In vitro and in vivo evaluation of ultrananocrystalline diamond as an encapsulation layer for implantable microchips.
Thin ultrananocrystalline diamond (UNCD) films were evaluated for use as hermetic and bioinert encapsulating coatings for implantable microchips, where the reaction to UNCD in vitro and in vivo tissue was investigated. Leakage current tests showed that depositing UNCD coatings, which were conformally grown in (1% H2) Ar/CH4 plasma, on microchips rendered the surface electrochemically inactive, i.e. with a very low leakage current density (2.8×10(-5)Acm(-2) at -1V and 1.9×10(-3)Acm(-2) at ±5V) ex vivo. The impact of UNCD with different surface modifications on the growth and activation of macrophages was compared to that of standard-grade polystyrene. Macrophages attached to oxygen-terminated UNCD films down-regulated their production of cytokines and chemokines. Moreover, with UNCD-coated microchips, which were implanted subcutaneously into BALB/c mice for up to 3months, the tissue reaction and capsule formation was significantly decreased compared to the medical-grade titanium alloy Ti-6Al-4V and bare silicon. Additionally, the leakage current density, elicited by electrochemical activity, on silicon chips encapsulated in oxygen-terminated UNCD coatings remained at the low level of 2.5×10(-3)Acm(-2) at 5V for up to 3months in vivo, which is half the level of those encapsulated in hydrogen-terminated UNCD coatings. Thus, controlling the surface properties of UNCDs makes it possible to manipulate the in vivo functionality and stability of implantable devices so as to reduce the host inflammatory response following implantation. These observations suggest that oxygen-terminated UNCDs are promising candidates for use as encapsulating coatings for implantable microelectronic devices.
Department of Applied Science, National Hsinchu University of Education, Hsinchu 30014, Taiwan, ROC. Electronic address: yingchieh@mail.nhcue.edu.tw.
Ying-Chieh
YC
Chen
Department of Applied Science, National Hsinchu University of Education, Hsinchu 30014, Taiwan, ROC.
Che-Yao
CY
Tsai
Department of Materials Science and Engineering, National Tsing-Hua University, Hsinchu 30013, Taiwan, ROC.
Chi-Young
CY
Lee
Department of Physics, Tamkang University, Tamsui 251, Taiwan, ROC.
I-Nan
IN
Lin
D000818:Animals; D002448:Cell Adhesion; D002460:Cell Line; D049109:Cell Proliferation; D048430:Cell Shape; D018932:Chemokine CCL2 / Q000378:metabolism; D018130:Diamond / Q000737:chemistry*; D004553:Electric Conductivity; D020007:Implants, Experimental / Q000009:adverse effects; D007249:Inflammation / Q000473:pathology; D051379:Mice; D008807:Mice, Inbred BALB C; D046228:Microarray Analysis / Q000295:instrumentation / Q000379:methods*; D053758:Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D019919:Prosthesis Implantation; D015203:Reproducibility of Results; D013499:Surface Properties; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D018932:Chemokine CCL2; D014409:Tumor Necrosis Factor-alpha; D018130:Diamond
Biocompatibility; Encapsulation layer; Implantable; UNCD