Zinc-metal–natural frameworks with tunable UV diffuse-reflectance as sunscreens | Journal of Nanobiotechnology

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Supplies and animals

Zinc oxide (ZnO, ≥ 99.9%), titanium oxide (TiO2, ≥ 99.9%), zinc acetate dihydrate (Zn(Ac)2·2H2O, ≥ 99.9%), terephthalic acid (H2BDC, 99%), N,N-dimethylformamide (DMF, 99.8%) and 2-methylimidazole (2-MeIM) have been obtained from J&Ok Chemical substances (Beijing, China). Dimethyl sulfoxide-d6 (DMSO-d6, ≥ 99.9%) have been bought from Tian in Fuyu Tremendous Chemical Co., Ltd (Tianjin, China). 4,4’-stilbenedicarboxylic acid (LH2) was purchased from Flurochem (UK). Dulbecco’s modified eagle medium (DMEM), minimal important medium (MEM) and fetal bovine serum (FBS) have been bought from Thermo Fisher Scientific (Waltham, MA, USA). Thiazolyl blue (MTT) was purchased from Biosharp (Hefei, China). IL-1β polyclonal antibody was obtained from Signalway Antibody LLC (Faculty Park, USA). Phospho-histone H2AX (Ser139) antibody (γ-H2AX) was purchased from Affinity Biosciences (Cincinnati, USA). Anti-thymine dimer antibody (cyclobutane pyrimidine dimers, CPDs) was obtained from Sigma-Aldrich (Louis, USA). Masson’s trichrome staining equipment was bought from Beijing Solarbio Science & Expertise (Beijing, China). Annexin V-FITC/PI apoptosis detection equipment was purchased from Procell Life Science & Expertise (Wuhan, China). 2,7-Dichlorofluorescein Diacetate (DCFH-DA) probe equipment and DNA injury assay equipment have been obtained from Nanjing Jiancheng Bioengineering Institute (Nanjing, China). UVB mild with a peak emission at 308 nm was purchased from Sankyo Denki Co. (Tokyo, Japan).

Human immortalized epidermal keratinocytes (HaCaTs) have been bought from China Heart for Sort Tradition Assortment (CCTCC, Wuhan, China) and cultured in DMEM with 10% FBS and 1% antibiotics. Human epithelial keratinocytes (HEKas) have been obtained from Jennio Biotech (Guangzhou, China) and reserved in MEM medium with 10% FBS and 1% antibiotics. Each cells have been positioned in a humidified incubator with 5% CO2 at 37 °C.

Male BALB/c mice (6 weeks) have been obtained from Laboratory Animal Centre of Guangzhou College of Chinese language Medication. Male Ba-Ma miniature pig (2–3 months) was purchased from Dongguan Songshan Lake Laboratory Animal Expertise Co., Ltd (Guangdong, China). All of the protocols for animal experiments have been accredited by the Animal Ethics Committee of Southern Medical College, China. (Approval variety of the laboratory: L2018244).

