Roozbeh Siavash Moakhar

Melatonin is a clinically relevant biomarker for diagnosing circadian rhythm sleep disorders (CRSDs) and monitoring circadian disruption associated with cancer, metabolic and cardiovascular disease, and psychiatric disorders. This work reports the implementation of an electrochemical aptamer‐based biosensor (E‐aptasensor) for direct reagentless detection of melatonin within physiological levels. The E‐aptasensor employs an optimized surface population of the aptamers in a conformational change‐based assay to detect melatonin over a broad dynamic range, including the picomolar physiological range. The behavior of the aptameric assay was validated both in bulk solution and in silico using fluorescence resonance energy transfer (FRET) and molecular docking (MD). The E‐aptasensor achieves sensitive and selective melatonin detection, with a limit of detection (LOD) of 0.75 pM and strong specificity against a panel of relevant interferents. Fitting the electrochemical responses to the Hill–Langmuir (HL) binding model yielded an apparent electrochemical dissociation constant (K _{d, app} ) of 37 pM. Notably, the E‐aptasensor showed promising performance in unextracted human plasma, avoiding the extraction step typically required for immunoassays. These features support future development of rapid melatonin profiling for CRSD diagnosis and monitoring, as well as future point‐of‐care implementation. The single‐step E‐aptasensor offers a promising, faster, and simpler complement to gold‐standard techniques.

Electron-accepting chain reactions play crucial roles in diagnostics for bacterial infections, from nucleic acid amplification for bacterial identification to metabolic assays for phenotypic antibiotic susceptibility testing. When coupled with redox mediators, these reactions can be interrogated using an electroanalytical method. We demonstrate kinetic acceleration of loop-mediated isothermal amplification–based identification and resazurin-based phenotypic antibiotic susceptibility profiling through enhanced electromagnetic fields and modulated hot electron injection at the multilayered plasmonic metasurface-fluidic interface. We systematically investigate rounded versus sharp-apex plasmonic architectures, quantifying near-field magnitude and decay to identify geometries that maximize kinetic amplification under electrochemical readout. This approach is further combined with machine learning–assisted Gaussian fitting to improve data quantification and interpretation. Across diverse bacterial species, we achieved rapid identification with no cross-reactivity and phenotypic antibiotic susceptibility testing without overnight culture. In a prospective pilot clinical study of urine specimens directly from patients with suspected urinary tract infections, we observe high accuracy and strong essential and categorical agreement with standard clinical microbiology assays for bacterial identification and antibiotic susceptibility testing.

Antimicrobial susceptibility testing (AST) technologies that rapidly identify pathogenic bacteria and their resistance phenotypes are critical in addressing the antimicrobial resistance crisis, enabling timely and precise antibiotic treatment decisions. We present a modular automated platform based on nanoplasmonic colorimetry in microfluidics for parallel bacterial identification and phenotypic profiling of AST (QolorPhAST), achieving an eightfold enhancement in detection rapidity. QolorPhAST reduces drug susceptibility profiling times in direct specimens from days to minutes, bypassing overnight cultures and pathogen isolation typically required in standard clinical AST workflows. The approach was validated with a broad range of microbial pathogens, spanning 10 bacterial species and 34 strains across various antibiotic concentrations to identify pathogens and antibiotic minimal inhibitory concentrations in a multiplexed fashion. In a proof-of-concept clinical study, QolorPhAST was tested with a cohort of blinded patient samples suspected of urinary tract infections, achieving 100% accuracy in species identification, an average categorical agreement of 91.81% and an average essential agreement of 86.4%, with a turnaround time of 36 min from specimen introduction to result. The study suggests that QolorPhAST, with its ease of use and cost-effectiveness, can be a transformative solution to address the antimicrobial resistance burden.

Reagentless molecular-imprinted polymer (MIP) electrochemical biosensors can offer the next generation of biosensing platforms for the detection of biomarkers owing to their simplicity, cost-efficacy, tunability, robustness, and accuracy. In this work, a novel combination of Prussian blue (PB), coated as an embedded redox probe on a gold working electrode (GWE), and a signal-off MIP assay has been proposed in an electrochemical format for the detection of troponin I (TnI) in biofluids. TnI is a variant exclusive to heart muscles, and its elevated level in the bloodstream is indicative of acute myocardial infarction (AMI). The proposed lab-manufactured PB/MIP electrochemical biosensor, consisting of a simple signal-off MIP assay and a PB redox probe embedded on the GWE surface, is the first of its kind that allows for reagentless, label-free, and single-step electrochemical biosensing of proteins. The preparation steps of the biosensor were fully characterized by cyclic voltammetry (CV), atomic force microscopy (AFM), and Raman spectroscopy. Finally, the performance of the optimized biosensor was investigated through the determination of various concentrations of TnI, ranging from 10 to 100 pg mL⁻¹ within 5 min, in serum and plasma with limits of detection less than 3.6 pg mL⁻¹, and evaluation of selectivity towards TnI using some relevant proteins that exist in biofluids with higher concentrations.

