In vivo imaging of hydrogen peroxide production in a murine tumor model with a chemoselective bioluminescent reporter

Ex Tenebris Lux: Illuminating Reactive Oxygen and Nitrogen Species with Small Molecule Probes

Reactive oxygen and nitrogen species are small reactive molecules derived from elements in the air─oxygen and nitrogen. They are produced in biological systems to mediate fundamental aspects of cellular signaling but must be very tightly balanced to prevent indiscriminate damage to biological molecules. Small molecule probes can transmute the specific nature of each reactive oxygen and nitrogen species into an observable luminescent signal (or even an acoustic wave) to offer sensitive and selective imaging in living cells and whole animals. This review focuses specifically on small molecule probes for superoxide, hydrogen peroxide, hypochlorite, nitric oxide, and peroxynitrite that provide a luminescent or photoacoustic signal. Important background information on general photophysical phenomena, common probe designs, mechanisms, and imaging modalities will be provided, and then, probes for each analyte will be thoroughly evaluated. A discussion of the successes of the field will be presented, followed by recommendations for improvement and a future outlook of emerging trends. Our objectives are to provide an informative, useful, and thorough field guide to small molecule probes for reactive oxygen and nitrogen species as well as important context to compare the ecosystem of chemistries and molecular scaffolds that has manifested within the field.

Development of a Novel Amplifiable System to Quantify Hydrogen Peroxide in Living Cells

Although many redox signaling molecules are present at low concentrations, typically ranging from micromolar to submicromolar levels, they often play essential roles in a wide range of biological pathways and disease mechanisms. However, accurately measuring low-abundant analytes has been a significant challenge due to the lack of sensitivity and quantitative capability of existing measurement methods. In this study, we introduced a novel chemically induced amplifiable system for quantifying low-abundance redox signaling molecules in living cells. We utilized H2O2 as a proof-of-concept analyte and developed a probe that quantifies cellular peroxide levels by combining the NanoBiT system with androgen receptor dimerization as a reporting mechanism. Our system demonstrated a highly sensitive response to cellular peroxide changes induced both endogenously and exogenously. Furthermore, the system can be adapted for the quantification of other signaling molecules if provided with suitable probing chemistry.

Comparative understanding of peroxide quantitation assays: a case study with peptide drug product degradation

Peroxide-mediated oxidation of drug molecules is a known challenge faced throughout the pharmaceutical development pathway-from early-stage stability studies to manufacturing processes. During the initial development stage, the major source of peroxide is the formulation excipients, whether they are pre-loaded or generated in situ due to slow degradation, and in the late phase, peroxides can be introduced during sanitization processes or generated via cavitation. In essence, a control strategy for peroxide mitigation often becomes a critical quality attribute for successful drug development. To this end, quantitation of peroxide is essential to monitor the peroxide level to ensure product quality and proposed shelf-life. However, methods for reliable and robust quantitation to detect trace levels of peroxide in a complex drug product matrix become increasingly challenging. This article discusses three high-throughput assays based on absorbance, fluorescence and chemiluminescence measurements to detect peroxide at a low level and compares the methods through validation studies in water. Selected methods have also been tested to understand the forced degradation of model peptide drug products with spiked hydrogen peroxide. Peptide degradation profiles and residual peroxide levels are presented to provide an understanding of the suitability of the quantitation methods and their performance.

Bioluminescence Imaging of Potassium Ion Using a Sensory Luciferin and an Engineered Luciferase

Bioluminescent indicators are power tools for studying dynamic biological processes. In this study, we present the generation of novel bioluminescent indicators by modifying the luciferin molecule with an analyte-binding moiety. Specifically, we have successfully developed the first bioluminescent indicator for potassium ions (K+), which are critical electrolytes in biological systems. Our approach involved the design and synthesis of a K+-binding luciferin named potassiorin. Additionally, we engineered a luciferase enzyme called BRIPO (bioluminescent red indicator for potassium) to work synergistically with potassiorin, resulting in optimized K+-dependent bioluminescence responses. Through extensive validation in cell lines, primary neurons, and live mice, we demonstrated the efficacy of this new tool for detecting K+. Our research demonstrates an innovative concept of incorporating sensory moieties into luciferins to modulate luciferase activity. This approach has great potential for developing a wide range of bioluminescent indicators, advancing bioluminescence imaging (BLI), and enabling the study of various analytes in biological systems.

Surface Bio-engineered Polymeric Nanoparticles

Surface bio-engineering of polymeric nanoparticles (PNPs) has emerged as a cornerstone in contemporary biomedical research, presenting a transformative avenue that can revolutionize diagnostics, therapies, and drug delivery systems. The approach involves integrating bioactive elements on the surfaces of PNPs, aiming to provide them with functionalities to enable precise, targeted, and favorable interactions with biological components within cellular environments. However, the full potential of surface bio-engineered PNPs in biomedicine is hampered by obstacles, including precise control over surface modifications, stability in biological environments, and lasting targeted interactions with cells or tissues. Concerns like scalability, reproducibility, and long-term safety also impede translation to clinical practice. In this review, these challenges in the context of recent breakthroughs in developing surface-biofunctionalized PNPs for various applications, from biosensing and bioimaging to targeted delivery of therapeutics are discussed. Particular attention is given to bonding mechanisms that underlie the attachment of bioactive moieties to PNP surfaces. The stability and efficacy of surface-bioengineered PNPs are critically reviewed in disease detection, diagnostics, and treatment, both in vitro and in vivo settings. Insights into existing challenges and limitations impeding progress are provided, and a forward-looking discussion on the field's future is presented. The paper concludes with recommendations to accelerate the clinical translation of surface bio-engineered PNPs.

Bioluminescence Imaging of Potassium Ion Using a Sensory Luciferin and an Engineered Luciferase

Bioluminescent indicators are power tools for studying dynamic biological processes. In this study, we present the generation of novel bioluminescent indicators by modifying the luciferin molecule with an analyte-binding moiety. Specifically, we have successfully developed the first bioluminescent indicator for potassium ions (K+), which are critical electrolytes in biological systems. Our approach involved the design and synthesis of a K+-binding luciferin named potassiorin. Additionally, we engineered a luciferase enzyme called BRIPO (bioluminescent red indicator for potassium) to work synergistically with potassiorin, resulting in optimized K+-dependent bioluminescence responses. Through extensive validation in cell lines, primary neurons, and live mice, we demonstrated the efficacy of this new tool for detecting K+. Our research demonstrates an innovative concept of incorporating sensory moieties into luciferins to modulate luciferase activity. This approach has great potential for developing a wide range of bioluminescent indicators, advancing bioluminescence imaging (BLI), and enabling the study of various analytes in biological systems.

