Blueprints for Biosensors: Design, Limitations, and Applications

Portable Sensing Devices for Detection of COVID-19: A Review

The coronavirus pandemic is the most challenging incident that people have faced in recent years. Despite the time-consuming and expensive conventional methods, point-of-care diagnostics have a crucial role in deterrence, timely detection, and intensive care of the disease's progress. Hence, this detrimental health emergency persuaded researchers to accelerate the development of highly-scalable diagnostic devices to control the propagation of the virus even in the least developed countries. The strategies exploited for detecting COVID-19 stem from the already designed systems for studying other maladies, particularly viral infections. The present report reviews not only the novel advances in portable diagnostic devices for recognizing COVID-19, but also the previously existing biosensors for detecting other viruses. It discusses their adaptability for identifying surface proteins, whole viruses, viral genomes, host antibodies, and other biomarkers in biological samples. The prominence of different types of biosensors such as electrochemical, optical, and electrical for detecting low viral loads have been underlined. Thus, it is anticipated that this review will assist scientists who have embarked on a competition to come up with more efficient and marketable in-situ test kits for identifying the infection even in its incubation time without sample pretreatment. Finally, a conclusion is provided to highlight the importance of such an approach for monitoring people to combat the spread of such contagious diseases.

Macrolide Biosensor Optimization through Cellular Substrate Sequestration

Developing and optimizing small-molecule biosensors is a central goal of synthetic biology. Here we incorporate additional cellular components to improve biosensor sensitivity by preventing target molecules from diffusing out of cells. We demonstrate that trapping erythromycin within Escherichia coli through phosphorylation increases the sensitivity of its biosensor (MphR) by approximately 10-fold. When combined with prior engineering efforts, our optimized biosensor can detect erythromycin concentrations as low as 13 nM. We show that this strategy works with a range of macrolide substrates, enabling the potential usage of our optimized system for drug development and metabolic engineering. This strategy can be extended in future studies to improve the sensitivity of other biosensors. Our findings further suggest that many naturally evolved genes involved in resistance to multiple classes of antibiotics may increase intracellular drug concentrations to modulate their own expression, acting as a form of regulatory feedback.

Transcription factor-based biosensors: a molecular-guided approach for natural product engineering

Natural products and their derivatives offer a rich source of chemical and biological diversity; however, traditional engineering of their biosynthetic pathways to improve yields and access to unnatural derivatives requires a precise understanding of their enzymatic processes. High-throughput screening platforms based on allosteric transcription-factor based biosensors can be leveraged to overcome the screening bottleneck to enable searching through large libraries of pathway/strain variants. Herein, the development and application of engineered allosteric transcription factor-based biosensors is described that enable optimization of precursor availability, product titers, and downstream product tailoring for advancing the natural product bioeconomy. We discuss recent successes for tailoring biosensor design, including computationally-based approaches, and present our future outlook with the integration of cell-free technologies and de novo protein design for rapidly generating biosensor tools.

Sensing the future of bio-informational engineering

The practices of synthetic biology are being integrated into 'multiscale' designs enabling two-way communication across organic and inorganic information substrates in biological, digital and cyber-physical system integrations. Novel applications of 'bio-informational' engineering will arise in environmental monitoring, precision agriculture, precision medicine and next-generation biomanufacturing. Potential developments include sentinel plants for environmental monitoring and autonomous bioreactors that respond to biosensor signaling. As bio-informational understanding progresses, both natural and engineered biological systems will need to be reimagined as cyber-physical architectures. We propose that a multiple length scale taxonomy will assist in rationalizing and enabling this transformative development in engineering biology.

Biosensors-on-Chip: An Up-to-Date Review

Generally, biosensors are designed to translate physical, chemical, or biological events into measurable signals, thus offering qualitative and/or quantitative information regarding the target analytes. While the biosensor field has received considerable scientific interest, integrating this technology with microfluidics could further bring significant improvements in terms of sensitivity and specificity, resolution, automation, throughput, reproducibility, reliability, and accuracy. In this manner, biosensors-on-chip (BoC) could represent the bridging gap between diagnostics in central laboratories and diagnostics at the patient bedside, bringing substantial advancements in point-of-care (PoC) diagnostic applications. In this context, the aim of this manuscript is to provide an up-to-date overview of BoC system development and their most recent application towards the diagnosis of cancer, infectious diseases, and neurodegenerative disorders.

