Abstract
In this work, a fluorescent probe, VanPI-CarE, with a vanillin–pyridine–imidazole core structure was developed for carboxylesterase (CarE) detection in macrophage polarization during bone homeostasis. The probe responded to CarE with a distinct fluorescence reporting signal at 490 nm upon excitation at 355 nm. Tests in solution showed the advantages of VanPI-CarE, including high sensitivity, excellent stability under various working conditions, high selectivity, and low cytotoxicity. Further confocal imaging indicated that VanPI-CarE enabled visualization of CarE level in living macrophages. The probe further revealed macrophage polarization in bone homeostasis under both induction and inhibition conditions via CarE detection. These findings provide meaningful insights for inflammation-related research.
1 Introduction
Bone homeostasis is an essential balance between bone formation and absorption, which is responsible for the generation, coloboma, and reconstruction of the bone tissues (; ). One pathway for generating bone cells is the conversion of immune-related cells after the induction of specific cytokines or agents, while the reverse process—conversion from bone cells back to immune-related cells—also occurs (; ). One typical case of conversion is macrophage polarization during bone homeostasis, which is closely associated with inflammation during differentiation to form the classic pro-inflammatory M1 macrophages and the alternative anti-inflammatory M2 macrophages (; ). M1 macrophages, which are commonly induced by Toll-like receptors (TLRs) or Th1 cytokines, exhibit strong antigen-presenting capabilities and secrete pro-inflammatory cytokines (; ). In particular, they are also the precursors of osteoclasts, which produce cytokines to induce bone resorption (). On the other hand, M2 macrophages promote tissue repair through processes such as immune tolerance, tissue remodeling, debris clearance, and immune regulation while also activating tumor angiogenesis, which facilitates tumor growth and immune escape (; ). In bone homeostasis, M2 macrophages stimulate differentiation and mineralization by producing osteogenic factors, after which the resulting cells, including mesenchymal stem cells (MSCs), complete bone formation (). Previous investigations revealed that macrophage polarization was closely related to lipid metabolism (). A key factor is oxidized low-density lipoprotein (ox-LDL), which activates macrophage polarization toward the M1 type by affecting TLRs and scavenger receptors (). Meanwhile, inflammation is promoted by cytokines such as interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α). For the fatty acids, the saturated species activate the NF-κB signaling pathway to induce M1-type macrophage polarization; on the other hand, the unsaturated species stimulate the peroxisome proliferator-activated receptor (PPAR) pathway to cause anti-inflammatory M2-type macrophage polarization (; ). Correspondingly, lipid metabolism in macrophage polarization during bone homeostasis has become a research hot spot.
Monitoring lipid metabolism commonly relies on the detection of the blood lipid substances, including total cholesterol (TC), triglycerides (TGs), low-density lipoprotein cholesterol (LDL-C), and high-density lipoprotein cholesterol (HDL-C) (; ). Further molecular and enzymatic indicators are urgently needed to fulfill the necessity of real-time and in situ detection. Among the potential candidates, carboxylesterase (CarE) has attracted the attention of researchers due to its significant role in lipid metabolism during endogenous generation, drug digestion, and exogenous toxicant intake (; ). As a key regulator, CarE mediates the hydrolysis of TGs, which has been studied in liver disorders, including fatty liver, alcoholic hepatitis, and hepatocellular carcinoma (HCC), and obesity-associated inflammatory diseases such as diabetes mellitus (DM) (; ; ). In consideration of its key role in both lipid and carbohydrate metabolism, CarE is a suitable indicator for both lipid-related and inflammation-related events. Therefore, CarE is a potential indicator for macrophage polarization during bone homeostasis. The detection of CarE has been investigated in hepatic and pulmonary cells, while the reports in bone-related induction remain a challenging trial (). Accordingly, for CarE detection, the current method is a blood biochemistry test, which requires extracorporeal operation (). The fluorescent probes, with advantageous features including high sensitivity, high specificity, and non-invasive imaging capability, have been introduced for the detection of many molecular indicators (). For CarE detection, in particular, the corresponding fluorescent probes have also been developed to suit the specific application scenarios (; ; ; ; ; ; ; ; ; ). One of the most reliable recognition groups for CarE is the carbamate group, which was inspired by inhibitors of acetylcholinesterase and butyrylcholinesterase (). Based on the above information, it is meaningful to develop novel fluorescent probes for CarE detection in macrophage polarization during bone homeostasis. With the introduction of the cooperative indicators, including blood calcium concentration and cytokines (IL-6 and TNF-α), the established functioning network might be referable.
