Abstract
Polymer nanofibers have exceptionally high surface area. This is advantageous compared to bulk polymeric structures, as nanofibrils increase the area over which materials can be transported into and out of a system, via diffusion and active transport. On the other hand, since hydrogels possess a degree of flexibility very similar to natural tissue, due to their significant water content, hydrogels made from natural or biodegradable macromolecular systems can even be injectable into the human body. Due to unique interactions with water, hydrogel transport properties can be easily modified and tailored. As a result, combining nanofibers with hydrogels would truly advance biomedical applications of hydrogels, particularly in the area of sustained drug delivery. In fact, certain nanofiber networks can be transformed into hydrogels directly without the need for a hydrogel enclosure. This review discusses recent advances in the fabrication and application of biomedical nanofiber hydrogels with a strong emphasis on drug release. Most of the drug release studies and recent advances have so far focused on self-gelling nanofiber systems made from peptides or other natural proteins loaded with cancer drugs. Secondly, polysaccharide nanofiber hydrogels are being investigated, and thirdly, electrospun biodegradable polymer networks embedded in polysaccharide-based hydrogels are becoming increasingly popular. This review shows that a major outcome from these works is that nanofiber hydrogels can maintain drug release rates exceeding a few days, even extending into months, which is an extremely difficult task to achieve without the nanofiber texture. This review also demonstrates that some publications still lack careful rheological studies on nanofiber hydrogels; however, rheological properties of hydrogels can influence cell function, mechano-transduction, and cellular interactions such as growth, migration, adhesion, proliferation, differentiation, and morphology. Nanofiber hydrogel rheology becomes even more critical for 3D or 4D printable systems that should maintain sustained drug delivery rates.
Highlights
Definition of Hydrogels and Their ApplicationsA hydrogel is defined as a three-dimensional (3D) network of hydrophilic molecules or polymers that are able to swell in water and retain large amounts of water in their bulk.In such a state, hydrogels can maintain their structure and stability due to chemical or physical cross-linking of individual polymer chains
Most of the drug release studies and recent advances have so far focused on self-gelling nanofiber systems made from peptides or other natural proteins loaded with cancer drugs
This review shows that a major outcome from these works is that nanofiber hydrogels can maintain drug release rates exceeding a few days, even extending into months, which is an extremely difficult task to achieve without the nanofiber texture
Summary
A hydrogel is defined as a three-dimensional (3D) network of hydrophilic molecules or polymers that are able to swell in water and retain large amounts of water in their bulk. (b) A typical DNA hydrogel formation mechanism known as a double-stranded DNA monomer (O1-O2, 30 base pairs and 15 base sticky ends) is generated, which can self-assemble. Widely used hydrogel-forming reactions of natural polymers including DNA. There are several dedicated reviews on each of these natural polymer based hydrogels and more and the readers should consult to them for further details on cross-linking and applications.
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