Time-of flight secondary ion mass spectrometry (ToF-SIMS) has been employed
to characterize and evaluate the surface of a novel biochip prototype, con
sisting of an array of gold microelectrodes on which the laminin-derived ol
igopeptide CDPGYIGSR-NH2 was immobilized. The microelectrodes were isolated
from each other via a thin, film of amorphous Teflon (Teflon AF). Prior to
studying biochip surfaces, characterization of gold surfaces (supported on
oxidized silicon wafers) incorporating the oligopeptide was carried out, t
o serve as reference standards. With positive-mode ToF-SIMS, the whole pept
ide could be observed, and in addition, ions that were characteristic of th
e constituent amino acids of the oligopeptide could also be observed. The m
icrofabrication process for biochip realization comprised several steps whi
ch included the use of compounds that could potentially contaminate the res
ultant surface. Therefore, it was important to: investigate the chemical co
mposition of these surfaces with the highest level of sensitivity. With ToF
-SIMS imaging it was possible to detect oligopeptide-related ions only on t
he microelectrodes and nowhere else. Assessment of the spectral data from u
ser-defined regions within the imaged areas revealed that the microelectrod
e and Teflon surfaces were devoid of any process-related contamination. In
some cases, ToF-SIMS revealed some defects on the biochip surface, which wo
uld otherwise not be readily detectable, thereby offering some insight into
areas that might require further optimization in the fabrication process.