Influence of formulation on the physicochemical properties of casein microparticles.

Casein microparticles (CAS/MP) have a potential clinical use for targeting drugs. However, the use of organic solvents in their preparation is undesirable. This study was designed to investigate the influence of preparation procedures in aqueous media on the formulation and physicochemical properties of CAS/MP. The first stage involved the influence of the coacervating agents (lactic acid, succinic anhydride, succinic acid and tartaric acid). The second stage studied was the influence of the ionic strength and the third, the influence of adding a thickener, hydroxypropyl cellulose or hydroxypropyl methycellulose (HPC or HPMC), and a plasticizing agent (gelatin). Some physicochemical properties of CAS/MP were evaluated. While the infrared and the thermal analysis showed that all coacervating agents were appropriate for coacervation, the scanning electron microscopy studies showed that the external morphology of the particles was more homogeneous when lactic acid was used. Utilizing lactic acid as the coacervating agent, there was a trend effect of adding NaCl implying that the increasing of the ionic strength resulted in better stability. Finally, the addition of 0.1% HPC plus either 0.25 or 0.5% gelatin resulted in homogeneous formulations. In conclusion, the use of lactic acid plus 0.1% HPC and 0.25% gelatin results in biodegradable and homogeneous CAS/MP, presenting a potentially useful drug delivery system.