Poly-β-thioester-Based Cross-Linked Nanocarrier for Cancer Cell Selectivity over Normal Cells and Cellular Apoptosis by Triggered Release of Parthenolide, an Anticancer Drug

Breast cancer is the most prevalent and aggressive type of cancer, causing high mortality rates in women globally. Many drawbacks and side effects of the current chemotherapy force us to develop a robust chemotherapeutic system that can deal with off-target hazards and selectively combat cancer growth, invasiveness, and cancer-initiating cells. Here, a pH-responsive cross-linked nanocarrier (140-160 nm) endowed with poly-β-thioester functionality (CBAPTL) has been sketched and fabricated for noncovalent firm encapsulation of anticancer drug, parthenolide (PTL) at physiological pH (7.4), which enables sustain release of PTL at relevant endosomal pH (∼5.0-5.3). For this, a bolaamphiphilic molecule integrated with β-thioester and acrylate functionality was synthesized to fabricate the pH-responsive poly-β-thioester-based cross-linked nanocarrier via Michael addition click reactions in water. The poly-β-thioester functionality of CBAPTL hydrolyzes at endosomal acidic conditions, thus leading to the selective release of PTL inside the cancer cell. Cross-linked nanocarriers exhibit high serum stability, dilution insensitivity, and targeted cellular uptake at tumor microenvironment (TME), contrasting normal cells. In vitro study using human MCF-7 breast cancer cells demonstrated that CBAPTL exhibited selective cytotoxicity, reduced clonogenic potential, increased reactive oxygen species (ROS) generation, and arrested the progression of the cell cycle at the G0/G1 phase efficiently. CBAPTL induced apoptosis via downregulating pro-proliferative protein Bcl-2 and upregulating proapoptotic proteins p53, BAD, p21, and cleaved PARP-1. CBAPTL inhibited proliferating signaling by suppressing AKT phosphorylation and p38 expression. CBAPTL also blocked the invasion and migration of MCF-7 cells. CBAPTL effectively inhibits primary and secondary mammosphere formation, thereby preventing cancer-initiating cells' growth. Conversely, CBAPTL has negligible effect on human red blood cells (RBCs) and peripheral blood mononuclear cells (PBMCs). These findings highlight the superior efficacy of CBAPTL compared to PTL alone in suppressing cancer cell growth, inducing apoptosis, and preventing invasiveness of MCF-7 cells. Thus, CBAPTL could be considered a possible selective chemotherapeutic cargo against breast cancer without affecting normal cells.

Activatable Probes for Ratiometric Imaging of Endogenous Biomarkers In Vivo

Dynamic variations in the concentration and abnormal distribution of endogenous biomarkers are strongly associated with multiple physiological and pathological states. Therefore, it is crucial to design imaging systems capable of real-time detection of dynamic changes in biomarkers for the accurate diagnosis and effective treatment of diseases. Recently, ratiometric imaging has emerged as a widely used technique for sensing and imaging of biomarkers due to its advantage of circumventing the limitations inherent to conventional intensity-dependent signal readout methods while also providing built-in self-calibration for signal correction. Here, the recent progress of ratiometric probes and their applications in sensing and imaging of biomarkers are outlined. Ratiometric probes are classified according to their imaging mechanisms, and ratiometric photoacoustic imaging, ratiometric optical imaging including photoluminescence imaging and self-luminescence imaging, ratiometric magnetic resonance imaging, and dual-modal ratiometric imaging are discussed. The applications of ratiometric probes in the sensing and imaging of biomarkers such as pH, reactive oxygen species (ROS), reactive nitrogen species (RNS), glutathione (GSH), gas molecules, enzymes, metal ions, and hypoxia are discussed in detail. Additionally, this Review presents an overview of challenges faced in this field along with future research directions.

Current advances in the development of bioluminescent probes toward spatiotemporal trans-scale imaging

Bioluminescence imaging has recently attracted great attention as a highly sensitive and non-invasive analytical method. However, weak signal and low chemical stability of the luciferin are conventional drawbacks of bioluminescence imaging. In this review article, we describe the recent progress on the development and applications of bioluminescent probes for overcoming the aforementioned limitations, thereby enabling spatiotemporal trans-scale imaging. The detailed molecular design for manipulation of their luminescent properties and functions enabled a variety of applications, including in vivo deep tissue imaging, long-term imaging, and chemical sensor.

Health position paper and redox perspectives - Disease burden by transportation noise

Transportation noise is a ubiquitous urban exposure. In 2018, the World Health Organization concluded that chronic exposure to road traffic noise is a risk factor for ischemic heart disease. In contrast, they concluded that the quality of evidence for a link to other diseases was very low to moderate. Since then, several studies on the impact of noise on various diseases have been published. Also, studies investigating the mechanistic pathways underlying noise-induced health effects are emerging. We review the current evidence regarding effects of noise on health and the related disease-mechanisms. Several high-quality cohort studies consistently found road traffic noise to be associated with a higher risk of ischemic heart disease, heart failure, diabetes, and all-cause mortality. Furthermore, recent studies have indicated that road traffic and railway noise may increase the risk of diseases not commonly investigated in an environmental noise context, including breast cancer, dementia, and tinnitus. The harmful effects of noise are related to activation of a physiological stress response and nighttime sleep disturbance. Oxidative stress and inflammation downstream of stress hormone signaling and dysregulated circadian rhythms are identified as major disease-relevant pathomechanistic drivers. We discuss the role of reactive oxygen species and present results from antioxidant interventions. Lastly, we provide an overview of oxidative stress markers and adverse redox processes reported for noise-exposed animals and humans. This position paper summarizes all available epidemiological, clinical, and preclinical evidence of transportation noise as an important environmental risk factor for public health and discusses its implications on the population level.

A coronene diimide based radical anion for detection of picomolar H2O2: a biochemical assay for detection of picomolar glucose in aqueous medium

Coronene diimide functionalized with 4-(2-nitrovinyl)phenyl (CDI 2) serves as a precursor for generating a stable radical anion (CDI 2˙-) using H2S as a reductant in 40% H2O-THF solution in the NIR region with stability up to >50 min. The optical, cyclic voltammetry (CV), current-voltage (I-V) and electron paramagnetic resonance (EPR) studies revealed the formation of the radical anion (CDI 2˙-). The addition of a strong oxidant NOBF4 quenches the radical anion (CDI 2˙-). The aggregation studies revealed that CDI 2 exists in the aggregated state in 40% H2O-THF solution, which points to the possibility of stabilization of the radical anion in the aggregates. The radical anion (CDI 2˙-) was explored for the detection of 58.27 pM H2O2 in aqueous medium with the naked eye colour change from green to light yellow. The biochemical assay involving the radical anion (CDI 2˙-) and glucose oxidase (GOx) enzyme can be used for the detection of 16 pM (UV-vis method) and 82.4 pM (fluorescence method) glucose. The naked eye colour change from green to light yellow (daylight) and a colorless non-fluorescent solution to a green fluorescent solution (365 nm) allow the detection of 1 nM glucose.