In this work, after checking the previous investigations, a fluorescent probe with a vanillin–pyridine–imidazole core structure was developed for CarE detection in macrophage polarization during bone homeostasis (Figure 1). The prepared probe, VanPI-CarE, was named based on the subunits of its core structure, including vanillin, pyridine, and imidazole, and its detecting target, CarE. Recently, modification of the fluorophores has been inspired by natural products (; ; ; ; ). Among the reported moieties, vanillin was preferred because of its methoxy group, which serves as an inherent optical auxiliary group (; ). The probe was assembled from the modified fluorophore VanPI-OH, as referenced by and , and the reliable carbamate recognition group for CarE (). It was expected to show practical serviceability for the challenging trial of bone homeostasis-related inflammatory regulation, such as macrophage polarization. Tests in solution and imaging in induced macrophages were conducted.
FIGURE 1
2 Experimental procedure
2.1 General materials and methods
Commercially available chemicals and enzymes were purchased and used without further purification. In thin-layer chromatography (TLC) and column chromatographic separation, 300–400 mesh silica gel was purchased from Qingdao Haiyang Chemical Co., Ltd. (China). The cell lines used in this study were obtained from the American Type Culture Collection (ATCC) and stored in the central laboratory of the Jinhua Institute of Zhejiang University. The solution system, including phosphate-buffered saline (PBS), was prepared with pure water produced by the Milli-Q Reference Water Purification System (Merck, Darmstadt, Germany). Characterization was performed by nuclear magnetic resonance (NMR) spectroscopy on a Bruker DRX-600 Spectrometer (Germany) and high-resolution mass spectrometry (HRMS) on an AB SCIEX Triple-TOF 4600 System (United States). The UV-VIS spectra tests were conducted on a Shimadzu UV-2550 Spectrophotometer (Shimazu, Kyoto, Japan), while the fluorescence signals were measured on a Hitachi F-7000 Fluorescence Spectrophotometer (Japan). The confocal imaging experiments were performed on a Leica Mai Tai SP8 Microscope (Germany).
The probe VanPI-CarE was stored as a 1 mM stock solution, with dimethyl sulfoxide (DMSO) as the solvent. The solution system at a total volume of 200 µL for the detection consisted of 20 µL DMSO (containing the probe), 80 µL PBS (final concentration 10 mM, for preparing CarE), and 100 µL pure water (containing the aqueous analytes). Unless the condition was being tested, the working conditions were set as pH 7.4, incubation time 20 min, incubation temperature 37 °C, photomultiplier voltage 600 V, excitation/emission slit width 5 nm * 5 nm, and excitation wavelength 355 nm. The signal collection range in the confocal imaging experiments was 450 nm–600 nm in the green channel.
2.2 Synthesis of compounds
The chemical synthesis process of the probe VanPI-CarE is depicted in Figure 2. There were two main steps. At first, 15 mL of acetic acid was added to a 50-mL round-bottom flask to dissolve the reagents phenyl(pyridin-2-yl)methanone (0.27 g, 1.5 mmol), ammonium acetate (0.15 g, 2 mmol), and vanillin (0.23 g, 1.5 mmol). The reaction was carried out under reflux for 5 h, and its completion was monitored by TLC. Subsequently, ice water was added to the reaction system, and the precipitate was collected. After column chromatography (petroleum ether: ethyl acetate = 5:1), the fluorophore VanPI-OH was acquired as a yellow solid (yield 75.2%). The 1H NMR spectrum (600 MHz, CDCl3) showed signals at δ 9.79 (s, 1H), 8.18 (d, J = 7.3 Hz, 1H), 7.92 (d, J = 7.2 Hz, 2H), 7.81 (d, J = 9.3 Hz, 1H), 7.45 (t, J = 7.7 Hz, 2H), 7.35 (d, J = 1.8 Hz, 1H), 7.29 (t, J = 7.4 Hz, 1H), 7.28–7.24 (m, 1H), 7.01 (d, J = 8.0 Hz, 1H), 6.76 (dd, J = 9.7, 6.3 Hz, 1H), 6.55 (t, J = 7.1 Hz, 1H), and 3.91 (s, 3H). The 13C NMR spectrum (151 MHz, CDCl3) showed peaks at δ 147.35, 146.66, 138.27, 134.73, 131.40, 128.73, 127.33, 126.86, 126.56, 121.87, 120.91, 119.62, 119.03, 114.68. 114.53, 113.20, 111.90, and 56.08. HRMS (Q-TOF m/z) provided a calculated value of 317.1290 for [C20H17N2O2]+ and a found value of 317.1279.
