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Novel Hydrophilic Chitosan–Polyethylene Oxide Nanoparticles as Protein Carriers

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Novel Hydrophilic Chitosan–Polyethylene Oxide
Nanoparticles as Protein Carriers
´ PEZ, J. L. VILA-JATO, and M. J. ALONSO*
˜ A´N-LO
P. CALVO, C. REMUN
Department of Pharmacy and Pharmaceutical Technology, School of Pharmacy, University of Santiago de Compostela,
15706 Santiago de Compostela, Spain

SYNOPSIS

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.
᭧ 1997 John Wiley & Sons, Inc.

INTRODUCTION
The development of hydrophilic nanoparticles as
drug carriers has represented over the last few
years an important challenge. Among the different approaches, polyethylene oxide (PEO) –polylactic acid (PLA) nanoparticles have been revealed as very promising systems for the intravenous administration of drugs.1 Due to the creation
of a PEO sterically stabilizing layer, these nanospheres avoid the rapid clearance from the
blood stream, thus allowing an improved delivery
of the drug. Besides this important feature, these
hydrophobic–hydrophilic nanoparticles have a
limitation in their preparation procedure which
requires the use of organic solvents as well as
sonication or homogenization. We present in this
paper a new approach to create biodegradable na-

* To whom correspondence should be addressed.
Journal of Applied Polymer Science, Vol. 63, 125 – 132 (1997)
᭧ 1997 John Wiley & Sons, Inc.
CCC 0021-8995/97/010125-08

noparticles made solely of hydrophilic pol...
Novel Hydrophilic ChitosanPolyethylene Oxide
Nanoparticles as Protein Carriers
P. CALVO, C. REMUN
˜
A
´
N-LO
´
PEZ, J. L. VILA-JATO, and M. J. ALONSO*
Department of Pharmacy and Pharmaceutical Technology, School of Pharmacy, University of Santiago de Compostela,
15706 Santiago de Compostela, Spain
SYNOPSIS
Hydrophilic nanoparticulate carriers have important potential applications for the ad-
ministration of therapeutic molecules. The recently developed hydrophobichydrophilic
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 prepara-
tion of nanoparticles made solely of hydrophilic polymers is presented. The preparation
technique, based on an ionic gelation process, is extremely mild and involves the mix-
ture 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
(2001000 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 nanopar-
ticles 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.
1997 John Wiley & Sons, Inc.
INTRODUCTION
noparticles made solely of hydrophilic polymers.
The major components of these nanoparticles are
PEO, the block copolymers polyethylene oxide The development of hydrophilic nanoparticles as
drug carriers has represented over the last few polypropylene oxide (PEOPPO) , and the poly-
saccharide chitosan (CS). PEO and PEOPPOyears an important challenge. Among the differ-
ent approaches, polyethylene oxide (PEO) poly- are nonionic polymers or diblock copolymers, re-
spectively, which have been shown to be beneficiallactic acid (PLA) nanoparticles have been re-
vealed as very promising systems for the intrave- in improving the hemocompatibility of polymeric
biomaterials.
2
On the other hand, the cationicnous administration of drugs.
1
Due to the creation
of a PEO sterically stabilizing layer, these na- polysaccharide CS has some important properties
such as mucoadhesivity,
3
biocompatibility, andnospheres avoid the rapid clearance from the
blood stream, thus allowing an improved delivery nontoxicity,
4,5
which render it an interesting bio-
material. From a physicochemical point of view,of the drug. Besides this important feature, these
hydrophobichydrophilic nanoparticles have a CS has the special quality of gelling upon contact
with anions thus allowing the formation of beadslimitation in their preparation procedure which
requires the use of organic solvents as well as under very mild conditions.
6,7
These CS beads
showed a pH-dependent swelling behavior whichsonication or homogenization. We present in this
paper a new approach to create biodegradable na- makes them appropriate for the delivery of drugs
in the gastric cavity. Nevertheless, due to their
large size (1–2 mm), these beads are not appro-
priate for other routes of administration, such as
* To whom correspondence should be addressed.
those which require injection or deposition in mu-
Journal of Applied Polymer Science, Vol. 63, 125132 (1997)
1997 John Wiley & Sons, Inc. CCC 0021-8995/97/010125-08
cosal surfaces (nasal, mucosal ). The reduction of
125
3805/ 8E70$$0006 07-31-97 13:41:35 polaa W: Poly Applied
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