Engineering a thermophilic luciferase variant from Photuris pennsylvanica into a mesophilic-like enzyme for expanded applications potential

Luciferase, known for its exceptional catalytic bioluminescent properties, has been widely utilized in diverse applications within biotechnology and medical research. Currently, enhancing thermostability and catalytic activity is a primary focus for optimizing luciferase modifications to further expand its detection range and accuracy. This study revealed a highly thermostable luciferase variant from Photuris pennsylvanica, Ppe146-1H2, which inherently exhibits thermophilic enzyme characteristics that are not conducive for optimal catalytic performance in practical applications. Building upon structural analysis, this research engineered Ppe146-1H2 into Ppe146-LGR via the residue substitutions I422L, D435G, and I519R. Ppe146-LGR retained notably thermostability, exhibiting a melting temperature (Tm value) of 75.3 ± 0.3 °C. Additionally, the variant demonstrated efficient catalytic activity at moderate temperatures, exhibiting 3.8 and 3.7-fold higher catalytic efficiencies towards D-luciferin and ATP at 37 °C compared to Ppe146-1H2. Overall, Ppe146-LGR displayed mesophilic-like catalytic activity and thermophilic-like thermostability simultaneously. In addition to enhanced catalytic properties, Ppe146-LGR emitted longer-wavelength light (580 nm) and operated optimally at near-neutral pH, coordinating with the current demands of luciferase applications. Through validation via rapid bacterial detection and reporter gene assays, it has been demonstrated that Ppe146-LGR holds promise as a valuable tool in the field of bioluminescence technology.

Mechanisms and applications of bacterial luciferase and its auxiliary enzymes

Bacterial luciferase (LuxAB) catalyzes the conversion of reduced flavin mononucleotide (FMNH⁻), oxygen, and a long-chain aldehyde to oxidized FMN, the corresponding acid and water with concomitant light emission. This bioluminescence reaction requires the reaction of a flavin reductase such as LuxG (in vivo partner of LuxAB) to supply FMNH⁻ for the LuxAB reaction. LuxAB is a well-known self-sufficient luciferase system because both aldehyde and FMNH⁻ substrates can be produced by the associated enzymes encoded by the genes in the lux operon, allowing the system to be auto-luminous. This makes it useful for in vivo applications. Structural and functional studies have long been performed in efforts to gain a better understanding of the LuxAB reaction. Recently, continued exploration of the LuxAB reaction have elucidated the mechanisms of C4a-hydroperoxyflavin formation and identified key catalytic residues such as His44 that facilitates the generation of flavin intermediates important for light generation. Advancements in protein engineering and synthetic biology have improved the bioluminescence properties of LuxAB. Various applications of LuxAB for bioimaging, bioreporters, biosensing in metabolic engineering and real-time monitoring of aldehyde metabolites in biofuel production pathways have been developed during the last decade. Challenging issues such as achieving red-shifted emissions, optimizing the signal intensity and identifying mechanisms related to the generation of light-emitting species remain to be explored. Nevertheless, LuxAB continues to be a promising tool for diverse biotechnological and biomedical applications.

Machine Learning Nonadiabatic Dynamics: Eliminating Phase Freedom of Nonadiabatic Couplings with the State-Interaction State-Averaged Spin-Restricted Ensemble-Referenced Kohn-Sham Approach

Excited-state molecular dynamics (ESMD) simulations near conical intersections (CIs) pose significant challenges when using machine learning potentials (MLPs). Although MLPs have gained recognition for their integration into mixed quantum-classical (MQC) methods, such as trajectory surface hopping (TSH), and their capacity to model correlated electron-nuclear dynamics efficiently, difficulties persist in managing nonadiabatic dynamics. Specifically, singularities at CIs and double-valued coupling elements result in discontinuities that disrupt the smoothness of predictive functions. Partial solutions have been provided by learning diabatic Hamiltonians with phaseless loss functions to these challenges. However, a definitive method for addressing the discontinuities caused by CIs and double-valued coupling elements has yet to be developed. Here, we introduce the phaseless coupling term, Δ2, derived from the square of the off-diagonal elements of the diabatic Hamiltonian in the state-interaction state-averaged spin-restricted ensemble-referenced Kohn-Sham (SI-SA-REKS, briefly SSR)(2,2) formalism. This approach improves the stability and accuracy of the MLP model by addressing the issues arising from CI singularities and double-valued coupling functions. We apply this method to the penta-2,4-dieniminium cation (PSB3), demonstrating its effectiveness in improving MLP training for ML-based nonadiabatic dynamics. Our results show that the Δ2-based ML-ESMD method can reproduce ab initio ESMD simulations, underscoring its potential and efficiency for broader applications, particularly in large-scale and long-time scale ESMD simulations.

Automated Engineering Protein Dynamics via Loop Grafting: Improving Renilla Luciferase Catalysis

Engineering protein dynamics is a challenging and unsolved problem in protein design. Loop transplantation or loop grafting has been previously employed to transfer dynamic properties between proteins. We recently released a LoopGrafter Web server to execute the loop grafting task, employing eight computational tools and one database. The LoopGrafter method relies on the prediction of the local dynamic behavior of the elements to be transplanted and has successfully reconstructed previously engineered sequences. However, it was unclear whether catalytically competitive previously uncharacterized designs could be obtained by this method. Here, we address this question, showing how LoopGrafter generates viable loop-grafted chimeras of luciferases, how these chimeras encompass the activity of interest and unique kinetic properties, and how all this process is done fully automatically and agnostic of any previous knowledge. All constructed designs proved to be catalytically active, and the most active one improved the activity of the template enzyme by 4 orders of magnitude. The computational details and parameter optimization of the sequence pairing step of the LoopGrafter workflow are revealed. The optimized and experimentally validated loop grafting workflow available as a fully automated Web server represents a powerful approach for engineering catalytically efficient enzymes by modification of protein dynamics.

A Bioluminescent Probe for H2S Detection in Tumor Microenvironment

Hydrogen sulfide (H2S) is an endogenous gaseous signaling molecule that regulates various physiological functions, and its abnormal levels have been closely linked to the onset and progression of numerous diseases including renal cell carcinoma (RCC). RCC is the most common malignant tumor of the kidney, accounting for 85-90% of all kidney cancer cases. However, studies using H2S as a biomarker for monitoring RCC progression at the molecular level remain relatively limited. Most current H2S luminescent probes suffer from low sensitivity and often need external stimuli, such as cysteine, to artificially elevate H2S levels, thereby reducing their effectiveness in detecting H2S in cells or in vivo. Although bioluminescent imaging probes are gaining attention for their specificity and high signal-to-noise ratio, no existing probes are specifically designed for detecting H2S in RCC. Additionally, many bioluminescent probes face challenges such as short emission wavelengths or dependence on complex conditions such as external adenosine triphosphate (ATP). Herein, through "caging" the luciferin substrate QTZ with H2S recognition groups, a H2S-sensitive bioluminescent probe QTZ-N3 with good sensitivity (∼0.19 μM) and selectivity was prepared. QTZ-N3 can effectively detect endogenous H2S in 786-O-Nluc renal cancer cells and sensitively monitor H2S levels in the RCC xenograft nude mouse model without requiring stimuli like cysteine. Furthermore, QTZ-N3 allows for the real-time monitoring of H2S during tumor progression. This work lays a solid foundation for future understanding of the biological functions of H2S in vivo.

