Chemiluminescence and Bioluminescence Imaging for Biosensing and Therapy: In Vitro and In Vivo Perspectives

Pathological biopsy strategy by regulating intracellular ROS to precisely differentiate cancer cells from diseased tissues

We have developed an innovative pathological biopsy strategy by expanding the differences of ROS levels among cancer cells, inflammatory cells and normal cells using cross-linked lipoic acid vesicles loaded with vitamin C (VC@cLAVs), combined with chemiluminescence imaging technology. By analyzing the different trends of intracellular chemiluminescence intensity, the three types of cells were quickly and accurately differentiated from diseased tissues, thus holding clinical tumor diagnostic potential.

Recent Advances of Aminopeptidases-Responsive Small-Molecular Probes for Bioimaging

Aminopeptidases, enzymes with critical roles in human body, are emerging as vital biomarkers for metabolic processes and diseases. Aberrant aminopeptidase levels are often associated with diseases, particularly cancer. Small-molecule probes, such as fluorescent, fluorescent/photoacoustics, bioluminescent, and chemiluminescent probes, are essential tools in the study of aminopeptidases-related diseases. The fluorescent probes provide real-time insights into protein activities, offering high sensitivity in specific locations, and precise spatiotemporal results. Additionally, photoacoustic probes offer signals that are able to penetrate deeper tissues. Bioluminescent and chemiluminescent probes can enhance in vivo imaging abilities by reducing the background. This comprehensive review is focused on small-molecule probes that respond to four key aminopeptidases: aminopeptidase N, leucine aminopeptidase, Pyroglutamate aminopeptidase 1, and Prolyl Aminopeptidase, and their utilization in imaging tumors and afflicted regions. In this review, the design strategy of small-molecule probes, the variety of designs from previous studies, and the opportunities of future bioimaging applications are discussed, serving as a roadmap for future research, sparking innovations in aminopeptidase-responsive probe development, and enhancing our understanding of these enzymes in disease diagnostics and treatment.

Mechanistic Insights into the Bacterial Luciferase-based Bioluminescence Resonance Energy Transfer Luminescence: The Role of Protein Complex Dimer

Bacterial bioluminescence holds significant potential in the realm of optical imaging due to the inherent advantages of bioluminescence and ease of operation. However, its practical utility is hindered by its low light intensity. The fusion of bacterial luciferase with a highly fluorescent protein has been demonstrated to significantly enhance autonomous luminescence. Nevertheless, the underlying mechanism behind this enhancement remains unclear, and there is a dearth of research investigating the mechanistic aspects of bioluminescence resonance energy transfer (BRET) luminescence, whether it occurs naturally or can be achieved through experimental means. In this study, we investigated the phenomenon of bacterial luciferase-based BRET luminescence employing a range of computational techniques, including structural modeling, molecular docking, molecular dynamics simulations, as well as combined quantum mechanics and molecular mechanics calculations. The theoretical findings suggest that the BRET luminescence occurs through resonance energy transfer between the excited bioluminophore and the ground chromophore within the protein complex dimer. The proposed mechanism of the protein complex dimer offers a microscopic understanding of the intriguing BRET phenomenon and has the potential to inspire further practical applications in the field of optical imaging.

Application of CRISPR/Cas13a-based biosensors in serum marker detection

The detection of serum markers is important for the early diagnosis and monitoring of diseases, but conventional detection methods have the problem of low specificity or sensitivity. CRISPR/Cas13a-based biosensors have the characteristics of simple detection methods and high sensitivity, which have a certain potential to solve the problems of conventional detection. This paper focuses on the research progress of CRISPR/Cas13a-based biosensors in serum marker detection, introduces the principles and applications of fluorescence, electrochemistry, colorimetric, and other biosensors based on CRISPR/Cas13a in the detection of serum markers, compares and analyzes the differences between the above CRISPR/Cas13a-based biosensors, and looks forward to the future development direction of CRISPR/Cas13a-based biosensors.

Determination of Nitric Oxide and Its Metabolites in Biological Tissues Using Ozone-Based Chemiluminescence Detection: A State-of-the-Art Review

Ozone-based chemiluminescence detection (CLD) has been widely applied for determining nitric oxide (•NO) and its derived species in many different fields, such as environmental monitoring and biomedical research. In humans and animals, CLD has been applied to determine exhaled •NO and •NO metabolites in plasma and tissues. The main advantages of CLD are high sensitivity and selectivity for quantitative analysis in a wide dynamic range. Combining CLD with analytical separation techniques like chromatography allows for the analytes to be quantified with less disturbance from matrix components or impurities. Sampling techniques like microdialysis and flow injection analysis may be coupled to CLD with the possibility of real-time monitoring of •NO. However, details and precautions in experimental practice need to be addressed and clarified to avoid wrong estimations. Therefore, using CLD as a detection tool requires a deep understanding of the sample preparation procedure and chemical reactions used for liberating •NO from its derived species. In this review, we discuss the advantages and pitfalls of CLD for determining •NO species, list the different applications and combinations with other analytical techniques, and provide general practical notes for sample preparation. These guidelines are designed to assist researchers in comprehending CLD data and in selecting the most appropriate method for measuring •NO species.