Portable sample-to-answer devices with applications in point-of-care settings have emerged to obviate the necessity of centralized laboratories for biomarker analysis. In this work, a smartphone-operated and additively manufactured multiplexed electrochemical device (AMMED) is presented for the portable detection of biomarkers in blood and saliva. AMMED is comprised of a customized portable potentiostat with a multiplexing feature, a 3D-printed sample collection cartridge to handle three samples of saliva and blood at the same time, a smartphone application to remotely control the potentiostat, and a 3D-printed-based multiplexed microfluidic electrochemical biosensor (test chip). Here, by employing additive manufacturing techniques, a simple, cleanroom-free, and scalable approach was proposed for the fabrication of the test chip. Moreover, these techniques can bring about easy integration of AMMED components. Additionally, the test chip can be compatible with different affinity-based bioassays which can be implemented in a multiplexed manner for detection. The AMMED components were successfully characterized in terms of electrochemical and fluidic performance. Particularly, to demonstrate the biosensing capabilities of the device, the spike protein of the SARS-CoV-2 omicron variant and a well-established aptameric assay were selected as the representative biomarker and the bioassay, respectively. The proposed device accurately and selectively detected the target of interest in a rapid (5 min) and multiplex manner with a dynamic detection range of 1–10 000 pg ml⁻¹ in different media, and the clinical feasibility was assessed by several saliva patient samples. AMMED offers a versatile sample-to-answer platform that can be used for the detection of various biomarkers present in biofluids.

Deployment of nucleic acid amplification assays for diagnosing pathogens in point-of-care settings is a challenge due to lengthy preparatory steps. We present a molecular diagnostic platform that integrates a fabless plasmonic nano-surface into an autonomous microfluidic cartridge. The plasmonic ‘hot’ electron injection in confined space yields a ninefold kinetic acceleration of RNA/DNA amplification at single nucleotide resolution by one-step isothermal loop-mediated and rolling circle amplification reactions. Sequential flow actuation with nanoplasmonic accelerated microfluidic colorimetry and in conjugation with machine learning-assisted analysis (using our ‘QolorEX’ device) offers an automated diagnostic platform for multiplexed amplification. The versatility of QolorEX is demonstrated by detecting respiratory viruses: SARS-CoV-2 and its variants at the single nucleotide polymorphism level, H1N1 influenza A, and bacteria. For COVID-19 saliva samples, with an accuracy of 95% on par with quantitative polymerase chain reaction and a sample-to-answer time of 13 minutes, QolorEX is expected to advance the monitoring and rapid diagnosis of pathogens.

In this review, we highlight the most recent advances in the nucleic acid detection of viruses, bacteria, fungi, and protozoa in a portable fashion using colorimetric-based microfluidic devices.

A nanostructured microfluidic device, featuring a series of self-organized gold nanocavities, enhanced with graphene nanosheets, for ultrasensitive, quantitative, and plasmon-assisted electrochemical detection of H₂O₂ released from cancer cells.

The cost‐effective, robust, and efficient electrocatalysts for photoelectrochemical (PEC) water‐splitting has been extensively studied over the past decade to address a solution for the energy crisis. The interesting physicochemical properties of CuO have introduced this promising photocathodic material among the few photocatalysts with a narrow bandgap. This photocatalyst has a high activity for the PEC hydrogen evolution reaction (HER) under simulated sunlight irradiation. Here, the recent advancements of CuO‐based photoelectrodes, including undoped CuO, doped CuO, and CuO composites, in the PEC water‐splitting field, are comprehensively studied. Moreover, the synthesis methods, characterization, and fundamental factors of each classification are discussed in detail. Apart from the exclusive characteristics of CuO‐based photoelectrodes, the PEC properties of CuO/2D materials, as groups of the growing nanocomposites in photocurrent‐generating devices, are discussed in separate sections. Regarding the particular attention paid to the CuO heterostructure photocathodes, the PEC water splitting application is reviewed and the properties of each group such as electronic structures, defects, bandgap, and hierarchical structures are critically assessed.