Abstract
In situ gelling drug delivery systems have gained enormous attention over the last decade. They are in a sol-state before administration, and they are capable of forming gels in response to different endogenous stimuli, such as temperature increase, pH change and the presence of ions. Such systems can be administered through different routes, to achieve local or systemic drug delivery and can also be successfully used as vehicles for drug-loaded nano- and microparticles. Natural, synthetic and/or semi-synthetic polymers with in situ gelling behavior can be used alone, or in combination, for the preparation of such systems; the association with mucoadhesive polymers is highly desirable in order to further prolong the residence time at the site of action/absorption. In situ gelling systems include also solid polymeric formulations, generally obtained by freeze-drying, which, after contact with biological fluids, undergo a fast hydration with the formation of a gel able to release the drug loaded in a controlled manner. This review provides an overview of the in situ gelling drug delivery systems developed in the last 10 years for non-parenteral administration routes, such as ocular, nasal, buccal, gastrointestinal, vaginal and intravesical ones, with a special focus on formulation composition, polymer gelation mechanism and in vitro release studies.
Highlights
In the last decade, the development of in situ gelling drug delivery systems has gained an increasing attention in the scientific community
It is well-known that some anionic polysaccharides (alginate (ALG), gellan gum (GG) and pectin (PEC)) are ion-sensitive polymers [5,6,7,8,9]; they are cross-linked by some monovalent (Na+) and/or divalent (Mg2+ and Ca2+) cations present in different physiological fluids, such as saliva, tears, nasal fluid, etc
This review provides an overview of the advances in the development of in situ gelling drug-delivery systems over the past decade, for non-parenteral administration routes, such as ocular, nasal, buccal, gastrointestinal, vaginal and intravesical ones, taking into account the eventual synergism between gelation and mucoadhesion on the formulation performance
Summary
The development of in situ gelling drug delivery systems has gained an increasing attention in the scientific community The majority of these systems presents the peculiarity to be in a sol-state before administration and to undergo gelation into the body. Thermo-sensitive in situ gelling systems are in a sol-state at room temperature and are subjected to a sol–gel transition at temperature values close to the physiological one (32–37 ◦C, depending on the administration site). Among thermo-sensitive polymers, poly(N-isopropylacrilamide) (PNIPAM), poloxamers (Pluronic®) and cellulose derivatives are the most used in drug delivery It is well-known that some anionic polysaccharides (alginate (ALG), gellan gum (GG) and pectin (PEC)) are ion-sensitive polymers [5,6,7,8,9]; they are cross-linked by some monovalent (Na+) and/or divalent (Mg2+ and Ca2+) cations present in different physiological fluids, such as saliva, tears, nasal fluid, etc. A special focus on formulation composition, polymer gelation mechanism and in vitro release studies is given
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