"Turn-on" Fluorescent Aptasensor Based on AIEgen Labeling for the Localization of IFN-γ in Live Cells

Aggregation-induced emission-based aptasensors for the detection of various targets: Recent progress

The advancement of aptasensors utilizing aggregation-induced emission (AIE) has progressed remarkably in recent years, owing to various unique benefits provided by aggregation-induced emission luminogens (AIEgens) as a novel category of fluorescent substances and aptamers as exceptional recognition components. AIE refers to a photophysical phenomenon identified in certain luminogens that show minimal or absent emission in dilute solutions, yet display considerable emission when in aggregate or solid states. Fluorescent sensing is an effective technique for the detection of various targets; however, many traditional dyes frequently demonstrate an aggregation-caused quenching (ACQ) effect in solid form, which limits their applicability on a larger scale. In contrast, fluorescent probes that leverage AIE characteristics have garnered considerable interest, owing to their elevated fluorescence quantum yields and ease of fabrication. This review discusses the application of various AIEgens in the design of diverse sensitive and selective AIE-based aptasensors for monitoring various targets, with a particular focus on recent advances. The AIE-based aptasensors exploit the supreme affinity of the aptamers to their targets and the remarkable properties of AIEgen, including its photostability and high quantum yield, and the interaction between AIEgen and DNA. The objective is to acquaint researchers with the various categories of materials exhibiting AIE characteristics and their potential applications in the creation of different aptasensors, enabling them to introduce novel kinds of innovative AIEgens and AIE-integrated aptasensors.

Development of a light-initiated chemiluminescent assay platform for rapid detection of multiple inflammatory biomarkers

The accurate and timely detection of inflammatory biomarkers, including C-reactive protein (CRP), interferon-γ (IFN-γ), and procalcitonin (PCT), is critical for the diagnosis and monitoring of various diseases. Traditional immunoassays often suffer from complex workflows, long incubation times, and limited multiplexing capabilities, which restrict their utility in high-throughput or point-of-care applications. To overcome these challenges, we developed a light-initiated chemiluminescent assay (LICA) platform, leveraging the synthesis and functionalization of photosensitive microspheres and luminescent microspheres encapsulated with β-diketonate-Eu(III) complexes for the rapid detection of CRP, IFN-γ, and PCT. The LICA platform exhibited excellent analytical performances, achieving detection limits of 6.2 ng mL-1 for CRP, 0.32 pg mL-1 for IFN-γ, and 0.012 ng mL-1 for PCT, alongside remarkable specificity and reproducibility. We further validated the LICA platform by analyzing clinical blood samples, and the results were in excellent agreement with those obtained using well-established clinical methods, with a correlation coefficient exceeding 0.9940. Mechanistic investigations revealed that singlet oxygen is the key reactive species driving luminescence, while efficient intramolecular energy transfer from the ligands to the Eu(III) metal center plays a critical role in the emission of luminescence. Our findings underscore the potential of the LICA platform as a transformative tool for the detection of multiple inflammatory biomarkers, particularly in scenarios requiring rapid, multiplexed detection of inflammatory biomarkers.

FADH2-mediated radical polymerization amplification for microRNA-21 detection

For early diagnosis of disease, ultrasensitive mircoRNA-21 detection has considerable potential. In this paper, an ultra-sensitive fluorescence detection method for microRNA was developed by atom transfer radical polymerization (ATRP). This ATRP reaction was first initiated by using flavin mononucleotide (FADH2). The DNA probe 1 modified with amino group was fixed on the magnetic nanoparticle Fe3O4, and microRNA-21 was added to form the probe 1-microRNA-21. Another carboxy-modified DNA 2 forms a sandwich structure with the bound microRNA-21. Two terminally modified DNA types are used as microRNA probes, using complementary base pairing to form a stable super-sandwich structure between the DNA probe and the microRNA. Under optimal conditions, microRNA was detected in PBS buffer with a detection limit of 0.19 fM. And even in 10% of human serum, microRNA-21 can be detected with a detection limit of 47.8 fM. Results show that this method has high selectivity, efficiency and stability, which broad application prospect in microRNA ultra-sensitive detection.

