Article pubs.acs.org/Biomac
Biocellulose Membranes as Supports for Dermal Release of Lidocaine Eliane Trovatti,† Nuno H. C. S. Silva,† Iola F. Duarte,† Catarina F. Rosado,§ Isabel F. Almeida,‡ Paulo Costa,‡ Carmen S. R. Freire,*,† Armando J. D. Silvestre,† and Carlos Pascoal Neto† †
CICECO and Department of Chemistry, University of Aveiro, 3810-193 Aveiro, Portugal Laboratory of Pharmaceutical Technology/Centre of Research in Pharmaceutical Sciences (LTF/CICF), Department of Drug Sciences, Faculty of Pharmacy, University of Porto, Portugal § CBIOS - Experimental Dermatology Unit, Faculty of Sciences and Health Technologies, Lusófona University, Campo Grande 376, 1749-024 Lisboa, Portugal ‡
ABSTRACT: Biocellulose (BC) is a highly pure form of cellulose, produced in the form of a swollen membrane, with several applications in the biomedical area. In this study, the behavior of BC membranes as systems for topical delivery of lidocaine was evaluated. The BC-lidocaine membranes were prepared and characterized in terms of structural and morphological properties. A uniform distribution of the drug inside the BC membranes was observed. In vitro diffusion studies with Franz cells were conducted using human epidermal membranes and showed that the permeation rate of the drug in BC membranes was slightly slower than that obtained with the conventional systems, which was attributed to the establishment of interactions between the lidocaine molecules and the BC membrane, as evidenced by FTIR and NMR analysis. These results indicate that this methodology can be successfully applied for the dermal administration of lidocaine regarding the release profile and ease of application.
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purity, the unique physical and mechanical properties, arising from its tridimensional and branched nano- and microfibrillar structure, as well as the biocompatibility of BC, triggered considerable interest on this material, particularly in the biomedical area, namely as wound healing membranes, substituting natural skin,8 chirurgical implants, and specific technological applications such as audio membranes,9 electronic paper,10 and transparent nanocomposites,11−13 among others. Moreover, the peculiar nanofibrillar structure of BC should represent a perfect macromolecular support for inclusion of active compounds and therefore for the development of specific controlled release systems for drugs (antibiotics, analgesics, anti-inflammatories, hormones, and anticancer). However, despite the BC high potential in the biomedical field, only a few studies refer to its use or potential as a support for release of drugs have been reported.14,15 Additionally, recently BC was functionalized with polyvinyl alcohol (PVA),16 or prepared as molecular imprinted membrane matrix for drug delivery.17 BC membranes could be particularly advantageous in the design of topical drug delivery systems that have, simultaneously, the ability to absorb exudates and adhere to irregular skin surfaces, for example, for oral mucosa application. The main difficulties of topical formulations are related to the lack of reproducibility of the drug dose that is applied and to the loss of material because of contact with garments or surfaces. Both issues can be surpassed using BC systems. The dose can
INTRODUCTION
The high-quality standards of life attained by humanity in the last century, as a result of enormous development of science and technology, strongly contributed to the constant improvement or development of hygiene and health care products. Advanced medical textiles and polymers constitute a quite interesting and rapidly developing area because of their expansion in fields like wound healing, controlled drug release, bandaging and pressure garments, and implantable medical devices, among others.1 Numerous synthetic polymers, for example, poly(dimethylsiloxanes), polyvinyl alcohol, poly(hydroxyalkyl)acrylates, among others, are used for this purpose. 2 However, natural counterparts are gaining considerable attention because of their renewable and biodegradable character. Polysaccharides, one of the most abundant families of biopolymers, are usually nontoxic and biocompatible and show a number of peculiar physicochemical properties that make them suitable for different applications in drug delivery systems and wound healing.3 Among them, cellulose plays an important role in the biomedical field.4 Cellulose and its derivatives, like hydroxypropylmethylcellulose (HPMC), ethylcellulose (EC), and carboxymethyl cellulose (CMC), have a wide variety of applications for a long time in this area.5,6 Although most of the cellulose available on earth is produced by photosynthesis in green plants, some microorganisms like several bacteria from the Gluconacetobacter genus are also able to produce an extracellular form of cellulose, bacterial cellulose, or biocellulose (BC), in the form of a highly swollen membrane (with ∼99% water) on the culture medium surface.7 The high © 2011 American Chemical Society
