Week 8: Calibration (continued) and preliminary testing

This week, we focused on fabricating calcium alginate gel matrices containing bromelain.  Bromelain was added to distilled water and stirred before sodium alginate was mixed into the solution.  Sodium alginate concentrations of 1 wt% and 2 wt% were used.  The bromelain alginate solution was then cast into a 0.5 wt% CaCl₂ solution using a pipette.  Normally, droplets of the bromelain alginate solution fell from the pipette tip once the droplet reached sufficient mass (0.04 mg) that the force of gravity overcame the droplets’ cohesive force with the solution inside the pipette and the adhesive force with the pipette tip.  Early attempts to cast the 2 wt% alginate solution, resulted in cylindrical alginate structures since the viscosity of the solution resulted in long streams rather than discrete droplets.  This was avoided by manually separating the alginate solution from the pipette tip once it reached a desirable size.  Once the alginate bromelain solution was cast in the 0.5 wt% CaCl₂ bath, the alginate was allowed 30 minutes to form.  A 2 wt% alginate rod is shown in Figure 1.

Figure 1. Bromelain/alginate "rod"

The test setup for testing bromelain release form the alginate drug is shown in Figure 2.  It consists of a hot plate heating a water bath to 37°C.  The test bath inside the thermal bath has a volume of 1L to simulate the size of human stomach. Initially, a low pH environment was to be created using a 0.001M HCl solution.  However, due to safety concerns, this was abandoned.  During the test, the bath was stirred every 30 minutes to evenly mix the released bromelain, and care was taken not to break up the alginate beads via mechanical irritation.  5mL samples were drawn from the center of the bottle every 30 minutes and stores for spectroscopic analysis.  The overall duration of the test was 6 hours.  Consideration was given to simulate the natural compressive forces of the stomach and foods from meals, but due to budget and time constraints, these were not realized in the present work.  

Figure 2. Test setup