Design And Evaluation Of Suitable Localized Drug Films Based On Carboxymethyl-chitosan For Periodontal Treatment

In order to design suitable localized drug films with carboxymethyl-chitosan (CMCS), we prepared two types of CMCS film systems by using high technologic process of polymer materials, one is CMCS/PVA blend films and the other is CMCS microspheres (Cs2Ms) in PVA film forming a multi-structure system (Cs2Ms-PVA). In the paper, the two CMCS film systems that used for localized delivering drug were prepared. The pharmaceutical and biological properties of the two film systems were characterized, and their feasibilities for using as periodontal treatments were investigated. The results were reported as follow:Several carboxymethyl-chitosan (CMCS) samples with different deacetylation degree (Dd) and/or substituent degree (Ds) were prepared from the carboxymethylation reaction of chitosan under soft conditions. The products were dissolved in standard HCl aqueous solution (0.1 M) to carry out potentiometric titration by using NaOH as titrating solution at different ionic strengths. Then the dissociation behaviors of protonated carboxyl and amine groups of CMCS were investigated under their degree of dissociation (α) and protonation constant (pKa) had been calculated. Moreover, influence of the intrinsic parameters (e.g. Dd and Ds) and extrinsic parameters (e.g. pH and ionic strength) on the dissociation behavior of CMCS were also considered in this paper. As a result, dissociations of carboxyl and amine on CMCS exhibited unusual behaviors in comparison with carboxyl on carboxymethyl-cellulose and amine groups on chitosan, respectively. The pKa values of carboxyl declined slightly at early dissociation stage but subsequently maintained constant. For that, we obtained the modeling equations by means of mathematic simulation. In contrast, the pKa of ammonium increased with its dissociation degree (αn) despite that there was an inflexed change on itsαn-pKa curve. The potentiometric behavior of carboxyl was hardly affected by variation of Dd or Ds. However, the intrinsic parameters (Dd and Ds) played more important role on dissociations of ammonium on CMCS. The ionic strength of media could bring screening effect on dissociaciation of both sorts of ionizable groups on CMCS. With increasing the ionic strength of media, screening effect on dissociations increased significantly. The distinguishable films composed of PVA and CMCS were prepared byblending/casting method, and loaded with ornidazole as local drug delivery system. In vitro test, the blend films showed pH-depended swelling behavior and seemly drug release action, and also exhibited a little antibacterial activity for E.coil and S.aureus strains. Those characteristics of CMCS/PVA blend films were controlled by the weight ratio of CMCS and PVA in the blended films. Increasing the content of PVA in blended films reduced the swelling ratio and decelerated the drug release. However, increasing the content of CMCS would enhance the antibacterial activity.A background for study CMCS/PVA blend film was the intended use of polymer films as coating material in a site-specific drug delivery system. The surface morphology of compact dried films and swollen blend films were detected using scanning electron microscopy. Roughness image was shown on the surface of high CMCS content blend films. The structure of 50%C films (i.e. content of CMCS in the blend was 50%) became loosen and porous after adsorbing water. Blending PVA with CMCS also brought the coating films with some pH-sensitive swelling properties. Low swelling degree was found at acidic condition, but high swelling degree was found at high pH conditions. Permeation of model drugs through blend films was studied using a modified side-to-side static diffusion-vessels. The results showed that drugs permeation was affected by several impacts. Enhancement of the CMCS content in the blend film, decrease of the drugs'molecule weight, increase the pH of medium and rational attenuation of the film thickness would all accelerated the solutes permeating the blend coating films.Bovine serum albumin (BSA) and bovine fibrinogen (BFG) were chose as representative plasma proteins to carry out adsorption test. Equilibrium adsorption amount of proteins onto the blends decreased with the increase of CMCS content in film matrix, and BSA was more easily adsorbed onto the films than BFG at the same conditions. The blend films also exhibited different trend for BSA and BFG adsorption when pH of the media changed, but maximum adsorption approximately occurred at the isoelectric point of proteins. Moreover, increasing the ionic strength would always decrease the adsorptions of protein onto the films. In animal experiments, it was found that incorporation of CMCS and PVA brought lower tissue reaction than pure PVA films as they were subcutaneously implanted in Wister rat. After two weeks subcutaneous implantation, surfaces of PVA became wrinkled and cracked, however, the blend implants exhibited alveolate porous microstructure.The bioactivities of the blend film were also checked using anaerobic bacterial and some animal molds. This blend drug system was of no hemolysis, no toxicity to skin of Guinea pig and periodontium of Wister rat, and exhibited excellent antibacterial activity to ATCC 25586 and ATCC 25175. After embedding the 30%C blend drug films in the periodontum of rat model, the systems kept a good retention at the application site and maintained high drug concentration in long time (5 days) more extended the period in vitro (220 mins).Carboxymethyl-chitosan microspheres (Cs2Ms) were prepared by a method of emulsification combined with two-step solidification and loaded ornidazole as model drug. The ornidazole loaded Cs2Ms were incorporated into PVA film to form a multi-structure drug system (Cs2Ms-PVA) for feasibly releasing drug in local site. The appearance, particle size, drug loading and encapsulation efficiency, and drug release profiles of Cs2Ms could be tailored in the preparation. Appropriate enhancement of drug amount in the microsphere would bring optimum effect on drug loading percentage and release profile. The use of dimethylsulfoxide (DMSO) could produce spherical spheres with smooth surface and small size, but depress the drug loading and encapsulation efficiency and hasten the burst drug release. For the multi-structure carrier materials, the outer PVA film rapidly breaks up to pieces after about 30 min of placement in water and then entirely dissolved. Drug release from the multi-structure carriers was a little faster than that from the pure Cs2Ms. Ornidazole release from the carriers performed a burst release in the initial 2 hours then followed a gradual release. It could be achieved the controlled release pattern of ornidazole by dispersing the well prepared Cs2Ms into PVA film.As core parts of the novel formulation of Cs2Ms-PVA, chitosan-based microsphere was prepared form chitosan and/or carboxymethyl-chitosan (CM-chitosan) by using water in oil emulsification method. Then basic in vitro and in vivo experiments focusing on biocompatibility and biodegradability of the chitosan-based microspheres were carried out to evaluate the feasibility of the novel film formulation. In vitro tests, besides having no hemolysis, CM-chitosan microsphere (Cs2Ms) have adsorbed little proteins on their surfaces. Moreover, plasma proteins adsorbed on Cs2Ms, most of which can easily desorbed, are much less than that adsorbed on Cs1Ms. This indicates that Cs2Ms perhaps has better biocompatibility than Cs1Ms. In vivo tests, subcutaneous implantation of Cs1Ms and Cs2Ms in rat was carried out to investigate the host tissue inflammatory response and biodegradability of the microspheres. Implantations of Cs1Ms and Cs2Ms induced a littlie more severe inflammation when compared with the implantation of PVA film. However, the difference on in vivo biocompatibility between Cs1Ms and Cs2Ms could not be confirmed by the implantation model used in our experiments. Both Cs1Ms and Cs2Ms had suffered bioerosion when they were subcutaneously implanted. The hard and compact matrixes of Cs1Ms were degraded very slowly, and only some trifling degradation had been found until 4 weeks of implantation. In contrast, Cs2Ms is soft and more hydrophilic, and can be quickly degraded in a form of diffluence by the physiological circumstance. All these results suggested that Cs2Ms had better potentials used as core parts of the novel designed film dosage in the future developments.Based on the above considerations, we incline to design the novel periodontal localized drug delivery system with carboxymethyl-chitosan in despite that there were some limits on the development of the two film dosages based on in vivo or in vitro findings.