Abstract
As a natural polysaccharide, chitosan has good biocompatibility, biodegradability and biosecurity. The hydroxyl and amino groups present in its structure make it an extremely versatile and chemically modifiable material. In recent years, various synthetic strategies have been used to modify chitosan, mainly to solve the problem of its insolubility in neutral physiological fluids. Thus, derivatives with negative or positive fixed charge were synthesized and used to prepare innovative drug delivery systems. Positively charged conjugates showed improved properties compared to unmodified chitosan. In this review the main quaternary ammonium derivatives of chitosan will be considered, their preparation and their applications will be described to evaluate the impact of the positive fixed charge on the improvement of the properties of the drug delivery systems based on these polymers. Furthermore, the performances of the proposed systems resulting from in vitro and ex vivo experiments will be taken into consideration, with particular attention to cytotoxicity of systems, and their ability to promote drug absorption.
Highlights
The current research in the field of controlled drug delivery systems has been focused on the use of polymeric materials
The method frequently used to assess the antioxidant activity of quaternary ammonium derivatives is the 2,2-diphenyl-1-picrylhydrazyl hydrate (DPPH) radical scavenging assay that is based on the measurement of the scavenging capacity of antioxidants [126]
DPPH method has undergone various modifications, but the basic approach remains the same: the compound under analysis is mixed with a DPPH solution and the absorbance, measured colorimetrically, is directly related to the antioxidant activity
Summary
The current research in the field of controlled drug delivery systems has been focused on the use of polymeric materials. It is known that [5], evenbutslight through stratified epithelia suchinas the buccal [6,7], vaginal [7] and tissue physical-chemical differences polymer backbone arecorneal reflected in [8,9,10,11] For all these characteristics, chitosan has been used for the preparation of conventional differences concerning, for example, cellular absorption, the biological processes that regulate this pharmaceutical systems (e.g., solutions, suspensions, emulsions, etc.). That drug release systems systems based on chitosan and systems its derivatives promote the absorption and the pharmacologic and therapeutic application of is limited its insolubility biodistribution of drugs in a manner strictly dependent on thechitosan properties of theby polymer These in water and in most solvents. A great deal of different chitosanDerivatives: derivatives,Principal includingCharacteristics acylated, alkylated, carboxylated and
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