Supramolecular Hydrogels Made of End-Functionalized Low-Molecular-Weight PEG and α-Cyclodextrin and Their Hybridization with SiO₂ Nanoparticles through Host−Guest Interaction

Abstract

As quite generally stated in the literature, low-molecular-weight (MW) poly(ethylene glycol) (PEG) (M n less than 2K) and α-cyclodextrin (α-CD) can lead to only crystalline precipitates (not hydrogels). However, in this study we found that: (1) adamantane monoend-functionalized low-MW PEG (Ada-PEG, M n= 1.1 or 2K) and α-CD lead to hydrogels but not to crystalline precipitates and (2) β-cyclodextrin (β-CD) surface-functionalized silica nanoparticles (β-CD−SiO2) can be well dispersed in low-MW Ada-PEG and α-CD aqueous mixtures, resulting in hybrid hydrogels. The hydrophobic aggregation of Ada-PEG in case 1 and the further functionalization of β-CD−SiO2 with PEG chains due to the inclusion complexation between β-CD and the Ada group attached to PEG in case 2 were found to play a key role as a supra-crosslink that promoted the gelation of the inclusion complexes of α-CD and the low-MW Ada-PEG. The resultant native and hybrid hydrogels retained the basic characteristics of the supramolecular physical hydrogels, especially the shear-thinning property. The mechanical strength and the viscosity of the hybrid hydrogel were greatly improved in comparison with those of the corresponding native hydrogels.

A three-dimensional graphene oxide supramolecular hydrogel for infrared light-responsive cascade release of two anticancer drugs

“…For our system, the CPT-PEG modified GO sheets act as a core material to anchor a high density of PEG chains on its surface, which provides additional supra-cross-links and steric hindrance partly preventing a-CD to be included on the PEG chains completely. 5b, 13 As shown in Fig. S4 (ESI †), the characteristic peak of CPT-PEG at 23.21 can also be observed for G1 to G4, implying that GO sheets can efficiently prevent the PEG chain from being covered by a-CD completely.…”

Review: Bioanalytical applications of biomolecule-functionalized nanometer-sized doped silica particles

“…An unwanted consequence, for example, of functionalization with amine-containing silanes is that the colloidal stability may decrease, and particles may aggregate in water (caused by a reduction in the overall charge of the particle at neutral pH). This problem could be resolved using the addition of inert negatively charged silanes, which contain phosphonate (e.g., (3-trihydroxy)silylpropyl methylphosphonate, THPMP) or other groups [125,126]; alternatively, PEGylated silanes may be added, which are highly hydrophilic [127][128][129]. A novel precision-assembly methodology based on the controlled, simultaneous assembly of a core nanoparticle substrate in a polyelectrolyte solution (polyethyleneimine) was recently described by Bringley et al [130].…”

Dual Stimuli-Responsive Supramolecular Hydrogel Based on Hybrid Inclusion Complex (HIC)

“…15 Such hybrid hydrogels are reported to have useful mechanical, optical, or magnetic properties. 16,17 Harada et al 18 prepared hybride hydrogel through CD-functionalized carbon nanotube. Our group introduced β-CD-modified SiO 2 nanoparticle as a supra-cross-link to poly(ethylene glycol) (PEG), which promotes the formation of hybrid hydrogel.…”