DESIGN OF SOME TOPICAL DELIVERY SYSTEMS WITH LIDOCAINE BASED ON COLLAGEN FOR WOUND TREATMENT

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1 DESIGN OF SOME TOPICAL DELIVERY SYSTEMS WITH LIDOCAINE BASED ON COLLAGEN FOR WOUND TREATMENT MIHAELA VIOLETA GHICA 1, MADALINA GEORGIANA ALBU 2, LACRAMIOARA POPA 1 1 Physical-Chemistry and Colloids Department, Faculty of Pharmacy, Carol Davila University of Medicine and Pharmacy, 1-6, Traian Vuia, 2956, Bucharest, Romania, mihaelaghica@yahoo.com 2 Collagen Department, Leather and Footwear Research Institute, 93, Ion Minulescu, 31215, Bucharest, Romania, albu_mada@yahoo.com For the acute or chronic wounds, the associated pain is an important aspect that has to be considered in the management of their therapy. Among the local anesthetics, the lidocaine proved its efficiency for topical application, in different aetiology pains. Collagen, a well tolerated biomaterial and biodegradable, represents a favorable matrix for the drugs release. In this study some collagen hydrogels different cross-linked with lidocaine were developed, according to a 32 factorial design. The lidocaine in vitro release from the hydrogels was determined using a modified Franz diffusion cell. For establishing the mechanism of the lidocaine release from hydrogel different kinetic models were used. The formulations were also characterized from their rheological properties. Rheological measurements were performed using a rotational viscometer. The flow behaviour was quantified through different rheological models. The designed topical systems presented a thinning through shearing behaviour. Quantitative relations were built between the rheological parameters with biopharmaceutical implications and the lidocaine release kinetic characteristics. Keywords: collagen hydrogels, lidocaine, quantitative relation rheology-kinetic. INTRODUCTION The untreated pain can have a negative impact on the wounds healing rate both for acute wounds (burns) and for the chronic wounds (decubitis ulcers: bedsores or pressure sores; leg ulcer: venous, ischaemic or of traumatic origin). For the amelioration of the local pains associated to different ethiology wounds, the local anaesthetics have been widely used. Among them we selected for the present study the lidocaine hydrochloride as drug model. Between many drug delivery systems, the percutaneous drug delivery was widely used as advanced drug delivery system, being a successfull alternative for the oral or parenteral administration way due to their advantages (Ricci et al., 25, Shin et al., 24, Pathak and Nagarsenker, 29). The local anaesthetics treatment is supposing the existence of an adequate support for their topical release, currently the semisolid systems based on biodegradable natural polymers being widely used. Among them a special attention is granted to the collagen, a biomaterial perceived by the human body as one of its constituents and not a foreign material. The excellent biocompatibility and the safety dues to its biologic features, as biodegradability and low antigenicity transformed the collagen in the main ressource for the medical applications. The collagenic hydrogels properties are very important for the pharmaceutical applications, the cross-linking degree modification conferring the desired mechanical properties (Titorencu et al., 21, Ghica et al., 29). The purpose of this paper was thereby the study of the lidocaine release from certain collagenic hydrogels evidenciating the delivery mechanism of the drug from the designed hydrogels and of its availability for the cutaneous absorption. The kinetic analysis is complemented with the study of the flow properties that can give us useful 193

2 informations concerning the analyzed hydrogels behaviour at the application site (suitable consistency and a sufficient apparent plasticity). The hydrogels rheological properties can determine the release kinetic of a drug from the gel as well as the stasis time at the application site. The relationships kinetic-rheology can be useful for the determination of the release parameters of lidocaine from other collagen hydrogels, containing different amounts of collagen or glutaraldehyde (Diez-Sales et al., 25). MATERIALS AND METHODS Materials The following materials were used: type I fibrillar collagen gel having a concentration of 1.71% (w/w) extracted from calf hide by the currently used technology in the Leather and Footwear Research Institute, Collagen Department (Albu, 29), lidocaine obtained from Sigma-Aldrich and glutaraldehyde (GA) purchased from Merck (Germany). Sodium hydroxide and phosphate buffer solution were of analytical grade. Preparation of Collagen Hydrogels Hydrogels were prepared according to the 3 2 Mitchell and Bayne factorial fractional design (Lewis et al., 1997). The formulation factors: collagen concentration (X 1 ) and glutaraldehyde concentration (X 2 ) are mentioned under the coded form in Table 1. The physical variation levels for these formulation variables are mentioned in Table 2. The lidocaine concentration was.1% for each sample. Each hydrogel was adjusted at ph = 7.2 with 1M sodium hydroxide under mechanical stirring. The neutral hydrogels were cross-linked with,.25 or.5% GA reported at collagen gel and then stored for 24h at 4 C for maturation and/or cross-linking processes. The lidocaine was incorporated as lidocaine hydrochloride. Table 1. Mitchell and Bayne experimental design Hydrogels Collagen GA (X 1 ) (X 2 ) G G G G G-5 +1 G-6 +1 G-7 Table 2. Physical variation levels for the formulation factors Formulation Physical variation levels factors Collagen % (X 1 ) GA % ( X 2 )

