English

• Photodynamic therapy (PDT) is widely used in the fields of antibacterial due to its non-invasive, low-cost modalities and lack of resistance after multiple sessions of therapy [1–9]. At present, PDT is usually associated with harmless low-intensity light by photosensitizer (PS) to stimulate the generation of toxic reactive oxygen species (ROS), including singlet oxygen (¹O₂) [10], hydroxyl radicals (·OH) [11] and superoxide radicals (·O₂⁻) [12, 13], in which the development of highly active PS plays a critical role. Conventional PSs can be divided into two main categories: inorganic PSs and organic PSs [14–18]. In the last few years, inorganic PSs have been widely used in PDT due to their good photostability. For example, layer double hydroxide-based nanomaterials [19–22], Cu_2−xS nanocrystals [23], Au nanocages [24], BiAgOS nanoparticles [25] have been reported as efficient PSs for PDT. However, these reported inorganic PSs are usually suffering from poor efficiency in the generation of ROS, thus hampering their application in antimicrobial and anti-tumour therapy. Organic PSs (e.g., porphyrins, phenothiazinium salts, and cyanine dyes) have many advantages, including good biocompatibility, ease of modulation and avoidance of heavy metal accumulation, and have demonstrated considerable antimicrobial therapeutic efficacy [26–30]. Due to their high photoconversion efficiency, ¹O₂ quantum yield and ease of chemical modification, porphyrin-based PSs are the most studied organic PSs in biomedicine [31–34]. However, porphyrin-based compounds have been limited in PDT due to their poor solubility in aqueous media. To achieve effective antimicrobial properties, adding porphyrin or porphyrin derivatives to the porous scaffold creates an ordered scaffold that improves its water solubility and stability.

  As an emerging crystalline porous material, metal-organic frameworks (MOFs) are attractive compounds for various applications (e.g., biomedicine, catalysis, and energy) because of their high surface area, adjustable composition, homogeneity of pore size, and so on [35–57]. Porphyrin-based MOFs, due to the synergistic effect of metal-linker bridging units, can achieve optimized photonic functionality and light-harvesting ability of porphyrins, which is assembled by coordination between porphyrin and metal ions, thus resulting in high photosensitizer loading capacity without self-quenching [58–63]. Among them, porphyrin-based MOFs synthesized from meso‑tetra(4-carboxyphenyl)porphyrin (TCPP) have been widely reported to have excellent PDT performance [59–62]. For example, Wang et al. used PCN-224 (Zr-TCPP MOF) nanoparticles as a light-sensitive agent to construct a multi-modal antibacterial platform by loading vanaglucin, which releases large amounts of ¹O₂ in visible light, achieving effective antibacterial effect [61]. Wan et al. created Mn-TCPP nanoparticles with regulated ROS production and GSH depletion, which can considerably improve the efficacy of photodynamic treatment [62]. Although many porphyrin-based MOFs have been widely used in PDT, most of them are bulk materials and nanoparticles, with a focus on anti-tumor effects. There are still few reports on the controlled synthesis of 2D MOF nanosheets for photodynamic antimicrobial applications. In comparison with bulk or nanoparticle MOF, it can be an ideal antimicrobial material due to its abundant active sites and large surface area [63–65]. Previously, we successfully explored the size engineering of 2D MOF nanosheets for enhanced photodynamic antimicrobial therapy, suggesting that the photodynamic activity of MOF increases when the size reduces [65]. However, the technique of controlled synthesis of 2D MOF nanosheets is still a challenge to overcome, as it usually requires the addition of large amounts of surfactants (e.g., polyvinylpyrrolidone (PVP) and hexadecyltrimethylammonium bromide (CTAB)) [66–68]. Although the surface active agent has an outstanding ability to control the growth of crystals, its leftovers after the reaction are difficult to remove, affecting the purity of the material. How to achieve simple and controllable synthesis of 2D MOF nanosheets in the absence of surfactants and apply them to PDT needs to be further explored.

