Jabuticaba (Myrciaria Jaboticaba) Peel As A Sustainable Source Of Anthocyanins And Ellagitannins Delivered By Phospholipid Vesicles For Alleviating Oxidative Stress in Human Keratinocytes Part 2

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2.3. In Vitro Studies with Keratinocytes

2.3.1.Biocompatibility of Vesicles

The study performed to evaluate the physicochemical properties of transfersomes, especially those enriched with the polymers, confirmed their greater stability and ideal size to be applied on the skin. Any important difference was detected as a function of the polymer concentrations(1 or 2 mg/mL). In order to assess this, the vesicles modified with the highest polymer concentration (2 mg/mL) were used to perform the subsequent studies. Their biocompatibility was evaluated using keratinocytes and that of the extract in aqueous dispersion was evaluated as well and used as a comparison. Keratinocytes have been chosen as they are the most representative cells of the epidermis and a layer-by-layer setup was used since in their special differentiation they form the main barrier of the skin, which regulates skin hydration and prevents exogenous substances from penetrating into and through it. Keratinocytes were treated for 48 h with the extract in dispersion or incorporated within the vesicles at four different dilutions, after which the cell viability was measured (Figure 3). The viability of cells incubated with the extract in dispersion was ~88%(p<0.05 versus the viability measured using extract loaded vesicles), indicating that the extract is not toxic. The viability of cells treated with extract-loaded transfersomes and hyaluronan-transfersomes at higher dilutions was~100% (p>0.05 among this group). The treatment with HEcellulose-transfersomes and hyaluronan-transfersomes further improved cell viability. All formulations were highly biocompatible regardless of the polymer and dilution used. Indeed, the cell viability was equal to or higher than 100%,even showcasing a proliferative effect associated with vesicle loading.

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2.3.2. Protective Effect of the Extract, in Dispersion or Loaded in Vesicles, against Damage Induced in Keratinocytes by Hydrogen Peroxide

The keratinocytes were stressed with hydrogen peroxide and then treated with the extract either in dispersion or loaded into transfersomes. The cell viability was measured at 4 h and this was used to evaluate the protective effect of the formulations against oxidative stress (Figure 4). The samples were diluted with the cell medium to reach two different concentrations (4 and 0.4 ug/mL). The hydrogen peroxide stress caused high cell mortality and reduced viability by up to~50%(p<0.05 versus the viability of cells treated with the extract in dispersion or loaded in vesicles)[35]. Hydrogen peroxide is considered one of the most dangerous oxidative molecules among the different reactive oxygen species, capable of promoting apoptosis and cell death. The treatment of stressed cells with the aqueous dispersion of the extract was capable of reducing the damaging effect of hydrogen peroxide as the viability increased up to~78%(p<0.05 versus the viability of cells treated with the extract loaded in HEcelluose-transfersomes at a higher dilution and hyaluronan-transfersomes), although the complete restoration of normal conditions was not achieved (Figure 4). Treatment with the extract-loaded transfersomes protected the cell to the same extent as the extract in dispersion (~82%,p>0.05 versus the viability of cells treated with dispersion). The treatment with the best result was the extract loaded with HEcellulose-transfersomes(at a higher dilution)and hyaluronan-transfersomes, which achieved a viability of~104%(p<0.05 versus the values of other treatments). The restored normal conditions and even slightly promoted cell proliferation, probably due to the synergic effect of the extract and the polymer-immobilized vesicles. The vesicle behavior was not affected by the dilution levels of the samples.

2.3.3. In Vitro Wound Healing Effects

The in vitro scratch assay was performed with a monolayer of keratinocytes in order to verify the ability of the extract in aqueous dispersion or incorporated into vesicles to stimulate the proliferation and migration of cells. Empty vesicles were not tested as in a previous study no improvement in wound healing was detected when empty hyalurosomes were used [37]. The closure of the performed wound was monitored for 48 h (Figure 5)and the% of closure was calculated by measuring the lesion areas (Figure6). The wound closure of untreated cells occurred very slowly—13% at 24 h, 28% at 36 h, and only 40%at 48 h. Treatment with the extract in water dispersion slightly improved the process and brought the closure at 48 h to 50%. Treatment with the extract-loaded vesicles at 48 h achieved 90% closure when using transfersomes and HEcellulose-transfersomes and around 100% closure when using hyaluronan-transfersomes. As we can see, the wound closure was almost complete, confirming the restoring properties of the extract-loaded hyaluronan-transfersomes.

Our overall results confirmed the high biocompatibility of hyaluronan-transfersomes, which were also the most effective at stimulating the proliferation and migration of skin cells and counteracting the damage induced in skin by oxidative stress.