Devices and methodologies

Powder X-ray diffraction (PXRD) was carried out on Bruker D8 advance (Bruker Company, Billerica, USA) on the velocity of 10° min−1 with an angle vary of 5°–60°. 1H NMR spectra have been recorded on 400 MHz Bruker (Bruker Company, Billerica, USA). Fourier rework infrared (FT-IR) spectra from KBr pellets have been carried out utilizing a Nicolet iS10 spectrometer (Thermo, Waltham, MA, USA). Elemental evaluation was carried out on an Elementar Vario-EL Dice CHNS elemental analyzer (Vario EL dice, Hanau, Germany). Transmission electron microscope (TEM) imaging was acquired on Hitachi H-7650 microscope (80 kV, Hitachi, Tokyo, Japan). N2 isotherm measurements have been carried out on ASAP 2460 (Micromeritics instrument Ltd., GA, Norcross, USA) at 77 Ok with 20–100 mg of pattern per measurement. Inductively coupled plasma mass spectrometry (ICP-MS) was carried out on Agilent 7700 (Agilent Applied sciences, Inc., Santa Clara, USA). X-ray photoelectron spectroscopy (XPS) have been measured utilizing Ok-Alpha (Thermo Scientific, Waltham, MA, USA). Thermogravimetric evaluation (TGA) was acquired on TGA 5500 from 30 to 780 °C at a velocity of 5 °C min−1 (TA Devices, New Fortress, USA). UV–seen diffuse-reflectance spectrum have been carried out from BaSO4 pellets on Lambda 950 (PerkinElmer Inc., Waltham, USA) geared up with photometric integrating sphere (150 mm Int. sphere). The zeta potentials of Zn-based MOFs have been measured utilizing Zetasizer Nano ZS (Malvern Panalytical, UK). To measure electron paramagnetic resonance (EPR), TiO2, ZnO, or ZIF-8 (2 mL, 800 μg mL−1) have been blended with free radical catcher α-(4-Pyridyl N-oxide)-N-tert-butylnitrone (POBN, 38.8 mg), irradiated with UV (200–400 nm) for 10 min at 25 ± 0.1 °C below customary atmospheric strain, and analyzed utilizing a A300 spectrometer (Bruker Company, Billerica, USA). The samples at 800 μg mL−1 however not 50 μg mL−1, have been chosen for EPR measurement, as a result of ROS sign was too low to be detected at 50 μg mL−1, although ZIF-8 and TiO2 might shield pores and skin cells towards UV injury at 50 μg mL−1. (Extra file 1: Fig. S14).

The synthesis and characterization of MOFs

ZIF-8: ZIF-8 with varied sizes have been synthesized in line with beforehand reported strategies with minor modifications [45, 46]. Briefly, Zn(Ac)2·2H2O (2.28 × 10–1 mol L−1 in DMF, 2 mL) have been added with varied ratios of Zn2+ to 2-MeIM (4 mL of DMF, 2.28 × 10–1 mol L−1 for ZIF-8 1:2, 5.71 × 10–1 mol L−1 for ZIF-8 1:5, 9.14 × 10–1 mol L−1 for ZIF-8 1:8, 18.28 × 10–1 mol L−1 for ZIF-8 1:16) below stirring at 450 rpm to synthesize ZIF-8 with completely different sizes. After 7.5 h, the response answer was centrifuged at 8000 rpm for two min and washed with DMF (5 mL) and ethanol (5 mL) for two instances, respectively. The samples have been resuspended with ethanol and saved at – 80 °C for additional use.

TEM, 1H NMR, PXRD, XPS, and N2 isotherm have been carried out to verify the construction of ZIF-8.

ZIF-8 1:2: 1H NMR (DMSO-d6/D2SO4 (9:1, v/v)): 7.49 (s, 2H, Imidazole H), 2.60 (s, 3H, –CH3). Yield: 29.7%. BET floor space was 1237.8 m2 g−1. Pore measurement: 9.3–15.0 Å. XPS information additionally revealed the profitable synthesis of ZIF-8 1:2 (Extra file 1: Fig. S3).

ZIF-8 1:5: 1H NMR (DMSO-d6/D2SO4 (9:1, v/v)): 7.49 (s, 2H, Imidazole H), 2.56 (s, 3H, –CH3). Yield: 19.1%. BET floor space was 1306.9 m2 g−1. Pore measurement: 9.3–15.0 Å. XPS information additionally revealed the profitable synthesis of ZIF-8 1:5 (Extra file 1: Fig. S4).

ZIF-8 1:8: 1H NMR (DMSO-d6/D2SO4 (9:1, v/v)): 7.38 (s, 2H, Imidazole H), 2.48 (s, 3H, –CH3). Yield: 19.0%. BET floor space was 1566.8 m2 g−1, which was just like the reported values, doubtlessly as a result of excessive crystallinity and the superb activation earlier than N2 isotherm measurement. [47, 48] Pore measurement: 9.3–16.0 Å. XPS information additionally revealed the profitable synthesis of ZIF-8 1:8 (Extra file 1: Fig. S5).

