Sol‐Gel‐Sol Transition of Gold Nanoparticle‐Based Supramolecular Hydrogels Induced by Cyclodextrin Inclusion

Abstract

Hydrogel systems are attractive for different biomedical applications because of their favorable biocompatibility, such as controlled drug delivery and tissue engineering.[1] A number of examples of temperature-, light-, and pH-responsive hydrogel systems have been reported. [2] On the other hand, gold nanoparticles (GNPs) have also attracted much scientific and technological attention due to their excellent physical and chemical characteristics. For example, they are used for tracing cellular biological samples, manipulation of DNA and other biomolecules and enhancing of antimicrobial activities.[3] Therefore, it is highly valuable to combine hydrogels and GNPs together to construct supramolecular hydrogels for biology and medical applications. For instance, GNPschitosan nanocomposite gels are used for immobilization and electrochemical studies of K562 leukemia cells as a bio-inspired support.[4]Herein, we report a facile preparation of novel GNP-based supramolecular hydrogels and their sol-gel-sol transition. The hydrogel is constructed from a triblock copolymer, Pluronic F127, that is, poly(ethylene oxide) 100 -(propylene oxide) 70 -(ethylene oxide) 100 (PEO 100 -PPO 70 -PEO 100 ), mono-6-thio-b-cyclodextrins (SH-b-CDs), and GNPs. The SH-b-CDs couple to the GNPs via thio-groups and include PPO blocks of F127 to form pseudo-polyrotaxanes. Although Li et al. have reported that Pluronics and a-CDs could form hydrogels, which are driven by the micro-crystallization of inclusion complexes of a-CD and PEO blocks and the micellization of the PPO blocks, [5] the study presented here is a distinct design route using both physical and chemical interactions. Moreover, such supramolecular hydrogels show potential for use as drug carriers to realize drug-upload in solution, drug-carry in the gel, and drug-unload in the final solution phase.The GNPs colloidal dispersions were prepared by reducing AuCl 4 À with citrate according to the well-known method established by Freeman and Natan.[6] The obtained GNPs are nearly monodisperse with the average diameter of 10.1 nm (see Figure S1 in Supporting Information) as determined by transmission electron microscopy (TEM) and UV/Vis spectroscopy (Figures 1 A and 1B). The supramolecular hydrogels were prepared by adding newly prepared SH-b-CDs (0.05 g, 0.043 mmol) to the mixture of GNPs solution (0.85 mL) and F127 (0.15 g, 0.012 mmol). As shown in Figure 1 C, the viscosity of the ternary system increases gradually during mixing, until the formation of a red-brown gel. On addition of 1-adamantanamine hydrochloride (AdCl) powder (0.0082 g, 0.043 mmol), the gel becomes a homogenous solution again following penetration of AdCl molecules. UV/Vis spectroscopy (see Figure S2 in Supporting Information) showed that the GNPs had no distinct aggregation after the AdCl was added.It is well-known that a water-rich solution region (L 1 phase) is found at 15 wt % F127 and 85 wt % H 2 O. [7] This concentration was thus chosen to eliminate the possible disturbance of hydrogel formation between F127 a...

The Construction and Transition of Supramolecular Hydrogels Induced by Cyclodextrin Inclusion

“…Mono‐6‐deoxy‐6‐( p ‐tolylsulfonyl)‐β‐CD (6‐OTs‐β‐CD) and SH‐β‐CD were synthesized as described in Ref. , and 1 H NMR verified the synthesis of β‐CD derivates (Figure S1, Supporting information).…”

The synthesis of mono-6-thio-β-cyclodextrin capped CdTe QDs and its interaction with neutral red

“…The appearance of the isosbestic point in the absorption spectra of the interaction of (mono-6-thio--CD)-CdTe QDs with neutral red indicated that HNR + didn't form aggregates on the surface of (mono-6-thio--CD)-CdTe QDs. NR formed the inclusion complex with S--CD on the surface of (mono-6-thio--CD)-CdTe QDs [23] which made the equilibrium between HNR + and NR shift towards NR. On the surface of (mono-6-thio--CD)-CdTe QDs appeared charge neutralization occurred due to the combination of HNR + with SCH 2 COO on the surface of (mono-6-thio--CD)-CdTe QDs.…”

“…The synthesis of mono-6-thio--CD [23] -Cyclodextrin (70.0 g, 62 mmol) was suspended in water (550 mL), and NaOH (6.6 g, 165 mmol) in water (20 mL) was added dropwise over 6 min. The suspension became homogeneous and slightly yellow before the addition was complete.…”

Metal Nanoparticles and Supramolecular Macrocycles: A Tale of Synergy

“…Chen et al. reported the preparation of gold‐nanoparticle‐based supramolecular hydrogels induced by cyclodextrin inclusion 36. The thio‐β‐CDs, covalently adsorbed on Au nanoparticles, formed inclusion complexes with the propylene oxide (PPO) blocks of Pluronic F127, giving rise to a network structure.…”