Recent Advances in the Development of Non-Invasive Imaging Probes for Cancer Immunotherapy

The last two decades have witnessed a major revolution in the field of tumor immunology including clinical progress using various immunotherapy strategies. These advances have highlighted the potential for approaches that harness the power of the immune system to fight against cancer. While cancer immunotherapies have shown significant clinical successes, patient responses vary widely due to the complex and heterogeneous nature of tumors and immune responses, calling for reliable biomarkers and therapeutic strategies to maximize the benefits of immunotherapy. Especially, stratifying responding individuals from non-responders during the early stages of treatment could help avoid long-term damage and tailor personalized treatments. In efforts to develop non-invasive means for accurately evaluating and predicting tumor response to immunotherapy, multiple affinity-based agents targeting immune cell markers and checkpoint molecules have been developed and advanced to clinical trials. In addition, researchers have recently turned their attention to substrate and activity-based imaging probes that can provide real-time, functional assessment of immune response to treatment. Here, we highlight some of those recently designed probes that image functional proteases as biomarkers of cancer immunotherapy with a focus on their chemical design and detection modalities and discuss challenges and opportunities for the development of imaging tools utilized in cancer immunotherapy.

Internal Light Sources-Mediated Photodynamic Therapy Nanoplatforms: Hope for the Resolution of the Traditional Penetration Problem

Photodynamic therapy (PDT) is an alternative cancer treatment technique with a noninvasive nature, high selectivity, and minimal adverse effects. The indispensable light source used in PDT is a critical factor in determining the energy conversion of photosensitizers (PSs). Traditional light sources are primarily concentrated in the visible light region, severely limiting their penetration depth and making them prone to scattering and absorption when applied to biological tissues. For that reason, its efficacy in treating deep-seated lesions is often inadequate. Self-exciting PDT, also known as auto-PDT (APDT), is an attractive option for circumventing the limited penetration depth of traditional PDT and has acquired significant attention. APDT employs depth-independent internal light sources to excite PSs through resonance or radiative energy transfer. APDT has considerable potential for treating deep-tissue malignancies. To facilitate many researchers' comprehension of the latest research progress in this field and inspire the emergence of more novel research results. This review introduces internal light generation mechanisms and characteristics and provides an overview of current research progress based on the recently reported APDT nanoplatforms. The current challenges and possible solutions of APDT nanoplatforms are also presented and provide insights for future research in the final section of this article.

In vivo three-dimensional brain imaging with chemiluminescence probes in Alzheimer's disease models

Optical three-dimensional (3D) molecular imaging is highly desirable for providing precise distribution of the target-of-interest in disease models. However, such 3D imaging is still far from wide applications in biomedical research; 3D brain optical molecular imaging, in particular, has rarely been reported. In this report, we designed chemiluminescence probes with high quantum yields, relatively long emission wavelengths, and high signal-to-noise ratios to fulfill the requirements for 3D brain imaging in vivo. With assistance from density-function theory (DFT) computation, we designed ADLumin-Xs by locking up the rotation of the double bond via fusing the furan ring to the phenyl ring. Our results showed that ADLumin-5 had a high quantum yield of chemiluminescence and could bind to amyloid beta (Aβ). Remarkably, ADLumin-5's radiance intensity in brain areas could reach 4 × 107 photon/s/cm2/sr, which is probably 100-fold higher than most chemiluminescence probes for in vivo imaging. Because of its strong emission, we demonstrated that ADLumin-5 could be used for in vivo 3D brain imaging in transgenic mouse models of Alzheimer's disease.

Recombinase Polymerase Amplification-Based Biosensors for Rapid Zoonoses Screening

Recent, outbreaks of new emergency zoonotic diseases have prompted an urgent need to develop fast, accurate, and portable screening assays for pathogen infections. Recombinase polymerase amplification (RPA) is sensitive and specific and can be conducted at a constant low temperature with a short response time, making it especially suitable for on-site screening and making it a powerful tool for preventing or controlling the spread of zoonoses. This review summarizes the design principles of RPA-based biosensors as well as various signal output or readout technologies involved in fluorescence detection, lateral flow assays, enzymatic catalytic reactions, spectroscopic techniques, electrochemical techniques, chemiluminescence, nanopore sequencing technologies, microfluidic digital RPA, and clustered regularly interspaced short palindromic repeats/CRISPR-associated systems. The current status and prospects of the application of RPA-based biosensors in zoonoses screening are highlighted. RPA-based biosensors demonstrate the advantages of rapid response, easy-to-read result output, and easy implementation for on-site detection, enabling development toward greater portability, automation, and miniaturization. Although there are still problems such as high cost with unstable signal output, RPA-based biosensors are increasingly becoming one of the most important means of on-site pathogen screening in complex samples involving environmental, water, food, animal, and human samples for controlling the spread of zoonotic diseases.

