Research Article |
Corresponding author: Denitsa Momekova ( dmomekova@pharmfac.mu-sofia.bg ) Academic editor: Plamen Peikov
© 2024 Denitsa Momekova, Viliana Gugleva, Petar Petrov.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Momekova D, Gugleva V, Petrov P (2024) Development and evaluation of curcumin-loaded vesicular carriers: impact of formulation variables. Pharmacia 71: 1-8. https://doi.org/10.3897/pharmacia.71.e127997
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Vesicular carriers are a well-established approach to improving the technological and biopharmaceutical characteristics of the loaded cargo. The current manuscript is focused on the development and evaluation in a comparative aspect of two types of vesicles—ethosomes and transfersomes loaded with the phytoconstituent curcumin. The formulation variables affecting their physiochemical and cytotoxic properties are outlined as well. A series of ethosomes and transfersomes based on Lipoid S75 and ethanol, or edge activator, were prepared using the thin film hydration method and subjected to comprehensive evaluation by dynamic light scattering (DLS) analysis, transmission electron microscopy (TEM), entrapment efficiency evaluation, in vitro release, and cytotoxicity studies. Ethosomes based on Lipoid S75 (4% w/w) and ethanol (30% v/v) showed suitable physicochemical characteristics (hydrodynamic diameter of 578.6 nm, monomodal size distribution, high curcumin entrapment efficiency (78.2%)), and superior antiproliferative activity compared to free drug and transfersomal nanocarriers.
biological active compounds, curcumin, antineoplastic activity, topical delivery, ethosomes, transfersomes
Bioactive compounds from natural origin exhibit a variety of advantageous effects when applied to skin; however, often their physicochemical characteristics, such as high molecular weight, strictly hydro-lipophilicity, and high degree of ionization, may hinder their successful dermal and transdermal delivery (
Curcumin is a plant phenolic compound (curcuminoid) isolated from the roots of Curcuma longa and extensively used in traditional medicine and current therapeutics owing to its diverse pharmacological effects, such as antioxidant, anti-inflammatory, antimicrobial, antiviral, and anti-proliferative (
Vesicular systems such as liposomes and niosomes have been widely investigated as drug delivery platforms capable of preserving the chemical stability of the encapsulated cargo and improving its bioavailability for various routes of administration (
The aim of this study was to develop curcumin-loaded vesicular carriers—transfersomes and ethosomes—and to evaluate in a comparative manner the impact of the composition variables on their physicochemical, drug release, and cytotoxic characteristics.
Curcumin, Tween 20, Tween 60, and Tween 80 were obtained from Sigma-Aldrich (St. Louis, MO, USA). Lipoid S75 (Soya phosphatidylcholine) was a generous gift from Lipoid GmbH (Ludwigshafen, Germany). All other solvents and reagents used were of analytical grade.
Ethosomes and transfersomes (blanc and curcumin-loaded) were prepared by the thin film hydration method (
Transfersomes were prepared following the same procedure and maintaining the constituents’ concentrations (Lipoid S75 3% w/v, curcumin 0.0025% w/v) constant. After the formation of the lipid film, it was hydrated for 45 minutes with purified water containing different edge activators (Tween 20, Tween 60, and Tween 80) in concentrations of 0.3% and 0.60% (w/v). The obtained transfersomal dispersions were further sonicated for 10 minutes in a sonication bath (ArgoLab DU-32, Capri, Italy), then transferred into vials and stored at 4 ± 2 °C for subsequent studies.
The hydrodynamic diameter (Dh) and polydispersity index (PDI) of the nanocarriers were determined by applying the dynamic light scattering technique. The experiment was performed at 25 °C using Zetasizer Ultra (Malvern Panalytical Ltd., Malvern, UK), equipped with a 633 nm laser. The samples were properly diluted (1:300 v/v) with distilled water and measured using a back-scattering angle of detection of 173°. The zeta potential of the formulations was assessed via electrophoretic light mobility using Zetasizer Ultra (Malvern Panalytical Ltd., Malvern, UK) following the same dilution protocol. The values are presented as mean ± standard deviation (SD) from three measurements.
The morphology of optimal ethosomal and transfersomal formulations was assessed by transmission electron microscopy. A drop of nanovesicles’ suspensions was placed onto a carbon-coated copper grid and allowed to dry at ambient temperature for 10 minutes. A solution of phosphotungstic acid (1% w/v) was used as a staining agent, placed onto the formulations, and after excess’ removal, the samples were analyzed with a transmission electron microscope (JEOL JEM-2100), equipped with a digital camera, at an accelerating voltage of 200 kV and proper magnification.
