CD44-Specific Targeting Nanoreactors with Glutathione Depletion for Magnifying Photodynamic Tumor Eradication

Abstract

Open AccessCCS ChemistryRESEARCH ARTICLE5 Aug 2022CD44-Specific Targeting Nanoreactors with Glutathione Depletion for Magnifying Photodynamic Tumor Eradication Chao Shi, Xiao Zhou, Qiancheng Zhao, Zhen Zhang, He Ma, Yang Lu, Zhibin Huang, Wen Sun, Jianjun Du, Jiangli Fan and Xiaojun Peng Chao Shi State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116024 , Xiao Zhou State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116024 , Qiancheng Zhao State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116024 , Zhen Zhang State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116024 , He Ma State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116024 , Yang Lu State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116024 , Zhibin Huang State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116024 , Wen Sun State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116024 State Key Laboratory of Fine Chemicals, Shenzhen Research Institute, Dalian University of Technology, Nanshan District, Shenzhen 518057 , Jianjun Du State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116024 State Key Laboratory of Fine Chemicals, Shenzhen Research Institute, Dalian University of Technology, Nanshan District, Shenzhen 518057 , Jiangli Fan State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116024 State Key Laboratory of Fine Chemicals, Shenzhen Research Institute, Dalian University of Technology, Nanshan District, Shenzhen 518057 and Xiaojun Peng *Corresponding author: E-mail Address: [email protected] State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116024 State Key Laboratory of Fine Chemicals, Shenzhen Research Institute, Dalian University of Technology, Nanshan District, Shenzhen 518057 https://doi.org/10.31635/ccschem.021.202101222 SectionsSupplemental MaterialAboutAbstractPDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareFacebookTwitterLinked InEmail Photodynamic therapy (PDT) is an efficacious noninvasive therapeutic modality that utilizes nontoxic photosensitizers (PSs) to transform oxygen into highly cytotoxic reactive oxygen species (ROS) under specific light irradiation. However, low intratumoral accumulation capacity and the reduced ROS production caused by excessive glutathione (GSH, a scavenger of ROS) in the tumor microenvironment (TME) immensely limit PDT therapeutic efficacy. Hence, an innovative nanoreactor [email protected] was constructed using DSPE-PEG2k-Maleimide and CD44-specific polypeptide (A6) modified liposome to encapsulate sulfur substituted Nile blue (NBS). NBS, as a near-infrared (NIR) PS, possesses not only a simple synthesis but also an extremely low IC50 (0.024 μM) compared with commercial Ce6 (5.16 μM) at a tiny light-dose irradiation of 6 J/cm2 in MCF7 cells. Encouragingly, [email protected] revealed significantly increased uptake and retention in breast cancer with CD44 overexpression. Furthermore, [email protected] can exhaust the intracellular GSH and upregulate ROS levels, causing explosive apoptosis to cancer cells. In brief, the abundant enrichment of nanomedicine and augmented ROS could amplify the PDT efficacy to achieve tumor ablation; the prepared nanoreactor possesses excellent biocompatibility and provides a novel clinical strategy. Download figure Download PowerPoint Introduction Photodynamic therapy (PDT) has been widely applied in cancer therapies due to its selective destruction, visual monitoring, mini-invasive surgical operation, and specific inhibitory efficacy on multidrug resistant tumors.1–6 Upon light irradiation at a specific wavelength, nontoxic photosensitizers (PSs) are excited to generate high-level reactive oxygen species (ROS) under oxygenated environments, resulting in irreversible oxidative damage to malignancies.7–12 Nevertheless, the antitumor efficiency of PDT is usually severely compromised by diminished ROS generation and nonspecific PSs accumulation.13–16 Glutathione (GSH) levels in tumor sites are 1000 times higher than in normal tissue; therefore, excessive GSH scavenging of cell-killing ROS during