Emission Onset Time-Adjustable Chemiluminescent Gold Nanoparticles with Ultrastrong Emission for Smartphone-Based Immunoassay of Severe Acute Respiratory Syndrome Coronavirus 2 Antigen

Recently, our group reported a chemical timer approach to manipulate the onset time of chemiluminescence (CL) emission. However, it is still in the proof-of-concept stage, and its analytical applications have not been explored yet. Nanomaterials have merits of good catalytic effect, large specific surface area, good biocompatibility, and ease of self-assembly, which are ideal for constructing analytical-interfaces for bioassays. Herein, an emission onset time-adjustable chemiluminescent L012-Au/Mn2+ was synthesized for the first time by modifying Mn2+ on the surface of L012-protected gold nanoparticle. By using H2O2 and NaHCO3 as coreactants, L012-Au/Mn2+ could not only generate an ultrastrong and long-time CL emission but also its CL emission onset time could be adjusted by the addition of thiourea, which could effectively eliminate interference from the addition of coreactants, shorten the exposure time, reduce the detection background, and finally achieve high sensitivity CL imaging analysis. On this basis, a label-free CL immunoassay was constructed with a smartphone-based imaging system for high-throughput and sensitive determination of severe acute respiratory syndrome coronavirus 2 nucleocapsid (N) protein. The CL image of the immunoassay with different concentrations of N proteins was captured in one photograph 100 s after the injection of H2O2 with a short exposure time of 0.5 s. The immunoassay showed good linearity over the concentration range of 1 pg/mL to 10 ng/mL with a detection limit of 0.13 pg/mL, which was much lower than the reported CCD imaging detection method. In addition, it showed good selectivity and stability and was successfully applied in serum samples from healthy individuals and COVID-19 rehabilitation patients.

Nucleic acid aptamer-based biosensors and their application in thrombin analysis

Thrombin is a multifunctional serine protease that plays an important role in coagulation and anticoagulation processes. Aptamers have been widely applied in biosensors due to their high specificity, low cost and good biocompatibility. This review summarizes recent advances in thrombin quantification using aptamer-based biosensors. The primary focus is optical sensors and electrochemical sensors, along with their applications in thrombin analysis and disease diagnosis.

Ratiometric optical probes for biosensing

Biosensing by optical probes is bringing about a revolution in our understanding of physiological and pathological states. Conventional optical probes for biosensing are prone to inaccurate detection results due to various analyte-independent factors that can lead to fluctuations in the absolute signal intensity. Ratiometric optical probes provide built-in self-calibration signal correction for more sensitive and reliable detection. Probes specifically developed for ratiometric optical detection have been shown to significantly improve the sensitivity and accuracy of biosensing. In this review, we focus on the advancements and sensing mechanism of ratiometric optical probes including photoacoustic (PA) probes, fluorescence (FL) probes, bioluminescence (BL) probes, chemiluminescence (CL) probes and afterglow probes. The versatile design strategies of these ratiometric optical probes are discussed along with a broad range of applications for biosensing such as sensing of pH, enzymes, reactive oxygen species (ROS), reactive nitrogen species (RNS), glutathione (GSH), metal ions, gas molecules and hypoxia factors, as well as the fluorescence resonance energy transfer (FRET)-based ratiometric probes for immunoassay biosensing. Finally, challenges and perspectives are discussed.

Chemiluminescent polymeric nanoprobes for tumor diagnosis: A mini review

Chemiluminescence (CL), a distinct luminescent process by taking advantage of chemical reactions rather than external light source, has recently attracted considerable research interests due to its high sensitivity and low background signal. The sensitivity and specificity of chemiluminescent signals in complex tumor microenvironment provide a sound basis for accurate detection of tumors. Various chemiluminescent nanoprobes with superior performance have been obtained by structural modification of chemiluminescent units or introduction of fluorescent dyes. In this review, we focused on the recent progress of chemiluminescent polymeric systems based on various chromophore substrates, including luminol, peroxyoxalates, 1, 2-dioxetanes and their derivatives for tumor detecting. And we also emphasized the design strategies, mechanisms and diagnostic applications of representative chemiluminescent polymeric nanoprobes. Finally, the critical challenges and perspectives of chemiluminescent systems usage in tumor diagnosis were also discussed.

Polymeric Nanoreactors with Chemically Tunable Redox Responsivity

Bioresponsive nanomaterials are increasingly important in a variety of applications such as disease imaging, drug delivery, and tissue engineering. However, it remains a big challenge to manipulate response efficacy of such materials for performance optimization in a highly complex milieu in vivo. Here, we developed chemically adjustable nanoreactors (CANs) with the structure of polymeric cores and albumin shells to achieve tunable redox responsivity. In vitro characterization demonstrates stable, spherical nanoparticles of the CANs with a particle size of about 50 nm. The fluorescence activation ratios of the CANs are determined by various albumin modification densities on the shell. Meanwhile, the response sensitivity of the CANs to GSH levels (0.6-4 mM) can be tuned by acid-base properties of polymeric blocks in the core. This unique tunable redox responsivity enables the CANs suitable for probe optimization in cancer imaging both in vivo and at histological levels. Overall, this study offers a new design strategy for manipulation on performance of core/shell nanoreactors or bioresponsive nanomaterials.

Small-Molecules as Chemiluminescent Probes to Detect Lipase Activity

The set-up of highly sensitive detection tools to evaluate lipase activity remains a central goal in different fields. In this context, we proposed new chemiluminescent 1,2-dioxetane luminophores, sharing an octanoyl triggerable group, to monitor lipase activity. We herein report the synthesis and both the evaluation of their luminescence emission profile and their enzyme-substrate specificity, generated by three different commercial lipases (Candida cylindracea, Pseudomonas fluorescens, and Mucor miehei) and one esterase (porcine liver esterase, PLE, as a literature control). Remarkably, the present study confirmed the applicability of these 1,2-dioxetane luminophores as (i) highly efficient, broad-range, chemiluminescent probes for the detection and the enzymatic activity evaluation of lipases and as (ii) promising candidates for the future development of both flash- and glow-type luminescence assays.