Received: September 19, 2011 Published: October 16, 2011 4162
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Characterization of BC-Lidocaine Membranes. BC, BC-Ldc, and BC-Ldc-Glyc dried membranes were characterized in terms of structure, surface morphology, mechanical properties, and swelling behavior. Fourier transform infrared (FTIR) spectra were obtained in a Perkin-Elmer FTIR system spectrometer equipped with a single horizontal Golden Gate ATR cell. Thirty-two scans were acquired in the 4000−600 cm−1 range with a resolution of 4 cm−1. SEM micrographs of the membranes surfaces were obtained on a HR-FESEM SU-70 Hitachi equipment operating at 15 kV. Samples were coated with evaporated carbon. Tensile assays were performed on a Shimadzu machine TA-Hdi stable microsystems texture analyzer using a load cell of 5 kg operating at a deformation rate of 50 mm/s performed under ambient conditions. Five specimens were tested for each composite. Tensile strength, tensile modulus, and elongation at break were calculated using the Instron Series IX software. BC and BC-lidocaine membranes were vacuum-dried at room temperature before determining the swelling behavior. The samples were weighted, soaked in separate tubes containing 0.01 M phosphate buffer (pH 7.4) at room temperature (25 °C), and kept in this medium until a constant weight was attained. Before the wet membrane was weighed, the surface water was gently removed with a tissue paper. The degree of swelling of the membranes (%) was calculated as: [(Wwet − Wdry)/Wdry] × 100% where Wdry and Wwet are the weights of dried and wet samples, respectively. In Vitro Lidocaine Release. Dissolution Assays. BC-Ldc-Glyc dried membranes were placed in a vessel containing 500 mL of a 0.01 M phosphate buffer (pH 7.4) solution. The dissolution was then carried out at 32 °C and 50 rpm using a modified dissolution apparatus. At determined time intervals, 5 mL of each solution was withdrawn, and the same volume of fresh buffer solution was added to maintain a constant volume. The lidocaine content in each aliquot was determined by UV−vis at 230 nm as described below. The lidocaine content at each time was plotted as a cumulative percentage release. Six replicates were performed for each sample. In addition, the dissolution assays were also followed by NMR spectroscopy, as described below, based on the analysis of the BC membranes removed at different release times. UV−vis quantitative analysis of lidocaine was performed on a UV spectrophotometer (Evolution 600, Thermo Scientific) at 230 nm. A linear calibration curve (y = 0.010x + 0.003 (R 2 of 0.9999)) for lidocaine in the range of 1−100 μg/mL24 was obtained at 230 nm. The specificity of the method was determined through the analysis of the samples performed with BC membranes and BC membranes containing glycerol, under the same conditions of the dissolution assays. For NMR studies, samples of dry BC-Ldc-Glyc membranes (cut as rectangles of similar dimensions), fully impregnated and after 5, 10, and 40 min release in buffer solution, were packed into 4 mm diameter high-resolution magic angle spinning (HRMAS) rotors (with top inserts), and 20 μL of deuterated water (D2O) containing 0.25% TSPd4 was added. Solutions of Ldc and Ldc-Glyc were also analyzed by HRMAS. 1 H HRMAS NMR data were acquired on a Bruker Avance DRX500 spectrometer operating at 500.13 MHz for 1H observation at a temperature of 295 K and a spinning rate of 12 kHz. For acquiring 1H 1D spectra, 16 transients were collected into 16 K data points using a standard 1D pulse sequence (relaxation delay-90°-t 1-90°-tm-90°acquire FID), in which the water signal was irradiated during the relaxation delay (5 s) and the mixing period (tm = 100 ms), with T1 being a short delay of 3 μs. A spectral width of 6510 Hz and an acquisition time of 1.26 s were used. The data were processed with a line broadening of 0.3 Hz and a zero filling factor of 2, and the chemical shifts were referenced to the TSP-d4 signal at 0 ppm. 1 H spin−lattice relaxation times (T1) were measured by using the inversion−recovery sequence (180°-tr-90°-FID), where the recovery time (tr) was varied in the range 10 ms to 20 s, recording 26 experimental points. The 1 H T 1 values were calculated by monoexponential fitting of the inversion recovery curves.