Stimuli-Responsive DNA Nanomachines for Intracellular Targeted Electrochemiluminescence Imaging in Single Cells

Electrochemiluminescence (ECL) microscopy has emerged as a powerful technique for single-cell imaging owing to its unparalleled background-free imaging advantages. However, controlled intracellular ECL imaging remains challenging. Here, we developed a stimuli-responsive self-assembled DNA nanomachine that enables the ECL imaging of intracellular target biomolecules in single cells. The ECL nanoprobe consists of an ECL nanoemitter constructed from Ru(bpy)3 2+-doped metal-organic framework as the nanoreactor core, with a DNA polymer hydrogel (DNAgel) shell acting as the stimuli-gated layer. The outer functionalized DNAgel of the ECL nanoprobe was specifically designed to block ECL generation and to dissociate by ATP molecules, thereby enabling selective recovery of ECL emission capability. Such an engineered stimuli-responsive nanomachine successfully achieved the targeted ECL imaging of intracellular ATP distribution with spatial resolution. In addition, ECL imaging of various intracellular biomolecules should be generalizable by simply changing the switching DNA sequence of the probe. Our research provided a reliable strategy for ECL microscopy within cells, which will broaden the application of ECL in single-cell and single-molecule profiling.

Inspired by nature: Bioluminescent systems for bioimaging applications

Bioluminescence is a natural process where biological organisms produce light through chemical reactions. These reactions predominantly occur between small-molecule substrates and luciferase within bioluminescent organisms. Bioluminescence imaging (BLI) has shown significant potential in biomedical research owing to its non-invasive, real-time observation and quantification. In this review, we introduced the chemical mechanism of bioluminescent systems and categorized several strategies that successfully addressed the native limitations, including improvements on the chemical structures of luciferase-luciferin bioluminescence system and bioluminescence resonance energy transfer (BRET) methods. In addition, we also reviewed and summarized recent advances in bioimaging applications. We hope that this review can provide effective guidance for the development and application of bioluminescent systems in the field of bioimaging.

Genetically Engineered Bacteria as A Living Bioreactor for Monitoring and Elevating Hypoxia-Activated Prodrug Tumor Therapy

Tirapazamine (TPZ), an antitumor prodrug, can be activated in hypoxic environment. It specifically targets the hypoxic microenvironment of tumors and produces toxic free radicals. However, due to the tumor is not completely hypoxic, TPZ often fails to effectively treat the entire tumor tissue, resulting in suboptimal therapeutic outcomes. Herein, a low pathogenic Escherichia coli TOP10 is utilized to selectively colonize tumor tissues, disrupt blood vessels, and induce thrombus formation, leading to the expansion of hypoxic region and improving the therapeutic effect of TPZ. Additionally, a thermosensitive hydrogel is constructed by Pluronic F-127 (F127), which undergoes gelation in situ at the tumor site, resulting in sustained release of TPZ. To monitor the therapeutic process, it is genetically modified TOP10 by integrating the bioluminescent system luxCDABE (TOP10-Lux). The bioluminescent signal is associated with tumor hypoxia enhancement and thrombus formation, which is beneficial for therapeutic monitoring with bioluminescence imaging. In the murine colon cancer model, the TOP10-Lux combined with TPZ-loaded F127 hydrogel effectively suppressed tumor growth, and the treatment process is efficiently monitored. Together, this work employs genetically modified TOP10-Lux to enhance the therapeutic efficacy of TPZ and monitor the treatment process, providing an effective strategy for bacteria-based tumor-targeted chemotherapy and treatment monitoring.

Holistic monitoring of Campylobacter jejuni biofilms with NanoLuc bioluminescence

Campylobacter jejuni, a major cause of foodborne zoonotic infections worldwide, shows a paradoxical ability to survive despite its susceptibility to environmental and food-processing stressors. This resilience is likely due to the bacterium entering a viable but non-culturable state, often within biofilms, or even initiating biofilm formation as a survival strategy. This study presents an innovative application of NanoLuc bioluminescence to accurately monitor the development of C. jejuni biofilms on various substrates, such as polystyrene plates, mucin-coated surfaces, and chicken juice matrices. Introduction of NanoLuc luciferase in a pathogenic C. jejuni strain enables rapid non-invasive holistic observation, capturing a spectrum of cell states that may comprise live, damaged, and viable but non-culturable populations. Our comparative analysis with established biofilm quantification methods highlights the specificity, sensitivity, and simplicity of the NanoLuc assay. The assay is efficient and offers precise cell quantification and thus represents an important complementary or alternative method to conventional biofilm monitoring methods. The findings of this study highlight the need for a versatile approach and suggest combining the NanoLuc assay with other methods to gain comprehensive insight into biofilm dynamics. KEY POINTS: • Innovative NanoLuc bioluminescence assay for sophisticated biofilm quantification. • Holistic monitoring of C. jejuni biofilm by capturing live, damaged and VBNC cells. • Potential for improving understanding of biofilm development and structure.

Bioluminescent Pseudomonas aeruginosa and Escherichia coli for whole-cell screening of antibacterial and adjuvant compounds

Continued efforts to discover new antibacterial molecules are critical to achieve a robust pre-clinical pipeline for new antibiotics. Screening of compound or natural product extract libraries remains a widespread approach and can benefit from the development of whole cell assays that are robust, simple and versatile, and allow for high throughput testing of antibacterial activity. In this study, we created and validated two bioluminescent reporter strains for high-throughput screening, one in Pseudomonas aeruginosa, and another in a hyperporinated and efflux-deficient Escherichia coli. We show that the bioluminescent strains have a large dynamic range that closely correlates with cell viability and is superior to conventional optical density (OD600) measurements, can detect dose-dependent antibacterial activity and be used for different drug discovery applications. We evaluated the assays' performance characteristics (signal to background ratio, signal window, Z' robust) and demonstrated their potential utility for antibiotic drug discovery in two examples. The P. aeruginosa bioluminescent reporter was used in a pilot screen of 960 repurposed compound libraries to identify adjuvants that potentiate the fluoroquinolone antibiotic ofloxacin. The E. coli bioluminescent reporter was used to test the antibacterial activity of bioactive bacterial supernatants and assist with bioassay-guided fractionation of the crude extracts.

A practical, biomimetic, one-pot synthesis of firefly luciferin

The bioluminescence reaction of firefly luciferase with D-luciferin has become an indispensable imaging technique in modern biology and life science experiments, but the high cost of D-luciferin is limiting its further application. Here, we report a practical, one-pot synthesis of D-luciferin from p-benzoquinone (p-BQ), L-cysteine methyl ester and D-cysteine, with an overall yield of 46%. Our route, which is six steps in length and proceeds via 2-cyano-6-hydroxybenzothiazole, is inspired by the mechanistic study of our previously reported biomimetic, non-enzymatic, one-pot formation of L-luciferin from p-BQ and L-cysteine. Advantages of our route include its high yield, low cost, use of only inexpensive, commercially available reagents, without requiring strictly anhydrous and oxygen-free conditions, and elevated temperatures.

Biomimetic Electrodynamic Metal-Organic Framework Nanosponges for Augmented Treatment of Biofilm Infections

Electrodynamic therapy (EDT) is a promising alternative approach for antibacterial therapy, as reactive oxygen species (ROS) are produced efficiently in response to an electric field without relying on endogenous H2O2 and O2. However, the inherent toxicity of metallic catalysts and numerous bacterial toxins during the therapeutic process still hinder its development. Herein, biomimetic metal-organic (MOF@EV) nanosponges composed of ginger-derived extracellular vesicles (EVs), and electrodynamic metal-organic frameworks (MOFs) are developed for the eradication of bacterial infections and the absorption of toxins. The prolonged circulation time of MOF@EV in vivo facilitates their accumulation at infection sites. More interestingly, MOF@EV can behave as nanosponges and effectively prevent host cells from binding to bacterial toxins, thereby reducing damage to cells. Subsequently, the MOF@EV nanosponges are discovered to work as electro-sensitizers, which is confirmed through both theoretical calculation and experimental verification. As a result, ROS is continuously produced under the electric field to achieve effective EDT-mediated bacterial eradication. Meanwhile, the treatment process of MOF@EV in vivo is visualized in mice infected with luciferase-expressing Staphylococcus aureus (S. aureus), and excellent biofilm eradication capacity and detoxification efficiency are demonstrated in a subcutaneous abscess model. This work provides a promising strategy for the treatment of bacterial infections.