Recent advances in nanomaterials-based optical sensors for detection of various biomarkers (inorganic species, organic and biomolecules)

This review briefly emphasizes the different detection approaches (electrochemical sensors, chemiluminescence, surface-enhanced Raman scattering), functional nanostructure materials (quantum dots, metal nanoparticles, metal nanoclusters, magnetic nanomaterials, metal oxide nanoparticles, polymer-based nanomaterials, and carbonaceous nanomaterials) and detection mechanisms. Further, this review emphasis on the integration of functional nanomaterials with optical spectroscopic techniques for the identification of various biomarkers (nucleic acids, glucose, uric acid, oxytocin, dopamine, ascorbic acid, bilirubin, spermine, serotonin, thiocyanate, Pb²⁺ , Cu²⁺ , Hg²⁺ , F^- , peptides, and cancer biomarkers (mucin 1, prostate specific antigen, carcinoembryonic antigen, CA15-3, human epidermal growth factor receptor 2, C-reactive protein, and interleukin-6). Analytical characteristics of nanomaterials-based optical sensors are summarized in Tables, providing the insights of nanomaterials-based optical sensors for biomarkers detection. Finally, the opportunities and challenges of nanomaterials-based optical analytical approaches for the detection of various biomarkers (inorganic, organic, biomolecules, peptides and proteins) are discussed.

Analyses of chemiluminescence reactions of fluorophore-linked 1,2-dioxetane isomers in crystals heating at elevated temperature including a development of a simultaneous measurement method of thermal diffusivity and light emission for a single crystal

It has been found that a fluorophore-linked adamantylideneadamantane 1,2-dioxetane derivative showed an isomeric difference in the reactivities of crystalline-state chemiluminescence (CL) under isothermal heating conditions, while there are still unsolved problems on the conditions for intracrystalline reactions. To confirm the suitable heating conditions for initiating crystalline-state CL reactions of the isomers, the CL reactions in their crystal samples heated at elevated temperature were investigated with monitoring of CL light emission and thermogravimetry-differential thermal analysis (TG-DTA) measurements together with a simultaneous measurement method of thermal diffusivity and light emission, to provide the information on suitable temperature range for the crystalline-state CL reactions and on the reactivities depending on open and closed conditions of the crystal samples. The newly developed simultaneous measurement method provides a methodology for a single crystal to analyze the relationship between a change of the thermophysical property of inside of the crystal and the progress of a crystalline-state CL reaction.

Cationic AIEgen micelle-improved chemiluminescent H2O2 assay by integrating reactant approach and CRET

The enhancement of chemiluminescence (CL) intensity is significant in the development of chemiluminescent detection systems with improved sensitivity. In this study, a cationic surfactant with an intrinsic aggregation-induced emission emitter (AIEgen) has been applied to boost the CL signal of the horseradish peroxidase-luminol-H₂O₂ system. The formed cationic AIEgen micelles enhance the CL signal in two ways: the electrostatic attraction-mediated enrichment and approach of reactants and the high CRET efficiency between excited luminol radicals and AIEgen in the surfactant backbone. As a result, strong CL intensity is produced. Rapid and sensitive H₂O₂ detection is realized through the proposed cationic AIEgen micelle-containing chemiluminescent system with a limit of detection of 100 nM. The favourable selectivity over other possible interferents including metal ions and anions is due to the specific chemical reaction. Practical H₂O₂ analysis of thawing water samples with high accuracy using the proposed chemiluminescent platform is realized and is consistent with standard methods.

Early diagnosis of breast cancer lung metastasis by nanoprobe-based luminescence imaging of the pre-metastatic niche

Background

Early detection of breast cancer lung metastasis remains highly challenging, due to few metastatic cancer cells at an early stage. Herein we propose a new strategy for early diagnosis of lung metastasis of breast cancer by luminescence imaging of pulmonary neutrophil infiltration via self-illuminating nanoprobes.

Methods

Luminescent nanoparticles (LAD NPs) were engineered using a biocompatible, neutrophil-responsive self-illuminating cyclodextrin material and an aggregation-induced emission agent. The chemiluminescence resonance energy transfer (CRET) effect and luminescence properties of LAD NPs were fully characterized. Using mouse peritoneal neutrophils, in vitro luminescence properties of LAD NPs were thoroughly examined. In vivo luminescence imaging and correlation analyses were performed in mice inoculated with 4T1 cancer cells. Moreover, an active targeting nanoprobe was developed by surface decoration of LAD NPs with a neutrophil-targeting peptide, which was also systemically evaluated by in vitro and in vivo studies.

Results

LAD NPs can generate long-wavelength and persistent luminescence due to the CRET effect. In a mouse model of 4T1 breast cancer lung metastasis, we found desirable correlation between neutrophils and tumor cells in the lungs, demonstrating the effectiveness of early imaging of the pre-metastatic niche by the newly developed LAD NPs. The active targeting nanoprobe showed further enhanced luminescence imaging capability for early detection of pulmonary metastasis. Notably, the targeting nanoprobe-based luminescence imaging strategy remarkably outperformed PET/CT imaging modalities in the examined mouse model. Also, preliminary tests demonstrated good safety of LAD NPs.