  Herein, we report on the controlled synthesis of 2D In-TCPP nanosheets as an efficient photosensitizer to enhance photodynamic antibacterial therapy via a simple solvent-mediated synthesis method (Scheme 1). The 2D In-TCPP nanosheets morphology can be readily regulated through varying the ratio of water to N,N-dimethylformamide (DMF) with the appropriate assistance of pyridine, obviating the necessity for surfactant addition. Notably, we used the pyridine N-group as a tool for domain-limited growth of In-TCPP nanosheets to achieve the bulk-to-nanosheet transition. Compared to In-TCPP bulk, it was found that 2D In-TCPP nanosheets could produce more ¹O₂ under a 660 nm laser irradiation, indicating that the smaller nanosheets possess more active sites for photocatalysis and can greatly improve the antibacterial photodynamic therapeutic effect. In vitro and in vivo experiments have shown that 2D In-TCPP nanosheets have excellent sterilization and low levels of biotoxicity, which can accelerate wound healing under the radiation of 660 nm laser. Therefore, 2D In-TCPP nanosheets can be used as highly effective PSs to enhance photodynamic antimicrobial therapy.

  Scheme 1

  

  Scheme 1.  Schematic demonstration of the controlled synthesis of 2D In-TCPP nanosheets and their efficient photodynamic antibacterial.

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  In-TCPP bulk MOFs were synthesized at high temperature (180 ℃) in pure DMF for using a simple solvothermal method, following a previously established procedure (see Experimental Section in Supporting information) [67]. As can be seen from the scanning electron microscopy (SEM) image (Fig. S1a in Supporting information), the In-TCPP bulk crystals exhibit an irregular cubic structure with a diameter of up to 10 µm. After reducing the reaction temperature to 100 ℃ and reacting for 4 h, we found that the In-TCPP MOF synthesized in pure DMF exhibited irregular sheet-like morphology with a vertical size ranging from 50 nm to 300 nm (Fig. S2a in Supporting information). In order to obtain regular and homogeneous-shaped In-TCPP nanosheets, the effect of different reaction solvents was investigated. With the presence of pyridine (200 µL), a small quantity of water (0.5 mL) was introduced into DMF (4.5 mL), resulting in a reduction in the In-TCPP MOF, but the boundaries of the nanosheets became blurred and showed obvious adhesion (Fig. S2b in Supporting information). At the same pyridine content, further increasing the relative water content (DMF/water = 1:9, v/v) leads to the formation of regularly dispersed nanosheets with a diameter ranging from 70 nm to 150 nm (Figs. 1a and b, Fig. S2c in Supporting information). When the reaction solvent is pure water, In-TCPP MOF still showed a regular and thin nanosheet structure, but its lateral size of around 500 nm is the largest of all synthesized In-TCPP (Fig. S2d in Supporting information). These results demonstrated that the relative ratio of water and DMF, as well as the addition of pyridine, plays a crucial role in the growth of regular In-TCPP nanosheets. To investigate the effect of pyridine dosage on the morphology of In-TCPP, we fixed the content of water and DMF at a ratio of 1:9 (v/v), and then added varying amounts of pyridine. In the absence of pyridine in the solvent, the In-TCPP MOF appeared as uniform nanorods measuring 50–150 nm in length (Fig. S3a in Supporting information). After adding 50 µL of pyridine to the solvent (DMF/water = 1:9, v/v), the morphology of In-TCPP transformed from nanorods to irregular nanosheets/nanoparticles (Fig. S3b in Supporting information). Subsequently, the nanoparticles lost their morphology and the nanosheets became uniform and regular when the pyridine amount was raised to 200 µL (Fig. S3c in Supporting information). Once the pyridine content reaches 400 µL, it is accompanied by the formation of large size and irregular nanosheets (Fig. S3d in Supporting information). Therefore, the uniform In-TCPP nanosheets were obtained at a pyridine content of 200 µL. In order to further validate the necessity of adding pyridine for the synthesis of 2D In-TCPP nanosheets, we attempted to modulate the morphology of In-TCPP using different ratios of water and DMF solutions without the addition of pyridine. It should be noted that when the solvent is pure water, the synthesis of In-TCPP MOF fails due to the poor solubility of TCPP in water. When only 0.5 mL of DMF was added, the solubility of TCPP in the reaction increased, and it presents as nanorods without the addition of pyridine (Fig. S4a in Supporting information). As the ratio of DMF to water was 9:1 and 5:0, the In-TCPP nanorods gradually evolved into nanosheets. Nevertheless, the resulting In-TCPP nanosheets displayed an inhomogeneous and significant aggregated (Figs. S4b and c in Supporting information). The results showed that pyridine can limit the growth of In-TCPP, which leads to a morphology transformation from nanorods to nanosheets, thus achieving the purpose of controlling its morphology [69, 70]. This is due to the fact that the regulator pyridine can effectively limit the growth of 2D In-TCPP nanosheets along the vertical direction. The uniform nanosheet morphology will also be destroyed by the addition of excessive pyridine. It is worth noting that both pyridine and DMF increase the solubility of TCPP in the reaction process. Therefore, by adjusting the dosage of pyridine, DMF, and water, In-TCPP nanosheets with a regular uniform morphology can be synthesized.