Coumarin-Conjugated Macromolecular Probe for Sequential Stimuli-Mediated Activation

Protein bioconjugation has emerged as one of the most valuable tools for the development of protein-based biochemical assays. Here, we report a fluorescent macromolecular material, RF16_Halo, in which the coumarin derivative RF16 is specifically conjugated onto HaloTag protein to achieve a dual-stimuli-mediated fluorescence response. RF16 is first obtained by installing a H2O2-sensitive boron cage onto the C7 hydroxy moiety of the coumarin fluorophore with a HaloTag ligand attaching to the pH-labile 1,3-dioxane moiety. Upon stimulation, RF16_Halo exhibits a sequential fluorescence response to H2O2/pH at both liquid and solid interfaces. The fluorescence of the RF16_Halo-based protein film increases linearly toward H2O2 with a higher sensitivity when compared with that of RF16. Subsequently, the H2O2-cleaved RF16_Halo presents a pH-dependent fluorescence decrease under acidic conditions. Such a stimulus-responsive fluorescence "off-on-off" multimode enables RF16_Halo to be applied as a sequential logic circuit. In addition, we evaluate the fluorescence labeling ability of RF16 to intracellular IRE1_Halo protein and demonstrate that RF16 containing the HaloTag ligand could be precisely retained in cells to track IRE1_Halo protein. Hence, we provide a unique structural design strategy to construct a fluorescence dual-responsive macromolecular probe for information encryption and protein tracking in cells.

Synthesis and Fabrication of Betulin-Derived Polysulfide and Polysulfoxide Electrospun Fibers for Fruit Preservation

Plant-derived biocompounds play a crucial role in the field of renewable materials due to their sustainability as they can be converted into monomers for polymerization, comparable to numerous monomers obtained from petroleum. In this work, betulin, a triterpene derivative with antibacterial properties obtained from birch tree bark, was esterified to produce two varieties of α,ω-diene derivatives with different lengths of methylene spacers. These derivatives were then copolymerized with 2,2'-(ethylenedioxy)diethanethiol using thiol-ene photopolymerization. We optimized and confirmed the polymerization parameters such as solvents, catalysts, and monomer concentrations. These analyses allowed for the obtainment of polysulfides with a high molar mass of up to 38.9 kg/mol under the optimized conditions. Furthermore, the polysulfides were converted into polysulfoxides by using a dilute hydrogen peroxide solution. Thermal analysis of the obtained polymers revealed excellent thermal stability (up to 300 °C) and tunable glass transition temperatures depending on their molar mass and composition. We successfully produced fibers with a diameter of approximately 3.9 μm by using the electrospinning technique. The morphology and hydrophobicity of the fibers were analyzed by using scanning electron microscopy and water contact angle analysis. Plant-derived polymeric fibers exhibited good cellular biocompatibility and broad-spectrum antibacterial activity, making them promising candidates for applications in fruit preservation.

In vivo bioluminescence imaging of labile iron in xenograft models and liver using FeAL-1, an iron-activatable form of D-luciferin

Dysregulated iron homeostasis underlies diverse pathologies, from ischemia-reperfusion injury to epithelial-mesenchymal transition and drug-tolerant "persister" cancer cell states. Here, we introduce ferrous iron-activatable luciferin-1 (FeAL-1), a small-molecule probe for bioluminescent imaging of the labile iron pool (LIP) in luciferase-expressing cells and animals. We find that FeAL-1 detects LIP fluctuations in cells after iron supplementation, depletion, or treatment with hepcidin, the master regulator of systemic iron in mammalian physiology. Utilizing FeAL-1 and a dual-luciferase reporter system, we quantify LIP in mouse liver and three different orthotopic pancreatic ductal adenocarcinoma tumors. We observed up to a 10-fold increase in FeAL-1 bioluminescent signal in xenograft tumors as compared to healthy liver, the major organ of iron storage in mammals. Treating mice with hepcidin further elevated hepatic LIP, as predicted. These studies reveal a therapeutic index between tumoral and hepatic LIP and suggest an approach to sensitize tumors toward LIP-activated therapeutics.

A novel method for synthesis of carbon dots and their applications in reactive oxygen species (ROS) and glucose detections

A simple and novel method is proposed for preparation of water-soluble fluorescent carbon dots (C-dots), which have potential to be applied in detecting reactive oxygen species (ROS). The C-dots with high fluorescence quantum yield were created by hydrothermal methods with lactose as the carbon source and tris(hydroxylmethyl)aminomethane (Tris) as the surface passivation reagent. The C-dots have some unique characteristics such as excellent biocompatibility with a broad pH working range of 5-11 and high fluorescence, which makes them especially useful in the bio-detection field. The optical properties, surface groups, and element components of the prepared C-dots have been systematically studied by fluorescence spectroscopy. This facile approach is efficient and environmentally friendly and allows large-scale production of the C-dots without any further post-treatment. The C-dots have been adopted as probes for fluorescence turn-off detection owing to their high sensitivity to the hydroxyl radical. The detection limit can reach ∼0.1 μM under optimized conditions when using hydrogen peroxide as the source for generating ROS. Moreover, when paired with glucose oxidase, these C-dots can track glucose concentrations in samples. This adaptability suggests their potential in detecting various metabolites, paving the way for practical uses in disease detection.

Non-Solvatochromic Cell Membrane-Targeted NIR Fluorescent Probe for Visualization of Polarity Abnormality in Drug-Induced Liver Injury Mice

Noninvasive visualization of liver polarity by using fluorescence imaging technology is helpful to better understand drug-induced liver injury (DILI). However, cell membrane-targeted polarity-sensitive near-infrared (NIR) fluorescent probes are still scarce. Herein, we report a non-solvatochromic cell membrane-targeted NIR small molecular probe (N-BPM-C10) for monitoring the polarity changes on cell membranes in living cells and in vivo. N-BPM-C10 exhibits polarity-dependent fluorescence around 655 nm without an obvious solvatochromic effect, which endows it with good capability for the in vivo imaging study. Moreover, it can rapidly and selectively light up the cell membranes as well as distinguish tumor cells from normal cells due to its excellent polarity-sensitive ability. More importantly, N-BPM-C10 has been successfully applied to visualize liver polarity changes in vivo, revealing the reduction of liver polarity in DILI mice. We believe that N-BPM-C10 provides a new way for the diagnosis of DILI.

Review of optical reporters of radiation effects in vivo: tools to quantify improvements in radiation delivery technique

Significance

Radiation damage studies are used to optimize radiotherapy treatment techniques. Although biological indicators of damage are the best assays of effect, they are highly variable due to biological heterogeneity. The free radical radiochemistry can be assayed with optical reporters, allowing for high precision titration of techniques.

Aim

We examine the optical reporters of radiochemistry to highlight those with the best potential for translational use in vivo, as surrogates for biological damage assays, to inform on mechanisms.

