AIE-based theranostic systems for detection and killing of pathogens

Multiscale and stimuli-responsive biosensing in biomedical applications: Emerging biomaterials based on aggregation-induced emission luminogens

Biosensors play a critical role in the diagnosis, treatment, and prognosis of diseases, with diverse applications ranging from molecular diagnostics to in vivo imaging. Conventional fluorescence-based biosensors, however, often suffer from aggregation-caused emission quenching (ACQ), limiting their effectiveness in high concentrations and complex environments. In contrast, the phenomenon of aggregation-induced emission (AIE) has emerged as a promising alternative, where luminescent materials exhibit strong emission in the aggregated state with good photostability, biocompatibility, large Stokes shift, high quantum yield, and tunable emission. This review article discusses the development of AIEgen-based biosensors for multiscale biosensing in biomedical applications. The integration of AIEgens with nanomaterials, such as graphene oxide and stimuli-responsive nanomaterials, can further improve the selectivity and multifunctionality of biomolecule detection. By careful molecular design, the affinity between AIEgens and specific biomolecules can be tuned, enabling the selective detection of targets like DNA, RNA, and proteins ex vivo, in vitro and in vivo, which can be applied across multiple scales, from detecting biomolecules and cellular structures to analyzing tissues and organs, underscoring their growing importance in disease diagnosis. Furthermore, we explore the potential integration of AIEgen-based biosensors with artificial intelligence (AI) technologies, offering promising avenues for future advancements in this field.

Eradication of Antibiotic-Resistant Gram-Positive Bacteria and Biofilms by Rationally Designed AIE-Active Iridium(III) Complexes Derived from Cyclometalating 2-Phenylquinoline and Ancillary Bipyridyl Ligands

Antibiotic resistance caused by Gram-positive bacteria is a growing global human health threat. Selective discrimination and eradication of Gram-positive bacteria and their biofilms is challenging. Therapeutic strategies with multiple modes of action are urgently needed to address the increase in Gram-positive bacteria-resistant nosocomial infections. In this work, we have presented rationally designed aggregation-induced emission (AIE)-active cationic cyclometalated iridium(III) complexes derived from 2-phenylquinoline and 2,2'-bipyridine ligands for Gram-positive antibacterial studies. The AIE properties of these complexes were exploited for selective discrimination between Gram-positive and Gram-negative bacteria. These complexes displayed good antimicrobial activity against critical Gram-positive ESKAPE pathogens with minimum inhibitory concentrations in the low micromolar range but were inactive against Gram-negative pathogens. Importantly, the complexes can inhibit biofilm formation and eradicate bacteria from mature biofilms, which are major causes of persistent infections and antibiotic resistance and are more difficult to eliminate. In addition, these complexes showed low hemolytic activity against mammalian cells and a high therapeutic index, indicating good selectivity. Interestingly, the complexes kill bacteria through a variety of modes of mechanism, including ROS generation, cell membrane disruption, and depolarization and the loss of bacterial membrane integrity. These findings offer opportunities for designing metal AIEgens to treat Gram-positive bacterial infections effectively.

Progress and challenges in bacterial infection theranostics based on functional metal nanoparticles

The rapid proliferation and infection of bacteria, especially multidrug-resistant bacteria, have become a great threat to global public health. Focusing on the emergence of "super drug-resistant bacteria" caused by the abuse of antibiotics and the insufficient and delayed early diagnosis of bacterial diseases, it is of great research significance to develop new technologies and methods for early targeted detection and treatment of bacterial infection. The exceptional effects of metal nanoparticles based on their unique physical and chemical properties make such systems ideal for the detection and treatment of bacterial infection both in vitro and in vivo. Metal nanoparticles also have admirable clinical application prospects due to their broad antibacterial spectrum, various antibacterial mechanisms and excellent biocompatibility. Herein, we summarized the research progress concerning the mechanism of metal nanoparticles in terms of antibacterial activity together with the detection of bacterial. Representative achievements are selected to illustrate the proof-of-concept in vitro and in vivo applications. Based on these observations, we also give a brief discussion on the current problems and perspective outlook of metal nanoparticles in the diagnosis and treatment of bacterial infection.

Photosensitive AIEgens sensitize bacteria to oxidative damage and modulate the inflammatory responses of macrophages to salvage the photodynamic therapy against MRSA

The urgent need for antimicrobial agents to combat infections caused by multidrug-resistant bacteria facilitates the exploration of alternative strategies such as photosensitizer (PS)-mediated photoinactivation. However, increasing studies have discovered uncorrelated bactericidal activities among PSs possessing similar photodynamic and pathogen-targeted properties. To optimize the photodynamic therapy (PDT) against infections, we investigated three type-I PSs of D-π-A AIEgens TI, TBI, and TTI. The capacities of reactive oxygen species (ROS) generation of TI, TBI, and TTI did not align with their bactericidal activities. Despite exhibiting the lowest photodynamic efficiency, TI exhibited the highest activities against methicillin-resistant Staphylococcus aureus (MRSA) by impairing the anti-oxidative responses of bacteria. By comparison, TTI, characterized by the strongest ROS production, inactivated intracellular MRSA by potentiating the inflammatory response of macrophages. Unlike TI and TTI, TBI, despite possessing moderate photodynamic activities and inducing ROS accumulation in both MRSA and macrophages, did not exhibit any antibacterial activity. Therefore, relying on the disturbed anti-oxidative metabolism of pathogens or potentiated host immune responses, transient ROS bursts can effectively control bacterial infections. Our study reevaluates the contribution of photodynamic activities of PSs to bacterial elimination and provides new insights into discovering novel antibacterial targets and agents.

Hepcidin contributes to largemouth bass (Micropterus salmoides) against bacterial infections

The increasing emergence and dissemination of bacterial pathogens in largemouth bass culture accelerate the desire for new treatment measures. Antimicrobial peptides as the host's antimicrobial source dominate the preferred molecules for discovering antibacterial agents. Here, the potential of Hepcidin-1 from largemouth bass (Micropterus salmoides) (MsHep-1) against bacterial infection is demonstrated. MsHep-1 not only improved the survival rate in infection experiments involving Nocardia seriolae (12 %) and Aeromonas hydrophila (18 %) but also coped with iron overload conditions in vivo. Moreover, the antibacterial activity of MsHep-1 in vitro was identified against both gram-negative and gram-positive bacteria. Mechanistic studies show MsHep-1 leads to bacterial death by changing the bacterial membrane potential and disrupting the bacterial membrane structure. These findings demonstrate that MsHep-1 may play an important role in the host response to bacterial infection. It provides promising strategies in the application of immunosuppression prevention and control in fish. AMPs may be a promising and available reservoir for treating the current bacterial diseases.