  Figure 1

  

  Figure 1.  (a, b) The SEM, (c) TEM, (d) HRTEM and (e) AFM height images of 2D In-TCPP nanosheets. (f) HAADF-STEM image and (g) its corresponding EDX element mapping images of 2D In-TCPP nanosheets.

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  Based on the conclusions of the SEM characterization data, the morphology of the 2D In-TCPP nanosheets has been further investigated by means of transmission electron microscopy (TEM). The TEM image of the resulting 2D In-TCPP nanosheets (Fig. 1c) shows regular nanosheet as well as the SEM image (Fig. 1b). A continuous lattice fringe is visible in the high-resolution TEM (HRTEM) image of the 2D In-TCPP nanosheets, and the measured lattice spacing is 1.76 nm, which corresponds to the (021) crystal plane of the 2D In-TCPP crystals (Fig. 1d) [71]. Atomic force microscopy (AFM) indicated that the thickness of the 2D In-TCPP nanosheets was 21.5–27.4 nm (Fig. 1e and Fig. S6 in Supporting information). The high angle annular dark field scanning transmission electron microscopy (HAADF-STEM) image further reveals that the obtained In-TCPP exhibits a rhombic sheet-like morphology (Fig. 1f). The analysis results of energy-dispersive X-ray (EDX) spectroscopy mapping visualized a uniform distribution of C, N, O and In elements throughout the 2D In-TCPP nanosheets (Fig. 1g).

  The element valence states of the 2D In-TCPP nanosheets were verified by X-ray photoelectron spectroscopy (XPS). From the characteristic peaks observed in the full spectrum of XPS, it can be deduced that the presence of C, N, O, and In elements is confirmed in In-TCPP nanosheets (Fig. S7a in Supporting information). The C 1s XPS peaks of the 2D In-TCPP nanosheets presented two peaks, which are 284.8 and 288.8 eV, attributed to C=C and C-O (Fig. S7b in Supporting information). The O 1s XPS spectra of the In-TCPP nanosheets exhibited a main peak located at 532.2 eV (Fig. S7c in Supporting information). The N 1s XPS peaks of the In-TCPP nanosheets at 400.0 and 397.9 eV were attributed to the C-N and =N- bonds of the porphyrin units (Fig. 2a), respectively. As shown in Fig. 2b, the valence state of the In ions in In-TCPP was +3, as indicated by the XPS peaks of In 3d at 453.2 and 445.7 eV [71]. Obviously, the information consistent with the above can be obtained from the XPS diagram of In-TCPP bulk (Fig. S8 in Supporting information). It should be noted that the N 1s XPS spectrum of In-TCPP bulk exhibits a stronger peak at the binding energy of 398.0 eV, which may be attributed to the influence of DMF in the lattice of In-TCPP crystals [72]. Meanwhile, we conducted further structural characterization of them through X-ray diffraction (XRD). It was found that the XRD peaks of In-TCPP bulk and 2D In-TCPP nanosheets synthesized through solvent modulation, matched well with the simulated and measured peaks of In-TCPP single crystals (Fig. 2c and Fig. S1b in Supporting information). The XRD pattern exhibits sharp diffraction peaks at 7.5°, 12.7°, and 15.0°, which can be correspondingly attributed to the (021), (110), and (042) facets of In-TCPP MOF. In addition, the diffraction peaks of In-TCPP MOF synthesized under different solvent ratios all match well with the simulated peaks (Fig. S5 in Supporting information). This indicates that the change in organic solvent and the addition of pyridine have no effect on the structure of In-TCPP MOF.