treatment results in failure of tumor therapy especially for PDT.17–20 Subsequently, numerous endeavors have been put forward to exhaust extra GSH by introducing substantial amounts of inorganic metal ions (Fe2+, Cu2+, Mn2+, etc.) to enhance therapeutic effects.21–24 However, the potential biotoxicity and tough metabolism capacity of inorganic nanoparticles have become major obstacles to their further applications in vivo. Consequently, designing a smart nanoreactor to deplete the overexpressed GSH in tumor for reducing PDT-generated ROS annihilation is crucial. Additionally, delivering the PSs precisely to the desired regions is particularly essential for ROS before its rapid decay and degradation. Currently, one main method for achieving this milestone is modifying ligands on the surface of the nanocarrier to heighten delivery capability to targeting sites and aggrandize the internalization of nanomedicine, which can amplify therapeutic efficiency and ultimately reinforce patient recovery.25–28 To date, several targeting ligands such as antibodies, peptides, and aptamers have been applied to enhance tumor therapy by increasing drug accumulation because of their high affinity for specific tumor tissues.29–31 Generally, traditional ligands have long chains or large sizes, which lead to expensive cost and complicated fabrication. Zhong and co-workers32 have exploited a CD44-specific A6 short peptide (KPSSPPEE), which possesses extraordinary targetability to CD44-overpressed orthotopic human multiple myeloma (MM) xenografts. As a glycoprotein in the transmembrane cell surface, CD44 is a low level endogenously expressed adhesion molecule in normal tissues; however, CD44 is overexpressed in various tumor cells such as breast, colon, stomach, pancreatic, and prostate cancers.33,34 Thus, the A6 short peptide is worthy of further exploration for the specific targeting ability on various cancers. Herein, the A6 short peptide (KPSSPPEE) was functionalized with DSPE-PEG2K-Maleimide (DSPE-PEG2k-Mal) to form A6-PEG2k-DSPE,35 which was initially applied to facilitate targeting ability in breast cancer. In addition, a near-infrared (NIR) PS, sulfur substituted Nile blue (NBS), was designed and synthesized, which possessed a straightforward synthetic route, caused localized tissue damage, and imparted relatively minimal adverse effects. As shown in Scheme 1, the smart nanoreactor ([email protected]) was fabricated by A6-PEG2k-DSPE, soybean phosphatidylcholine (SPC), cholesterol, DSPE-PEG2k-Maleimide, and NBS according to our previous preparation method.36 Subsequently, the maleimide on the surface of [email protected] interacted with GSH by Michael addition in the mild tumor microenvironment (TME) after entering the cell by endocytosis, which led to the GSH annihilation and increased ROS generation to facilitate PDT efficacy. Strikingly, [email protected] exhibited great stability, dispersibility, biocompatibility, and excellent biological safety according to the standard blood routine assays. Moreover, in vitro and in vivo experiments showed obvious GSH depletion and amplified ROS signal by the [email protected] reactivity with GSH. Furthermore, [email protected] exhibited powerful infiltration and retention in deep tumor tissue in the 4T1 tumor spheroids model and abundantly concentrated in the tumor site compared with [email protected] (no A6 targeting nanomedicine). In brief, an ingenious nanoreactor of [email protected] is reported, which significantly inhibits tumor growth at low light doses of 24 J/cm2 and achieves tumor eradication at 60 J/cm2 due to exhausting GSH and increasing drug concentrations at tumor sites. Our research provides a new strategy to amplify PDT in cancer and anticipates transforming clinical protocols. Scheme 1 | Illustration of the nanoreactor [email protected] for enhanced PDT tumor therapeutic strategy. Download figure Download PowerPoint Experimental Methods Synthesis of NBS As shown in Supporting Information Scheme S1, compounds 1 (298 mg, 1 mmol) and 2 (308 mg, 1.8 mmol) were stirred in methanol (MeOH, 25 mL) refluxed at 70 °C. Afterward, AgCO3 (606 mg, 2.2 mmol) was added slowly to the refluxed