Fig.1 AIE molecular probes based on sulfonamide modification: structural design, pH-responsive mechanism, and performance characterization. (a) Synthetic route for the preparation of TPE-based fluorescent probes, including TPE-SA, TPE-SAC, and TPE-SDOX. (b) Schematic diagram of the reversible and pH-responsive fluorescence switching mechanism of TPE-SDOX. The probe exhibits aggregation-induced luminescence (“ on ”state) at pH <6.8 and fluorescence quenching (“ off ”state) at pH >6.8, thereby achieving reversible optical behavior. (c) Emission spectra of TPE-SDOX in DMSO/H2O mixtures with increasing water fractions (fw). (d) Plot of normalized fluorescence intensity (I/I0) of TPE-SDOX versus water fraction (fw) in DMSO/H2O mixtures, where I0 and I denote the fluorescence intensities in pure DMSO (fw = 0%) and mixed solvents, respectively. Inset: fluorescence images of TPE-SDOX in pure DMSO and in DMSO/H2O (fw = 98%) under UV light (λ = 365 nm, 20 µm/mL). (e) Observation of the Tyndall effect for TPE-SDOX in pure DMSO, DMSO/H2O (fw = 98%), and pH 7.4 buffer solution (20 µm/mL), indicating aggregation behavior. (f) Fluorescence emission spectra of TPE-SDOX recorded in buffer solutions of varying pH values. (g) Quantitative analysis of the fluorescence intensity of TPE-SDOX under different pH conditions. (h) Fluorescence images of TPE-SDOX in buffer solutions with different pH values under UV illumination (λ = 365 nm, probe concentration: 20 µm/mL). (i) Zeta potential measurements of H4TCPE, TPE-SA, TPE-SAC, and TPE-SDOX in buffer solutions at pH 7.4 and pH 6.5 (20 µm/mL), reflecting their surface charge variation under different pH conditions. (j) Reversible fluorescence switching of TPE-SDOX between acidic (fluorescence “ on ”) and basic (fluorescence “ off ”) conditions (λ = 365 nm). (k) Fluorescence stability of TPE-SDOX in acidic PBS and DMEM media under the “ on ” (acidic) state (λ = 365 nm).#

为了在理论层面阐明其发光与响应机制，研究团队进行了密度泛函理论与含时密度泛函理论计算。如图2所示，量子化学计算表明，改性后的探针在基态与激发态之间保持了极小的能隙，证明磺酰胺基团的修饰并未破坏四苯基乙烯核心的AIE发光本征特性。通过静电势分布与静电电荷分析发现，探针中磺酰胺氮原子的电荷密度大小与其酸碱解离常数呈现出高度的线性相关性，这在分子轨道层面上验证了阶梯式酸碱响应设计的合理性与准确性。

Fig.2 Computational insights validating experimental findings. (a) HOMO and LUMO orbital diagrams of TPE-SDOX in the ground state (S0) and excited state (S1). (b) Comparison of the HOMO and LUMO energy levels in the excited state (S1) of the synthesized fluorescent probes TPE-SA, TPE-SAC, and TPE-SDOX with those of previously reported TPE derivatives (TPE-NPPB, THTPE, and TPE-Cl). (c) Electrostatic potential distribution of deprotonated and protonated nitrogen atoms on the TPE-SA, TPE-SAC, and TPE-SDOX probes. (d) Correlation between Mulliken charge on deprotonated/protonated nitrogen atoms and pKa values for TPE-SA, TPE-SAC, and TPE-SDOX probes.#

随后，研究团队将这三种AIE探针分别共价引入由甲基丙烯酰氧基乙基磺基甜菜碱与聚乙二醇二甲基丙烯酸酯构成的两性离子双网络水凝胶中，制备出兼具良好生物相容性与组织粘附力的荧光水凝胶薄膜。如图3所示，得益于两性离子基质优异的亲水性与柔韧性，水凝胶薄膜可承受高达600%的拉伸应变，并能紧密贴合于动态运动的皮肤表面。在图案化写入与擦除实验中，水凝胶展示出极佳的可逆酸碱响应循环稳定性，且在模拟伤口渗出液与复杂蛋白质环境中保持了极低非特异性蛋白吸附和良好的荧光背景抗干扰能力。

Fig.3 pH-responsive AIE hydrogel indicator films for reversible fluorescence modulation and skin-conformal adhesion. (a) Schematic of the pH-regulated emission mechanism of AIE probes encapsulated in an SBMA-based hydrogel network (crosslinked with PEGDMA). Variation of pH relative to the probe pKa modulates the aggregation/dispersed state of the AIE molecules, leading to fluorescence switching under UV irradiation. (b) Reversible writing-erasing cycles enabled by pH alternation: fluorescent patterns are generated at pH 5.5 (“writing”) and erased at pH 7.4 (“erasure”), demonstrating repeatable information recording. (c) Representative photographs showing reversible optical/fluorescence changes during a pH cycle (5.5→7.4→5.5). (d) Fluorescence images of pristine SBMA hydrogel and AIE-hydrogel composites (S@T-A, S@T-C and S@T-X) after immersion in PBS buffers with the indicated pH values. (e) Demonstration of skin adhesion and mechanical compliance of the hydrogel film, including conformal attachment and stretchability, shown under ambient light and UV illumination.#