ZIF-8 1:16: 1H NMR (DMSO-d6/D2SO4 (9:1, v/v)): 7.49 (s, 2H, Imidazole H), 2.50 (s, 3H, –CH3). Yield: 15.7%. BET floor space was 1267.4 m2 g−1. Pore measurement: 9.3–15.9 Å. XPS information additionally revealed the profitable synthesis of ZIF-8 1:16 (Extra file 1: Fig. S6).

ZIF-8 was noticed utilizing TEM and the particle sizes have been plotted thereafter. The particle measurement have been 164.8 ± 32.6 nm, 102.5 ± 26.8 nm, 82.3 ± 24.5 nm, and 80.0 ± 37.7 nm for ZIF-8 1:2, ZIF-8 1:5, ZIF-8 1:8, ZIF-8 1:16, respectively, confirming the dimensions was decreased with the ratios of Zn2+ to 2-MeIM reducing (Fig. 1A, Extra file 1: Figs. S1, S7A, B). These have been just like the earlier report that ZIF-8 sizes have been decreased from 110 to 40 nm with the ratios of Zn2+ to 2-MeIM reducing from 1:2 to 1:16 [46]. Nonetheless, no apparent ZIF-8 morphology variations have been noticed, (Fig. 1A, S7A) which weren’t in step with the studies that morphologies of ZIF-8 turned from dice to sphere with the ratios of Zn2+ to 2-MeIM reducing [46]. Probably as a result of decline of particle sizes, UV reflectance, particularly for UVB and UVC, was enhanced with the lower of Zn2+ to 2-MeIM ratios, which reached to the best worth for ZIF-8 1:8. No additional enhancement was noticed for ZIF-8 1:16, (Extra file 1: Fig. S7C) probably as a result of measurement of ZIF-8 1:16 was just like that of ZIF-8 1:8. So ZIF-8 1:8 was chosen as mannequin ZIF-8 within the following experiments.

To check the power launch methods of ZIF-8 after UV publicity, TiO2, ZnO, or ZIF-8 (150 mg mL−1 in glycerol, 1 mL) have been irradiated with UVB on the dose of 6.408 × 104 J m−2, thermal photographs have been then taken by FLIR C2 Compact Thermal Digicam (FLIR Programs, Wilsonville, USA). After irradiation, the fluorescence depth of TiO2, ZnO, and ZIF-8 (50 μg mL−1 in ethanol) have been obtained by F97 professional fluorescence spectrophotometer (Lengguang Tech., Shanghai, China) with excitation wavelength at 308 nm.

TEM, PXRD, XPS additionally have been used to verify the buildings of TiO2 and ZnO (Fig. 1A, Extra file 1: Figs. S8, S9).

MOF-5: MOF-5 was synthesized as beforehand reported [49]. Zn(NO3)2·6H2O (290 mg, 1 mmol) was added into H2BDC (5.0 × 10–2 mol L−1 in DMF, 10 mL) and heated at 120 °C for 21 h. The response answer was centrifuged at 8000 rpm for two min and washed with DMF (5 mL) for 3 instances. The pattern was saved in ethanol at − 80 °C for additional use. 1H NMR (DMSO-d6/D2SO4 (9:1, v/v)): 8.07 (s, 4H, Ar H). Yield: 14.2%. BET floor space: 741.5 m2 g−1. Pore measurement: 6.5—15.0 Å. XPS information confirmed the profitable synthesis of MOF-5 (Extra file 1: Figs. S10, S13).

