An integrated microchannel biosensor platform to analyse low density lactate metabolism in HepG2 cells in vitro

Sensor-integrated brain-on-a-chip platforms: Improving the predictive validity in neurodegenerative research

Affecting millions of individuals worldwide, neurodegenerative diseases (NDDs) pose a significant and growing health concern in people over the age of 60 years. Contributing to this trend are the steady increase in the aging population coupled with a persistent lack of disease-altering treatment strategies targeting NDDs. The absence of efficient therapeutics can be attributed to high failure rates in clinical trials and the ineptness of animal models in preceding preclinical studies. To that end, in recent years, significant research effort has been dedicated to the development of human cell-based preclinical disease models characterized by a higher degree of predictive validity. However, a key requirement of any in vitro model constitutes the precise knowledge and replication of the target tissues' (patho-)physiological microenvironment. Herein, microphysiological systems have demonstrated superiority over conventional static 2D/3D in vitro cell culture systems, as they allow for the emulation and continuous monitoring of the onset, progression, and remission of disease-associated phenotypes. This review provides an overview of recent advances in the field of NDD research using organ-on-a-chip platforms. Specific focus is directed toward non-invasive sensing strategies encompassing electrical, electrochemical, and optical sensors. Additionally, promising on- and integrable off-chip sensing strategies targeting key analytes in NDDs will be presented and discussed in detail.

Cancer Models on Chip: Paving the Way to Large-Scale Trial Applications

Cancer kills millions of individuals every year all over the world (Global Cancer Observatory). The physiological and biomechanical processes underlying the tumor are still poorly understood, hindering researchers from creating new, effective therapies. Inconsistent results of preclinical research, in vivo testing, and clinical trials decrease drug approval rates. 3D tumor-on-a-chip (ToC) models integrate biomaterials, tissue engineering, fabrication of microarchitectures, and sensory and actuation systems in a single device, enabling reliable studies in fundamental oncology and pharmacology. This review includes a critical discussion about their ability to reproduce the tumor microenvironment (TME), the advantages and drawbacks of existing tumor models and architectures, major components and fabrication techniques. The focus is on current materials and micro/nanofabrication techniques used to manufacture reliable and reproducible microfluidic ToC models for large-scale trial applications.

Lactate-Oxidase-Instructed Cancer Diagnosis and Therapy

Lactate oxidase (LOx) has attracted extensive interest in cancer diagnosis and therapy in recent years owing to its specific catalysis on l-lactate; its catalytic process consumes oxygen (O₂ ) and generates a large amount of hydrogen peroxide (H₂ O₂ ) and pyruvate. Given high levels of lactate in tumor tissues and its tight correlation with tumor growth, metastasis, and recurrence, LOx-based biosensors including H₂ O₂ -based, O₂ -based, pH-sensitive, and electrochemical have been designed for cancer diagnosis, and various LOx-based cancer therapy strategies including lactate-depletion-based metabolic cancer therapy/immunotherapy, hypoxia-activated chemotherapy, H₂ O₂ -based chemodynamic therapy, and multimodal synergistic cancer therapy have also been developed. In this review, the lactate-specific catalytic properties of LOx are introduced, and the recent advances on LOx-instructed cancer diagnostic or therapeutic platforms and corresponding biological applications are summarized. Additionally, the challenges and potential of LOx-based nanomedicines are highlighted.

Integrated biosensors for monitoring microphysiological systems

Microphysiological systems (MPSs), also known as organ-on-a-chip models, aim to recapitulate the functional components of human tissues or organs in vitro. Over the last decade, with the advances in biomaterials, 3D bioprinting, and microfluidics, numerous MPSs have emerged with applications to study diseased and healthy tissue models. Various organs have been modeled using MPS technology, such as the heart, liver, lung, and blood-brain barrier. An important aspect of in vitro modeling is the accurate phenotypical and functional characterization of the modeled organ. However, most conventional characterization methods are invasive and destructive and do not allow continuous monitoring of the cells in culture. On the other hand, microfluidic biosensors enable in-line, real-time sensing of target molecules with an excellent limit of detection and in a non-invasive manner, thereby effectively overcoming the limitation of the traditional techniques. Consequently, microfluidic biosensors have been increasingly integrated into MPSs and used for in-line target detection. This review discusses the state-of-the-art microfluidic biosensors by providing specific examples, detailing their main advantages in monitoring MPSs, and highlighting current developments in this field. Finally, we describe the remaining challenges and potential future developments to advance the current state-of-the-art in integrated microfluidic biosensors.