Recent advances of aggregation‐induced emission in body surface organs

The surface organs mainly comprise the superficial layers of various parts of the mammalian body, including the skin, eyes, and ears, which provide solid protection against various threats to the entire body. Damage to surface organs could lead to many serious diseases or even death. Currently, despite significant advancements in this field, there remain numerous enigmas that necessitate expeditious resolution, particularly pertaining to diagnostic and therapeutic objectives. The advancements in nanomedicine have provided a significant impetus for the development of novel approaches in the diagnosis, bioimaging, and therapy of superficial organs. The aggregation‐induced emission (AIE) phenomenon, initially observed by Prof. Ben Zhong Tang, stands out due to its contrasting behavior to the aggregation‐caused quenching effect. This discovery has significantly revolutionized the field of nanomedicine for surface organs owing to its remarkable advantages. In this review of literature, we aim to provide a comprehensive summary of recent advances of AIE lumenogen (AIEgen)‐based nanoplatforms in the fields of detection, diagnosis, imaging, and therapeutics of surface organ‐related diseases and discuss their prospects in the domain. It is hoped that this review will help attract researchers’ attention toward the utilization of this field for the exploration of a wider range of biomedical and clinical applications.

Expert opinion on antimicrobial therapies: is there enough scientific evidence to state that targeted therapies outperform non-targeted ones?

INTRODUCTION

Different active and passive strategies have been developed to fight against pathogenic bacteria. Those actions are undertaken to reduce the bacterial burden while minimizing the possibilities to develop not only antimicrobial resistance but also antimicrobial side-effects such as allergic or hypersensitivity reactions.

AREAS COVERED

We have reviewed preclinical results that evidence that targeted antimicrobial therapies outperform non-targeted ones. Active selective targeting against pathogenic bacteria has been achieved through the functionalization of antimicrobials, either alone or encapsulated within micro- or nanocarriers, with various recognition moieties. These moieties include peptides, aptamers, antibodies, carbohydrates, extracellular vesicles, cell membranes, infective agents, and other affinity ligands with specific bacterial tropism. Those selective ligands increase retention and enhance effectiveness reducing the side-effects and the required dose to exert the antimicrobial action at the site of infection.

EXPERT OPINION

When using targeted antimicrobial therapies not only reduced side-effects are observed, but also, compared to the administration of equivalent doses of the non-targeted drugs, a superior efficacy has been demonstrated against planktonic, sessile, and intracellular pathogenic bacterial persisters. The translation of those targeted therapies to subsequent phases of clinical development still requires the demonstration of a reduction in the probabilities for the pathogen to develop resistance when using targeted approaches.

Aggregation-Induced Emission-Armored Living Bacteriophage-DNA Nanobioconjugates for Targeting, Imaging, and Efficient Elimination of Intracellular Bacterial Infection

Intracellular bacterial infections bring a considerable risk to human life and health due to their capability to elude immune defenses and exhibit significant drug resistance. As a result, confronting and managing these infections present substantial challenges. In this study, we developed a multifunctional living phage nanoconjugate by integrating aggregation-induced emission luminogen (AIEgen) photosensitizers and nucleic acids onto a bacteriophage framework (forming MS2-DNA-AIEgen bioconjugates). These nanoconjugates can rapidly penetrate mammalian cells and specifically identify intracellular bacteria while concurrently producing a detectable fluorescent signal. By harnessing the photodynamic property of AIEgen photosensitizer and the bacteriophage's inherent targeting and lysis capability, the intracellular bacteria can be effectively eliminated and the activity of the infected cells can be restored. Moreover, our engineered phage nanoconjugates were able to expedite the healing process in bacterially infected wounds observed in diabetic mice models while simultaneously enhancing immune activity within infected cells and in vivo, without displaying noticeable toxicity. We envision that these multifunctional phage nanoconjugates, which utilize AIEgen photosensitizers and spherical nucleic acids, may present a groundbreaking strategy for combating intracellular bacteria and offer powerful avenues for theranostic applications in intracellular bacterial infection-associated diseases.

Polyarylether-based COFs coordinated by Tb3+ for the fluorescent detection of anthrax-biomarker dipicolinic acid

In this study, a rare-earth hybrid luminescent material (lanthanide@COF) was constructed for the detection of a biomarker for anthrax (dipicolinic acid, DPA). JCU-505-COOH was prepared by the hydrolysis of the cyano group in JCU-505 via a post-synthetic modification strategy, then the carboxyl groups in JCU-505-COOH coordinated with Tb3+ ions, similar to pincer vising nut. The prepared Tb3+@JCU-505-COOH exhibited a turn-on response toward DPA, which allowed the lanthanide@COF to serve as a fluorescence sensor with excellent selectivity and high sensitivity (binding constant Ka = 3.66 × 103). The fluorescent probe showed satisfactory performance for the determination of DPA in saliva and urine with a detection limit of 0.6 μM. Moreover, we established a facile point-of-care testing (POCT) using the Tb3+@JCU-505-COOH-based fluorescent test paper together with a smartphone for the initial diagnosis of anthrax. As expected, Tb3+@JCU-505-COOH showed great potential for the rapid screening of anthrax due to low cost, simple operation, and wide applicability.

Illuminating the path: aggregation-induced emission for food contaminants detection

Food safety is a global concern that deeply affects human health. To ensure the profitability of the food industry and consumer safety, there is an urgent need to develop rapid, sensitive, accurate, and cost-effective detection methods for food contaminants. Recently, the Aggregation-Induced Emission (AIE) has been successfully used to detect food contaminants. AIEgens, fluorescent dyes that cause AIE, have several valuable properties including high quantum yields, photostability, and large Stokes shifts. This review provides a detailed introduction to the principles and advantages of AIE-triggered detection, followed by a focus on the past five years' applications of AIE in detecting various food contaminants including pesticides, veterinary drugs, mycotoxins, food additives, ions, pathogens, and biogenic amines. Each detection principle and component is comprehensively covered and explained. Moreover, the similarities and differences among different types of food contaminants are summarized, aiming to inspire future researchers. Finally, this review concludes with a discussion of the prospects for incorporating AIEgens more effectively into the detection of food contaminants.