FIGURE 2
Furthermore, 20 mL of dichloromethane (DCM) was added to a 50-mL round-bottom flask to dissolve VanPI-OH (0.5 mmol), N,N-dimethyl carbamic acid (0.5 mmol), 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDCI, 1 mmol), and 1-hydroxybenzotriazole (HOBt, 0.5 mmol). The reaction was carried out at room temperature for 5 h, and its completion was monitored by TLC. The solvent was vaporized, and following that, column chromatography (petroleum ether: ethyl acetate = 16:1) was conducted. The probe VanPI-CarE was acquired as a yellow solid (yield 48.6%). The 1H NMR spectrum (600 MHz, CDCl3) showed signals at δ 8.27 (d, J = 7.3 Hz, 1H), 7.96 (d, J = 7.3 Hz, 2H), 7.85 (d, J = 9.2 Hz, 1H), 7.50–7.48 (m, 3H), 7.38 (dd, J = 8.2, 1.9 Hz, 1H), 7.32 (t, J = 7.4 Hz, 1H), 7.26 (d, J = 8.1 Hz, 1H), 6.80 (dd, J = 9.2, 6.3 Hz, 1H), 6.59 (t, J = 6.5 Hz, 1H), 3.95 (s, 3H), 3.18 (s, 3H), and 3.06 (s, 3H). The 13C NMR spectrum (151 MHz, CDCl3) showed peaks at δ 154.57, 152.39, 141.16, 137.67, 134.86, 131.87, 128.75, 128.26, 127.73, 126.86, 126.61, 123.65, 121.92, 119.97, 119.81, 119.11, 113.35, 113.26, 56.28, 36.86, and 36.65. HRMS (Q-TOF m/z) provided a calculated value of 388.1661 for [C23H22N3O3]+ and a found value of 388.1643.
2.3 Determination of fluorescence quantum yields
The reference method using an ethanol solution of rhodamine B (10 μM, Φ = 0.69, λex = 365 nm) was employed to calculate the fluorescence quantum yield (FQY) values. In this study, the FQY values of the probe VanPI-CarE and the detection product VanPI-OH were 0.15 and 0.71, respectively.
2.4 Determination of the limit of detection
In this work, the limit of detection (LOD) was calculated using the formula LOD = 3σ/k, where the background noise σ was obtained from 25 independent tests of the solution system containing only the probe and the slope k was determined from the linear regression equation. Thus, σ = 0.4985, k = 88.52, and LOD = 0.017 U/mL.
2.5 Determination of cell viability and confocal imaging
Cell viability was tested on RAW264.7 (mouse monocyte macrophage leukemia cells) and MC3T3-E1 (mouse embryonic osteoblast precursor cells) using the thiazolyl blue (MTT) assay (). Absorbance at 570 nm was measured.
Moreover, RAW264.7 cells were incubated in Dulbecco’s modified Eagle’s medium (DMEM) with hydroxyethyl piperazine ethane sulfonic acid buffer (HEPES, pH 7.2), 10% fetal bovine serum (FBS), and 1% penicillin–streptomycin at 37 °C under a 5% CO2 atmosphere. HEPES was added to improve the solubility of receptor activator of nuclear factor-κB ligand (RANKL). The RAW264.7 cell line was chosen for its relevance to the study of macrophage polarization in bone homeostasis. The cells were divided into five groups. The first group served as the original condition, incubated with HEPES for 30 min, followed by incubation with the probe VanPI-CarE (10 μM) for 30 min, and then imaged. The second group served as the inhibited condition, incubated with the CarE inhibitor bis(4-nitrophenyl)phosphate (BNPP) at 1 μM for 30 min, followed by incubation with VanPI-CarE (10 μM) for 30 min, and then imaged. The third group served as the stimulated condition, which was pre-treated with oxidized low-density lipoprotein (ox-LDL) at 20 μg/mL during the last 12 h of culturing to induce the CarE level, incubated with VanPI-CarE (10 μM) for 30 min, and then imaged. The fourth group served as the bone homeostasis-related macrophage polarization condition, which was induced by RANKL (100 ng/mL) during the last 12 h of culturing (), incubated with HEPES for 30 min, followed by incubation with VanPI-CarE (10 μM) for 30 min, and then imaged. The fifth group served as the macrophage polarization-inhibited condition, which was induced by RANKL, treated with the RANKL inhibitor denosumab (1 μg/mL) during the last 1 h of culturing (), incubated with HEPES for 30 min, followed by incubation with VanPI-CarE (10 μM) for 30 min, and then imaged. The fluorescence signals in the green channel of 450 nm–600 nm were collected when the excitation wavelength was set to 355 nm.