3. Materials and Methods 3.1. Materials

Lipoid S75 (consisting of~70% of soy phosphatidylcholine, 9%phosphatidylethanolamine, and 3% lyso-phosphatidylcholine)was purchased from Lipoid GmbH(Ludwigshafen, Ger-many).Sodium hyaluronate with low molecular weight (200-400 kDa) and a polydispersity of 1.4 Mw/Mn, was purchased from DSM Nutritional Products AG Branch Pentapharm (Switzerland). Tween 80, glycerol, DPPH radical (2,2-diphenyl-1-picrylhydrazyl), ferric chloride hexahydrate, gallic, chlorogenic, and ascorbic acids, catechin, tetrazolium salt, 3-(4,5-dimethylthiazol-2-vl)-2,5-diphenyltetrazolium bromide(MTT), quercetin, Neosporin, Folin-Ciocalteu's phenol reagent,2,4,6-tris(2-pyridyl)-S-triazine(TPTZ) and pvrocatechol violet were purchased from Sigma-Aldrich (Milan, Italy). Potassium hexacyanoferrate (ⅢI) was obtained from Merck(Darmstadt, Germany). Anhydrous sodium acetate, copper sulfate pentahydrate and copper chloride dihydrate were obtained from VWR Chemi-cals BDH⑧(Frankfurt, Germany). Cyanidin 3-O-glucoside (≥95%)and delphinidin 3-O-glucoside(≥95%) were purchased from Extrasynthese(Lyon, France). Glacial acetic acid and phosphoric acid (85%)were acquired from J.T.Baker (Mallinckrodt Baker Inc., Utrecht, The Netherlands). All reagents and plastics for cell culture were purchased from Life Technologies Europe (Monza, Italy).

3.2. Jabuticaba Pees: Extraction, Chemical Characterization, and Antioxidant Activity

Jabuticaba fruits (Myrciaria jabuticaba (Vell.)O.Berg)cv. Sabara was harvested at a ripe maturation stage in Araucaria city， Paranå， Brazil（geographical coordinates∶25°2924.7" S49°2637.8"W) in December 2018. Fruits were washed and sanitized (NaOCl at 100 mg/L/15 min), rinsed, and pulped manually. Peels were dried at 35°℃ for 50 h, ground to reach 42 Tyler mesh, and extracted in an accelerated solvent extractor(ASE-350, Dionex, Sunnyvale, CA, USA), employing a pressure of 100 bar(98.7 atm) in two extraction cycles at 50°C. Water acidified with citric acid(pH 2.10)was used as the solvent and extractions were repeated four times. Then, extracts were filtered using qualitative paper and freeze-dried under vacuum for 120 h. Following this, the extraction yield, expressed as a percentage, was calculated concerning the raw material used in the procedure.

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The total phenolic content (TPC, mg of gallic acid equivalent per 100 g, mg GAE/100 g)total condensed tannin (TCT, mg of catechin equivalent per 100 g, mg CE/100 g), total flavonoids(TF, mg CE/100 g)and total ortho-diphenols content (TOD, mg of chlorogenic acid equivalent per 100 g, mg CAE/100 g)were measured in triplicate by using UV-Vis spectrophotometry according to the procedures fully described by do Carmo et al. [20].

Anthocyanins (cyanidin 3-O-glucoside and delphinidin 3-O-glucoside)were quantified by high-performance liquid chromatography (HPLC) using an Agilent 1100(Agilent Technologies Inc., Espoo, Finland) device equipped with diode array detection (DAD). Separation was performed using a Gemini C18 column （150 mm×4.6 mm， 5 μm） with a gradient elution of acetonitrile acidified with formic acid at 5%. Total ellagitannin content was determined after acid hydrolysis, according to Mattila and Kumpulainen [38], and gallic acid was determined using an Inertsil ODS-3 column （150 mm ×4.0 mm， 3 μm）with a gradient elution of acetonitrile into 50 mmol/L H3PO4(pH 2.5). Analyses were performed in triplicate and results were expressed as mg/100 g. Ultra-high performance liquid chromatography(UHPLC) combined with high-resolution mass spectrometry (MS) was applied for the characterization of major ellagitannins and anthocyanins. An Acquity UPLC-Xevo G2 QTOF mass spectrometer (Waters, Milford, MA， USA）was equipped with a Waters Acquity BEH C18 （1.7 μm，2.1 mm × 150 mm）column and the separation was performed using a gradient of acetonitrile into water acidified with 0.1% formic acid, according to Santos et al. [39]. The flow rate was 0.55 mL/min, the temperature of the column oven was 45°C and the injection volume was 1.0 μL. An electrospray interface (ESI) in negative and positive mode was used with capillary voltages of -1 kV and +0.5 kV, respectively. Argon was used as the collision gas. MS analyses were conducted by data-independent acquisition (MSE) centroid data model in a full scan m/z 50-1500 with 0.2 s scan time. In the MSE function, the precursor ions of MS were fragmented using high collision energy ramped up from 25 to 45 V.