Detecting Disruption of HER2 Membrane Protein Organization in Cell Membranes with Nanoscale Precision

The spatiotemporal organization of proteins within the cell membrane can affect numerous biological functions, including cell signaling, communication, and transportation. Deviations from normal spatial arrangements have been observed in various diseases, and a better understanding of this process is a key stepping stone to advancing development of clinical interventions. However, given the nanometer length scales involved, detecting these subtle changes has primarily relied on complex super-resolution and single-molecule imaging methods. In this work, we demonstrate an alternative fluorescent imaging strategy for detecting protein organization based on a material that exhibits a unique photophysical behavior known as aggregation-induced emission (AIE). Organic AIE molecules have an increase in emission signal when they are in close proximity, and the molecular motion is restricted. This property simultaneously addresses the high background noise and low detection signal that limit conventional widefield fluorescent imaging. To demonstrate the potential of this approach, the fluorescent molecule sensor is conjugated to a human epidermal growth factor receptor 2 (HER2)-specific antibody and used to investigate the spatiotemporal behavior of HER2 clustering in the membrane of HER2-overexpressing breast cancer cells. Notably, the disruption of HER2 clusters in response to an FDA-approved monoclonal antibody therapeutic (Trastuzumab) is successfully detected using a simple widefield fluorescent microscope. While the sensor demonstrated here is optimized for sensing HER2 clustering, it is an easily adaptable platform. Moreover, given the compatibility with widefield imaging, the system has the potential to be used with high-throughput imaging techniques, accelerating investigations into membrane protein spatiotemporal organization.

Aggregation-Induced Emission (AIE), Life and Health

Light has profoundly impacted modern medicine and healthcare, with numerous luminescent agents and imaging techniques currently being used to assess health and treat diseases. As an emerging concept in luminescence, aggregation-induced emission (AIE) has shown great potential in biological applications due to its advantages in terms of brightness, biocompatibility, photostability, and positive correlation with concentration. This review provides a comprehensive summary of AIE luminogens applied in imaging of biological structure and dynamic physiological processes, disease diagnosis and treatment, and detection and monitoring of specific analytes, followed by representative works. Discussions on critical issues and perspectives on future directions are also included. This review aims to stimulate the interest of researchers from different fields, including chemistry, biology, materials science, medicine, etc., thus promoting the development of AIE in the fields of life and health.

Detection of Pb2+ in Tea Using Aptamer Labeled with AIEgen Nanospheres Based on MOFs Sensors

Tea is an important economic crop and health beverage in China. The presence of heavy metal ions in tea poses a significant threat to public health. Here, we prepared an aptamer biosensor labelled with AIEgen nanospheres to detect Pb²⁺ in tea. The dsDNA modified by amino and phosphoric acid was combined with the carboxylated AIEgen NPs to form AIEgen-DNA with a fluorescence group, which was then fixed to the surface of Zr-MOFs to quench the fluorescence of AIEgen NPs. At the same time, PEG was added to remove nonspecific adsorption. Then Pb²⁺ was added to cut the DNA sequences containing the cutting sites, and AIEgen NPs and part of the DNA sequences were separated from the Zr-MOFs surface to recover the fluorescence. By comparing the fluorescence changes before and after adding Pb²⁺, the detection limit of Pb²⁺ can reach 1.70 nM. The fluorescence sensor was applied to detect Pb²⁺ in tea, and the detection results showed that the tea purchased on the market did not contain the concentration of Pb²⁺ within the detection range. This study provides new insights into monitoring food and agriculture-related pollutants based on fluorescent biosensors.

Fluorescence Aptasensor of Tuberculosis Interferon-γ in Clinical Samples Regulated by Steric Hindrance and Selective Identification

Although there are many interferon gamma (IFN-γ)-based tools for tuberculosis (TB) diagnosis, they are less sensitive and laborious. Here, we developed an IFN-γ aptasensor using pyrophosphate-cerium coordination polymeric nanoparticles (PPi-Ce CPNs) as signal reporters and a double-stranded DNA as a probe. The sensor was realized by sterically regulating the polymerization elongation of terminal deoxynucleotidyl transferase (TdT) and the selective recognition reaction of PPi-Ce CPNs. This method employs PPi-Ce CPNs to selectively identify Cu²⁺ and polyT-templated copper nanoparticles (Cu NPs), as well as a TdT-assisted amplification technique. Our data showed that under optimized experimental conditions, a limit of detection of as low as 0.25 fg/mL was achieved, with a linear range of 1-100 fg/mL, and a good target protein specificity. The detection sensitivity was an order of magnitude higher than that observed with Cu NPs when used as signal reporters. This IFN-γ quantification technique was further validated in clinical samples using 57 clinical TB patients (22 negative and 35 positive). Our findings agreed with those from enzyme-linked immunosorbent assay, GeneXpert MTB/rifampin assay, and polymerase chain reaction detection of TB-DNA and those from clinical imaging techniques. Therefore, our analytical system may provide an additional and more sensitive tool for the early diagnosis of TB.