Curcumin entrapment efficiency in the vesicular carriers was evaluated by the ultracentrifugation method (
(1)
Curcumin release from ethosomes and transfersomes was evaluated by the dialysis method against phosphate-buffered saline (PBS) of pH 5.5 at 32 °C (
To evaluate curcumin release kinetics from the prepared ethosomes and transfersomes, in vitro release data was fitted with different mathematical models (zero order, first order, Higuchi, and Korsmeyer-Peppas models). The highest values obtained for the coefficient of determination (R2) indicated the most suitable kinetic model.
The stability of optimal curcumin-loaded ethosomal and transfersomal formulations was investigated in terms of alterations in the physicochemical properties (Dh, PDI, zeta potential, EE%) of the vesicles after one-month storage in the refrigerator (4 ± 2 °C). A macroscopic evaluation of the appearance of vesicular dispersions was also performed.
The cytotoxic activity of curcumin and its nanovesicular formulations was evaluated against HUT-78 cells (cutaneous T-cell lymphoma, CTCL Sézary syndrome). The cell lines were purchased from the German Collection of Microorganisms and Cell Cultures (DSMZGmbH, Braunschweig, Germany). The growth medium was 90% RPMI-1640 + 10% FBS. The cells were cultivated in a controlled environment—cell culture flasks at 37 °C in an incubator ‘BB 16-FunctionLine’ Heraeus (Kendro, Hanau, Germany) with a humidified atmosphere and 5% CO2.
The cytotoxicity of free or loaded curcumin into ethosomes and transferosomes was evaluated by an MTT-dye reduction assay against HUT-78 (cutaneous T-cell lymphoma, CTCL-Cesary syndrome). In brief, exponentially growing cells were plated in 96-well flat-bottomed plates (100 µL/well) at a density of 1×105/mL and were incubated for 24 h at 37 °C. Afterwards, cells were exposed to varying concentrations of the tested formulations and the free drug for 72 h. At least 8 wells were used for each concentration. After the needed time for exposure, 100 µL of MTT solution (10 mg/mL in PBS) were added to each well. Afterwards, the samples were incubated for 4 h at 37 °C, and the MTT-formazan crystals that had formed were then dissolved by adding 5% formic acid-acidified 2-propanol. The MTT formazan absorption was recorded using a LabeximLMR-1 microplate reader at 580 nm. Cell survival fractions were calculated as a percentage of the untreated control. In addition, IC50 values were derived from the concentration-response curves.
A series of ethosomes and transfersomes were prepared via the thin film hydration method, and the impact of constituents on their physicochemical characteristics was assessed. Next, optimal formulations were selected for further cytotoxic investigation. Although the thin film hydration method is the most established technique for the preparation of vesicular carriers, it may often determine the formation of non-uniform-size vesicles, unless followed by subsequent sonication or extrusion steps. Therefore, the initial aim of our study was to optimize the process parameters in order to obtain formulations with suitable physicochemical parameters. The ethosomes prepared via the thin film hydration method were characterized by sizes ranging between 578 and 871 nm, high zeta potential values, and curcumin entrapment efficiency ranging within 69–81%. The subsequent sonication of curcumin-loaded vesicles (E2) was not found to exert a beneficial effect on their properties; therefore, this step was not included in the ethosomes’ preparation protocol. Opposite results were evident in the case of transfersomes, where the sonication process led to a decrease in vesicles’ size and PDI values without compromising the colloidal stability of the dispersions (Table
Composition and physicochemical properties of curcumin-loaded ethosomes (E) and transferosmes (T). In each drug-loaded formulation, the curcumin concentration was maintained constant (0.0025% w/v).