Combinatorial metabolic pathway assembly approaches and toolkits for modular assembly

Synthetic Biology is a rapidly growing interdisciplinary field that is primarily built upon foundational advances in molecular biology combined with engineering design principles such as modularity and interoperability. The field considers living systems as programmable at the genetic level and has been defined by the development of new platform technologies and methodological advances. A key concept driving the field is the Design-Build-Test-Learn cycle which provides a systematic framework for building new biological systems. One major application area for synthetic biology is biosynthetic pathway engineering that requires the modular assembly of different genetic regulatory elements and biosynthetic enzymes. In this review we provide an overview of modular DNA assembly and describe and compare the plethora of in vitro and in vivo assembly methods for combinatorial pathway engineering. Considerations for part design and methods for enzyme balancing are also presented, and we briefly discuss alternatives to intracellular pathway assembly including microbial consortia and cell-free systems for biosynthesis. Finally, we describe computational tools and automation for pathway design and assembly and argue that a deeper understanding of the many different variables of genetic design, pathway regulation and cellular metabolism will allow more predictive pathway design and engineering.

Biosensing based on field-effect transistors (FET): Recent progress and challenges

The use of field-Effect-Transistor (FET) type biosensing arrangements has been highlighted by researchers in the field of early biomarker detection and drug screening. Their non-metalized gate dielectrics that are exposed to an electrolyte solution cover the semiconductor material and actively transduce the biological changes on the surface. The efficiency of these novel devices in detecting different biomolecular analytes in a real-time, highly precise, specific, and label-free manner has been validated by numerous research studies. Considerable progress has been attained in designing FET devices, especially for biomedical diagnosis and cell-based assays in the past few decades. The exceptional electronic properties, compactness, and scalability of these novel tools are very desirable for designing rapid, label-free, and mass detection of biomolecules. With the incorporation of nanotechnology, the performance of biosensors based on FET boosts significantly, particularly, employment of nanomaterials such as graphene, metal nanoparticles, single and multi-walled carbon nanotubes, nanorods, and nanowires. Besides, their commercial availability, and high-quality production on a large-scale, turn them to be one of the most preferred sensing and screening platforms. This review presents the basic structural setup and working principle of different types of FET devices. We also focused on the latest progression regarding the use of FET biosensors for the recognition of viruses such as, recently emerged COVID-19, Influenza, Hepatitis B Virus, protein biomarkers, nucleic acids, bacteria, cells, and various ions. Additionally, an outline of the development of FET sensors for investigations related to drug development and the cellular investigation is also presented. Some technical strategies for enhancing the sensitivity and selectivity of detection in these devices are addressed as well. However, there are still certain challenges which are remained unaddressed concerning the performance and clinical use of transistor-based point-of-care (POC) instruments; accordingly, expectations about their future improvement for biosensing and cellular studies are argued at the end of this review.

Programmable cross-ribosome-binding sites to fine-tune the dynamic range of transcription factor-based biosensor

Currently, predictive translation tuning of regulatory elements to the desired output of transcription factor (TF)-based biosensors remains a challenge. The gene expression of a biosensor system must exhibit appropriate translation intensity, which is controlled by the ribosome-binding site (RBS), to achieve fine-tuning of its dynamic range (i.e. fold change in gene expression between the presence and absence of inducer) by adjusting the translation level of the TF and reporter. However, existing TF-based biosensors generally suffer from unpredictable dynamic range. Here, we elucidated the connections and partial mechanisms between RBS, translation level, protein folding and dynamic range, and presented a design platform that predictably tuned the dynamic range of biosensors based on deep learning of large datasets cross-RBSs (cRBSs). In doing so, a library containing 7053 designed cRBSs was divided into five sub-libraries through fluorescence-activated cell sorting to establish a classification model based on convolutional neural network in deep learning. Finally, the present work exhibited a powerful platform to enable predictable translation tuning of RBS to the dynamic range of biosensors.