Peptide-Conjugated Aggregation-Induced Emission Fluorogenic Probe for Glypican-3 Protein Detection and Hepatocellular Carcinoma Cells Imaging

Hepatocellular carcinoma (HCC) is a malignant tumor with high morbidity and mortality on a global scale, and the development of accurate detection and imaging methods for HCC cells is urgently needed. Herein, by connecting peptide L5, which can specifically bind to the overexpressed Glypican-3 (GPC-3) protein of HCC cells with aggregation-induced emission (AIE) moiety ammonium cation-functionalized 9,10-distyrylanthracene (NDSA) via the “click” reaction, we synthesized a fluorescent probe NDSA-L5. In an aqueous solution, the probe shows weak emission, whereas, in the presence of the GPC-3 protein, bright fluorescence can be obtained since NDSA-L5 binds to the GPC-3 protein, leading to the restricted intramolecular movement of AIE-active NDSA-L5. The imaging and flow cytometry experiments demonstrate that the NDSA-L5 probe can rapidly accumulate in the subcutaneous HCC cells and liver tumor tissue and shows a potential application in early detection and surgical navigation for HCC cancer.

Interferon-γ detection in point of care diagnostics: Short review

Interferon (IFN)-γ is a cytokine secreted by immune cells. The elevated levels of IFN-γ are an early indicator of multiple diseases such as tuberculosis and autoimmune diseases. This short review focuses on different sensing methods based on optical, electrochemical, and mechanical principles. We explain how specific biorecognition molecules such as antibodies and aptamers are employed in the sensing methods. We also compare different surface functionalization methods and their details. Although the review gives an overview of only IFN-γ sensing, the same strategies can be applied to sensing other analytes with appropriate modifications.

Aptamer based probes for living cell intracellular molecules detection

Biosensors have been employed for monitoring and imaging biological events and molecules. Sensitive detection of different biomolecules in vivo can reflect the changes of physiological conditions in real-time, which is of great significance for the diagnosis and treatment of diseases. The detection of intracellular molecules concentration change can indicate the occurrence and development of disease. But the analysis process of the existing detection methods, such as Western blot detection of intracellular protein, polymerase chain reaction (PCR) technique quantitative analysis of intracellular RNA and DNA, usually need to extract the cell lysis which is complex and time-consuming. Fluorescence bioimaging enables in situ monitoring of intracellular molecules in living cells. By combining the specificity of aptamer for intracellular molecules binding, and biocompatibility of fluorescent materials and nanomaterials, biosensors with different nanostructures have been developed to enter into living cells for analysis. This review summarizes the fluorescence detection methods based on aptamer for intracellular molecules detection. The principles, limit of detection, advantages, and disadvantages of different platforms for intracellular molecular fluorescent response are summarized and reviewed. Finally, the current challenges and future developments were discussed and proposed.

Recent Advances in Aptasensor for Cytokine Detection: A Review

Cytokines are proteins secreted by immune cells. They promote cell signal transduction and are involved in cell replication, death, and recovery. Cytokines are immune modulators, but their excessive secretion causes uncontrolled inflammation that attacks normal cells. Considering the properties of cytokines, monitoring the secretion of cytokines in vivo is of great value for medical and biological research. In this review, we offer a report on recent studies for cytokine detection, especially studies on aptasensors using aptamers. Aptamers are single strand nucleic acids that form a stable three-dimensional structure and have been receiving attention due to various characteristics such as simple production methods, low molecular weight, and ease of modification while performing a physiological role similar to antibodies.

Cytokines: From Clinical Significance to Quantification

Cytokines are critical mediators that oversee and regulate immune and inflammatory responses via complex networks and serve as biomarkers for many diseases. Quantification of cytokines has significant value in both clinical medicine and biology as the levels provide insights into physiological and pathological processes and can be used to aid diagnosis and treatment. Cytokines and their clinical significance are introduced from the perspective of their pro- and anti-inflammatory effects. Factors affecting cytokines quantification in biological fluids, native levels in different body fluids, sample processing and storage conditions, sensitivity to freeze-thaw, and soluble cytokine receptors are discussed. In addition, recent advances in in vitro and in vivo assays, biosensors based on different signal outputs and intracellular to extracellular protein expression are summarized. Various quantification platforms for high-sensitivity and reliable measurement of cytokines in different scenarios are discussed, and commercially available cytokine assays are compared. A discussion of challenges in the development and advancement of technologies for cytokine quantification that aim to achieve real-time multiplex cytokine analysis for point-of-care situations applicable for both biomedical research and clinical practice are discussed.

