Concept and objectives

Various possibilities exist to solve the issue of bacteria in hospitals. The first defence must be to ensure good hygiene practice (both on human and environmental surfaces), and the EU has launched initiatives in recent years to clean up hospitals and increase awareness. The effectiveness of surface cleaning is considerably enhanced on smooth, scratch-free surfaces. However there is only so much that can be done when bacteria are invisible to the naked eye, and enforcing a strict washing routine relies on an individual's conscience.

Commercial silver coatings are available, however the have not been used in hospitals for the following reasons:

  • Cost - the high price of the silver makes them expensive
  • Effectiveness - they are only effective at high temperature (35degC) and humidity (>90%)
  • Environment - leaching of silver ions can cause damage to the environment and an excessive concentration is damaging to health

These factors have lead us to the conclusion that the use of copper-based coatings represents an exciting alternative, which we propose to explore within this project.

Copper coatings offer a low cost, effective, and environmentally friendly solution that could be readily adopted by the healthcare system

The challenge for copper coatings is to restrain the copper nano-particles in a structure that provides antibacterial functionality, but prevents leaching of copper into the environment. The CuVito consortium believes that the silsesquioxane structure, formed using Vitolane technology (figure 1), is the answer.

Figure 1 Vitolane structure

Silsesquioxanes have the formula RSiO1.5 (where R is any organic molecule), and form cage or ladder structures. Standard silsesquioxane structures have organic side groups (denoted 'R' in figure 1) that complement the basic silsesquioxane properties. Incorporating the silsesquioxane nano-structure within a coating formulation confers hardness and abrasion resistance and, by selecting appropriate organic side groups (e.g. acrylate, methacrylate, glycidoxy) to chemically bond with the organic resin constituents in the formulation, cross-link density may be controlled, enhancing coating durability. This makes silsesquioxanes inherently suited for use in coatings for surface which require regular cleaning to a high standard.

Silsesquioxanes have been available for some years but at a prohibitively high cost, due to the complexity of manufacture. Vitolane technology represents an alternative, cost effective production route which can be readily tailored to incorporate the most appropriate side groups for a given application. The process route has been patented and is currently undergoing scale up for commercial manufacture by Thomas Swan. It is proposed to make use of this unique processing feature to provide suitable side groups (R2) to bond directly to the copper, yielding antibacterial properties and resolving the issue of leaching, since other groups within the structure (R1) will be used to bond within the coating structure. This is illustrated in figure 2.

Figure 2 The vitolane - copper nanoparticle concept

Research will determine the most suitable form for the nanoparticles to be bonded to the silsesquioxane, and also the manufacturing process. The copper-silsesquioxane formula is most likely to take the form of an additive, and commercial formulation of the coating will then be required.

The science and technology objectives of the project can be summarised:

  1. Develop a copper nano-particle production process capable of producing functionalised nano-particles at a cost of less than 8,000$/kg (12,000 €/kg)
  2. Functionalise silsesquioxanes with copper using Vitolane technology, targeting 90% functionalisation
  3. Produce a commercially acceptable coating, meeting a market price of 5$/kg (7 €/kg)
  4. Validate coating in a hospital environment reduce hospital acquired infections by 10%.