The Role of Structural Hydrophobicity on Cationic Amphiphilic Aggregation-Induced Emission Photosensitizer-Bacterial Interaction and Photodynamic Efficiency

The aggregation-induced emission photosensitizer (AIE PS) has stood out as an alternative and competent candidate in bacterial theranostics, particularly with the use of cationic AIE PS in bacterial discrimination and elimination. Most reported work emphasizes the role of electrostatic interaction between cationic AIE PS and negatively charged bacterial surfaces, enabling broad applications from bacterial discrimination to bacterial killing. However, the underlying targeting mechanism and the design rationale of the cationic AIE PS for effective bacterial labeling remain poorly investigated. In this Article, we designed and synthesized a series of cationic amphiphilic AIE PSs with different calculated log P values. Then, we systemically studied the relationship between the hydrophobicity variation of AIE PS and bacterial targeting outcomes, the dose of AIE PS needed to label various species of bacteria, and their photodynamic antibacterial efficiency. The findings in this work provide a better understanding of the unclear AIE PS-bacterial interaction mechanism and some insights into the structural design strategies of cationic amphiphilic AIE PS for better development in bacterial theranostics.

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.

Mitochondria-Targeted Fluorescent Nanoparticles with Large Stokes Shift for Long-Term BioImaging

Mitochondria (MITO) play a significant role in various physiological processes and are a key organelle associated with different human diseases including cancer, diabetes mellitus, atherosclerosis, Alzheimer's disease, etc. Thus, detecting the activity of MITO in real time is becoming more and more important. Herein, a novel class of amphiphilic aggregation-induced emission (AIE) active probe fluorescence (AC-QC nanoparticles) based on a quinoxalinone scaffold was developed for imaging MITO. AC-QC nanoparticles possess an excellent ability to monitor MITO in real-time. This probe demonstrated the following advantages: (1) lower cytotoxicity; (2) superior photostability; and (3) good performance in long-term imaging in vitro. Each result of these indicates that self-assembled AC-QC nanoparticles can be used as effective and promising MITO-targeted fluorescent probes.

Phenotyping of Methicillin-Resistant Staphylococcus aureus Using a Ratiometric Sensor Array

Chemical tools capable of classifying multidrug-resistant bacteria (superbugs) can facilitate early-stage disease diagnosis and help guide precision therapy. Here, we report a sensor array that permits the facile phenotyping of methicillin-resistant Staphylococcus aureus (MRSA), a clinically common superbug. The array consists of a panel of eight separate ratiometric fluorescent probes that provide characteristic vibration-induced emission (VIE) profiles. These probes bear a pair of quaternary ammonium salts in different substitution positions around a known VIEgen core. The differences in the substituents result in varying interactions with the negatively charged cell walls of bacteria. This, in turn, dictates the molecular conformation of the probes and affects their blue-to-red fluorescence intensity ratios (ratiometric changes). Within the sensor array, the differences in the ratiometric changes for the probes result in "fingerprints" for MRSA of different genotypes. This allows them to be identified using principal component analysis (PCA) without the need for cell lysis and nucleic acid isolation. The results obtained with the present sensor array agree well with those obtained using polymerase chain reaction (PCR) analysis.

Noncancerous disease-targeting AIEgens

Noncancerous diseases include a wide plethora of medical conditions beyond cancer and are a major cause of mortality around the world. Despite progresses in clinical research, many puzzles about these diseases remain unanswered, and new therapies are continuously being sought. The evolution of bio-nanomedicine has enabled huge advancements in biosensing, diagnosis, bioimaging, and therapeutics. The recent development of aggregation-induced emission luminogens (AIEgens) has provided an impetus to the field of molecular bionanomaterials. Following aggregation, AIEgens show strong emission, overcoming the problems associated with the aggregation-caused quenching (ACQ) effect. They also have other unique properties, including low background interferences, high signal-to-noise ratios, photostability, and excellent biocompatibility, along with activatable aggregation-enhanced theranostic effects, which help them achieve excellent therapeutic effects as an one-for-all multimodal theranostic platform. This review provides a comprehensive overview of the overall progresses in AIEgen-based nanoplatforms for the detection, diagnosis, bioimaging, and bioimaging-guided treatment of noncancerous diseases. In addition, it details future perspectives and the potential clinical applications of these AIEgens in noncancerous diseases are also proposed. This review hopes to motivate further interest in this topic and promote ideation for the further exploration of more advanced AIEgens in a broad range of biomedical and clinical applications in patients with noncancerous diseases.

Primary Amine Functionalized Carbon Dots for Dead and Alive Bacterial Imaging

Small molecular dyes are commonly used for bacterial imaging, but they still meet a bottleneck of biological toxicity and fluorescence photobleaching. Carbon dots have shown high potential for bio-imaging due to their low cost and negligible toxicity and anti-photobleaching. However, there is still large space to enhance the quantum yield of the carbon quantum dots and to clarify their mechanisms of bacterial imaging. Using carbon dots for dyeing alive bacteria is difficult because of the thick density and complicated structure of bacterial cell walls. In this work, both dead or alive bacterial cell imaging can be achieved using the primary amine functionalized carbon dots based on their small size, excellent quantum yield and primary amine functional groups. Four types of carbon quantum dots were prepared and estimated for the bacterial imaging. It was found that the spermine as one of precursors can obviously enhance the quantum yield of carbon dots, which showed a high quantum yield of 66.46% and high fluorescence bleaching-resistance (70% can be maintained upon 3-h-irradiation). Furthermore, a mild modifying method was employed to bound ethylenediamine on the surface of the spermine-carbon dots, which is favorable for staining not only the dead bacterial cells but also the alive ones. Investigations of physical structure and chemical groups indicated the existence of primary amine groups on the surface of spermine-carbon quantum dots (which own a much higher quantum yield) which can stain alive bacterial cells visibly. The imaging mechanism was studied in detail, which provides a preliminary reference for exploring efficient and environment-friendly carbon dots for bacterial imaging.

Highly Efficient Photodynamic Therapy with Mitochondria-Targeting Aggregation-Induced Emission Photosensitizer for Retinoblastoma

Retinoblastoma (RB) is an aggressive eye cancer in infancy and childhood, lethal by metastasis if left untreated. Currently, the survival rate and the chance of saving vision depend on the severity of the disease. In this work, a highly efficient photodynamic ophthalmic therapy for RB is reported by employing an isoquinolinium-based aggregation-induced-emission (AIE) photosensitizer (PS) TPE-IQ-2O for photodynamic inactivation (PDI). TPE-IQ-2O is an efficient mitochondria-targeting photosensitizer as an efficient guided photodynamic therapy (PDT) agent against cancer cells. Maximizing cancer-selectively damage to tumors with minimized side effects on normal tissue is essential for effective anticancer PDT and provides long-lasting protection against metastasis. In addition, TPE-IQ-2O can effectively reduce the degree of tissue inflammation by inhibiting the expression of related inflammatory factors. TPE-IQ-2O also exhibits excellent biocompatibility with a neglectable hemolysis effect on mouse red blood cells and almost no killing effect on mammalian cells, which enables its potential applications in the treatment of RB.