Microfluidic Magnetic Analyte Delivery Technique for Separation, Enrichment, and Fluorescence Detection of Ultratrace Biomarkers

A microfluidic magnetic analyte delivery (μMAD) technique was developed to realize sample preparation and ultrasensitive biomarker detection. A simply designed microfluidic device was employed to carry out this technique, including a poly(dimethylsiloxane)-glass hybrid microchip having four straight rectangular channels and a permanent magnet. In the μMAD process, functionalized magnetic beads (MBs) were used to recognize and isolate analytes from a complex sample matrix, deliver analytes into tiny microchannels, and preconcentrate analytes in the magnetic trapping/detection region for in situ fluorescence detection. In the feasibility study and sensitivity optimization, horseradish peroxidase-labeled MBs were used, and critical parameters for the signal amplification performance of μMAD were carefully evaluated. At optimized conditions, a sensitivity improvement of at least 2 orders of magnitude was achieved. As a proof of concept, μMAD was combined with the enzyme-linked immunosorbent assay (ELISA), while carcinoembryonic antigen (CEA), prostate-specific antigen (PSA), and interleukin 6 (IL-6) were selected as model biomarkers. The limits of detection (LODs) of μMAD-ELISA were as low as 0.29 pg/mL for CEA, 0.047 pg/mL for PSA, and 0.021 pg/mL for IL-6, which corresponded to an over 200-fold reduction compared to their commercial ELISA results. Meanwhile, μMAD-ELISA revealed high selectivity and reproducibility. In clinical sample analysis, good accuracy was acquired for human serum analysis relative to commercial ELISA kits, and satisfied recoveries of 85.1-102% with RSDs of 1.7-9.8% for IL-6 and 84.7-113% with RSDs of 3.2-8.3% for interferon-γ were obtained. This ultrasensitive and easy operation technique provides a valuable approach for trace-level biomarker detection for practical applications.

Recent Advances in Two-Photon AIEgens and Their Application in Biological Systems

Two-photon fluorescence imaging technology has the advantages of high light stability, little light damage, and high spatiotemporal resolution, which make it a powerful biological analysis method. However, due to the high concentration or aggregation state of traditional organic light-emitting molecules, the fluorescence intensity is easily reduced or disappears completely, and is not conducive to optimal application. The concept of aggregation-induced emission (AIE) provides a solution to the problem of aggregation-induced luminescence quenching (ACQ), and realizes the high fluorescence quantum yield of luminescent molecules in the aggregation state. In addition, two-photon absorption properties can readily be improved just by increasing the loading content of AIE fluorogen (AIEgen). Therefore, the design and preparation of two-photon fluorescence probes based on AIEgen to achieve high-efficiency fluorescence imaging in vitro/in vivo has become a major research hotspot. This review aims to summarize representative two-photon AIEgens based on triphenylamine, tetraphenylethene, quinoline, naphthalene and other new structures from the past five years, and discuss their great potential in bioimaging applications.

π-Extended Tetraphenylethylene Containing a Dicyanovinyl Group as an Ideal Fluorescence Turn-On and Naked-Eye Color Change Probe for Hydrazine Detection

A π-extended tetraphenylethylene derivative 1 was developed as a fluorescent "turn-on" and "naked-eye" color change probe for hydrazine detection. Probe 1 was composed of the representative AIE luminogen (AIEgen), tetraphenylethylene, and a dicyanovinyl group was adopted for hydrazine recognition. Upon exposure of hydrazine, probe 1 immediately gave a significant aggregation-induced emission around 575 nm and excellent photostability. A naked-eye color change was also observed from red to yellow. Moreover, probe 1 was simply coated with a glass-backed silica gel-coated thin-layer chromatography plate, showing rapid and on-site detection of hydrazine vapor.

An enzyme-responsive and photoactivatable carbon-monoxide releasing molecule for bacterial infection theranostics

Infections caused by pathogenic bacteria, especially the drug-resistant bacteria, are posing a devastating threat to public health, which underscores the urgent needs for advanced strategies to effectively prevent and treat these intractable issues. Here we report a feasible and effective theranostic platform based on an enzyme-sensitive and photoactivatable carbon monoxide releasing molecule (CORM-Ac) for the successive detection and elimination of bacterial infection. The extracellular bacterial lipase can trigger the excited state intramolecular proton transfer (ESIPT) via elimination of the ester group in CORM-Ac, thus providing a fluorescence switch for an early warning of infection. Subsequently, the potent bactericidal therapy against the model bacterial strains, Staphylococcus aureus (S. aureus) and notorious methicillin-resistant Staphylococcus aureus (MRSA), was readily realized via photoinduced release of CO. In addition, the CORM-Ac and CORM showed good biocompatibility within a wide range of concentrations. The results of an infected animal wound test also demonstrated that the CORM-Ac-loaded gauze was effective in indicating the wound infection and accelerating the wound healing via the photoinduced CO release. The simplicity, functional integration, good biocompatibility and broad adaptability make CORM-Ac very attractive for bacterial theranostic applications.