be precisely defined by the area of membrane applied to the skin, and the characteristics of this system prevent any loss of drug after application. Finally, BC could represent a much more cosmetically appealing alternative than oil-based formulations, improving patient compliance. BC films could be employed in topical or transdermal drug delivery systems. Because the majority of transdermal patches are manufactured by superimposing different materials,18 a system composed of fewer or even a single layer could simplify the preparation procedure and lower production costs. 19 In recent years, we have been studying BC in different perspectives, ranging from the selection of highly productive bacterial strains, such as Gluconacetobacter sacchari,20 to the study of less expensive carbon sources for culture media21 and also as reinforcing element in transparent nanocomposites11 and in paper-coating formulations.22 In the context referred above, and considering our interest on BC, the aim of the present study was to investigate the potential of BC membranes as systems for topical or transdermal drug delivery. Lidocaine, an anesthetic drug, with high solubility in water in the form of hydrochloride (3.58 mg/mL) and commonly used in surgery20 and topical application21 was used in this study. BC-lidocaine membranes were prepared and characterized in terms of mechanical properties, structure, and morphology. Finally, the permeation through human epidermis of lidocaine in three different systems (BC, a gel and an aqueous solution) was compared to assess its therapeutic applicability and feasibility.
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EXPERIMENTAL SECTION
Materials. Lidocaine hydrochloride monohydrate and glycerol (99.5%) were purchased from Sigma Aldrich Chemical. Solvents and other reagents were of analytical grade. BC membranes (99% water content) were produced in our laboratory using the bacteria Gluconacetobacter sacchari20 and conventional culture media conditions.23 Lidonostrum (Sociedade Nostrum, Lisbon, Portugal) was used as reference topical gel. This formulation contains 2% (w/w) of lidocaine hydrochloride in a water-based gel formulation. Preparation of BC-Lidocaine Membranes. Wet 6 × 4 × 0.8 cm BC membranes (∼100 mg dry weight) were weighted, and 50% of their water mass was removed by pressure. Drained BC membranes were then soaked in 5 mL of an aqueous buffered solution (pH 7.4) of lidocaine (2%) and glycerol (1%) and shaken at 100 rpm and 30 °C for 1 h to allow the complete absorption of the solution. After the total solution absorption, the BC membranes were placed over a Petri dish and dried at 40 °C in a ventilated oven for 16 h. The dried BClidocaine membranes were kept in a desiccator until their use. The kinetics of lidocaine absorption by the membranes was determined by measuring the mass gains at different times. Control samples were also prepared by immersing BC membranes in separate buffer, glycerol, or lidocaine aqueous solutions. The identification of all samples studied is summarized in Table 1.
Table 1. Identification of All BC Membranes (100 mg) Prepared in This Work sample BC BC-Ldc BC-Glyc BC-Ldc-Glyc a
lidocaine (%)a
glycerol (%)a
solution name
1 1
Ldc Glyc Ldc-Glyc
2 2
In respect to the volume of the solution.