reaction. The reaction was heated for another 30 min until it turned dark blue, and then it was cooled to room temperature. Solvent was removed under reduced pressure distillation to produce the dark blue crude product. The crude product was dissolved in 25 mL dichloromethane (DCM) and extracted (3 × 100) with saturated aqueous NaCO3. The combined organic extracts were dried over anhydrous Na2SO4, filtered, acidified with concentrated HCl (0.4 mL) and concentrated. The acquired product was purified by silica gel column chromatography with MeOH and DCM to obtain targeted compound, NBS (Yield: 55.6%). Electrospray ionization high-resolution mass spectrometry (ESI-HRMS): m/z calcd for [M − Cl−]+, 362.1685; found, 362.1691. 1H NMR [500 MHz, dimethyl sulfoxide (DMSO), δ]: 10.03 (s, 1H), 9.00 (d, J = 8.1 Hz, 1H), 8.60 (d, J = 8.2 Hz, 1H), 8.01 (d, J = 9.3 Hz, 1H), 7.95 (t, J = 7.5 Hz, 1H), 7.91–7.84 (m, 1H), 7.57 (s, 1H), 7.49–7.33 (m, 2H), 3.76 (dt, J = 12.9, 6.3 Hz, 2H), 3.67 (q, J = 6.9 Hz, 4H), 1.37 (t, J = 7.2 Hz, 3H), 1.24 (t, J = 7.1 Hz, 6H). 13C NMR (126 MHz, DMSO, δ): 152.87, 150.82, 139.85, 136.84, 133.65, 133.24, 132.07, 131.28, 131.25, 129.55, 124.72, 124.17, 123.37, 117.35, 105.40, 102.99, 48.56, 45.08, 13.99, 12.62. Synthesis of A6-PEG2k-DSPE A6 peptide (Ac-KPSSPPEEC-NH2, 30 mg, 30 μmol, 1.5 equiv) was added to a solution of DSPE-PEG2k-Mal (40 mg, 20 μmol, 1 equiv) in a mixture of MeOH (15 mL) and DCM (15 mL) under N2 atmosphere, and the reaction proceeded at 37 °C for 24 h under constant stirring. DSPE-PEG2k-A6 was isolated by precipitation three times in cold anhydrous diethyl ether, and the white precipitate was obtained by centrifugation (3500 rpm, 5 min) in a frozen centrifuge at 4 °C. The final product was dried under vacuum for 24 h at 37 °C. As shown in Supporting Information Figure S6, the molecular weights of DSPE-PEG2k-Mal are 2849.9 and 2893.9, and the corresponding molecular weights of A6-PEG2k-DSPE are 3863.9 and 3907.9. The mass spectrometric results showed that A6-PEG2k-DSPE was successfully prepared. Preparation of [email protected] [email protected] was prepared per the method in our previous study. Briefly, SPC (80 mg), cholesterol (10 mg), DSPE-PEG2k-A6 (10 mg), DSPE-PEG2k-Mal (10 mg), and NBS (1 mg) at the molar ratio of 76:18:2:2:2 was absolutely dissolved in 20 mL chloroform (CHCl3), and then the solvent was removed by reduced pressure distillation. Later, the dried mixture was placed into a vacuum-drying oven, desiccated overnight at 35 °C, and was re-distributed in 20 mL phosphate-buffered saline (PBS; pH 7.4). After multigelation five times in the −80 °C refrigerator, the obtained solution was then circulated under a high-pressure homogenizer 30 times and quickly percolated with 400 and 220 nm polycarbonate filter 10 times separately using an extruder a in water bath at 35 °C. Finally, the final product was stored at 4 °C. In vivo GSH assays All animal studies involved in this work were performed in compliance with the Guidelines for the Care and Use of Laboratory Animals, published by the National Institutes of Health. The animal protocol was approved by the local research ethics review board of the Animal Ethics Committee of Dalian University of Technology (Certificate number//Ethics approval no. is 2020-048). The 4T1-bearing mice were treated with PBS, empty liposome, [email protected], [email protected], and [email protected] (three times per group). Tumors were isolated from mice 40 min after injection. The tumor tissue was frozen in liquid nitrogen and then ground into a powder. Powder (10 mg) was removed from each group and added to 30 μL protein removal reagent M, and then fully vortex. An additional 70 μL of protein removal reagent M was added and fully homogenized with a glass homogenizer. The obtained sample tubes were put at 4 °C for 10 min and centrifuged at 4 °C by 10,000 × g for 10 min. The supernatant was used for the determination of GSH per the GSH and oxidized GSH (GSSG) assay kit. Other routine experimental procedures, materials, instruments, characterization methods, additional data, and supplementary figures are outlined in the Supporting Information. Results and