Development of a dendrimer PAMAM‑based gold biochip for rapid and sensitive detection of endogenous IFN‑γ and anti‑IFN‑γ IgG in patients with hemophagocytic lymphohistiocytosis

Hemophagocytic lymphohistiocytosis (HLH) is a rare but severe disease characterized by immune hyperactivation and cytokine storm. Given the high mortality rate of HLH, there is a need for more effective diagnostic tools and treatments. The present study developed a dendrimer‑based protein biochip for rapid, sensitive and simultaneous detection of serum interferon (IFN)‑γ and endogenous anti‑IFN‑γ antibody (Ab) in patients with HLH. A gold biochip was modified with 1, 4‑phenylene diisothiocyanate (PDITC), polyamidoamine (PAMAM) or PDITC‑activated PAMAM. The optimal immobilization concentration for Ab capture and the reaction concentration for detecting Ab on the PDITC‑activated PAMAM‑modified biochip were 6.25 and 3.12 µg/ml, respectively; the limit of detection of IFN‑γ protein was 50 pg/ml. The efficiency of the protein‑probed biochip in detecting IFN‑γ and anti‑IFN‑γ Ab in serum samples from 77 patients with HLH was evaluated; the positive rates for IFN‑γ and anti‑IFN‑γ IgG Ab were 63.6% (49/77) and 61.0% (47/77), respectively. The present results demonstrated that the PDITC‑activated PAMAM‑modified biochip might be a sensitive tool for the specific detection of IFN‑γ and anti‑IFN‑γ Ab in serum, and might have clinical applicability for the diagnosis of HLH.

Design a fluorometric aptasensor based on CoOOH nanosheets and carbon dots for simultaneous detection of lysozyme and adenosine triphosphate

Simultaneous detection of biomarkers and biomolecules with great analytical performance still is challenging. A simple fluorometric dual-functional aptasensor was designed to detect Lysozyme (LYS) and adenosine triphosphate (ATP) as models of a protein and a small molecule simultaneously. The sensing principle of the aptasensor is based on the interactions between cobalt oxyhydroxide CoOOH nanosheets as fluorescence quencher and carbon dots (CDs) as fluorophores. The aptamer labeled with CDs was able to assemble on CoOOH nanosheets and consequently, the fluorescence signal was quenched. With addition target analytes to the system, the aptamers folded around of targets with a strong and specific affinity. Therefore, the labeled aptamer with CDs was detached from CoOOH nanosheets and the fluorescence signal was restored. The fluorescence spectral overlap of these two CDs is the main limitation for the simultaneous analysis. The least squared support vector machine (LS-SVM) was applied to resolve this problem. Under optimal conditions, when LS-SVR was used, detection limits were found 4.0 and 1.8 nmol L^-1 for ATP and LYS. The parallel biosensor is capable of monitoring ATP and LYS levels in the biological samples with satisfactory results.

Synthesis of the cationic fluorescent probes for the detection of anionic surfactants by electrostatic self-assembly

Anionic surfactants were widespread used in car cleaning agents, household detergents, agricultural and industrial processes, and considered as a major source of environmental pollutant. Therefore, it is necessary to develop a fast, simple, highly selective and sensitive probe for the detection of anionic surfactants. Here, we synthesized two aggregation induced emission (AIE)-active molecules 4,4',4″,4‴-(ethene-1,1,2,2-tetrayltetrakis(benzene-4,1-diyl))tetrakis (1-(4-bromobenzyl)pyridin-1-ium) bromide (TPE-Br) and 4,4',4″,4‴-(ethene-1,1,2,2-trayltetrakis(benzene-4,1-diyl))tetrakis(1-methylpyridin-1-ium)iodide (TPE-I), which were then applied as fluorescence probes for detecting sodium dodecyl sulfate (SDS) with high selectivity and sensitivity. In the presence of SDS, a multi-fold fluorescence emission intensity enhancement was observed in both two probes (TPE-Br and TPE-I) due to the electrostatic self-assembly of AIE molecular. The limits of detection are 71.5 and 120 nM for TPE-Br and TPE-I, respectively. This study may provide a new strategy for environmental monitoring by AIE-based fluorescent probe.

