Surfactant-Stripped Micelles with Aggregation-Induced Enhanced Emission for Bimodal Gut Imaging In Vivo and Microbiota Tagging Ex Vivo

Impact of the Acceptor Group on the Properties of Triphenylamine-Donor-Acceptor Dyes: An Experimental and Computational Study

Three triphenylamine-Indane donor-acceptor dyes with different functional groups on the acceptor were studied to investigate how substitution would affect the optical properties. The dyes studied were IndCN, containing two malononitrile groups; InO, with two ketone groups; and InOCN, which features mixed functional groups. A combination of Raman spectroscopy, UV-vis absorption and emission spectroscopy, and density functional theory (DFT) calculations were employed for characterization. The dyes exhibited intramolecular charge transfer transitions with relatively high molar absorptivity (εabs) of ∼50 mM-1 cm-1 at 491-591 nm within the visible spectrum and emissions at 690-840 nm in dichloromethane. The malononitrile-containing dyes showed lower-energy absorption and emissions due to a reduced band gap compared to ketone-containing dyes. The bulkiness of the malononitrile group led to a bent geometry, increasing nonradiative decay and reducing the fluorescence quantum yield. The dyes exhibited fluorescence quantum yields less than 0.25 and lifetimes of ∼5 ns. Resonance Raman spectra and DFT calculations showed that the longer linker group (propen-1-ylidene linker) in these systems reduced the charge-transfer character of the optical transition. The emission intensities of the three dyes were temperature-sensitive, with ketone-containing dyes showing shifts in emission bands as well. This could be due to molecular stacking and intermolecular π-interactions.

Expanding Our Horizons: AIE Materials in Bacterial Research

Bacteria share a longstanding and complex relationship with humans, playing a role in protecting gut health and sustaining the ecosystem to cause infectious diseases and antibiotic resistance. Luminogenic materials that share aggregation-induced emission (AIE) characteristics have emerged as a versatile toolbox for bacterial studies through fluorescence visualization. Numerous research efforts highlight the superiority of AIE materials in this field. Recent advances in AIE materials in bacterial studies are categorized into four areas: understanding bacterial interactions, antibacterial strategies, diverse applications, and synergistic applications with bacteria. Initial research focuses on visualizing the unseen bacteria and progresses into developing strategies involving electrostatic interactions, amphiphilic AIE luminogens (AIEgens), and various AIE materials to enhance bacterial affinity. Recent progress in antibacterial strategies includes using photodynamic and photothermal therapies, bacterial toxicity studies, and combined therapies. Diverse applications from environmental disinfection to disease treatment, utilizing AIE materials in antibacterial coatings, bacterial sensors, wound healing materials, etc., are also provided. Finally, synergistic applications combining AIE materials with bacteria to achieve enhanced outcomes are explored. This review summarizes the developmental trend of AIE materials in bacterial studies and is expected to provide future research directions in advancing bacterial methodologies.

Oxygen Self-Supplied Perfluorocarbon-Modified Micelles for Enhanced Cancer Photodynamic Therapy and Ferroptosis

Photodynamic therapy (PDT) and ferroptosis show significant potential in tumor treatment. However, their therapeutic efficacy is often hindered by the oxygen-deficient tumor microenvironment and the challenges associated with efficient intracellular drug delivery into tumor cells. Toward this end, this work synthesized perfluorocarbon (PFC)-modified Pluronic F127 (PFC-F127), and then exploits it as a carrier for codelivery of photosensitizer Chlorin e6 (Ce6) and the ferroptosis promoter sorafenib (Sor), yielding an oxygen self-supplying nanoplatform denoted as Ce6-Sor@PFC-F127. The PFCs on the surface of the micelle play a crucial role in efficiently solubilizing and delivering oxygen as well as increasing the hydrophobicity of the micelle surface, giving rise to enhanced endocytosis by cancer cells. The incorporation of an oxygen-carrying moiety into the micelles enhances the therapeutic impact of PDT and ferroptosis, leading to amplified endocytosis and cytotoxicity of tumor cells. Hypotonic saline technology was developed to enhance the cargo encapsulation efficiency. Notably, in a murine tumor model, Ce6-Sor@PFC-F127 effectively inhibited tumor growth through the combined use of oxygen-enhanced PDT and ferroptosis. Taken together, this work underscores the promising potential of Ce6-Sor@PFC-F127 as a multifunctional therapeutic nanoplatform for the codelivery of multiple cargos such as oxygen, photosensitizers, and ferroptosis inducers.