3 In vitro Lidocaine Release Study Lidocaine in vitro kinetic release was performed using a modified Franz diffusion cell fitted with a standard cellophane membrane. The phosphate buffer with ph 7.4 was used as receiving medium and maintained at 37 C, temperature for which the kinetic experiments were performed. The receptor solution was continuosly stirred by a rotating teflon coated magnet placed inside the cell and an additional stirring were performed by a peristaltic pump. The amount of lidocaine released at certain time periods was spectrophotometrically evaluated at 263 nm (Albu et al., 29). Rheological Analysis The rheological properties of the designed gels were studied using a rotational viscometer Multi-visc Rheometer-Fungilab equipped with standard spindles and an ultrathermostat ThermoHaake P5. The rheological experiments were performed at 37±.5 C. RESULTS AND DISCUSSION The experimental kinetic data obtained served for the determination of the release mechanism for the lidocaine hydrochloride from the topical systems designed. Various kinetic models with different determination coefficient R 2 (Albu et al., 29, Ghica et al., 29) were verified. Comparing R 2 values we can observed that the lidocaine release follows the Higuchi model (equation 1), proving that this model describes the best the drug release mechanism from hydrogels, the fickian diffusion (the diffusion rate of the drug is much less than the polymer relaxation rate): m t = k t (1) m where, m t is the amount of drug released at time t, m is the total drug contents in the designed collagen hydrogels, m t /m represents the fractional release of the drug and k is the kinetic constant. In order to determine the effect of the formulation factors (collagen and glutaraldehyde) on drug amount delivered from the hydrogels, the release kinetic of the lidocaine was quantified through parameters specific to Higuchi model, namely the diffusion coefficient (equation 2) and time lag: 2 q π D = (2) 4 C t 2 where, q is the amount of drug release per membrane unit area, C is the initial drug concentration in the donor medium, D is the diffusion coefficient of the drug and t is the drug release time. If the rate of drug release obeys this law, the amount of drug release is a linear function of the t 1/2, and D can be calculated from the slope (Ricci et al, 25). The time lag, defined as initial period preceeding the appearance of the drug in the receiving medium (corresponding to the settlement of a diffusion gradient), is determined from the regression line q 2 depending on time. The values of the kinetic parameters previousely mentioned are given in Table 3: 195

4 Table 3. Kinetic parameters specific for Higuchi model Hydrogels Diffusion coefficient (D) D 1 +8 (cm 2 /s) Time lag (T lag ) (min) G G G G G G G Analyzing the data mentioned in Table 3 we can observe the combined effect of the two formulation factors on the lidocaine release from the topical formulations tested. The increase both of the collagen and the cross-linking agent concentration determines the drug diffusion coefficient decrease and the time lag increase. We can also observe that hydrogels with a smaller gelifying polymer concentration buth with a superior glutaraldehyde concentration can present smaller values of the diffusion coefficient, respectively superior time lag compared to hydrogels formulated with a higher collagen quantity, but smaller cross-linking agent (e.g.: hydrogel 2 compared to hydrogel 6) due to the different physical or chemical bindings that can occur in the system. The designed hydrogels were also tested from the rheological point of view. The experimental data obtained verified the Herschel Bulkley model (equation 3): τ τ K γ n = + & (3) where, τ is the shear stress (Pa), γ& is the shear rate (s -1 ), τ is the yield stress (Pa), K is the consistency index (Pa s n ) and n is the flow index (Albu at al, 29). In Table 4 the values of the rheological parameters specific to this model are given as well as the values of the viscosity recorded at the rotational speed of.3 rpm. Table 4. The values of the rheological parameters specific to Herschel-Bulkley model and the viscosity at minimum rotation speed Hydrogels Yield stress (τ ) (Pa) Consistency index (K) (Pa s n ) Flow index (n) Viscosity at.3 rpm (η.3 ) (Pa s) G G G G G G G The values of the flow index n being less than unity for all hydrogels we can observe a pseudoplastic and shear thinning behaviour which facilitated the formulations flow. The rheograms shear stress as function of shear rate corresponding to the crosslinked and uncross-linked collagenic gels are presented in Figure