Feasibility of on/at Line Methods to Determine Boar Taint and Boar Taint Compounds: An Overview

Simple Summary

Due to welfare issues, the physical castration of male pigs is decreasing, and the entire male pig production is increasing. Fattening entire male pigs requires control due to the possibility of accumulating off odour/flavour called boar taint, which is mainly due to two compounds - skatole and androstenone. If carcasses with boar taint reach the market, it can cause a negative consumer reaction which may have economic consequences for the whole meat chain. Thus, it is necessary to sort out carcasses at the slaughter line. Today, a sensory quality control (human nose method) is used in some slaughter plants for this purpose. Detection by physical or chemical methods is also envisaged. A colorimetric method to determine skatole has been used in Danish abattoirs for decades, but it is foreseen that it will soon be replaced by the laser diode thermal desorption ion source coupled with a mass spectrometry equipment that allows a fully automated classification based on skatole and androstenone levels at speed line, with a delay of less than 40 min. Other potential methods such as the electrochemical biosensors, rapid evaporative ionization mass spectroscopy and Raman spectroscopy, still need further development and validation for an application at abattoir level.

Abstract

Classification of carcasses at the slaughter line allows an optimisation of its processing and differentiated payment to producers. Boar taint is a quality characteristic that is evaluated in some slaughter plants. This odour and flavour is mostly present in entire males and perceived generally by sensitive consumers as unpleasant. In the present work, the methodologies currently used in slaughter plants for boar taint classification (colorimetric method and sensory quality control-human nose) and the methodologies that have the potential to be implemented on/at the slaughter line (mass spectrometry, Raman and biosensors) have been summarized. Their main characteristics are presented and an analysis of strengths, weaknesses, opportunities and threats (SWOT) has been carried out. From this, we can conclude that, apart from human nose, the technology that arises as very promising and available on the market, and that will probably become a substitute for the colorimetric method, is the tandem between the laser diode thermal desorption ion source and the mass spectrometry (LDTD-MS/MS) with automation of the sampling and sample pre-treatment, because it is able to work at the slaughter line, is fast and robust, and measures both androstenone and skatole.

Engineered bacteria to report gut function: technologies and implementation

Advances in synthetic biology and microbiology have enabled the creation of engineered bacteria which can sense and report on intracellular and extracellular signals. When deployed in vivo these whole-cell bacterial biosensors can act as sentinels to monitor biomolecules of interest in human health and disease settings. This is particularly interesting in the context of the gut microbiota, which interacts extensively with the human host throughout time and transit of the gut and can be accessed from feces without requiring invasive collection. Leveraging rational engineering approaches for genetic circuits as well as an expanding catalog of disease-associated biomarkers, bacterial biosensors can act as non-invasive and easy-to-monitor reporters of the gut. Here, we summarize recent engineering approaches applied in vivo in animal models and then highlight promising technologies for designing the next generation of bacterial biosensors.

Two-Component Biosensors: Unveiling the Mechanisms of Predictable Tunability

Many studies have been devoted to the engineering of cellular biosensors by exploiting intrinsic natural sensors. However, biosensors rely not only on input detection but also on an adequate response range. It is therefore often necessary to tune natural systems to meet the demands of specific applications in a predictable manner. In this study, we explored the customizability of two-component bacterial biosensors by modulating the main biosensor component, i.e., the receptor protein. We developed a mathematical model that describes the functional relationship between receptor abundance and activation threshold, sensitivity, dynamic range, and operating range. The defined mathematical framework allows the design of the genetic architecture of a two-component biosensor that can perform as required with minimal genetic engineering. To experimentally validate the model and its predictions, a library of biosensors was constructed. The good agreement between theoretical designs and experimental results indicates that modulation of receptor protein abundance allows optimization of biosensor designs with minimal genetic engineering.

Zwitterionic Polydopamine/Protein G Coating for Antibody Immobilization: Toward Suppression of Nonspecific Binding in Immunoassays

For the development of immunoassays into sophisticated analyte-sensing methods, it is a priority to suppress nonspecific binding in immunoassays. Herein, we report a one-step surface coating method that can not only optimally immobilize antibodies but also suppress nonspecific binding. Zwitterionic dopamine (ZW-DOPA) exhibits distinct antifouling performance, and protein G enables an antibody to have an optimal orientation. A mixture of ZW-DOPA and protein G can be simply coated onto various kinds of surfaces, and the antibody can be immobilized onto the ZW-DOPA/protein G-coated surfaces. The antifouling property of the zwitterionic group, surface-independent coating property of the catechol and amine groups, and antibody-retaining property of protein G synergistically contribute to surface-independent and oriented immobilization of antibodies without nonspecific binding. The surface characteristics of ZW-DOPA/protein G-coated substrates were analyzed by X-ray photoelectron spectroscopy, contact angle goniometry, atomic force microscopy, and ellipsometry. Importantly, the ZW-DOPA/protein G-coated substrates showed high resistance to nonspecific protein adhesion. We also verified that antibodies could be immobilized onto ZW-DOPA/protein G-coated substrates using fluorescence and biolayer interferometry systems. Finally, ZW-DOPA/protein G-coated substrates were employed as immune substrates for influenza virus detection via the naked eye and surface-enhanced Raman scattering, allowing us to efficiently identify the virus. It is anticipated that the developed ZW-DOPA/protein G coating method will be useful for the advancement of immunoassays.