Discussion Synthesis of NBS and A6-PEG2k-DSPE To obtain a high-efficiency PS, NBS was synthesized by a simple and high-yield synthetic process ( Supporting Information Scheme S1). The structures of all the compounds were accurately characterized by 1H NMR, 13C NMR, and ESI-HRMS ( Supporting Information Figures S1–S5). In addition, A6-PEG2k-DSPE was acquired by reacting DSPE-PEG2k-Maleimide with A6 short peptide (KPSSPPEE), which was observed by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOFMS) ( Supporting Information Figure S6). Preparation and characterization of [email protected] The smart nanoreactor [email protected] was prepared by thin-film dispersion–homogenization–extrusion. The morphology and properties of [email protected] were characterized with a series of techniques. As shown in Figure 1a, transmission electron microscopy (TEM) showed that the average diameter of [email protected] was approximately 60 nm and displayed spherical structure and uniform particle size distribution. Homogeneously, the mean size of empty liposome, [email protected], [email protected], and [email protected] mainly distributed at approximately 60–80 nm, showing a normal and unimodal distribution in deionized water from dynamic light scattering (DLS) (Figure 1b). In addition, DLS also revealed the zeta potential of [email protected] was −45.5 mV ( Supporting Information Figure S7), illustrating that the prepared nanoparticles possessed excellent stability. To calculate the loading rate of [email protected], the absorption spectra of NBS were measured by UV–vis spectrometer in MeOH at different known concentrations ( Supporting Information Figure S8a), and their linear relationship between concentration and maximum absorbance was fitted by Origin ( Supporting Information Figure S8b). After optimization, the encapsulation efficiency of [email protected] loading NBS was approximately 69.2% ± 1.8%. Furthermore, to further validate the storage stability of the nanomedicine, we detected the variation of polydispersity index (PDI), average size, zeta potential, and loading capacity of the prepared nanoparticles over time at 4 °C. As depicted in Supporting Information Table S1, the average size exhibited no significant increase and maintained a diameter of 100 ± 50 nm over 30 days, and the PDI was below 0.23. The zeta potential showed negligible change and retained the range of −20 to −50 over 30 days. The entrapment efficacy exhibited negligible variation, indicating that the prepared nanoparticles could steadily disperse in PBS at 4 °C and had great stability over 30 days. Figure 1 | (a) TEM image and (b) DLS measurement of empty liposome, [email protected], [email protected], and [email protected] nanoparticles. (c) The UV–vis absorbance (solid line) and fluorescence spectra (dash line) of free NBS in various solvents. (d) EPR signals produced by [email protected] in light using TEMP and DMPO for detecting 1O2 and O2−•, separately. (e) Attenuated absorbance of DPBF at 415 nm and (f) amplified fluorescence value of DHR123 at 525 nm for testing 1O2 and O2−• under 660 nm irradiation with different laser densities (1.5, 2.0, and 2.5 mW/cm2) in MeOH, respectively. (g) The relative GSH level with an increasing molar ratio of DSPE-PEG2k-Mal/GSH in PBS (n = 3). The concentration of GSH after receiving different treatments in (h) 10 mg MCF7 cells or (i) 10 mg tumor of 4T1-bearing balb/c mice. Download figure Download PowerPoint Light-triggered ROS generation We tested the absorption and emission spectra of free NBS in various solvents and found a maximum emission value of approximately 700 nm under excitation by light at 650 nm of the maximum absorbance value (Figure 1c). To determine the type of ROS, electron paramagnetic resonance (EPR) spectroscopy was initially carried out. As shown in Figure 1d, the obvious superoxide anion (O2−•) and singlet oxygen (1O2) signals were captured by using 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) and 2,2,6,6-tetramethylpiperidine (TEMP) as the spin-trapping agent, respectively. To further clarify this result, we utilized 1,3-diphenylisobenzofuran (DPBF) and dihydrorhodamine 123 (DHR123) as radical