Advances in image-guided drug delivery for antibacterial therapy

The emergence of antibiotic-resistant bacterial strains is seriously endangering the global healthcare system. There is an urgent need for combining imaging with therapies to realize the real-time monitoring of pathological condition and treatment progress. It also provides guidance on exploring new medicines and enhance treatment strategies to overcome the antibiotic resistance of existing conventional antibiotics. In this review, we provide a thorough overview of the most advanced image-guided approaches for bacterial diagnosis (e.g., computed tomography imaging, magnetic resonance imaging, photoacoustic imaging, ultrasound imaging, fluorescence imaging, positron emission tomography, single photon emission computed tomography imaging, and multiple imaging), and therapies (e.g., photothermal therapy, photodynamic therapy, chemodynamic therapy, sonodynamic therapy, immunotherapy, and multiple therapies). This review focuses on how to design and fabricate photo-responsive materials for improved image-guided bacterial theranostics applications. We present a potential application of different image-guided modalities for both bacterial diagnosis and therapies with representative examples. Finally, we highlighted the current challenges and future perspectives image-guided approaches for future clinical translation of nano-theranostics in bacterial infections therapies. We envision that this review will provide for future development in image-guided systems for bacterial theranostics applications.

Cationic Liposomes with Different Lipid Ratios: Antibacterial Activity, Antibacterial Mechanism, and Cytotoxicity Evaluations

Due to their strong bacterial binding and bacterial toxicity, cationic liposomes have been utilized as effective antibacterial materials in many studies. However, few researchers have systematically compared their antibacterial activity with their mammalian cell cytotoxicity or have deeply explored their antibacterial and cytotoxicity mechanisms. Here, we prepared a series of cationic liposomes (termed CLs) using dimethyldioctadecylammonium chloride (DODAC) and lecithin at different molar ratios. CLs have the ability to effectively bind with Gram-positive and Gram-negative bacteria through electrostatic and hydrophobic interactions. Further, the CLs with high molar ratios of DODAC (30 and 40 mol%) can disrupt the bacterial wall/membrane, efficiently inducing the production of reactive oxygen species (ROS). More importantly, we carefully compared the antibacterial activity and the mammalian cell cytotoxicity of various CLs differing in DODAC contents and liposomal concentrations and revealed that, whether they are bacterial or mammalian cells, an increasing DODAC content in CLs can lead to an elevated cytotoxicity level. Further, there exists a critical DODAC contents (>20 mol%) in CLs to endow them with effective antibacterial ability. However, the variation in the DODAC content and liposomal concentration of CLs has different degrees of influence on the antibacterial activity or cytotoxicity. For example, CLs at high DODAC content (i.e., CL0.3 and CL0.4) could effectively kill both types of bacterial cells but only cause negligible toxicity to mammalian cells. We believe that a systematic comparison between the antibacterial activity and the cytotoxicity of CLs with different DODAC contents will provide an important reference for the potential clinical applications of cationic liposomes.

Antibacterial Theranostic Agents with Negligible Living Cell Invasiveness: AIE-Active Cationic Amphiphiles Regulated by Alkyl Chain Engineering

To address the threat of bacterial infection in the following post-antibiotic era, developing effective antibacterial approaches is of utmost urgency. Theranostic medicine integrating diagnosis and therapy is a promising protocol to fight against pathogenic bacteria. But numerous reported antibacterial theranostic materials are disclosed to be trapped in the excessive invasiveness to living mammal cells, leading to false positives and possible biosafety risks. Herein, a series of cationic pyridinium-substituted phosphindole oxide derivatives featuring aggregation-induced emission are designed, and alkyl chain engineering is conducted to finely tune their hydrophobicity and investigate their bioaffinity preference for living mammal cells and pathogenic bacteria. Most importantly, an efficient theranostic agent (PyBu-PIO) is acquired that is free from living cell invasiveness with negligible cytotoxicity and yet holds a good affinity for Gram-positive bacteria, including drug-resistant strains, with a superior inactivating effect. Externally applying PyBu-PIO onto Gram-positive bacteria-infected skin wounds can achieve creditable imaging effects and successfully accelerate the healing processes with reliable biosafety. This work proposes living cell invasiveness as a criterion for antibacterial theranostic materials and provides important enlightenment for the design of antibacterial theranostic materials.

Photoluminescent inorganic nanoprobe-based pathogen detection

Pathogens are serious threats to human health, and traditional detection techniques suffer from various limitations. The unique optical properties of photoluminescent inorganic nanomaterials, such as high photoluminescence quantum yields, good photostability, and tunable spectrum, make them ideal tools for the detection of pathogens with high specificity and sensitivity. In this review, the design strategies, working mechanisms, and applications of photoluminescent inorganic nanomaterial-based probes in pathogen detection are introduced. In particular, the design and construction of stimuli-responsive nanoprobes and their potential in these fields are highlighted.

Antibacterial and Fluorescence Staining Properties of an Innovative GTR Membrane Containing 45S5BGs and AIE Molecules In Vitro

This study aimed to add two functional components-antibacterial 45S5BGs particles and AIE nanoparticles (TPE-NIM⁺) with bioprobe characteristics-to the guided tissue regeneration (GTR) membrane, to optimize the performance. The PLGA/BG/TPE-NIM⁺ membrane was synthesized. The static water contact angle, morphologies, and surface element analysis of the membrane were then characterized. In vitro biocompatibility was tested with MC3T3-E1 cells using CCK-8 assay, and antibacterial property was evaluated with Streptococcus mutans and Porphyromonas gingivalis by the LIVE/DEAD bacterial staining and dilution plating procedure. The fluorescence staining of bacteria was observed by Laser Scanning Confocal Microscope. The results showed that the average water contact angle was 46°. In the cytotoxicity test, except for the positive control group, there was no significant difference among the groups (p > 0.05). The antibacterial effect in the PLGA/BG/TPE-NIM⁺ group was significantly (p < 0.01), while the sterilization rate was 99.99%, better than that in the PLGA/BG group (98.62%) (p < 0.01). Confocal images showed that the membrane efficiently distinguished G⁺ bacteria from G^- bacteria. This study demonstrated that the PLGA/BG/TPE-NIM⁺ membrane showed good biocompatibility, efficient sterilization performance, and surface mineralization ability and could be used to detect pathogens in a simple, fast, and wash-free protocol.