Vesicular nanocarrier code | Lipoid S75 (% w/v) | Ethanol (% v/v) | Edge activator (% w/v) | Dh (nm) ± SD | PDI ± SD | ζ-potential (mV) ± SD | EE (%) ± SD |
---|---|---|---|---|---|---|---|
E1 | 3 | 20 | - | 871.1 ± 16.34 | 0.16 ± 0.06 | -42.14 ± 4.67 | 69.1 ± 2.21 |
E2 | 3 | 30 | - | 722.2 ± 7.70 | 0.22 ± 0.01 | -53.24 ± 1.15 | 81.5 ± 1.61 |
E2 sonicated | 3 | 30 | - | 552.6 ± 14.48 | 0.30 ± 0.02 | -50.23 ± 1.35 | 76.2 ± 0.86 |
E2 blanc | 3 | 30 | - | 786.9 ± 3.18 | 0.08 ± 0/03 | -30.72 ± 1.26 | - |
E3 | 3 | 40 | 627.7 ± 15.25 | 0.41 ± 0.03 | -59.28 ± 1.32 | 75.1 ± 1.19 | |
E4 | 2 | 30 | - | 778.1 ± 4.47 | 0.29 ± 0.01 | -44.49 ± 0.40 | 73.7 ± 2.23 |
E5 | 4 | 30 | - | 578.6 ± 4.54 | 0.20 ± 0.02 | -65.96 ± 3.60 | 78.2 ± 1.76 |
T1 sonicated | 3 | - | Tween 20 0.3% | 881.1 ± 43.21 | 0.57 ± 0.03 | -69.78 ± 1.69 | 59.4 ± 0.95 |
T2 unsonicated | 3 | - | Tween 60 0.3% | 1383 ± 58.62 | 0.75 ± 0.14 | -62.65 ± 1.31 | 70.7 ± 2.35 |
T2 sonicated | 3 | - | Tween 60 0.3% | 1245 ± 65.27 | 0.55 ± 0.04 | -60.11 ± 1.14 | 63.5 ± 2.39 |
T2 blanc sonicated | 3 | - | Tween 60 0.3% | 817.6 ± 29.5 | 0.56 ± 0.1 | -55.16 ± 1.78 | - |
T3 sonicated | 3 | - | Tween 80 0.3% | 808.1 ± 31.75 | 0.50 ± 0.06 | -70.31 ± 1.45 | 64.8 ± 2.76 |
T4 sonicated | 3 | - | Tween 20 0.6% | 796 ± 21.19 | 0.41 ± 0.01 | -56.12 ± 1.18 | 57.5 ± 2.17 |
T5 sonicated | 3 | - | Tween 60 0.6% | 802.4 ± 13.93 | 0.31 ± 0.05 | -59.81 ± 1.13 | 65.4 ± 1.15 |
T6 sonicated | 3 | - | Tween 80 0.6% | 787 ± 10.46 | 0.46 ± 0.03 | -57.38 ± 1.15 | 60.9 ± 1.89 |
Besides the preparation techniques, the formulation constituents also have a major impact on the physicochemical properties of the nanocarriers. As evident from the presented data (cf. E1, E2, and E3), increasing ethanol concentration determines a reduction in vesicles’ size, which may be attributed to a decrease in the ethosomal membrane thickness following interpenetration of the alcohol hydrocarbon chain at higher concentrations (
Regarding transfersomal formulations, the impact of type (Tween 20, Tween 60, and Tween 80) and concentration (0.3% and 0.6%) of edge activators on the main physicochemical parameters was studied. As evident from the obtained results, both of the investigated variables strongly affect the properties of the vesicles. There is an inverse relationship between the hydrophilic-lipophilic balance (HLB) values of edge activators and the obtained entrapment efficiency data. The highest curcumin encapsulation was estimated in the vesicles comprising Tween 60 (vs. Tween 20 and Tween 80-based ones), irrespective of the concentration (0.3 or 0.6% w/v). The obtained results also correlate with the molecular weight (Mw) of the surfactants; higher Mw values correspond to a higher percentage of entrapped curcumin. Tween 60-transfersomes are characterized by larger sizes, whereas Tween 80-based ones exhibit the smallest dimensions. As both edge activators (Tween 60 and Tween 80) have the same chain length (18C) and close HLB values (14.9 and 15, respectively), the obtained outcomes may be related to the presence of a double bond in the Tween 80 chain, which probably determines the formation of a more compact vesicular structure. A further decrease in transfersomal size was estimated by increasing the concentration of edge activators. The results may be attributed to surfactants’ ability to reduce the interfacial tension; hence, higher edge activators’ concentration contributes to size reduction. A slight decrease in curcumin entrapment efficiency was estimated in the compositions containing 0.6% (w/v) edge activators; however, the obtained values are still considered high (between 57.5% and 65.4%). Based on the obtained results, the optimal transfersomal composition for further studies was selected as composition T5. The size distribution curves of the selected curcumin-loaded ethosomes and transfersomes are illustrated in Fig.
