Carmen Remuñán-López

Novel hydrophilic chitosan-polyethylene oxide nanoparticles as protein carriers

Hydrophilic 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.

Chitosan and chitosan/ethylene oxide-propylene oxide block copolymer nanoparticles as novel carriers for proteins and vaccines.

AbstractPurpose. The aim of this study was to investigate the interaction between the components of novel chitosan (CS) and CS/ethylene oxide-propylene oxide block copolymer (PEO-PPO) nanoparticles and to evaluate their potential for the association and controlled release of proteins and vaccines. Methods. The presence of PEO-PPO on the surface of the nanoparticles and its interaction with the CS was identified by X-ray photoelectron spectroscopy (XPS). The mechanism of protein association was elucidated using several proteins, bovine serum albumin (BSA), and tetanus and diphtheria toxoids, and varying the formulation conditions (different pH values and concentrations of PEO-PPO), and the stage of protein incorporation into the nanoparticles formation medium. Results. BSA and tetanus and diphtheria toxoids were highly associated with CS nanoparticles partly due to electrostatic interactions between the carboxyl groups of the protein and the amine groups of CS. PEO-PPO also interacted electrostatically with CS, thus competing with the proteins for association with CS nanoparticles. A visible amount of PEO-PPO was projected towards the outer phase of the nanoparticles. Proteins were released from the nanoparticles at an almost constant rate, the intensity of which was closely related to the protein loading. Furthermore, the tetanus vaccine was released in the active form for at least 15 days. Conclusions. 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.

Enhancement of Nasal Absorption of Insulin Using Chitosan Nanoparticles

AbstractPurpose. To investigate the potential of chitosan nanoparticles as a system for improving the systemic absorption of insulin following nasal instillation. Methods. Insulin-loaded chitosan nanoparticles were prepared by ionotropic gelation of chitosan with tripolyphosphate anions. They were characterized for their size and zeta potential by photon correlation spectroscopy and laser Doppler anemometry, respectively. Insulin loading and release was determined by the microBCA protein assay. The ability of chitosan nanoparticles to enhance the nasal absorption of insulin was investigated in a conscious rabbit model by monitoring the plasma glucose levels. Results. Chitosan nanoparticles had a size in the range of 300−400 nm, a positive surface charge and their insulin loading can be modulated reaching values up to 55% [insulin/nanoparticles (w/w): 55/100]. Insulin association was found to be highly mediated by an ionic interaction mechanism and its release in vitro occurred rapidly in sink conditions. Chitosan nanoparticles enhanced the nasal absorption of insulin to a greater extent than an aqueous solution of chitosan. The amount and molecular weight of chitosan did not have a significant effect on insulin response. Conclusions. Chitosan nanoparticles are efficient vehicles for the transport of insulin through the nasal mucosa.

Design of microencapsulated chitosan microspheres for colonic drug delivery

Among the different approaches to achieve colon-selective drug delivery, the use of polymers, specifically biodegraded by colonic bacteria, holds great promise. In this work a new system which combines specific biodegradability and pH-dependent release is presented. The system consists of chitosan (CS) microcores entrapped within acrylic microspheres. Sodium diclofenac (SD), used as a model drug, was efficiently entrapped within CS microcores using spray-drying and then microencapsulated into Eudragit L-100 and Eudragit S-100 using an oil-in-oil solvent evaporation method. The size of the CS microcores was small (1.8-2.9 microns) and they were encapsulated within Eudragit microspheres (size between 152 and 233 microns) forming a multireservoir system. Even though CS dissolves very fast in acidic media, at pH 7.4, SD release from CS microcores was delayed, the release rate being adjustable (50% dissolved within 30-120 min) by changing the CS molecular weight (MW) or the type of CS salt. Furthermore, by coating the CS microcores with Eudragit, perfect pH-dependent release profiles were attained. No release was observed at acidic pHs, however, when reaching the Eudragit pH solubility, a continuous release for a variable time (8-12 h) was achieved. A combined mechanism of release is proposed, which considers the dissolution of the Eudragit coating, the swelling of the CS microcores and the dissolution of SD and its further diffusion through the CS gel cores. In addition, infrared (IR) spectra revealed that there was an ionic interaction between the amine groups of CS and the carboxyl groups of Eudragit, which provided the system with a new element for controlling the release. In conclusion, this work presents new approaches for the modification of CS as well as a new system with a great potential for colonic drug delivery.

DESIGN AND EVALUATION OF CHITOSAN/ETHYLCELLULOSE MUCOADHESIVE BILAYERED DEVICES FOR BUCCAL DRUG DELIVERY

This paper describes the preparation of new buccal bilayered devices comprising a drug-containing mucoadhesive layer and a drug-free backing layer, by two different methods. Bilaminated films were produced by a casting/solvent evaporation technique and bilayered tablets were obtained by direct compression. The mucoadhesive layer was composed of a mixture of drug and chitosan, with or without an anionic crosslinking polymer (polycarbophil, sodium alginate, gellan gum), and the backing layer was made of ethylcellulose. The double-layered structure design was expected to provide drug delivery in a unidirectional fashion to the mucosa and avoid loss of drug due to wash-out with saliva. Using nifedipine and propranolol hydrochloride as slightly and highly water-soluble model drugs, respectively, it was demonstrated that these new devices show promising potential for use in controlled delivery of drugs to the oral cavity. The uncrosslinked chitosan-containing devices absorbed a large quantity of water, gelled and then eroded, allowing drug release. The bilaminated films showed a sustained drug release in a phosphate buffer (pH 6.4). Furthermore, tablets that displayed controlled swelling and drug release and adequate adhesivity were produced by in situ crosslinking the chitosan with polycarbophil.