Adaptive in vivo device for theranostics of inflammation: Real-time monitoring of interferon-γ and aspirin

Cytokines mediate and control immune and inflammatory responses. Complex interactions exist among cytokines, inflammation, and the innate and adaptive immune responses in maintaining homeostasis, health, and well-being. On-demand, local delivery of anti-inflammatory drugs to target tissues provides an approach for more effective drug dosing while reducing the adverse effects of systemic drug delivery. This work demonstrates a proof-of-concept theranostic approach for inflammation based on analyte-kissing induced signaling, whereby a drug (in this report, aspirin) can be released upon the detection of a target level of a proinflammatory cytokine (i.e., interferon-γ (IFN-γ)) in real time. The structure-switching aptamer-based biosensor described here is capable of quantitatively and dynamically detecting IFN-γ both in vitro and in vivo with a sensitivity of 10 pg mL^-1. Moreover, the released aspirin triggered by the immunoregulatory cytokine IFN-γ is able to inhibit inflammation in a rat model, and the release of aspirin can be quantitatively controlled. The data reported here provide a new and promising strategy for the in vivo detection of proinflammatory cytokines and the subsequent therapeutic delivery of anti-inflammatory molecules. This universal theranostic platform is expected to have great potential for patient-specific personalized medicine. STATEMENT OF SIGNIFICANCE: We developed an adaptive in vivo sensing device whereby a drug, aspirin, can be released upon the detection of a proinflammatory cytokine, interferon-γ (IFN-γ), in real time with a sensitivity of 10 pg mL^-1. Moreover, the aspirin triggered by IFN-γ depressed inflammation in the rat model and was delivered indirectly through blood and cerebrospinal fluid or directly to the inflammation tissue or organ without adverse gastrointestinal effects observed in the liver and kidney. We envision that, for the first time, patients with chronic inflammatory disease can receive the right intervention and treatment at the right time. Additionally, this technology may empower patients to monitor their personalized health and disease management program, allowing real-time diagnostics, disease monitoring, and precise and effective treatments.

Near-Infrared Microlasers from Self-Assembled Spiropyrane-Based Microsphercial Caps

Near-infrared (NIR) microlasers play a significant role in telecommunication and biomedical tissue imaging. However, it remains a big challenge to realize NIR microlasers because of the difficulty in preparing highly efficient NIR luminescent materials and perfect optical resonators. Here, we propose a molecular design strategy to creatively realize the first spiropyrane (SP)-based NIR microlasers with low threshold from self-assembled microsphercial caps. The tetraphenylethylene (TPE) moiety with a highly twisted conformation provides a large free volume to facilitate the photoisomerization process of SP and enhance NIR emission of merocyanine in the solid state. Moreover, self-assembled TPE-SP microsphercial caps simultaneously serve as gain media and resonant microcavities, providing optical gain and feedback for NIR laser oscillations with a low threshold (3.68 μJ/cm²). These results are beneficial for deeply understanding the SP microstructures-lasing emission characteristic relationship and provide a useful guideline for the rational molecular design of NIR microlasers with special functionalities.

Biomacromolecule-Functionalized AIEgens for Advanced Biomedical Studies

The advances in bioinformatics and biomedicine have promoted the development of biomedical imaging and theranostic systems to respectively extend the endogenous biomarker imaging with high contrast and enhance the therapeutic effect with high efficiency. The emergence of biomacromolecule-functionalized aggregation-induced emitters (AIEgens), utilizing AIEgens, and biomacromolecules (nucleic acids, peptides, glycans, and lipids), displays specific targeting ability to cancer cell, improved biocompatibility, reduced toxicity, enhanced therapeutic effect, and so forth. This review summarizes the rational design of biomacromolecule-functionalized AIEgens and their biomedical applications in recent ten years, including high-resolution optical imaging of cell, tissue, and small animal model with low background; the biomarker detection for early diagnosis and prognosis; the delivery and monitoring of prodrugs; image-guide photodynamic therapy and its combination with chemotherapy. Through illustrating their functional mechanisms and application, it is hoped that this review would open up a completely new train of research thought for attracted researchers in various fields.

