1.04 µg cm-2 , for the glass homologues. AM constructs can be considered as viable alternatives to the use of conventional glass apparatus offering a simple, reproducible and cost-effective method of replicating specialised laboratory glassware. A wider range of permeants will be investigated in future studies with these novel 3D printed Franz diffusion cells.
Highlights
The additive manufactured (AM) cells were examined for leaks over a minimum of 24 h and the printouts were considered successful if no aqueous media was present on the outer wall after this period
Caffeine compatibility studies with AM Franz type diffusion cells were conducted by filling the diffusion cell receptor compartment with a 1.5 mg mL-1 CAF solution prepared in PBS
The AM Franz cell was sealed with Parafilm® (Bemis NA, Neenah, USA) and placed in a JB Nova thermostatically controlled water bath (Grant, London, UK) set to 32 ± 1 °C equipped with a HP 15 stirring system (Variomag, Florida, USA). 200 μL aliquots were taken from the Franz cell receptor compartment at different timepoints, 0, 24, 48 and 72 h and replaced with the same volume of fresh CAF solution
Summary
Post-curing of AM constructs was achieved by exposing the 3D printed Franz type cell compartments to UV light (405 nm) at 60 °C for 15 min using Form Cure (Formlabs, Massachusetts, USA) [8]. All transparent 3D printed Franz cells were tested for leaks by filling both compartments with a PBS (pH 7.3 ± 0.1) solution.
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