Pack to the future

New packaging materials are adding value to pharmaceutical products while meeting the challenge of increasing legislation

Packaging for pharmaceutical products can be either internal (integral) or external. External packaging is that which surrounds the pharmaceutical product, such as a blisterpack, while integral packaging is that which is part of the actual drug delivery, for example, tablet coating. Within these two categories packaging can be described as either active or passive. Active materials respond to external factors (e.g. pH triggers for drug release) while passive materials just have a predefined inherent functionality (e.g. binders for active components or a material approved for food contact).

One of the key challenges is to develop new materials that will meet industry's need for increased functionality (added value) and decreasing production costs (downgauging, more efficient processes), while at the same time rising to the challenge of increasing environmental and health legislation for packaging and products.

built-in functionality

At the Polymer Centre, University of Sheffield, one of the key activities is the bespoke design and synthesis of

tailor-made polymer structures with specific functionality built in. These developments are commercialised through FaraPack Polymers Ltd, a joint venture with Faraday Packaging Partnership.

In relation to external packaging, while talking about new 'high technologies' it must not be forgotten that there are many gains to be had from the continuous improvement (and new combinations) of more traditional properties such as strength, durability, clarity, moisture resistance, weight, processability, appearance and design.

For example, multilayer films allow many different properties to be incorporated together, such as an internal layer that is approved for food contact and an external layer that is optimised for printing or moisture resistance.

The technology becoming available means that external packaging can be much more than a passive plastic container. Active polymers applied as thin films can be a cost-effective method for adding functionality to the packaging. Two examples are:

• polymers that can be used as sensors for biological, chemical or environmental effects and thus help to predict shelf life or warn of product contamination or degradation.

• polymers with selective permeability, for example, that let water in and carbon dioxide out to ensure the survival of the required 'live' micro-organisms.

Looking to the future, cheap and flexible carbon-based electronics will allow the functionality of electronic circuits and displays to be incorporated into packaging, whether this is for promotional purposes or security and tracking.

Integral and passive materials aid the handling and delivery of the active ingredient. For example, they may be inorganic filler materials that are used to make the tablet a sensible size. However, even these are not immune from enhancement with polymers. The Polymer Centre at Sheffield has been looking at methods to attach polymer chains to the surface of inorganic particles to modify their surface properties. This can be designed to give enhanced interaction with other components in the tablet, such as other particles, binders or colorants, or could be adapted to attach active compounds directly.

The incorporation of chemicals and drugs into polymeric materials can allow the transport and delivery of substances through hostile environments to specific sites. Several functional vessels for drug delivery have been explored at the Polymer Centre: hydrogels, dendrimers, hyper-branched polymers and vesicles (microscale polymer bags).

Additional functionality can then be incorporated by using responsive polymers which can be triggered by a change in pH, pressure, temperature or light to release the active components that they carry.

Polymers are extremely adaptable and present many properties that could be applied to both the integral and external packaging of pharmaceutical products. The Polymer Centre is working with companies both to get current developed functionality into products as well as looking to develop new functionality that could differentiate products in the future.