Omics for deciphering oral microecology

The human oral microbiome harbors one of the most diverse microbial communities in the human body, playing critical roles in oral and systemic health. Recent technological innovations are propelling the characterization and manipulation of oral microbiota. High-throughput sequencing enables comprehensive taxonomic and functional profiling of oral microbiomes. New long-read platforms improve genome assembly from complex samples. Single-cell genomics provides insights into uncultured taxa. Advanced imaging modalities including fluorescence, mass spectrometry, and Raman spectroscopy have enabled the visualization of the spatial organization and interactions of oral microbes with increasing resolution. Fluorescence techniques link phylogenetic identity with localization. Mass spectrometry imaging reveals metabolic niches and activities while Raman spectroscopy generates rapid biomolecular fingerprints for classification. Culturomics facilitates the isolation and cultivation of novel fastidious oral taxa using high-throughput approaches. Ongoing integration of these technologies holds the promise of transforming our understanding of oral microbiome assembly, gene expression, metabolites, microenvironments, virulence mechanisms, and microbe-host interfaces in the context of health and disease. However, significant knowledge gaps persist regarding community origins, developmental trajectories, homeostasis versus dysbiosis triggers, functional biomarkers, and strategies to deliberately reshape the oral microbiome for therapeutic benefit. The convergence of sequencing, imaging, cultureomics, synthetic systems, and biomimetic models will provide unprecedented insights into the oral microbiome and offer opportunities to predict, prevent, diagnose, and treat associated oral diseases.

Barium sulfate and pigment admixture for photoacoustic and x-ray contrast imaging of the gut

Significance

X-ray imaging is frequently used for gastrointestinal imaging. Photoacoustic imaging (PAI) of the gastrointestinal tract is an emerging approach that has been demonstrated for preclinical imaging of small animals. A contrast agent active in both modalities could be useful for imaging applications.

Aim

We aimed to develop a dual-modality contrast agent comprising an admixture of barium sulfate with pigments that absorb light in the second near-infrared region (NIR-II), for preclinical imaging with both x-ray and PAI modalities.

Approach

Eleven different NIR-II dyes were evaluated after admixture with a 40% w/v barium sulfate mixture. The resulting NIR-II absorption in the soluble fraction and in the total mixture was characterized. Proof-of-principle imaging studies in mice were carried out.

Results

Pigments that produced more uniform suspensions were assessed further for photoacoustic contrast signal at a wavelength of 1064 nm that corresponds to the output of the Nd:YAG laser used. Phantom imaging studies demonstrated that the pigment-barium sulfate mixture generated imaging contrast in both x-ray and PAI modalities. The optimal pigment selected for further study was a cyanine tetrafluoroborate salt. Ex-vivo and whole-body mouse imaging demonstrated that photoacoustic and x-ray contrast signals co-localized in the intestines for both imaging modalities.

Conclusion

These data demonstrate that commercially-available NIR-II pigments can simply be admixed with barium sulfate to generate a dual-modality contrast agent appropriate for small animal gastrointestinal imaging.

Application of Nanoparticles in the Diagnosis of Gastrointestinal Diseases: A Complete Future Perspective

The diagnosis of gastrointestinal (GI) diseases currently relies primarily on invasive procedures like digestive endoscopy. However, these procedures can cause discomfort, respiratory issues, and bacterial infections in patients, both during and after the examination. In recent years, nanomedicine has emerged as a promising field, providing significant advancements in diagnostic techniques. Nanoprobes, in particular, offer distinct advantages, such as high specificity and sensitivity in detecting GI diseases. Integration of nanoprobes with advanced imaging techniques, such as nuclear magnetic resonance, optical fluorescence imaging, tomography, and optical correlation tomography, has significantly enhanced the detection capabilities for GI tumors and inflammatory bowel disease (IBD). This synergy enables early diagnosis and precise staging of GI disorders. Among the nanoparticles investigated for clinical applications, superparamagnetic iron oxide, quantum dots, single carbon nanotubes, and nanocages have emerged as extensively studied and utilized agents. This review aimed to provide insights into the potential applications of nanoparticles in modern imaging techniques, with a specific focus on their role in facilitating early and specific diagnosis of a range of GI disorders, including IBD and colorectal cancer (CRC). Additionally, we discussed the challenges associated with the implementation of nanotechnology-based GI diagnostics and explored future prospects for translation in this promising field.

