Sterilization

with Atmospheric Plasma

Sterilization and disinfection are terms used for processes whereby materials and items are freed of living microorganisms, including their dormant states (e. g. spores). The state thus achieved is called “sterile”.

Sterilization ideally kills all the microorganisms contained in or adherent to an object, including their permanent forms such as spores, while at the same time viruses, prions (infectious proteins), plasmids and other DNA fragments are destroyed. Application examples include materials (e. g. foods, pharmaceuticals, solutions), items, packaging or tools (e.g. containers for cultivating microorganisms, endoscopes).

In practice, there is no guarantee for 100% sterilization. It is customary to demand the reduction of microorganisms capable of proliferation by a factor determined by the field of application (in powers of ten), or alternatively a certain degree of probability for complete sterilization.

The sterilizing effect of atmospheric pressure plasma has been principally substantiated by a great number of studies. Its mode of action is a complex interplay of many components, which can be precisely balanced with an adequate means of control.

In the near field, atmospherically generated plasma works through a combination of:

• Light (UV radiation)
• Electrons with high kinetic energies up to several keV
• Highly excited ions and short-lived oxygen species
• Electric fields

Secondary plasma allows for a highly reactive mixture of several chemical species to be administered to a surface:

• Ozone
• Peroxide
• Nitrogen oxide

Additionally, thermal energy is efficiently entered into the layer close to the surface.

Depending on the application in question, suitable plasma systems are either pulsed atmospheric arc discharge technology such as for example Plasma or Piezo cold discharge .

When the Piezo plasma is used, the predominant effect is that of UV light (in the near field) together with ROS (reactive oxygen species, especially ozone) and RNS (reactive nitrogen species). Very high electric fields can also be induced in the near field. Thermal effects, on the other hand, are minimal.

PDD technology, which the Piezo plasma is based on, is currently the most efficient known ozone generator.

Due to the high energy density in the atmospheric arc, the Plasma can generate an extensive number of highly reactive species. Depending on the composition of the input gas, the balance between ozone, nitrogen oxides or peroxides can be adjusted. At the same time, surface temperature can be shock-raised to a degree resulting in the decomposition of all organic or biological materials. Under the right circumstances, almost perfect sterility can be achieved.

Industrial products

Packaging in pharmaceutics, sterile goods, blister packs, beverage bottling, foods

In most cases, industrial processes require virtually complete sterilization for low levels of contamination, with cycle times as brief as possible (<1s). This makes pulsed atmospheric arc discharge the process of choice.

Often, however, processes require the extremely high output rate of ROS (reactive oxygen species) provided by piezoelectric discharge with its low power input, high efficiency, compact design and maximal operative safety. Hollow spaces are efficiently sterilized.

Resistant Pathogens

Resistant pathogens pose a substantial threat worldwide, especially in surgical intensive care units, burns units, neonatal units, and in geriatric care. Increasing effort is devoted to finding methods of killing multi-resistant pathogens without the use of antibiotics in clinical practice. The Piezo plasma has proved successful in effectively neutralizing the methicillin-resistant staphylococcus aureus (MRSA), a pathogen deemed especially dangerous.

Consumer products

Cosmetic devices, everyday consumer products, sports bags, shoes, airtight containers – for a wide variety of consumer products, the sterilizing and deodorizing effects of cost-effective piezo technology naturally offer the user lots of added value.

Medical implants

In orthopedics, PEEK implants have been firmly established for quite some time, especially when the spinal column is concerned. Increasingly, this high-performance plastic material is also used to make dental implants.

The reasons for this lie in the excellent mechanical properties of the polymer, in its biocompatibility and biostability, its sterilizability and x-ray transparency.

Positive effects of plasma:

Firstly, plasma treatment destroys potential microorganisms on surfaces. The sterilizing effect of plasma helps reduce the risk of infection, while at the same time a fine-cleaned surface increases the body’s tolerance for the implant as a foreign body.

The second effect is based on the enhanced surface energy of the plastic. The resulting wettability facilitates better coating of the implant surface with endogenous substances (e. g. blood and other fluids), which supports and speeds up the healing process.

Living tissue and medical applications

The field of plasma medicine best researched is the treatment of wounds and infected skin areas. As direct contact with living tissue is desirable, only so-called cold plasma is suitable for this treatment. The effect of cold plasma at atmospheric pressure is complex and involves UV radiation, reactive compounds and electric fields.

The interplay of these factors greatly reduces bacterial growth, which speeds up healing processes. Additionally, plasma may be able to prevent infection around implants and inhibit the growth of bacteria that cause caries in tooth enamel. We are actively supporting fundamental research in this field.

With PDD®, we have substantially advanced technology by developing the most effective and powerful method comparable. Its basic technology is equally suited to direct wound care via plasma jet and to extensive barrier discharge onto the skin area to be treated.

In spite of these powerful effects on a wide spectrum of typical germs, among them some multi-resistant pathogens that are increasingly moving into focus, known side effects are comparatively weak. Moreover, combined applications with actively added bioactive substances are entirely possible.

In many instances, transitions between medical and cosmetic therapy are fluent.