Cross Linked Chitosan in Situ Gel of Satranidazole for Intra Periodontal Drug Delivery

This paper introduces a novel type of injectable temperature-sensitive chitosan polymer based in situ gel for the local delivery of Satranidazole into the infected periodontal pocket. The thermo gelling polymer, chitosan with different concentrations has been used for formulation of in situ gel of Satranidazole with 10 % propylene glycol as plasticizer and was allowed to cross linked with 1 % solution of glutaraldehyde for extended release. The FTIR studies and the XRD studies confirmed the absence of chemical interaction between the drug and the polymer. The developed formulations were evaluated for various parameters like surface pH, gelation temperature, drug content, spreadability, viscosity, in vitro drug release and in vitro antibacterial activity, SEM and stability studies. The optimized formulation G6 in terms of cumulative percent drug release along with zero order kinetic mechanism with 98.6 % drug release for 5 days and fulfilled many requirements of once a week delivery system. Throughout the permeation study, the average permeation rate for in situ gel was found to be above the minimum inhibitory concentration of Satranidazole indicating the suitability of formulating Satranidazole as a controlled release local delivery in situ gel for longer periods of time. Histopathological and microscopic study of the periodontal mucosa after permeation study suggested that the gel formulations were safe for local anti microbial treatment in to the infected periodontal pocket. The in vitro antibacterial activity demonstrated a significant antibacterial profile of the in situ gel G6 formulation against Porphyromonas gingivalis. The SEM of in situ gel suggesting that the drug(s) were dispersed rather than dissolved in the polymer matrix. The stability studies confirmed that the in situ gel formulation of Satranidazole remained stable at room temperature (30 ± 2°C) and refrigerator temperature (4 ± 2°C). Keyword: Injectable system, Periodontal pocket, local delivery, bio adhesive polymer. INTRODUCTION The bacteria that cause periodontal gum disease will be eliminated or inhibited through the use of antimicrobial therapy. The aim of current periodontal therapy is to remove the bacterial deposits from the tooth surface and to shift the pathogenic micro biota to one compatible with periodontal health. The periodontal mucosa has been considered as a potential administration route to achieve faster and higher level of drug absorption. The periodontal cavity offers a number of unique advantages such as easy accessibility, good permeability especially for lipophilic, low molecular weight drugs, avoidance of harsh environmental conditions and hepatic first pass metabolism. The use of bio adhesive polymers can lengthen the residence time and enhance bioavailability of drugs delivered to the periodontal cavity. Success of any drug system designed to target periodontal infection depends upon its ability to deliver the anti microbial agent to the base of pocket at a bacteriostatic or bactericidal concentration. It must also facilitate retention of medicament long enough to ensure an efficacious result. Local applications (as mouth rinse, gels, tooth paste etc,) control only supra gingival microbial plaque or periodontal disease involving pocket formation and also requires high initial concentrations and multiple applications in order to provide sustained effectiveness. Local application of antibiotics has been achieved either by sub gingival irrigation or by incorporating the drug into different devices for insertion into periodontal pockets. Sub gingival irrigation of antimicrobial involves local drug delivery but not controlled release. Injectable systems are particularly attractive for the delivery of drug into the periodontal pocket. This application can be easily and rapidly carried out, without pain and using a syringe. The chitosan has favourable biological properties such as biodegradability and biocompatibility which has attracted a lot of attention in the pharmaceutical and medical fields and an attractive material for multiple applications. Blending of chitosan with other polymers and cross linking are both convenient and effective methods of improving the physical and mechanical properties of chitosan for practical applications. Immunization studies carried out on rats using glutaraldehyde cross linked chitosan spheres showed promising tolerance by the living tissues of the rat muscles. The drug Satranidazole exhibits its anti bacterial effect by extensive DNA damage characterized by helix