Printable graphene BioFETs for DNA quantification in Lab-on-PCB microsystems

Lab-on-Chip is a technology that aims to transform the Point-of-Care (PoC) diagnostics field; nonetheless a commercial production compatible technology isyet to be established. Lab-on-Printed Circuit Board (Lab-on-PCB) is currentlyconsidered as a promising candidate technology for cost-aware butsimultaneously high specification applications, requiring multi-componentmicrosystem implementations, due to its inherent compatibility with electronicsand the long-standing industrial manufacturing basis. In this work, wedemonstrate the first electrolyte gated field-effect transistor (FET) DNAbiosensor implemented on commercially fabricated PCB in a planar layout.Graphene ink was drop-casted to form the transistor channel and PNA probeswere immobilized on the graphene channel, enabling label-free DNA detection. Itis shown that the sensor can selectively detect the complementary DNAsequence, following a fully inkjet-printing compatible manufacturing process. The results demonstrate the potential for the effortless integration of FET sensorsinto Lab-on-PCB diagnostic platforms, paving the way for even higher sensitivityquantification than the current Lab-on-PCB state-of-the-art of passive electrodeelectrochemical sensing. The substitution of such biosensors with our presentedFET structures, promises further reduction of the time-to-result in microsystemscombining sequential DNA amplification and detection modules to few minutes,since much fewer amplification cycles are required even for low-abundancenucleic acid targets

Ultra stable, inkjet-printed pseudo reference electrodes for lab-on-chip integrated electrochemical biosensors

Lab-on-Chip technology comprises one of the most promising technologies enabling the widespread adoption of Point-of-Care testing in routine clinical practice. However, until now advances in Lab-on-Chip have not been translated to the anticipated degree to commercialized tools, with integrated device mass manufacturing cost still not at a competitive level for several key clinical applications. Lab-on-PCB is currently considered as a candidate technology addressing this issue, owing to its intuitive compatibility with electronics, seamless integration of electrochemical biosensors and the extensive experience regarding industrial manufacturing processes. Inkjet-printing in particular is a compatible fabrication method, widening the range of electronic materials available and thus enabling seamlessly integrated ultrasensitive electronic detection. To this end, in this work stable pseudo-reference electrodes are fabricated for the first time by means of commercial inkjet-printing on a PCB-integrated electrochemical biosensing platform. SEM and XPS analysis are employed to characterize the electrodes' structure and composition and identify any special characteristics, compared to published work on alternative substrates. Additionally, this paper analyzes integrated reference electrodes from a new perspective, focusing mainly on their characteristics in real-life operation: chemical sintering as opposed to high budget thermal one, stability under continuous flow, pH dependency and bias stress effects on electrode instability, a parameter often overlooked in electrochemical biosensors

Investigation of the H₂O sensing mechanism of DC operated chemiresistors based on graphene oxide and thermally reduced graphene oxide

Graphene oxide (GO) is a promising material for H 2O vapour sensing. However, the H 2O sensing mechanisms are still under investigation especially in the case of thermally reduced GO. To this purpose, planar devices were fabricated by spin-coating graphene oxide on glass substrates. Ultra high response to H 2O was recorded but poor repeatability and stability over time were also noted. Three different degrees of thermal reduction were applied to improve material stability. An inverse change of resistance was observed for reduced graphene oxide compared to pure graphene oxide upon interaction with H 2O. The sensing mechanisms that govern GO and reduced GO behavior were studied based on DC measurements. In the case of GO, strong ionic conductivity was proposed whereas in the case of reduced GO mixed electronic/ionic with the leading mechanism affected by H 2O percentage in air, degree of material reduction, and sensor working temperature. Finally, it was found that by promoting one sensing mechanism over the other, improved operating humidity range of the sensor can be achieved. </p

Microfluidic devices for label-free DNA detection

Sensitive and specific DNA biomarker detection is critical for accurately diagnosing a broad range of clinical conditions. However, the incorporation of such biosensing structures in integrated microfluidic devices is often complicated by the need for an additional labelling step to be implemented on the device. In this review we focused on presenting recent advances in label-free DNA biosensor technology, with a particular focus on microfluidic integrated devices. The key biosensing approaches miniaturized in flow-cell structures were presented, followed by more sophisticated microfluidic devices and higher integration examples in the literature. The option of full DNA sequencing on microfluidic chips via nanopore technology was highlighted, along with current developments in the commercialization of microfluidic, label-free DNA detection devices

LoCKAmp: lab-on-PCB technology for <3 minute virus genetic detection

The recent COVID-19 outbreak highlighted the need for lab-on-chip diagnostic technology fit for real-life deployment in the field. Existing bottlenecks in multistep analytical microsystem integration and upscalable, standardized fabrication techniques delayed the large-scale deployment of lab-on-chip solutions during the outbreak, throughout a global diagnostic test shortage. This study presents a technology that has the potential to address these issues by redeploying and repurposing the ubiquitous printed circuit board (PCB) technology and manufacturing infrastructure. We demonstrate the first commercially manufactured, miniaturised lab-on-PCB device for loop-mediated isothermal amplification (LAMP) genetic detection of SARS-CoV-2. The system incorporates a mass-manufactured, continuous-flow PCB chip with ultra-low cost fluorescent detection circuitry, rendering it the only continuous-flow μLAMP platform with off-the-shelf optical detection components. Ultrafast, SARS-CoV-2 RNA amplification in wastewater samples was demonstrated within 2 min analysis, at concentrations as low as 17 gc μL−1. We further demonstrate our device operation by detecting SARS-CoV-2 in 20 human nasopharyngeal swab samples, without the need for any RNA extraction or purification. This renders the presented miniaturised nucleic-acid amplification-based diagnostic test the fastest reported SARS-CoV-2 genetic detection platform, in a practical implementation suitable for deployment in the field. This technology can be readily extended to the detection of alternative pathogens or genetic targets for a very broad range of applications and matrices. LoCKAmp lab-on-PCB chips are currently mass-manufactured in a commercial, ISO-compliant PCB factory, at a small-scale production cost of £2.50 per chip. Thus, with this work, we demonstrate a high technology-readiness-level lab-on-chip-based genetic detection system, successfully benchmarked against standard analytical techniques both for wastewater and nasopharyngeal swab SARS-CoV-2 detection