Feng Gao

Activatable molecular probes in the second near-infrared (NIR-II, 900−1700 nm) window are sought-after for in vivo optical imaging and biosensing. However, current molecular skeletons are confined to a limited range of dye systems, including cyanine, hemicyanine, and xanthene derivatives. Herein, we report a series of ortho-halogenated phenol-conjugated aza boron dipyrromethene platforms (OBDP-xOH, where X = H, F, Cl, Br, or 2Cl) that achieve bright NIR-II emission through a pH-regulated intramolecular charge transfer mechanism. The optimized scaffold, OBDP-2ClOH (pKa = 6.1), concurrently demonstrates the NIR-II emission maximum at approximately 905 nm, a large Stokes shift of 117 nm, high NIR-II brightness (εmaxΦf>1000 nm ≈ 38.46 M−1 cm−1), and excellent photochemical stability. To validate the broad applicability of this platform, we further designed three target-activatable NIR-II nanoprobes responsive to UV light, H2S, and Cu2+, respectively. Each nanoprobe exhibited a high fluorescence turn-on ratio exceeding 29-fold and limits of detection below 10.3 nM. Leveraging these probes, we achieved rapid (<30 min) dynamic imaging of labile Cu2+ in the brains of Parkinson’s disease models, as well as high-fidelity in vivo early detection of acute liver injury within 5 min, which is substantially faster than conventional clinical serum analysis that requires approximately 90 min. Collectively, these findings underscore the translational potential of the OBDP-2ClOH scaffold as a versatile and generalizable platform for the development of advanced activatable NIR-II probes.

Abnormal accumulation of lipid droplets (LDs), accompanied by altered microenvironmental polarity within the microglia, is closely associated with neuroinflammation and also has been increasingly recognized as an early and dynamic indicator of Alzheimer’s disease (AD). Herein, a LD-targeting polarity-sensitive blood-brain barrier (BBB)-permeable near-infrared (NIR) probe, BTDN, was screened by tuning the electron-donating substituents to modulate the pKa values of benzothiadiazole-based derivatives. Endowed with the donor−acceptor−donor (D1−A−D2) architecture and strong intramolecular charge-transfer (ICT) characteristics, the BTDN probe exhibited high sensitivity to polarity change. The BTDN probe displayed suitable physicochemical properties such as a pKa of 7.47 and lipophilicity with a log P of 3.72 for favorable BBB-penetrating efficiency with a permeability percentage of 24.23%. In addition, the BTDN probe showed advantages for fluorescence imaging including NIR emission from 643 to 770 nm with the increased polarity, Stokes shift larger than 308 nm, comparable two-photon absorption capacity with an absorption cross-section of 10 GM at 870 nm, good biocompatibility, and robust photostability. Using this multifunctional BTDN probe, the dynamic fluorescence imaging of accumulation behaviors of LDs in BV2 microglia with neuroinflammation was performed, demonstrating that LD formation may serve as a potential biomarker for neuroinflammation. Furthermore, overproduced LDs within microglia were directly observed in vivo and in tissue sections from the brains of AD mice. This work not only provides an imaging tool for dynamically characterizing LD accumulation in microglia but also provides insights into the relationship between LD accumulation in microglia and AD pathogenesis.

Nanoarmored probiotics with inflammation targeting and scavenging activities without complex synthetic procedure is important for maintaining their native bioactivity, yet it remains a challenge. In this work, we demonstrated the multifunctional nanoparticle (QL@PS NP)-armored Lactobacillus rhamnosus (LAB) with inflammation targeting and regulation activity for inflammatory bowel disease (IBD) treatment. QL@PS NPs were assembled by quercetin (Que), lipoic acid (LA), and phosphatidylserine (PS), which could target macrophages and degrade in reactive oxygen species (ROS)-rich lesion sites, exhibiting excellent antioxidant and anti-inflammatory capability in vitro. QL@PS NPs were coated on the surface of thiolated LAB under a cell-friendly condition, and the resulting nanoarmored probiotic (LAB@NPs) could protect LAB from the gastrointestinal assaults and ROS damage. LAB@NPs are more likely to be up-taken by macrophages, scavenging oxidative stress and regulating the inflammatory microenvironment of colitis lesions through the synergistic effect of probiotics and QL@PS NPs. In vivo experimental results certified that LAB@NPs achieved notable lesion-specific therapeutic efficacy in mouse colitis models, significantly ameliorating colon shortening, reducing inflammatory reactions and pathological tissue damage. This work provides a facile and effective strategy to construct nanoarmored probiotics for therapy of IBD.

