Supported Catalytically Active Supramolecular Hydrogels for Continuous Flow Chemistry

Abstract

Inspired by biology, one current goal in supramolecular chemistry is to control the emergence of new functionalities arising from the self‐assembly of molecules. In particular, some peptides can self‐assemble and generate exceptionally catalytically active fibrous networks able to underpin hydrogels. Unfortunately, the mechanical fragility of these materials is incompatible with process developments, relaying this exciting field to academic curiosity. Here, we show that this drawback can be circumvented by enzyme‐assisted self‐assembly of peptides initiated at the walls of a supporting porous material. We applied this strategy to grow an esterase‐like catalytically active supramolecular hydrogel (CASH) in an open‐cell polymer foam, filling the whole interior space. Our supported CASH material is highly efficient towards inactivated esters and enables the kinetic resolution of racemates. This hybrid material is robust enough to be used in continuous flow reactors, and is reusable and stable over months.

Autonomous Growth of a Spatially Localized Supramolecular Hydrogel with Autocatalytic Ability

“…Self-Assembly of Peptide HC atalyzes the Production of Hb y Hydrolysis of the Precursor HE 2 Recently we have shown that heptapeptides H,t hat is, Fmoc-GFFYGHY,e xhibit ac atalytic activity when they are self-assembled resulting in hydrogel formation that efficiently catalyzes the hydrolysis of al arge panel of non-activated esters, [23] af eature barely reported in the literature for selfassembled catalytic systems. [28][29][30][31][32] Indeed, all classes of ester are catalytically transformed into their corresponding carboxylic acid by using this catalytically active supramolecular hydrogel (CASH).…”

“…HP 2 is aw ater-soluble peptide that does not self-assemble and exhibits no catalytic activity.T he amount of H peptide released from HP 2 can be tuned by using AP because this enzymatic action allows acomplete generation of H.W ethus mixed HP 2 , AP,and HE 2 by keeping the concentration of HE 2 constant at 7.6 mm and by decreasing the concentrations of both HP 2 and AP from 790, 79, 7.9, 0.79 mm and 5.9, 0.59, 0.059, 0.0059 mm, respectively.W efollowed the conversion of HE 2 into H over time by HPLC (Figures 2a and S2). A concentration of 10 mg mL À1 for HE 2 was chosen because it corresponds to the critical gelation concentration (CGC) of H. [23] In all cases,t he in situ generation of H is formed with decreasing kinetics when the concentrations of AP and HP 2 are reduced:f or the lower concentration of AP and HP 2 , The precursor HP 2 is enzymatically dephosphorylated by AP leading to the self-assembly of the hydrogelator H.F rom the resulting assembly emerges an esterase-like activity efficient enough to hydrolyze HE 2 into H,s elf-sustaining the growth of the catalytic material.…”

“…This evolution takes place at the same time as ahuge increase of the dissipation factors.Both behaviors are symptomatic of hydrogel formation. [23,25,26] It must be noted that despite the fact that the HE 2 concentration is 10 times lower than the CGC needed in the bulk to obtain ahydrogel, hydrogelation occurs from the AP-modified surface.T he amount of hydrogel formed from the enzymatic multilayer is dependent on the concentration of HE 2 solution brought into contact with the film:decreasing this concentration from 0.76, 0.53, 0.38, 0.15, and 0.076 mm decreases concomitantly the mass of hydrogel generated according to QCM-D measurements (Figure 4d). When 0.76 mm of HE 2 is used, the thickness of the resulting hydrogel layer reaches % 18 mma ccording to cryo-SEM analysis (Figure 4e).…”

“…We have designed an original amphiphilic diester heptapeptide HE 2 (H = hydrogelator, E = ester, Figure 1a)t hat lacks catalytic activity,b ut once both ester groups are hydrolyzed the remaining hydrogelator H self-assembles leading to as upramolecular hydro-gel that possesses highly efficient esterase-like activity. [23] The self-sustained growth of the catalytic hydrogel is initiated by generating traces of H in the chemical system in situ thanks to an enzymatic action. Thec hoice of an enzyme trigger is motivated by several advantages:1 )enzymes are the most efficient class of catalysts that allow ar apid production of H and accurate regulation of its concentration, initiating the gelation process by using very few enzymes;2 )enzymes can be spatially localized through grafting methods to provide localization of H generation [24] and thus of the hydrogel growth.…”

Autonomous Growth of a Spatially Localized Supramolecular Hydrogel with Autocatalytic Ability

“…HP 2 is aw ater-soluble peptide that does not self-assemble and exhibits no catalytic activity.T he amount of H peptide released from HP 2 can be tuned by using AP because this enzymatic action allows acomplete generation of H.W ethus mixed HP 2 , AP,and HE 2 by keeping the concentration of HE 2 constant at 7.6 mm and by decreasing the concentrations of both HP 2 and AP from 790, 79, 7.9, 0.79 mm and 5.9, 0.59, 0.059, 0.0059 mm, respectively.W efollowed the conversion of HE 2 into H over time by HPLC (Figures 2a and S2). A concentration of 10 mg mL À1 for HE 2 was chosen because it corresponds to the critical gelation concentration (CGC) of H. [23] In all cases,t he in situ generation of H is formed with decreasing kinetics when the concentrations of AP and HP 2 are reduced:f or the lower concentration of AP and HP 2 , The precursor HP 2 is enzymatically dephosphorylated by AP leading to the self-assembly of the hydrogelator H.F rom the resulting assembly emerges an esterase-like activity efficient enough to hydrolyze HE 2 into H,s elf-sustaining the growth of the catalytic material. Angewandte Chemie (5.9 nm and 0.79 mm, respectively), the transformation of HE 2 into H starts significantly after 27 hours and then the transformation accelerates in asimilar manner to anucleation and growth process (Figure 2a).…”