  Figure 2

  

  Figure 2.  (a) The N 1s and (b) In 3d XPS spectra of 2D In-TCPP nanosheets. (c) XRD patterns of 2D In-TCPP nanosheets. (d) The fluorescence spectra of SOSG treated with 2D In-TCPP (50 µg/mL) by irradiation using a 660 nm laser for different times (0–10 min) at 0.5 W/cm². (e) Fluorescence changes of SOSG at 532 nm treated with PBS, In-TCPP (50 µg/mL) bulk and nanosheets by irradiation using a 660 nm laser for different times. (f) The UV–vis spectra of ABDA solution (100 µmol/L) with the addition of 2D In-TCPP (50 µg/mL) under a 660 nm laser irradiation (0.5 W/cm²) for different times. (g) The UV–vis spectra change of ABDA at 380 nm treated with PBS, In-TCPP (50 µg/mL) bulk and nanosheets for different times. The ESR spectra of In-TCPP (h) bulk and (i) nanosheets under different illumination times in the presence of ¹O₂ scavenger (TEMP).

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  In-TCPP is porphyrin-based photosensitizers that produce ¹O₂ for photodynamic therapy (PDT). Therefore, the photodynamic effects of the In-TCPP nanosheets and bulk crystals were monitored under a 660 nm laser (0.5 W/cm²) irradiation. The ROS production of the In-TCPP nanosheets and bulk crystals was investigated by the fluorescence (FL), UV spectrometry and electron spin resonance (ESR) using different probes or trapping agents. For FL, singlet oxygen sensor green (SOSG) was used as a probe for the detection of ¹O₂ generation. The free SOSG does not exhibit fluorescence unless it comes into contact with ¹O₂, and the intensity of fluorescence is directly related to the concentration of ¹O₂, with a maximum wavelength of 532 nm (Fig. S9a in Supporting information). Compared to free SOSG, the In-TCPP bulk-treated SOSG showed a sustained increase in fluorescence intensity under 660 nm laser irradiation (0.5 W/cm²) for different times (Fig. S9b in Supporting information). Promisingly, the fluorescence intensity of the SOSG treated with In-TCPP nanosheets showed a significant increase under the same laser conditions (Fig. 2d), and its fluorescence intensity was 2.3 times higher than that of In-TCPP bulk-treated SOSG when the light was radiated for 10 min (Fig. 2e). It can be seen that In-TCPP nanosheets have a stronger ¹O₂ generating capacity than In-TCPP bulk in a short period of time. This is due to the greater number of photoactive sites on the surface of In-TCPP, which enhances its photodynamic properties.

  In addition, ¹O₂ generation of In-TCPP was further detected by UV using 9, 10-anthracenediyl-bis(methylene) dimalonic acid (ABDA) as an indicator. The principle is that ABDA reacts with ¹O₂ to form endoperoxides and shows a tendency of decreasing absorption in the UV spectrum. Obviously, the UV absorption of the free ABDA solution at 340–400 nm remains almost unchanged with the prolongation of laser irradiation time (Fig. S10a in Supporting information). Although the In-TCPP bulk shows a decrease in the UV absorption peak at 380 nm after laser radiation, its absorbance only decreases by 0.14 after 10 min of illumination (Fig. S10b in Supporting information). In contrast, the UV absorbance curve of ABDA treated with In-TCPP nanosheets significantly dropped upon laser exposure, decreasing by 0.63 after 10 min (Fig. 2f). As shown in Fig. 2g, the minimum UV absorption intensity at 380 nm of ABDA treated with In-TCPP nanosheet was much lower than free ABDA and that treated with In-TCPP bulk.

