title: Biomolecular screening with encoded porous-silicon photonic crystals.
abstract: Strategies to encode or label small particles or beads for use in high-throughput screening and bioassay applications focus on either spatially differentiated, on-chip arrays or random distributions of encoded beads. Attempts to encode large numbers of polymeric, metallic or glass beads in random arrays or in fluid suspension have used a variety of entities to provide coded elements (bits)--fluorescent molecules, molecules with specific vibrational signatures, quantum dots, or discrete metallic layers. Here we report a method for optically encoding micrometre-sized nanostructured particles of porous silicon. We generate multilayered porous films in crystalline silicon using a periodic electrochemical etch. This results in photonic crystals with well-resolved and narrow optical reflectivity features, whose wavelengths are determined by the etching parameters. Millions of possible codes can be prepared this way. Micrometre-sized particles are then produced by ultrasonic fracture, mechanical grinding or by lithographic means. A simple antibody-based bioassay using fluorescently tagged proteins demonstrates the encoding strategy in biologically relevant media.
authors.affiliation: Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0358, USA.
authors.forename: Frédérique
authors.initials: F
authors.lastname: Cunin
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Schmedake
authors.forename: Jamie R
authors.initials: JR
authors.lastname: Link
authors.forename: Yang Yang
authors.initials: YY
authors.lastname: Li
authors.forename: Jennifer
authors.initials: J
authors.lastname: Koh
authors.forename: Sangeeta N
authors.initials: SN
authors.lastname: Bhatia
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Sailor
mesh_terms: D000818:Animals; D000906:Antibodies / Q000276:immunology*; D000941:Antigens / Q000032:analysis / Q000276:immunology*; D015374:Biosensing Techniques / Q000295:instrumentation* / Q000379:methods*; D002417:Cattle; D003460:Crystallization; D005453:Fluorescence; D006041:Goats; D007118:Immunoassay / Q000295:instrumentation / Q000379:methods; D008567:Membranes, Artificial; D015335:Molecular Probes / Q000032:analysis; D016062:Porosity; D011817:Rabbits; D051381:Rats; D012709:Serum Albumin / Q000032:analysis / Q000276:immunology; D017655:Silicon Compounds / Q000737:chemistry*
chemical_list: D000906:Antibodies; D000941:Antigens; D008567:Membranes, Artificial; D015335:Molecular Probes; D012709:Serum Albumin; D017655:Silicon Compounds