Ultrasound-triggered hydrogel formation through thiol–norbornene reactions

Abstract

Ultrasound-initiated thiol-norbornene reaction has been applied to fabricate hydrogels, and the ultrasound conditions in determining the properties of hydrogels have been systematically investigated.

An ultrasound-induced MXene doped PAM–SA super-tough hydrogel

“…31 KPS is a conventional oxidizing initiator in which oxygen–oxygen bonds are broken by heating and split into two corresponding free radicals. 32 The redox reaction between MXene nanosheets and APS under ultrasonic-induction was easily achieved under the ultrasonic-induction. The atom of Ti of Ti 3 C 2 was oxidized to produce free radical TiO 2 − , and the KPS generates a large amount of free radical SO 4 − ˙, which initiates AM polymerization.…”

Ultrasonic interfacial crosslinking of TiO2-based nanocomposite hydrogels through thiol–norbornene reactions for sonodynamic antibacterial treatment

“…76 On the other hand, since intermolecular disulfide links between molecules can be created under ultrasonic treatment, the lower modulus of hydrogels under the conditions of higher frequency (120 kHz) might be associated with radical quantities and the production of disulfide bonds. 53,77…”

“…Norbornene-functionalized dextran (Nor-Dex) was synthesized by conjugating carbic anhydride to the dextran structure under alkaline conditions according to the reported procedure, 53 and the modification percentage of norbornene in Nor-Dex was about 25% (Scheme S1a †). The TiO 2 NPs were coated with a mesoporous silica shell through a sol-gel reaction, 62 where tetraethoxysilane (TEOS) and cetyltrimethylammonium bromide (CTAB) was used as the source of silica and the template, respectively (Scheme S1b †).…”

“…This decrease in the compressive modulus of hydrogels could be attributed to the creation of disulfide bonds between crosslinkers, which hinders the thiol-norbornene reactions and the propagation of hydrogels. 53,72,74,75 The effect of ultrasound frequency on the mechanical properties of the TiO 2 @MS-SH/Nor-Dex NC hydrogels was further investigated. The compressive moduli of the TiO 2 @MS-SH/ Nor-Dex NC hydrogels prepared with ultrasound frequencies of 40, 80, and 120 kHz were 50.46 ± 4.86, 80.64 ± 3.70, and 64.41 ± 5.64 kPa, respectively (Fig.…”

“…In our previous work, norbornene-functionalized dextran (Nor-Dex) was synthesized and crosslinked with dithiothreitol (DTT) through ultrasound-triggered thiol-norbornene reactions for the formation of Nor-Dex hydrogels. 53 Also, the thiol-ene reactions between norbornene and DTT have been well characterized in many reports. [54][55][56] Herein, we aim to extend the utility of the ultrasound-triggered thiol-norbornene reactions for NC hydrogel formation and apply the TiO 2 -based NC hydrogels as an effective sonosensitizing matrix for sonodynamic antibacterial treatment.…”