5 Share stress, Pa Share rate, s -1 Figure 1. Rheological profiles for hydrogels 1-7 The cumulated effect of the formulation factors is reflected both on the lidocaine release profiles from topical semisolids and on the rheological characteristics of these pharmaceutical systems. For this purpose, the setting of the quantitative relationships kinetic rheology (equations 4-7) was based on some rheological parameters with biopharmaceutical implications that describe a certain lidocaine release kinetic profile. The rheological characteristics considered were: the yield stress (important both from the point of view of skin spreading and forming a continous film at the application site and also from the point of view of adequate conditioning) and the viscosity at.3 rpm (the viscosity for which the diffusion of the drug is considered to be realized yet at significant values, similar to the physiological conditions). The kinetic parameters taken into account were: the diffusion coefficient of lidocaine and the time lag. D = f( τ ) = τ (R =.9781) (4) D = f( η.3 ) = 4.13 η.3 (R =.9919) (5).515 T lag = f( τ ) = τ (R =.987) (6) T lag = f( η.3 ) = η.3 (R =.985) (7) In order to show their predictive power, the theoretical models kinetics-rheology were also applied to the other two hydrogels not belonging to the initial fractional experimental matrix. The two systems coded under the name of hydrogel 8 and hydrogel 9 contain.9% collagen and.25% GA, 1.2% collagen and % GA respectively, as well as the same quantity of lidocaine hydrochloride. The two hydrogels were also rheologically analyzed in the same conditions (G8: τ = 1.911Pa, η.3 = 27.7Pa s; G9: τ = 2.442Pa, η.3 = 31.5Pa s). The predictive values of the kinetic parameters obtained following the application of the equations (4)-(7) as well as the experimental values are mentioned in Table

6 Table 5. Predicted and experimental kinetic values for the hydrogel 8 and hydrogel 9 Kineticsrheology Hydrogel 8 Hydrogel 9 model Theoretical values Experimental value Theoretical values Experimental value D = f(τ ) D = f(η.3 ) T lag = f(τ ) T lag = f(η.3 ) We can observe a good correspondence between the theoretical values and the experimental observed values for the kinetic parameters. CONCLUSIONS In this work collagen-lidocaine hydrogels cross-linked or uncross-linked were formulated and its kinetic and rheological studies were carrried out. All the hydrogels have a non-newtonian pseudoplastic behaviour with yield stress. The lidocaine release follows the Higuchi model and the diffusion coeficients are strongly influenced by the collagen and glutaraldehyde concentrations. By modulation of the two formulation factors concentration we can design delivery systems with kinetic and rheologic properties adequate to the drug release in the management of the pains associated to the treatment of the different causes wounds. The quantitative relations kinetic parameters and rheological properties proved a high predictive power and are useful because they can be applied to other systems not belonging to the initial experimental matrices. Acknowledgements This work was supported by CNCSIS UEFISCSU, project number PNII RU code 149/21. REFERENCES Albu, M.G. (29), Collagen Gels and Matrices with Different Hydration Degrees and Cvasisolid Structure for Biomedical Applications, Doctoral Thesis, University of Bucharest. Albu, M.G., Ghica, M.V., Popa, L. et al. (29), Kinetics of in vitro Release of Doxycycline Hyclate from Collagen Hydrogels, Revue Roumaine de Chimie, 54(52), Diez-Sales, O., Garrigues, T.M., Herraez, J.V. et al. (25), In vitro Percutaneous Penetration of Acyclovir from Solvent Systems and Carbopol 971-P Hydrogels: Influence of Propylene Glycol, Journal of Pharmacy Science, 94(5), Ghica, M.V., Albu, M.G., Popa, L. et al. (29), Drug Delivery Systems Based on Collagen-Tannic Acid Matrices, Revue Roumaine de Chimie, 54(11-12), Lewis, G.A., Mathieu, D., Phan-Tan-Luu, R. (1997), Pharmaceutical Experimental Design, Marcel Dekker Inc., New York. Pathak, P. and Nagarsenker, M. (29), Formulation and Evaluation of Lidocaine Lipid Nanosystems for Dermal Delivery, AAPS Pharmacy Science and Technology, 1(3), Ricci, E.J., Lunardi, L.O., Nanclares, D.M.A. et al. (25), Sustained Release of Lidocaine from Polaxamer 47 Gels, International Journal of Pharmacy, 288(2), Shin, S.C., Cho, C.W. and Yang, K.H. (24) Development of Lidocaine Gels for Enhanced Local Anesthetic Action, International Journal of Pharmacy, 287(1-2), Titorencu, I., Albu, M.G., Giurginca, M. et al. (21), In vitro Biocompatibility of Human Endothelial Cells with Collagen-Doxycycline Matrices, Molecular Crystals and Liquid Crystals, 523,