Harnessing Bioluminescence: A Comprehensive Review of In Vivo Imaging for Disease Monitoring and Therapeutic Intervention

The technique of using naturally occurring light-emitting reactants (photoproteins and luciferases] that have been extracted from a wide range of animals is known as bioluminescence imaging, or BLI. This imaging offers important details on the location and functional state of regenerative cells inserted into various disease-modeling animals. Reports on gene expression patterns, cell motions, and even the actions of individual biomolecules in whole tissues and live animals have all been made possible by bioluminescence. Generally speaking, bioluminescent light in animals may be found down to a few centimetres, while the precise limit depends on the signal's brightness and the detector's sensitivity. We can now spatiotemporally visualize cell behaviors in any body region of a living animal in a time frame process, including proliferation, apoptosis, migration, and immunological responses, thanks to BLI. The biological applications of in vivo BLI in nondestructively monitoring biological processes in intact small animal models are reviewed in this work, along with some of the advancements that will make BLI a more versatile molecular imaging tool.

Molecular Spies in Action: Genetically Encoded Fluorescent Biosensors Light up Cellular Signals

Cellular function is controlled through intricate networks of signals, which lead to the myriad pathways governing cell fate. Fluorescent biosensors have enabled the study of these signaling pathways in living systems across temporal and spatial scales. Over the years there has been an explosion in the number of fluorescent biosensors, as they have become available for numerous targets, utilized across spectral space, and suited for various imaging techniques. To guide users through this extensive biosensor landscape, we discuss critical aspects of fluorescent proteins for consideration in biosensor development, smart tagging strategies, and the historical and recent biosensors of various types, grouped by target, and with a focus on the design and recent applications of these sensors in living systems.

Harnessing luciferase chemistry in regulated cell death modalities and autophagy: overview and perspectives

Regulated cell death is a fate of cells in (patho)physiological conditions during which extrinsic or intrinsic signals or redox equilibrium pathways following infection, cellular stress or injury are coupled to cell death modalities like apoptosis, necroptosis, pyroptosis or ferroptosis. An immediate survival response to cellular stress is often induction of autophagy, a process that deals with removal of aggregated proteins and damaged organelles by a lysosomal recycling process. These cellular processes and their regulation are crucial in several human diseases. Exploiting high-throughput assays which discriminate distinct cell death modalities and autophagy are critical to identify potential therapeutic agents that modulate these cellular responses. In the past few years, luciferase-based assays have been widely developed for assessing regulated cell death and autophagy pathways due to their simplicity, sensitivity, known chemistry, different spectral properties and high-throughput potential. Here, we review basic principles of bioluminescent reactions from a mechanistic perspective, along with their implication in vitro and in vivo for probing cell death and autophagy pathways. These include applying luciferase-, luciferin-, and ATP-based biosensors for investigating regulated cell death modalities. We discuss multiplex bioluminescence platforms which simultaneously distinguish between the various cell death phenomena and cellular stress recovery processes such as autophagy. We also highlight the recent technological achievements of bioluminescent tools for the prediction of drug effectiveness in pathways associated with regulated cell death.

Bioluminescent Whole-Cell Bioreporter Bacterial Panel for Sustainable Screening and Discovery of Bioactive Compounds Derived from Mushrooms

This study presents a rapid and comprehensive method for screening mushroom extracts for the putative discovery of bioactive molecules, including those exhibiting antimicrobial activity. This approach utilizes a panel of bioluminescent bacteria, whose light production is a sensitive indicator of various cellular effects triggered by the extracts, including disruption of bacterial communication (quorum sensing), protein and DNA damage, fatty acid metabolism alterations, and oxidative stress induction. The bioassay's strength is its ability to efficiently analyze a large number of extracts simultaneously while also assessing several different mechanisms of toxicity, significantly reducing screening time. All samples analyzed exhibited more than one cellular effect, as indicated by the reporter bacteria. Four samples (C. cornucopioides, F. fomentarius, I. obliquus, and M. giganteus) displayed the highest number (six) of possible mechanisms of antibacterial activity. Additionally, combining extraction and purification protocols with a bioluminescent bacterial panel enables simultaneous improvement of the desired antimicrobial properties of the extracts. The presented approach offers a valuable tool for uncovering the diverse antimicrobial mechanisms of mushroom extracts.

Behind the glow: unveiling the nature of NanoLuc reactants and products

Due to the largely recognized utility of bioluminescence in many fields, a wide variety of luciferase-luciferin systems have been investigated in order to find the best-suited for a number of different applications. The collected knowledge has allowed the identification of a few necessary, or at least desirable, properties, such as bright luminescence, low background signal and small dimension of the enzyme that must exhibit structural stability at operating conditions. The NanoLuc-furimazine pair seems to meet all these requirements, but the mechanism of the reaction and the characteristics of the species responsible for the emission remain unknown. The aim of this study is to identify the luminescent product among the possible forms of oxidized furimazine and to understand how the chemical form and structure of the system, before and after the oxidation, are involved into the reaction mechanism and determine emission. To do this, we consider two possible forms of furimazine, the keto and the enol one, and test which of them is the most plausible candidate in the bioluminescence process on the basis of enzyme-substrate interactions from docking calculations. A similar procedure is repeated for three possible forms of the furimamide luminescent product, and their properties in the protein environment are then evaluated via QM/MM calculations. In contrast with previous indications, our simulations well support the involvement of the enol form of furimazine as reagent and point to the zwitterionic forms of furimamide as emissive species.

Direct and Ultrasensitive Bioluminescent Detection of Intact Respiratory Viruses

Respiratory viruses such as SARS-CoV-2, influenza, and respiratory syncytial virus (RSV) represent pressing health risks. Rapid diagnostic tests for these viruses detect single antigens or nucleic acids, which do not necessarily correlate with the amount of the intact virus. Instead, specific detection of intact respiratory virus particles may be more effective at assessing the contagiousness of a patient. Here, we report GLOVID, a modular biosensor platform to detect intact virions against a background of "free" viral proteins in solution. Our approach harnesses the multivalent display of distinct proteins on the surface of a viral particle to template the reconstitution of a split luciferase, allowing specific, single-step detection of intact influenza A and RSV virions corresponding to 0.1-0.3 fM of genomic units. The protein ligation system used to assemble GLOVID sensors is compatible with a broad range of binding domains, including nanobodies, scFv fragments, and cyclic peptides, which allows straightforward adjustment of the sensor platform to target different viruses.