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1 H T2 relaxation times were measured by a Carr−Purcell− Meiboom−Gill (CPMG) sequence (90°-ts-180°-ts-FID) by varying the spin−echo time (ts) in the 5 ms to 12 s range (32 experimental points). The plots of area versus echo-time were fitted to a single exponential decay. Permeation Studies. Human abdominal skin tissue was obtained following cosmetic surgery. After removal of the adipose tissue by blunt dissection, the epidermis was separated by immersing the skin in water at 60 °C for 1 min. It was then pinned on a corkboard and the epidermis was carefully peeled away from the dermis and mounted on filter paper. It was stored in a freezer at −20 °C until required. The epidermis was cut to appropriate sizes and mounted onto glass Franz-type diffusion cells with a receptor volume of ∼4 mL and a diffusional area of 0.95 cm2. The pH 7.4 phosphate buffer saline (PBS) receptor phase was sonicated for 15 min to remove air bubbles and thus prevent the buildup of air pockets in the receptor compartment. Constant mixing of the receptor phases was achieved by inserting 2 mm magnetic bars in the receptor compartments. The diffusion cells were mounted on a magnetic stirring bed that was submerged in a water bath at 37 °C. A defined loading dose of lidocaine hydrochloride in different systems was placed in each donor compartment (Table 2). Evaporation of the donor and receptor phases was prevented by using glass coverslips and foil lids.
Figure 1. Absorption curves of the Ldc-Glyc, Ldc, Glyc, and phosphate buffer solutions into the BC membranes.
These results showed that the solution composed of glycerol and lidocaine penetrates and disperses easily into the humid BC membranes when compared with the reference solutions, which could be associated with the plasticizing effect of glycerol and also with the establishment of stronger intermolecular interactions between glycerol and lidocaine and also with the BC membrane, as will be discussed below. In fact, all BC-LdcGlyc dried membranes were very homogeneous (Figure 2),
Table 2. Lidocaine Content, Amount Applied, and Results Obtained in the Permeation Experiments lidocaine content system
% (w/w)
mg/cm2
flux (μg/cm2 h−1)
aqueous solution gel BC-Ldc-Glyc
1.9 2 50
50 4,1
47.93 ± 4.20 40.84 ± 6.18 31.35 ± 1.23
At designated time intervals, the receiver solution was withdrawn completely from the receptor compartment and immediately replaced with fresh and prethermostated PBS. Flux values were calculated by monitoring the cumulative amount of lidocaine diffused and measuring the slope of the graph once steady-state diffusion was reached. One-way ANOVA with post Hoc tests were used in this study (SPSS Statistics 17.0, IBM Corporation, Somers, NY). A 0.05 significance level was adopted.
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Figure 2. Visual aspect of BC (A) and BC-Ldc-Glyc (B) dry membranes.
RESULTS AND DISCUSSION Preparation of the BC-Ldc-Glyc Membranes. The incorporation of the lidocaine or lidocaine-glycerol (LdcGlyc) solutions into the BC membrane was performed after draining 50% of its water content aiming to guarantee their total absorption. Glycerol was added to increase the low malleability of the BC-Ldc membranes, as will be discussed below. This process enabled us to measure accurately the mass of lidocaine incorporated into the BC membranes, which was further confirmed by weighting the dry BC-Ldc membranes and by determining the total amount of drug released in the dissolution assays (by UV−vis), as will be discussed later. The absorption behavior of the solutions (Ldc-Glyc, Ldc, Glyc, and phosphate buffer) by BC membranes is shown in Figure 1. About 98% of the total volume of the Ldc-Glyc solutions was absorbed after 20 min of immersion of the BC membranes for BC-Ldc-Glyc sample. In this way, the lidocaine content of the BC loaded membranes, prepared under the conditions referred above, was 4.1 mg/cm2 of 0.8 cm thick membranes. For reference samples, with only glycerol or lidocaine, the absorption of the corresponding solutions was >90% for 40 min of immersion of the BC membranes. However, only 80% of the phosphate buffer solution volume was absorbed after 40 min.