Chitosan-alginate blended nanoparticles as carriers for the transmucosal delivery of macromolecules.

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 ALGs M(w). Briefly, this work describes a new nanoparticulate composition of potential value for increasing nasal insulin absorption.

Microencapsulated chitosan nanoparticles for pulmonary protein delivery: In vivo evaluation of insulin-loaded formulations

This work presents a new dry powder system consisting of microencapsulated protein-loaded chitosan nanoparticles (CS NPs). The developed system was evaluated in vivo in rats in order to investigate its potential to transport insulin (INS), a model protein, to the deep lung, where it is absorbed into systemic circulation. The INS-loaded CS NPs were prepared by ionotropic gelation and characterized for morphology, size, zeta potential, association efficiency and loading capacity. Afterwards, the NPs were co-spray dried with mannitol resulting in a dry powder with adequate aerodynamic properties for deposition in deep lungs. The assessment of the plasmatic glucose levels following intratracheal administration to rats revealed that the microencapsulated INS-loaded CS NPs induced a more pronounced and prolonged hypoglycemic effect compared to the controls. Accordingly, the developed system constitutes a promising alternative to systemically deliver therapeutic macromolecules to the lungs, but it can also be used to provide a local effect.

Glucomannan, a promising polysaccharide for biopharmaceutical purposes

Over the last few decades, polysaccharides have gained increasing attention in the biomedical and drug delivery fields. Among them, glucomannan (GM), has become a particularly attractive polymer. In this paper, we review the physicochemical and biological properties which are decisive for the exploitation of GM as a biomaterial. These properties include the structural organization, molecular weight, solubility, viscosity, gelling properties and degradation behavior. Moreover, herein we analyze the possibilities of combining GM with other hydrophilic polymers, as well as the preparation of semisynthetic derivatives of GM, which may be of interest in the pharmaceutical context. Finally, we discuss the specific applications of GM in the drug delivery field.

Microspheres containing lipid/chitosan nanoparticles complexes for pulmonary delivery of therapeutic proteins

Chitosan/tripolyphosphate nanoparticles have already been demonstrated to promote peptide absorption through several mucosal surfaces. We have recently developed a new drug delivery system consisting of complexes formed between preformed chitosan/tripolyphosphate nanoparticles and phospholipids, named as lipid/chitosan nanoparticles (L/CS-NP) complexes. The aim of this work was to microencapsulate these protein-loaded L/CS-NP complexes by spray-drying, using mannitol as excipient to produce microspheres with adequate properties for pulmonary delivery. Results show that the obtained microspheres are spherical and present appropriate aerodynamic characteristics for lung delivery (aerodynamic diameters around 2-3 microm and low apparent tap density of 0.4-0.5 g/cm3). The physicochemical properties of the L/CS-NP complexes are affected by the phospholipids composition. Phospholipids provide a controlled release of the encapsulated protein (insulin), which was successfully associated to the system (68%). The complexes can be easily recovered from the mannitol microspheres upon incubation in aqueous medium, maintaining their morphology and physicochemical characteristics. Therefore, this work demonstrates that protein-loaded L/CS-NP complexes can be efficiently microencapsulated, resulting in microspheres with adequate properties to provide a deep inhalation pattern. Furthermore, they are expected to release their payload (the complexes and, consequently, the encapsulated macromolecule) after contacting with the lung aqueous environment.

New generation of hybrid poly/oligosaccharide nanoparticles as carriers for the nasal delivery of macromolecules.

We have recently reported a new generation of polysaccharide nanoparticles consisting of chitosan (CS) and cyclodextrin (CD) derivatives, which exhibit a number of advantages when compared to the classical CS nanoparticles. In the present work our goal was to explore the potential of these hybrid CS/CD nanoparticles as carriers for the nasal delivery of macromolecules. First, we evaluated the effect of the amount and type of CD (sulfobutylether-beta-CD or carboximethyl-beta-CD) on the physicochemical properties of the nanocarriers. Second, we investigated the interaction of CS/CD nanoparticles with the nasal epithelium by studying their ability to modulate the tight junctions between epithelial cells (Calu-3 cell model) as well as their capacity to overcome mucosal barriers (nasal epithelium of rats). Finally, we loaded two selected nanocarriers with insulin and studied their potential for enhancing the nasal transport of insulin in rabbits. The results showed that CS/CD nanoparticles caused a reversible reduction in the transepithelial resistance of the cell monolayer, thus increasing the membrane permeability. Moreover, the results obtained following the in vivo administration of fluorescent CS/CD nanoparticles to rats evidenced their capability to overcome the nasal mucosal barrier. Finally, the in vivo evaluation in conscious rabbits revealed that insulin-loaded nanoparticles (association efficiencies > 88%) were able to significantly decrease plasma glucose levels (more than 35% reduction). Overall, these results suggest that these new nanoparticles work as nasal carriers and, therefore, have a potential for enhancing the transport of complex molecules across the nasal barrier.