Conclusions

The neutrophil-targeting imaging strategy based on newly developed luminescence nanoparticles can serve as a promising modality for early diagnosis of lung metastasis of breast cancers.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-022-01346-4.

Peptide probes for proteases - innovations and applications for monitoring proteolytic activity

Proteases are excellent biomarkers for a variety of diseases, offer multiple opportunities for diagnostic applications and are valuable targets for therapy. From a chemistry-based perspective this review discusses and critiques the most recent advances in the field of substrate-based probes for the detection and analysis of proteolytic activity both in vitro and in vivo.

Advances in the DNA Nanotechnology for the Cancer Biomarkers Analysis: Attributes and Applications

The most commonly used clinical methods are enzyme-linked immunosorbent assay (ELISA) and quantitative PCR (qPCR) in which ELISA was applied for the detection of protein biomarkers and qPCR was especially applied for nucleic acid biomarker analysis. Although these constructed methods have been applied in wide range, they also showed some inherent shortcomings such as low sensitivity, large sample volume and complex operations. At present, many methods have been successfully constructed on the basis of DNA nanotechnology with the merits of high accuracy, rapid and simple operation for cancer biomarkers assay. In this review, we summarized the bioassay strategies based on DNA nanotechnology from the perspective of the analytical attributes for the first time and discussed and the feasibility of the reported strategies for clinical application in the future.

Direct and Indirect Chemiluminescence: Reactions, Mechanisms and Challenges

Emission of light by matter can occur through a variety of mechanisms. When it results from an electronically excited state of a species produced by a chemical reaction, it is called chemiluminescence (CL). The phenomenon can take place both in natural and artificial chemical systems and it has been utilized in a variety of applications. In this review, we aim to revisit some of the latest CL applications based on direct and indirect production modes. The characteristics of the chemical reactions and the underpinning CL mechanisms are thoroughly discussed in view of studies from the very recent bibliography. Different methodologies aiming at higher CL efficiencies are summarized and presented in detail, including CL type and scaffolds used in each study. The CL role in the development of efficient therapeutic platforms is also discussed in relation to the Reactive Oxygen Species (ROS) and singlet oxygen (1O2) produced, as final products. Moreover, recent research results from our team are included regarding the behavior of commonly used photosensitizers upon chemical activation under CL conditions. The CL prospects in imaging, biomimetic organic and radical chemistry, and therapeutics are critically presented in respect to the persisting challenges and limitations of the existing strategies to date.

Molecular Probes for Autofluorescence-Free Optical Imaging

Optical imaging is an indispensable tool in clinical diagnostics and fundamental biomedical research. Autofluorescence-free optical imaging, which eliminates real-time optical excitation to minimize background noise, enables clear visualization of biological architecture and physiopathological events deep within living subjects. Molecular probes especially developed for autofluorescence-free optical imaging have been proven to remarkably improve the imaging sensitivity, penetration depth, target specificity, and multiplexing capability. In this Review, we focus on the advancements of autofluorescence-free molecular probes through the lens of particular molecular or photophysical mechanisms that produce long-lasting luminescence after the cessation of light excitation. The versatile design strategies of these molecular probes are discussed along with a broad range of biological applications. Finally, challenges and perspectives are discussed to further advance the next-generation autofluorescence-free molecular probes for in vivo imaging and in vitro biosensors.

The Cutting Edge of Disease Modeling: Synergy of Induced Pluripotent Stem Cell Technology and Genetically Encoded Biosensors

The development of cell models of human diseases based on induced pluripotent stem cells (iPSCs) and a cell therapy approach based on differentiated iPSC derivatives has provided a powerful stimulus in modern biomedical research development. Moreover, it led to the creation of personalized regenerative medicine. Due to this, in the last decade, the pathological mechanisms of many monogenic diseases at the cell level have been revealed, and clinical trials of various cell products derived from iPSCs have begun. However, it is necessary to reach a qualitatively new level of research with cell models of diseases based on iPSCs for more efficient searching and testing of drugs. Biosensor technology has a great application prospect together with iPSCs. Biosensors enable researchers to monitor ions, molecules, enzyme activities, and channel conformation in live cells and use them in live imaging and drug screening. These probes facilitate the measurement of steady-state concentrations or activity levels and the observation and quantification of in vivo flux and kinetics. Real-time monitoring of drug action in a specific cellular compartment, organ, or tissue type; the ability to screen at the single-cell resolution; and the elimination of the false-positive results caused by low drug bioavailability that is not detected by in vitro testing methods are a few of the benefits of using biosensors in drug screening. Here, we discuss the possibilities of using biosensor technology in combination with cell models based on human iPSCs and gene editing systems. Furthermore, we focus on the current achievements and problems of using these methods.