Point-of-care testing for early-stage liver cancer diagnosis and personalized medicine: Biomarkers, current technologies and perspectives

Liver cancer is a highly prevalent and lethal form of cancer worldwide. In the absence of early diagnosis, treatment options for this disease are severely restricted. Recent advancements in genomics and bioinformatics have facilitated the discovery of a multitude of novel biomarkers that accurately depict an individual's disease diagnosis, progression, and treatment response. Leveraging these breakthroughs, personalized medicine employs an individual's biomarker profile to enable early detection of liver cancer and inform decisions regarding treatment selection, dosage determination, and prognosis assessment. The current lack of readily applicable, timely, and economically viable tools for biomarker analysis has hindered the incorporation of personalized medicine into regular clinical procedures. Over the past decade, significant advancements have been achieved in the field of molecular point-of-care testing (POCT) and amplification techniques, leading to substantial improvements in the diagnosis of liver cancer and the implementation of precision medicine. Instrument-free PCR technology or plasma PCR technology can shorten the complex procedure of in vitro detection of nucleic acid-based biomarkers. Also, compared to traditional ELISA, various nanomaterials modified with monoclonal antibodies to target proteins for recognition, capture, and detection have improved the efficiency of protein-based biomarker detection. These advances have reduced the time and cost of clinical detection of early-stage hepatocellular carcinoma and improved the efficiency of timely diagnosis and survival of suspected patients while reducing unnecessary testing costs and procedures. This review aims to provide a comprehensive overview of the current and emerging biomarkers employed in the early detection of liver cancer, as well as the advancements in point-of-care molecular testing technology and platforms. The primary objective is to assess their potential in facilitating the implementation of personalized medicine. This review ultimately revealed that the diagnosis of early-stage hepatocellular carcinoma not only requires sensitive biomarkers, but its various modifications and changes during the progression of cirrhosis to early-stage hepatocellular carcinoma will be a greater focus of our attention in the future. The rapid development of POCT has facilitated the opportunity to readily detect liver cancer in the general population in the future, and the integration of multi-pathway multiplexing and intelligent algorithms has improved the sensitivity and accuracy of early liver cancer biomarker detection. It is expected that the integration of point-of-care technology will be instrumental in the widespread adoption of personalized medicine in the foreseeable future.

Theoretical Insight into the Fluorescence Spectral Tuning Mechanism: A Case Study of Flavin-Dependent Bacterial Luciferase

Bioluminescence of bacteria is widely applied in biological imaging, environmental toxicant detection, and many other situations. Understanding the spectral tuning mechanism not only helps explain the diversity of colors observed in nature but also provides principles for bioengineering new color variants for practical applications. In this study, time-dependent density functional theory (TD-DFT) and quantum mechanics and molecular mechanics (QM/MM) calculations have been employed to understand the fluorescence spectral tuning mechanism of bacterial luciferase with a focus on the electrostatic effect. The spectrum can be tuned by both a homogeneous dielectric environment and oriented external electric fields (OEEFs). Increasing the solvent polarity leads to a redshift of the fluorescence emission maximum, λF, accompanied by a substantial increase in density. In contrast, applying an OEEF along the long axis of the isoalloxazine ring (X-axis) leads to a significant red- or blue-shift in λF, depending on the direction of the OEEF, yet with much smaller changes in intensity. The effect of polar solvents is directionless, and the red-shifts can be attributed to the larger dipole moment of the S1 state compared with that of the S0 state. However, the effect of OEEFs directly correlates with the difference dipole moment between the S1 and S0 states, which is directional and is determined by the charge redistribution upon deexcitation. Moreover, the electrostatic effect of bacterial luciferase is in line with the presence of an internal electric field (IEF) pointing in the negative X direction. Finally, the key residues that contribute to this IEF and strategies for modulating the spectrum through site-directed point mutations are discussed.

Amino-Acid-Encoded Supramolecular Nanostructures for Persistent Bioluminescence Imaging of Tumor

Bioluminescence imaging (BLI) is a powerful technique for noninvasive monitoring of biological processes and cell transplantation. Nonetheless, the application of D-luciferin, which is widely employed as a bioluminescent probe, is restricted in long-term in vivo tracking due to its short half-life. This study presents a novel approach using amino acid-encoded building blocks to accumulate and preserve luciferin within tumor cells, through a supramolecular self-assembly strategy. The building block platform called Cys(SEt)-X-CBT (CXCBT, with X representing any amino acid) utilizes a covalent-noncovalent hybrid self-assembly mechanism to generate diverse luciferin-containing nanostructures in tumor cells after glutathione reduction. These nanostructures exhibit efficient tumor-targeted delivery as well as sequence-dependent well-designed morphologies and prolonged bioluminescence performance. Among the selected amino acids (X = Glu, Lys, Leu, Phe), Cys(SEt)-Lys-CBT (CKCBT) exhibits the superior long-lasting bioluminescence signal (up to 72 h) and good biocompatibility. This study demonstrates the potential of amino-acid-encoded supramolecular self-assembly as a convenient and effective method for developing BLI probes for long-term biological tracking and disease imaging.

Optical Image Sensors for Smart Analytical Chemiluminescence Biosensors

Optical biosensors have emerged as a powerful tool in analytical biochemistry, offering high sensitivity and specificity in the detection of various biomolecules. This article explores the advancements in the integration of optical biosensors with microfluidic technologies, creating lab-on-a-chip (LOC) platforms that enable rapid, efficient, and miniaturized analysis at the point of need. These LOC platforms leverage optical phenomena such as chemiluminescence and electrochemiluminescence to achieve real-time detection and quantification of analytes, making them ideal for applications in medical diagnostics, environmental monitoring, and food safety. Various optical detectors used for detecting chemiluminescence are reviewed, including single-point detectors such as photomultiplier tubes (PMT) and avalanche photodiodes (APD), and pixelated detectors such as charge-coupled devices (CCD) and complementary metal-oxide-semiconductor (CMOS) sensors. A significant advancement discussed in this review is the integration of optical biosensors with pixelated image sensors, particularly CMOS image sensors. These sensors provide numerous advantages over traditional single-point detectors, including high-resolution imaging, spatially resolved measurements, and the ability to simultaneously detect multiple analytes. Their compact size, low power consumption, and cost-effectiveness further enhance their suitability for portable and point-of-care diagnostic devices. In the future, the integration of machine learning algorithms with these technologies promises to enhance data analysis and interpretation, driving the development of more sophisticated, efficient, and accessible diagnostic tools for diverse applications.

Luciferase-Loaded Calcium Phosphate Nanoparticles for Persistent Bioluminescence Imaging of Orthotopic Breast Tumors

Bioluminescence imaging (BLI) is an important noninvasive optical imaging technique that has been widely used to monitor many biological processes due to its high sensitivity, resolution, and signal-to-noise ratio. However, the BLI technique based on the firefly luciferin-luciferase system is limited by the expression of exogenous luciferase and the short half-life of firefly luciferin, which pose challenges for long-term tracking in vivo. To solve the problems, here we rationally designed an intelligent strategy for persistent BLI in tumors by combining luciferase-loaded calcium phosphate nanoparticles (Luc@CaP NPs) to provide luciferase and the probe Cys(SEt)-Lys-CBT (CKCBT) to slowly produce the luciferase substrate amino luciferin (Am-luciferin). Luc@CaP NPs constructed with CaP as a carrier could enable luciferase activity to be maintained in vivo for at least 12 h. And compared to the conventional substrate luciferin, CKCBT apparently prolonged the BL time by up to 2 h through GSH-induced intracellular self-assembly and subsequent protease degradation-induced release of Am-luciferin. We anticipate that this strategy could be applied for clinical translation in more disease diagnosis and treatment in the near future.

