# Self‐Assembled Polypseudorotaxanes Crosslinked by Dynamic Disulfide Bonds as Modular Functionalization for Thiophilic Metal Nanoparticles

## TL;DR

Scientists created a modular material using self-assembled molecules that can be used to enhance metal nanoparticles for applications like drug delivery.

## Contribution

A new modular platform using thiol-rich polypseudorotaxanes for functionalizing thiophilic metal nanoparticles is introduced.

## Key findings

- SPPR-based hydrogels show photo-responsive gelation and thixotropy with embedded metal nanoparticles.
- Metal nanoparticles wrapped with SPPR exhibit enhanced cancer cytotoxicity via thiol-mediated uptake.

## Abstract

As supramolecular assemblies, polypseudorotaxanes (PPR) exhibit inherent advantages in modular adaptability and structural programmability, with the potential to build tuneable platforms integrating various functionalities. Here we report the “one‐pot” preparation of a self‐assembled thiol‐rich PPR (SPPR), where thiolated‐α‐cyclodextrins (SHαCD) spontaneously thread onto polymers, and are then crosslinked into a three‐dimensional network by the thermally‐triggered oxidation of thiols into disulfide bonds. The dynamic thiol groups along the SPPR provide remarkable modularity for the functionalization of thiophilic metal nanoparticles (NPs), exemplified by two application vectors. First, SPPR were used as building blocks of a thermo‐responsive hydrogel to incorporate thiophilic NPs, where NPs are tethered to the networks and, in turn, reinforce its mechanical properties. The resulting gels, characterized by small‐angle neutron‐scattering and rheology, display photo‐responsive gelation and thixotropy. In the second application, the affinity of metal NPs to the dynamic thiol groups on SPPR was exploited to “wrap” the polymers around the NPs, through simple tuning of concentration and chain length. The flexible polydisulfides layer endows NPs with enhanced cancer cytotoxicity, possibly via the thiol‐mediated uptake pathway. These results establish SPPR as a powerful functionalization platform, offering a promising route toward customized supramolecular materials.

Self‐assembled thiol‐rich polypseudorotaxanes with high modularity were developed via a “one‐pot” preparation through the threading of thiolated α‐cyclodextrins on polymers and subsequent oxidation of thiols into disulfide bonds. This dynamic motif was used as a functionalization platform for thiophilic metal nanoparticles, either tethering them to a photothermal hydrogel or for their surface functionalization with nanoscopic “wrapping”.