Dear Colleagues, 

We would like to invite you to contribute research papers to the Special Issue entitled “Advances in the Design of Hydrogels for Therapeutic Agent and Cell Delivery”.

Hydrogels are three-dimensional networks made of water-soluble polymeric chains, with the ability to undergo swelling in physiological conditions without dissolution. Hence, they are a wide-ranging class of materials as they can be virtually prepared from any types of natural or synthetic water-soluble polymers. A hydrogel polymeric network can be stabilized via physical interactions (e.g., electrostatic interactions or hydrogen bonds) or chemical crosslinks (e.g., photo-induced crosslinking, enzyme-driven crosslinking, click-chemistry crosslinking among the polymeric chains, addition of chemical crosslinkers, etc.). Additionally, hydrogels can be prepared in a wide variety of physical forms, including slabs, microparticles, nanoparticles, coatings, fibers, scaffolds and films. Injectable hydrogels can also be designed with the ability to undergo sol-to-gel transition in vivo through specific mechanisms (e.g., click-chemistry crosslinking, photo crosslinking, pH- or temperature-induced gelation, etc.).

In regenerative medicine, hydrogels are particularly effective for sustained and controlled drug delivery. Indeed, hydrogels allow a spatial and temporal control in the release of various therapeutic agents, including small-molecule drugs, macromolecular drugs, oligonucleotides and drug-loaded micro/nanoparticles. Due to their tunable physical properties (e.g., mesh size and swelling ability), controllable degradability (e.g., mediated by protease-cleavable peptide sequences) and capability to protect drugs from degradation, hydrogels represent versatile platforms that can be exploited as cell or agent depots for controlled, active therapeutic release.

In this Special Issue, we cover new advances in the design of hydrogels as drug delivery systems, focusing on the physical and chemical properties of the hydrogel network and hydrogel–drug interactions across the network, mesh and molecular scales. Special attention is dedicated both to “bio-orthogonal” hydrogels for cells encapsulation and/or in vivo injection, as well as to smart hydrogels provided with triggering mechanisms for a fine control in time and space over drug release.

Recently, non-viral gene therapy attracted a broad interest by the scientific community for its ability to treat a range of diseases, including neurodegenerative, cardiovascular, rare disorders, and cancer, etc. However, considering that naked oligonucleotides are not internalized by cells due to their negative charge and sensitivity to enzymatic degradation, nanocarriers are generally used to convey them into target cells. In this Special Issue, we will also collate reviews or original research articles on the design of hydrogels as depots for the local release of oligonucleotide-loaded nanoparticles, in order to achieve their efficient and controlled local release.

Another advanced topic is represented by the paracrine stimulation of extracellular vesicles derived from cells, which can be encapsulated into hydrogels for controlled in vivo release to achieve different functions, including pro-angiogenetic, anti-inflammatory and anti-fibrotic activities. This Special Issue will also collect review or research articles on the design of hydrogels for the release of extracellular vesicles and their preclinical validation.

Finally, other topics of interest include: the bioprinting or electrowriting of hydrogel scaffolds for drug release and stimuli-sensitive, drug-releasing hydrogels.

The final aim of this Special Issue is to provide readers with an overview of the most recent progress in drug-releasing hydrogels, and guidelines for a rational design of hydrogel delivery systems. 

Prof. Dr. Valeria Chiono
Prof. Dr. Jochen Salber
Dr. Alice Zoso
Dr. Irene Carmagnola
Guest Editors

Manuscript Submission Information

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• Click-chemistry
• Injectable hydrogels
• Photo-crosslinking
• Natural polymers
• Synthetic polymers
• Oligonucleotide release
• Nanoparticle release
• Bioprinting
• Electrowriting