A new approach to developing diagnostics and therapeutics: Aggregation-induced emission-based fluorescence turn-on

Fluorescence imaging is a promising visualization tool and possesses the advantages of in situ response and facile operation; thus, it is widely exploited for bioassays. However, traditional fluorophores suffer from concentration limits because they are always quenched when they aggregate, which impedes applications, especially for trace analysis and real-time monitoring. Recently, novel molecules with aggregation-induced emission (AIE) characteristics were developed to solve the problems encountered when using traditional organic dyes, because these new molecules exhibit weak or even no fluorescence when they are in free movement states but emit intensely upon the restriction of intramolecular motions. Inspired by the excellent performances of AIE molecules, a substantial number of AIE-based probes have been designed, synthesized, and applied to various fields to fulfill diverse detection tasks. According to numerous experiments, AIE probes are more practical than traditional fluorescent probes, especially when used in bioassays. To bridge bioimaging and materials engineering, this review provides a comprehensive understanding of the development of AIE bioprobes. It begins with a summary of mechanisms of the AIE phenomenon. Then, the strategies to realize accurate detection using AIE probes are discussed. In addition, typical examples of AIE-active materials applied in diagnosis, treatment, and nanocarrier tracking are presented. In addition, some challenges are put forward to inspire more ideas in the promising field of AIE-active materials.

AIEgen based poly(L-lactic-co-glycolic acid) magnetic nanoparticles to localize cytokine VEGF for early cancer diagnosis and photothermal therapy

Aim: We demonstrated a novel theranostic system for simultaneous photothermal therapy and magnetic resonance imaging applicable to early diagnostics and treatment of cancer cells. Materials & methods: Oleic acid-Fe3O4 and triphenylamine-divinylanthracene-dicyano were loaded to the poly(L-lactic-co-glycolic acid) nanoparticles (NPs) on which anti-VEGF antibodies were modified to form anti-VEGF/OA-Fe3O4/triphenylamine-divinylanthracene-dicyano@poly(L-lactic-co-glycolic acid) NPs. The 1H nuclear magnetic resonance (NMR), mass spectra, fluorescence, UV absorption, dynamic light scattering, transmission electron microscope and inductively coupled plasma mass spectrometry tests were used to characterize the NPs, and the bioimaging was illustrated by confocal laser scanning microscope (CLSM) and in vivo MRI animal experiment. Results: This system was capable to recognize the overexpressed VEGF-A as low as 68 pg/ml in different cell lines with good selectivity and photothermal therapy effect. Conclusion: These ultrasensitive theranostic NPs were able to identify tumor cells by fluorescence imaging and MRI, and destroy tumors under near infrared illumination.

Quantum 3D thermal imaging at the micro-nanoscale

Real-time and accurate measurement of three-dimensional (3D) temperature field gradient maps of cells and tissues would provide an effective experimental method for analyzing the coupled correlation between metabolism and heat, as well as exploring the thermodynamic properties of nanoparticles under complex environments. In this work, a new principle of quantum 3D thermal imaging is proposed. The photoluminescence principle of quantum dots is expounded and CdTe QDs are prepared by aqueous phase synthesis. Fluorescence spectral characteristics of QDs at different temperatures are studied. The optimized algorithm of the optical spot double helix point spread function is proposed to improve the imaging, where optimized light energy increased by 27.36%. The design scheme of a quantum 3D thermal imaging system is presented. The measurement range is (-8 mm, +8 mm). The temperature is calculated according to the temperature-heat curve of quantum dots. The double helix point spread function has converted the defocus distance of QDs into the rotation angle of the double optical spot, thereby determining its position. The experimental results reveal that real-time 3D tracking and temperature measurements of quantum dots at the micro-nanoscale are achieved. Overall, the proposed nano-scale 3D quantum thermal imaging system with high-resolution may provide a new research direction and exploration of many frontier fields.

AIEgens/Nucleic Acid Nanostructures for Bioanalytical Applications

DNA occupies significant roles in life processes, which include encoding the sequences of proteins and accurately transferring genetic information from generation to generation. Recent discoveries have demonstrated that a variety of biological functions are correlated with DNA's conformational transitions. The non-B form has attained great attention among the diverse forms of DNA over the past several years. The main reason for this is that a large number of studies have shown that the non-B form of DNA is associated with gross deletions, inversions, duplications, translocations as well as simple repeating sequences, which therefore causes human diseases. Consequently, the conformational transition of DNA between the B-form and the non-B form is important for biology. Conventional fluorescence probes based on the conformational transitions of DNA usually need a fluorophore and a quencher group, which suffers from the complex design of the structure and tedious synthetic procedures. Moreover, conventional fluorescence probes are subject to the aggregation-caused quenching (ACQ) effect, which limits their application toward imaging and analyte detection. Fluorogens exhibiting aggregation-induced emission (AIE) have attracted tremendous attention over the past decade. By taking advantage of this unique behavior, plenty of fluorescent switch-on probes without the incorporation of fluorescent quenchers/fluorophore pairs have been widely developed as biosensors for imaging a variety of analytes. Herein, the recent progress in bioanalytical applications on the basis of aggregation-induced emission luminogens (AIEgens)/nucleic acid nanostructures are presented and discussed.