Approach

A survey of the radical chemistry effects from reactive oxygen species (ROS) and oxygen itself was completed to link to DNA or biological damage. Optical reporters of ROS include fluorescent, phosphorescent, and bioluminescent molecules that have a variety of activation pathways, and each was reviewed for its in vivo translation potential.

Results

There are molecular reporters of ROS having potential to report within living systems, including derivatives of luminol, 2'7'-dichlorofluorescein diacetate, Amplex Red, and fluorescein. None have unique specificity to singular ROS species. Macromolecular engineered reporters unique to specific ROS are emerging. The ability to directly measure oxygen via reporters, such as Oxyphor and protoporphyrin IX, is an opportunity to quantify the consumption of oxygen during ROS generation, and this translates from in vitro to in vivo use. Emerging techniques, such as ion particle beams, spatial fractionation, and ultra-high dose rate FLASH radiotherapy, provide the motivation for these studies.

Conclusions

In vivo optical reporters of radiochemistry are quantitatively useful for comparing radiotherapy techniques, although their use comes at the cost of the unknown connection to the mechanisms of radiobiological damage. Still their lower measurement uncertainty, compared with biological response assay, makes them an invaluable tool. Linkage to DNA damage and biological damage is needed, and measures such as oxygen consumption serve as useful surrogate measures that translate to in vivo use.

G-quadruplex-hemin DNAzyme functionalized nanopipettes: Fabrication and sensing application

Solid-nanopores/nanopipettes have the exquisite ability to reveal the changes in molecular volume due to the advantages of adjustable size, good rigidity and low noise. Herein, a new platform for sensing application was established based on G-quadruplex-hemin DNAzyme (GQH) functionalized gold-coated nanopipettes. In this method, GQH was immobilized on gold-coated nanopipette, which could be used as a catalyst for the reaction of H₂O₂ with 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) to promote the conversion of ABTS to ABTS⁺ ions inside gold-coated nanopipette, and the change of transmembrane ion current could be monitored in real time. At the optimal conditions, there was a correlation between the ion current and the concentration of H₂O₂ in a certain range, which could be used for the hydrogen peroxide sensing. The GQH immobilized nanopipette provides a useful platform to investigate enzymatic catalysis in confined environment, which can be used in electrocatalysis, sensing and fundamental electrochemistry.

Reactive oxygen species in biological media are they friend or foe? Major In vivo and In vitro sensing challenges

The role of Reactive Oxygen Species (ROS) on biological media has been shifting over the years, as the knowledge on the complex mechanism that lies in underneath their production and overall results has been growing. It has been known for some time that these species are associated with a number of health conditions. However, they also participate in the immunoactivation cascade process, and can have an active role in theranostics. Macrophages, for example, react to the presence of pathogens through ROS production, potentially allowing the development of new therapeutic strategies. However, their short lifetime and limited spatial distribution of ROS have been limiting factors to the development and understanding of this phenomenon. Even though, ROS have shown successful theranostic applications, e.g., photodynamic therapy, their wide applicability has been hampered by the lack of effective tools for monitoring these processes in real time. Thus the development of innovative sensing strategies for in vivo monitoring of the balance between ROS concentration and the resultant immune response is of the utmost relevance. Such knowledge could lead to major breakthroughs towards the development of more effective treatments for neurodegenerative diseases. Within this review we will present the current understanding on the interaction mechanisms of ROS with biological systems and their overall effect. Additionally, the most promising sensing tools developed so far, for both in vivo and in vitro tracking will be presented along with their main limitations and advantages. This review focuses on the four main ROS that have been studied these are: singlet oxygen species, hydrogen peroxide, hydroxyl radical and superoxide anion.

Reactive oxygen species-upregulating nanomedicines towards enhanced cancer therapy

Reactive oxygen species (ROS) play a crucial role in physiological and pathological processes, emerging as a therapeutic target in cancer. Owing to the high concentration of ROS in solid tumor tissues, ROS-based treatments, such as photodynamic therapy and chemodynamic therapy, and ROS-responsive drug delivery systems have been widely explored to powerfully and specifically suppress tumors. However, their anticancer efficacy is still hampered by the heterogeneous ROS levels, and thus comprehensively upregulating the ROS levels in tumor tissues can ensure an enhanced therapeutic effect, which can further sensitize and/or synergize with other therapies to inhibit tumor growth and metastasis. Herein, we review the recently emerging drug delivery strategies and technologies for increasing the H₂O₂, ˙OH, ¹O₂, and ˙O₂^- concentrations in cancer cells, including the efficient delivery of natural enzymes, nanozymes, small molecular biological molecules, and nanoscale Fenton-reagents and semiconductors and neutralization of intracellular antioxidant substances and localized input of mechanical and electromagnetic waves (such as ultrasound, near infrared light, microwaves, and X-rays). The applications of these ROS-upregulating nanosystems in enhancing and synergizing cancer therapies including chemotherapy, chemodynamic therapy, phototherapy, and immunotherapy are surveyed. In addition, we discuss the challenges of ROS-upregulating systems and the prospects for future studies.

Polyphenolic Boronates Inhibit Tumor Cell Proliferation: Potential Mitigators of Oxidants in the Tumor Microenvironment

Boronate-based compounds have been used in brain cancer therapy, either as prodrugs or in combination with other modalities. Boronates containing pro-luminescent and fluorescent probes have been used in mouse models of cancer. In this study, we synthesized and developed polyphenolic boronates and mitochondria-targeted polyphenolic phytochemicals (e.g., magnolol [MGN] and honokiol [HNK]) and tested their antiproliferative effects in brain cancer cells. Results show that mitochondria-targeted (Mito) polyphenolic boronates (Mito-MGN-B and Mito-HNK-B) were slightly more potent than Mito-MGN and Mito-HNK in inhibiting proliferation of the U87MG cell line. Similar proliferation results also were observed in other cancer cell lines, such as MiaPaCa-2, A549 and UACC-62. Independent in vitro experiments indicated that reactive nitrogen species (e.g., peroxynitrite) and reactive oxygen species (e.g., hydrogen peroxide) stoichiometrically react with polyphenolic boronates and Mito-polphenolic boronates, forming polyphenols and Mito-polyphenols as major products. Previous reports suggest that both Mito-MGN and Mito-HNK activate cytotoxic T cells and inhibit immunosuppressive immune cells. We propose that Mito-polyphenolic boronate-based prodrugs may be used to inhibit tumor proliferation and mitigate oxidant formation in the tumor microenvironment, thereby generating Mito-polyphenols in situ, as well as showing activity in the tumor microenvironment.