indicating a good dispersion of Ldc-Glyc solution inside the BC nano and microfibrills network, whereas BC-Ldc or BC-Glyc showed some heterogeneity. In summary, BC-Ldc-Glyc membranes were prepared through a simple, rapid, and effective method, constituting an advantage of this type of systems. Characterization of the BC-Ldc-Glyc Membranes (Structure, Morphology, Mechanical, and Swelling Properties). FTIR-ATR analysis was carried out to study the main structural features of these drug delivery systems. The spectrum of BC, lidocaine powder, glycerol, and BC-Ldc-Glyc membrane are displayed in Figure 3a. BC membranes showed typical FTIR spectra of cellulosic substrates,25 with strong bands at around 3300, 2880, and 1100 cm−1, associated with the vibrations of the OH, C−H, and C− O−C groups, respectively. The spectrum of glycerol presented a broad absorption band associated with the hydroxyl groups at 3250 cm−1 and the C−O absorptions characteristic of primary and secondary alcohols occurring at 1030 and 1100 cm−1, respectively.26 The FTIR spectrum of lidocaine showed several peaks, namely, at ∼3250 cm−1, associated with the N−H bonds of secondary amide at ∼1550 cm−1 related to aromatic CC 4164
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Figure 3. (a) FTIR-ATR spectra of BC membrane, lidocaine powder, glycerol, and BC-Ldc-Glyc membrane. (b) 500 MHz 1H HRMAS NMR spectra of Ldc solution (top), Ldc-Glyc solution (middle), and BC-Ldc-Glyc membrane (bottom). All spectra are calibrated to the TSP signal at 0 ppm. The assignment of Ldc protons is indicated through letters a−e.
bonds and at ∼1650 cm−1 associated with the CO bonds of the amide groups.27 In general, the FTIR spectra of the BC-Ldc-Glyc membranes are a perfect sum of the spectra of individual components. No novel peaks were observed; however, some were slightly shifted probably because of the establishment of intermolecular interactions, like hydrogen bonding, between lidocaine, glycerol, and cellulose. These observations support the higher absorption of Ldc-Glyc solution by the BC membranes and their higher homogeneity, as discussed above. These assumptions are further supported by the NMR results, as
the 1H 1D spectra recorded for the solutions of Ldc and LdcGlyc and for the BC membrane fully impregnated with LdcGlyc which shows clear shifts in the resonances of Ldc protons (Figure 3b). In particular, Ldc proton resonances were shifted to higher frequencies in the BC-Ldc-Glyc membrane spectrum compared with Ldc and Ldc-Glyc, probably reflecting interactions within Ldc molecules and between these and the BC membrane. According to the magnitude of these shifts, the CO−CH2−N protons were the most affected (0.055 ppm shift), probably due to their proximity to groups involved in hydrogen bonding with BC protons, whereas the other signals 4165
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The water absorption by pure BC is due to its chemical and physical structure. BC is a high hydrophilic material, that is, with a high affinity to water and other polar molecules,7 and its 3D network with large amount of pores, maintained after drying, make possible to generate a capillary force within the network that move forward the molecules of water.28 However, the collapse of the tridimensional network and the resulting strong hydrogen bonding between nanofibers limits the extent of rehydratation, that is, the water uptake to maximum values of ∼50%.29 A similar value was observed in this study (Figure 5).
showed similar downfield shifts (0.026 to 0.031 ppm), except for the aromatic ring proton resonances, which did not shift. Additionally, glycerol signals were shifted by a similar magnitude in the BC-Ldc-Glyc membrane relatively to the Ldc-Glyc solution, reflecting BC−glycerol interactions. Also of note is the broadening of Ldc resonances in the membrane spectrum, reflecting, as expected, the lower mobility of Ldc molecules when inserted into the BC matrix. These observations also support the existence of relevant interactions among BC, Lcd, and Glyc, as already evidenced by FTIR and consequently their influence on the absorption and release behavior of Ldc. The surface morphology of the BC membranes was assessed by SEM (Figure 4). The micrographs of BC-Ldc-Glyc showed
Figure 4. SEM images of BC and BC-Ldc-Glyc dry membranes surface. Figure 5. Swelling behavior of BC, BC-Ldc-Glyc, BC-Ldc, and BCGlyc membranes.