destabilization and strand breakage. The MIC90 of Satranidazole against 50 clinical isolates of anaerobes was 0.25 mg/l which was fourfold lower than the MIC90 of metronidazole, tinidazole and ornidazole (MIC90 = 1.0 mg/l). It is a highly potent; well tolerated. It is rapidly absorbed and exhibits higher plasma and liver concentration than metronidazole. So in the present research work, an attempt has made to formulate in situ gel of Satranidazole using a natural polymer, chitosan for the effective management of periodontitis with local delivery into the infected periodontal pockets. MATERIALS AND METHODS SZ was obtained as a kind gift sample from Alkem Laboratory, Mumbai, India, and Chitosan from Central Institute of Fisheries Technology, Cochin, India. All other chemicals used in this study are of analytical reagent grade. Revathy V Nair et al. Int. Res. J. Pharm. 2014, 5 (5) Page 385 The drug was characterized for various pre formulation studies. Pre formulation Studies Drug solubility studies The solubility of Satranidazole in a variety of solvents was carried. Excess amount of drug (100 mg) was added to 10 mL of various solvents. The dispersions were shaken in a thermostatically controlled water bath shaker at 37 + 0.5C until equilibrium (48 h). Afterward, samples were withdrawn, filtered through a 0.45 μm membrane filter and suitably diluted. Drug concentration was analyzed and the solubility of the drug in different solvents after suitable dilution, absorbance of solution was measured at 319 nm by using UV visible spectrophotometer. Fourier transform infrared spectroscopy (FT-IR) FTIR spectra of pure drug, chitosan and the physical mixture (SZ + Chitosan) were obtained using KBr pellet method (applying 6000 kg/cm). Spectral measurements were obtained by powder diffuse reflectance on a FTIR spectrophotometer (Shimadzu, USA). Each spectrum was recorded in the frequency range of 4000-450 X-ray diffractometry The X-ray diffractograms of Satranidazole, Chitosan and the Physical mixture (SZ + Chitosan) were recorded by using a Shimadzu XD-5 Diffractometer with tube anode Cu over the interval 4-40/2θ. Preparation of in situ Gels In the present study six batches of Satranidazole cross linked in situ gels were prepared using natural biodegradable polymer, Chitosan in variable concentrations using glutaraldehyde as a cross linking agent. First, appropriate concentrations of polymer solutions (0.5, 1, 1.5, 2, 2.5 and 3 %) were prepared by dissolving chitosan in 1 % dil acetic acid into a glass vial. The vial was placed on a continuous shaker overnight at room temperature to completely dissolve the polymer. Then, 10 % v/v propylene glycol as plasticizer was added into the polymer solution and mixed together. 1 % w/w of drug Satranidazole was added to the drug-free formulation. All formulations were clear, homogeneous solutions at room temperature. To get cross linked in situ gel of chitosan, preparation containing SZ were allowed to cross linked with 1 % aqueous solution of glutaraldehyde. The mixture was stirred for 30 min at room temperature until it became increasingly viscous. The viscous solution was left at room temperature to remove bubble. Typical composition showed in Table 1. Evaluation of in situ Gels The developed formulations were evaluated for various parameters like pH, gelation temperature, drug content, bio adhesive strength, viscosity, in vitro drug release and permeation studies, mucosa deposition studies, histopathology, in vitro antibacterial activities and finally stability studies. Measurement of Gelation Temperature A 2 ml aliquot of gel was transferred to a test tube, immersed in a water bath. The temperature of water bath was increased slowly and left to equilibrate for 5 minutes at each new setting. The sample was then examined for gelation, which was said to have occurred when the meniscus would no longer moves upon tilting through 90. Surface pH An acidic or alkaline formulation is bound to cause irritation on mucosal membrane and hence this parameter assumes significance while developing a mucoadhesive formulation. The surface pH was determined by the method similar to Bottenburg et al. A digital glass electrode pH meter was used for this purpose. pH was noted by bringing the electrode near the surface of the formulations and allowing it to equilibrate for 1 minute. Viscosity Study Viscosity of gels was studied on Brookfield viscometer by using spindle number 3 at 60 revolution per minute (RPMS) at constant temperature. Spreadability The spreadability of the gel formulations was determined 48h after preparation, by measuring the spreading diameter of 1 g