Tetrandrine activates STING/TBK1/IRF3 pathway to potentiate anti-PD-1 immunotherapy efficacy in non-small cell lung cancer

The efficacy of PD-1 therapy in non-small cell lung cancer (NSCLC) patients remains unsatisfactory. Activating the STING pathway is a promising strategy to improve PD-1 inhibitor efficacy. Here, we found tetrandrine (TET), an anti-tumor compound extracted from a medicinal plant commonly used in traditional Chinese medicine, has the ability to inhibit NSCLC tumor growth. Mechanistically, TET induces nuclear DNA damage and increases cytosolic dsDNA, thereby activating the STING/TBK1/IRF3 pathway, which in turn promotes the tumor infiltration of dendritic cells (DCs), macrophages, as well as CD8+ T cells in mice. In vivo imaging dynamically monitored the increased activity of the STING pathway after TET treatment and predicted the activation of the tumor immune microenvironment. We further revealed that the combination of TET with αPD-1 monoclonal antibody (αPD-1 mAb) yields significant anti-cancer effects by promoting CD8+ T cell infiltration and enhancing its cell-killing effect, which in turn reduced the growth of tumors and prolonged survival of NSCLC mice. Therefore, TET effectively eliminates NSCLC cells and enhances immunotherapy efficacy through the activation of the STING pathway, and combining TET with anti-PD-1 immunotherapy deserves further exploration for applications.

Engineering photodynamics for treatment, priming and imaging

Photodynamic therapy (PDT) is a photochemistry-based treatment approach that relies on the activation of photosensitizers by light to locally generate reactive oxygen species that induce cellular cytotoxicity, in particular for the treatment of tumours. The cytotoxic effects of PDT are depth-limited owing to light penetration limits in tissue. However, photodynamic priming (PDP), which inherently occurs during PDT, can prime the tissue microenvironment to adjuvant therapies beyond the direct PDT ablative zone. In this Review, we discuss the underlying mechanisms of PDT and PDP, and their application to the treatment of cancer, outlining how PDP can permeabilize the tumour vasculature, overcome biological barriers, modulate multidrug resistance, enhance immune responses, increase tumour permeability and enable the photochemical release of drugs. We further examine the molecular engineering of photosensitizers to improve their pharmacodynamic and pharmacokinetic properties, increase their molecular specificity and allow image guidance of PDT, and investigate engineered cellular models for the design and optimization of PDT and PDP. Finally, we discuss alternative activation sources, including ultrasound, X-rays and self-illuminating compounds, and outline key barriers to the clinical translation of PDT and PDP.

Unveiling Invisible Extracellular Vesicles: Cutting-Edge Technologies for Their in Vivo Visualization

Extracellular vesicles (EVs), nanosized lipid bilayer vesicles released by nearly all types of cells, play pivotal roles as intercellular signaling mediators with diverse biological activities. Their adaptability has attracted interest in exploring their role as disease biomarker theranostics. However, the in vivo biodistribution and pharmacokinetic profiles of EVs, particularly following administration into living subjects, remain unclear. Thus, in vivo imaging is vital to enhance our understanding of the homing and retention patterns, blood and tissue half-life, and excretion pathways of exogenous EVs, thereby advancing real-time monitoring within biological systems and their therapeutic applications. This review examines state-of-the-art methods including EV labeling with various agents, including optical imaging, magnetic resonance imaging, and nuclear imaging. The strengths and weaknesses of each technique are comprehensively explored, emphasizing their clinical translation. Despite the potential of EVs as cancer theranostics, achieving a thorough understanding of their in vivo behavior is challenging. This review highlights the urgency of addressing current questions in the biology and therapeutic applications of EVs. It underscores the need for continued research to unravel the complexities surrounding EVs and their potential clinical implications. By identifying these challenges, this review contributes to ongoing efforts to optimize EV imaging techniques for clinical use. Ultimately, bridging the gap between research advancements and clinical applications will facilitate the integration of EV-based theranostics, marking a crucial step toward harnessing the full potential of EVs in medical practice.

Ratiometric Readout of Bacterial Infections via a Lyophilized CRISPR-Cas12a Sensor with Color-Changeable Bioluminescence

The healthcare burden imposed by bacterial infections demands robust and accessible diagnostic methods that can be performed outside hospitals and centralized laboratories. Here, we report Pathogen Assay with Ratiometric Luminescence (PEARL), a sensitive and easy-to-operate platform for detecting pathogenic bacteria. The PEARL leveraged a color-changeable CRISPR-Cas12a sensor and recombinase polymerase amplification to elicit ratiometric bioluminescence responses to target inputs. This platform enabled robust and visualized identification of attomolar bacteria genome deoxyribonucleic acid according to the color changes of the reactions. In addition, the components of the color-changeable Cas12a sensor could be lyophilized for 3 month storage at ambient temperature and then be fully activated with the amplicons derived from crude bacterial lysates, reducing the requirements for cold-chain storage and tedious handling steps. We demonstrated that the PEARL assay is applicable for identifying the infections caused by Pseudomonas aeruginosa in different clinical specimens, including sputa, urines, and swabs derived from wounds. These results revealed the potential of PEARL to be used by untrained personnel, which will facilitate decentralized pathogen diagnosis in community- and resource-limited regions.

Bioimaging and prospects of night pearls-based persistence phosphors in cancer diagnostics

Inorganic persistent phosphors feature great potential for cancer diagnosis due to the long luminescence lifetime, low background scattering, and minimal autofluorescence. With the prominent advantages of near-infrared light, such as deep penetration, high resolution, low autofluorescence, and tissue absorption, persistent phosphors can be used for deep bioimaging. We focus on highlighting inorganic persistent phosphors, emphasizing the synthesis methods and applications in cancer diagnostics. Typical synthetic methods such as the high-temperature solid state, thermal decomposition, hydrothermal/solvothermal, and template methods are proposed to obtain small-size phosphors for biological organisms. The luminescence mechanisms of inorganic persistent phosphors with different excitation are discussed and effective matrixes including galliumate, germanium, aluminate, and fluoride are explored. Finally, the current directions where inorganic persistent phosphors can continue to be optimized and how to further overcome the challenges in cancer diagnosis are summarized.

Single-cell level LasR-mediated quorum sensing response of Pseudomonas aeruginosa to pulses of signal molecules

Quorum sensing (QS) is a communication form between bacteria via small signal molecules that enables global gene regulation as a function of cell density. We applied a microfluidic mother machine to study the kinetics of the QS response of Pseudomonas aeruginosa bacteria to additions and withdrawals of signal molecules. We traced the fast buildup and the subsequent considerably slower decay of a population-level and single-cell-level QS response. We applied a mathematical model to explain the results quantitatively. We found significant heterogeneity in QS on the single-cell level, which may result from variations in quorum-controlled gene expression and protein degradation. Heterogeneity correlates with cell lineage history, too. We used single-cell data to define and quantitatively characterize the population-level quorum state. We found that the population-level QS response is well-defined. The buildup of the quorum is fast upon signal molecule addition. At the same time, its decay is much slower following signal withdrawal, and the quorum may be maintained for several hours in the absence of the signal. Furthermore, the quorum sensing response of the population was largely repeatable in subsequent pulses of signal molecules.

Bioluminescent Systems for Theranostic Applications

Bioluminescence, the light produced by biochemical reactions involving luciferases in living organisms, has been extensively investigated for various applications. It has attracted particular interest as an internal light source for theranostic applications due to its safe and efficient characteristics that overcome the limited penetration of conventional external light sources. Recent advancements in protein engineering technologies and protein delivery platforms have expanded the application of bioluminescence to a wide range of theranostic areas, including bioimaging, biosensing, photodynamic therapy, and optogenetics. This comprehensive review presents the fundamental concepts of bioluminescence and explores its recent applications across diverse fields. Moreover, it discusses future research directions based on the current status of bioluminescent systems for further expansion of their potential.

Luminescence Probes in Bio-Applications: From Principle to Practice

Bioanalysis based on optical imaging has gained significant progress in the last few decades. Luminescence probes are capable of detecting, monitoring, and tracing particular biomolecules in complex biological systems to figure out the roles of these molecules in organisms. Considering the rapid development of luminescence probes for bio-applications and their promising future, we have attempted to explore the working principles and recent advances in bio-applications of luminescence probes, in the hope of helping readers gain a detailed understanding of luminescence probes developed in recent years. In this review, we first focus on the current widely used luminescence probes, including fluorescence probes, bioluminescence probes, chemiluminescence probes, afterglow probes, photoacoustic probes, and Cerenkov luminescence probes. The working principles for each type of luminescence probe are concisely described and the bio-application of the luminescence probes is summarized by category, including metal ions detection, secretion detection, imaging, and therapy.