IRMOF-1: IRMOF-1 was synthesized in line with beforehand reported technique [50, 51]. Briefly, Zn(NO3)2·6H2O (10 mg, 0.034 mmol) was added into H2BDC answer (2.7 × 10–2 mol L−1 in DMF, 10 mL), and heated at 100 °C for 18 h. The crystals have been centrifuged at 8000 rpm for two min and washed with DMF (5 mL) and ethanol (5 mL) for 3 instances, respectively. The pattern was saved in ethanol at − 80 °C for additional use. 1H NMR (DMSO-d6/D2SO4 (9:1, v/v)): 8.07 (s, 4H, Ar H). Yield: 55.2%. BET floor space: 799.2 m2 g−1. Pore measurement: 6.0–25.0 Å. XPS information additionally revealed the profitable synthesis of IRMOF-1 (Extra file 1: Figs. S11, S13).

Zn3L3(DMF)2: Zn3L3(DMF)2 was synthesized following beforehand reported strategies [12]. Zn(NO3)2·6H2O (209.2 mg, 0.7 mmol) was added to LH2 (9.14 × 10–1 mol L−1 in DMF, 20 mL), heated at 75 °C for 16 h and adopted by heating at 85 °C for 4 h. Thereafter, the samples have been centrifuged at 8000 rpm for two min and the precipitate was washed with DMF (5 mL) and ethanol (5 mL) for 3 instances, respectively. The pattern was saved in ethanol at − 80 °C for additional use. 1H NMR (DMSO-d6/D2SO4 (9:1, v/v)): 7.94 (s, 2H, Ar H), 7.82 (s, 2H, Ar H), 7.49 (s, 2H, C=CH), 2.93 (S, –CH3, 3H), 2.77 (S, 3H, –CH3). Yield: 12.8%. BET floor space: 910.1 m2 g−1. Pore measurement: 6.4–11.8 Å. XPS information additionally revealed the profitable synthesis of Zn3L3(DMF)2 (Extra file 1: Fig. S12, 13).

The degradations of MOFs: The degradation of Zn-based MOFs in synthetic sweat was assessed as beforehand reported. Briefly, ZIF-8 1:8 (10 mg, 0.5 mg), MOF-5 (0.5 mg), IRMOF-1 (0.5 mg), and Zn3L3(DMF)2 (0.5 mg) dispersed in glycerol have been sealed into dialysis tubes, adopted by an incubation in synthetic sweat (0.5% NaCl, 0.1% lactic acid, and 0.1% urea, pH = 6.5, 32 °C ) at 100 rpm. On the predetermined time intervals, synthetic sweat samples have been collected and renewed with contemporary media. The MOF ligands in synthetic samples have been measured with NanoPhotometer (NP80 Contact, IMPLEN, Germany). ZIF-8 (10 mg) confirmed the bottom degradation charge (36.2 ± 0.5% of degradation inside 24 h), adopted by ZIF-8 (0.5 mg) (46.6 ± 6.2% in 4 h, 72.0 ± 8.3% in 24 h), Zn3L3DMF2 (0.5 mg) (46.8 ± 6.8% in 4 h, 80.7 ± 9.2% in 24 h), MOF-5 (0.5 mg) (78.3 ± 5.0% in 4 h), and IRMOF-1 (0.5 mg) (86.8 ± 5.9% in 4 h) (Fig. 1E, Extra file 1: Fig. S13H).

In vitro SPF measurement: TiO2, ZnO, and ZIF-8 have been dispersed in ethanol (15% by weight), respectively, and handled with ultrasonication for 10 min. The absorption at 290–320 nm was assessed utilizing NanoDrop 1000 UV–VIS spectrophotometer (Extra file 1: Fig. S16). SPF values have been calculated in line with Mansur Eq. (3) beneath [22]:

$${SPF}_{mathrm{spectrophotometric}}=mathrm{CF} instances sum_{290}^{320}mathrm{EE }left(uplambda proper)instances mathrm{I }left(uplambda proper)instances mathrm{Abs }left(uplambda proper)$$

(3)

the place CF = correction issue (10), EE (λ) = erythemal impact attributable to the radiation with λ wavelength, I (λ) = photo voltaic depth with λ wavelength, Abs (λ) = absorbance of samples. EE × I are constants as beforehand reported [23].