3 Results and discussion
3.1 Chemical synthesis of VanPI-CarE
The general synthetic route of the probe VanPI-CarE is depicted in Figure 2 as comprising two main steps. The initial step was the formation of the fluorophore VanPI-CarE from the cyclization of vanillin, phenyl(pyridin-2-yl)methanone, and ammonium acetate (; ). The vanillin–pyridine–imidazole core structure was constructed thereby. The second step was anchoring the carbamate recognition onto the fluorophore to yield the probe VanPI-CarE. The structures of the probe and the fluorophore were confirmed by satisfactory characterization data (1H NMR, 13C NMR, and HRMS, Supplementary Figures S1–S6 in Supporting Information). The recognition mechanism was supported by previous reports and variations in the HRMS data.
3.2 Optical performance in solution system
When the optical performance was studied, the UV–VIS absorption and fluorescence spectra were examined to provide the initial information. In this work, the probe VanPI-CarE (10 μM) exhibited a visible peak at 530 nm (due to the frequency-doubling effect), while recognition with CarE (20 U/mL) for 20 min at 37 °C resulted in a decrease in the signal (Supplementary Figures S7a). More importantly, for the aspect of the fluorescence reporting signal, when the excitation wavelength was set to 355 nm, the probe VanPI-CarE (10 μM) was almost non-fluorescent, while recognition with CarE (20 U/mL) for 20 min at 37 °C caused a remarkable enhancement in the peak at 490 nm (Supplementary Figures S7b). The response scale referred an over 35-fold fluorescence enhancement, which was suitable for establishing the system of turning-on recognition. Based on the collection of both the absorbance and fluorescence data, the FQY values of the probe VanPI-CarE and the detection product VanPI-OH were 0.15 and 0.71, respectively. Since the basic signal variation during CarE recognition had been studied, the following experiments were carried out to examine the working conditions, including pH, incubation time, and temperature. Recognition of the enzymatic indicator is commonly affected by the pH condition. In this study, the probe VanPI-CarE showed no obvious fluorescence signal within the whole tested range of 3.0–12.0, while the fluorescence reporting signal with a certain intensity after recognition between VanPI-CarE and CarE remained stable in the range of 7.0–9.0 (Figure 3a). This result indicated the considerable potential for detection in physiological and pathological procedures. Meanwhile, since the recognition time is usually a significant factor, it was also tested by setting different checking points. Recognition of VanPI-CarE toward CarE was completed within 20 min, which is a shorter period than that in similar reports (Figure 3b). The time-dependent response followed the Michaelis–Menten model, with parameters including Vmax = 1,011 min−1 and Km = 1.185 U/mL, consistent with typical values of carboxylesterase (). For the condition of incubation temperature, VanPI-CarE itself showed no obvious fluorescence signal in the tested range of 25 °C–45 °C, while the fluorescence reporting signal remained stable in the range of 35 °C–40 °C (Supplementary Figures S8). This result was also consistent with the requirements of the physiological micro-environment.
FIGURE 3
After the working conditions were investigated, the correlation between the reporting signal intensity at 490 nm and the CarE level (0–20 U/mL) in the solution system containing VanPI-CarE (10 μM) was established. The upper limit of the CarE level was set at 20 U/mL because this level ensured a relatively transparent solution and fulfilled the requirements for physiological detection. As the CarE level increased gradually, the fluorescence reporting signal correspondingly enhanced, reaching a saturated value at a CarE level of 15 U/mL (Figures 3c, d). A linear correlation was found in the range of 0 U/mL–10 U/mL, with a Pearson’s r value of 0.9997 (Figure 3d Inner). Using the formula 3σ/k, the LOD value was determined to be 0.017 U/mL, indicating relatively high sensitivity. Both the linear range and the LOD value are suitable for the potential research scenarios in this work. Therefore, in the solution system, the probe VanPI-CarE showed potential optical capabilities for CarE detection.