A concise detection strategy of Staphylococcus aureus using N-Succinyl-Chitosan-dopped bacteria-imprinted composite film and AIE fluorescence sensor

Staphylococcus aureus is one of the major foodborne pathogens. Efficient detection and isolation of Staphylococcus aureus from complex samples are crucial. Herein, we report a concise strategy to detect of Staphylococcus aureus with high sensitivity and specificity, based on N-Succinyl-Chitosan doping bacteria-imprinted composite film and aggregation-induced emission (AIE)-featuring fluorescence sensor. The good shaping and mechanical properties of polydimethylsiloxane provide a specific recognition site suitable for Staphylococcus aureus. For the first time, chitosan derivatives is combined with polydimethylsiloxane to prepare a two-component composite film, which possesses a remarkable absorption performance of Staphylococcus aureus using the natural excellent absorption property of chitosan. The positive charged AIE-featuring Au(I)-disulfide nanoparticles realized the quantitative characterization of Staphylococcus aureus without cooperation with bio-recognition elements. To conclude, this study provides new possibilities for the manufacture of highly efficient bacterial separators with superior performance and facilitates the application of unlabeled nanoparticles in quantitative analysis.

Pathways to fluorescence via restriction of intramolecular motion in substituted tetraphenylethylenes

The design of materials with enhanced luminescence properties is a fast-developing field due to the potential applicability of these materials as light-emitting diodes or for bioimaging. A transparent way to enhance the emission properties of interesting molecular candidates is blocking competing and unproductive non-radiative relaxation pathways by the restriction of intramolecular motions. Rationalized functionalization is an important possibility to achieve such restrictions. Using time-dependent density functional theory (TD-DFT) based on the ωB97XD functional and the semiempirical tight-binding method including long-range corrections (TD-LC-DFTB), this work investigates the effect of functionalization of the paradigmatic tetraphenylethylene (TPE) on achieving restricted access to conical intersections (RACI). Photodynamical surface hopping simulations have been performed on a larger set of compounds including TPE and ten functionalized TPE compounds. Functionalization has been achieved by means of electron-withdrawing groups, bulky groups which block the relaxation channels via steric hindrance and groups capable of forming strong hydrogen bonds, which restrict the motion via the formation of hydrogen bond channels. Most of the investigated functionalized TPE candidates show ultrafast deactivation to the ground state due to their still existing structural flexibility, but two examples, one containing -CN and -CF₃ groups and a second characterized by a network of hydrogen bonds, have been identified as interesting candidates for creating efficient luminescence properties in solution.

Recent Advances in Aggregation-Induced Emission Active Materials for Sensing of Biologically Important Molecules and Drug Delivery System

The emergence and development of aggregation induced emission (AIE) have attracted worldwide attention due to its unique photophysical phenomenon and for removing the obstacle of aggregation-caused quenching (ACQ) which is the most detrimental process thereby making AIE an important and promising aspect in various fields of fluorescent material, sensing, bioimaging, optoelectronics, drug delivery system, and theranostics. In this review, we have discussed insights and explored recent advances that are being made in AIE active materials and their application in sensing, biological cell imaging, and drug delivery systems, and, furthermore, we explored AIE active fluorescent material as a building block in supramolecular chemistry. Herein, we focus on various AIE active molecules such as tetraphenylethylene, AIE-active polymer, quantum dots, AIE active metal-organic framework and triphenylamine, not only in terms of their synthetic routes but also we outline their applications. Finally, we summarize our view of the construction and application of AIE-active molecules, which thus inspiring young researchers to explore new ideas, innovations, and develop the field of supramolecular chemistry in years to come.

Assessing Differential Binding of Aggregation-Induced Emission-Based Luminogens to Host Interacting Surface Proteins of SARS-CoV-2 and Influenza Virus-An in silico Approach

Early detection of asymptomatic cases through mass screening is essential to constrain the coronavirus disease 2019 (COVID-19) transmission. However, the existing diagnostic strategies are either resource-intensive, time-consuming, or less sensitive, which limits their use in the development of rapid mass screening strategies. There is a clear pressing need for simple, fast, sensitive, and economical diagnostic strategy for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) screening even in resource-limited settings. In the current work, we assessed the in silico feasibility of directly labeling virus surface proteins using fluorogenic molecules with aggregation-induced emission (AIE) property. Here, we present the results for binding of two such AIE probes, phosphonic acid derivative of tetraphenyl ethylene (TPE-P) and sulfonic acid derivative of tetraphenyl ethylene (TPE-S), to SARS-CoV-2 spike protein based on in silico docking studies. Our results show that both TPE-P and TPE-S bind to angiotensin converting enzyme 2 (ACE2)-binding, and N-terminal domains of SARS-CoV-2 spike protein. Molecular dynamic simulations have revealed specific nature of these interactions. We also show that TPE-P and TPE-S bind to hemagglutinin protein of influenza virus, but the interaction strength was found to be different. This difference in interaction strength may affect the emission spectrum of aforementioned AIE probes. Together, these results form a basis for the development of AIE-based diagnostics for differential detection of SARS-CoV-2 and influenza viruses. We believe that these in silico predictions certainly aid in differentially labeling of the both viruses toward the development of rapid detection by AIE probes.

A lipid droplet specific fluorescent probe for image-guided photodynamic therapy under hypoxia

Photodynamic therapy (PDT) is a potential strategy for many superficial, esophageal, intestinal, and bronchial cancer treatments, but its therapeutic effect is limited by a lack of specificity and the hypoxic tumor environment. It is necessary to develop novel photosensitizers (Ps) with organelles targeting and the ability to generate cytotoxic species under light irradiation without the presence of oxygen. Herein, we designed and synthesized a biocompatible fluorescent Ps CPNBD for lipid droplets (LDs) fluorescence (FL) image-guided PDT. CPNBD showed FL quenching in water but FL was significantly turned on by oil with a remarkable FL enhancement compared to that in aqueous solution. Due to its strong lipophilicity (Clog P of 7.96), CPNBD could specifically stain the LDs of human clear cell renal cell carcinoma (ccRCC) tumor cells and tissues with good photostability. Meanwhile, CPNBD could efficiently generate cytotoxic reactive oxygen species under low-power white-light irradiation, which could efficiently damage DNA via a PDT process with great tumor suppression ability in vitro and in vivo. Thus, this work provides a novel strategy for designing LD-targeting Ps with efficient image-guided PDT under the tumor hypoxic environment.