In vitro cytotoxicity assay HaCaTs or HEKas have been seeded (2 × 104 cells per effectively) into 96-well plates and incubated for twenty-four h. Thereafter, the cells have been handled with saline or varied concentrations (1—100 μg mL−1) of TiO2, ZnO, or ZIF-8 for twenty-four h after which incubated with MTT answer (0.5 mg mL−1) at 37 °C for 4 h. Lastly, DMSO (200 μL) was added to dissolve the resulted crystal and the absorbance at 570 nm have been measured utilizing a microplate reader (Multiskan FC, Thermo Scientific, Waltham, MA USA). Cell viability was expressed as a proportion of the absorbance to that of the management experiment with out therapy.

Cell apoptosis assay Cells have been seeded into 12-well plates (3 × 105 cells per effectively) and incubated for twenty-four h. After handled with TiO2, ZnO, or ZIF-8 (60 μg mL−1) (HaCaTs for 12 h and HEKas for 8 h), cells have been photographed utilizing a microscope with white mild. Thereafter, cells have been harvested, fastened with 4% paraformaldehyde at 4 °C for 30 min, permeabilized in 1% Triton-X 100 for one more 30 min, after which stained with DAPI for 20 min. The stained cells have been examined utilizing fluorescence microscope (DMI8, Leica, Germany).

Cell apoptosis additionally was assessed utilizing movement cytometry. Cells have been grown in 6-well plates at a density of 1 × 106 cells per effectively and incubated to finish adhesion. Then, the cells have been handled with TiO2, ZnO or ZIF-8 (60 μg mL−1, HaCaTs for 12 h and HEKas for 8 h). Thereafter, the cells have been indifferent with trypsin, centrifuged at 300 g for five min, stained with Annexin V-FITC and propidium iodide (PI) for 20 min, and analyzed by movement cytometer (CytoFLEX LX, Beckman Coulter Biotechnology Co., California, USA).

Safety towards UV-induced cell demise The cell viability of HaCaTs or HEKas after publicity with varied UV doses for twenty-four h was first assessed by MTT assay. Round 50% cell development inhibition was achieved at UV doses of 35 mJ cm−2 for HaCaTs and 75.6 mJ cm−2 for HEKas (Extra file 1: Fig. S17). Additionally, the optimized UV doses are just like the beforehand reported UVB irradiation doses (30 or 50 mJ cm−2) for cells [52, 53]. Thus, the 2 UV doses have been used within the following safety experiments. HaCaTs or HEKas (30 μL of medium per effectively) in 96-well plates have been handled with TiO2, ZnO or ZIF-8 at concentrations of fifty μg mL−1 or 60 μg mL−1 for 15 min, irradiated with UV lamp (emission peak 308 nm, Sankyo Denki Co., Taiwan, China) on the optimized doses, washed with PBS to take away the nanoparticles and incubated in contemporary full medium for one more 24 h. The cell viability was then assessed utilizing MTT assay.

Safety towards DNA injury attributable to UV irradiation Comet assay was used to find out the photoprotective impact of ZIF-8 to HaCaTs or HEKas. To optimize UV doses, cells have been seeded into 12-well plates (5 × 105 cells per effectively) and incubated for twenty-four h. Thereafter, cells have been uncovered to 4 UV doses (84, 98, 114 or 126 mJ cm−2 for HaCaTs and 38.5, 52.5, 66.5 or 84 mJ cm−2 for HEKas) and incubated with 1 mL of full medium for one more 2 h. Cells have been collected, blended with 0.7% low melting level agarose. The cell suspensions (40 μL) have been added onto slides with 1% regular melting level agarose. The slides have been soaked in lysis buffer (4 °C ) for 1 h, gently washed with PBS, immersed in electrophoresis buffer for 18 min to permit DNA denaturation, and subjected to electrophoresis for 30 min (25 V, 200 mA, Horizontal electrophoresis system, DYY-6C, Beijing Six-one Instrument plant, Beijing, China). Subsequently, the samples have been neutralized with Tris–HCl (pH 7.5, 5 min × 3 instances), stained with PI for 10 min, photographed by Leica fluorescence microscope, and analyzed by Comet Assay Software program Mission (CASP). Apparent DNA tails might be noticed for HaCaTs and HEKas after UV publicity at 114 mJ cm−2 and 66.5 mJ cm−2, respectively (Extra file 1: Fig. S18). So, the corresponding UV doses have been chosen for the next cell safety check.