3.3 Selectivity toward CarE
In the next step, the selectivity of the probe VanPI-CarE (10 µM) toward CarE (20 U/mL) was investigated. The most concerned species were the competing enzymes, including alkaline phosphatase (ALP), alanine aminotransferase (ALT), aspartate aminotransferase (AST), β-glucosidases (β-Glu), xanthine oxidase (XO), tyrosinase, trypsin, monoamine oxidase-A (MAO-A), monoamine oxidase-B (MAO-B), human serum albumin (HSA), and bovine serum albumin (BSA) from the similar physiological micro-environment of CarE (Figure 4a). In particular, the inhibition and induction agents in intracellular imaging, including BNPP, ox-LDL, RANKL, and denosumab, were involved. None of the tested species, except CarE, led to a remarkable enhancement of the fluorescence reporting signal. In consideration of their activity in physiological events, the reactive oxygen/nitrogen species (ROS/RNS), including NO, 1O2, ONOO−, HClO, OH, H2O2, and O2−, and anions, including Br−, F−, CO32−, HCO3−, SO42−, SO32−, and NO3−, were also tested in this section (Figure 4b). None of them caused any detectable fluorescence reporting signal. In further steps, the tests covered more analytes, including the usual amino acids (Ala, Arg, Asp, Asn, Gln, Gly, Glu, His, Ile, Leu, Lys, Met, Pro, Ser, Thr, Tyr, and Val; Figure 4c) and cations (Al3+, Ca2+, Cu2+, Fe3+, Fe2+, K+, Li+, Mg2+, Mn2+, Na+, Pb2+, Ti4+, and Zn2+; Figure 4d). None of the tested analytes produced a notable fluorescence reporting signal. Therefore, in the solution system, the high selectivity of the probe VanPI-CarE toward CarE was guaranteed.
FIGURE 4
3.4 Intracellular imaging for CarE
This work focused on carboxylesterase detection in macrophage polarization during bone homeostasis. Thus, bone homeostasis-related macrophages and precursor cells, including the RAW264.7 (Supplementary Figures S9a) and MC3T3-E1 (Supplementary Figures S9a) cell lines, were tested for cell viability using a standard MTT assay. After 24 h of incubation, both the cell lines retained over 90% cell viability when the working concentration of the probe gradually increased to 50 µM. Thus, VanPI-CarE inferred low cytotoxicity for imaging in living macrophages.
RAW264.7 cells were maintained in an uninduced state before the confocal experiments because bone homeostasis-related macrophage polarization requires induction during culturing. The cells were divided into five groups according to the different treatment conditions. The first group, which represented the original condition, was incubated with HEPES for 30 min, followed by incubation with the probe VanPI-CarE (10 μM) for 30 min, and then imaged (Figures 5a–c). Since the living RAW264.7 cells bore a certain level of CarE, the fluorescence reporting signal was observed in the green channel. In the second group, in which CarE was inhibited by BNPP (1 μM), the following incubation with VanPI-CarE resulted in a remarkable decrease in the fluorescence reporting signal (Figures 5d–f). On the contrary, the third group was pre-treated with ox-LDL (20 μg/mL) during the last 12 h of culturing before being incubated with VanPI-CarE for 30 min and then imaged (Figures 5g–i). In this group, the CarE level was stimulated, and the fluorescence reporting signal was notably enhanced. The results from the initial three groups suggested that VanPI-CarE was capable of visualizing the CarE levels in living macrophages under both inhibition and activation conditions. Then, the following two groups were associated with macrophage polarization during bone homeostasis. The fourth group, which served as the bone homeostasis-related macrophage polarization condition, was induced by RANKL (100 ng/mL) during the last 12 h of culturing before being incubated with HEPES for 30 min, followed by incubation with VanPI-CarE (10 μM) for 30 min, and then imaged (Figures 5j–l). Correspondingly, the fluorescence reporting signal in the green channel exhibited a remarkable decrease, which was consistent with the fact that the M1-type macrophage polarization process induced by ox-LDL caused inflammation and affected the metabolism of fatty acids (). Finally, the fifth group was established on the basis of the fourth condition. After induction with RANKL, the cells were treated with the RANKL inhibitor denosumab (1 μg/mL) during the last 1 h of culturing before incubation with HEPES and VanPI-CarE (Figures 5m–o). The fluorescence reporting signal subsequently indicated a recovery close to the original uninduced condition in the first group, suggesting a corresponding restoration of the CarE level. Therefore, VanPI-CarE achieved reflection of macrophage polarization in bone homeostasis, regardless of induction or inhibition, by visualizing the CarE level.