Aptamer-Based Biosensing with a Cationic AIEgen

Fabrication of low-cost biosensing platforms with high selectivity and sensitivity is important for constructing portable devices for personal health monitoring. Herein, we report a simple biosensing strategy based on the combination of a cationic AIEgen (aggregation-induced emission fluorogen), TPE-2+, with an aptamer for specific protein detection. The target protein can displace the dye molecules on the dye–aptamer complex, resulting in changes in the fluorescence signal. Selectivity towards different targets can be achieved by simply changing the aptamer sequence. The working mechanism is also investigated.

A water-soluble AIE-gen for organic-solvent-free detection and wash-free imaging of Al3+ ions and subsequent sensing of F− ions and DNA tracking

A water-soluble TPE-based AIEgen (TPE-diBuS) was developed for organic-solvent-free detection of Al³⁺ ions and its wash-free cell imaging. The TPE-diBuS-Al ensemble was used for the detection of F⁻ ions and DNA tracking.

2-Styrylquinoline-based two-photon AIEgens for dual monitoring of pH and viscosity in living cells

A new class of aggregation-induced emission (AIE) fluorophores HAPHs with excellent two-photon properties is developed from styrylquinoline.

Graphene Oxide Based Recyclable in Vivo Device for Amperometric Monitoring of Interferon-γ in Inflammatory Mice

Cytokine sensing is challenging due to their typically low abundances in physiological conditions. Nanomaterial fabricated interfaces demonstrated unique advantages in ultrasensitive sensing. Here, we demonstrate an amperometric sensing device based on graphene oxide (GO) and structure-switching aptamers for long-term detection of cytokines in a living organism. The device incorporates a single layer of GO acting as a signal amplifier on glassy carbon electrodes. The hairpin aptamers specific to interferon-γ (IFN-γ), which were loaded with redox probes, are covalently attached to GO to serve as biorecognition moieties. IFN-γ was able to trigger the configuration change of aptamers while releasing the trapped redox probes to introduce the electrochemical signal. This in vivo device was capable of quantitatively and dynamically detecting IFN-γ down to 1.3 pg mL^-1 secreted by immune cells in cell culture medium with no baseline drift even at a high concentration of other nonspecific proteins. The biocompatible devices were also implanted into subcutaneous tissue of enteritis mice, where they performed precise detection of IFN-γ over 48 h without using physical barriers or active drift correction algorithms. Moreover, the device could be reused even after multiple rounds of regeneration of the sensing interface.

High-Throughput Signal-On Photoelectrochemical Immunoassay of Lysozyme Based on Hole-Trapping Triggered by Disintegrating Bioconjugates of Dopamine-Grafted Silica Nanospheres

A unique split-type photoelectrochemical (PEC) immunoassay has been constructed for detection of low-abundance biocompounds (lysozyme, Lyz, used in this case) via a new trigger strategy by disintegrating bioconjugates of dopamine-grafted silica nanospheres (DA@SiO₂NSs) for signal amplification. The preferred electron donor assembly of DA@SiO₂NSs is first used as a molecular printboard for positioning anti-Lyz secondary antibody (Ab₂) through an amide reaction. With specific immunoreactions in a high-binding microplate, a sandwich immunoassay, the DA@SiO₂NSs-based bioconjugate is achieved. By initiating the disintegration of the bioconjugates via acid etching, numerous electron donors of DA are released, thus efficiently triggering hole-trapping with amplified signals obtained. The smart integration of ZnIn₂S₄-based heterojunctions as photoactive material, a split-type detection mode, and a new trigger strategy by disintegrating the DA@SiO₂NSs-based bioconjugate offer an attractive high-throughput signal-on PEC immunoassay for detection of Lyz. Such an unusual PEC sensor exhibits an outstanding linear response to the concentration in the range between 0.002 and 500 ng mL^-1, and the detection limit is as low as 0.6 ppt ( S/ N = 3). The as-fabricated assay is cost-effective and sensitive. It has been successfully used for measuring Lyz in real samples, which demonstrates great promise for practical applications.