Biomedical Engineering Reference
In-Depth Information
7.3 Drug Loading into Chitosan-Based Drug Delivery Systems
Loading drug into chitosan-based drug delivery systems can be achieved in two steps:
during the preparation of carriers (incorporation) and after the formation of carriers (incu-
bation). In these systems, drug is physically embedded into the matrix or adsorbed onto
the surface. Various methods of loading have been developed to improve the efficiency of
loading, which largely depends on the method of preparation, as well as physicochemical
properties of the drug. Maximum drug loading can be achieved by incorporating the drug
during the formation of carriers, but it may get affected by the process parameters such as
the method of preparation, presence of additives, and so on.
Both water-soluble and water-insoluble drugs can be loaded into chitosan-based partic-
ulate systems. Water-soluble drugs are mixed with a chitosan solution to form a homoge-
neous mixture and then carriers can be produced by any of the methods discussed
before. Water-insoluble drugs and drugs that can precipitate in acidic pH solutions can
be loaded after the formation of carriers by soaking the preformed particles with the
saturated solution of the drug.
7.4 Pharmaceutical Applications of Chitosan-Based Drug
Delivery Systems
Chitosan and its derivatives have been widely studied for drug delivery. Some of the bio-
medical applications of chitosan-based gels discussed in the following sections include
large-molecule drug delivery (protein and peptide delivery, enzyme delivery, gene delivery,
and vaccines delivery), ocular, oral, mucosal, and pulmonary drug delivery.
7.4.1 large-Molecule Drug Delivery
7.4.1.1 Protein and Peptide Delivery
Advanced research in biotechnology and genetic research has led to the discovery of a
large number of proteins and peptides that are very effective in disease treatment [18,19].
Routinely, peptides and proteins are administered through the parenteral route, which has
poor absorption efficiency in patients. A large amount of work has focused on protein
delivery by the oral route [20-22]. However, the bioavailability of peptide after oral admin-
istration is usually low because of instability and poor absorption of proteins in the gastro-
intestinal (GI) tract. One possible way to improve the GI uptake of peptides is to encapsulate
them in colloidal nanoparticles that can protect the peptide from being degraded in the GI
tract and facilitate their transportation into systemic circulation [23].
Chitosan-based gels and their ramifications have important applications in the controlled
release of protein and peptide drugs because they show excellent mucoadhesiveness [24] and
a permeation-enhancing effect across the biological surfaces. Superoxide dismutase, the most
potent antioxidant enzyme, has been encapsulated into chitosan microparticles to obtain suit-
able sustained protein delivery based on the complex coacervation process. The addition of
polyethylene glycol to the protein solution or a change of pH enhanced the encapsulation
efficiency for controlled release [25]. Luteinizing hormone-releasing hormone (LH-RH),
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