Introduction: The Institute "Dante Pazzanese" of Cardiology (IDPC) of São Paulo develops Ventricular Assist Devices (VAD) that can provide hemodynamic stability compatible with the patient's body with heart failure (HF) serious; circulatory support is implemented as a permanent support device, treatment or recovery[1]. Implantable medical devices should be made of biomaterials which do not present any form of degradation or deformation for at least five years. The titanium is a biometal applied for implants since the 60's for possessing high corrosion resistance, low density and chemical stability; However, when kept in medium to body fluids for a long time, the biometal releases ionic species which can trigger electrochemical reactions in the body and engage the homeostasis of the immune system[2].
Currently the IDPC study and apply the technique Oxidation Plasma Electrolytic (PEO) to texture the surface of titanium medical grade and thus improve the interaction of the implant surface with the living organism. Titanium after being processed and polished, features smooth surface appearance; After the substrate is subjected to oxidation by atmospheric plasma process presents rough surface appearance to the presence of pores and frameworks on the order of 5 to 20 microns, see Figure 1[1].
Interaction with blood tests should be performed with samples in medical grade titanium polished and rough titanium samples to prove the bioactivity improved by natural cellular lining.
Materials and Methods: The in vitro testing was conducted at the Engineering Center for Circulatory Assistance (ECAC) of the IDPC with support from the Department of Experimental Surgery of the same institution. The ability of a material to promote metabolic alterations in cells micrographic and dynamics are targets of interpretations in this study. Two samples of titanium were subjected to a hemodynamic testing, one with a smooth surface and hydrophobic and the other with the rough surface and hydrophilic character to compare the biochemical and cellular dynamics with respect to the surface bioaspecto.
The test circuit follows the profile used to assess damage to red blood cells by mechanical trauma of a DAV. The sample was positioned at the outlet of the blood pump inside the PVC tube; The test lasted 3 hours, with fixed flow rate of 5 L/min per 100 mmHg. They were held three collections of samples for biochemical analysis with an interval of 60 minutes between each collection and an initial sample called T0, withdrawal to the start of the test. A portable digital microscope was used to record the micrographs of the surface of the titanium samples before and after hemodynamic assay.
Results and Discussion: At the end of the experiment, microscopic analysis found the presence of blood cells and adhered firmly anchored to the roughened surface of titanium; Polished titanium while on the surface there was no adhesion just deposition, see Figure 2. Biochemical analysis by gas analysis also showed better bioactivity of blood with the modified titanium surface plasma, i.e., the measured biochemical parameters were kept closer to the values reference; in Figure 3.
Conclusion: When the blood enters in contacts with an artificial surface, adsorption occurs a protein layer on the interface. Thus, in vivo testing future will be performed with samples modified titanium plasma to study the control of the rate of growth of fibrous tissue, and neointima thickness as well as the formation of thrombi side neointima.
Universidade Estadual Paulista; Fundação Adib Jatene
References:
[1] Sá, R., Furlanetto, G., Cruz, N., Drigo, E., Leão, T., Leme, J., Fonseca, J., Utiyama, B., Andrade, A., Bock, B.. Titanium Implant Modified by Plasma Electrolytic for Neointima Formation in Blood Pumps. 23rd ABCM International Congress of Mechanical Enginnering; December 6 – 11, 2015. Rio de Janeiro, RL, Brazil.
[2] Boshi, A.(1996) O. O que é necessário para que um material possa ser considerado um biomaterial? Encontro Nacional de Biomateriais, 2., 1993, São Paulo. Resumos. São Paulo: IPEN-CNEN/SP, 1996.