Texture and topography analysis of doxycycline hyclate thermosensitive systems comprising zinc oxide

To characterize the thermal behavior and texture analysis of doxycycline hyclate thermosensitive gels developed for periodontitis treatment containing zinc oxide prepared by using poloxamer (Lutrol(®) F127) as polymeric material and N-methyl pyrrolidone was used as cosolvent. The thermosensitive gel comprising doxycycline hyclate, Lutrol(®) F127, and N-methyl pyrrolidone were characterized for the thermal behavior and texture analysis. The topography of the system after the dissolution test was characterized with scanning electron microscope. Differential scanning calorimetric thermogram exhibited the endothermic peaks in the systems containing high amount of N-methyl pyrrolidone in solvent. The sol-gel transition temperature of the systems decreased as the zinc oxide amount was increased. The addition of doxycycline hyclate, zinc oxide, and N-methyl pyrrolidone affected the syringeability of systems. The addition of zinc oxide into the doxycycline hyclate-Lutrol(®) F127 systems decreased the diameter of inhibition zone against Staphylococcus aureus, Escherichia coli, and Candida albicans since zinc oxide decreased the diffusion and prolonged release of doxycycline hyclate. From scanning electron microscope analysis, the porous surface of 20% w/w Lutrol(®) F127 system was notably different from that of gel comprising doxycycline hyclate which had interconnected pores and smooth surfaces. The number of pores was decreased with increasing zinc oxide and the porous structure was smaller and more compact. Therefore, the addition of zinc oxide could increase the syringeability of doxycycline hyclate-Lutrol(®) F127 system with the temperature dependence. Zinc oxide decreased inhibition zone against test microbes because of prolongation of doxycycline hyclate release and reduced size of continuous cells. Furthermore, zinc oxide also increased the compactness of wall surfaces of Lutrol(®) F127.