Bacterial pneumonia, a prevalent respiratory disease with high global morbidity and mortality rates, remains a formidable therapeutic challenge. Herein, pH/reactive oxygen species (ROS) dual-responsive zwitterionic polymer (PODEA-b-P(ROS-CA-EG)n) micelles are developed for bacterial pneumonia therapy. The zwitterionic shell can facilitate the micelles to effectively penetrate through the mucus. These micelles exhibit pH-responsive charge reversal performance, which is conducive to the cellular internalization and bacterial killing. Meanwhile, the micelles respond to the acid and overexpressed ROS microenvironment at the lesion site to release cinnamaldehyde (CA), enhance ROS generation, and activate an immune reaction to eliminate extracellular and intracellular bacteria collaboratively. In bacterial pneumonia, PODEA-b-P(ROS-CA-EG)n micelles can effectively eliminate bacteria and alleviate lung inflammation. These pH/ROS dual-responsive zwitterionic polymer micelles could provide a synergistic therapeutic strategy against bacterial pneumonia.

Ulcerative colitis (UC) is a lifelong inflammatory bowel disease affecting the rectum and the colon. Superoxide anion (O2•-), as the primary precursor of reactive oxygen species (ROS), is closely associated with the progression of UC. However, in vivo fast detection of O2•- in the alkaline microenvironment of UC remains a considerable challenge. Herein, a sequentially-activatable fluorescent probe, PT-3F, is engineered for fast fluorescence imaging of O2•- in an alkaline condition. The synthesized probe displays high selectivity, minimal background and rapid response to O2•-, enabling for in vivo fluorescence imaging of O2•- in PC-12 cells and colons of mice with UC.

Enantioselective discrimination of enantiomers is very important to reveal the function and concentration fluctuation of chiral isomers in biological processes and disease pathogenesis. It remains challenging to distinguish D/L-enantiomers because they possess identical chemical composition and very similar physicochemical properties. Norepinephrine (NE) is a chiral monoamine neurotransmitter that shows extensive physiological effects on both the peripheral and central nervous systems of mammals and plays significant roles in the pathogenesis of Alzheimer's disease (AD). However, specific fluorescent probes for direct enantioselective discrimination of D/L-NE have rarely been reported so far, although gold standard methods such as chiral high-performance liquid chromatography (HPLC) and circular dichroism (CD) spectroscopy have been established. In this study, we present an integrated and in situ activatable chiral D-NE probe, BTTD polymer dots (Pdots) derived from a chiral fluorescent conjugated polymer, for distinguishing D-NE from L-NE based on the defined chiral microenvironment. BTTD Pdots exhibited high selectivity over other amino neurotransmitters, including dopamine and epinephrine, fast response within 2 s, good biocompatibility, and favorable penetrating efficiency of 37.02% across the blood-brain barrier (BBB). BTTD Pdots were successfully applied to fluorescence imaging of the NE exocytosis process induced by a high concentration of K⁺, and also used to monitor D-NE levels in the brains of AD mice. The results reveal that the D-NE level is substantially lower in the brain with AD than in normal mice. This study provides a distinctive avenue for designing a chiral fluorescent probe for differentiating enantiomers through engineering a defined chiral microenvironment with clew-like polymer-derived Pdots.

Real-time monitoring of hepatic diseases is of paramount importance in the field of clinical biomedicine research. Methodologies based on the navigation of fluorescent probes for enabling both preoperative visualization of hepatic status and intraoperative delineation of lesion margins have been challenging in clinical applications. This study presents a persistently luminescent NIR-II fluorescent probe, DPTQ08-IDT polymer dots (Pdots), for real-time intraoperative visualization to guide hepatic resection and hepatic ischemia-reperfusion hemodynamic observation. The NIR-II DPTQ08-IDT Pdots emitted at 1050 nm were derived from donor (D)-acceptor (A) structured polymer DPTQ08-IDT, followed by coassembly with folic acid (FA). This probe exhibits a specific binding ability to folate receptor alpha (FRα), which is overexpressed in hepatic tumor cells. Through the specific targeted binding between FA and FRα, the probe achieves rapid hepatic accumulation and robust fluorescence signals in the NIR-II region. The proposed DPTQ08-IDT Pdots provide precise intraoperative guidance for hepatic resection via NIR-II fluorescence imaging. Additionally, this probe facilitates the observation of circulatory dynamics during hepatic ischemia-reperfusion, offering valuable insights into hepatic hemodynamics. This study advances liver-targeted Pdot-based fluorescent probes in the clinical application of liver diseases.