Hydrolysis-Resistant Ester-Based Linkers for Development of Activity-Based NIR Bioluminescence Probes

Activity-based sensing (ABS) probes equipped with a NIR bioluminescence readout are promising chemical tools to study cancer biomarkers owing to their high sensitivity and deep tissue compatibility. Despite the demand, there is a dearth of such probes because NIR substrates (e.g., BL660 (a NIR luciferin analog)) are not equipped with an appropriate attachment site for ABS trigger installation. For instance, our attempts to mask the carboxylic acid moiety with standard self-immolative benzyl linkers resulted in significant background signals owing to undesirable ester hydrolysis. In this study, we overcame this longstanding challenge by rationally designing a new hydrolysis-resistant ester-based linker featuring an isopropyl shielding arm. Compared to the parent, the new design is 140.5-fold and 67.8-fold more resistant toward spontaneous and esterase-mediated hydrolysis, respectively. Likewise, we observed minimal cleavage of the ester moiety when incubated with a panel of enzymes possessing ester-hydrolyzing activity. These impressive in vitro results were corroborated through a series of key experiments in live cells. Further, we showcased the utility of this technology by developing the first NIR bioluminescent probe for nitroreductase (NTR) activity and applied it to visualize elevated NTR expression in oxygen deficient lung cancer cells and in a murine model of non-small cell lung cancer. The ability to monitor the activity of this key biomarker in a deep tissue context is critical because it is associated with tumor hypoxia, which in turn is linked to drug resistance and aggressive cancer phenotypes.

Synthesis of benzylated amine-substituted xanthone derivatives and their antioxidant and anti-inflammatory activities

Oxidative stress and its constant companion, inflammation, play a critical part in the pathogenesis of many acute and chronic illnesses. The discovery of new multi-targeted drug candidates with antioxidant and anti-inflammatory properties is deemed necessary. Thus, a series of novel xanthone derivatives with halogenated benzyl (4b-4d, 4f-4h) and methoxylated benzyl groups (4e) attached to the butoxy amine substituent were synthesized in this study. The synthesized xanthone derivatives exhibited stronger antioxidant activity against H₂ O₂ scavenging than the standard drug, α-tocopherol, but weaker towards DPPH scavenging and ferrous ion chelation. Besides that, 4b-4d, 4f-4h demonstrated good anti-inflammatory activities through NO production inhibition towards lipopolysaccharide (LPS)-induced RAW 264.7 cells and showed 2-4 times stronger effects than the standard drug, diclofenac sodium. Moreover, compound 4b with two brominated benzyl groups attached to the butoxy amine substituent suppressed the production of pro-inflammatory cytokines, TNF-α and IL-1β, significantly. Structure-activity relationship elucidated that the halogenated benzylamine substituent plays an important role in contributing the antioxidant and anti-inflammatory activities of xanthones. In summary, xanthone 4b was identified as a potential lead compound to be further developed into antioxidant and anti-inflammatory drugs. Thus, further studies on the related mechanisms of action of 4b are recommended.

Activity-Based Sensing for Chemistry-Enabled Biology: Illuminating Principles, Probes, and Prospects for Boronate Reagents for Studying Hydrogen Peroxide

Activity-based sensing (ABS) offers a general approach that exploits chemical reactivity as a method for selective detection and manipulation of biological analytes. Here, we illustrate the value of this chemical platform to enable new biological discovery through a case study in the design and application of ABS reagents for studying hydrogen peroxide (H2O2), a major type of reactive oxygen species (ROS) that regulates a diverse array of vital cellular signaling processes to sustain life. Specifically, we summarize advances in the use of activity-based boronate probes for the detection of H2O2 featuring high molecular selectivity over other ROS, with an emphasis on tailoring designs in chemical structure to promote new biological principles of redox signaling.

Activity-Based Fluorescent Probes Based on Hemicyanine for Biomedical Sensing

In recent years, fluorescent probes, as an analytical tool that can target and rapidly detect analytes, have been increasingly used for applications related to medical treatment, detection, and bioimaging. Researchers are interested in hemicyanine-based fluorescent probes because of their high quantum yield, tunable spectrum characteristics, absorption and emission in the near-infrared (NIR) region, and good photo-stability. The development of these dyes and their derivatives as NIR fluorescent probes for biological applications has advanced significantly in the last ten years. This review introduces processes for making hemicyanine dyes and the methodology for creating functional activity-based fluorescent probes. A variety of hemicyanine-based probes have been systematically developed for the detection of small biomolecules in various illnesses. Finally, the potential drawbacks of hemicyanine-based functional probes, and the prospects for future research and translation into clinical medicine, are also discussed. This study is intended to provide strategies for the development and design of novel fluorescence probes.

H2O2-Activated NIR-II Fluorescent Probe with a Large Stokes Shift for High-Contrast Imaging in Drug-Induced Liver Injury Mice

Drug-induced liver injury (DILI) is the most common clinical adverse drug reaction, which is closely associated with the oxidative stress caused by overproduced reactive oxygen species. Hepatic H₂O₂, as an important biomarker of DILI, plays a crucial role in the progression of DILI. However, there remains a challenge to develop H₂O₂-activatable second near-infrared (NIR-II, 1000-1700 nm) small molecular probes with both a large Stokes shift and a long emission wavelength beyond 950 nm. Herein, we developed an activatable NIR-II fluorescent probe (IR-990) with an acceptor-π-acceptor (A-π-A) skeleton for real-time detection of H₂O₂ in vivo. In the presence of H₂O₂, nonfluorescent probe IR-990 was successfully unlocked by generating a donor-π-acceptor (D-π-A) structure and switched on intense NIR-II fluorescence, exhibiting a peak emission wavelength at 990 nm and a large Stokes shift of 200 nm. Moreover, it was able to detect H₂O₂ with high sensitivity and selectivity in vitro (LOD = 0.59 μM) and monitor the behavior of endogenous H₂O₂ in the HepG2 cell model of DILI for the first time. Notably, probe IR-990 was successfully applied in real-time imaging of endogenous H₂O₂ generation in the DILI mouse model, showing a high signal-to-background ratio of 11.3/1. We envision that IR-990 holds great potential as a powerful diagnosis tool for real-time visualization of H₂O₂ in vivo and revealing the mechanism of DILI in the future.

Constructing turn-on bioluminescent probes for real-time imaging of reactive oxygen species during cisplatin chemotherapy

Real-time imaging of reactive oxygen species (ROS) during cisplatin chemotherapy of cancer is imperative to fully reveal their functions in the biological response to cisplatin. Currently, using a bioluminescent probe for real-time imaging of a specific ROS in vivo during cisplatin chemotherapy has not been achieved. Herein, three bioluminescent probes, F Probe, N Probe and P Probe were synthesized for real-time imaging of the primary ROS, O₂^•-. They all consisted of a bioluminescent emitter _D-luciferin (_D-LH₂) and an O₂^•--recognition group, and their bioluminescent signal could be turned on in response to O₂^•-. In vitro results indicated that P Probe was the most suitable one among the three probes for detection of O₂^•-, with high sensitivity, excellent selectivity and stability. P Probe was then successfully applied for real-time imaging of O₂^•- in both cancer cells and tumors during cisplatin chemotherapy. The imaging results demonstrated that O₂^•- amount in cancer cells increased with the increasing dose of cisplatin, and that cisplatin-induced upregulation of O₂^•- level in cancer cells was upstream of the cancer-killing pathway of cisplatin. We envision that P Probe may serve as an elucidative tool to further explore the role of O₂^•- in cisplatin chemotherapy.

