Cecilia Vahlberg

Surface functionalization and biomedical applications based on SiC

The search for materials and systems, capable of operating long term under physiological conditions, has been a strategy for many research groups during the past years. Silicon carbide (SiC) is a material, which can meet the demands due to its high biocompatibility, high inertness to biological tissues and to aggressive environment, and the possibility to make all types of electronic devices.This paper reviews progress in biomedical and biosensor related research on SiC. For example, less biofouling and platelet aggregation when exposed to blood is taken advantage of in a variety of medical implantable materials while the robust semiconducting properties can be explored in surface functionalized bioelectronic devices.

Biotinylation of ZnO nanoparticles and thin films: a two-step surface functionalization study.

This study reports ZnO nanoparticles and thin film surface modification using a two-step functionalization strategy. A small silane molecule was used to build up a stabilizing layer and for conjugation of biotin (vitamin B7), as a specific tag. Biotin was chosen because it is a well-studied bioactive molecule with high affinity for avidin. ZnO nanoparticles were synthesized by electrochemical deposition under oxidizing condition, and ZnO films were prepared by plasma-enhanced metal-organic chemical vapor deposition. Both ZnO nanoparticles and ZnO thin films were surface modified by forming a (3-mercaptopropyl)trimethoxysilane (MPTS) layer followed by attachment of a biotin derivate. Iodoacetyl-PEG2-biotin molecule was coupled to the thiol unit in MPTS through a substitution reaction. Powder X-ray diffraction, transmission electron microscopy, X-ray photoemission electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, and near-edge X-ray absorption fine structure spectroscopy were used to investigate the as-synthesized and functionalized ZnO materials. The measurements showed highly crystalline materials in both cases with a ZnO nanoparticle diameter of about 5 nm and a grain size of about 45 nm for the as-grown ZnO thin films. The surface modification process resulted in coupling of silanes and biotin to both the ZnO nanoparticles and ZnO thin films. The two-step functionalization strategy has a high potential for specific targeting in bioimaging probes and for recognition studies in biosensing applications.

Surface engineering of functional materials for biosensors

Single crystal SiC with suitable surface termination and ZnO films on top have been grown. Biomolecular immobilization on the grown surfaces has been performed. APTES on Si terminated SiC surfaces and reaction with a compound containing a pre-activated carboxylic group was used. The rate of success for surface functionalization was monitored by XPS. A successful two-step functionalization including binding of MPA through an amide bond formation, between the amine group of APTES and the carboxylic group in MPA on ZnO epilayers, was shown as a proof of concept for biofunctionalization

Surface Functionalization of SiC for Biosensor Applications

SiC is a biocompatible material and a candidate as a transducer for biosensors. Here we have investigated the possibility to functionalize SiC with biomolecules. We have also processed very simple devices and performed electrical characterization. Double polished SiC samples with a C-face substrate and Si-face low doped epilayer have been functionalized on both sides. The SiC was first treated by HF in order to remove the native oxide, partly successful on the Si-face side but probably not on the C-face side. MPTMS, 3-mercaptopropyl trimethoxysilane, was chosen as the biomolecule since it has both a silanol group to be used as an anchoring group to the substrate and a thiol group available for further linking possibilities. The functionalization was evaluated by XPS, contact angle experiments, AFM and electrical measurements. The MPTMS molecules attached with the thiol (or sulphur containing) group pointing out from the surface on both faces of the SiC. Interesting differences between the two faces are however revealed by the analysis.