Microencapsulation is a procedure that can store singular particles within a shell that is enclosed or coated with an unbroken film of material which provides protection from the external environment.
Besides the additional protection, the encapsulated particles take advantage of better stability, longer shelf life, and the potential for controlled release. A broad range of applications appropriate for employing this process include pharmaceuticals, fragrances, cosmetics, food and beverage, textiles, and more.
Flow Imaging Microscopy using the FlowCam offers the capacity to acquire rare insight into the microencapsulation process via the dynamic tracking of capsule formation over time, while monitoring the effects of temperature, concentration pH, and other variables that can influence the process.
One method frequently used, known as complex coacervation, can greatly benefit from FlowCam monitoring. Throughout this process microcapsules form by combining two hydrocolloids to create a shell around droplets of an active ingredient (typically in an emulsion).
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Utilizing the FlowCam, observations of the coacervate formation were conducted in a test vat over a specified time period while the sample cooled under constant agitation. The sample was then pumped continuously into the FlowCam straight from the reaction vessel. Throughout this process, the view of the FlowCam’s flow cell was manually observed, while every 15-30 minutes collections of data runs were carried out (or if any considerable change was witnessed). The size range anticipated for the coacervates was between 80 µm and 140 µm in diameter. Therefore, the FlowCam was configured with a 4x objective (roughly 50x total magnification) and a 300 µm depth flow cell. Measurements were also taken during each run to correlate temperature and pH data to the particle images.
Figure 1. Coacervate Images T=t0 + 9 minutes Active ingredients are the dark circles. Image Credit: Yokogawa Fluid Imaging Technologies, Inc
Figure 2. Coacervate Images T=t0 + 30 minutes Gelatin casing begins to form around active ingredients. Image Credit: Yokogawa Fluid Imaging Technologies, Inc
Figures 1 through 4 exhibit the particle images acquired using the FlowCam throughout various stages of the experiment. From a visual examination alone, it appears that the run completed at t0 + 39 minutes demonstrates the cleanest coacervate formation. After this time, the particles began to group and agglomerate as an increasing amount of gelatin attached itself to the capsules.
Figure 3. Coacervate Images T=t0 + 39 minutes Coacervates are fully formed. Image Credit: Yokogawa Fluid Imaging Technologies, Inc
Figure 4. Coacervate Images T=t0 + 58 minutes Coacervates still visible, but agglomeration beginning to occur. Image Credit: Yokogawa Fluid Imaging Technologies, Inc
VisualSpreadsheet® software was utilized in order to confirm the qualitative observations. A statistical pattern recognition was performed on each run to quantify the exact number of coacervates. To achieve this, an image library was produced to exhibit all coacervate particles (with distinct particle properties) of different sizes and orientations. This library is displayed in Figure 5. Illustrated in the table in Figure 6, the results of the statistical pattern recognition operation can be seen. These results supply quantitative affirmation of the earlier subjective results: specifically, that the largest concentration of clean coacervates were formed at t0 + 39 minutes. Once this time point had passed, the gelatin started to attach itself to the capsule walls, leading to agglomeration and eventually to the total decay of the coacervates.
Figure 5. Coacervate images stored in library for statistical pattern recognition. Image Credit: Yokogawa Fluid Imaging Technologies, Inc
Figure 6. Table showing matching statistics after statistical pattern recogniation is run against coacervate library. Image Credit: Yokogawa Fluid Imaging Technologies, Inc
Conclusions
To summarize, the FlowCam produces remarkable insight concerning the coacervate formation process and can be an essential tool for microencapsulation R&D and QC applications.
This information has been sourced, reviewed and adapted from materials provided by Yokogawa Fluid Imaging Technologies, Inc.
For more information on this source, please visit fluidimaging.com.