of the gel between two glass plates after 1 minute. The mass of the upper plate was standardized at 125 g. The spreadability was calculated by using the formula S = m. l/t, where S is spreadability, m is the weight tied to the upper slide, l is the length of the glass slide, and t is the time taken. Homogeneity of gel formulation was tested by visual observations. Drug Content 1 ml of formulation was taken in 10 ml volumetric flask, diluted with 1 % dil. acetic acid and volume adjusted to 10 ml. Finally the absorbance of prepared solution was measured at 319 nm by using UV visible spectrophotometer (Shimadzu UV). Concentrations of drug were calculated from the standard calibration curve prepared in 1 % dilute acetic acid. Viscosity Measurement The viscosity of the prepared gels was measured using a Brookfield at a controlled temperature of 25 ± 2° at 50 rpm. In vitro Drug Release Studies A cellophane membrane (cut to suitable size) boiled in distilled water for 1 hour, soaked in absolute alcohol for half an hour and stored in phosphate buffer pH 6.6 for 24 hours before use. A glass cylinder with both ends open, 10 cm height, 3.7 cm outer diameter and 3.1 cm inner diameter cellophane. Membrane was tied to one end of donor compartment. Gel was accurately weighed, was taken in one cell (donor compartment) and the cell was immersed in a beaker containing 30 ml of phosphate buffer (receptor compartment) of pH 6.6 were used for study. The cell was immersed to a depth of 1 cm below the surface of phosphate buffer in the receptor compartment, and temperature maintained at 37 ± 1°C throughout the study. A static dissolution set up was created. Aliquots of 5 ml were withdrawn periodically at intervals of 1 day for a period of 5 days and each time equal volume was replaced with fresh phosphate buffer previously heated to 37 ± 1°C. The amount of drug release was estimated using UV spectrophotometer at 319 nm against blank. Similarly the in vitro release of control solutions were also performed (PBS PH 6.6 drug solution). Revathy V Nair et al. Int. Res. J. Pharm. 2014, 5 (5) Page 386 In vitro Permeation Study Fresh periodontal tissue was removed from bovine periodontal cavity obtained from local slaughter house. Periodontal mucosal permeation studies of the prepared gel were carried out using Franz diffusion cell. Pre-treated epithelial mucosa was fixed onto the Franz diffusion cell. Accurately weighed 1 ml gel was spread uniformly on an area of 1 cm of the mucosa, previously fixed in between the donor and receptor compartment of the Franz diffusion cell. The receptor compartment contained 15 ml of phosphate buffer, pH 6.6. The temperature of the elution medium was thermostatically controlled at 37 + 1°c by a surrounding water jacket, and the medium was kept as a static model throughout the study. Aliquots of 1 ml withdrawn at predetermined intervals for 48 h, and an equal volume of prewarmed buffer, was replaced. The samples were analyzed, after appropriate dilution, for SZ content spectrophotometrically at 319 nm against appropriate blank. The cumulative drug permeated per unit area was plotted against the time. The slope of the plot was noted and compared. Similar experiments were conducted with control (PBS PH 6.6 drug solution) also. Blanks were run for each set as described above, using placebo gel. Mucosa Deposition Studies Perform the in vitro permeation study for 48 h, and then the donor compartment was washed five times with methanol. The periodontal mucosa was extracted with methanol as a receptor solution for a further period of 12 hours and the amount of the drug was determined by spectrophotometricaly at 319 nm. During this stage, methanolic receptor solution will diffuse into the mucosa, releasing both bound and free form of drug and are estimated. Histopathological Evaluation of Mucosa Histopathological evaluation of tissue incubated in PBS (pH 6.6) after collection was compared with tissue incubated in the diffusion chamber with in situ gel formulation. Tissue was fixedin 10 % buffered formalin (pH 6.6), routinely processed and embedded in paraffin. Paraffin sections (7 μm) were cut on glass slides and stained with hematoxylin andeosin (HE). Sections were examined under a light microscope, to detect any damage to the tissue during in vitro permeation by a pathologist blinded to the study. In vitro Antibacterial Activity Formulation G6 containing satranidazole as drug are used in microbial assays. Drug equivalent to 1 mg formulations are used for measurement of zone of inhibition. Under aseptic conditions the formulated gels and placebo were placed on blood agar plates containing porphyromonas gingivalis and were incubated at 37°C for 24 h, after which zone of inhibition was measured. This was continued for 3 days and zone of inhibition on every 24 h interval was measured. 