Development of an ATP-independent bioluminescent probe for detection of extracellular hydrogen peroxide

This work reports a new ATP-independent bioluminescent probe (bor-DTZ) for detecting hydrogen peroxide that is compatible with the Nanoluciferase enzyme. The probe is designed with an arylboronate ester protecting group appended to a diphenylterazine core via a self-immolative phenolate linker. Reaction with hydrogen peroxide reveals diphenylterazine, which can then react with Nanoluciferase to produce a detectable bioluminescent signal. Bor-DTZ shows a dose-dependent response to hydrogen peroxide and selectivity over other biologically relevant reactive oxygen species and can be applied to detect either intra- or extracellular species. We further demonstrate the ability of this platform to monitor fluxes in extracellular hydrogen peroxide in a breast cancer cell line in response to the anticancer treatment, cisplatin.

Guidelines for measuring reactive oxygen species and oxidative damage in cells and in vivo

Multiple roles of reactive oxygen species (ROS) and their consequences for health and disease are emerging throughout biological sciences. This development has led researchers unfamiliar with the complexities of ROS and their reactions to employ commercial kits and probes to measure ROS and oxidative damage inappropriately, treating ROS (a generic abbreviation) as if it were a discrete molecular entity. Unfortunately, the application and interpretation of these measurements are fraught with challenges and limitations. This can lead to misleading claims entering the literature and impeding progress, despite a well-established body of knowledge on how best to assess individual ROS, their reactions, role as signalling molecules and the oxidative damage that they can cause. In this consensus statement we illuminate problems that can arise with many commonly used approaches for measurement of ROS and oxidative damage, and propose guidelines for best practice. We hope that these strategies will be useful to those who find their research requiring assessment of ROS, oxidative damage and redox signalling in cells and in vivo.

A puromycin-dependent activity-based sensing probe for histochemical staining of hydrogen peroxide in cells and animal tissues

Hydrogen peroxide (H₂O₂) is a key member of the reactive oxygen species family of transient small molecules that has broad contributions to oxidative stress and redox signaling. The development of selective and sensitive chemical probes can enable the study of H₂O₂ biology in cell, tissue and animal models. Peroxymycin-1 is a histochemical activity-based sensing probe that responds to H₂O₂ via chemoselective boronate oxidation to release puromycin, which is then covalently incorporated into nascent proteins by the ribosome and can be detected by antibody staining. Here, we describe an optimized two-step, one-pot protocol for synthesizing Peroxymycin-1 with improved yields over our originally reported procedure. We also present detailed procedures for applying Peroxymycin-1 to a broad range of biological samples spanning cells to animal tissues for profiling H₂O₂ levels through histochemical detection by using commercially available anti-puromycin antibodies. The preparation of Peroxymycin-1 takes 9 h, the confocal imaging experiments of endogenous H₂O₂ levels across different cancer cell lines take 1 d, the dot blot analysis of mouse liver tissues takes 1 d and the confocal imaging of mouse liver tissues takes 3-4 d.

Recent Approaches to Determine Static and Dynamic Redox State-Related Parameters

Oxidative stress refers to an imbalance between oxidant and antioxidant molecules, which is usually associated with oxidative damage to biomolecules and mitochondrial malfunction. Redox state-related parameters include (1) the direct measurement of ROS, (2) the assessment of the antioxidant defense status, and (3) the analysis of the resulting oxidative damage to molecules. Directly measuring ROS appears to be the preferred method among scientists, but most ROS are extremely unstable and difficult to measure. The processes of determining both the oxidative damage to biomolecules and the antioxidant system status, although both are indirect approaches, provide a reliable method to measure oxidative stress on a given sample. Recently, the Seahorse XF and the Oroboros O2k systems have provided new insights into the redox state from a more dynamic point of view. These techniques assess mitochondrial oxidative phosphorylation function and bioenergetics on isolated mitochondria, cultured cells, or specific tissues such as permeabilized fibers. This review describes a range of methodologies to measure redox state-related parameters, their strengths, and their limitations. In conclusion, all these techniques are valid and none of them can be replaced by another. Indeed, they have the potential to complement each other for a complete evaluation of the redox state of a given sample.

Evaluation of Label-Free Confocal Raman Microspectroscopy for Monitoring Oxidative Stress In Vitro in Live Human Cancer Cells

Understanding the impact of free radicals and antioxidants in cell biology is vital; however, noninvasive nonperturbative imaging of oxidative stress remains a challenge. Here, we evaluated the ability of label-free Raman spectroscopy to monitor redox biochemical changes in antioxidant (N-acetyl-l-cysteine, NAC) and pro-oxidant (tert-butyl hydroperoxide, TBHP) environments. Cellular changes were compared to fluorescence microscopy using CellROX Orange as a marker of oxidative stress. We also investigated the influence of cell media with and without serum. Incubation of cells with NAC increased the Raman signal at 498 cm-1 from S-S disulphide stretching mode, one of the most important redox-related sensors. Exposure of cells to TBHP resulted in decreased Raman spectral signals from DNA/proteins and lipids (at 784, 1094, 1003, 1606, 1658 and 718, 1264, 1301, 1440, 1746 cm-1). Using partial least squares-discriminant analysis, we showed that Raman spectroscopy can achieve sensitivity up to 96.7%, 94.8% and 91.6% for control, NAC and TBHP conditions, respectively, with specificity of up to 93.5, 90.1% and 87.9%. Our results indicate that Raman spectroscopy can directly measure the effect of NAC antioxidants and accurately characterize the intracellular conditions associated with TBHP-induced oxidative stress, including lipid peroxidation and DNA damage.

Constructing firefly luciferin bioluminescence probes for in vivo imaging

Bioluminescence imaging (BLI) is a widely applied visual approach for real-time detecting many physiological and pathological processes in a variety of biological systems. Based on the caging strategy, lots of bioluminescent probes have been well developed. While the targets react with recognizable groups, caged luciferins liberate luciferase substrates, which react with luciferase generating a bioluminescent response. Among the various bioluminescent systems, the most widely utilized bioluminescent system is the firefly luciferin system. The H and carboxylic acid of luciferin are critically caged sites. The introduced self-immolative linker extends the applications of probes. Firefly luciferin system probes have been successfully applied for analyzing physiological processes, monitoring the environment, diagnosing diseases, screening candidate drugs, and evaluating the therapeutic effect. Here, we systematically review the general design strategies of firefly luciferin bioluminescence probes and their applications. Bioluminescence probes provide a new approach for facilitating investigation in a diverse range of fields. It inspires us to explore more robust light emission luciferin and novel design strategies to develop bioluminescent probes.

