RESUMO
The biocompatibility of diamond was investigated with a view toward correlating surface chemistry and topography with cellular adhesion and growth. The adhesion properties of normal human dermal fibroblast (NHDF) cells on microcrystalline and ultrananocrystalline diamond (UNCD) surfaces were measured using atomic force microscopy. Cell adhesion forces increased by several times on the hydrogenated diamond surfaces after UV irradiation of the surfaces in air or after functionalization with undecylenic acid. A direct correlation between initial cell adhesion forces and the subsequent cell growth was observed. Cell adhesion forces were observed to be strongest on UV-treated UNCD, and cell growth experiments showed that UNCD was intrinsically more biocompatible than microcrystalline diamond surfaces. The surface carboxylic acid groups on the functionalized diamond surface provide tethering sites for laminin to support the growth of neuron cells. Finally, using capillary injection, a surface gradient of polyethylene glycol could be assembled on top of the diamond surface for the construction of a cell gradient.
Assuntos
Diamante , Fibroblastos/metabolismo , Teste de Materiais , Nanopartículas , Neurônios/metabolismo , Raios Ultravioleta , Animais , Adesão Celular/efeitos da radiação , Diamante/química , Fibroblastos/citologia , Humanos , Laminina/metabolismo , Microscopia de Força Atômica , Nanopartículas/química , Nanopartículas/ultraestrutura , Neurônios/citologia , Células PC12 , Tamanho da Partícula , Fotoquímica , Ratos , Ácidos Undecilênicos/químicaRESUMO
Horseradish peroxidase (HRP) has been immobilized on the surface of functionalized nanocrystalline diamond (NCD) thin films. The structure of the modified NCD surface as well as the electrochemical behavior of the whole system was characterized by impedance spectroscopy and cyclic voltammetry. The proximity of HRP heme groups to the NCD surface allowed direct electron transfer between them, resulting in two separated one-electron-transfer peaks at 0.05 V and 0.29 V vs Ag/AgCl, corresponding to the cathodic and anodic process, respectively. The heterogeneous electron-transfer constant for both processes was calculated to be 0.066 s(-1), the charge-transfer coefficient alpha = 0.49, and the immobilized enzymatic layer about 2.10(-10) mol/cm2. The modified NCD electrode was used as a third-generation biosensor for hydrogen peroxide determination showing a linear response in the 0.1-45 mM H2O2 range, at +0.05 V vs Ag/AgCl.
Assuntos
Técnicas Biossensoriais/métodos , Diamante/química , Nanopartículas/química , Eletroquímica , Eletrodos , Enzimas Imobilizadas/química , Peroxidase do Rábano Silvestre/química , Microscopia de Força Atômica , Modelos Moleculares , Propriedades de SuperfícieRESUMO
Diamond exhibits several special properties, for example good biocompatibility and a large electrochemical potential window, that make it particularly suitable for biofunctionalization and biosensing. Here we show that proteins can be attached covalently to nanocrystalline diamond thin films. Moreover, we show that, although the biomolecules are immobilized at the surface, they are still fully functional and active. Hydrogen-terminated nanocrystalline diamond films were modified by using a photochemical process to generate a surface layer of amino groups, to which proteins were covalently attached. We used green fluorescent protein to reveal the successful coupling directly. After functionalization of nanocrystalline diamond electrodes with the enzyme catalase, a direct electron transfer between the enzyme's redox centre and the diamond electrode was detected. Moreover, the modified electrode was found to be sensitive to hydrogen peroxide. Because of its dual role as a substrate for biofunctionalization and as an electrode, nanocrystalline diamond is a very promising candidate for future biosensor applications.
