Purely electronic diagnostic devices that are sensitive to biomolecules' intrinsic charge present a very attractive platform for point‐of‐care (PoC) applications, since they can operate under label‐free conditions. In this report, a graphene‐based electrolyte‐gated field‐effect transistor is developed as an immunosensor capable of sensitive analyte detection, even in the complex environment of physiological samples. The coimmobilization of an antibody fragment (F(ab′)2) and polyethylene glycol on the graphene surface allows for a highly sensitive and selective detection of a protein analyte, with a limit of detection in the low femtomolar range, both in high ionic strength buffer and undiluted serum. Multiparametric analysis of the device's analyte‐dependent electronic response shows that the mechanism behind this very sensitive detection cannot be explained by a commonly reported electrostatic gating effect. Rather, the observed combination of charge neutrality point shifts and asymmetric mobility changes are attributed to the modulation of scattering by charged impurities, which seem to dominate the device's transfer characteristics. Furthermore, the reproducibility of the normalized signal response obtained from several different devices shows that this graphene‐based immunosensor is capable of direct and quantitative measurements of protein analytes in untreated serum, imperative for diagnostic tools geared toward PoC applications.

Oxysterol species are formed in vivo by enzymatic and non-enzymatic oxidation of cholesterol. Oxysterols were shown not only to be intermediates in the biosynthesis of bile acids and steroid hormones but also to possess versatile bioactivities. Many functions of oxysterols are not fully understood, others may not have been discovered yet, especially those of non-enzymatic origin. The limited accessibility to standard compounds challenges both analytics and functional studies. Here an amperometric flow-through electrochemical (EC) oxidation of cholesterol was applied to generate numerous oxidation products within short reaction times. Besides nine oxysterols confirmed with standard compounds (LC-MS), more than 10 additional, not identified oxidation products were present. The oxidation sites of the identified compounds were in agreement to the expected accessibility of the cholesterol backbone to free radical driven oxidation. Additionally, the presence of three products which are known to be synthesized enzymatically in vivo demonstrated a successful mimicking of these processes by EC as well. Several of the unidentified species showed the same analytical behavior (retention time and MS/MS) as compounds observed in extracts from a cardiomyocyte cell model of nitrosative stress. Further investigation of electrochemically generated compounds will allow identification and characterization of new oxysterols in vivo.Practical applications: Electrochemical oxidation of cholesterol generates numerous oxysterols in short reaction times. The identified products were oxysterols known to be generated in vivo by both free radical and enzymatic processes. Among the unidentified oxidation products were species which showed the same analytical behavior as substances in extracts from stressed cell cultures. Further investigation of EC-generated compounds may facilitate identification and characterization of new in vivo relevant oxysterols and the synthesis of standards for biological and analytical applications.

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Graphene field‐effect transistors are appealing for biosensing applications due to their high charge sensitivity. In article number https://doi.org/10.1002/admt.201800186, Nesha Andoy, Alexey Tarasov, and co‐workers demonstrate label‐free detection of a clinically relevant protein – thyroid‐stimulating hormone – with a femtomolar detection limit in undiluted serum. This highly sensitive and selective detection in complex samples is facilitated by co‐immobilizing antibody fragments and polyethylene glycol on graphene.

A novel VCSEL array combines the high temporal flexibility of a laser source with the full field radiation characteristics of an array and yields a new optical excitation source for active thermography that can merge the two regimes of flash and lock-in thermography. Among others, we investigate the possibility of multiplex photothermics for two-dimensional material characterization, e. g. thickness mapping. Several first test results will be presented that demonstrate possibilities and capabilities of this new optical excitation source and compare it to conventional sources.