The purpose of this work was to investigate the factors involved in the formation of a new type of nanoparticle made of hydrophilic polysaccharides, chitosan (CS), and glucomannan (GM) and to study their potential for the association and delivery of proteins. Two different types of glucomannan were used (non-phosphorylated Konjac GM (KGM) and phosphorylated GM), and two different approaches were adopted for the preparation of the nanoparticles. These procedures involved the interaction of CS and GM in the presence or absence of sodium tripolyphosphate, which acted as an ionic cross-linking agent for CS. Using both approaches, it was possible to obtain nanoparticles with a size in the range from 200 to 700 nm and a variable zeta potential (from −2 to +39 mV), depending on the formulation conditions. Despite the mild forces involved in their formation, by adjusting the process variables, it was also possible to obtain nanoparticles that remain stable upon dilution with phosphate buffer saline. The nanoparticles exhibited a great capacity for the association of the model peptide insulin and the immunomodulatory protein P1, reaching association efficiency values as high as 89%. Moreover, the release of the peptide/protein could be modulated by varying the composition of the system. Consequently, the results presented here suggest that chitosan−glucomannan nanoparticles are promising carriers for the oral administration of peptides and proteins.

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The aim of the present work was to develop a new nanoparticle carrier, adapted for the oral administration of proteins and their delivery to the immune system. Chitosan and phosphorylated glucomannan were chosen as major constituents of the nanoparticles. Chitosan nanoparticles were formed by ionic gelation and then coated with glucomannan. Two different protocols were adopted for the formation of the glucomannan coating: protocol I, in which chitosan nanoparticles were isolated before their coating; protocol II, in which chitosan nanoparticles were not isolated, but coated with glucomannan in the presence of free chitosan. The results showed that, under the selected formulation conditions, the sizes of the nanoparticles ranged between 170 and 300 nm and their zeta potential values were inverted from positive to negative by the glucomannan coating. The nanoparticles prepared by the two protocols could be freeze-dried, in the presence or absence of cryoprotective agents, preserving their original characteristics. The results of the stability study evidenced the positive role of the glucomannan coating in preventing the aggregation of the nanoparticles in buffered media. Finally, the association of the inmunomodulatory protein complex P1 to the chitosan-glucomannan nanoparticles was investigated. The results showed that the association was not dependent on the chitosan: sodium tripoliphosphate ratio, but it was significantly affected by the presence of sodium phosphate in the protein structure.

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Cefuroxime axetil (CA) was encapsulated in pH-sensitive acrylic microspheres in order to formulate a suspension dosage form. Using this microencapsulated form it was expected to prevent leaching of the drug from the microspheres into the suspension medium and to assure the release of the drug in the first part of the intestine, thus avoiding changes to its bioavailability. For this purpose, CA was microencapsulated within several types of acrylic polymers by the solvent evaporation and the solvent extraction techniques. The acrylic polymers selected were: Eudragit E (positively charged and soluble at pH 5), Eudragit L-55 (negatively charged and soluble at pH > 5.5) and Eudragit RL (neutral, insoluble, but readily permeable). The influence of the polymer electrical charge on the stability and in vitro release of CA was investigated. Though Eudragit E microspheres presented good morphological characteristics and dissolution behaviour, the analysis of the stability of CA in the presence of Eudragit E by HPLC, indicated a negative interaction between both compounds. However, formulations made of Eudragit L-55 and RL in the ratios 100:0 and 90:10 were adequate in terms of the stability of the encapsulated CA. The dissolution studies showed a critical pH between 5.2 and 6.0, which allowed the complete release of CA in a short period. Furthermore, these polymer microspheres were shown to be efficient in masking the taste of CA.

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