在三种不同的细菌感染皮肤创伤模型（金黄色葡萄球菌、铜绿假单胞菌和大肠杆菌）中，研究团队深入评估了水凝胶薄膜的实时监测能力。如图4所示，涂覆于创面的水凝胶薄膜随着伤口微环境由酸性向中性转变，表现出清晰的阶梯式荧光淬灭现象。微电极测量与组织细菌计数结果表明，S@T-X水凝胶在pH 6.8处的荧光消失与创面细菌载量降至临床感染阈值以下高度重合。组织学与免疫荧光分析进一步证实，S@T-X荧光熄灭时，创面促炎细胞因子TNF-α和IL-6的表达量大幅下降超过90%，而细胞增殖标志物Ki67阳性细胞数显着增加，这表明pH 6.8处的光学信号改变能够精准指示伤口由炎症期向增殖期的生物学跨越。

Fig.4 Fluorescence monitoring of pH-responsive hydrogels in bacterial infection models. (a) Representative wound photographs and hydrogel fluorescence images in the S. aureus infection model. The blue color scale indicates fluorescence intensity. (b) Time-dependent fluorescence intensity heatmap of S@T-A, S@T-C, and S@T-X hydrogels. (c–e) Bacterial burden and wound pH changes in S. aureus-, P. aeruginosa-, and E. coli-infected wounds, respectively. Bacterial burden is shown in blue as CFU × 105 cm−2, and wound pH is shown in green. (f) H&E staining, TNF-α/DAPI immunofluorescence, IL-6 immunohistochemical staining, and Ki67 immunohistochemical staining of S. aureus-infected wounds monitored with S@T-X on Days 6–9. Arrows indicate representative positive signals. (g–i) Quantification of relative TNF-α fluorescence intensity, IL-6-positive nuclei, and Ki67-positive nuclei. Scale bars: 100 µm for H&E and Ki67 images, and 50 µm for TNF-α/DAPI and IL-6 images. Data are presented as mean ± SD, n = 3 independent biological replicates; at least three representative fields were analyzed per replicate for TNF-α, IL-6, and Ki67 quantification. Statistical significance was determined by one-way ANOVA with Tukey’s post hoc test; *p <0.05, **p <0.01, ***p <0.001.#

基于这一精准的时间窗口，研究团队将万古霉素或环丙沙星包载于水凝胶中，建立了荧光指导的抗生素精准停药策略，并将其与持续给药（过度治疗）及早期停药（治疗不足）两组进行了对比。如图5所示，在金黄色葡萄球菌和铜绿假单胞菌感染模型中，以S@T-X荧光熄灭作为停药指令的响应式停药组在第14天达到了97.6%的伤口愈合率，其愈合效果与持续给药组完全相当，同时成功减少了41.3%的抗生素用量。相比之下，依据低pKa水凝胶（S@T-A或S@T-C）信号过早停药的组别则出现了严重的细菌残留和愈合迟缓。在大肠杆菌感染模型中，由于细菌代谢产氨导致微环境提前碱化，研究团队通过将停药时间顺延24小时，同样实现了完美的感染清除与组织修复。

Fig.5 Integration of antibiotic therapy with pH-responsive fluorescent hydrogels enables precise infection monitoring and treatment. (a) Schematic illustration of the precise antibiotic management and wound healing process regulated by the pH-responsive S@T-X hydrogel. (b) Representative wound images showing continuous dosing and fluorescence-guided on-demand discontinuation (Ⓡ) strategies, simulating timely cessation of antibiotics after fluorescence disappearance. (c) Representative images and statistical analysis (Figure i–iv) of wound bacterial cultures from days 5–8 across hydrogel-treated groups, assessing the effects of early antibiotic cessation on infection control (mean ± standard deviation, n = 6; **p <0.01, ***p <0.001). (d) Wound healing simulation under antibiotic management across different treatment groups. (e) Quantitative comparison of wound healing areas on days 7 and 14 among S@T-A@VA, S@T-C@VA, S@T-X@VA, and S@T-X@VA groups. Data are presented as mean ± SD, n = 3 independent wounds per group. Statistical significance was determined by one-way ANOVA followed by Tukey’s post hoc test; *p <0.05, **p <0.01, ***p <0.001.#

深度的组织学与免疫学检测进一步揭示了精准停药在组织再生层面的独特优势。如图6所示，第14天的组织切片显示，荧光指导的停药组展现出完整的再上皮化、结构规整的新生胶面分布以及生理性的毛细血管密度。令人意外的是，持续抗生素给药的过度治疗组反而表现出新生血管网络紊乱、α-肌动蛋白过表达导致的纤维化倾向，以及异常升高的嗜酸性粒细胞浸润。这一发现有力证明了过度的抗生素暴露会破坏伤口微环境平衡并阻碍组织重塑，而基于pH 6.8临界点的及时停药则能顺应生理恢复节奏，实现高质量的创面修复。

Fig.6 Histological and immunofluorescence evaluation of wound healing under different antibiotic treatment strategies. (a) H&E and Masson’s trichrome staining of wound tissues on day 14. Dashed boxes indicate the magnified regions. (b,c) DAPI/CD31 immunofluorescence staining and quantitative analysis of vascular endothelial cells. (d,e) DAPI/α-SMA immunofluorescence staining and quantitative analysis of myofibroblast activation. (f,g) Wright’s staining and quantitative analysis of eosinophilic neutrophils. Scale bars: 200 µm for low-magnification H&E/Masson images, 100 µm for magnified H&E/Masson images, 50 µm for CD31 and α-SMA immunofluorescence images, and 10 µm for Wright’s staining images. Data are presented as mean ± SD, n = 3 independent biological replicates. For histological, immunofluorescence, and Wright’s staining quantification, at least three representative fields were analyzed for each biological replicate. Statistical significance was determined by one-way ANOVA with Tukey’s post hoc test; *p <0.05, **p <0.01, ***p <0.001. S@T-X@VA: continuous administration group; S@T-X@VA: fluorescence-guided withdrawal group; SBMA: blank hydrogel control group.#