Remote Control of Energy Transformation-Based Cancer Imaging and Therapy

Cancer treatment requires precise tumor-specific targeting at specific sites that allows for high-resolution diagnostic imaging and long-term patient-tailorable cancer therapy; while, minimizing side effects largely arising from non-targetability. This can be realized by harnessing exogenous remote stimuli, such as tissue-penetrative ultrasound, magnetic field, light, and radiation, that enable local activation for cancer imaging and therapy in deep tumors. A myriad of nanomedicines can be efficiently activated when the energy of such remote stimuli can be transformed into another type of energy. This review discusses the remote control of energy transformation for targetable, efficient, and long-term cancer imaging and therapy. Such ultrasonic, magnetic, photonic, radiative, and radioactive energy can be transformed into mechanical, thermal, chemical, and radiative energy to enable a variety of cancer imaging and treatment modalities. The current review article describes multimodal energy transformation where a serial cascade or multiple types of energy transformation occur. This review includes not only mechanical, chemical, hyperthermia, and radiation therapy but also emerging thermoelectric, pyroelectric, and piezoelectric therapies for cancer treatment. It also illustrates ultrasound, magnetic resonance, fluorescence, computed tomography, photoluminescence, and photoacoustic imaging-guided cancer therapies. It highlights afterglow imaging that can eliminate autofluorescence for sustained signal emission after the excitation.

Fluorescent, phosphorescent, magnetic resonance contrast and radioactive tracer labelling of extracellular vesicles

This review focusses on the significance of fluorescent, phosphorescent labelling and tracking of extracellular vesicles (EVs) for unravelling their biology, pathophysiology, and potential diagnostic and therapeutic uses. Various labeling strategies, such as lipid membrane, surface protein, luminal, nucleic acid, radionuclide, quantum dot labels, and metal complex-based stains, are evaluated for visualizing and characterizing EVs. Direct labelling with fluorescent lipophilic dyes is simple but generally lacks specificity, while surface protein labelling offers selectivity but may affect EV-cell interactions. Luminal and nucleic acid labelling strategies have their own advantages and challenges. Each labelling approach has strengths and weaknesses, which require a suitable probe and technique based on research goals, but new tetranuclear polypyridylruthenium(II) complexes as phosphorescent probes have strong phosphorescence, selective staining, and stability. Future research should prioritize the design of novel fluorescent probes and labelling platforms that can significantly enhance the efficiency, accuracy, and specificity of EV labeling, while preserving their composition and functionality. It is crucial to reduce false positive signals and explore the potential of multimodal imaging techniques to gain comprehensive insights into EVs.

Harnessing Bioluminescent Bacteria to Develop an Enzymatic-free Enzyme-linked immunosorbent assay for the Detection of Clinically Relevant Biomarkers

Enzyme-linked immunosorbent assay (ELISA) is the gold standard technique for measuring protein biomarkers due to its high sensitivity, specificity, and throughput. Despite its success, continuous advancements in ELISA and immunoassay formats are crucial to meet evolving global challenges and to address new analytical needs in diverse applications. To expand the capabilities and applications of immunoassays, we introduce a novel ELISA-like assay that we call Bioluminescent-bacteria-linked immunosorbent assay (BBLISA). BBLISA is an enzyme-free assay that utilizes the inner filter effect between the bioluminescent bacteriaAllivibrio fischeriand metallic nanoparticles (gold nanoparticles and gold iridium oxide nanoflowers) as molecular absorbers. Functionalizing these nanoparticles with antibodies induces their accumulation in wells upon binding to molecular targets, forming the classical immune-sandwich complex. Thanks to their ability to adsorb the light emitted by the bacteria, the nanoparticles can suppress the bioluminescence signal, allowing the rapid quantification of the target. To demonstrate the bioanalytical properties of the novel immunoassay platform, as a proof of principle, we detected two clinically relevant biomarkers (human immunoglobulin G and SARS-CoV-2 nucleoprotein) in human serum, achieving the same sensitivity and precision as the classic ELISA. We believe that BBLISA can be a promising alternative to the standard ELISA techniques, offering potential advancements in biomarker detection and analysis by combining nanomaterials with a low-cost, portable bioluminescent platform.

Diagnosis of Nonalcoholic Fatty Liver Disease via a H2S-Responsive Bioluminescent Probe Combined with Firefly Luciferase mRNA Delivery

The early detection of nonalcoholic fatty liver disease (NAFLD) through bioluminescent probes is of great significance. However, there remains a challenge to apply them in nontransgenic natural animals due to the lack of exogenous luciferase. To address this issue, we herein report a new strategy for in situ monitoring of endogenous hydrogen sulfide (H2S) in the liver of NAFLD mice by leveraging a H2S-responsive bioluminescent probe (H-Luc) combined with firefly luciferase (fLuc) mRNA delivery. The probe H-Luc was created by installing a H2S recognition moiety, 2,4-dinitrophenol, onto the luciferase substrate (d-luciferin), which is allowed to release cage-free d-luciferin in the presence of H2S via a nucleophilic aromatic substitution reaction. In the meantime, the intracellular luciferase was introduced by lipid nanoparticle (LNP)-mediated fLuc mRNA delivery, rendering it suitable for bioluminescence (BL) imaging in vitro and in vivo. Based on this luciferase-luciferin system, the endogenous H2S could be sensitively and selectively detected in living cells, showing a low limit of detection (LOD) value of 0.72 μM. More importantly, after systematic administration of fLuc mRNA-loaded LNPs in vivo, H-Luc was able to successfully monitor the endogenous H2S levels in the NAFLD mouse model for the first time, displaying a 28-fold higher bioluminescence intensity than that in the liver of normal mice. We believe that this strategy may shed new light on the diagnosis of inflammatory liver disease, further elucidating the roles of H2S.

Exploring the Light-Emitting Agents in Renilla Luciferases by an Effective QM/MM Approach

Bioluminescence is a fascinating natural phenomenon, wherein organisms produce light through specific biochemical reactions. Among these organisms, Renilla luciferase (RLuc) derived from the sea pansy Renilla reniformis is notable for its blue light emission and has potential applications in bioluminescent tagging. Our study focuses on RLuc8, a variant of RLuc with eight amino acid substitutions. Recent studies have shown that the luminescent emitter coelenteramide can adopt multiple protonation states, which may be influenced by nearby residues at the enzyme's active site, demonstrating a complex interplay between protein structure and bioluminescence. Herein, using the quantum mechanical consistent force field method and the semimacroscopic protein dipole-Langevin dipole method with linear response approximation, we show that the phenolate state of coelenteramide in RLuc8 is the primary light-emitting species in agreement with experimental results. Our calculations also suggest that the proton transfer (PT) from neutral coelenteramide to Asp162 plays a crucial role in the bioluminescence process. Additionally, we reproduced the observed emission maximum for the amide anion in RLuc8-D120A and the pyrazine anion in the presence of a Na+ counterion in RLuc8-D162A, suggesting that these are the primary emitters. Furthermore, our calculations on the neutral emitter in the engineered AncFT-D160A enzyme, structurally akin to RLuc8-D162A but with a considerably blue-shifted emission peak, aligned with the observed data, possibly explaining the variance in emission peaks. Overall, this study demonstrates an effective approach to investigate chromophores' bimolecular states while incorporating the PT process in emission spectra calculations, contributing valuable insights for future studies of PT in photoproteins.

