Physical hydrogels with self-assembled nanostructures as drug delivery systems

Abstract

Introduction: As an essential complement to chemically crosslinked hydrogels, drug delivery systems based on physical hydrogels with self-assembled nanostructures are gaining increasing attention, owing to potential advantages of reduced toxicity, convenience of in situ gel formation, stimuli-responsiveness, reversible sol-gel transition, and improved drug loading and delivery profiles.

Areas covered: In this review, drug delivery systems based on physical hydrogels are discussed according to their self-assembled nanostructures, such as micelles, layer-by-layer constructs, supramolecular inclusion complexes, polyelectrolyte complexes and crystalline structures. The driving forces of the self-assembly include hydrophobic interaction, hydrogen bonding, electrostatic interaction, π–π stacking and weak van der Waals forces. Stimuli-responsive properties of physical hydrogels, including thermo- and pH-sensitivity, are considered with particular focus on self-assembled nanostructures.

Expert opinion: Fabricating self-assembled nanostructures in drug delivery hydrogels, via physical interactions between polymer–polymer and polymer–drug, requires accurately controlled macro- or small molecular architecture and a comprehensive knowledge of the physicochemical properties of the therapeutics. A variety of nanostructures within hydrogels, with which payloads may interact, provide useful means to stabilize the drug form and control its release kinetics.

Keywords::

• crosslinking
• hydrogel
• nanostructure
• pH-sensitive
• physical hydrogel
• polyelectrolyte
• self-assembly
• thermo-sensitive

Notes

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