Catalytic Clusterbody for Enhanced Quantitative Protein Immunoblot

To assess low-abundance protein biomarkers associated with tumor progression, we have developed artificial catalytic antibodies based on well-defined metal clusters modified with rationally designed peptides, termed clusterbodies. Such clusterbodies possess favorable integrated features of matched ultrasmall sizes, intrinsic fluorescence, and enzyme-like catalytic and selective recognition properties that are inaccessible to traditional antibodies. Consequently, a quantitative assay with high accuracy and high sensitivity is established by measuring the fluorescence and catalytic chemiluminescence of metal clusters preferentially recognizing the protein biomarker, which is confirmed by the molecular-weight marker references of immunoblotting. The results of quantitative immunoblotting are highly close to that derived from the enzyme-linked immunosorbent assay, implying the reliability of this protocol. Remarkably, the detection limit of the aimed protein achieved is as low as 1.0 pg, one magnitude lower than that of the conventional immunoassay. The significant variation of expression levels of the biomarker in tumor cells evidently indicates their distinguished invasion ability. This platform has potential application in analyzing low-abundance protein biomarkers in complex biological matrixes, which is essential to corroborate tumor malignancy in early stage. It inspires the construction of clusterbody-based precise bioprobes with customized structures and integrative functions for advanced quantitative biosensing.

Wavelength-Tunable, Long Lifetime, and Biocompatible Luminescent Nanoparticles Based on a Vitamin E-Derived Material for Inflammation and Tumor Imaging

Luminescence imaging is one of the most effective noninvasive strategies for detection and stratification of inflammation and oxidative stress that are closely related to the pathogenesis of numerous acute and chronic diseases. Herein biocompatible nanoparticles based on a peroxalate ester derived from vitamin E (defined as OVE) are developed. In combination with different fluorophores, OVE can generate luminescence systems with emission wavelengths varying from blue to the near-infrared light in its native and nanoparticle forms, in the presence of hydrogen peroxide (H₂ O₂ ). The OVE-based nanoprobes exhibit high luminescence signals with extremely long lifetime, upon triggering by inflammatory conditions with abnormally elevated H₂ O₂ . Activated neutrophils and macrophages can be illuminated by this type of luminescent nanoprobes, with luminescence intensities positively correlated with inflammatory cell counts. In mouse models of peritonitis, alcoholic liver injury, drug-induced acute liver injury, and acute lung injury, the developed luminescence nanoprobes enable precision imaging of inflammation and disease progression. Moreover, tumors expressing a high level of H₂ O₂ can be shined. Importantly, the OVE-based nanoplatform shows excellent in vitro and in vivo biocompatibility.

Mutant firefly luciferase enzymes resistant to the inhibition by sodium chloride

OBJECTIVES

Firefly luciferase, one of the most extensively studied enzymes, has numerous applications. However, luciferase activity is inhibited by sodium chloride. This study was aimed at obtaining mutant luciferase enzymes resistant to the sodium chloride inhibition.

RESULTS

We first obtained two mutant luciferase enzymes whose inhibition were alleviated and determined the mutations to be Val288Ile and Glu488Val. Under medical dialysis condition (140 mM sodium chloride), the wild type was inhibited to 44% of its original activity level. In contrast, the single mutants, Val288Ile and Glu488Val, retained 67% and 79% of their original activity, respectively. Next, we introduced Val288Ile and Glu488Val mutations into wild-type luciferase to create a double mutant using site-directed mutagenesis. Notably, the double mutant retained its activity more than 95% of that in the absence of sodium chloride.

CONCLUSIONS

The mutant luciferase, named luciferase CR, was found to retain its activity in various concentrations of sodium chloride. The luciferase CR may be extensively useful in any bioassay which includes firefly luciferase and is employed in the presence of sodium chloride.

Metal enhanced chemiluminescence nanosensor for ultrasensitive bioassay based on silver nanoparticles modified functional DNA dendrimer

A novel metal enhanced chemiluminescence (MEC) nanosensor was developed for ultrasensitive biosensing and imaging, based on functional DNA dendrimer (FDD), proximity-dependent DNAzyme and silver nanoparticles (AgNPs). The FDD containing two split G-quadruplex structures was prepared through an enzyme-free and step-by-step assembly strategy, and then reacted with AgNPs and hemin molecules to form the FDD/hemin/AgNPs facilely. Such a MEC nanosensor consisted of three modules: FDD (scaffold), the generated G-quadruplex/hemin DNAzyme (signal reporter) and AgNPs (chemiluminescence enhancer). The MEC effect was achieved by controlling the length of DNA sequences between AgNPs on the periphery of FDD and DNAzymes inside it. Such nanosensor exhibited 9-fold amplification and another 6.4-fold metal enhancement in chemiluminescence intensity, which can be easily applied into trace detection of multiple protein markers using a disposable protein immunoarray. The FDD/hemin/AgNPs-based multiplex MEC imaging assay showed wide linear ranges over 5 orders of magnitude and detection limits down to 5× 10^-5 ng L^-1 and 1.8 × 10^-4 U mL^-1 for cardiac troponin T and carcinoma antigen 125, demonstrating a promising potential in application to protein analysis and clinical diagnosis. Moreover, the MEC nanosensor can be effectively delivered into cells with excellent biocompatibility and outstanding stability, offering a new tool for detection of intracellular targets and suggesting wide applications in bioassay.

