Cross-Linked PEG via Degradable Phosphate Ester Bond: Synthesis, Water-Swelling, and Application as Drug Carrier

Abstract

A new series of degradable and water-swellable cross-linked PEG phosphoester polymers (CPPs) based on a facile cross-linked reaction between diphosphoesters of polyethylene glycol (P-PEG-P) and diglycidyl ether of polyethylene glycol (E-PEG-E) has been prepared and characterized. The molecular weights and ratios of the prepolymers played an important role for the properties of CPPs polymers, such as mechanical property, swelling, and degradation rates. In the curing process, the glycidyl ether was consumed by both hydroxyl of the phosphoester (P-OH) and hydroxyl generated from the opened glycidyl ethers (C-OH) with the presence of acid, which generated degradable phosphate esters as cross-linked points and ether bonds as the short branches, respectively. Drug entrapment and release test and biological cytotoxicity studies in vitro suggested that the polymers and generated hydrogels have great potential applications in drug delivery system and biological materials.

Preparation and properties of hydrogels based on PEG and isosorbide building blocks with phosphate linkages

“…A similar phenomenon was noted by Zhu et al in their study of hydrogels based on phosphate linkages [19,20]. The initial hydrolysis would first result in a decrease in the crosslink density of the hydrogel which enabled the gel to absorb more water until reaching a maximum swelling.…”

“…Another advantage of phosphate based hydrogels is the decreased sol-gel temperature. Cheng [19]. In another study, they reacted polycaprolactone (PCL) phosphate ester with epoxidized vegetable oils to form an elastomer for potential biomedical application [20].…”

The influence of diffusion time on the properties of sequential interpenetrating PEG hydrogels

“…The increase could be a result of higher diffusion rate of the mobile ethanol molecules in comparison with the PEG-red-2k and which enable the primary network to undertake a larger mesh size. 30 After 44 h of diffusion, the PEG-red-2k reaches concentrations of 53.3 mg/mL which is below the initial solution concentration. For the diffusion of PEG-red-8k, equilibrium was found after 28 h for the semi-2-8.…”

“…[28][29][30] Parameters that influence these properties include the type of monomer or polymer, the nature and ratio of the crosslinking molecules, the efficiency of crosslinking chemistry, and the introduction of secondary networks templated from already prepared primary networks. The latter was recently reported by our group on sequentially interpenetrating network (SeqIPN) PEG hydrogels via UV initiated TEC chemistry.…”

Reactions of H3PO4 forming polymers. Apparently simple reactions leading to sophisticated structures and applications

“…In a recently published work [98], gels similar to those described by Kazanskii The reaction proceeds as described in papers on reaction of oxiranes with phosphoric acid. The resulting gels are complex crosslinked networks and, as indicated by Zhu et al, the Young's modulus was up to 4.0 MPa [98].…”