Imaging of Gastrointestinal Tract Ailments

Gastrointestinal (GI) disorders comprise a diverse range of conditions that can significantly reduce the quality of life and can even be life-threatening in serious cases. The development of accurate and rapid detection approaches is of essential importance for early diagnosis and timely management of GI diseases. This review mainly focuses on the imaging of several representative gastrointestinal ailments, such as inflammatory bowel disease, tumors, appendicitis, Meckel's diverticulum, and others. Various imaging modalities commonly used for the gastrointestinal tract, including magnetic resonance imaging (MRI), positron emission tomography (PET) and single photon emission computed tomography (SPECT), and photoacoustic tomography (PAT) and multimodal imaging with mode overlap are summarized. These achievements in single and multimodal imaging provide useful guidance for improved diagnosis, staging, and treatment of the corresponding gastrointestinal diseases. The review evaluates the strengths and weaknesses of different imaging techniques and summarizes the development of imaging techniques used for diagnosing gastrointestinal ailments.

Design and application of organic contrast agents for molecular imaging in the second near infrared (NIR-II) window

Optical imaging in the second near-infrared (NIR-II) window has attracted interest in recent years because of the merits of reduced light scattering, minimal autofluorescence from biological tissues and deeper penetration depth in this wavelength range. In this review, we summarize NIR-II organic contrast agents reported in the past decade for photoacoustic and fluorescence imaging including members of the cyanine family, D-A-D structure dyes, phthalocyanines and semiconducting polymers. Improved imaging contrast and higher resolution could be favorably achieved by rational design of NIR-II fluorophores by tuning their properties including molar extinction coefficient, fluorescence quantum yield, emission wavelength and others. A wide variety of applications using NIR-II dyes has been realized including imaging of tumors, lymphatics, brains, intestines and others. Emerging applications such as targeted imaging and activable imaging with improved resolution and sensitivity have been demonstrated by innovative chemical modification of NIR-II dyes. Looking forward, rational design of improved NIR-II dyes for advanced bioimaging is likely to remain an area of interest for next-generation potential approaches to disease diagnosis.

Recent advances in aggregation-induced emission luminogens in photoacoustic imaging

Photoacoustic imaging (PAI) is a rapidly emerging modality in biomedical research with the advantages of noncontact operation, high optical resolution, and deep penetration. Great efforts and progress in the development of PAI agents with improved imaging resolution and sensitivity have been made over the past 2 decades. Among them, organic agents are the most promising candidates for preclinical/clinical applications due to their outstanding in vivo properties and facile biofunctionalities. Motivated by the unique properties of aggregation-induced emission (AIE) luminogens (AIEgens), various optical probes have been developed for bioanalyte detection, multimodal bioimaging, photodynamic/photothermal therapy, and imaging-guided therapeutics. In particular, AIE-active contrast agents have been demonstrated in PAI applications with excellent performance in imaging resolution and tissue permeability in vivo. This paper presents a brief overview of recent progress in AIE-based agents in the field of photoacoustic imaging. In particular, we focus on the basic concepts, data sorting and comparison, developing trends, and perspectives of photoacoustic imaging. Through numerous typical examples, the way each system realizes the desired photoacoustic performance in various biomedical applications is clearly illustrated. We believe that AIE-based PAI agents would be promising multifunctional theranostic platforms in clinical fields and will facilitate significant advancements in this research topic.

Effective Genome Editing Using CRISPR-Cas9 Nanoflowers

CRISPR-Cas9 as a powerful gene-editing tool has tremendous potential for the treatment of genetic diseases. Herein, a new mesoporous nanoflower (NF)-like delivery nanoplatform termed Cas9-NF is reported by crosslinking Cas9 and polymeric micelles that enables efficient intracellular delivery and controlled release of Cas9 in response to reductive microenvironment in tumor cells. The flower morphology is flexibly tunable by the protein concentration and different types of crosslinkers. Cas9 protein, embedded between polymeric micelles and protected by Cas9-NF, remains stable even under extreme pH conditions. Responsive cleavage of crosslinkers in tumor cells, leads to the traceless release of Cas9 for efficient gene knockout in nucleus. This crosslinked nanoparticle exhibits excellent capability of downregulating oncogene expression and inhibiting tumor growth in a murine tumor model. Taken together, these findings pave a new pathway toward the application of the protein-micelle crosslinked nanoflower for protein delivery, which warrants further investigations for gene regulation and cancer treatment.