Organic Bioelectronics for In Vitro Systems

Bioelectronics have made strides in improving clinical diagnostics and precision medicine. The potential of bioelectronics for bidirectional interfacing with biology through continuous, label-free monitoring on one side and precise control of biological activity on the other has extended their application scope to in vitro systems. The advent of microfluidics and the considerable advances in reliability and complexity of in vitro models promise to eventually significantly reduce or replace animal studies, currently the gold standard in drug discovery and toxicology testing. Bioelectronics are anticipated to play a major role in this transition offering a much needed technology to push forward the drug discovery paradigm. Organic electronic materials, notably conjugated polymers, having demonstrated technological maturity in fields such as solar cells and light emitting diodes given their outstanding characteristics and versatility in processing, are the obvious route forward for bioelectronics due to their biomimetic nature, among other merits. This review highlights the advances in conjugated polymers for interfacing with biological tissue in vitro, aiming ultimately to develop next generation in vitro systems. We showcase in vitro interfacing across multiple length scales, involving biological models of varying complexity, from cell components to complex 3D cell cultures. The state of the art, the possibilities, and the challenges of conjugated polymers toward clinical translation of in vitro systems are also discussed throughout.

Electrochemical biosensor for glycine detection in biological fluids

We present herein the very first amperometric biosensor for the quantitative determination of glycine in diverse biological fluids. The biosensor is based on a novel quinoprotein that catalyzes the oxidation of glycine with high specificity. This process is coupled to the redox conversion of Prussian blue in the presence of hydrogen peroxide originating from the enzymatic reaction. The optimized tailoring of the biosensor design consists of the effective encapsulation of the quinoprotein in a chitosan matrix with the posterior addition of an outer Nafion layer, which is here demonstrated to suppress matrix interference. This is particularly important in the case of ascorbic acid, which is known to influence the redox behavior of the Prussian blue. The analytical performance of the biosensor demonstrates fast response time (<7 s), acceptable reversibility, reproducibility, and stability (<6% variation) as well as a wide linear range of response (25-500 μM) that covers healthy (and even most unhealthy) physiological levels of glycine in blood/serum, urine and sweat. A total of 6 real samples from healthy patients and animals were analyzed: two serum, two urine and two sweat samples. The results were validated via commercially available fluorescence kit, displaying discrepancy of less than 9% in all the samples. The unique analytical features and effortless preparation of the new glycine biosensor position it at the forefront of current technologies towards decentralized clinical applications and sport performance monitoring.

Review: Cantilever-Based Sensors for High Speed Atomic Force Microscopy

This review critically summarizes the recent advances of the microcantilever-based force sensors for atomic force microscope (AFM) applications. They are one the most common mechanical spring-mass systems and are extremely sensitive to changes in the resonant frequency, thus finding numerous applications especially for molecular sensing. Specifically, we comment on the latest progress in research on the deflection detection systems, fabrication, coating and functionalization of the microcantilevers and their application as bio- and chemical sensors. A trend on the recent breakthroughs on the study of biological samples using high-speed atomic force microscope is also reported in this review.

Single-Use Printed Biosensor for L-Lactate and Its Application in Bioprocess Monitoring

There is a profound need in bioprocess manufacturing for low-cost single-use sensors that allow timely monitoring of critical product and production attributes. One such opportunity is screen-printed enzyme-based electrochemical sensors, which have the potential to enable low-cost online and/or off-line monitoring of specific parameters in bioprocesses. In this study, such a single-use electrochemical biosensor for lactate monitoring is designed and evaluated. Several aspects of its fabrication and use are addressed, including enzyme immobilization, stability, shelf-life and reproducibility. Applicability of the biosensor to off-line monitoring of bioprocesses was shown by testing in two common industrial bioprocesses in which lactate is a critical quality attribute (Corynebacterium fermentation and mammalian Chinese hamster ovary (CHO) cell cultivation). The specific response to lactate of the screen-printed biosensor was characterized by amperometric measurements. The usability of the sensor at typical industrial culture conditions was favorably evaluated and benchmarked with commonly used standard methods (HPLC and enzymatic kits). The single-use biosensor allowed fast and accurate detection of lactate in prediluted culture media used in industrial practice. The design and fabrication of the biosensor could most likely be adapted to several other critical bioprocess analytes using other specific enzymes. This makes this single-use screen-printed biosensor concept a potentially interesting and versatile tool for further applications in bioprocess monitoring.