Biodegradable Polyester Thermogelling System as Emerging Materials for Therapeutic Applications

Abstract

In situ forming hydrogels are systems responsive to the environmental stimuli, such as change of temperature, pH, photo intensity, ionic strength, etc. [14,15] They have been divided into two types, one is chemical in situ gels and the other is physical in situ gels. Chemical in situ gels, also called "permanent" gels, are hydrogels containing covalently cross-linked networks. They are irreversible polymeric networks via the use of cross-linkers or enzymes. [16] Physical in situ gels, or "reversible" gels, are those networks held together by molecular entanglements and secondary forces such as hydrogen bonding, ionic, hydrophobic forces. [17,18] Usually these weak and reversible bonds formation depends on external stimulation to form cross-linking, which makes temperature, pH, lights, or ions sensitive reversible hydrogels possible. [19][20][21][22] In situ delivery systems have an upper hand compared with conventional systems, because they take longer time for in situ system to finish releasing drug at targeted site. Particularly, a temperature responsive hydrogel, namely thermogel, is a reversible physical cross-linking system, forming upon heating up temperature until critical temperature. The properties of thermogel offer opportunities in therapeutic application because of several reasons. [23][24][25] An injectable thermogel system has simplicity of pharmaceutical formulation by mixing of drug below sol-gel transition temperature. Large scale surgery for implantation is not needed. After injection, body temperature will stimulate sol-gel transition, viscous solution will change into a drug delivery depot. The high percentage water content makes thermogel highly competitive with the injection site. Also, peptides are kept at low temperature before application, which makes sure no denaturalization due to organic solvent interaction or dissolution triggered by high temperature.Currently, there are only two types of commercial polymeric thermoresponsive hydrogel products available in the market. One is Poloxamer, and the other is poly(N-isopropyl acrylamide) (PNIPAAm). When using Poloxamer based hydrogel, two conditions, polymer critical micelle concentration (CMC) and critical micelle temperature (CMT), must be reached to promote sol-gel transition. For Poloxamer, it includes Amphipathic Poloxamer and Pluronic F127. Amphipathic Poloxamer, a FDA-approved triblock polymer, composes of hydrophobic poly(ethylene oxide) and hydrophilic poly(propylene oxide) components. [26] Hydrogel based on this has been widely used in both therapeutic and consumer applications. Although Amphipathic Poloxamer has proven to be biocompatible and able to perform drug delivery, [27] degradation of it based hydrogels does not support sustainable Therapeutic Applications Polyesters comprise the earliest and most extensive investigation as biomaterials. The integration of polyester into thermogelling system is one of the most recent trends in the development of hydrogel research. In this review, the most recent development of polyester ba...

A Recent Perspective on Noncovalently Formed Polymeric Hydrogels

“…The main issue with these methods is that the covalent networks formed are more permanent. It is more difficult to induce huge changes in hydrogel properties within an unchanging covalent framework . Therefore, to allow for dynamic changes in the hydrogel, for example for cell spreading and migration, polymer degradation is often necessary .…”

Mechanism of Reduced Muscle Atrophy via Ketone Body (D)-3-Hydroxybutyrate

“…Therefore, our study lays a bene cial foundation for future space explorers and the aging populations. From the hydrolysis products of biocompatible implanted PHB biomaterial point of view, our study also provides values for the therapeutic applications in tissue engineering and drug delivery [90,91,92]. Studies on engineered microbes and synthetic biology for the production of 3HB may have practical applications and high market values in the healthcare eld [93,94].…”

Functionalized polyesters derived from glycerol: Selective polycondensation methods toward glycerol‐based polyesters by different catalysts

“…In recent years, the synthesis of degradable polyesters with renewable resources has increasingly attracted the attention of researchers . Biodegradable polymers and bio‐based materials have begun to be investigated as alternative products to substitute for nondegradable conventional polymers in packaging and biomedical applications.…”