The antioxidant activity of the extract was analyzed in triplicate by using different assays: free-radical scavenging activity in relation to the DPPH radical, ferric reducing antioxidant power (FRAP), cupric-ion reducing antioxidant capacity (CUPRAC), reducing power, and Cu2+ chelating ability. Results were expressed as mg GAE/100 g (reducing power), mg of ascorbic acid equivalent per 100 g, mg AAE/100 g (DPPH, FRAP, and CUPRAC), and mg EDTA equivalents/100 g (metal chelation), respectively. All methods used have been deeply described previously by do Carmo et al. and Fidelis et al. [9,20].

3.3. Vesicle Preparation

Transfersomes, hydroxyethylcellulose enriched transfersomes (HEcellulose-thansferomes), and sodium hyaluronate enriched transfersomes(hyaluronan-transfersomes) were prepared by dispersing phospholipid (S75, 180 mg/mL), Tween 80(20 mg/mL), extract (40 mg/mL) and polymer (hydroxyethylcellulose or sodium hyaluronate 1 and 2 mg/mL), when appropriate, in water and leaving the blends to hydrate for a few hours. Following this， the dispersions were sonicated （4 cycles 2 on 5 off 15.0μ amplitude）， waiting 5 min between each cycle to promote cooling and avoid overheating of the sample. A high-performance Soniprep 150 sonicator (MSE Crowley, London, UK)was used to sonicate all dispersions in order to obtain a homogeneous system with a small size [15]. This procedure avoids the loss of the components used for the preparation, leading to the formation of performant vesicles capable of incorporating high amounts of the extract.

3.4. Characterization of the Vesicles

The average diameter and the polydispersity index(a dimensionless measure of the broadness of the size distribution) of the vesicles were measured by photon correlation spectroscopy using a Zetasizer Ultra (Malvern Instrument, UK). The same equipment was used to measure the zeta potential of vesicles by measuring the electrophoretic mobility of particles [40]. The samples were suitably diluted before measurement to be optically clear and avoid the reduction of scattered light that can be detected. To evaluate the amount of extract actually incorporated into the vesicles, the dispersions were purified from the non-incorporated extract by dialysis. Vesicle dispersions (1 mL) were inserted into polycarbonate dialysis tubes (Spectra/Pormembranes:12-14 kDa MW cut-off, with pores 3 nm; Spectrum Laboratories Inc., Rancho Dominguez, CA, USA) and immersed in distilled water(2 L) at 25°C for 2 h under stirring. The water was refreshed after one hour, thus using 4 L of water to solubilize the bioactive molecules not incorporated in 1 mL of vesicle dispersion (40 mg). The amount of extract in the vesicle suspensions before and after the dialysis was quantified measuring their antioxidant activity using the DPPH assay. The entrapment efficiency of the extract inside the vesicles was calculated as a percentage ratio between the antioxidant activity of the samples before and after the purification process [41-43].

3.5. Stability of Vesicles on Storage

The stability of the vesicles in the dispersion was evaluated by monitoring their average size, the polydispersity index, and the surface charge for 90 days while keeping the dispersions at room temperature (25± 1°C).

3.6.Measurement of the Antioxidant Activity of Samples Using the DPPH Colorimetric Test The antioxidant activity of jabuticaba peel extract loaded into vesicles was measured as a function of its ability to scavenge DPPH. The dispersions（10 μL） were diluted （1∶100）with a methanolic solution of DPPH(0.4 ug/mL). The diluted samples were stored at room temperature and in the dark for 30 min, then the absorbance of the solutions was measured at 517 nm using a UV spectrophotometer. The antioxidant activity of the formulations was calculated according to Equation (1): (1)Antioxidant activity%=[(ABSDPPH-ABSample)/ABSpPPH]×100

3.7.Biocompatibility and Protective Effect of Samples against Oxidative Stress in Keratinocytes

