“Clickable” Organic Electrochemical Transistors

Abstract

Interfacing the surface of an organic semiconductor with biological elements is a central quest when it comes to the development of efficient organic bioelectronic devices. Here, we present the first example of “clickable” organic electrochemical transistors (OECTs). The synthesis and characterization of an azide-derivatized EDOT monomer (azidomethyl-EDOT, EDOT-N3) are reported, as well as its deposition on Au-interdigitated electrodes through electropolymerization to yield PEDOT-N3-OECTs. The electropolymerization protocol allows for a straightforward and reliable tuning of the characteristics of the OECTs, yielding transistors with lower threshold voltages than PEDOT-based state-of-the-art devices and maximum transconductance voltage values close to 0 V, a key feature for the development of efficient organic bioelectronic devices. Subsequently, the azide moieties are employed to click alkyne-bearing molecules such as redox probes and biorecognition elements. The clicking of an alkyne-modified PEG4-biotin allows for the use of the avidin–biotin interactions to efficiently generate bioconstructs with proteins and enzymes. In addition, a dibenzocyclooctyne-modified thrombin-specific HD22 aptamer is clicked on the PEDOT-N3-OECTs, showing the application of the devices toward the development of organic transistors-based biosensors. Finally, the clicked OECTs preserve their electronic features after the different clicking procedures, demonstrating the stability and robustness of the fabricated transistors.

Interface Engineering of “Clickable” Organic Electrochemical Transistors toward Biosensing Devices

“…The electropolymerization curves show that the deposition of the film takes place successfully, showing similar features as those previously reported for the deposition of PEDOT-N 3 on different substrates (Figure 1B). 23,35 In addition, CV measurements show that the deposition of the PEDOT-N 3 layer originates a significant change in the response of the conducting polymer electrodes (Figures 1C and S3), shifting from the typical capacitive-like behavior of PEDOT-based electrodes to a more resistive character. 11,46 This result can be ascribed to the lower conductivity of the azido-bearing polymer compared to that of PEDOT:TOS, in agreement with previously reported results.…”

“…The observed redox potential is higher than that obtained for the clicking of E-Fc while employing DMSO as a solvent (0.51 V). 23 This effect could be attributed to a hindered charge transport from the redox probes throughout the film and to the contact electrodes since they are supposed to be located closer to the surface of the OECTs when the clicking process is performed in EtOH/ H 2 O. 51,52 In this sense, the DMSO-induced swelling allows the clicking of the Fc molecules also inside the film and, therefore, closer to the Au electrodes, facilitating the electron hopping mechanism through a shorter distance and diminishing the effective potential at which the redox couple is observed.…”

“…Finally, we compared the performance of the developed interfacial sensing architecture with that formerly reported also based on "clickable" OECTs (Figure 6A). 23 Very recently, PEDOT-N 3 OECT-based biosensing devices were fabricated by clicking a DBCO-bearing HD22 aptamer (DBCO-HD22) via SPAAC to azido-bearing organic transistors. To the best of our knowledge, this is the only previous report on OECTbased biosensors for thrombin detection (while other FETbased biosensing devices have also been developed during the last years for the monitoring of thrombin, and a comparison is presented in Table S4 of the Supporting Information).…”

“…2-Azidomethyl-2,3-dihydro-thieno[3,4b] [1,4]dioxine (EDOT-N 3 ) was synthesized according to a recently reported protocol. 19,23 Briefly, sodium azide was added to a solution of 2-chloromethyl-2,3-dihydro-thieno [3,4-b][1,4]dioxine (EDOT-Cl) in absolute DMF. The reaction mixture was heated to 120 °C for 3 h. After cooling, water was added to the reaction mixture, and the product was extracted with diethyl ether.…”

“…8,22 In this regard, we have recently reported the T h i s c o n t e n t i s fabrication of PEDOT-N 3 -based OECTs, endowing the incorporation of recognition units such as biotin and aptamers to the surface. 23 On the other hand, click chemistry involves a group of orthogonal, selective, and high-yield reactions which can be performed at room temperature and in aqueous solvents, and whose relevance was recognized by the 2022 Chemistry Nobel Prize. 24,25 These reactions endow the efficient and straightforward fabrication of bio-constructs, being particularly relevant for bioconjugation and labeling purposes.…”