  As an effective experimental tool for the detection of free radicals, ESR with 2, 2, 6, 6-tetramethylpiperidine (TEMP) as the trapping agent was further used to detect ¹O₂ generation by In-TCPP nanosheets. As shown in Fig. S11 (Supporting information), the ESR signals of PBS showed almost no change after irradiation with a 660 nm laser (0.5 W/cm², 5 min). Meanwhile, the ESR signal of In-TCPP bulk was only slightly enhanced by a 660 nm laser radiation compared to PBS, indicating that its production of ¹O₂ is very poor (Fig. 2h). Specifically, the ESR signal of In-TCPP nanosheets was significantly enhanced after only 1 min of laser irradiation. With the increase in laser irradiation time, the ESR signal strength also shows an increasing tendency (Fig. 2i), which is consistent with the results from the FL and UV spectrometer. These experimental results further indicated that the transformation of the morphology of In-TCPP MOF from bulk to nanosheets can significantly enhance its photo-trigger ¹O₂ yield, which is expected to be used as photosensitizer for efficient photodynamic antibacterial treatment.

  Based on the excellent ¹O₂ generation ability of the In-TCPP nanosheets, S. aureus (10⁷ CFU/mL) was selected as its photodynamic antimicrobial interface to evaluate its antimicrobial performance in vitro. The antimicrobial properties of In-TCPP nanosheets solutions at concentrations of 0 (PBS), 10, 30 and 50 µg/mL were investigated for testing, respectively. As shown in Fig. 3a, the number of bacteria in the In-TCPP solution at different concentrations was almost unchanged without the 660 nm laser (0.5 W/cm²) compared to the PBS control group, suggesting they had low dark toxicity. Observing the bacterial growth in the control group, it is clear that the bacteria survived well with increased laser time. This result suggests that exposure to a 660 nm laser alone is not sufficient to kill the bacteria. Surprisingly, adding low concentrations of In-TCPP resulted in significant bacterial killing in a short time. After 5 min of 660 nm laser irradiation, the bacterial survival rate in the 10 µg/mL In-TCPP group was 71.9%. It is noteworthy that the number of bacteria appeared to decrease dramatically, and their survival rate was only 27.3% when the laser duration was increased to 10 min. When the concentration of In-TCPP was increased to 30 µg/mL and 50 µg/mL, the bacteria on the agar plate had almost stopped growing. The bacterial inhibition reached 98.0% and 98.6% at only 5 min of light exposure, and the bacterial mortality rate after 10 min of light treatment had reached 100%, respectively (Fig. 3b). This is an indication that the ¹O₂ produced by In-TCPP is sufficient for effective sterilization in a short period of time.

  Figure 3

  

  Figure 3.  Antibacterial effects of In-TCPP nanosheets. (a) Photographs of S. aureus on agar plates treated with different concentrations (0–50 µg/mL) of In-TCPP nanosheets under a 660 nm laser (0.5 W/cm²) irradiation for different times. (b) The survival rate of S. aureus was calculated with plate count method. (c) Fluorescence staining images of S. aureus using SYTO9/PI after different treatments.

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  In order to visualize the survival of the S. aureus (10⁷ CFU/mL), bacterial structural integrity was assessed by live/dead fluorescent staining assays with PBS and In-TCPP (50 µg/mL). The bacterial suspensions treated with different conditions were stained using SYTO 9 and PI. It indicates that the antimicrobial properties of the In-TCPP nanosheets with synergistic photodynamic therapy have been substantially enhanced. As shown in Fig. 3c, a lot of green fluorescence and little red fluorescence was observed in the PBS, PBS + Laser (660 nm, 0.5 W/cm²), In-TCPP groups. There was a significant increase in the red fluorescence of the In-TCPP + Laser group, proving that In-TCPP + Laser effectively killed the S. aureus. The above results demonstrate that the antibacterial properties of In-TCPP on the S. aureus under a 660 nm laser irradiation were higher than those of the other groups.

