Surface modifications of silicon nitride for cellular biosensor applications
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Thin films of silicon nitride (Si3N4) can be used in several kinds of micro-sized biosensors as a material to monitor fine environmental changes related to the process of bone formation in vitro. We found however that Si3N4 does not provide optimal conditions for osseointegration as osteoblast-like MG-63 cells tend to detach from the surface when cultured over confluence. Therefore Si3N4 was modified with self-assembled monolayers bearing functional end groups of primary amine (NH2) and carboxyl (COOH) respectively. Both these modifications enhanced the interaction with confluent cell layers and thus improve osseointegration over Si3N4. Furthermore it was observed that the NH2 functionality increased the adsorption of fibronectin (FN), promoted cell proliferation, but delayed the differentiation. We also studied the fate of pre-adsorbed and secreted FN from cells to learn more about the impact of above functionalities for the development of provisional extracellular matrix on materials interface. Taken together our data supports that Si3N4 has low tissue integration but good cellular biocompatibility and thus is appropriate in cellular biosensor applications such as the ion-sensitive field effect transistor (ISFET). COOH and NH2 chemistries generally improve the interfacial tissue interaction with the sensor and they are therefore suitable substrates for monitoring cellular growth or matrix deposition using electrical impedance spectroscopy.
KeywordsOsteocalcin Alkaline Phosphatase Activity Electrical Impedance Spectroscopy Osteocalcin Production Initial Cell Adhesion
This work was part of the European funded project NMP3-CT-2005-013912. The authors thank Drs. F. Bessueille and M. Pla-Roca of the Barcelona Science Park for help with the silanisation. J.G. acknowledges support from the Catalonian Government, Grant (2006FI00863), and Folke y Margit Pehrzon foundation. G.A acknowledges grants AGAUR 2004PIV25 from the Catalonian Government and SAB2004-0209 from the Spanish Ministry of Education and Science. E.E. acknowledges the Spanish Ministry of Education and Science for the Juan de la Cierva Grant. Roche Diagnostics is acknowledged for the provided vitamin D.
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