Will nanobiosensors change therapeutic drug monitoring? The case of methotrexate

Development of epistatic YES and AND protein logic gates and their assembly into signalling cascades

The construction and assembly of artificial allosteric protein switches into information and energy processing networks connected to both biological and non-biological systems is a central goal of synthetic biology and bionanotechnology. However, designing protein switches with the desired input, output and performance parameters is challenging. Here we use a range of reporter proteins to demonstrate that their chimeras with duplicated receptor domains produce YES gate protein switches with large (up to 9,000-fold) dynamic ranges and fast (minutes) response rates. In such switches, the epistatic interactions between largely independent synthetic allosteric sites result in an OFF state with minimal background noise. We used YES gate protein switches based on β-lactamase to develop quantitative biosensors of therapeutic drugs and protein biomarkers. Furthermore, we demonstrated the reconfiguration of YES gate switches into AND gate switches controlled by two different inputs, and their assembly into signalling networks regulated at multiple nodes.

Real-Time, Seconds-Resolved Measurements of Plasma Methotrexate In Situ in the Living Body

Dose-limiting toxicity and significant patient-to-patient pharmacokinetic variability often render it difficult to achieve the safe and effective dosing of drugs. This is further compounded by the slow, cumbersome nature of the analytical methods used to monitor patient-specific pharmacokinetics, which inevitably rely on blood draws followed by post-facto laboratory analysis. Motivated by the pressing need for improved "therapeutic drug monitoring", we are developing electrochemical aptamer-based (EAB) sensors, a minimally invasive biosensor architecture that can provide real-time, seconds-resolved measurements of drug levels in situ in the living body. A key advantage of EAB sensors is that they are generalizable to the detection of a wide range of therapeutic agents because they are independent of the chemical or enzymatic reactivity of their targets. Three of the four therapeutic drug classes that have, to date, been shown measurable using in vivo EAB sensors, however, bind to nucleic acids as part of their mode of action, leaving open questions regarding the extent to which the approach can be generalized to therapeutics that do not. Here, we demonstrate real-time, in vivo measurements of plasma methotrexate, an antimetabolite (a mode of action not reliant on DNA binding) chemotherapeutic, following human-relevant dosing in a live rat animal model. By providing hundreds of drug concentration values, the resulting seconds-resolved measurements succeed in defining key pharmacokinetic parameters, including the drug's elimination rate, peak plasma concentration, and exposure (area under the curve), with unprecedented 5 to 10% precision. With this level of precision, we easily identify significant (>2-fold) differences in drug exposure occurring between even healthy rats given the same mass-adjusted methotrexate dose. By providing a real-time, seconds-resolved window into methotrexate pharmacokinetics, such measurements can be used to precisely "individualize" the dosing of this significantly toxic yet vitally important chemotherapeutic.

The present and the future of protein biosensor engineering

Protein biosensors play increasingly important roles in cell and neurobiology and have the potential to revolutionise the way clinical and industrial analytics are performed. The gradual transition from multicomponent biosensors to fully integrated single chain allosteric biosensors has brought the field closer to commercial applications. We evaluate various approaches for converting constitutively active protein reporter domains into analyte operated switches. We discuss the paucity of the natural receptors that undergo conformational changes sufficiently large to control the activity of allosteric reporter domains. This problem can be overcome by constructing artificial versions of such receptors. The design path to such receptors involves the construction of Chemically Induced Dimerisation systems (CIDs) that can be configured to operate single and two-component biosensors.

Creation of a Nanobody-Based Fluorescent Immunosensor Mini Q-body for Rapid Signal-On Detection of Small Hapten Methotrexate

"Quenchbody (Q-body)" is a quench-based fluorescent biosensor labeled with a fluorescent dye near the antigen-binding site of an antibody. Q-bodies can detect a range of target molecules quickly by simply mixing with a sample. However, the development of Q-bodies using V_HH-nanobodies derived from camelid heavy-chain antibodies has not been reported despite their favorable characteristics. Here, we report a "mini Q-body" that can detect the chemotherapy agent methotrexate (MTX) by using anti-MTX nanobody. Three kinds of constructs each encoding an N-terminal Cys-tag and anti-MTX VHH gene with a different length of linker (GGGS)_n (n = 0, 2, and 4) between them were prepared followed by the expression in Escherichia coli and labeling with several dye maleimides. When the fluorescence intensities in the presence of varied MTX concentrations were measured, TAMRA-labeled nanobodies showed a higher response than ATTO520- or R6G-labeled ones. Especially, TAMRA C6-labeled mini Q-body with no linker showed the highest response of ∼6-fold and a low detection limit of 0.56 nM. When each Trp residue in the mini Q-body was mutated to address the quenching mechanism, the major role of Trp34 at CDR1 in quenching was revealed. Furthermore, the mini Q-body could detect MTX in 50% human serum with a low detection limit of 1.72 nM, showing its applicability to therapeutic drug monitoring. This study is expected to become the basis of the construction of highly responsive mini Q-bodies for sensitive detection of many molecules from small haptens to larger proteins, which will lead to broader applications such as point-of-care tests.