Lighting up hydrogen peroxide in living cells by a novel quinoxalinamine based fluorescent probe

Hydrogen peroxide (H₂O₂), a member of small-molecule reactive oxygen species (ROS), plays vital roles in normal physiological activities and the occurrence of many diseases. In this work, two off-on fluorescent probes, QX8A-H₂O₂ and QX9A-H₂O₂, were firstly designed for H₂O₂ detection with novel fused quinoxalines as the fluorophores and boronate moiety as the reaction sites. By comparing the optical properties, QX9A-H₂O₂ with better performance was selected for further studies. QX9A-H₂O₂ exhibited a high sensitivity to H₂O₂ with the detection limit as low as 46 nM, and displayed a good selectivity towards H₂O₂ over other reactants such as ROS, biothiols and various ions. The detection was based on the intramolecular charge transfer (ICT), proceeding through a sequential oxidative hydrolysis, 1,6-rearrangement elimination and decarboxylation process to release the fluorophore QX9A. Moreover, probe QX9A-H₂O₂ was cell permeable and was successfully employed in both exogenous and endogenous H₂O₂ imaging in living cells.

Chemiluminescence Measurement of Reactive Sulfur and Nitrogen Species

Significance: Reactive sulfur and nitrogen species such as hydrogen sulfide (H₂S) and nitric oxide (NO^•) are ubiquitous cellular signaling molecules that play central roles in physiology and pathophysiology. A deeper understanding of these signaling pathways will offer new opportunities for therapeutic treatments and disease management. Recent Advances: Chemiluminescence methods have been fundamental in detecting and measuring biological reactive sulfur and nitrogen species, and new approaches are emerging for imaging these analytes in living intact specimens. Ozone-based and luminol-based chemiluminescence methods have been optimized for quantitative analysis of hydrogen sulfide and nitric oxide in biological samples and tissue homogenates, and caged luciferin and 1,2-dioxetanes are emerging as a versatile approach for monitoring and imaging reactive sulfur and nitrogen species in living cells and animal models. Critical Issues: This review article will cover the major chemiluminescence approaches for detecting, measuring, and imaging reactive sulfur and nitrogen species in biological systems, including a brief history of the development of the most established approaches and highlights of the opportunities provided by emerging approaches. Future Directions: Emerging chemiluminescence approaches offer new opportunities for monitoring and imaging reactive sulfur and nitrogen species in living cells, animals, and human clinical samples. Widespread adoption and translation of these approaches, however, requires an emphasis on rigorous quantitative methods, reproducibility, and effective technology transfer. Antioxid. Redox Signal. 36, 337-353.

Connecting the Dynamics and Reactivity of Arylboronic Acids to Emergent and Stimuli-Responsive Material Properties

Over the past two decades, arylboronic acid-functionalized biomaterials have been used in a variety of sensing and stimuli-responsive scaffolds. Their diverse applications result from the diverse reactivity of arylboronic acids,...

Recent advances in self-immolative linkers and their applications in polymeric reporting systems

Interest in self-immolative chemistry has grown over the past decade with more research groups harnessing the versatility to control the release of a compound from a larger chemical entity, given...

Small-Molecule Prodrug Nanoassemblies: An Emerging Nanoplatform for Anticancer Drug Delivery

The antitumor efficiency and clinical translation of traditional nanomedicines is mainly restricted by low drug loading, complex preparation technology, and potential toxicity caused by the overused carrier materials. In recent decades, small-molecule prodrug nanoassemblies (SMP-NAs), which are formed by the self-assembly of prodrugs themselves, have been widely investigated with distinct advantages of ultrahigh drug-loading and negligible excipients-trigged adverse reaction. Benefited from the simple preparation process, SMP-NAs are widely used for chemotherapy, phototherapy, immunotherapy, and tumor diagnosis. In addition, combination therapy based on the accurate co-delivery behavior of SMP-NAs can effectively address the challenges of tumor heterogeneity and multidrug resistance. Recent trends in SMP-NAs are outlined, and the corresponding self-assembly mechanisms are discussed in detail. Besides, the smart stimuli-responsive SMP-NAs and the combination therapy based on SMP-NAs are summarized, with special emphasis on the structure-function relationships. Finally, the outlooks and potential challenges of SMP-NAs in cancer therapy are highlighted.

Lectin-Triggered Aggregation of Glyco-Gold Nanoprobes for Activity-based Sensing of Hydrogen Peroxide by the Naked Eye

The purpose of this study was to develop a colorimetric assay for detecting hydrogen peroxide (H₂ O₂ ) through a combination of using an aryl boronate (AB) derivative and gold nanoparticles (AuNPs). The unique optical property of AuNPs is applied to design a detection probe. The aggregation of AuNPs could be directly observed as a color change by the naked eye. A mannoside-boronate-sulfide (MBS) ligand was designed that contains an arylboronate (AB), a mannoside, and a thiol group. The thiol group bonds covalently with the surface of AuNPs to obtain MBS@AuNPs. The mannoside moiety recognizes concanavalin A (Con A), a lectin with four carbohydrate recognition sites that can specifically recognize the non-reducing end of an α-D-mannoside or α-D-glucoside structure. The AB structure on MBS first reacts with H₂ O₂ and then inserts an oxygen atom in the B-H bond, which triggers intramolecular electron rearrangement to cleave the covalent bond, resulting in a MBSt mixture. The MBS or MBSt is then modified to citrate-coated AuNPs (c-AuNPs) to have MBS@AuNPs or MBSt@AuNPs. When the MBS@AuNPs are incubated with Con A, the Con A recognizes multiple mannosides on the surface of the MBS@AuNPs. Subsequently, the MBS@AuNPs aggregate and the solution's color changes from red to purple, but this color change does not occur in the case of MBSt@AuNPs. The phenomenon can be observed by the naked eye.

A sequentially activated bioluminescent probe for observation of cellular H2O2 production induced by cysteine

We report herein a caged luciferin probe Cy-Hy as a sequentially activated probe to selectively and sensitively sense L-Cys and H₂O₂. The probe displayed fluorescence and bioluminescence responses toward the two analytes. Utilizing the present probe, cellular excess L-Cys-induced H₂O₂ up-regulation was observed for the first time in living MDA-MB-231 cells.

