Locking in extractables
Eliminating extractables with high technology coatings

Eyeglasses that resist scratches, surfaces that are easier to clean, medi-cations with longer shelf lives: high-technology coating techniques are creating new opportunities in a number of areas, including pharmaceutical packaging. Schott’s Type I plus is a tough silica coating that virtually eliminates extractables.

They’re known as “extractables”, those invisible elements that, over time, can leach from pharmaceutical packaging to the point of degrading the medicine within. “Even the highest-quality borosilicate glass is subject to this effect,” says Dr. Robert Hormes, Manager Competence Center Coating for Schott’s Pharmaceutical Packaging business segment. “Plastics are also no exception. The approach that has been adopted by us to improve the resistance of packaging materials to chemicals is based on an extremely thin, yet highly effective barrier layer,” Hormes adds.
To counter the problem, Schott forma vitrum has developed Schott Type I plus, which adds an ultra-thin, highly flexible barrier coating of pure silica to the inside surface of pharmaceutical containers. Hormes explained the advantages of Schott Type I plus at interpack 2005 in Duesseldorf.
The process used to create Schott Type I plus is known as plasma impulse chemical vapor deposition (PICVD).

This deposits a quartz-like surface of pure silica that bonds chemically to the interior of the container, creating an ultra-thin, non-porous lining with no significant dimensional changes. Applied in a validated process, the coating helps to overcome adsorption of radioactive diagnostics and proteins as well as improving the inertness and stability of the packaging material. The method has been scientifically verified to be an effective diffusion barrier, reducing the leaching of elements such as sodium, calcium, boron, silicon and aluminum, and suppressing metallic ions to below their detection limits. The product to be coated is placed in a vacuum chamber and a mixture of oxygen and a silicon-containing precursor gas is introduced. A plasma is then created by adding microwave energy. This decomposes the gas and causes a layer of silicon dioxide to be deposited on the surface. The microwave energy is added in pulses, which helps to create a uniform and non-porous layer of silica. By changing the chemical composition of the gas mixture, layers can also be created with different properties.
At Schott’s new production facility in Müllheim/Germany (see box) up to 16 vials can be coated in a single cycle that lasts approximately one minute. During the pulsed plasma method, more than 400 layers of silicon dioxide molecules are applied to the inside surface of the container. In total, the coating layer is approximately 100 to 200 nanometers thick. The Type I plus vials are packaged for processing by the pharmaceutical industry as if they were made of normal glass. This applies to both the washing process and de-pyrogenization inside the heating tunnel at temperatures of up to 280°C. The vials can then be filled aseptically inside a clean room.
Advantage in lyophilization or freeze-drying
Developed by Schott in the 1980s, the plasma impulse method has made a real difference in the area of pharmaceutical packaging. Schott Fiolax glass that is coated on the inside offers much better barrier characteristics, said Hormes. “Thanks to the silicon dioxide layer, hardly any metallic ions are able to diffuse. This is extremely important in ensuring the stability of the biological molecules contained in the solution. This also results in a more homogeneous surface that is an advantage in lyophilization or freeze-drying, which is commonly used to achieve long-term stability of biomolecules.”
Even no problems with high pH values
The plasma layer also prevents protein adsorption; therefore, fluid formulations are possible. Type I plus is also suited for use with non-buffered solutions, such as “water for injection purposes”, due to the fact that it retains its pH value for a long period of time. Even solutions with high pH values that would normally have a corrosive effect on the glass can be stored longer in Type I plus vials.
The flexibility of the PICVD process enables it to be adapted to different geometries and materials, including glass and plastics like PET and COC (cycloolefine copolymer). Coatings can be customized with layer properties adapted to the active ingredients. “Schott Type I plus pharmaceutical packaging with PICVD coating keeps the active ingredient more stable, so there is potential to reduce dosage—an added financial benefit,” said Hormes.
Type I plus is made using only high-grade glass tubing manufactured by Schott’s tubing companies. Hormes: “The primary considerations of the Schott pharmaceutical packaging group are care, cleanliness and strict observance of customers’ requirements. Quality is the keyword, combined with sound technical knowledge, years of experience and close collaboration with the customer.