Aggregation-Induced Emission-Based Platforms for the Treatment of Bacteria, Fungi, and Viruses

The prevention and control of pathogenic bacteria, fungi, and viruses is a herculean task for all the countries since they greatly threaten global public health. Rapid detection and effective elimination of these pathogens is crucial for the treatment of related diseases. It is urgently demanded to develop new diagnostic and therapeutic strategies to combat bacteria, fungi, and viruses-induced infections. The emergence of aggregation-induced emission (AIE) luminogens (AIEgens) is a revolutionary breakthrough for the treatment of many diseases, including pathogenic infections. In this review, the main focus is on the applications of AIEgens for theranostic treatment of pathogenic bacteria, fungi, and viruses. Due to the AIE characteristic, AIEgens are promising fluorescent probes for the detection of bacteria, fungi, and viruses with excellent sensitivity and photostability. Moreover, AIEgen-based theranostic platforms can be fabricated by introducing bactericidal moieties or designing AIE photosensitizers and AIE photothermal agents. The current strategies and ongoing developments of AIEgens for the treatment of pathogenic bacteria, fungi, and viruses will be discussed in detail.

Aggregation-Induced Emission-Active Poly(phenyleneethynylene)s for Fluorescence and Raman Dual-Modal Imaging and Drug-Resistant Bacteria Killing

Poly(phenyleneethynylene) (PPE) is a widely used functional conjugated polymer with applications ranging from organic optoelectronics and fluorescence sensors to optical imaging and theranostics. However, the fluorescence efficiency of PPE in aggregate states is generally not as good as their solution states, which greatly compromises their performance in fluorescence-related applications. Herein, a series of PPE derivatives with typical aggregation-induced emission (AIE) properties is designed and synthesized. In these PPEs, the diethylamino-substituted tetraphenylethene units function as the long-wavelength AIE source and the alkyl side chains serve as the functionalization site. The obtained AIE-active PPEs with large π-conjugation show strong aggregate-state fluorescence, interesting self-assembly behaviors, inherently enhanced alkyne vibrations in the Raman-silent region of cells, and efficient antibacterial activities. The PPE nanoparticles with good cellular uptake capability can clearly and sensitively visualize the tumor region and residual tumors via their fluorescence and Raman signals, respectively, to benefit the precise tumor resection surgery. After post-functionalization, the obtained PPE-based polyelectrolyte can preferentially image bacteria over mammalian cells and possesses efficient photodynamic killing capability against Gram-positive and drug-resistant bacteria. This work provides a feasible design strategy for developing functional conjugated polymers with multimodal imaging capability as well as photodynamic antimicrobial ability.

Plasmon induced dual excited synergistic effect in Au/metal-organic frameworks composite for enhanced antibacterial therapy

Efficient antibacterial therapy holds great promise for human health. However, it is often limited by the insufficient activity of antibacterial agents. Herein, we demonstrate that the localized surface plasmon resonance (LSPR) excitation of gold nanostars (AuNSs) can dramatically improve the antibacterial activity of a Zn-metal-organic frameworks (Zn-MOFs) nanosheet, which exhibits higher ability to generate reactive oxygen species (ROS) (∼2.5-fold) for bacterial inactivation under light irradiation. Mechanistic investigations demonstrate that the enhancement is closely related to a plasmon-induced "dual excited synergistic effect". On the one hand, the Zn-MOFs nanosheets as photosensitive agents can be excited to generate ROS with bacterial toxicity. More importantly, abundant plasmonic hot electrons are generated on the surface of AuNSs upon LSPR excitation, which are then transferred from AuNSs into the Zn-MOFs due to the energy matching. As a result, the Zn-MOFs nanosheet presents an electron-rich condition, which activates the adsorbed O₂ molecule into a transition state followed by its decomposition into ROS for bacterial inactivation. This study highlights the superiority of LSPR excitation on improving the antibacterial activity of MOFs and provides a novel strategy for effective antibacterial therapy.

New Applications of Photodynamic Therapy in the Management of Candidiasis

The most important aetiological agent of opportunistic mycoses worldwide is Candida spp. These yeasts can cause severe infections in the host, which may be fatal. Isolates of Candida albicans occur with greater frequency and variable resistance patterns. Photodynamic therapy (PDT) has been recognised as an alternative treatment to kill pathogenic microorganisms. PDT utilises a photosensitizer, which is activated at a specific wavelength and oxygen concentration. Their reaction yields reactive oxygen species that kill the infectious microorganism. A systematic review of new applications of PDT in the management of candidiasis was performed. Of the 222 studies selected for in-depth screening, 84 were included in this study. All the studies reported the antifungal effectiveness, toxicity and dosimetry of treatment with antimicrobial PDT (aPDT) with different photosensitizers against Candida spp. The manuscripts that are discussed reveal the breadth of the new applications of aPDT against Candida spp., which are resistant to common antifungals. aPDT has superior performance compared to conventional antifungal therapies. With further studies, aPDT should prove valuable in daily clinical practice.

Aggregation induced emission molecules for detection of nucleic acids

Aggregation-induced emission (AIE) is an ingenious concept in the field of luminescent molecules. AIE is the energy released in an excited state that in turn is converted into light irrespective of being in either liquid phase or solid phase. Aggregation or crystallization of AIE molecules impedes the free movement of molecules and it resultantly becomes highly fluorescent. It is currently being used for several applications including sensing, diagnostic, protein, DNA or RNA detection, cells and cell organelles imaging. AIEs are highly sensitive and specific for binding with target molecules. In this chapter, we underline different AIE molecules for detection of nucleic acids.

Recent Strategies to Develop Innovative Photosensitizers for Enhanced Photodynamic Therapy

This review presents a robust strategy to design photosensitizers (PSs) for various species. Photodynamic therapy (PDT) is a photochemical-based treatment approach that involves the use of light combined with a light-activated chemical, referred to as a PS. Attractively, PDT is one of the alternatives to conventional cancer treatment due to its noninvasive nature, high cure rates, and low side effects. PSs play an important factor in photoinduced reactive oxygen species (ROS) generation. Although the concept of photosensitizer-based photodynamic therapy has been widely adopted for clinical trials and bioimaging, until now, to our surprise, there has been no relevant review article on rational designs of organic PSs for PDT. Furthermore, most of published review articles in PDT focused on nanomaterials and nanotechnology based on traditional PSs. Therefore, this review aimed at reporting recent strategies to develop innovative organic photosensitizers for enhanced photodynamic therapy, with each example described in detail instead of providing only a general overview, as is typically done in previous reviews of PDT, to provide intuitive, vivid, and specific insights to the readers.