Firefly-inspired bipolar information indication system actuated by white light

The indication of information in materials is widely used in our daily life, and optical encoding materials are ideal for information loading due to their easily readable nature and adjustable optical properties. However, most of them could only indicate one type of information, either changing or unchanging due to the mutual interference. Inspired by firefly, we present a non-interfering bipolar information indication system capable of indicating both changing and unchanging information. A photochemical afterglow material is incorporated into the photonic crystal matrix through a high-throughput technique called shear-induced ordering technique, which can efficiently produce large-area photonic crystal films. The indication of changing and unchanging information is enabled by two different utilizations of white light by the afterglow material and photonic crystals, respectively, which overcome the limitations of mutual interference. As a proof of concept, this system is used to indicate the changing photodegradation level of mecobalamin (a photosensitive medicine) and unchanging intrinsic drug information with anti-counterfeiting functionality, which is a promising alternative to instantly ascertain the efficacy of medicine at home where conventional assays are impractical.

Bioluminescence - The Vibrant Glow of Nature and its Chemical Mechanisms

Bioluminescence, the mesmerizing natural phenomenon where living organisms produce light through chemical reactions, has long captivated scientists and laypersons alike, offering a rich tapestry of insights into biological function, ecology, evolution as well as the underlying chemistry. This comprehensive introductory review systematically explores the phenomenon of bioluminescence, addressing its historical context, geographic dispersion, and ecological significance with a focus on their chemical mechanisms. Our examination begins with terrestrial bioluminescence, discussing organisms from different habitats. We analyze thefireflies of Central Europe's meadows and the fungi in the Atlantic rainforest of Brazil. Additionally, we inspect bioluminescent species in New Zealand, specifically river-dwelling snails and mosquito larvae found in Waitomo Caves. Our exploration concludes in the Siberian Steppes, highlighting the area's luminescent insects and annelids. Transitioning to the marine realm, the second part of this review examines marine bioluminescent organisms. We explore this phenomenon in deep-sea jellyfish and their role in the ecosystem. We then move to Toyama Bay, Japan, where seasonal bioluminescence of dinoflagellates and ostracods present a unique case study. We also delve into the bacterial world, discussing how bioluminescent bacteria contribute to symbiotic relationships. For each organism, we contextualize its bioluminescence, providing details about its discovery, ecological function, and geographical distribution. A special focus lies on the examination of the underlying chemical mechanisms that enables these biological light displays. Concluding this review, we present a series of practical bioluminescence and chemiluminescence experiments, providing a resource for educational demonstrations and student research projects. Our goal with this review is to provide a summary of bioluminescence across the diverse ecological contexts, contributing to the broader understanding of this unique biological phenomenon and its chemical mechanisms serving researchers new to the field, educators and students alike.

Molecular evolution of Cypridina noctiluca secretory luciferase for production of spectrum-shifted luminescence-emitting mutants and their application in nuclear receptor-reporter assays

Luciferase is a popular enzyme used for biological analyses, such as reporter assays. In addition to a conventional reporter assay using a pair of firefly and Renilla luciferases, a simple multicolor reporter assay using multiple firefly or beetle luciferases emitting different color luminescence with a single substrate has been reported. Secretory luciferases have also been used for convenient sample preparation in reporter assays; however, reporter assay using secretory luciferase mutants that emit spectrum-shifted luminescence have not yet been reported. In this study, we generated blue- and red-shifted (-16 and 12 nm) luminescence-emitting Cypridina secretory luciferase (CLuc) mutants using multiple cycles of random and site-directed mutagenesis. Even for red-shifted CLuc mutant, which exhibited relatively low activity and stability, its enzymatic activity was sufficiently high for a luciferase assay (3.26 × 106 relative light unit/s), light emission was sufficiently prolonged (half-life is 3 min), and stability at 37°C was high. We independently determined the luminescence of these CLuc mutants using a luminometer with an optical filter. Finally, we replaced the commonly used reporters, firefly and Renilla luciferases used in a conventional nuclear receptor-reporter assay with these CLuc mutants and established a secretory luciferase-based single-substrate dual-color nuclear receptor-reporter assay.

The BTB-ZF gene Bm-mamo regulates pigmentation in silkworm caterpillars

The color pattern of insects is one of the most diverse adaptive evolutionary phenotypes. However, the molecular regulation of this color pattern is not fully understood. In this study, we found that the transcription factor Bm-mamo is responsible for black dilute (bd) allele mutations in the silkworm. Bm-mamo belongs to the BTB zinc finger family and is orthologous to mamo in Drosophila melanogaster. This gene has a conserved function in gamete production in Drosophila and silkworms and has evolved a pleiotropic function in the regulation of color patterns in caterpillars. Using RNAi and clustered regularly interspaced short palindromic repeats (CRISPR) technology, we showed that Bm-mamo is a repressor of dark melanin patterns in the larval epidermis. Using in vitro binding assays and gene expression profiling in wild-type and mutant larvae, we also showed that Bm-mamo likely regulates the expression of related pigment synthesis and cuticular protein genes in a coordinated manner to mediate its role in color pattern formation. This mechanism is consistent with the dual role of this transcription factor in regulating both the structure and shape of the cuticle and the pigments that are embedded within it. This study provides new insight into the regulation of color patterns as well as into the construction of more complex epidermal features in some insects.

Cloning and characterization of luciferase from an Asian firefly Pygoluciola qingyu and its comparison with other beetle luciferases

The bioluminescence system of luminescent beetles has extensive applications in biological imaging, protein labeling and drug screening. To explore wild luciferases with excellent catalytic activity and thermal stability, we cloned the luciferase of Pygoluciola qingyu, one species living in areas of high temperature and with strong bioluminescence, by combining transcriptomic sequencing and reverse transcription polymerase chain reaction (RT-PCR). The total length of luciferase gene is 1638 bp and the luciferase consists 544 amino acids. The recombinant P. qingyu luciferase was produced in vitro and its characteristics were compared with those of eight luciferases from China firefly species and two commercial luciferases. Compared with these luciferases, the P. qingyu luciferase shows the highest luminescence activity at room temperature (about 25-28 ℃) with similar KM value for D-luciferin and ATP to the Photinus pyralis luciferase. The P. qingyu luciferase activity was highest at 35 ℃ and can keep high activity at 30-40 ℃, which suggests the potential of P. qingyu luciferase for in vivo and cell application. Our results provide new insights into P. qingyu luciferase and give a new resource for the application of luciferases.

Advances in Bio-Optical Imaging Systems for Spatiotemporal Monitoring of Intestinal Bacteria

Vast and complex intestinal communities are regulated and balanced through interactions with their host organisms, and disruption of gut microbial balance can cause a variety of diseases. Studying the mechanisms of pathogenic intestinal flora in the host and early detection of bacterial translocation and colonization can guide clinical diagnosis, provide targeted treatments, and improve patient prognosis. The use of in vivo imaging techniques to track microorganisms in the intestine, and study structural and functional changes of both cells and proteins, may clarify the governing equilibrium between the flora and host. Despite the recent rapid development of in vivo imaging of intestinal microecology, determining the ideal methodology for clinical use remains a challenge. Advances in optics, computer technology, and molecular biology promise to expand the horizons of research and development, thereby providing exciting opportunities to study the spatio-temporal dynamics of gut microbiota and the origins of disease. Here, this study reviews the characteristics and problems associated with optical imaging techniques, including bioluminescence, conventional fluorescence, novel metabolic labeling methods, nanomaterials, intelligently activated imaging agents, and photoacoustic (PA) imaging. It hopes to provide a valuable theoretical basis for future bio-intelligent imaging of intestinal bacteria.

