title: Towards a label-free optical porous silicon DNA sensor.
abstract: We report on the fabrication of an optical silicon-based label-free DNA sensor. n-Type crystalline silicon wafers have been electrochemically etched to form porous silicon layers and characterized in terms of porosity, pore distribution, surface composition and photoluminescence. Samples (0.25 cm(2)) have been cut and properly derivatized using trimethoxy-3-bromoacetamidopropylsilane in order to link single strand DNA (ss-DNA). Such a molecule is not commercially available and has been ad-hoc prepared by reacting hydrobromic acid and 3-aminopropyltrimethoxysilane in presence of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide as coupling agent. Trimethoxy-3-bromoacetamidopropylsilane acts as a bridge anchored to the porous silicon surface through the silane group while immobilizing ss-DNA by means of the bromoacetamido moiety. We have found that derivatized samples exhibit a photoluminescence that is stable in time and is not modified after exposure to non-complementary DNA strand. On the other hand, a sensible enhancement of the light emission has been observed when the derivatized samples react with the complementary strand, showing that the specific ss-DNA/complementary DNA (c-DNA) interaction can be optically sensed without using further labeling steps. This strongly strengthens the possible role of silicon as a material for biosensors.
authors.affiliation: CR-ENEA Loc. Granatello, Via Vecchio Macello, 80055 Portici, Italy.
authors.forename: Girolamo Di
authors.initials: GD
authors.lastname: Francia
authors.forename: Vera La
authors.initials: VL
authors.lastname: Ferrara
authors.forename: Sonia
authors.initials: S
authors.lastname: Manzo
authors.forename: Salvatore
authors.initials: S
authors.lastname: Chiavarini
mesh_terms: D015374:Biosensing Techniques / Q000295:instrumentation* / Q000379:methods; D004247:DNA / Q000032:analysis* / Q000737:chemistry* / Q000235:genetics; D004867:Equipment Design; D019544:Equipment Failure Analysis; D017403:In Situ Hybridization / Q000295:instrumentation* / Q000379:methods; D008163:Luminescent Measurements / Q000295:instrumentation* / Q000379:methods; D020411:Oligonucleotide Array Sequence Analysis / Q000295:instrumentation* / Q000379:methods; D055095:Optics and Photonics / Q000295:instrumentation; D016062:Porosity; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012825:Silicon / Q000737:chemistry*; D013194:Staining and Labeling
chemical_list: D004247:DNA; D012825:Silicon