Influences of process parameters on preparation of microparticle used as a carrier system for omega - 3 unsaturated fatty acid ethyl esters used in supplementary nutrition.

Microparticles were prepared by complex coacervation to encapsulate eicosapentaenoic acid ethyl ester (EPA-EE) for incorporation into foods as a nutrition supplement. Gelatin and acacia were used in the coacervation process. With an increasing oil/polymer ratio, both yield and encapsulation rate decreased; with an increasing homogenization time, the yield remained constant while the encapsulation rate slightly increased. Several particle hardening techniques were examined and their influence on particle structure, yield and encapsulation rate were examined. Ethanol hardening was compared to cross-linking with dehydroascrobic acid with respect to both yield and encapsulation rate. The particle diameters for both formulations were similar (ethanol: 38.4 +/- 4.1 microm; cross-linking: 41.8 +/- 3.0 microm). Spray-drying of the coacervates led to the smallest particles (5.2 +/- 1.1 microm), lowest yield and encapsulation rate. All microencapsulation products were assayed for their storage stability over 4 weeks with respect to the oxidation of the encapsulated omega - 3 unsaturated fatty acid ester inside the particles. Hardening with ethanol showed the lowest amount of peroxides: particle wall cross-linking by dehydroascorbic acid and spray-drying were observed to be less protective. All microparticles were characterized for their internal structure with confocal laser scanning microscopy (CLSM) after fluorescence labelling of the polymers, in order to localize the oil phase and visualize the distribution of the polymers in the coacervates. With increasing homogenization time, the internal structure changed stepwise from a capsule structure (core/wall) towards a matrix structure. For all experiments, a homogeneous distribution for both polymers, gelatin and acacia was observed inside the particle wall. No influence of the different particle hardening procedures on the polymer distribution was found.

Cortical activation in profoundly deaf patients during cochlear implant stimulation demonstrated by H2(15)O PET.

Cochlear implants (CIs) are used to provide sensations of sound to profoundly deaf patients. The performance of the CI is assessed mainly by the subjective reports of patients. The aim of this study was to look for objective cortical responses to the stimulation of the CI. Two postlingually and two prelingually deaf patients were investigated by positron emission tomography (PET) using 15O-labeled water (H2(15)O) to determine the regional cerebral blood flow (rCBF). Instead of quantifying rCBF in absolute terms, it was estimated by referring the regional tissue concentration of H2(15)O to the mean whole brain concentration. CI stimulation encoded from white noise and sequential words led to an increased rCBF in the primary and secondary (Wernicke) auditory cortex. Relative elevations of up to 33% were observed bilaterally, although they were higher contralateral to the CI. These results were obtained not only in the postlingually deaf patients but also in two patients who had never been able to hear. Thus, it could be demonstrated that PET measurements of cerebral H2(15)O distribution yield objective responses of the central auditory system during electrical stimulation by CIs in profoundly deaf patients.