SYNOPSISHydrophilic nanoparticulate carriers have important potential applications for the administration of therapeutic molecules. The recently developed hydrophobic-hydrophilic carriers require the use of organic solvents for their preparation and have a limited protein-loading capacity. To address these limitations a new approach for the preparation of nanoparticles made solely of hydrophilic polymers is presented. The preparation technique, based on an ionic gelation process, is extremely mild and involves the mixture of two aqueous phases at room temperature. One phase contains the polysaccharide chitosan (CS) and a diblock copolymer of ethylene oxide and propylene oxide (PEO-PPO) and, the other, contains the polyanion sodium tripolyphosphate (TPP). Size (200-1000 nm) and zeta potential (between /20 mV and /60 mV) of nanoparticles can be conveniently modulated by varying the ratio CS/PEO-PPO. Furthermore, using bovine serum albumin (BSA) as a model protein it was shown that these new nanoparticles have a great protein loading capacity (entrapment efficiency up to 80% of the protein) and provide a continuous release of the entrapped protein for up to 1 week.

CS and CS/PEO-PPO nanoparticles prepared by a very mild ionic crosslinking technique are novel and suitable systems for the entrapment and controlled release of proteins and vaccines.

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Chitosan nanoparticles are efficient vehicles for the transport of insulin through the nasal mucosa.

Nanoparticles intended for use in the transmucosal delivery of macromolecules were prepared by the ionic gelation of chitosan (CS) hydrochloride with pentasodium tripolyphosphate (TPP) and concomitant complexation with sodium alginate (ALG). The incorporation of a small proportion of ALG of increasing molecular weight (M(w); from 4 to 74 kDa) into the nanoparticles led to a monotonic increase in colloidal size from ∼260 to ∼525 nm. This increase in size was regarded as a consequence of the formation of gradually more expanded structures. Insulin, taken as a model peptide, was associated to CS-TPP-ALG nanoparticles with efficiencies in the range of ∼41 to ∼52%, irrespective of the M(w) of the ALG incorporated in the formulation. These CS-TPP-ALG nanoparticles exhibited a capacity to enhance the systemic absorption of insulin after nasal administration to conscious rabbits. Interestingly, it was observed that the duration of the hypoglycaemic response was affected by the ALG's M(w). Briefly, this work describes a new nanoparticulate composition of potential value for increasing nasal insulin absorption.

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