Case study: printing powders with Sticky Web technology

Nov 01, 2009
Volume 21, Issue 11

The brief:

GlaxoSmithKline (GSK) appointed 42 Technology (42T) to evaluate existing powder dispensing approaches that could be scaled for highspeed manufacturing.

42T suggested an innovative precision powder dispensing technology, now known as Sticky Web, which can accurately 'print' powdered APIs onto edible or inert adhesive surfaces to create a novel dosage form.

GSK has now granted 42T worldwide pharmaceutical rights to the technology.

Henrik Weis/Getty Images
Powder handling is technically challenging at the best of times, but accurately filling capsules with milligram quantities of potent APIs at the manufacturing speeds and outputs required for a blockbuster product adds another layer of complexity. Manufacturers usually overcome this hurdle by bulking out actives with excipients and using mixtures for tablet pressing or capsule filling; however, there is considerable commercial interest in developing highspeed manufacturing technologies that can dispense pure active powders. A technology that can accomplish this is Sticky Web.

According to Keith Smith, Manager of GSK's strategic technologies department, the core technology was first proposed as a result of some "shrewd research" by 42T. "GSK first appointed 42T to conduct an independent strategic technology review and to evaluate existing, credible powder dispensing approaches that could potentially be scaled for high-speed manufacturing. We already knew of some commercial systems claiming speeds of up to 15000 doses/h, but these typically involved check weighing or volumetric techniques, which are often unsuitable for some pure APIs that require careful handling," said Smith. "The consultancy team responded not only with a detailed review of the options, but with some great new ideas of their own — including the approach we now call Sticky Web."

Henrik Weis/Getty Images
Sticky Web is a scalable technology capable of accurately dispensing 0.1–100 mg of powder, with a variety of particle size distributions, onto edible or inert adhesive webs or surfaces. Accuracies are typically greater than 4% and the technology can deliver commercial manufacturing speeds of up to 60000 doses/h.

Developing the technology

Sticky Web takes its name from a simple discovery by one of 42T's engineers, based on the following theory: when a piece of adhesive parcel tape is dipped into powder and the excess shaken off, the quantity left adhering is directly proportional to the surface area of the tape. The exact quantity depends on the combined properties of the specific adhesive and powder, but even the very first tests conducted by 42T showed consistent coverage rates of approximately 1.5 mg/cm2 with accuracies greater than ±10%.

The author says...
These results led GSK and 42T to quickly establish a joint development team to create a stronger technology platform and improve the dosing accuracy — in some cases to within ±2.5%. The team studied a range of APIs with widely varying physical properties and further tested the applicability of the technology.

The development programme progressed quickly to deliver the core approach, as well as several adhesives and designs for a prototype production machine. A number of key patent applications were also secured.

Dispensing the powder

The powder dispensing head and process are critical to the Sticky Web approach. The web, which is preprinted with adhesive further up the production line, passes around a drum where powder from a vibrating hopper is applied through drum apertures or masks to the sticky areas; any excess is tapped off using a vibrating paddle. The technique delivers uniform coverage for freeflowing powders, as well as powders that have dry clumping behaviours. It is also gentle enough for powders that require very careful handling to prevent degradation or any loss of activity.

lorem ipsum