Fast Broad-Spectrum Staining and Photodynamic Inhibition of Pathogenic Microorganisms by a Water-Soluble Aggregation-Induced Emission Photosensitizer

Pathogenic microorganisms pose great challenges to public health, which is constantly urgent to develop extra strategies for the fast staining and efficient treatments. In addition, once bacteria form stubborn biofilm, extracellular polymeric substance (EPS) within biofilm can act as protective barriers to prevent external damage and inward diffusion of traditional antibiotics, which makes it frequently develop drug-resistant ones and even hard to treat. Therefore, it is imperative to develop more efficient methods for the imaging/detection and efficient inhibition of pathogenic microorganisms. Here, a water-soluble aggregation-induced emission (AIE)-active photosensitizer TPA-PyOH was employed for fast imaging and photodynamic treatment of several typical pathogens, such as S. aureus, methicillin-resistant Staphylococcus aureus, L. monocytogenes, C. albicans, and E. coli. TPA-PyOH was non-fluorescent in water, upon incubation with pathogen, positively charged TPA-PyOH rapidly adhered to pathogenic membrane, thus the molecular motion of TPA-PyOH was restricted to exhibit AIE-active fluorescence for turn-on imaging with minimal background. Upon further white light irradiation, efficient reactive oxygen species (ROS) was in-situ generated to damage the membrane and inhibit the pathogen eventually. Furthermore, S. aureus biofilm could be suppressed in vitro. Thus, water-soluble TPA-PyOH was a potent AIE-active photosensitizer for fast fluorescent imaging with minimal background and photodynamic inhibition of pathogenic microorganisms.

Turn-on fluorescent probe for lipid droplet specific imaging of fatty liver and atherosclerosis

Fluorescence imaging plays an important role in researching the biological function of lipid droplets (LDs). However, the short-wave emission, tedious synthesis process and insufficient specificity have significantly limited the applications of commercially available probes. Herein, we have prepared a novel one-step synthesized near-infrared (NIR) fluorescent probe, TNBD, with a very low emission in aqueous solution and the solid state, but a significantly enhanced fluorescence emission is exhibited in oleic acid. Moreover, TNBD exhibited an impressive lipid droplet (LD) specific fluorescence turn-on ability in cells, fatty liver and atherosclerosis (AS) samples with a good biocompatibility and high signal-to-noise ratio. Our study not only establishes a novel LD turn-on fluorescence probe, but also provides a novel way to prepare a NIR LD targeted fluorescence probe.

Antibacterial AIE polycarbonates endowed with selective imaging capabilities by adjusting the electrostaticity of the mixed-charge backbone

Combining rapid microbial discrimination with antibacterial properties, multi-functional biomacromolecules allow the timely diagnosis and effective treatment of infectious diseases. Through a two-step approach involving organocatalytic ring-opening copolymerization and thiol-ene modification, aggregation-induced emission (AIE) polycarbonates decorated with tertiary amines were prepared. After being ionized using acetic acid, the obtained cationic AIE polycarbonate with excellent water solubility showed bacteria imaging capabilities and antibacterial activities toward both Gram-positive S. aureus and Gram-negative E. coli. It was indicated via scanning electron microscope images that the bactericidal mechanism involved membrane lysis, consistent with most cationic polymers. Through further co-grafting carboxyl and tertiary amine groups, mixed-charge AIE polycarbonates were obtained. The isoelectric points of such mixed-charge AIE polycarbonates could be simply tuned based on the grafting ratio of positive and negative moieties. Compared with the cationic AIE polycarbonate, mixed-charge AIE polycarbonates allowed the rapid and selective imaging of S. aureus, but not E. coli. The selectivity probably arose from the lower binding forces between the mixed-charge AIE polycarbonates and the low-negative-charge components of the E. coli surface. Therefore, these biodegradable polycarbonates, which integrated selective bacteria imaging and antibiotic abilities, potentially suggest a precision medicine approach for infectious diseases. The overall synthesis approach and mixed-charge AIE polycarbonates provide new references for the design and application of bio-related AIE polymers.

Real-Time Visualization and Monitoring of Physiological Dynamics by Aggregation-Induced Emission Luminogens (AIEgens)

Physiological dynamics in living cells and tissues are crucial for maintenance and regulation of their normal activities and functionalities. Tiny fluctuations in physiological microenvironments can leverage significant influences on cell growth, metabolism, differentiation, and apoptosis as well as disease evolution. Fluorescence imaging based on aggregation-induced emission luminogens (AIEgens) exhibits superior advantages in real-time sensing and monitoring of the physiological dynamics in living systems, including its unique properties such as high sensitivity and rapid response, flexible molecular design, and versatile nano- to mesostructural fabrication. The introduction of canonic AIEgens with long-wavelength, near-infrared, or microwave emission, persistent luminescence, and diversified excitation source (e.g., chemo- or bioluminescence) offers researchers a tool to evaluate the resulting molecules with excellent performance in response to subtle fluctuations in bioactivities with broader dimensionalities and deeper hierarchies.

A Membrane-Targeting Photosensitizer with Aggregation-Induced Emission Characteristics for Highly Efficient Photodynamic Combat of Human Coronaviruses

COVID-19 pandemic, caused by severe acute respiratory syndrome coronavirus 2, has resulted in global social and economic disruption, putting the world economy to the largest global recession since the Great Depression. To control the spread of COVID-19, cutting off the transmission route is a critical step. In this work, the efficient inactivation of human coronavirus with photodynamic therapy (PDT) by employing photosensitizers with aggregation-induced emission characteristics (DTTPB) is reported. DTTPB is designed to bear a hydrophilic head and two hydrophobic tails, mimicking the structure of phospholipids on biological membranes. DTTPB demonstrates a broad absorption band covering the whole visible light range and high molar absorptivity, as well as excellent reactive oxygen species sensitizing ability, making it an excellent candidate for PDT. Besides, DTTPB can target membrane structure, and bind to the envelope of human coronaviruses. Upon light irradiation, DTTPB demonstrates highly effective antiviral behavior: human coronavirus treated with DTTPB and white-light irradiation can be efficiently inactivated with complete loss of infectivity, as revealed by the significant decrease of virus RNA and proteins in host cells. Thus, DTTPB sensitized PDT can efficiently prevent the infection and the spread of human coronavirus, which provides a new avenue for photodynamic combating of COVID-19.

