The effect of core-to-wall ratio and Span 80 concentration on the properties of ascorbic acid microcapsules

One Factor at a Time and factorial experimental design for formulation of l-carnitine microcapsules to improve its manufacturability

l-carnitine is an essential dietary supplement of physiological importance. Handling and manufacture of l-carnitine is difficult due to its hygroscopic nature, resulting in impairing its flow properties, as well as solid dosage form stability. The study aimed at reducing l-carnitine hygroscopicity through its encapsulation within a hydrophobic, pH-insensitive polymer. A solid in oil in oil (s/o/o) emulsion solvent evaporation technique for microencapsulation was adopted to exclude the possibility of water uptake. The polymers used were two ethyl cellulose (EC) grades with different viscosities. The chosen solvent for the polymer was acetone, and liquid paraffin was the dispersion medium in which both the drug and polymer were insoluble. Sixteen formulations were developed, and evaluated to study the formulation parameters as anti-coalescent type, mixing speed, surfactant type and polymer ratio, and viscosity grade. A "One Factor at A Time" (OFAT) design of experiment, and a factorial design were utilized. Study results revealed that successful microencapsulation occurred by using Aerosil 200 (0.1 %) as anti-coalescent, a mixing speed of 1000 rpm, and Ethocel Std 20 at a 3:1 drug-to-polymer ratio. Microcapsule formulation containing l-carnitine base, successfully compressed into tablets, showed acceptable water content, disintegration time, hardness, and dissolution. Moreover, it showed acceptable stability upon storage at 40 °C at 75 % RH for six months compared to l-carnitine tablets prepared by wet granulation.

Preparation and characterization of biodegradable urea-loaded microparticles as an approach for transdermal delivery

This work describes the formulation and characterization of urea-loaded microspheres prepared using various polymers such as ethyl cellulose (EC), cellulose acetate phthalate (CAP) and poly (D,L-lactic-co-glycolic acid) (PLGA), along with the utilization of a solvent evaporation technique. The effect of various formulation parameters (i.e. polymer type and concentration, vehicle type, polymer solution/vehicle volume ratio, drug/polymer ratio, homogenizer and stirrer speed, sonication time and speed, type of washing solution, drying and separation method) on the characteristics of microspheres was also evaluated. Results obtained indicated that, in the presence of urea, highest rate of EC microsphere production could be obtained at a drug/polymer ratio of 1:2 and a polymer solution/vehicle volume ratio of 1:50. In some cases, crystallization of urea was observed during the encapsulation process using cellulose derivative polymers. CAP microparticles showed a rough and tortuous surface while EC microparticles had a wider range of particle size. However, with the PLGA polymer, much better desired microparticles with a smaller size range of 1-3 microm were obtained. In general, PLGA microspheres were spherical in shape and possessed smooth surfaces with less pores in comparison with those obtained by the other polymers. The yield of particle production and the extent of urea encapsulation in PLGA particles were measured to be 68.87% +/- 5.3 and 40.5% +/- 3.4, respectively. The release study from PLGA microspheres revealed that up to 70% of the drug was released within a few days, through a four-stage release pattern.