To evaluate the protecting impact towards DNA injury, HaCaTs or HEKas have been pretreated with TiO2, ZnO, or ZIF-8 on the focus of 60 µg mL−1 for 15 min and irradiated with UVB (114 mJ cm−2 for HaCaTs, 66.5 mJ cm−2 for HEKas). Comet assay was then carried out as above talked about.

Intracellular manufacturing of ROS HaCaT cells and HeKa cells (2.5 × 105) have been seeded in 24-well plates and incubated for twenty-four h, pretreated with TiO2, ZnO, or ZIF-8 on the focus of 60 µg mL−1 for 15 min and irradiated with UVB or UVA (UVB: 350 mJ cm−2 for HaCaTs, 180 mJ cm−2 for HEKas; UVA: 100 mJ cm−2 for HaCaTs, 60 mJ cm−2 for HEKas). Thereafter, the cells have been handled with 2′,7′—dichlorofluorescein diacetate (DCFH-DA) reactive oxygen species assay kits following the manufacture directions. The intracellular ROS ranges have been assessed utilizing confocal fluorescent microscopy and movement cytometry. (Detrimental management: Cells with out UV publicity and with out UV safety; Constructive management: Cells with UV publicity however with out UV safety.)

Protecting results on mice and pig pores and skin The dorsal pores and skin of every male BALB/c mouse (6-weeks previous) was demarcated into six squares (1 cm × 1 cm), uncovered to UV at varied doses (172, 206, or 240 J m−2, respectively) to optimize UV dose. After three days, apparent erythema was noticed for the pores and skin with UV publicity at dose of 206 J m−2 and this UV dose was chosen for additional use (Extra file 1: Fig. S23). To optimize ZIF-8 dose, the pores and skin squares have been handled with ZIF-8 (1.5 μL) for 15 min with concentrations of 10%, 15%, or 20%, respectively, and uncovered to UV at 206 J m−2. After three days, no apparent erythema was noticed for the pores and skin with ZIF-8 safety on the dose of 15%, so this ZIF-8 dose was chosen for additional use (Extra file 1: Fig. S24). To evaluate anti-UV impact, the pores and skin squares have been randomly handled with glycerol, TiO2, ZnO, or ZIF-8 (15%, 1.5 μL) for 15 min, uncovered to UVB radiation (206 mJ cm−2) and photographed after 3 days. The mice have been fed individually in the course of the experiment. On the finish time level, the pores and skin was fastened with 4% paraformaldehyde, embedded in paraffin, sectioned with a thickness of 4 µm and subjected to Hematoxylin and Eosin (H&E) staining, Masson’s trichrome staining, or immunohistochemistry for CPD and IL-1β, respectively. The pores and skin with out safety was used as management. In these assessments, the mouse and pig pores and skin have been pretreated with filters for 15 min following the World Well being Group (WHO) suggestion with minor adjustments, with the aim to not have an effect on the SPF worth of those sunscreens [54, 55].

In vivo ROS in mouse pores and skin after UV publicity The dorsal pores and skin (1 cm × 1 cm) of every mouse was handled with glycerol (1.5 μL), TiO2, ZnO, and ZIF-8 (15%, 1.5 μL) for 15 min, respectively. Thereafter, the pores and skin was uncovered with UVB (18 mJ m−2) and picked up after 3 h. After that, the cells have been indifferent from the pores and skin and stained utilizing DCFH-DA. The ROS stage was assessed utilizing movement cytometry.

