Ano-materials coating-based multifunctional medical catheter 

Except for nano-silver materials, many nano-materials with special optical, magnetic or biological properties can endow medical catheter with new natures and functions. For instance, catheter with drug-loading coating, ultrasound visible catheter and MRI visible catheter with MRI compatibility will become the focus of future development. 

(1) Nano-drug-loading coating

Drug-loading nano-particle is a product derived from the combination of nanotechnology and modern medicine and its diameter is generally between 100-500nm. On the one hand, drug-loading nano-particles with micro volumes can improve the drug intake of tissues and cells and increase the concentration of drug at the local lesions; at the same time, it can slowly release drug and thus prolong reaction time. On the other hand, owing to drug-loading nano-particle has a high surface area, therefore, drug loading rate per unit area is increased furthest and thus meet the dosage needed by local treatment. Consequently, making good use of advantages of drug-loading nano-particles and stent implantation and realizing the integration of them, constructing new-type local drug-delivering system for minimally invasive treatment--drug-loading nano-particle blood vessel stent will fundamentally resolve comprehensive factors of restenosis and realize the treatments of cardiovascular diseases. 

(2) Micro-bubble ultrasound angiography nano-coating

Non-invasive and real-time ultrasound angiography has been used widely due to its practical characteristics. However, positioning of catheter has always been the difficulty for the application of ultrasound. If the ultrasound imaging of catheter can be realized, then it will be helpful for doctors to diagnose and treat their patients.

A new-type micro-bubble nano-coating is coated on the surface of catheter can realize real-time ultrasound observation of catheter in the body. Ultrasound angiography coating belongs to a feedback coating (thin polymer coating) which will become very bright under the action of ultrasound. micro-bubbles with air embed into the surface of catheter and reflect signal in all directions especially when the catheter forms a certain angle with the probe; the nano-coating can display catheter by means of ultrasound imaging system by which doctors can know the actual location of catheter in the body. With this new technology, surgical positioning devices and other equipments such as MRI or fluoroscopy instrument may be replaced with ultrasound.  

(3) Magnetic nano-materials coating

MRI makes use of different resonance signals which come from different tissues of organisms under the influence of external magnetic field to form images. Signal strength depends on the content of water in the tissues and the relaxation time of water protons. MRI is particularly effective for the detections of tissue necrosis, ischemia or other malignant lesions; moreover, it can carry out early diagnosis and monitor the metabolism of human body’s circulatory system. 

At present, about 30% of MRI examination in the world belongs to enhanced method, that is to say, it needs to adopt magnetic resonance imaging contrast agents. Magnetic iron oxide nano-particles belong to magnetic nano-materials which are widely used in a clinical diagnosis or treatments such as cancer hyperthermia, MRI contrast agents or molecular markers and other fields. A layer of paramagnetic materials such as nano-sized iron oxide is coated on the surface of catheter will realize the preparation of catheter with magnetic resonance imaging functions. 

Nano-scale devices-based new-type medical catheter and technology

Another important area of the development and application of nanotechnology is nano-scale device. In the field of science and technology of life and medicine, nano-scale devices developed with nanotechnology can circulate in the blood and detect or diagnose each part of the body; at the same time, it can carry out some special treatments and remove thrombus in the cerebral blood vessels and the fat deposits in the heart arteries; besides, it can even realize virus phagocytosis and kill cancer cells, and thus overcome many deadly baffling diseases which can not be cured by means of today's medicine and lead to great changes in the medicine and human health care.   

Catheter is the best carrier by which nano-scale devices can be delivered into patient’s body and realize its function. By means of conventional catheter intervention methods, nano-scale devices can be delivered to some specific sites in the body so as to carry out relevant detections. A miniature ultrasonic probe (1mm×2.5mm) developed recently by U.S.A, for example, can be delivered into the arteries by means of catheter and thus obtain images with high-resolution of various tissues in the arteries or artery walls, which provides a new detection way for the diagnosis and treatment of some difficult and baffling diseases. 

Besides, a new-type nano-micro-motor which draws energy from the surrounding environment and then transform it into electric current can be installed on the implantable medical devices or implantable drug pump such as pacemaker and ventricular defibrillator etc as power source. Theoretically, the life of it is indefinite unless mechanical aging. Once the nano-micro-motor is put into production, it will bring about a fundamental change in the existing medical devices (especially implantable medical devices). 

Summary and Outlook

The combination of nanotechnology and medical devices will play an enormous effect, it can not only resolve some traditional clinical problems, but can develop some new materials with advanced functions. The combination of surface modification technology and nanotechnology provides various new functions for traditional medical catheter, which will significantly improve the clinical application of medical catheters. Surface modification technology has opened up a whole new field for catheters and its relevant medical device products.