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Título/Title/Titulo

DYNAMIC FUNCTIONALIZATION OF VASCULAR SCAFFOLDS

Introdução/Introduction/Introdución

Currently, there is a great lack of vascular grafts suitable for use in vessel replacement surgeries, especially for application in small vessels. The commercially available synthetic supports have a high failure rate due to thrombosis and intimal hyperplasia.Tissue engineering (TE), therefore, has been evaluated as an alternative for the development of vascular substitutes. In TE, tubular scaffolds can be produced and associated with drugs in order to prevent the formation of thrombi in their interiors guaranteeing the sucess of its clinical application. However, the geometry of these scaffolds can minimize their binding to biomolecules, especially in their lumen.

Objetivos - Metodologia - Resultados - Discussão dos Resultados/Objectives - Methodology - Results - Discussion of Results/Objetivos - Metodología - Resultados - Discusión de los resultados

This study has aimed to evaluate the use of bioreactors to functionalize dynamically the internal surface of vascular scaffolds with the heparin anticoagulant. Tubular scaffolds of poly(caprolactone) with 6 mm diameter were produced by electrospinning. The scaffolds were inserted into rotating bioreactor chambers and their lumen were filled with 2M NaOH for 30 minutes. Subsequently, the supports were rinsed with water and then left in contact with 2 mL of a fresh solution of 1% (w/v) heparin, 5 mg/mL N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide (EDC) and 5 mg/mL N-hydroxysuccinimide (NDS). Bioreactors were rotated at 1 rpm, overnight. After functionalization, the scaffolds were removed from the chambers and cut into 1 cm2 pieces. Following this, these samples were submitted to the blue toluidine test for determination of heparin content. As a control, flat scaffolds, with 1 cm2, were statically functionalized. For this, the heparin solution was dispensed on the surface of the scaffolds and maintained overnight. The blue toluidine test demonstrated that the heparin content was significantly higher in statistically functionalized biomaterials. The tubular scaffolds exhibited 131.9 /cm2 of heparin. Meanwhile, the scaffolds functionalized by the static method showed 143.5 μg/cm2 of heparin on their surface. This result was already expected. In static functionalization, there is no fluid movement and, thus, the chemical bonds between biomolecules and 3D structures can be maximized. Although the heparin binding was lower when dynamic functionalization was performed, this method is ideal for the association of drugs to tubular structures. The rotating bioreactor allows for a constant contact of the biomolecules with the entire internal wall of the material structure, ensuring homogenous functionalization. Moreover, the concentration of an anticoagulant, obtained with the dynamic process, is enough to confer antithrombogenic properties to the scaffolds. In accordance with previous studies of this research group, the obtained concentration prevents the formation of thrombi on the biomaterial surface. Another important feature of the homogeneous heparin functionalization of scaffolds is that they can reduce the proliferation of smooth muscle cells and thus, prevent the occurrence of neointimal hyperplasia.

Considerações Finais/Final considerations/Consideraciones finales

The present work has demonstrated that the use of rotating bioreactors allows for the attachment of heparin to the internal surface of tubular scaffolds in an adequate concentration for their thrombogenic activity. The homogenous functionalization of tubular biomaterials with heparin can prevent thrombosis and intimal hyperplasia in their lumen, the two major causes of failure of the vascular grafts.
Acknowledgments: MCTIC, FINEP, CNPq and Stem Cell Research Institute (IPCT).

Palavras-chave/Key words/Palabras clave

tubular scaffolds, vascular scaffolds, vascular tissue engineering, bioreactor