In vivo penetration into mouse pores and skin The dorsal pores and skin of the mice was demarcated into 5 squares (1 cm × 1 cm) after the hair was eliminated and randomly handled for six h with glycerol (1.5 μL), TiO2, ZnO, and ZIF-8 (15%, 1.5 μL), respectively. In the course of the experiment, the mice have been fed with 0.1 mL of water per hour by intragastric administration and heated on a pad at 37 °C. After that, the skins have been topically washed with PBS (37 °C, 5 min × 3 instances) and dried. The pores and skin samples have been collected and stripped for 30 instances with tape, wiped with ethanol swabs for 3 instances, weighed, and lysed with 70% HNO3 for 12 h. The degrees of Zn2+ and Ti4+ within the pores and skin have been measured utilizing ICP-MS. The pores and skin with out therapy was used as management.

In vivo long-term toxicity The mice have been randomly divided into 5 teams as above talked about. The dorsal pores and skin was gently outlined into 2 cm × 2 cm squares utilizing purple surgical marker and handled with glycerol (6 μL), TiO2, ZnO or ZIF-8 (15%, 6 μL) for 15 min each different day and 6 instances in complete. Three days after the final therapy, the pores and skin, coronary heart, liver, spleen, lung, kidney was collected, the paraffin part and the next H&E staining have been carried out. Additionally, the Ti or Zn ranges in coronary heart, liver, spleen, lung, kidney, or blood have been measured utilizing ICP-MS. Moreover, blood biochemical parameters have been measured to evaluate the system toxicity, together with alkaline phosphatase (AKP), aspartate aminotransferase (AST), and alanine transaminase (ALT) for liver perform, and creatinine (CRE) and serum urea nitrogen (BUN) for kidney perform.

In vivo anti-UV impact on pig Ba-Ma miniature pig (60–90 days previous, male) was anesthetized with 3.5% sodium pentobarbital (0.3 mL kg−1) and 10% xylazine hydrochloride injection (0.3 mL kg−1). In the course of the experiment, the pig was given with supplemental anesthetics when needed. The pores and skin was demarcated into squares (1 cm × 1 cm) after the dorsal hair was eliminated. Thereafter, the pores and skin squares have been uncovered to UV at varied doses (442, 544, or 646 J m−2, respectively) to optimize UV dose. After someday, apparent erythema was induced by UV publicity at dose of 544 J m−2 and this UV dose was chosen for additional use (Extra file 1: Fig. S28). To optimize ZIF-8 dose, the pores and skin squares have been handled to ZIF-8 for 15 min with 1.5 μL of ZIF-8 at concentrations of 10%, 15%, or 20%, respectively, and uncovered to UV at 544 J m−2. After someday, erythema was efficiently inhibited by ZIF-8 safety with focus of 15%, nevertheless, apparent erythema might nonetheless be seen for the pores and skin with ZIF-8 therapy at 10%, so ZIF-8 dose at 15% was chosen for additional use (Extra file 1: Fig. S29). To evaluate anti-UV impact of ZIF-8 on pig, the pores and skin squares have been randomly pretreated with glycerol (1.5 μL), TiO2, ZnO, or ZIF-8 (15%, 1.5 μL) for 15 min, uncovered to UVB radiation (544 mJ cm−2) and photographed once more after 24 h. The pores and skin was collected, and the paraffin part was carried out, adopted by H&E staining, Masson’s trichrome staining, and γH2AX immunofluorescence staining. The pores and skin with out safety was used as management.

Ex vivo penetration into pig pores and skin Contemporary pig pores and skin was minimize into items (1 cm × 1 cm), topically handled with glycerol, TiO2, ZnO or ZIF-8 (1.5 μL, 15%), respectively, and incubated at 32 °C in a humidity chamber for six h. The degrees of Zn2+ and Ti4+ within the skins have been assessed utilizing ICP-MS after therapy following the strategies within the part of “In vivo ZIF-8 penetration into mouse pores and skin”. The pores and skin with no therapy was used as management.

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