Injectable Block Copolymer Hydrogels: Achievements and Future Challenges for Biomedical Applications

Abstract

In the past two decades, physical polymeric hydrogels have been extensively explored for biomedical applications, such as drug delivery and tissue engineering. These hydrogels exhibit a sol–gel phase transition in response to external stimuli, such as pH, temperature, glucose, electric field, magnetic field, ionic strength, or their combination. Hydrogel precursors can be mixed with bioactive molecules or cells and then simply injected into the body at specific sites. Substantial progress has been made in the development of novel hydrogels and applications. In this Perspective, we report recent progress in physically cross-linked hydrogels responding to pH and/or temperature and their pharmaceutical and tissue engineering applications. The outlook for the future, including remaining challenges of injectable hydrogels, is also discussed.

Light-Triggered RNA Release and Induction of Hmsc Osteogenesis Via Photodegradable, Dual-Crosslinked Hydrogels

“…Bioactive factors and cells can easily be encapsulated within hydrogels for tissue engineering applications [2,5,6,38,[55][56][57][58]. The degradation of hydrogel biomaterial platforms increases their network pore size, which regulates the release of loaded bioactive molecules, creates free space for newly forming tissues and enhances transport of oxygen and nutrients to encapsulated cells as well as removal of metabolic waste.…”

“…Polymeric hydrogel biomaterials are three-dimentional chemically or physically crosslinked hydrophilic polymer networks that can absorb and retain large quantities of water [2,38,[55][56][57][58]. Hydrogels hold great potential in biomedical and pharmaceutical applications because bioactive factors can be encapsulated within them and subsequently delivered in a localized and controlled manner at desired anatomic locations [38,[55][56][57].…”

“…Hydrogels hold great potential in biomedical and pharmaceutical applications because bioactive factors can be encapsulated within them and subsequently delivered in a localized and controlled manner at desired anatomic locations [38,[55][56][57]. For example, they have been employed as depots for the delivery of anticancer drugs [59][60][61], genetic materials [62], and proteins [63][64][65].…”

Sulfamethazine-based pH-sensitive hydrogels with potential application for transcatheter arterial chemoembolization therapy

“…These hydrogels possess several advantages, including electrostatic interaction with therapeutic agents, ease of handling and storage, and the ability to avoid obstructing a long needle or catheter [43][44][45][46][47][48][49][50][51]. Sulfamethazine is an anionic molecule, with a pK a value of 7.4, that has been widely employed to fabricate anionic pH-sensitive hydrogels, which can exhibit a sol-to-gel phase transition in response to lowering environmental pH [52][53][54][55][56].…”

Temperature/pH Responsive Hydrogels Based on Poly(ethylene glycol) and Functionalized Poly(e-caprolactone) Block Copolymers for Controlled Delivery of Macromolecules

“…Introduction of pH sensitive moieties to temperature responsive polymer may, in fact, be used to narrow down the sol-gel transition temperature range of the thermo-gelling material; in other words, make the transition sharper (17). It may also be used to introduce pH sensitive release properties to the developed biomaterials for several diverse application in drug delivery.…”