Transporter Engineering for Microbial Manufacturing

Microbes play an important role in biotransformation and biosynthesis of biofuels, natural products, and polymers. Therefore, microbial manufacturing has been widely used in medicine, industry, and agriculture. However, common strategies including enzyme engineering, pathway optimization, and host engineering are generally inadequate to obtain an efficient microbial production system. Transporter engineering provides an alternative strategy to promote the transmembrane transfer of substrates, intermediates, and final products in microbial cells and thus enhances production by alleviating feedback inhibition and cytotoxicity caused by final products. According to the current studies in transport engineering, native transporters usually have low expression and poor transportation ability, resulting in inefficient transport processes and microbial production. In this review, current approaches for transporter mining, characterization, and verification are comprehensively summarized. Practical approaches to enhance the transport system in engineered cells, such as balancing transporter overexpression and cell growth, and evolution of native transporters are discussed. Furthermore, the applications of transporter engineering in microbial manufacturing, including enhancement of substrate utilization, concentration of metabolic flux to the target pathway, and acceleration of efflux and recovery of products, demonstrate its outstanding advantages and promising prospects.

Application of combinatorial optimization strategies in synthetic biology

In the first wave of synthetic biology, genetic elements, combined into simple circuits, are used to control individual cellular functions. In the second wave of synthetic biology, the simple circuits, combined into complex circuits, form systems-level functions. However, efforts to construct complex circuits are often impeded by our limited knowledge of the optimal combination of individual circuits. For example, a fundamental question in most metabolic engineering projects is the optimal level of enzymes for maximizing the output. To address this point, combinatorial optimization approaches have been established, allowing automatic optimization without prior knowledge of the best combination of expression levels of individual genes. This review focuses on current combinatorial optimization methods and emerging technologies facilitating their applications.

Developments of Riboswitches and Toehold Switches for Molecular Detection-Biosensing and Molecular Diagnostics

Riboswitches and toehold switches are considered to have potential for implementation in various fields, i.e., biosensing, metabolic engineering, and molecular diagnostics. The specific binding, programmability, and manipulability of these RNA-based molecules enable their intensive deployments in molecular detection as biosensors for regulating gene expressions, tracking metabolites, or detecting RNA sequences of pathogenic microorganisms. In this review, we will focus on the development of riboswitches and toehold switches in biosensing and molecular diagnostics. This review introduces the operating principles and the notable design features of riboswitches as well as toehold switches. Moreover, we will describe the advances and future directions of riboswitches and toehold switches in biosensing and molecular diagnostics.

Better together: building protein oligomers naturally and by design

Protein oligomers are more common in nature than monomers, with dimers being the most prevalent final structural state observed in known structures. From a biological perspective, this makes sense as it conserves vital molecular resources that may be wasted simply by generating larger single polypeptide units, and allows new features such as cooperativity to emerge. Taking inspiration from nature, protein designers and engineers are now building artificial oligomeric complexes using a variety of approaches to generate new and useful supramolecular protein structures. Oligomerisation is thus offering a new approach to sample structure and function space not accessible through simply tinkering with monomeric proteins.

A new bivalent fluorescent fusion protein for differential Cu(II) and Zn(II) ion detection in aqueous solution

Simple and easy to engineer metal-sensing molecules that are capable of differentiating metal ions and producing metal-specific signals are highly desirable. Metal ions affect the thermal stability of proteins by increasing or decreasing their resistance to unfolding. This work illustrates a new strategy for designing bivalent fluorescent fusion proteins capable of differentiating metal ions in solution through their distinct effects on a protein's thermal stability. A new dual purpose metal sensor was developed consisting of biotin protein ligase (BirA) from B. pseudomallei (Bp) fused to green fluorescent protein (GFP). When coupled with differential scanning fluorimetry of GFP-tagged proteins (DSF-GTP) for signal-transduction detection, Bp BirA-GFP yields distinct protein unfolding signatures with Zn(II) and Cu(II) ions in aqueous solutions. The limit of detection of the system is ∼1 μM for both metal species. The system can be used in a variety of high-throughput assay formats including for the screening of metal-binding proteins and chelators. Bp BirA-GFP has also the additional benefit of being useful in Cu(II) ion field-testing applications through simple visual observation of a temperature-dependent loss of fluorescence. Bp BirA-GFP is the first example of a 2protein-based dual purpose Cu(II) and Zn(II) ion sensor compatible with two different yet complementary signal-transduction detection systems.