Pseudo-Luciferase Activity of the SARS-CoV-2 Spike Protein for Cypridina Luciferin

Enzymatic reactions that involve a luminescent substrate (luciferin) and enzyme (luciferase) from luminous organisms enable a luminescence detection of target proteins and cells with high specificity, albeit that conventional assay design requires a prelabeling of target molecules with luciferase. Here, we report a luciferase-independent luminescence assay in which the target protein directly catalyzes the oxidative luminescence reaction of luciferin. The SARS-CoV-2 antigen (spike) protein catalyzes the light emission of Cypridina luciferin, whereas no such catalytic function was observed for salivary proteins. This selective luminescence reaction is due to the enzymatic recognition of the 3-(1-guanidino)propyl group in luciferin at the interfaces between the units of the spike protein, allowing a specific detection of the spike protein in human saliva without sample pretreatment. This method offers a novel platform to detect virus antigens simply and rapidly without genetic manipulation or antibodies.

A handheld luminometer with sub-attomole limit of detection for distributed applications in global health

Luminescence is ubiquitous in biology research and medicine. Conceptually simple, the detection of luminescence nonetheless faces technical challenges because relevant signals can exhibit exceptionally low radiant power densities. Although low light detection is well-established in centralized laboratory settings, the cost, size, and environmental requirements of high-performance benchtop luminometers are not compatible with geographically-distributed global health studies or resource-constrained settings. Here we present the design and application of a ~$700 US handheld, battery-powered luminometer with performance on par with high-end benchtop instruments. By pairing robust and inexpensive Silicon Photomultiplier (SiPM) sensors with a low-profile shutter system, our design compensates for sensor non-idealities and thermal drift, achieving a limit of detection of 1.6E-19 moles of firefly luciferase. Using these devices, we performed two pilot cross-sectional serology studies to assess sars-cov-2 antibody levels: a cohort in the United States, as well as a field study in Bangladesh. Results from both studies were consistent with previous work and demonstrate the device's suitability for distributed applications in global health.

Investigation of the Chemiluminescent Reaction of a Fluorinated Analog of Marine Coelenterazine

Bioluminescence (BL) and chemiluminescence (CL) are remarkable processes in which light is emitted due to (bio)chemical reactions. These reactions have attracted significant attention for various applications, such as biosensing, bioimaging, and biomedicine. Some of the most relevant and well-studied BL/CL systems are that of marine imidazopyrazine-based compounds, among which Coelenterazine is a prime example. Understanding the mechanisms behind efficient chemiexcitation is essential for the optimization and development of practical applications for these systems. Here, the CL of a fluorinated Coelenterazine analog was studied using experimental and theoretical approaches to obtain insight into these processes. Experimental analysis revealed that CL is more efficient under basic conditions than under acidic ones, which could be attributed to the higher relative chemiexcitation efficiency of an anionic dioxetanone intermediate over a corresponding neutral species. However, theoretical calculations indicated that the reactions of both species are similarly associated with both electron and charge transfer processes, which are typically used to explain efficiency chemiexcitation. So, neither process appears to be able to explain the relative chemiexcitation efficiencies observed. In conclusion, this study provides further insight into the mechanisms behind the chemiexcitation of imidazopyrazinone-based systems.

A Comprehensive Exploration of Bioluminescence Systems, Mechanisms, and Advanced Assays for Versatile Applications

Bioluminescence has been a fascinating natural phenomenon of light emission from living creatures. It happens when the enzyme luciferase facilitates the oxidation of luciferin, resulting in the creation of an excited-state species that emits light. Although there are many bioluminescent systems, few have been identified. D-luciferin-dependent systems, coelenterazine-dependent systems, Cypridina luciferin-based systems, tetrapyrrole-based luciferins, bacterial bioluminescent systems, and fungal bioluminescent systems are natural bioluminescent systems. Since different bioluminescence systems, such as various combinations of luciferin-luciferase pair reactions, have different light emission wavelengths, they benefit industrial applications such as drug discovery, protein-protein interactions, in vivo imaging in small animals, and controlling neurons. Due to the expression of luciferase and easy permeation of luciferin into most cells and tissues, bioluminescence assays are applied nowadays with modern technologies in most cell and tissue types. It is a versatile technique in a variety of biomedical research. Furthermore, there are some investigated blue-sky research projects, such as bioluminescent plants and lamps. This review article is mainly based on the theory of diverse bioluminescence systems and their past, present, and future applications.

Molecularly generated light and its biomedical applications

Molecularly generated light, referred to here as "molecular light", mainly includes bioluminescence, chemiluminescence, and Cerenkov luminescence. Molecular light possesses unique dual features of being both a molecule and a source of light. Its molecular nature enables it to be delivered as molecules to regions deep within the body, overcoming the limitations of natural sunlight and physically generated light sources like lasers and LEDs. Simultaneously, its light properties make it valuable for applications such as imaging, photodynamic therapy, photo-oxidative therapy, and photobiomodulation. In this review article, we provide an updated overview of the diverse applications of molecular light and discuss the strengths and weaknesses of molecular light across various domains. Lastly, we present forward-looking perspectives on the potential of molecular light in the realms of molecular imaging, photobiological mechanisms, therapeutic applications, and photobiomodulation. While some of these perspectives may be considered bold and contentious, our intent is to inspire further innovations in the field of molecular light applications.

Understanding neural circuit function through synaptic engineering

Synapses are a key component of neural circuits, facilitating rapid and specific signalling between neurons. Synaptic engineering - the synthetic insertion of new synaptic connections into in vivo neural circuits - is an emerging approach for neural circuit interrogation. This approach is especially powerful for establishing causality in neural circuit structure-function relationships, for emulating synaptic plasticity and for exploring novel patterns of circuit connectivity. Contrary to other approaches for neural circuit manipulation, synaptic engineering targets specific connections between neurons and functions autonomously with no user-controlled external activation. Synaptic engineering has been successfully implemented in several systems and in different forms, including electrical synapses constructed from ectopically expressed connexin gap junction proteins, synthetic optical synapses composed of presynaptic photon-emitting luciferase coupled with postsynaptic light-gated channels, and artificial neuropeptide signalling pathways. This Perspective describes these different methods and how they have been applied, and examines how the field may advance.

Cloning and Expression Analysis of Bioluminescence Genes in Omphalotus guepiniiformis Reveal Stress-Dependent Regulation of Bioluminescence

Bioluminescence is a type of chemiluminescence that arises from a luciferase-catalyzed oxidation reaction of luciferin. Molecular biology and comparative genomics have recently elucidated the genes involved in fungal bioluminescence and the evolutionary history of their clusters. However, most studies on fungal bioluminescence have been limited to observing the changes in light intensity under various conditions. To understand the molecular basis of bioluminescent responses in Omphalotus guepiniiformis under different environmental conditions, we cloned and sequenced the genes of hispidin synthase, hispidin-3-hydroxylase, and luciferase enzymes, which are pivotal in the fungal bioluminescence pathway. Each gene showed high sequence similarity to that of other luminous fungal species. Furthermore, we investigated their transcriptional changes in response to abiotic stresses. Wound stress enhanced the bioluminescence intensity by increasing the expression of bioluminescence pathway genes, while temperature stress suppressed the bioluminescence intensity via the non-transcriptional pathway. Our data suggested that O. guepiniiformis regulates bioluminescence to respond differentially to specific environmental stresses. To our knowledge, this is the first study on fungal bioluminescence at the gene expression level. Further studies are required to address the biological and ecological meaning of different bioluminescence responses in changing environments, and O. quepiniiformis could be a potential model species.