Drugs delivery systems (DDSs) play important roles in healthcare engineering. However, many systems are hard to efficiently load or deliver the drugs because of the poor encapsulation efficiency, non-targeting, and fast inactivation.

Recently, various novel DDSs have been developed to load, protect and deliver drugs, and have shown excellent therapeutic effects. Among them, DDSs based on hydrogels, which consist of hydrophilic polymer chains by physical or chemical crosslinking, have received increasing attention. These DDSs have great biocompatibility and similar properties to the extracellular matrix, as well as can release drugs in a controlled manner through spontaneous or responsive swelling and shrinking of hydrogels. These features allow the hydrogel-based DDSs to hold excellent prospects in healthcare engineering. Current hydrogel-based DDSs have developed rapidly and focus especially on the following areas. In the aspect of the source of the hydrogels, researchers have explored a series of novel synthetic polymers or modified natural polymers for the fabrication of DDSs, which significantly broadened the choice of raw materials. In the aspect of fabrication strategies, many kinds of technologies, including microfluidics, electrospinning, and 3D printing, have been employed for constructing novel DDSs. Additionally, the response mechanisms of the hydrogels have also been studied. Based on their responsive behaviors, the hydrogels have shown they can release drugs controllably.

This Special Issue invites original research and review articles focusing on the further novel design strategies and applications of hydrogel-based DDSs.

Potential topics include but are not limited to the following:

• Drug delivery hydrogel
• Pharmacokinetics in hydrogel
• Stimuli-responsive polymer
• Natural polymers
• Hydrogel nanoparticles
• Injectable hydrogel
• Drug encapsulation
• Dynamic hydrogel
• Sustained drug release
• Targeted drug delivery