the characteristic tridimensional fibrillar network of BC and the absence of aggregates formation, which indicated that no precipitation of lidocaine occurred during the processing of the membranes, most certainly due to solubilization of Ldc in the glycerol phase. In addition, these images provided further evidence of the good dispersion of both lidocaine and glycerol into the BC matrices. The incorporation of lidocaine into the BC network increased considerably the hardness of the membranes, and the materials became brittle, as demonstrated by the large decrease in elongation at break (Table 3) and the
The BC-Ldc-Glyc membranes showed an increased swelling capacity comparatively to their pure BC counterparts certainly due to the presence of glycerol and lidocaine that on the one hand due to the plasticizing role of glycerol had limited the extent of the collapse of the tridimensional structure, facilitating the reabsorption of water, and, on the other hand, were also highly hydrophilic favoring the penetration and imprisonment of the water molecules between the cellulose chains. In fact, both BC-Ldc and BC-Glyc membranes presented also higher water uptakes than the unloaded BC membranes. This increased water absorption is very important for absorption of exudates if the BC-Ldc-Glyc membranes are used as woundhealing membranes. Dissolution Assays. The release profile of lidocaine from BC-Ldc-Glyc membranes in a phosphate buffer solution (pH 7.4) at 32 °C showed that 60% of total drug was liberated in the first 10 min and >90% after 20 min (Figure 6). Because lidocaine was already solubilized in the glycerol media (as discussed above) and both components are highly watersoluble, the lidocaine release from the BC membranes was essentially governed by its diffusion throughout the polymeric porous and tridimensional matrix. Therefore, under these conditions, the diffusion of the dissolved lidocaine molecules to the liquid environment was highly dependent on the swellability of the BC matrix, previously demonstrated. Globally however, maximum release was obtained at the end of ∼40 min. To investigate the dynamics of the BC-Ldc-Glyc systems upon drug release, we performed NMR relaxation measurements, and the results are shown in Figure 7. The spin−lattice or longitudinal relaxation time (T1) is affected by rapid molecular motions with frequencies on the order of hundreds of megahertz, such as fast rotation of individual groups, for
Table 3. Young Modulus, Tensile Strength and Elongation at Break of BC, BC-Ldc-Glyc, BC-Ldc, and BC-Glyc Membranes, Obtained from Tensile Essays sample BC BC-Ldc BC-Gly BC-LdcGlyc
E modulus (MPa) 3621.15 3949.98 1720.07 1840.11
± ± ± ±
108.6 118.5 51.6 55.2
elongation at break (%) 5.40 2.01 7.47 7.01
± ± ± ±
0.38 0.14 0.52 0.49
tensile strength (MPa) 172.98 190.12 115.60 129.97
± ± ± ±
8.65 9.5 5.78 6.49
corresponding increase in Young modulus and tensile strength. This drawback was overcome by the use of glycerol as plasticizer. The plasticizer molecules are retained between the cellulose nanofibers, separating them and reducing the intermolecular attraction forces, therefore increasing the mobility of the fibers and thus the flexibility of the material. The addition of glycerol to the BC-Ldc membranes increased considerable their malleability, as observed by the increment on the elongation at break and by the corresponding decrease in the Young modulus (Table 3). This aspect is quite important in terms of the clinical application of the membranes because flexible-type materials are easier to manipulate and to fix. 4166
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an increase from 0 to 5 min and then a trend to decrease from 5 to 10 min, with no significant differences found between 10 and 40 min samples (Figure 7). These results suggest an increase in the mobility of Ldc protons from 0 to 5 min release, probably reflecting the less tight packing of Ldc molecules in the BC matrix. As the dissolution progresses and Ldc molecules with weaker interactions with the membrane are released, the contribution to the average relaxation times from Ldc molecules with stronger interactions with the BC matrix becomes more pronounced, thus resulting in the decrease in T1 and T2 values. These results support the hypothesis of intra- and intermolecular interactions between Ldc and the BC-Glyc matrix. In Vitro Permeation Studies. Diffusion profiles of the permeation of lidocaine through human epidermis in each formulation are shown in Figure 8. It can be seen that steady-
Figure 6. Dissolution profile of lidocaine from BC-Ldc-Glyc membranes.