The representative TEM micrographs of the elaborated nanocarriers (blank and curcumin-loaded) are illustrated in Fig.
Curcumin release from the selected ethosomal and transfersomal formulations was evaluated in a comparative manner under physiologically relevant conditions (Fig.
Release kinetic data for optimal ethosomal and transfersomal formulations.
Formulation | Zero order | First order | Higuchi | Peppas | |
---|---|---|---|---|---|
R2 | R2 | R2 | R2 | N | |
E | 0.887 | 0.946 | 0.990 | 0.985 | 0.404 |
T | 0.858 | 0.907 | 0.978 | 0.959 | 0.373 |
The physical stability of the selected ethosomes and transfersomes expressed in terms of alterations in size, size distribution pattern, zeta potential, and curcumin entrapment efficiency was evaluated by storing the formulations at 4–6 °C for 1 month. As evident from Table
Physical stability assessment of optimal curcumin-loaded ethosomes and transfersomes.
Sample | Size (nm) ± SD | PDI ± SD | ζ potential (mV) ± SD | EE (%) | ||||
---|---|---|---|---|---|---|---|---|
Initial | One month | Initial | One month | Initial | One month | Initial | One month | |
E5 | 578.6 ± 4.54 | 682 ± 12.74 | 0.20 ± 0.02 | 0.13 ± 0.03 | -65.96 ± 3.60 | -63.57 ± 2.27 | 78.2 ± 1.76 | 76.5 ± 1.98 |
T5 | 802.4 ± 13.93 | 889.7 ± 11.65 | 0.31 ± 0.05 | 0.30 ± 0.07 | -56.12 ± 1.18 | -54.98 ± 1.96 | 65.4 ± 1.15 | 63.2 ± 2.1 |
Cytotoxic effects after treatment of malignant HUT-78 cells with free or formulated curcumin ethosomes or transfersomes were investigated. Succeeding 72-h exposure to the free drug and its formulations showed a noticeable concentration-dependent reduction of cell viability, causing almost 82% eradication of treated cells at the highest tested concentrations of curcumin (0.05 mg/mL) (see Fig. 4А). It is worth mentioning that the encapsulation of curcumin inside both types of elaborated vesicles proved to significantly augment its antineoplastic activity. Thus, the equieffective IC50 values derived from non-linear regression analysis of concentration-effect curves for formulated curcumin were lower as compared to free agents (Table
Equivalent concentration (IC50) and modulation indices (MI) of free curcumin and its formulations against the human tumor HUT-78 cell line after 72 h exposure.
Sample | IC50 (mg/mL) | MI* |
---|---|---|
Free Curc | 0.031 | - |
Transferosomes:Curc (T5) | 0.025 | 1.24 |
Ethosomal:Curc (E5) | 0.020 | 1.55 |
To investigate whether the observed enhanced cytotoxic activity of nanoformulated curcumin is due only to the inherent cytotoxicity of the drug (not to the carrier itself), we performed an analogous study on HUT-78 cells treated with empty vesicles at equivalent concentrations of the lipid carrier as in the analogue-loaded counterparts. The data shown in Fig.
Curcumin-loaded ethosomes and transferosomes were elaborated and evaluated as nanoplatforms for dermal curcumin delivery. Both nanovesicular systems are characterized by high curcumin loading efficacy and controlled drug delivery, governed by the Fickian diffusion mechanism. In addition, both formulations are characterized by favorable storage stability. The bioassay data showed that the formulated curcumin was superior in terms of cytotoxic activity as compared to the free drug. The ethosomal formulation constrained the viability and proliferation of HUT-78 cells at lower micromolar concentrations as compared to free drugs and curcumin formulated in transferosomes. These findings give us the reason to conclude that the presented nanovesicles are feasible platforms to ensure augmentation of curcumin antiproliferative activity with a concomitant anticipated beneficial modulation of the skin permeation ability, based on the well-known generic properties of both types of vesicles, especially ethosomes.
Financial support by the European Union-Next Generation EU through the National Recovery and Resilience Plan of the Republic of Bulgaria, Project BG-RRP-2.004-0004-C01. Georgi Momekov from the Department of Pharmacology, Pharmacotherapy, and Toxicology at the Faculty of Pharmacy, Medical University-Sofia, is greatly acknowledged for the in vitro pharmacological evaluation of the developed nanosystems.