AVS 46th International Symposium
    Biomaterial Interfaces Group Monday Sessions
       Session BI-MoM

Paper BI-MoM1
TOF-SIMS Investigation of the Immobilization Process of PNA and DNA Biosensor Chips

Monday, October 25, 1999, 8:20 am, Room 613/614

Session: Biosensor-Biology Interface
Presenter: H.F. Arlinghaus, Physikalisches Institut der Universität Münster, Germany
Authors: H.F. Arlinghaus, Physikalisches Institut der Universität Münster, Germany
C. Höppener, Physikalisches Institut der Universität Münster, Germany
J. Drexler, Physikalisches Institut der Universität Münster, Germany
M. Ostrop, Physikalisches Institut der Universität Münster, Germany
Correspondent: Click to Email
A novel DNA sequencing method is described that uses peptide nucleic acid (PNA) hybridization biosensor chips. PNA is a synthesized DNA analog, in which both the phosphate and the deoxyribose of the DNA backbone are replaced by polyamides. This DNA analog retains the ability to hybridize with complementary DNA or RNA sequences. Because the backbone of DNA contains phosphates, of which PNA is free, an analysis technique that identifies the presence of phosphates in a molecular surface layer allows the use of unlabeled DNA for hybridization on a biosensor chip. We used TOF-SIMS to investigate its ability to distinguished between PNA and DNA molecules on surfaces, as well as the PNA and DNA immobilization process. For this purpose we immobilized silane SA-layers on UV/ozone treated silicon wafers and bonded PNA and DNA with different concentrations to these layers. It was found that the immobilization process is strongly dependent on the concentration and the immobilization time and that under optimized conditions, PNA and DNA can be covalently bonded to the silane SA-layers. A comparison between positive and negative TOF-SIMS spectra showed that the masses corresponding to PO@sub 2@@super -@, PO@sub 3@@super -@ and H@sub 2@PO@sub 4@@super -@ provide the best correlation to DNA presence. The phosphate yield could be significantly increased with polyatomic ion bombardment. Temperature-programmed SIMS (TP-SIMS) was used to measure the thermal stability of the immobilized layers showing that characteristic silane fragment ions decrease at a temperature of about 70°C. It can be concluded that the combination of TOF-SIMS and TP-SIMS provides a very useful technique for examining the complexity of the immobilization and hybridization processes of nucleic acid and that TOF-SIMS has the potential for providing a rapid method for DNA/RNA sequencing and diagnostics.