Medical catheter plays an important role in various medical fields such as surgery, treatment and care, diagnosis and interventional therapy etc. By means of nanotechnology-based new-type medical catheter, several issues brought about by traditional catheters such as blood biocompatibility, mechanical properties or restenosis can be overcome successfully. At the same time, new-type multifunctional catheter such as antibacterial catheters with capacity of drug-loading or catheters with more advanced ultrasound and magnetic resonance imaging system etc can come true finally by means of the combination of nano-materials and catheter. Moreover, integrating catheter with more precise nano-components can realize human body’s real-time or location detection. In this article, we will specifically describe these new-type nanotechnology-based catheters.

Modifying medical catheters with nanotechnology and nano-materials

(1) Surface modification of medical catheter

Blood compatibility has been a primary problem for the application of catheter material which must be overcome in advance and introducing hydrophilic functional groups onto the surface of medical catheter is an effective means to improve its blood compatibility; it is a new surface modification technology that controlling nanostructures of surface of medical catheter or fixing biological molecules on it. Self-assembled monolayer end-group, for example, it belongs to a new two-dimensional technique, which can be used to regulate or control the surface properties of medical device made by polymer.

For medical catheter, surface modification will create new features and surface lubrication is an important factor we should always take into account. At present, surface lubricity has become one of essential features of high-end medical catheters. Improved surface lubricity will bring about a series of special features: reducing damage on the interface between organs and catheter and alleviating patients’ suffering; reducing platelet aggregation and fibrin adsorption as well as decreasing bacterial adsorption on the surface of materials; lubricant coating on the surface of medical catheter facilitate catheter to arrive at the end of blood vessel and provide very precise impetus or torque control etc so as to avoid serious injury. Therefore, both clinicians and patients will give priority to medical devices such as medical catheters or guide wire with high-lubricity and low-friction. Stability is one of key factors for the successful application of lubricating coating and adopting nano-materials coating as the interlayer of medical catheter and lubricating materials can provide a stable surface with high-lubricity.

(2) Improving catheter performances with nano-materials

Interventional catheter is becoming more small and thin, especially micro-invasive ultra-lubricated thin  catheter for interventional therapy which can easily enter into some small and distorted branches of blood vessels; this advantage is becoming increasingly obvious in the course of treatment and thus put forward higher requirements for the mechanical properties of catheter materials.

Nano-particles and polymer composites can be adopted as a new-type catheter material. It contains nano-particles polymer and has a better biological and mechanical or thermal properties, therefore, it is more competitive than traditional wires. Polymer and nano-materials can form organic/inorganic composite materials. Nowadays, it is composed of metal nano-materials and polymer such as gold, silver or copper and other precious metals. Recent studies have shown that mixing gold and silver nano-particles into catheter materials can significantly improve the physical and chemical properties of polyurethane composites such as strength modulus and chemical stability etc. Owing to silver nano-particles can reduce crystallization, so the thermal stability and mechanical properties of polyurethane can be improved significantly. Gold nano-particles can obviously reduce its pyrolysis temperature and glass transition temperature. Animal test results showed that polyurethane containing silver/gold nano-particles has higher biological tolerance and lower rejection response.

Antibacterial medical catheter made by nano-materials 

Nowadays, medical catheter has been increasingly used, but its complications especially bacterial attachment-related infections always limit the use of catheter. Traditional antibacterial methods include antibiotics coating and catheter with negative surface charge etc. However, it is unable to provide persistent, broad-spectrum antibacterial effects and its side effects have not been resolved properly.

Nanotechnology provides a new way for the antibacterial treatment. Nowadays, a variety of metal nano-antibacterial materials have been developed successfully such as copper, zinc oxide, titanium dioxide, magnesium oxide, gold and silver etc. study shows that nano-silver can provide the most effective anti-bacterial effects and it is anti-bacterial or anti-virus as well as be resistant to other eukaryotic micro-organisms. Comparing with other clinically conventional antibacterial agents, nano-silver belongs to a broad-spectrum antimicrobial agent and even a small amount of it can obtain a bactericidal effect. Differing from antibiotics, silver will not lead to drug resistance and provides safer and long-lasting effects. Recent studies found that nano-silver has the ability to fight against HIV-1 virus and hepatitis B virus, which has opened up new space for the application of nano-silver.

Nano-silver can destroy some important physiological functions of micro-organisms by means of a variety of ways. Current studies make use of surface treatment methods to assemble nano-silver particles onto the catheter. All catheters integrated with nano-silver will be antibacterial and long-term release of silver ions can ensure a long-lasting anti-bacterial effect, and thus infections or blockage of medical catheter can be avoided effectively.

Researches at home and abroad adopted different techniques such as plasma deposition technique and catheter surface instilling processing etc to resolve the issue of nano-silver deposition. By means of some unique methods, they prepared AgBr mixed materials with nano-particles and polymer which can be adopted as surface coating in that its double-effect sterilization.

Except for surface plasma deposition technique, coating medical catheter with nano-silver particles can also obtain catheters with efficient antibacterial effect. After implanting the catheter into a specific site, it can release directionally silver ions and realize targeted antibacterial effects; processing silicone catheter with CO₂ supercritical technology and combining nano-silver-particles on its surface can also prepare antibacterial catheter; nano-silver-particles on the surface of instilling treatment catheter is just like a diffuse potential barrier which can reduce infusion potential to 10keV and thus improve surface activity. Moreover, infections caused by short-term use of equipment can be avoided by this antibacterial catheter. 

At present, nano-silver-technology-based anti-bacterial has come into international markets, for example, U.S.A. I-FLOW Bio-Materials Co. launched nano-silver sterile series catheters whose principle is adding a thin nano-silver coating on the ordinary polypropylene medical catheter. U.S.A. EHSY Co. also successfully developed anti-infection central venous catheter which is made of silver-particles (5-40nm) and polyurethane distributed in the matrix of catheter. Silver-particles released from the surface of catheter play an important role in anti-microbial effect and sterilization. This metallic silver particles anti-infection catheter can exist in the body of animal about 60- 90 days.