Surfactant-Stripped Semiconducting Polymer Micelles for Tumor Theranostics and Deep Tissue Imaging in the NIR-II Window

Photoacoustic imaging (PA) in the second near infrared (NIR-II) window presents key advantages for deep tissue imaging owing to reduced light scattering and low background signal from biological structures. Here, a thiadiazoloquinoxaline-based semiconducting polymer (SP) with strong absorption in the NIR-II region is reported. After encapsulation of SP in Pluronic F127 (F127) followed by removal of excess surfactant, a dual functional polymer system named surfactant-stripped semiconductor polymeric micelles (SSS-micelles) are generated with water solubility, storage stability, and high photothermal conversion efficiency, permitting tumor theranostics in a mouse model. SSS-micelles have a wideband absorption in the NIR-II window, allowing for the PA imaging at both 1064 and 1300 nm wavelengths. The PA signal of the SSS-micelles can be detected through 6.5 cm of chicken breast tissue in vitro. In mice or rats, SSS-micelles can be visualized in bladder and intestine overlaid 5 cm (signal to noise ratio, SNR ≈ 17 dB) and 5.8 cm (SNR over 10 dB) chicken breast tissue, respectively. This work demonstrates the SSS-micelles as a nanoplatform for deep tissue theranostics.

Anticancer Vaccination with Immunogenic Micelles That Capture and Release Pristine CD8+ T-Cell Epitopes and Adjuvants

The development of nanocarriers capable of codelivering antigens and immune-activating adjuvants is an emerging area of research and is relevant for cancer vaccines that target induction of antigen-specific CD8⁺ T-cell responses. Here, we report a system for delivery of short peptide antigens to dendritic cells for strong cellular immune responses, based on block copolymers chemically modified with a hydrophobic and self-immolative linker. After modification, micelles effectively and reversibly capture antigens and adjuvants via a covalent bond within several minutes in an aqueous solution. After uptake in antigen presenting cells, the polymer disulfide bond is cleaved by intracellular glutathione, leading to release of pristine antigens, along with the upregulated expression of costimulatory molecules. The induced antigen-specific CD8⁺ T cells have strong tumor cell killing efficacy in the murine B16OVA and human papilloma virus-E6/E7 subcutaneous and lung metastasis tumor models. In addition, delivery to lymph nodes can be imaged to visualize vaccine trafficking. Taken together, multifunctional self-immolative micelles represent a versatile class of a vaccine delivery system for the generation of a cellular immune response that warrants further exploration as a component of cancer immunotherapy.

Traceless antibiotic-crosslinked micelles for rapid clearance of intracellular bacteria

Effective delivery of antimicrobial agents to intracellular pathogens represents a major bottleneck for a wide variety of infectious diseases. To address this, we developed SIR-micelles(+), as a new delivery vehicle comprising antibiotic-loaded micelles with rapid self-immolation within cells for targeted delivery to macrophages, where most intracellular bacterial reside. After phagocytosis, SIR-micelles(+) rapidly release the pristine antibiotic after the cleavage of the disulfide bonds by intracellular reducing agents such as glutathione (GSH). Colistin, a hydrophilic and potent "last-resort" antibiotic used for the treatment of drug-resistant bacterial infection, was encapsulated in SIR-micelles with 40% yield and good short-term storage stability. Hydrophobic moieties and mannose ligands in SIR-micelles(+) enhanced the delivery of colistin into macrophages. The traceless and thiol-responsive release of colistin effectively eliminated intracellular Escherichia coli within twenty minutes. In a murine pneumonia model, SIR-micelles(+) significantly reduced bacterial lung burden of multidrug-resistant Klebsiella pneumoniae. Furthermore, SIR-micelles(+) improved the survival rate and reduced the bacterial burden of organs infected by intracellular bacteria transferred from donor mice. Using this formulation approach, the nephrotoxicity and neurotoxicity induced by antibiotic were reduced by about 5- 15 fold. Thus, SIR-micelles(+) represent a new class of material that can be used for targeting treatment of intracellular and drug-resistant pathogens.