In vitro blood vessel biomodeling with realistic mechanical properties and geometrical structures is helpful for training in surgical procedures, especial those used in endovascular treatment. Poly (vinyl alcohol) hydrogel (PVA-H), which is made of Poly (vinyl alcohol) (PVA) and water, may be useful as a material for blood vessel biomodeling due to its low surface friction resistance and good transparency. In order to simulate the mechanical properties of blood vessels, measurements of mechanical properties of PVA-H were carried out with a dynamic mechanical analyzer, and the storage modulus (G') and loss modulus (G'') of PVA-H were obtained. PVA-Hs were prepared by the low-temperature crystallization method. They were made of PVA with various concentrations (C) and degrees of polymerization (DP), and made by blending two kinds of PVA having different DP or saponification values (SV). The G' and G'' of PVA-H increased, as the C or DP of PVA increased, or as the proportion of PVA with higher DP or SV increased. These results indicate that it is possible to obtain PVA-H with desirable dynamic viscoelasticity. Furthermore, it is suggested that PVA-H is stable in the temperature range of 0°C to 40°C, indicating that biomodeling made of PVA-H should be available at 37°C, the physiological temperature. The dynamic viscoelasticity of PVA-H obtained was similar to that of the dog blood vessel measured in previous reports. In conclusion, PVA-H is suggested to be useful as a material of blood vessel biomodeling.

In this study, the friction of eight kinds of poly(vinyl alcohol) hydrogel (PVA-H) samples has been studied under various load and velocity conditions to elucidate the effects of PVA factors such as the degree of polymerization (DP) and the saponification value (SV) on the tribological behavior of PVA-H. Results showed the variations of the friction properties due to the PVA factors in the two friction conditions found for the hydrogels: elastic friction and hydrodynamic lubrication. In the elastic friction, the larger frictions were induced by the higher values of DP and SV. In the hydrodynamic lubrication, on the other hand, PVA-Hs with lower SV showed larger friction. The results can then be used to adjust the parameters of PVA-H in order to get given friction properties, for instance for the friction between catheter or scalpel and PVA-H, which can be used as a biomodel material of artery or oral mucosa, for the training of surgeons.

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Vascular diseases, such as ischemic heart disease, infarction, aneurysms, stroke and stenosis are a leading cause of serious long-term disability and their mortality rate is as high as that of cancers in many countries. Recently, neurovascular intervention using catheters is a minimally-invasive endovascular technique used to treat vascular disease of the brain, and a navigation system for catheters has been developed to facilitate surgical planning and to provide intra-operative assistance. Since the mechanical properties of a catheter play an important role in reaching the targeted disease, tracking of catheter movement during endovascular treatment may be useful to increase confirmation of the rate of successful operation. In this study, we developed an in vitro tracking system for catheter motion using poly (vinyl alcohol) hydrogel (PVA-H) to mimic an arterial wall. The employed models were made of PVA-H, which is sufficiently transparent to permit observation of catheter movement in the artery. This system is expected to contribute to validation of computer-based navigation systems for surgical assistance.

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