In this review, we provide an overview of conjugated organic semiconductors and their applications in biological sensing with a primary focus on the role of the organic semiconductor.

Many indicator displacement assays can detect biological analytes in water, but these often have reduced performance in the presence of an unavoidable component: NaCl. We report here a new self-assembled sensor, DimerDye, that uses a novel photochemical guest-sensing mechanism and that is intrinsically tolerant of cosolutes. We synthetically integrated a dye into a calixarene macrocycle, forming two new merocyanine calixarenes (MCx-1 and MCx-2). Both compounds self-assemble into nonemissive dimers in water. The addition of good guests like trimethyllysine induces a turn-on fluorescence response of MCx-1 due to simultaneous dimer dissociation and formation of an emissive host-guest complex. DimerDyes remain functional in solutions containing the various salts, metal ions, and cofactors that are needed for enzymatic reactions. MCx-1 provides a real-time, turn-on fluorescence signal in response to the lysine methyltransferase reaction of PRDM9.

dominated by poly (3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) and closely related derivatives as the active material, [4][5][6][7] new semiconducting materials have started to enter the arena in recent years. [8][9][10][11][12] In particular, hole-transporting (p-type) mixed conductors have emerged with properties on par or even better than benchmark PEDOT:PSS formulations, [9,13,14] whereas electron-transporting (n-type) materials are still lacking considerably in terms of mixed conduction performance. [15][16][17][18][19] The design of semiconducting materials for bioelectronic applications is heavily influenced by the rich body of literature in the broader field of organic electronics, evidenced by the development of, for example, oligo-and polythiophenes, [8,11,20,21] fullerenes, [18] diketopyrrolopyrrole-, [12,[22][23][24] and naphthalene-diimide-based [15,16] systems as efficient OMIECs. With that in mind, another versatile and highly efficient charge-transporting moiety, isoindigo (IG), has received very little attention for bioelectronic applications. [25] The IG motif depicted in Figure 1a can be structurally modified not only by introducing various solubilizing Organic mixed ionic and electronic conductors are of significant interest for bioelectronic applications. Here, three different isoindigoid building blocks are used to obtain polymeric mixed conductors with vastly different structural and electronic properties which can be further fine-tuned through the choice of comonomer unit. This work shows how careful design of the isoindigoid scaffold can afford highly planar polymer structures with high degrees of electronic delocalization, while subtle structural modifications can control the dominant charge carrier (hole or electron) when probed in organic electrochemical transistors. A combination of experimental and computational techniques is employed to probe electrochemical, structural, and mixed ionic and electronic properties of the polymer series which in turn allows the derivation of important structure-property relations for this promising class of materials in the context of organic bioelectronics. Ultimately, these findings are used to outline robust molecular-design strategies for isoindigo-based mixed conductors that can support efficient p-type, n-type, and ambipolar transistor operation in an aqueous environment.

Figure1.(a) Tr ipeptides found by Wennemers and co-workers.( b) Dipeptides designed based on pyranoid sugar e-a nd z-amino acids.

Herein, we introduce and demonstrate how carbohydrates can be used as conformational control units of organocatalysts to tune their catalytic properties. New hybrid dipeptide-like organocatalysts based on ζ-sugar aminoacids and proline were prepared and tested for the asymmetric Michael addition of aldehydes to βnitrostyrenes. Taking full advantage of the modular nature of the carbohydrate motif, both reactivity and stereoselectivity were significantly improved. By simple structural changes, such as the elimination of the methoxy group in the C4 position of the tetrahydropyran ring, we obtained two complementary catalysts that allow access to both enantiomers of the g-nitroaldehydes with excellent yields, diastereoselectivity, and enantiomeric excesses between 97 and 99%, using a catalytic load even below 1 mol%.