Fluorescent Probe for Monitoring Hydrogen Peroxide in COX-2-Positive Cancer Cells

Hydrogen peroxide (H₂O₂), an important marker for oxidative stress, plays a vital role in cellular biological functions. Overproduction of H₂O₂ causes oxidative damage to cellular functions and promotes cancer and other neurodegenerative diseases. Also, cyclooxygenase-2 (COX-2) enzyme is known to be expressed in several cancer types and exerts multifaceted roles in carcinogenesis and resistance to cancer treatment. Hence, it is important to monitor the H₂O₂ concentration changes in the COX-2-expressing cancer cells. Herein, we have developed a molecular fluorescent ratiometric H₂O₂-responsive probe (NPDIN) composed of indomethacin (COX-2 inhibitor) conjugated with 1,8-napthalimide boronate ester as fluorescent reporter through a chemical linker. The probe was capable of imaging the endogenous H₂O₂ in COX-2 overexpressing cancer cell lines (A549, LoVo, HT29, and Caco-2). Further studies revealed the critical role of the indomethacin moiety in the cellular uptake behavior of NPDIN in COX-2-overexpressing cancer cells. Collectively, our results demonstrated NPDIN as a COX-2-positive cancer-targeting sensitive ratiometric fluorescent probe (I₅₅₄/I₃₉₈) for H₂O₂ imaging and showed its promising biological applications in the future.

The Recombinant Luciferase of the Fungus Neonothopanus nambi: Obtaining and Properties

A key component of the recently described bioluminescent system of higher fungi is luciferase, a new class of proteins. The properties of fungal luciferase and their relationship with its structure are interesting both for improving autoluminescent systems already created on its basis and for creating new ones. Therefore, it is extremely important to understand the spatial structure of this protein. We have performed heterologous expression and purification of Neonothopanus nambi luciferase, obtained a protein suitable for subsequent crystallization, and also determined some biochemical properties of the recombinant luciferase.

Rational Design and Mutagenesis of Fungal Luciferase from Neonothopanus nambi

The recently described bioluminescent system from fungi has great potential for developing highly efficient tools for biomedical research. Luciferase enzyme is one of the most crucial components of this system. The luciferase from Neonothopanus nambi fungus belongs to the novel still undescribed protein family. The structure data for this protein is almost absent. A detailed study of the N. nambi luciferase properties is necessary for the improvement of analytical methods based on the fungal bioluminescent system. Here we present the positions of key amino acid residues and their effect on enzyme function described using bioinformatic and experimental approaches. These results are useful for further fungal luciferase structure determination.

Direct Comparison of Triggering Motifs on Chemiluminescent Probes for Hydrogen Sulfide Detection in Water

Hydrogen sulfide (H2S) is an important biomolecule and significant efforts have focused on developing chemical tools to aid different biological investigations. Of such tools, there are relatively few chemiluminescent or bioluminescent methods for H2S detection. Here we report two dioxetane-based chemiluminescent probes for H2S detection. With these probes, we directly compare the probe response to H2S-mediated azide reduction and nucleophilic displacement of 2,4-dinitrophenyl motifs and demonstrate that the SNAr cleavage of the DNP group results in a larger response and greater stability in water.

Frontiers in Multiscale Modeling of Photoreceptor Proteins

This perspective article highlights the challenges in the theoretical description of photoreceptor proteins using multiscale modeling, as discussed at the CECAM workshop in Tel Aviv, Israel. The participants have identified grand challenges and discussed the development of new tools to address them. Recent progress in understanding representative proteins such as green fluorescent protein, photoactive yellow protein, phytochrome, and rhodopsin is presented, along with methodological developments.

Novel Protease-Free Long-Lasting Chemiluminescence System Based on the Dox-ABEI Chimeric Magnetic DNA Hydrogel for Ultrasensitive Immunoassay

Most of chemiluminescence (CL) substrates exhibit the flash-type light emission. Therefore, the long-lasting CL system is always the crown in the field of CL-based analysis methodology. In this work, we constructed a Dox-ABEI chimeric magnetic DNA hydrogel (MDH) as a novel protease-free long-lasting CL reaction system. The functional MDH can transform flash-type ABEI/H₂O₂/CO²⁺ reaction into a glow-type CL system because of its block effect on delaying the diffusion rate of co-reactants, making the CL reaction gradually occur. More importantly, the functional MDH possessed the advantages of biocompatibility and controllability and could be well-designed to incorporate different biosensing strategies. Subsequently, we established a functional MDH-based long-lasting CL immunoassay system for ultrasensitive and highly specific detection of d-dimer and fibrin degradation products (FDPs). The designed CL immunoassay can detect d-dimer and FDP down to 53.7 and 31.6 fg/mL, respectively, with a wide line ranging from 100 fg/mL to 100 ng/mL, which was superior to the previously reported CL biosensing strategies. Moreover, benefiting from the magnetic separation of MDH and excellent CL performance, the developed immunoassaying method was successfully applied in the detection of clinical samples, which showed a close correlation with clinical reference technology. Thus, this functional MDH proved to be an excellent long-lasting CL system and a potential technical platform for clinical bioanalysis applications.