Figure 8. Lidocaine permeation profiles from aqueous solution (1.9% w/v) (▲) from 2% (w/w) topical gel (□) and BC (○) across human epidermis. Mean values ± standard deviation, n = 5.
state was quickly reached in all cases, and the permeation profile of the drug in BC membranes was analogous to that obtained with the conventional systems (e.g., aqueous solution and gel). Depending on the formulation system, different flux values were obtained, as seen in Table 3. The highest lidocaine fluxes were obtained in the aqueous solution and the lowest lidocaine fluxes were obtained observed in the BC. There were no statistically significant differences between the results obtained with the gel and with the aqueous solution. However, the average flux values of lidocaine in BC were significantly lower than those obtained with the other two formulations. The permeation profiles were obtained with lidocaine applied in different amounts per unit area, which could partially explain the variations observed in fluxes. Conflicting reports can be found in the literature, describing the effect of dose level on drug permeation through skin,30 and even though some studies have shown poor correlations between drug concentration and flux31 or even bioequivalence between topicals with different drug concentrations,32 it is recommended that similar dose levels are used in comparative studies.33 Additionally, such results can be attributed to differences in the resistance opposed by the formulations to the diffusion of the drug, which will appreciably influence the drug release. This effect is negligible in the aqueous solution but should be more
Figure 7. Average relaxation times (a) T1 and (b) T2 of Ldc protons obtained for duplicate samples (prepared in independent dissolution assays) of a Ldc-Glyc solution and BC-Ldc-Glyc membranes at different times of Ldc release. The error bars correspond to standard deviations. The relatively larger error bars for the BC sample after 40 min of release relate to the low signal-to-noise of the spectra recorded, as the amount of Ldc in this sample was residual.
example, methyl groups, whereas the spin−spin or transverse relaxation time (T2) is not only affected by these motions but also depends on lower frequency processes such as chain backbone motions and hindered group rotations. Compared with the Ldc-Glyc solution, Ldc protons in the BC-Ldc-Glyc membranes presented markedly shorter T1 and T2 values (Figure 7), which is consistent with the restricted mobility of Ldc protons, in agreement with the observed broadening of their signals in the 1D spectra (Figure 3b). Regarding the comparison of BC-Ldc-Glyc membranes collected at different times of the release assay (0, 5, 10, and 40 min), T1 and T2 values for the different Ldc protons showed 4167
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(17) Bodhibukkana, C.; Srichana, T.; Kaewnopparat, S.; Tangthong, N.; Bouking, P.; Martin, G. P.; Suedee, R. J. Controlled Release 2006, 113, 43−56. (18) Delgado-Charro, M. B.; Guy, R. H. STP Pharma Sci. 2001, 11, 403−414. (19) Padula, C.; Colombo, G.; Nicoli, S.; Catellani, P. L.; Massimo, G.; Santi, P. J. Controlled Release 2003, 88, 277−285. (20) Trovatti, E.; Serafim, L. S.; Freire, C. S. R.; Silvestre, A. J. D.; Neto, C. P. Carbohydr. Polym. 2011, 86, 1417−1420. (21) Carreira, P. M.; J.A., S.; Trovatti, E.; Serafim, L. S.; Freire, C. S. R.; Silvestre, A. J. D.; Neto, C. P. Bioresour. Technol. 