scavenger for checking 1O2 and O2−•, separately. As depicted in Figure 1e, a steady decrease in absorption of DPBF at 415 nm was observed after irradiating for 0 to 5 min, and at higher light doses, the rate of decline was greater. Likewise, a rectilinear rise in fluorescence intensity of DHR123 at 525 nm was observed after being irradiated for 0 to 3 min. The rising trend is steeper as the laser densities increase (Figure 1f). Thus, NBS could simultaneously generate 1O2 and O2−• for achieving PDT under irradiation at 660 nm. DSPE-PEG2k-Mal-mediated GSH depletion It was reported that maleimide can exclusively react with functional thiols of GSH through Michael addition an in vivo TME.37,38 Herein, DSPE-PEG2k-Mal was used as a liposome structure to reduce the ROS annihilation caused by GSH and to decrease phagocytosis by macrophages due to its stealthy structure. As displayed in Figure 1g, the GSH level decreased as the molar ratio of Mal-PEG2k-DSPE/GSH increased, which was measured by Ellman's assay. Similarly, significant decrease of GSH was detected after treating 10 mg MCF7 cells (Figure 1h) or 10 mg tumor of 4T1-bearing balb/c mice (Figure 1i) with [email protected] and [email protected] including Mal-PEG2k-DSPE. In contrast, no obvious change of GSH level compared with control group was observed after treatment of cells with empty liposome and [email protected] not containing Mal-PEG2k-DSPE. Overall, liposomes doped with Mal-PEG2k-DSPE downregulated GSH levels, which provides a new opportunity to regulate TME for enhancing PDT. In vitro cellular uptake behavior assays The cellular uptake and distribution of [email protected] were evaluated in MCF7 cells. The fluorescence intensity reached the maximum after being cultured with [email protected] for approximately 50 min, which provided a reference in the incubation time for subsequent cell experiments ( Supporting Information Figure S9). To explore the subcellular organelle localization after being internalized, [email protected] was incubated with Lyso-Tracker Green (a commercial lysosome tracker) or Mito-Tracker Green (a commercial mitochondrial tracker) in MCF7 cells, respectively (Figure 2a). Obviously, a strong superposition signal of [email protected]NBS and Lyso-Tracker Green was observed upon a colocalization study (Pearson's contrast, a colocalization fluorescence signal was acquired between the Mito-Tracker Green and fluorescence (Pearson's The results showed that [email protected] can and PDT in Figure 2 | (a) colocalization of [email protected] and Mito-Tracker Green or Lyso-Tracker Green cultured in MCF7 cells. the of nanoparticles and commercial nm, nm [email nm, nm Lyso-Tracker Green or Mito-Tracker 10 (b) The fluorescence signal and its ratio of [email protected] and [email protected] in MCF7 cells. nm, nm, 20 (c) of [email protected] and [email protected] into the 4T1 after approximately 1.5 (d) oxygen and superoxide anion of control light [email protected], [email protected] [email protected] and [email protected] after ROS using and fluorescence in MCF7 cells, respectively. nm, 20 Download figure Download PowerPoint ROS generation and specific targeting of [email protected] NBS produced 1O2 and O2−• under irradiation in Figures and To [email protected] could generate O2−• and 1O2 in cells, MCF7 cells were incubated with and separately. As depicted in Figure significant fluorescence signal was detected compared with light irradiation or [email protected] in dark and [email protected] containing DSPE-PEG2k-Mal exhibited a fluorescence signal than [email protected] under irradiation. that [email protected] can amplify 1O2 and O2−• production due to a of ROS, To further that increased ROS generation of the prepared nanoparticles under irradiation due to GSH intracellular thiols were initially by As significant of 1O2 and O2−• fluorescence signal was observed after being by compared with indicating [email protected] could amplify ROS generation for achieving enhanced PDT. revealed significantly higher drug fluorescence of [email protected] than [email protected] after incubation for 50 min, illustrating that [email protected] in cells due to the