Measuring glycolytic flux in single yeast cells with an orthogonal synthetic biosensor

Metabolic heterogeneity between individual cells of a population harbors significant challenges for fundamental and applied research. Identifying metabolic heterogeneity and investigating its emergence require tools to zoom into metabolism of individual cells. While methods exist to measure metabolite levels in single cells, we lack capability to measure metabolic flux, i.e., the ultimate functional output of metabolic activity, on the single-cell level. Here, combining promoter engineering, computational protein design, biochemical methods, proteomics, and metabolomics, we developed a biosensor to measure glycolytic flux in single yeast cells. Therefore, drawing on the robust cell-intrinsic correlation between glycolytic flux and levels of fructose-1,6-bisphosphate (FBP), we transplanted the B. subtilis FBP-binding transcription factor CggR into yeast. With the developed biosensor, we robustly identified cell subpopulations with different FBP levels in mixed cultures, when subjected to flow cytometry and microscopy. Employing microfluidics, we were also able to assess the temporal FBP/glycolytic flux dynamics during the cell cycle. We anticipate that our biosensor will become a valuable tool to identify and study metabolic heterogeneity in cell populations.

Off-Colony Screening of Biosynthetic Libraries by Rapid Laser-Enabled Mass Spectrometry

By leveraging advances in DNA synthesis and molecular cloning techniques, synthetic biology increasingly makes use of large construct libraries to explore large design spaces. For biosynthetic pathway engineering, the ability to screen these libraries for a variety of metabolites of interest is essential. If the metabolite of interest or the metabolic phenotype is not easily measurable, screening soon becomes a major bottleneck involving time-consuming culturing, sample preparation, and extraction. To address this, we demonstrate the use of automated laser-assisted rapid evaporative ionization mass spectrometry (LA-REIMS)-a form of ambient laser desorption ionization mass spectrometry-to perform rapid mass spectrometry analysis direct from agar plate yeast colonies without sample preparation or extraction. We use LA-REIMS to assess production levels of violacein and betulinic acid directly from yeast colonies at a rate of 6 colonies per minute. We then demonstrate the throughput enabled by LA-REIMS by screening over 450 yeast colonies within <4 h, while simultaneously generating recoverable glycerol stocks of each colony in real time. This showcases LA-REIMS as a prescreening tool to complement downstream quantification methods such as liquid chromatography-mass spectroscopy (LCMS). By prescreening several hundred colonies with LA-REIMS, we successfully isolate and verify a strain with a 2.5-fold improvement in betulinic acid production. Finally, we show that LA-REIMS can detect 20 out of a panel of 27 diverse biological molecules, demonstrating the broad applicability of LA-REIMS to metabolite detection. The rapid and automated nature of LA-REIMS makes this a valuable new technology to complement existing screening technologies currently employed in academic and industrial workflows.

Harnessing synthetic biology for kelp forest conservation1

Environmental and climatic change is outpacing the ability of organisms to adapt, at an unprecedented level, resulting in range contractions and global ecosystem shifts to novel states. At the same time, scientific advances continue to accelerate, providing never-before imagined solutions to current and emerging environmental problems. Synthetic biology, the creation of novel and engineered genetic variation, is perhaps the fastest developing and transformative scientific field. Its application to solve extant and emerging environmental problems is vast, at times controversial, and technological advances have outpaced the social, ethical, and practical considerations of its use. Here, we discuss the potential direct and indirect applications of synthetic biology to kelp forest conservation. Rather than advocate or oppose its use, we identify where and when it may play a role in halting or reversing global kelp loss and discuss challenges and identify pathways of research needed to bridge the gap between technological advances and organismal biology and ecology. There is a pressing need for prompt collaboration and dialogue among synthetic biologists, ecologists, and conservationists to identify opportunities for use and ensure that extant research directions are set on trajectories to allow these currently disparate fields to converge toward practical environmental solutions.

