Vuslat B. Juska

Continuous biomarker monitoring is revolutionizing chronic disease management, with glucose monitoring for diabetes as the primary example. Given the success of this approach, a transition to continuous protein monitoring (CPM, a real-time, implantable or wearable technology) could similarly advance precision medicine. In this work, we review state-of-the-art CPM platforms and their prospective clinical impact across both chronic disorders—metabolic, cardiovascular, autoimmune, and neurodegenerative—and acute crises, such as sepsis and transplant dysfunction. We also highlight remaining barriers to widespread adoption, including sensor stability, robust machine learning models for live interpretation, and responsible data handling for patient privacy. With continued engineering and clinical validation, emerging biosensor technologies could transform disease management, facilitating earlier interventions and individualizing treatment strategies, ultimately improving patient outcomes.

Affinity based electrochemical biosensing systems with integrated miniaturized interfaces has enabled key advancement toward rapid, sensitive, precise and deployable detection platforms. Translation of the biosensing tools for routine monitoring of dairy cows’ functional welfare through non‐invasive methods may have implications for identifying welfare compromise and improving welfare on‐farm. The goal is to develop an on‐chip voltammetric device to evaluate measures of inflammation and stress in biofluids of dairy cows, that is, milk. The straightforward fabrication of highly reproducible silicon devices designed is demonstrated for an electrochemical interface, using an efficient scale‐up process for batch manufacturing of sensitive multiplexed sensor arrays. Lift‐off and passivation lithography are used subsequently to construct the electroactive arrays with excellent reproducibility allowing micro and nano‐scale patterning. Then the non‐specific binding challenge is addressed via a rapid formation of a biocompatible antibiofouling coating onto porous gold surfaces on a single chip – simultaneously – in approximately two minutes. The developed coating provides flexibility in the experimental design due to abundant functional groups (‐COOH and –NH₂). The coating is combined with glutaraldehyde cross‐linked Protein A/G to achieve a universal matrix for Anti‐Immunoglobulin G (IgG)‐based biosensing and validate by the attainment of two sensors of cortisol and haptoglobin by using milk samples.

The development of compact biosensing devices capable of sensitive and selective concomitant detection of two or more analytes in a single sample has enormous potential for point-of-care and -use applications. Silicon microfabrication technologies outperform other fabrication processes in terms of reproducibility, miniaturization capability, and design adjustability. In this work, we present a novel miniaturized fully integrated multiplexed silicon-based sensing platform for rapid and label-free detection of milk and egg allergens in water. After modifying the microelectrodes with gold nanostructures and chitosan-gold nanocomposite hydrogel layer, we compared random covalent binding with boronic acid-assisted oriented strategy for antibody immobilization to the surface. The Boronic affinity-based approach exhibited a high reproducible and reliable immuno-response towards casein as a major milk allergen. The stepwise surface modifications characterized using various analytical techniques, confirming the successful attachment of antibodies to the surface. We then successfully adapted the biosensor surface for ovalbumin detection, an egg allergen, demonstrating multiplexed allergen detection and universal immobilization strategy for any IgG type antibodies, opening a wide range of potential applications in portable immunosensing for various target analytes beyond food allergens.

Affinity based electrochemical biosensing systems with integrated miniaturised interfaces has enabled key advancement toward rapid, sensitive, precise and deployable detection platforms. Manufacturing silicon micro/nano devices for biology interface has been a highly promising platform to design and develop electrochemical sensors for the detection of very low concentrations of the target molecules. However, the biofouling challenge of the biosensors when the surface is exposed to a complex matrix such as blood, serum, milk, has been a road blocker. Here we introduce a simple, rapid formation of an anti-biofouling coating onto several electroactive surface areas present on a single chip simultaneously. Using such a multiplexed surface, we were able to investigate the optimum working conditions on-chip. Concentrating on two individual bioassay platforms for stress biomarkers, haptoglobin and cortisol, we demonstrate the broad applicability of the developed universal platform with excellent performance in bovine serum and correlation with conventional ELISA using milk samples.

Advances in multiplexed sensing on a single chip device offer a range of advantages for the development of new biosensing platforms. The increasing number of reports on multiplexed sensing demonstrates the reliability and attractiveness of merging several closely packed sensing areas. However, the most important starting point for this emerging technology is being able to reproducibly manufacture chips with high yield. Microfabrication is arguably the most elegant approach to develop chips with ultra micro and nano scaled sensing electrodes that have the highest reproducibility and design flexibility. With this approach, it is possible to manufacture devices at very small scales with any arrangement of the components on a single chip. Such devices are not only outstanding for sensing applications but also for building interfaces for electrochemistry with very high reproducibility at the micro and nanoscale, so called micro/nanoarchitectures. Here we show one route for a successful fabrication protocol of ultra-micro scaled sensing electrode chips. We demonstrate the effectiveness of alkaline and acidic treatments in terms of cleaning and reproducibility of electrochemical sensing on chip and on wafer. The alkaline treatment protocol established for these particular microfabricated chips will aid the development of highly reproducible biosensors. Herein, we clearly demonstrate the intimate link between the microfabrication and engineering micro-interfaces for high performance sensing tools in the fields of chemical and biological applications.

Electrochemical Impedance Spectroscopy (EIS) is a surface sensitive technique which examines the impedance of an electrochemical cell over a range of frequencies. By immobilising an antigen or antibody to the electrode surface, EIS shows potential for highly specific and sensitive immunosensor performance. Following an introduction into antibodies and EIS, this review presents immobilisation techniques for an immunosensor’s bioreceptor. It highlights electrode modifications such as self-assembled monolayers (SAMs), polymers and nanostructures for anchoring the bioreceptor to the surface. Stable immobilisation directly to these modifications is not always possible. Immobilisation techniques to these modified surfaces are explored including cross-linking and controlled orientation. EIS allows for label-free detection by monitoring the change in charge-transfer resistance or capacitance caused by changes in the electrode surface. Label-free immunosensors are the focus of this paper as they show potential for point-of-care (POC) devices.

BACKGROUND: Carbon‐based nanostructures have been attracting major interest in many research fields, including chemical and biological sensing, because of their unique structural dimensions and excellent physical, chemical and mechanical properties. A recently developed laser scribing approach allows design and fabrication of flexible, graphitic carbon‐based substrates for (bio‐)electrochemical applications, as it provides highly robust and low‐cost sensing platforms.RESULTS: Here we demonstrate the fabrication of a highly reproducible laser‐scribed graphitic electrode (LSE) on a polyimide (Kapton) film using a simple, do‐it‐yourself laser engraving system equipped with a 405 nm wavelength laser. Copper nanostructures were deposited onto an electrode surface via the electrodeposition process. The developed three‐dimensional graphitic electrodes modified by nano copper/copper oxide species (LSE‐Cu) were used for the detection of dopamine and glucose. Electrochemical studies of LSE‐Cu showed that in the presence of nano‐copper there is an apparent shift of the oxidation peaks of dopamine and ascorbic acid, allowing determination of dopamine without an interference effect, with an excellent sensitivity of 1321.54 μA L mmol⁻¹ cm⁻². Furthermore, the LSE‐Cu sensor exhibited highly satisfying analytical performance towards glucose electro‐oxidation, with a reproducibility of 5.47% (RSD %).CONCLUSION: We have demonstrated a simple design, fabrication and passivation route for the preparation of LSEs performing as biosensors. Such a cost‐effective and design‐flexible system is highly suitable for developing a biosensing platform towards various target analytes and further miniaturization of the electrode. © 2020 Society of Chemical Industry