targeting of A6 (Figure To further the capacity of [email protected], tumor spheroids were constructed by 4T1 cells. As displayed in Figure [email protected] could only on the surface of the tumor [email protected] the of the tumor We that the A6 on the nanoreactor surface their and In vitro The standard cell assay was applied to the PDT therapeutic efficiency of [email protected] in MCF7 and 4T1 cells. To the of NBS, we used commercial Ce6 as a at the light and incubation time in different cancer cells. the IC50 value of Ce6 was times than that of NBS in MCF7 cells with the light of 6 J/cm2 (Figure a of the IC50 was obtained between Ce6 and NBS in 4T1 cells (Figure by this result, the cell rate in the of prepared nanoparticles was by standard assay. As exhibited in Figures and the empty liposome under [email protected], and [email protected] in dark exhibited negligible in 4T1 and MCF7 cells. In contrast, obvious of [email protected] was [email protected] and [email protected] showed cell damage under irradiation because of targeting ability and GSH respectively. [email protected] possessed the IC50 value compared with the illustrating that it could amplify the tumor therapy efficiency of PDT due to high intracellular enrichment of nanomedicine and ROS level in the Nevertheless, the [email protected] and [email protected] exhibited negligible in normal cells with low intracellular GSH which further that [email protected] PDT therapeutic efficiency by overexpressed intracellular GSH in tumor cells ( Supporting Information Figure To further the obtained result, fluorescence of and was used to cell strong fluorescence after being by in cells, the cell into the to generate As shown in Figure the group of control with and irradiation and [email protected] in dark exhibited negligible in MCF7 [email protected] possessed extremely compared with [email protected] or [email protected] under irradiation It was that [email protected] could the PDT treatment efficiency because of large intracellular drug concentration and explosive ROS Figure 3 | The cell of (a) free NBS and (b) free Ce6 with various concentrations in MCF7 cells and 4T1 cells by 660 nm light intensity of 6 The cell of empty liposome light [email protected] [email protected] [email protected] [email protected] [email protected] and [email protected] with different concentrations in (c) MCF7 cells and (d) 4T1 cells under 660 nm irradiation (e) signal of MCF7 cells incubated with and after being treated with nanoparticles with or light irradiation nm, 6 nm, nm nm, nm 100 Download figure Download PowerPoint In vivo and PDT We observed the in vivo of [email protected] and [email protected] by of 4T1-bearing balb/c mice. As displayed in Figures and significant signals were at the tumor and the maximum concentration was 40 min after injection. [email protected] showed fluorescence signal than [email protected], indicating that [email protected] possessed targeting of the CD44 overexpressed 4T1 were and at 40 min, that [email protected] in and in and and that [email protected] possesses affinity for CD44 and We that the was the major for the accumulation of nanoparticles in the which provides a strategy for treatment of the excellent targeting ability of [email protected] tumor sites in we tested the therapeutic efficiency on tumor with 4T1 cells. with of were into (three mice per and separately various treatment at the drug concentration 60 as PBS, empty liposome light [email protected], [email protected] light [email protected] light [email protected] light [email protected] light and [email protected] light All of mice one treatment at 40 min after injection. As depicted in Figure no variation in of mice was observed in all after indicating that nanoparticles possessed negligible to mice. the tumor growth control containing PBS, empty liposome under and [email protected] exhibited negligible inhibitory on tumor As [email protected] and [email protected] possessed than [email protected], indicating that high drug retention in tumor and GSH annihilation could amplify tumor [email protected] displayed efficiency and achieve

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