A biocompatible dual-AIEgen system without spectral overlap for quantitation of microbial viability and monitoring of biofilm formation

The lack of rapid and reliable microbial detection and sensing platforms and insufficient understanding of microbial behavior may delay precautions that could be made, which is a great threat to human life and increases the heavy financial burden on society. In this contribution, a dual-aggregation-induced emission luminogen (AIEgen) system is successfully developed for microbial imaging and metabolic status sensing. This system consists of two AIEgens (DCQA and TPE-2BA) that bear positively charged groups or boronic acid groups, providing universal microbial staining ability and specific affinity for dead microbes, respectively. Based on the distinctive fluorescence response produced by the diverse interaction of AIEgens with live or dead microbes, this dual-AIEgen system can detect all the microbes and identify their viabilities. Furthermore, the morphology and metabolic status of a sessile biofilm can also be imaged and monitored. The system exhibits rapid labelling properties that suitable for various microbes, and good biocompatibilities.

Nanobody modified high-performance AIE photosensitizer nanoparticles for precise photodynamic oral cancer therapy of patient-derived tumor xenograft

Photodynamic therapy (PDT) is a promising noninvasive treatment option for patients suffering from superficial tumors, such as oral cancer. However, for photosensitizers (PSs), it remains a grand challenge to simultaneously excel in all the key performance indicators including effective singlet oxygen (¹O₂) generation under clinical laser, specific targeting function and stable far-red (FR)/near-infrared (NIR) emission with low dark toxicity. In addition, traditional PS nanoparticles (NPs) for clinical use suffer from quenched fluorescence and reduced ¹O₂ production caused by molecular aggregation. To address these issues, AIEPS5 with aggregation-induced FR/NIR emission and effective ¹O₂ generation under 532 nm laser irradiation is designed by precise optimization of the chemical structure. By attaching a polyethylene glycol (PEG) chain onto AIEPS5, the yielded amphiphilic AIEPS5-PEG2000 can spontaneously self-assemble into water dispersible NPs, which are further endowed with targeted delivery function via the decoration of anti-Her-2 nanobody (NB). The bespoke AIEPS5-NPs-NB exhibit effective ¹O₂ generation capability, bright FR/NIR emission centered at 680 nm, and negligible dark toxicity, which outperform Heimbofen, a clinically approved PS in PDT using a patient-derived tumor xenograft model.

DNA-encoded bimetallic Au-Pt dumbbell nanozyme for high-performance detection and eradication of Escherichia coli O157:H7

Infectious Escherichia coli O157:H7 threatens the health of millions people each year. Thus, it is important to establish a simple and sensitive method for bacterial detection and eradication. Herein, a DNA-programming strategy is explored to synthesize anisotropic dumbbell-like Au-Pt nanoparticles with excellent catalytic and anti-bacterial activities, which were applied in the simultaneous detection and eradication of pathogenic bacteria. The DNA sequence-dependent growth of bimetallic nanoparticles is firstly studied and polyT20 has the tendency to form dumbbell-like Au-Pt bimetallic structures based on gold nanorods seeds. PolyA20 and polyC20 can also form similar structures but only at much lower DNA concentrations, which can be explained by their much higher affinity to the metal surfaces than T20. The as-prepared nanoparticles exhibit high nanozyme catalytic activity resulting from the synergistic effect of Au and Pt. Under light irradiation, the Au-Pt nanoparticles show high photothermal conversion efficiency and enhanced catalytic activity, which can be applied for the eradication and detection of E. coli O157:H7 with a robust efficacy (95%) in 5 min and provides excellent linear detection (10-10⁷ CFU/mL), with a detection limit of 2 CFU/mL. This study offered new insights into DNA-directed synthesis of nanomaterials with excellent biosensing and antibiotic applications.

Efficient Killing of Multidrug-Resistant Internalized Bacteria by AIEgens In Vivo

Bacteria infected cells acting as "Trojan horses" not only protect bacteria from antibiotic therapies and immune clearance, but also increase the dissemination of pathogens from the initial sites of infection. Antibiotics are hard and insufficient to treat such hidden internalized bacteria, especially multidrug-resistant (MDR) bacteria. Herein, aggregation-induced emission luminogens (AIEgens) such as N,N-diphenyl-4-(7-(pyridin-4-yl) benzo [c] [1,2,5] thiadiazol-4-yl) aniline functionalized with 1-bromoethane (TBP-1) and (3-bromopropyl) trimethylammonium bromide (TBP-2) (TBPs) show potent broad-spectrum bactericidal activity against both extracellular and internalized Gram-positive pathogens. TBPs trigger reactive oxygen species (ROS)-mediated membrane damage to kill bacteria, regardless of light irradiation. TBPs effectively kill bacteria without the development of resistance. Additionally, such AIEgens activate mitochondria dependent autophagy to eliminate internalized bacteria in host cells. Compared to the routinely used vancomycin in clinic, TBPs demonstrate comparable efficacy against methicillin-resistant Staphylococcus aureus (MRSA) in vivo. The studies suggest that AIEgens are promising new agents for the treatment of MDR bacteria associated infections.

Theranostic platforms for specific discrimination and selective killing of bacteria

Bacterial infections are serious threats to public health due to lack of advanced techniques to rapidly and accurately diagnose these infections in clinics. Although bacterial infections can be treated with broad-spectrum antibiotics based on empirical judgment, the emergence of antimicrobial resistance has attracted global attention due to long-term misuse and abuse of antibiotics by humans in recent decades. Therefore, it is imperative to selectively discriminate and precisely eliminate pathogenic bacteria. Herein, in addition to the conventional methods for bacterial identification, we comprehensively reviewed the recently developed theranostic platforms for specific discrimination and selective killing of bacteria according to their different interactions with the target bacteria, such as electrostatic and hydrophobic interactions, molecular recognition, microenvironment response, metabolic labeling, bacteriophage targeting, and others. These theranostic agents not only benefit from improved therapeutic efficiency but also present limited susceptibility to induce bacterial resistance. The strategies summarized in this review will open up new avenues in developing effective antimicrobial materials to accurately diagnose and treat bacterial infections in the post-antibiotic era. STATEMENT OF SIGNIFICANCE: Bacterial infections are difficult to be rapidly and accurately diagnosed, and are generally treated with broad-spectrum antibiotics, which leads to the development of drug resistance. By integrating imaging modalities and therapeutic methods in a single treatment, various theranostic agents have been developed to address the abovementioned issues. Therefore, the emerging theranostic platforms for selective identification and elimination of bacteria based on the distinct interactions of the theranostic agents with the target bacteria are summarized in this review. We believe that the information provided in this review will guide researchers in designing advanced antibacterial theranostics for practical applications in the post-antibiotic era.