26-27 Scanning electron microscopy (SEM) Scanning electron microscopy (SEM) of the in situ gel was performed to evaluate the surface and cross morphology of the in situ gel (Joel jsm-6490la analytical SE). Samples were dried for 24 h before the analysis. Samples were transferred into the SEM instrument after gold coating. The SEM analysis was carried out at room temperature. Stability Studies The optimized in situ gel formulation F5 was kept for stability studies for 45 days at room temperature (30 ± 2°C), a refrigerator temperature (4 ± 2°C) and oven temperature (45 ± 2°C) to determine physical and chemical stabilities. The formulation was evaluated visually and for drug content and % cumulative drug release after 7, 15, 30 and 45 days. RESULTS In this study, the thermo gelling polymer, chitosan with different concentrations has been used for formulation of in situ gel of Satranidazole with 10 % propylene glycol as plasticizer and were allowed to cross linked with 1 % solution of glutaraldehyde in order to extend the drug release for a longer period of time. The typical composition is shown in Table 1. The solubility studies of pure Satranidazole as shown in Table 2 revealed that the pure drug is freely soluble in methanol, dilute acid, 1,4,dioxane and n, ndimethyl formamide and practically insoluble in water. The FTIR spectra of Satranidazole-chitosan physical mixture (Figure 1) shows characteristic peaks at 3000 (aromatic –CH stretch), 1750 (C=O stretch), 1350(-NO2 Stretching) and 750 cm (NO2 Stretch) respectively. All characteristic peaks of drug are present in the polymer drug mixture. There is reduction in peak intensity but not shifting of the band indicating that there is no interaction between satranidazole and the respective polymer, hence compatible. X-ray diffraction was carried out to determine the nature of the materials whether a material is amorphous or crystalline. Pure Satranidazole showed characteristic peaks at 16.764 o, 66.44 o, 74.25 o, 51.50 o at 2θ value. The XRD of drug – chitosan physical mixture (Figure 2) revealed a reduction in polymer peak intensity when compared with XRD of plain drug and polymer and showed reduced crystalline properties, indicating of possible conversion into amorphous form. A little decrease in the crystallinity of drug polymer physical mixture is due to the hydrogen bonding between the drug and polymers, which leads to their good compatibility. The developed formulations were evaluated for various parameters like surface pH, gelation temperature, drug content, spreadability, viscosity, bio adhesion study, in vitro drug release and in vitro antibacterial activity. The formulation stored at 4 ̊C before application, which is syringeable through 21 gauge needle. This formulation is directly injected in to periodontal pocket where it will immediately convert in to gel form at body temperature. In the preliminary studies, the minimum concentration of chitosan that formed gel below 36C was found to be 0.5 % wt/vol. In general, the gelation temperatures have been considered to be suitable if they are in the range of 25C to 37C. If the gelation temperature of a thermo gelling formulation is lower than 25C, a gel might be formed at room temperature leading to difficulty in manufacturing, handling, and administering. If the gelation temperature is higher than 37C, a liquid dosage form still exists at the body temperature, resulting in the loss of the administered drugs at an early stage. As the temperature of the periodontal cavity is 36C, this study aimed at preparing the liquid formulations of chitosan that may gel below 36C. The results also revealed that as the increase of bio adhesive polymer chitosan concentration, increase in the gelation temperature. The pH of all the formulations were found to be within the range between 5.8 – 6.5 and the periodontal mucosa can tolerate the above mentioned pH of the formulations. Revathy V Nair et al. Int. Res. J. Pharm. 2014, 5 (5) Page 387 Table 1: Composition of different cross linked in situ gel formulations containing satranidazole Ingredients G1 G2 G3 G4 G5 G6 Satranidazole 1 % 1 % 1 % 1 % 1 % 1 % Chitosan 0.5 % 1 % 1.5 % 2 % 2.5 % 3 % Propylene glycol 10 % 10 % 10 % 10 % 10 % 10 % Acetic acid solution (1%) 10 ml 10 ml 10 ml 10 ml 10 ml 10 ml Aq. Gluteraldehyde 1 % 1 % 1 % 1 % 1 % 1 % Table 2: Solubility Profile of Pure Satranidazole Drug in various solvents S. No. Solvent Solubility (mg/ml)