Gold Nanoparticle-Based Platforms for Diagnosis and Treatment of Myocardial Infarction

In recent years, an increasing rate of mortality due to myocardial infarction (MI) has led to the development of nanobased platforms, especially gold nanoparticles (AuNPs), as promising nanomaterials for diagnosis and treatment of MI. These promising NPs have been used to develop different nanobiosensors, mainly optical sensors for early detection of biomarkers as well as biomimetic/bioinspired platforms for cardiac tissue engineering (CTE). Therefore, in this Review, we presented an overview on the potential application of AuNPs as optical (surface plasmon resonance, colorimetric, fluorescence, and chemiluminescence) nanobiosensors for early diagnosis and prognosis of MI. On the other hand, we discussed the potential application of AuNPs either alone or with other NPs/polymers as promising three-dimensional (3D) scaffolds to regulate the microenvironment and mimic the morphological and electrical features of cardiac cells for potential application in CTE. Furthermore, we presented the challenges and ongoing efforts associated with the application of AuNPs in the diagnosis and treatment of MI. In conclusion, this Review may provide outstanding information regarding the development of AuNP-based technology as a promising platform for current MI treatment approaches.

Optical Biosensors for Therapeutic Drug Monitoring

Therapeutic drug monitoring (TDM) is a fundamental tool when administering drugs that have a limited dosage or high toxicity, which could endanger the lives of patients. To carry out this monitoring, one can use different biological fluids, including blood, plasma, serum, and urine, among others. The help of specialized methodologies for TDM will allow for the pharmacodynamic and pharmacokinetic analysis of drugs and help adjust the dose before or during their administration. Techniques that are more versatile and label free for the rapid quantification of drugs employ biosensors, devices that consist of one element for biological recognition coupled to a signal transducer. Among biosensors are those of the optical biosensor type, which have been used for the quantification of different molecules of clinical interest, such as antibiotics, anticonvulsants, anti-cancer drugs, and heart failure. This review presents an overview of TDM at the global level considering various aspects and clinical applications. In addition, we review the contributions of optical biosensors to TDM.

Remotely Triggered Nano-Theranostics For Cancer Applications

Nanotechnology has enabled the development of smart theranostic platforms that can concurrently diagnose disease, start primary treatment, monitor response, and, if required, initiate secondary treatments. Recent in vivo experiments demonstrate the promise of using theranostics in the clinic. In this paper, we review the use of remotely triggered theranostic nanoparticles for cancer applications, focusing heavily on advances in the past five years. Remote triggering mechanisms covered include photodynamic, photothermal, phototriggered chemotherapeutic release, ultrasound, electro-thermal, magneto-thermal, X-ray, and radiofrequency therapies. Each section includes a brief overview of the triggering mechanism and summarizes the variety of nanoparticles employed in each method. Emphasis in each category is placed on nano-theranostics with in vivo success. Some of the nanotheranostic platforms highlighted include photoactivatable multi-inhibitor nanoliposomes, plasmonic nanobubbles, reduced graphene oxide-iron oxide nanoparticles, photoswitching nanoparticles, multispectral optoacoustic tomography using indocyanine green, low temperature sensitive liposomes, and receptor-targeted iron oxide nanoparticles loaded with gemcitabine. The studies reviewed here provide strong evidence that the field of nanotheranostics is rapidly evolving. Such nanoplatforms may soon enable unique advances in the clinical management of cancer. However, reproducibility in the synthesis procedures of such "smart" platforms that lend themselves to easy scale-up in their manufacturing, as well as the development of new and improved models of cancer that are more predictive of human responses, need to happen soon for this field to make a rapid clinical impact.

Naked-eye nanobiosensor for therapeutic drug monitoring of methotrexate

Sensing of methotrexate at clinically-relevant concentrations was achieved with a plasmon-coupling assay.

Biosensors and nanobiosensors for therapeutic drug and response monitoring

Review of different biosensors and nanobiosensors increasingly used in therapeutic drug monitoring (TDM) for pharmaceutical drugs with dosage limitations or toxicity issues and for therapeutic response monitoring.