FIGURE 5
4 Conclusion
In conclusion, on the basis of the investigation of previous research, a fluorescent probe with a vanillin–pyridine–imidazole core structure was developed for CarE detection in macrophage polarization during bone homeostasis. The acquired probe VanPI-CarE exhibited an obvious fluorescence reporting signal at 490 nm upon excitation at 355 nm. In the solution system, the FQY values of the probe VanPI-CarE and the detection product VanPI-OH were 0.15 and 0.71, respectively. After the investigation of the working conditions, including pH, incubation time, and temperature, the results indicated that the fluorescence reporting signal reached a saturated value within 20 min and remained stable at pH 7.0–9.0 and 35 °C–40 °C. The optical performance was beneficial for fulfilling the requirements of the physiological micro-environment. The intensity of the fluorescence reporting signal at 490 nm exhibited a dose-dependent enhancement along with an increase in the CarE level. A linear correlation was found in the range of 0 U/mL–10 U/mL, and the LOD value was determined to be 0.017 U/mL, which suggested relatively high sensitivity. VanPI-CarE also showed high selectivity toward CarE over competing species and low cytotoxicity toward bone homeostasis-related macrophages and precursor cells. Moreover, the confocal imaging results suggested that VanPI-CarE successfully visualized the CarE level in living macrophages under both inhibition and activation conditions. Furthermore, in macrophage polarization during bone homeostasis, both the induction and inhibition conditions were reflected by VanPI-CarE via CarE detection. Future research should focus on the enhancement of the fluorescence reporting signal intensity in imaging due to the relatively short emission wavelength. The possible solutions might include the precise modification of the substitutes and enrichment with functional carriers (; ). This work provides valuable information on carboxylesterase detection in macrophage polarization during bone homeostasis, which is relevant for inflammation-related research.
Statements
Data availability statement
The datasets presented in this study can be found in online repositories. The names of the repository/repositories and accession number(s) can be found in the article/Supplementary Material.
Ethics statement
Ethical approval was not required for the studies on humans in accordance with the local legislation and institutional requirements because only commercially available established cell lines were used. Ethical approval was not required for the studies on animals in accordance with the local legislation and institutional requirements because only commercially available established cell lines were used.
Author contributions
HX: Formal Analysis, Methodology, Writing – original draft. XW: Formal Analysis, Methodology, Writing – original draft. WH: Formal Analysis, Visualization, Writing – review and editing. XJ: Investigation, Methodology, Validation, Writing – review and editing. XH: Investigation, Supervision, Validation, Writing – review and editing. CW: Conceptualization, Methodology, Project administration, Supervision, Validation, Writing – review and editing.
Funding
The author(s) declare that no financial support was received for the research and/or publication of this article.
Conflict of interest
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
Generative AI statement
The author(s) declare that no Generative AI was used in the creation of this manuscript.
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Supplementary material
The Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/fchem.2025.1666238/full#supplementary-material
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Summary
Keywords
carboxylesterase detection, macrophage polarization, fluorescence probe, intracellular imaging, bone homeostasis
Citation
Xia H, Wang X, Huang W, Jiang X, Han X and Wang C (2025) A fluorescent probe with a vanillin–pyridine–imidazole core structure for carboxylesterase detection in macrophage polarization during bone homeostasis. Front. Chem. 13:1666238. doi: 10.3389/fchem.2025.1666238
Received
15 July 2025
Accepted
07 August 2025
Published
21 August 2025
Volume
13 - 2025
Edited by
Bing Yang, Nantong University, China
Reviewed by
Ramesh Maruthi Chingle, National Institutes of Health (NIH), United States
Hualin Yang, Yangtze University, China
Ruojun Man, Guangxi Minzu University, China
Updates
Copyright
© 2025 Xia, Wang, Huang, Jiang, Han and Wang.
This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
*Correspondence: Xionggao Han, xionggao414@zju-jhi.com; Chaoyue Wang, wangchaoyue2023@126.com
Disclaimer
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