Synthesis and characterization of a pH-responsive poly(ethylene glycol)-based hydrogel: acid degradation, equilibrium swelling, and absorption kinetic characteristics

Abstract

We developed a pH-responsive, hydrogel based on poly(ethylene glycol) (PEG) covalently cross-linked with acrylic acid and N′,N′-dimethylacrylamide along with acidlabile groups. In the hydrogel, PEG plays a role as the key constituent. If its chains break, the polymer networks are destroyed. The pharmacological potential of these hydrogels were demonstrated by determining their water transport profile, modulus of elasticity, and cytotoxicity assay. The hydrogels showed a pseudo-Fickian behavior, a transport mechanism that occurs when the diffusion coefficient changes with the time and the swelling equilibrium is never fully reached. At pH 2, the PEG-richer hydrogels degraded and the scanning electron microscopy (SEM) images illustrated less-defined shapes than at pH 7 and 10. This morphological characteristic results of the hydrogel deconstruction owing to cleavage of ether bonds of the PEG chains unmaking its 3D polymer network. The proposed hydrogels were shown to be compatible to cells, indicating acceptable biocompatibility and an appropriate level of security for use in the biological environments. Furthermore, they showed structural changes in their polymer network in response to pH, which is an important characteristic for stimuli-triggered release of guest molecules.

Bionanocomposites based on mesoporous silica and alginate for enhanced drug delivery

“…The HGs and nanocomposites showed values of n < 0.5, which suggests pseudo-Fickian water diffusion mechanism. Such a mechanism is found when the time needed to achieve equilibrium swelling is very long (Curcio et al, 2013;Tenório-Neto et al, 2015). Parameter k w from Weibull model is associated with the time in which HG reaches the equilibrium swelling.…”

Synthesis and drug release profile of a dual-responsive poly(ethylene glycol) hydrogel nanocomposite

“…The experimental conditions for PEG modication as well as for hydrogel synthesis were performed according to our previous work. 12 Briey, 16 g of PEG (16 mmol) were added to 80 mL of water at 50 C while stirring. The pH of the mixture was adjusted to pH 10.5 with addition of NaOH pellets.…”

“…It has been reported that ester groups from GMA PEG structure may be cleaved, particularly in acid media, contributing to erosion mechanism. 12 On the other hand, the presence of polyacrylic acid in the hydrogel network plays a predominant role on swelling prole. The pK a of polyacrylic acid is ca.…”

“…11 It can be easily converted into a macromere (or cross-linking agent) by reacting its two hydroxyl-end groups with other reactive groups, such as methoxyl, carboxyl, amine, thiol, azide, vinyl sulfone, azide, acrylate, and so on. 12 This work aimed at synthetizing a PEG-based hydrogel with a dual-responsive behavior (pH-and magnetic-responsive) as a platform for drug delivery. Prednisolone was the drug model.…”

Mechanical Properties and Moisture Transport Behavior of Acid-Sensitive Hydrogels

“…Many of these pH responsive hydrogels have been used in medical applications, especially for drug delivery systems. The pharmacological potentials for the pH sensitive hydrogels were demonstrated by determining their water transport profile, mechanical properties, and cytotoxicity assay. − Acid sensitive micro- or nanosized cross-linked hydrogel networks have also been designed and described for various biomedical applications, including living cell encapsulation, tissue engineering, and stimuli responsive controlled delivery of bioactive molecules. − …”