Mechanical and adhesive properties of cellulosic film coats containing polymeric additives.

The effects of some polymeric additives, i.e. corn starch (CS) and magnesium stearate (MS), on mechanical properties (tensile strength, modulus of elasticity, and elongation at break) and adhesive toughness of hydroxypropyl methylcellulose (HPMC) and ethylcellulose (EC) film coats were investigated. The free and in situ films containing 10 and 20% additives by weight of polymer were prepared by spray method. The mechanical properties of both HPMC and EC free films decreased as the concentration of additives was increased because of the lower stiffening effect brought about by hydrodynamic or reinforcing effect. However, adhesive toughness of in situ films was found to increase for HPMC whereas that of EC films decreased with the increasing concentration of polymeric additives. Such contradictory results between these two film forming polymers may be attributed to the net result of the opposite effects between interference of film-tablet interfacial bonds and the reduction of mechanical properties. The former seemed to be preferential in the case of EC films, while the latter predominated for HPMC films. Such conclusions were supported by the FTIR results, in which the polymer-additive interaction was found for EC. Increase in concentration of polymeric additives resulted in the decrease in mechanical properties of free films whereas the adhesive toughness of in situ films may be influenced by either the interference of film-tablet interfacial bonds or the significant reduction of mechanical properties.

Development of chitosan-coated liposomes for sustained delivery of tamarind fruit pulp's extract to the skin.

In this study, chitosan-coated liposomes were developed. To entrap lyophilized tamarind extract containing alpha-hydroxy acids (AHAs) together with tartaric acid, the reverse phase evaporation method was used to obtain well-formed liposomes loaded with the extract. The highest entrapment efficiency of 68.3 +/- 3.0% into the liposomes was obtained with liposomes consisting of phosphatidylcholine and cholesterol in a molar ratio of 2 : 1 after the extrusion process. The average particle size of the prepared liposomes was 158 +/- 26 nm showing a negative zeta potential of -6 mV. For the preparation of the chitosan-coated liposomes, two selected independent parameters were varied: chitosan concentrations of 0.1, 0.5 and 1.0% w/v and volumes of the chitosan solutions of 1, 2 and 3 mL, to study the effects of such parameters on the entrapment efficiency of the extract-loaded liposomes. Variation in the volumes of the chitosan solution did not affect the entrapment efficiency of the liposomes. However, the entrapment efficiency of the AHAs in the chitosan-coated liposomes significantly increased with increasing chitosan concentrations. The size of the chitosan-coated liposomes was in the range of 200-300 nm with a positive zeta potential in the range of 6-29 mV. An in vitro release study using dialysis technique was performed to evaluate the release profile of the tartaric acid from the chitosan-coated liposomes. The obtained results showed the effect of the chitosan-coated liposomes on the lower release rate and on the amount of tartaric acid in comparison with that of the uncoated liposomes. The study in an in vitro skin cell model indicated that the developed system could enhance the potential of tamarind's AHAs on the stimulation of human keratinocyte proliferation being two-fold higher than the solution of the tamarind extract.

Influence of methylation process on the degree of quaternization of N-trimethyl chitosan chloride.

N-Trimethyl chitosan chloride (TMC) is a soluble chitosan derivative that shows effective enhancing properties for peptide and protein drug transport across mucosal membranes. TMC was synthesized by reductive methylation of chitosan in an alkaline environment at elevated temperature. The number of methylation process steps and the base used in the process was demonstrated to affect the degree of quaternization of the primary amino group and methylation of 3- and 6-hydroxyl groups. 1H-Nuclear magnetic resonance spectra showed that the degree of quaternization of TMC was higher when using sodium hydroxide as the base compared to using dimethyl amino pyridine. The degrees of quaternization as well as O-methylation of TMC increased with the number of reaction steps. O-Methylation resulted in decreased solubility of TMC. The high degree of quaternization of TMC with a low degree of O-methylation was prepared by employing one reaction step with two subsequent addition steps and a controlled alkaline environment of the mixture reaction.