Studies On Functionalized Diamond-like Carbon Film For Regulation Of Neural Cells Growth

To select the appropriate substrate material for cell sensor and realize the effective control and real-time detection of cell behaviors in vitro is of great significance in the study of cell physiology and pathology, medical diagnosis, drug screening and other areas. With low deposition temperature, good resistance to friction and wear, perfect acid and alkali corrosion-resistant ability and long-term stability, good biocompatibility and other characteristics, diamond-like carbon (DLC) film is regarded as a preferred material for cell sensor substrate. However, the intrinsic compressive stress, low electro-catalytic activity and biochemical inertness inhibit its use as biological electrode material. In this paper, element doping and chemical molecular modification was applied to modify the DLC film, and the effects of modification on the microstructure, cell compatibility and electrochemical properties of the film were discussed.Differently doped DLC films were prepared by using nitrogen (N2), phosphine (PH3) as gas doping source, or by adding boron powder or platinum powder to the graphite cathode target with the filtered cathodic vacuum arc (FCVA) technique. Atomic force microscope (AFM), Raman spectrum and X-ray photoelectron spectroscopy (XPS) were carried out to character the performances of the DLC films. Our results showed that element doping did no harm to the smooth surface and only slightly changed the amorphous structure of the film by a little increase of the amount of the sp2 hybridized carbon. The adhesion, proliferation and apoptosis experiments of PC 12 cells showed that B, N, P doping improved the cell compatibility of DLC film, but the incorporation of Pt had the opposite effect. After 5-day culture, compared to the undoped DLC film, the cell density on the phosphorus doped film increased by about 60% and the apoptotic rate reduced by about 40%, while the cell density on the film with nitrogen and platinum codoping decreased by about 40% and the apoptosis rate increased by 30%. The electrochemical test showed that the DLC films doped with different elements had distinct catalytic abilities on hydrogen peroxide, especially, N and P doping obviously enhanced the catalytic ability.Through covalent bonding, the surface of nitrogen doped DLC (DLC:N) films were connected with chemical active molecules such as dopamine (DA), amino phenylboronic acid (APBA) and adenosine triphosphate (ATP), respectively, to achieve further modification of the doped DLC films. The microstructure of the modified films did not change obviously, and the surface roughness only slightly increased by about 0.3 nm. The APBA and ATP modified films had better cell compatibility, while DA modification had the opposite effect. After 3-day culture, the cell activity on APBA and ATP modified DLC:N films were about two times of that on the unmodified film. For the DA modified film, the cell activity is reduced. Chemical molecular modification enhanced the catalytic ability to H2O2 oxidation and the detcetion sensitivity of the APBA modified film is increased up to about 4 times when compared to the original film, so the film can be better used to dectect H2O2 released by the stimulated cells in vitro. The electrocatalytic activity of the DLC:N array electrode prepared by photolithography was also significantly enhanced by 10～30 times.In summary, the regulation of electrochemical properties and cell compatibility of the DLC film can be realized at the same time by element-doping or chemical molecular modification. Via choosing appropriate doping elements and modification molecules, satisfactory cell sensor substrate originated from DLC films can be obtained.