From pharmaceuticals to food and agriculture to cosmetics, controlled release systems are currently used in many fields to facilitate a slow, predictable delivery of specific ingredients over time. The advantages are many including tailored release rates, site-specific deliveries and less frequent applications. Generally a complex system of layers, a common manufacturing strategy for controlling a release profile is to encapsulate the active ingredient at the core with a coating of an insoluble substance like a polymer or acrylic or to sandwich it between an inert core and several layers. In either method, it is crucial to the system’s overall performance and stability that the coatings be uniformly applied.
Leading the way in measuring coating and layer uniformity is a novel technique called Raman chemical imaging (RCI). A hyperspectral imaging method based on Raman spectroscopy, RCI determines the chemical identity of individual components of a sample based on partial Raman spectra that correlates to a high-quality digital image. Images are collected as a function of wavelength based on the material’s spectral response, enabling each pixel within the image to have a fully resolved spectrum associated with it.
Spectral and spatial information from specific spectral ranges are used to identify, place and size particles in simple and complex systems. This allows for the ingredient-specific measurement of individual coating layers which can supply valuable feedback about coating processes and help establish coating consistency in laboratory and manufacturing environments.
Although prevalent in several industries, controlled release designs are commonly applied in oral pharmaceutical formulations due to their ability to extend a product’s life and offer more convenient treatment options to patients. In a study conducted by our scientists, generic controlled release beads were examined from an out-of-specification batch rejected by a company’s quality assurance department. Using RCI, the inner coating thickness was determined to vary from 32.3 to 56.5 μm, and the outer coating ranged from 3.5 to 18.1 μm. Given its very thin to absent coating, the issue at hand was associated with the bead’s outer layer, and its origin was traced back to a change in spray-drying conditions.
In addition to controlled release formulations, RCI has been used to identify contaminants in food products. In 2007, toxic melamine scrap was found in flour and animal feed imported from China, and RCI identified the melamine in the wheat flour due to its distinctive spectral response. The U.S. Department of Agriculture (USDA) conducted a study using hyperspectral imaging to distinguish Campylobacter, a foodborne pathogen that causes human illness, from other microorganisms.
No matter the application, the benefits of RCI and other novel technologies are clear — they keep progressing science forward … with each new development providing an avenue to do things that weren’t possible before.