Detection of Lysyl Oxidase Activity in Tumor Extracellular Matrix Using Peptide-Functionalized Gold Nanoprobes

Simple Summary

Although various malignant tumors express high levels of lysyl oxidase (LOX) and though its role in tumor progression is well-defined, there is a lack of sensing techniques to target LOX. This study highlights the application of peptide-functionalized gold nanoprobes for sensing the LOX levels in tumor microenvironments. The gold nanoparticles (AuNPs) in these nanoprobes aggregate upon exposure to LOX, resulting in a red shift of the surface plasmon resonance peak, accompanied by a characteristic color change. This colorimetric assay based on peptide-functionalized AuNP sensitively detects LOX secreted from various cancer cells not only in vitro but also in the tissue extract. In this study, the suggested analytical approach demonstrated high specificity to LOX and did not show any color change in the presence of other enzymes.

Abstract

High LOX levels in the tumor microenvironment causes the cross-linking of extracellular matrix components and increases the stiffness of tumor tissue. Thus, LOX plays an important role in tumorigenesis and in lowering the tumor response to anticancer drugs. Despite comprehensive efforts to identify the roles of LOX in the tumor microenvironment, sensitive and accurate detection methods have not yet been established. Here, we suggest the use of gold nanoparticles functionalized with LOX-sensitive peptides (LS-AuNPs) that aggregate upon exposure to LOX, resulting in a visual color change. LOX-sensitive peptides (LS-peptides) contain lysine residues that are converted to allysine in the presence of LOX, which is highly reactive and binds to adjacent allysine, resulting in the aggregation of the AuNPs. We demonstrated that the synthesized LS-AuNPs are capable of detecting LOX sensitively, specifically both in vitro and in the tissue extract. Moreover, the suggested LS-AuNP-based assay is more sensitive than commonly employed assays or commercially available kits. Therefore, the LS-AuNPs developed in this study can be used to detect LOX levels and can be further used to predict the stiffness or the anticancer drug resistance of the tumor.

A microtubule-localizing activity-based sensing fluorescent probe for imaging hydrogen peroxide in living cells

Hydrogen peroxide (H₂O₂) is a major reactive oxygen species (ROS) in living systems with broad roles spanning both oxidative stress and redox signaling. Indeed, owing to its potent redox activity, regulating local sites of H₂O₂ generation and trafficking is critical to determining downstream physiological and/or pathological consequences. We now report the design, synthesis, and biological evaluation of Microtubule Peroxy Yellow 1 (MT-PY1), an activity-based sensing fluorescent probe bearing a microtubule-targeting moiety for detection of H₂O₂ in living cells. MT-PY1 utilizes a boronate trigger to show a selective and robust turn-on response to H₂O₂ in aqueous solution and in living cells. Live-cell microscopy experiments establish that the probe co-localizes with microtubules and retains its localization after responding to changes in levels of H₂O₂, including detection of endogenous H₂O₂ fluxes produced upon growth factor stimulation. This work adds to the arsenal of activity-based sensing probes for biological analytes that enable selective molecular imaging with subcellular resolution.

Dual-locked spectroscopic probes for sensing and therapy

Optical imaging probes allow us to detect and uncover the physiological and pathological functions of an analyte of interest at the molecular level in a non-invasive, longitudinal manner. By virtue of simplicity, low cost, high sensitivity, adaptation to automated analysis, capacity for spatially resolved imaging and diverse signal output modes, optical imaging probes have been widely applied in biology, physiology, pharmacology and medicine. To build a reliable and practically/clinically relevant probe, the design process often encompasses multidisciplinary themes, including chemistry, biology and medicine. Within the repertoire of probes, dual-locked systems are particularly interesting as a result of their ability to offer enhanced specificity and multiplex detection. In addition, chemiluminescence is a low-background, excitation-free optical modality and, thus, can be integrated into dual-locked systems, permitting crosstalk-free fluorescent and chemiluminescent detection of two distinct biomarkers. For many researchers, these dual-locked systems remain a 'black box'. Therefore, this Review aims to offer a 'beginner's guide' to such dual-locked systems, providing simple explanations on how they work, what they can do and where they have been applied, in order to help readers develop a deeper understanding of this rich area of research.

Portable bioluminescent platform for in vivo monitoring of biological processes in non-transgenic animals

Bioluminescent imaging (BLI) is one of the most powerful and widely used preclinical imaging modalities. However, the current technology relies on the use of transgenic luciferase-expressing cells and animals and therefore can only be applied to a limited number of existing animal models of human disease. Here, we report the development of a “portable bioluminescent” (PBL) technology that overcomes most of the major limitations of traditional BLI. We demonstrate that the PBL method is capable of noninvasive measuring the activity of both extracellular (e.g., dipeptidyl peptidase 4) and intracellular (e.g., cytochrome P450) enzymes in vivo in non-luciferase-expressing mice. Moreover, we successfully utilize PBL technology in dogs and human cadaver, paving the way for the translation of functional BLI to the noninvasive quantification of biological processes in large animals. The PBL methodology can be easily adapted for the noninvasive monitoring of a plethora of diseases across multiple species.

Bioluminescence imaging tends to rely on transgenic luciferase-expressing cells and animals. Here the authors report a portable bioluminescent system to non-invasively measure intra- and extracellular enzymes in vivo in non-transgenic animals which do not express luciferase.

Stimuli-responsive nanoparticles based on poly acrylic derivatives for tumor therapy

Serve side effects caused by discriminate damage of chemotherapeutic drugs to normal cell and cancer cells remain a main obstacle in clinic. Hence, continuous efforts have been made to find ways to effectively enhance drug delivery and reduce side effects. Recent decades have witnessed impressive progresses in fighting against cancer, with improved understanding of tumor microenvironment and rapid development in nanoscale drug delivery system (DDS). Nanocarriers based on biocompatible materials provide possibilities to improve antitumor efficiency and minimize off-target effects. Among all kinds of biocompatible materials applied in DDS, polymeric acrylic derivatives such as poly(acrylamide), poly(acrylic acid), poly(N-isopropylacrylamide) present inherent biocompatibility and stimuli-responsivity, and relatively easy to be functionalized. Furthermore, nanocarrier based on polymeric acrylic derivatives have demonstrated high drug encapsulation, improved uptake efficiency, prolonged circulation time and satisfactory therapeutic outcome in tumor. In this review, we aim to discuss recent progress in design and development of stimulus-responsive poly acrylic polymer based nanocarriers for tumor targeting drug delivery.

Molecular Design of d-Luciferin-Based Bioluminescence and 1,2-Dioxetane-Based Chemiluminescence Substrates for Altered Output Wavelength and Detecting Various Molecules

Optical imaging including fluorescence and luminescence is the most popular method for the in vivo imaging in mice. Luminescence imaging is considered to be superior to fluorescence imaging due to the lack of both autofluorescence and the scattering of excitation light. To date, various luciferin analogs and bioluminescence probes have been developed for deep tissue and molecular imaging. Recently, chemiluminescence probes have been developed based on a 1,2-dioxetane scaffold. In this review, the accumulated findings of numerous studies and the design strategies of bioluminescence and chemiluminescence imaging reagents are summarized.