Immortalized human keratinocytes (HaCaT)were grown as monolayers at 37°C, with 100% humidity and 5% CO2 using Dulbecco's Modified Eagle Medium (DMEM) high glucose supplemented with foetal bovine serum, penicillin and streptomycin as a growth medium. To evaluate the biocompatibility of formulations, cells were seeded into 96-well plates at a density of 7.5 × 10° cells/well. After 24 h, cells were treated for 48 h with jabuticaba extract in aqueous dispersion or loaded in vesicles properly diluted with DMEM to reach different concentrations of the extract(40, 4, 0.4, and 0.04 ug/mL). At the end of the incubation, MTT [3(4,5-dimethyl thiazolyl-2)-2, 5-diphenyltetrazolium bromide]（100 μL， 0.5 mg/mL final concentration） was added to each well， and， after three hours， the formed formazan crystals were dissolved with dimethyl sulfoxide. The absorbance of each well was measured at 570 nm using a microplate reader (Synergy 4 Reader, BioTek Instruments, AHSI S.p.A, Bernareggio, Italy). All experiments were repeated at least three times, each time in triplicate. Results are shown as percent of cell viability in comparison with untreated control cells (100% viability).

The in vitro protective effect of formulations against damage caused by oxidative stress was evaluated as well. Cells were seeded into 96-well plates at a density of 7.5× 10cells/well. After 24 h of incubation, cells were stressed with hydrogen peroxide (30% diluted 1:40,000 v/o with PBS) and treated with the extract in aqueous dispersion or loaded in vesicles and diluted to reach two different concentrations(4 and 0.4 ug/mL,). Cells stressed with hydrogen peroxide only were used as a negative control, while untreated cells were used as a positive control. After 4 h of incubation, cells were washed with a fresh medium and their viability was determined by the MTT assay. Results are reported as the percentage of untreated cells (100% viability).

3.8. In Vitro Wound Healing Properties

The ability of the jabuticaba peel extract loaded into vesicles to remodel the skin lesions and promote their healing was evaluated by measuring the cell expansion on a lesion in a cell monolayer. The cells were cultured in 6 well plates until a complete and homogeneous monolayer was reached. A linear wound was generated using a sterile plastic pipette tip. The scattered fragments of cells were removed by gentle washing with a fresh medium. Extract aqueous dispersion or extract-loaded vesicles were diluted with cell medium up to4 ug/mL of extract and used to treat the lesioned cell monolayers. The cell lesions were observed, and the images were captured at 24, 36, and 48 h of incubation using an optical microscope with a 10× objective. Untreated cells were used as a negative control. The area lesions in the captured images were measured by Java's image J software (http://rsb.info.nih.gov, accessed in April-June 2021). The closure of the wounds was calculated using Equation (2):

where ao is the wounded area immediately after scratching, and a is the wounded area measured at 24, 36, and 48 h [44].

3.9. Statistical Analysis

Results are expressed as the mean ± standard deviation and significance was tested at the 0.05 level of probability (p). For size, zeta potential, viscosity, drug accumulation, and cytotoxicity, one-way analysis of variance(ANOVA) was used to substantiate statistical differences between groups followed by Tukey's test, while Student's t-test was used for comparison between two samples using XLStatistic for Excel.

4. Conclusions

The lyophilized jabuticaba peel extract was incorporated into transfersomes and polymer (hydroxyethylcellulose and sodium hyaluronate) enriched transfersomes with the aim of stabilizing the extract and improving its therapeutic efficacy. The obtained vesicles were small in size and homogeneously dispersed. The addition of both polymers only led to the formation of slightly larger vesicles without differences between the polymeric concentrations used. Polymer-enriched vesicles seemed to be ideal for topical administration and were capable of incorporating the bioactive-rich extract in high amounts. In particular, the combination of a phospholipid, Tween 80, and sodium hyaluronate to obtain Hyaluronan-transfersomes, has been selected as the best formulation in terms of stability and ability to interact with keratinocytes, as only these vesicles were able to effectively counteract the damage induced in cells when using hydrogen peroxide and to promote wound healing in human keratinocytes. Overall, our results suggested that hyaluronan-transfersomes may represent a promising system for the treatment of skin diseases or skin wounds connected with oxidative stress. In addition, we show for the first time the use of jabuticaba peel extract in a dermatological delivery system.

Author Contributions: D.G., M.L.M., M.M.: conceptualization, formal analysis, data curation, writing, and review; I.C., M.A., J.H: formal analysis and writing. All authors have read and agreed to the published version of the manuscript.

Funding: This research received no external funding. Institutional Review Board Statement: Not applicable. Informed Consent Statement: Not applicable.

Data Availability Statement: Raw data are available and can be asked directly to authors.

Conflicts of Interest: The authors declare no conflict of interest.

Sample Availability: Samples of the jaboticaba peel extract are available from the authors.

This article is extracted from Molecules 2021, 26, 6697. https://doi.org/10.3390/molecules26216697 https://www.mdpi.com/journal/molecules