Organic Semiconductor Laser Platform for the Detection of DNA by AgNP Plasmonic Enhancement

Abstract

Organic semiconductor lasers are a sensitive biosensing platform that respond to specific biomolecule binding events. So far, such biosensors have utilized protein-based interactions for surface functionalization but a nucleic acid-based strategy would considerably widen their utility as a general biodiagnostic platform. This manuscript reports two important advances for DNA-based sensing using an organic semiconductor (OS) distributed feedback (DFB) laser. First, the immobilization of alkyne-tagged 12/18-mer oligodeoxyribonucleotide (ODN) probes by Cu-catalyzed azide alkyne cycloaddition (CuAAC) or "click-chemistry" onto an 80 nm thick OS laser film modified with an azide-presenting polyelectrolyte monolayer is presented. Second, sequence-selective binding to these immobilized probes with complementary ODN-functionalized silver nanoparticles, is detected. As binding occurs, the nanoparticles increase the optical losses of the laser mode through plasmonic scattering and absorption, and this causes a rise in the threshold pump energy required for laser action that is proportional to the analyte concentration. By monitoring this threshold, detection of the complementary ODN target down to 11.5 pM is achieved. This complementary binding on the laser surface is independently confirmed through surface-enhanced Raman spectroscopy (SERS).

Star-shaped oligofluorene truxene macromolecules – synthesis and properties as a function of alkyl chain length

“…The analysis was comparable with that from the literature. 64 General procedure D: Deprotection of the trimethylsilane group of (bromooligofluorenyl)trimethylsilanes (8) 41 To a solution of (bromooligofluorenyl)trimethylsilane (TMS-Fn-Br) (1 eq) in dichloromethane (16 mL per gram), CF3COOH (15 eq) was added and the mixture stirred at room temperature for 2 h. Basic work up was carried out with water (2 times), saturated NaHCO3 solution (2 times) and final washing with water. The organic fraction was dried over anhydrous MgSO4 and filtered through a silica plug to remove polar by-products and crystallized from acetone to yield the product.…”

“…The organic fraction was dried over anhydrous MgSO4 and filtered through a silica plug to remove polar by-products and crystallized from acetone to yield the product. 7-Bromo-9,9,9',9',9'',9'',9''',9'''-octaoctyl-2,2':7',2'':7''',2'''-quaterfluorene (8) Using the general procedure D, the quantities used were: (7'''-bromo-9,9,9',9',9'',9'',9''',9'''-octaoctyl-2,2':7',2'':7'',2'''-quaterfluoren-7-yl)trimethylsilane (7 O) (2.96 g, 1.74•10 -3 mol), dichloromethane (56 mL), CF3COOH (1.8 mL). The product was obtained as a white crystalline solid (2.74 g, 1.68•10 -3 mol, 96%).…”

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Star-shaped oligofluorene truxenes are very promising materials and have demonstrated excellent properties as the gain medium in organic semiconductor lasers (OSLs). [1][2][3][4][5][6][7][8][9][10] Alkyl chains in oligofluorene truxenes act as solubilizing groups as well as spacers to prevent intermolecular π-π stacking that leads to quenching of the light emission. A new series of star-shaped systems analogous to hexyl oligofluorene truxenes 11 with alkyl chains of different lengths (butyl chains and octyl chains) was synthesized.

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Biological Lasers for Biomedical Applications

“…Strictly speaking, the above two DFB laser examples do not fall into the biolaser definition, as they act merely like passive label‐free optical biosensors. Very recently, McConnel et al developed a sequence‐selective detection of analytes (oligodeoxyribonucleotide, ODN) using a hybrid DNA/organic laser in conjunction with Ag nanoparticles . As binding occurs, the nanoparticles increase the optical losses of the laser mode through plasmonic scattering and absorption, which in turn results in an increased lasing threshold.…”

“…In the past decade, dyes, quantum dots, quantum wells, nanowires, rare‐earth materials, fluorescent proteins, fluorescent product resulting from enzyme–substrate reaction, and other naturally fluorescent biomaterials have been used to participate actively in lasing action . Biolasers have been employed in the detection of various bioactivities at the molecular, cellular, and tissue levels . Recently, their applications in cell tracking, labeling/probes, implantable devices, cell/tissue imaging start to emerge.…”