  The S. aureus-infected mice were randomly separated into four treatment groups (PBS, PBS + Laser, In-TCPP, and In-TCPP + Laser) to evaluate the in vivo PDT performance of In-TCPP nanosheets. The study was approved by the First Affiliated Hospital of Henan University of Science and Technology. As shown in Fig. 4a, wound healing was recorded on days 0, 1, 3, 5 and 7 in mice treated with the four sets of conditions, respectively. After seven days of healing, all the PBS, PBS + Laser and In-TCPP groups showed poorer recovery and significant wound sepsis (Fig. 4a). In contrast, the wounds of mice treated with In-TCPP + Laser healed fastest owing to the substantially reduced wound area after treatment for 7 days. Subsequently, wound tissues from mice on the seventh day were selected for bacterial culture and counting to quantify the antimicrobial effect of the different groups. The In-TCPP + Laser group exhibited almost no bacterial growth on the nutrient agar plates, with a significantly lower number of bacterial than the PBS, PBS + Laser and In-TCPP groups. Additionally, after 7 days of repair, the relative wound area of mice in groups PBS, PBS + Laser, and In-TCPP decreased to 62.77% ± 3.48%, 50.75% ± 4.68% and 48.90% ± 4.29%, respectively (Fig. 4b). In contrast, the relative wound area of mice in In-TCPP + Laser group decreased significantly to only 2.20% ± 2.27%. At the same time, body weights were recorded daily for mice during the test period. As shown in Fig. 4c, each group of mice showed some increase in body weight after seven days, which further determined that the In-TCPP nanosheets had no drug toxicity.

  Figure 4

  

  Figure 4.  In vivo antibacterial performance of In-TCPP nanosheets. (a) The wound photographs of mice after various treatments at different treatment time, and the corresponding colony photographs of wound tissue after treating for 7 days. (b) The quantitative analysis of wound area under different treatments. (c) The changes in body weight of mice during treatment. (d) H&E, Masson and TNF-α staining of the bacteria infected tissues after different treatments.

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  To further validate the wound tissue and its morphological changes, we used histological staining methods to analyze wound sections taken from the mice on the seventh day (Fig. 4d). Inflammatory cell levels provide a visual response to wound healing, and the microscopic change can be clearly observed with hematoxylin and eosin (H&E) staining. A large number of inflammatory cells can be seen in the H&E staining of PBS, PBS + Laser and In-TCPP groups, indicating that they are heavily bacterially infected. In contrast, the number of inflammatory cells was significantly reduced in the In-TCPP + Laser group. In addition, the arrangement of collagen fibres in the wound tissue was assessed by Masson staining, in which collagen fibres appeared in blue and muscle fibres in red, and the more collagen fibres, the better the wound heals. The staining results proved that the blue collagen fibres in PBS, PBS + Laser, and In-TCPP were significantly less than those In-TCPP + Laser, suggesting that In-TCPP can effectively promote wound healing after PDT. To demonstrate the anti-infective properties of In-TCPP nanosheets with a 660 nm laser, we chose to analyze the level of inflammation in the wound through immunohistochemistry (TNF-α). It demonstrated that the positive cell area was significantly lower in the In-TCPP + Laser group than in the other three groups. To assess the in vivo biotoxicity of In-TCPP nanosheets, we performed H&E staining analysis of mouse organs (heart, liver, spleen, lung, and kidney). H&E staining of the mice's organs on day seven indicating that none of them showed inflammatory cells and lesions, suggesting that In-TCPP nanosheets do not have strong drug toxicity (Fig. S12 in Supporting information). These staining results were consistent with wound healing in mice, further confirming the efficient photodynamic antimicrobial properties of In-TCPP nanosheets.

  In summary, we have prepared 2D In-TCPP nanosheets by a simple solvent-mediated synthesis method and achieved control of the nanosheet morphology by adjusting the water/organic solvent ratio without the addition of any surfactants. It is worth noting that the transformation of In-TCPP from bulk to nanosheet with high yield was also achieved by using pyridine N group as a tool for growth restriction of In-TCPP nanosheets. Importantly, the ¹O₂ generation of 2D In-TCPP nanosheets is enhanced by over 2.3 times compared to the In-TCPP bulk, suggesting the photodynamic performance of 2D In-TCPP nanosheets has been significantly improved. The effect is mainly attributed to the fact that smaller nanosheets have more active sites. In vitro antimicrobial experiments showed that low concentrations of 2D In-TCPP nanosheets had a significant bactericidal effect immediately after irradiation by a 660 nm laser. At the same time, 2D In-TCPP nanosheets have highly effective antibacterial properties and promote wound healing in vivo, without any other side effects or toxicity. It has been demonstrated that morphologically optimized 2D In-TCPP nanosheets can be used as effective photosensitizers for PDT antimicrobial therapy and are expected to be further applied in anti-tumour therapy.

