Preventing biofilms

23-Jan-2012

Antibacterial coatings have had limited success in preventing urinary tract infections in catheter users. Novel patented polymer coatings derived from resorcinarenes have been developed in the UK that prevent the formation of the biofilms that can release toxins and cause inflammation and infection.

Urinary infections are a major problem for catheter users and most antibacterial coatings have had limited success. Camstent has developed a promising non-stick coating from an unlikely source.

It was a “eureka” moment for CamStent founder David Hampton when he realised that a polymer, originally designed to prevent moss sticking to roofs, would have huge benefit in the medical industry to stop bacteria colonising urinary catheters. His invention has the potential to save healthcare organisations millions of pounds treating patients with urinary infections.

Clare Twemlow, cfo at CamStent, explains: “Currently bacteria will attach to the surface of a catheter and then spread to form a ‘biofilm’ that can lead to infection. Our coating prevents this first step.”

CamStent’s patented polymer coatings are derived from a well-characterised class of organic compounds called resorcinarenes. The polymer prevents the formation of biofilms, the thin layers of micro-organisms, usually protozoa and bacteria, that aggregate on the surface of implanted medical devices. In medical implant and medical device situations biofilms can directly irritate the surrounding tissue and release toxins that cause inflammation and infection.

Urinary infections, such as E. coli, account for around 40% of hospital-acquired infections and catheters are the main culprits. In the UK, these infections cost an estimated £100m a year to treat, and they cause patients discomfort and longer hospital stays.

One in four hospital patients require a urinary catheter and more than half of adults who have catheters fitted for longer than two weeks during a hospital stay will contract an infection. It is also a major problem in care homes, where residents may have permanent catheters.

“The current options for reducing infection rates include coating the catheter with silver alloy, but this works for only about a week. It is possible to use an antibiotic coating but, unlike our technology, this can lead to antibiotic resistant strains emerging, so it is very rarely used,” Twemlow says.

“The principle of our non-stick surface has a huge range of potential applications. There are other medical uses, for example on stents used to keep arteries open following heart surgery. Orthopaedic implants can also pose an infection risk, so there are opportunities for coating stainless steel.

“It’s not just bacteria we can prevent from sticking, but other organisms such as algae, which can be a huge problem fouling the inside of pipes or the hulls of ships. We’ve even been approached by scientists tracking dolphins – they don’t want biofilms to build up on their tracking device.”

David Hampton, CEO, saw potential benefit for the medical industry

David Hampton, CEO, saw potential benefit for the medical industry

The idea for CamStent came when Hampton, now ceo, was studying at the Judge Business School. He attended a lecture by Professor Charles Stirling about a polymer he was developing for the construction industry, and Hampton suddenly realised what a huge potential this had for the medical industry. To fulfil this potential they founded the company in 2007. CamStent will enter clinical trials next year and the technology should be on the market in two years.

Coating development

Resorcinarenes, the class of organic compounds from which CamStent’s patented polymer coatings are derived, are based on a rigid circular scaffolding that may be anchored to substrates in either polymerised form (a shell) or as individual particles (a coating). The long pendant chains can be designed to resist or attract a variety of agents, promoting adhesion or resistance to different substances.

Variations on the molecule have previously found applications in commercial products such as ion-sensitive electrodes, biomedical sensors, selective-pore membranes, and non-linear optical filters.

The polyethylene glycol (PEG) sidechains that resist attachment of the organisms implicated in urinary tract infections give the biofilm-resistant coating specific advantages over current products:

  • Giving superior resistance to biofilm development and encrustation.
  • Forming a smooth, thin surface over the catheter that minimises patient discomfort and chronic irritation, yet remaining bonded to the catheter throughout normal use.
  • Being non-pharmacologic, it also avoids excess application of antibiotics and possible emergence of drug-resistant strains of pathological organisms.

Its application in the field of cardiology arises because CamStent’s coating resists attachment adhesion of platelets that are the cause of clots and sudden death events in patients receiving drug-eluting stents.

The company believes that ‘non-stick stents’ based on the proprietary coating would have five major advantages over current formulations because they are:

  • Biologically inert, and therefore do not exacerbate inflammation or carry risk of side-effects.
  • Durable, so remain part of the stent surface, effective for the duration of the stent’s life.
  • A thin film, creating a smooth coating that decreases turbulence caused by surface roughness; a factor that has been implicated in coronary thrombosis.
  • Non-pharmacologic, so they will not incur any drug-drug interactions with immuno-suppressants already coupled to the stent. They do not require control of elution rates, control of characterisation or testing for drug stability, availability, release or degradation.
  • Localised in their effect so they can be applied preferentially to the luminal side of the stent, facing the blood stream, while the endothelial side can still be coated with a conventional drug-eluting combination, achieving an optimal combination of antistenotic and antithrombotic properties.

A third application being targeted by the company is that of preventing marine biofilms. Over time, marine organisms attach to submerged surfaces, adding weight and texture to structures and corroding materials that they contact. Biofilms, such as algae, and the subsequent attachment of larger organisms, including seaweed and barnacles, can lead to the accumulation of enormous masses that can diminish a boat\'s manoeuvrability and carrying capacity. Biofouling forces repetitive and costly maintenance of marine structures, with annual costs estimated to be more than US$25bn worldwide.

CamStent is creating a novel oligomer coating to create a surface that is both hydrophilic and protein repellent.

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