2011, 102, 7354− 7360. (22) Pascoal Neto, C.; Da Rocha Freire Barros, C. S.; De Matos Fernandes, S. C.; Domingues Silvestre, A. J.; Gandini, A. Aqueous Coating Compositions for Use in Surface Treatment of Cellulosic Substrates. Patent No. WO/2011/012934,2011. (23) Hestrin, S.; Schramm, M. Biochem. J. 1954, 58, 345−352. (24) Yuan, J. S.; Ansari, M.; Samaan, M.; Acosta, E. J. Int. J. Pharm. 2008, 349, 130−143. (25) El-Saied, H.; El-Diwany, A. I.; Basta, A. H.; Atwa, N. A.; ElGhwas, D. E. Bioresources 2008, 3, 1196−1217. (26) Medeiros, M. D.; Rezende, J. D.; Araujo, M. H.; Lago, R. M. Polimeros 2010, 20, 188−193. (27) Fraceto, L. F.; Pinto, L. D. A.; Franzoni, L.; Braga, A. A. C.; Spisni, A.; Schreier, S.; de Paula, E. Biophys. Chem. 2002, 99, 229−243. (28) Iguchi, M.; Yamanaka, S.; Budhiono, A. J. Mater. Sci. 2000, 35, 261−270. (29) Clasen, C.; Sultanova, B.; Wilhelms, T.; Heisig, P.; Kulicke, W. M. Macromol. Symp. 2006, 244, 48−58. (30) Brain, K.; Walters, K. A.; Watkinson, A. C. Methods for Studying Percutaneous Absorption. In Dermatological and Transdermal Formulations; Walters, K. A., Ed.; M. Dekker: New York, 2002; pp 197−269. (31) Akhter, S. A.; Barry, B. W. J. Pharm. Pharmacol. 1985, 37, 27− 37. (32) Peltonen, L.; Solberg, V. M. Curr. Ther. Res. Clin. Exp. 1984, 35, 78−82. (33) Basic Criteria for the in Vitro Assessment of Dermal Absorption of Cosmetic Ingredients; SCCS/1358/10; SCCS (Scientific Committee on Consumer Safety): Brussels, 2010. (34) A-sasutjarit, R.; Sirivat, A.; Vayumhasuwan, P. Pharm. Res. 2005, 22, 2134−2140. (35) Di Colo, G.; Carelli, V.; Giannaccini, B.; Serafini, M. F.; Bottari, F. J. Pharm. Sci. 1980, 69, 387−391.
significant in the gel (HPMC). The effect of gel viscosity on drug release is well-known,34,35 and most studies have found inverse relationships between the viscosity of preparations and drug diffusion coefficients. BC membranes have a complex tridimensional structure, which makes the diffusion pathway of the drug tortuous and results in a global decrease in the drug release rate.
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CONCLUSIONS
BC-lidocaine membranes were prepared through a simple and efficient approach. The morphological structure of the BC membranes was not affected by the presence of lidocaine and glycerol because no significant differences were detected by the characterization techniques applied. The loaded membranes presented a doubled swelling capacity when compared with the pure BC membranes. The permeation rate of lidocaine in BC membranes was lower than that obtained with the conventional delivery systems (e.g., aqueous solutions and gels), suggesting that this technology can be applied to modulate the bioavailability of lidocaine for topical administration with the advantage of the easy application in mucosa and epidermis.
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AUTHOR INFORMATION Corresponding Author *E-mail:
[email protected]. Tel: +351 234 370 604. Fax: +351 234 370 084.
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ACKNOWLEDGMENTS E.T. is grateful to FCT (Fundaçaõ para a Ciência e Tecnologia) and POPH/FSE for Grant SFRH/BPD/63250/2009.
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REFERENCES
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dx.doi.org/10.1021/bm201303r | Biomacromolecules 2011, 12, 4162−4168