Advanced Bioluminescence System for In Vivo Imaging with Brighter and Red-Shifted Light Emission

In vivo bioluminescence imaging (BLI), which is based on luminescence emitted by the luciferase-luciferin reaction, has enabled continuous monitoring of various biochemical processes in living animals. Bright luminescence with a high signal-to-background ratio, ideally red or near-infrared light as the emission maximum, is necessary for in vivo animal experiments. Various attempts have been undertaken to achieve this goal, including genetic engineering of luciferase, chemical modulation of luciferin, and utilization of bioluminescence resonance energy transfer (BRET). In this review, we overview a recent advance in the development of a bioluminescence system for in vivo BLI. We also specifically examine the improvement in bioluminescence intensity by mutagenic or chemical modulation on several beetle and marine luciferase bioluminescence systems. We further describe that intramolecular BRET enhances luminescence emission, with recent attempts for the development of red-shifted bioluminescence system, showing great potency in in vivo BLI. Perspectives for future improvement of bioluminescence systems are discussed.

Gaussia Luciferase as a Reporter for Quorum Sensing in Staphylococcus aureus

Gaussia luciferase (GLuc) is a secreted protein with significant potential for use as a reporter of gene expression in bacterial pathogenicity studies. To date there are relatively few examples of its use in bacteriology. In this study we show that GLuc can be functionally expressed in the human pathogen Staphylococcus aureus and furthermore show that it can be used as a biosensor for the agr quorum sensing (QS) system which employs autoinducing peptides to control virulence. GLuc was linked to the P3 promoter of the S. aureusagr operon. Biosensor strains were validated by evaluation of chemical agent-mediated activation and inhibition of agr. Use of GLuc enabled quantitative assessment of agr activity. This demonstrates the utility of Gaussia luciferase for in vitro monitoring of agr activation and inhibition.

Evaluation of NanoLuc, RedLuc and Luc2 as bioluminescent reporters in a cutaneous leishmaniasis model

New drugs for the treatment of human leishmaniasis are urgently needed, considering the limitations of current available options. However, pre-clinical evaluation of drug candidates for leishmaniasis is challenging. The use of luciferase-expressing parasites for parasite load detection is a potentially powerful tool to accelerate the drug discovery process. We have previously described the use of Leishmania amazonensis mutants expressing firefly luciferase (Luc2) for drug testing. Here, we describe three new mutant L. amazonensis lines that express different variants of luciferases: NanoLuc, NanoLuc-PEST and RedLuc. These mutants were evaluated in drug screening protocols. NanoLuc-parasites, in spite of high bioluminescence intensity in vitro, were shown to be inadequate in discriminating between live and dead parasites. Bioluminescence detection from intracellular amastigotes expressing NanoLuc-PEST, RedLuc or Luc2 proved more reliable than microscopy to determine parasite killing. Increased sensitivity was observed in vivo with RedLuc-expressing parasites as compared to NanoLuc-expressing L. amazonensis. Our data indicates that NanoLuc is not suitable for in vivo parasite burden determination. Additionally, RedLuc and the conventional luciferase Luc2 demonstrated equivalent sensitivity in an in vivo model of cutaneous leishmaniasis.

Temporal-Spatial-Color Multiresolved Chemiluminescence Imaging for Multiplex Immunoassays Using a Smartphone Coupled with Microfluidic Chip

Chemiluminescence (CL) bioassays have become a main technology in clinical diagnosis. However, multiplex analysis for sensitive and simultaneous determination of multiple biomarkers related to one disease in one detection run on a single chip in order to achieve fast and accurate diagnosis of diseases remains a great challenge. Herein, we report temporal-spatial-color multiresolved CL imaging strategy for multiplex label-free immunoassays using a smartphone coupled with a microfluidic chip. Temporal-spatial-color multiresolved CL imaging signals were produced by sequentially transporting coreactant H₂O₂ to the detection zones to initiate cobalt-based zeolitic imidazolate frameworks ZIF-67 catalyzed luminol-H₂O₂ CL and CL resonance energy transfer reactions. As proof-of-concept, a ZIF-67 regulated sensing strategy was developed for multiplex analysis of three model cancer biomarkers with a low detection limit of pg/mL to fg/mL, good selectivity, and low-cost, avoiding complicated labeling procedures and interferences from adjacent detection zones. This work opens a door for temporal-spatial-color multiresolved imaging for multiplex analysis.

Imaging of intranasal drug delivery to the brain

Intranasal (IN) delivery is a rapidly developing area for therapies with great potential for the treatment of central nervous system (CNS) diseases. Moreover, in vivo imaging is becoming an important part of therapy assessment, both clinically in humans and translationally in animals. IN drug delivery is an alternative to systemic administration that uses the direct anatomic pathway between the olfactory/trigeminal neuroepithelium of the nasal mucosa and the brain. Several drugs have already been approved for IN application, while others are undergoing development and testing. To better understand which imaging modalities are being used to assess IN delivery of therapeutics, we performed a literature search with the key words "Intranasal delivery" and "Imaging" and summarized these findings in the current review. While this review does not attempt to be fully comprehensive, we intend for the examples provided to allow a well-rounded picture of the imaging tools available to assess IN delivery, with an emphasis on the nose-to-brain delivery route. Examples of in vivo imaging, for both humans and animals, include magnetic resonance imaging (MRI), positron emission tomography (PET), single-photon emission computed tomography (SPECT), gamma scintigraphy and computed tomography (CT). Additionally, some in vivo optical imaging modalities, including bioluminescence and fluorescence, have been used more in experimental testing in animals. In this review, we introduce each imaging modality, how it is being utilized and outline its strengths and weaknesses, specifically in the context of IN delivery of therapeutics to the brain.