Creating an in vivo bifunctional gene expression circuit through an aptamer-based regulatory mechanism for dynamic metabolic engineering in Bacillus subtilis

Aptamer-based regulatory biosensors can dynamically regulate the expression of target genes in response to ligands and could be used in dynamic metabolic engineering for pathway optimization. However, the existing aptamer-ligand biosensors can only function with non-complementary DNA elements that cannot replicate in growing cells. Here, we construct an aptamer-based synthetic regulatory circuit that can dynamically upregulate and downregulate the expression of target genes in response to the ligand thrombin at transcriptional and translational levels, respectively, and further used this system to dynamically engineer the synthesis of 2'-fucosyllactose (2'-FL) in Bacillus subtilis. First, we demonstrated the binding of ligand molecule thrombin with the aptamer can induce the unwinding of fully complementary double-stranded DNA. Based on this finding, we constructed a bifunctional gene expression regulatory circuit using ligand thrombin-bound aptamers. The expression of the reporter gene ranged from 0.084- to 48.1-fold. Finally, by using the bifunctional regulatory circuit, we dynamically upregulated the expression of key genes fkp and futC and downregulated the expression of gene purR, resulting in the significant increase of 2'-FL titer from 24.7 to 674 mg/L. Compared with the other pathway-specific dynamic engineering systems, here the constructed aptamer-based regulatory circuit is independent of pathways, and can be generally used to fine-tune gene expression in other microbes.

Development of a Genetically Encoded Biosensor for Detection of Polyketide Synthase Extender Units in Escherichia coli

The scaffolds of polyketides are constructed via assembly of extender units based on malonyl-CoA and its derivatives that are substituted at the C2-position with diverse chemical functionality. Subsequently, a transcription-factor-based biosensor for malonyl-CoA has proven to be a powerful tool for detecting malonyl-CoA, facilitating the dynamic regulation of malonyl-CoA biosynthesis and guiding high-throughput engineering of malonyl-CoA-dependent processes. Yet, a biosensor for the detection of malonyl-CoA derivatives has yet to be reported, severely restricting the application of high-throughput synthetic biology approaches to engineering extender unit biosynthesis and limiting the ability to dynamically regulate the biosynthesis of polyketide products that are dependent on such α-carboxyacyl-CoAs. Herein, the FapR biosensor was re-engineered and optimized for a range of mCoA concentrations across a panel of E. coli strains. The effector specificity of FapR was probed by cell-free transcription-translation, revealing that a variety of non-native and non-natural acyl-thioesters are FapR effectors. This FapR promiscuity proved sufficient for the detection of the polyketide extender unit methylmalonyl-CoA in E. coli, providing the first reported genetically encoded biosensor for this important metabolite. As such, the previously unknown broad effector promiscuity of FapR provides a platform to develop new tools and approaches that can be leveraged to overcome limitations of pathways that construct diverse α-carboxyacyl-CoAs and those that are dependent on them, including biofuels, antibiotics, anticancer drugs, and other value-added products.

3D biosensors in advanced medical diagnostics of high mortality diseases

Cardiovascular diseases, cancer, and diabetes are high mortality diseases, which account for almost two thirds of all deaths worldwide. Their early detection and continuous evaluation are fundamental for an improved patient prognosis and reduced socioeconomic impact. Current biosensor technologies are typically based on the analysis of whole blood samples from patients for the detection of disease-specific biomarkers. However, these technologies display serious shortcomings, such as reduced sensitivity and dynamic range, limited in vivo applicability, and lack of continuous monitoring. There is the urgent need for new diagnostic and treatment follow-up tools, which allow for the early detection of the pathology as well as for the continuous monitoring of the physiological responses to specific therapies. During the last years, a new generation of biosensor technologies with improved performance has emerged in the biomedical sector. The combination of advanced biomaterial methods, biochemical tools, and micro/nanotechnology approaches has resulted in the development of innovative three-dimensional (3D) biosensor platforms for advanced medical diagnosis. In this review, we report the most recent advances in the field of 3D biosensors for clinical applications, focusing on the diagnosis and monitoring of cardiovascular diseases, cancer, and diabetes. We discuss about their clinical performance compared to standard biosensor technologies, their implantable capability, and their integration into microfluidic devices to develop clinically-relevant models. Overall, we anticipate that 3D biosensors will drive us toward a new paradigm in medical diagnosis, resulting in real-time in vivo biosensors capable to significantly improve patient prognosis.