  CRediT authorship contribution statement

  Xiangrong Pan: Methodology, Measurement, Investigation, Verification, Writing – original draft Preparation. Xixi Hou: Analyze data, Writing – review & editing. Yuhang Du and Zhixin Pang: Analyze data, Measurement. Shiyang He: Analyze data, Validation. Lan Wang: Methodology, Formal analysis, Data curation. Jianxue Yang: Software, Resources. Longfei Mao: Conceptualization, Methodology, Resources, Verification. Jianhua Qin and Haixia Wu: Methodology, Formal analysis, Validation. Baozhong Liu: Formal analysis, Writing – review & editing. Zhan Zhou: Conceptualization, Verification, Writing – review & editing, Project administration. Lufang Ma: Supervision, Writing – review & editing, Project administration. Chaoliang Tan: Supervision, Conceptualization, Writing – review & editing, Project administration.

  Declaration of competing interest

  There are no conflicts of interest to declare.

  Acknowledgments

  This work is supported by the National Natural Science Foundation of China (Nos. 52102348, 22171123, and 22271130), the Science and Technology Innovation Talent Program of University in Henan Province (No. 23HASTIT016), the Natural Science Foundation of Henan Province (No. 242300420199), International Science and Technology Cooperation Project of Henan Province of China (No. 242102520016), and the Key Scientific Research Projects of Universities in Henan Province (No. 24A350006). C. Tan thanks the funding support from the National Natural Science Foundation of China-Excellent Young Scientists Fund (Hong Kong and Macau) (No. 52122002).

  Supplementary materials

  Supplementary material associated with this article can be found, in the online version, at doi:10.1016/j.cclet.2024.110536 .

  
  
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  Scheme 1  Schematic demonstration of the controlled synthesis of 2D In-TCPP nanosheets and their efficient photodynamic antibacterial.

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  Figure 1  (a, b) The SEM, (c) TEM, (d) HRTEM and (e) AFM height images of 2D In-TCPP nanosheets. (f) HAADF-STEM image and (g) its corresponding EDX element mapping images of 2D In-TCPP nanosheets.

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  Figure 2  (a) The N 1s and (b) In 3d XPS spectra of 2D In-TCPP nanosheets. (c) XRD patterns of 2D In-TCPP nanosheets. (d) The fluorescence spectra of SOSG treated with 2D In-TCPP (50 µg/mL) by irradiation using a 660 nm laser for different times (0–10 min) at 0.5 W/cm². (e) Fluorescence changes of SOSG at 532 nm treated with PBS, In-TCPP (50 µg/mL) bulk and nanosheets by irradiation using a 660 nm laser for different times. (f) The UV–vis spectra of ABDA solution (100 µmol/L) with the addition of 2D In-TCPP (50 µg/mL) under a 660 nm laser irradiation (0.5 W/cm²) for different times. (g) The UV–vis spectra change of ABDA at 380 nm treated with PBS, In-TCPP (50 µg/mL) bulk and nanosheets for different times. The ESR spectra of In-TCPP (h) bulk and (i) nanosheets under different illumination times in the presence of ¹O₂ scavenger (TEMP).

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  Figure 3  Antibacterial effects of In-TCPP nanosheets. (a) Photographs of S. aureus on agar plates treated with different concentrations (0–50 µg/mL) of In-TCPP nanosheets under a 660 nm laser (0.5 W/cm²) irradiation for different times. (b) The survival rate of S. aureus was calculated with plate count method. (c) Fluorescence staining images of S. aureus using SYTO9/PI after different treatments.

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  Figure 4  In vivo antibacterial performance of In-TCPP nanosheets. (a) The wound photographs of mice after various treatments at different treatment time, and the corresponding colony photographs of wound tissue after treating for 7 days. (b) The quantitative analysis of wound area under different treatments. (c) The changes in body weight of mice during treatment. (d) H&E, Masson and TNF-α staining of the bacteria infected tissues after different treatments.

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