Multi-responsive hydrogels derived from the self-assembly of tethered allyl-functionalized racemic oligopeptides

Abstract

A multi-responsive triblock hydrogelator oligo(dl-allylglycine)-block-poly(ethylene glycol)-block-oligo(dl-allylglycine) (ODLAG-b-PEG-b-ODLAG) was synthesized facilely by ring-opening polymerization (ROP) of DLAG N-carboxyanhydride (NCA) with a diamino-terminated PEG as the macroinitiator. This system exhibited heat-induced sol-to-gel transitions and either sonication- or enzyme-induced gel-to-sol transitions. The β-sheeting of the oligopeptide segments was confirmed by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and wide-angle X-ray scattering (WAXS). The β-sheets further displayed tertiary ordering into fibrillar structures that, in turn generated a porous and interconnected hydrogel matrix, as observed via transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The reversible macroscopic sol-to-gel transitions triggered by heat and gel-to-sol transitions triggered by sonication were correlated with the transformation of nanostructural morphologies, with fibrillar structures observed in gel and spherical aggregates in sol, respectively. The enzymatic breakdown of the hydrogels was also investigated. This allyl-functionalized hydrogelator can serve as a platform for the design of smart hydrogels, appropriate for expansion into biological systems as bio-functional and bio-responsive materials.

Multi-responsive polypeptide hydrogels derived from N-carboxyanhydride terpolymerizations for delivery of nonsteroidal anti-inflammatory drugs

“…As shown in the quantitative ATR-FTIR analyses, the content of β-sheet secondary structure in the hydrogels was calculated to be 63%, thus a mechano-triggered gel-to-sol transition was expected, based on previous studies. 43, 56 The mechano–responsiveness of the hydrogels was tested by applying sonication to the hydrogel for 30 s and the gel–to-sol transition was observed by the test tube inversion experiment. This transition was reversible, with the hydrogel reforming after maintaining the sol at T gel ( ca.…”

“…Therefore, in vitro gel weight loss profiles were obtained by measuring the weight loss of hydrogels formed from polymer 1 (4 wt%) at 37 °C. 22, 24, 56 The enzymatic degradation medium was prepared by dissolving MMP-2, proteinase K or trypsin in Tris-HCl buffer (0.05 M, pH = 8.0, 0.2 wt% NaN 3 ). The enzyme solution or Tris-HCl buffer without enzymes (0.5 mL) was added gently into each vial and removed along with accumulated gel debris at the selected time points.…”

Responsive hybrid (poly)peptide–polymer conjugates

“…In another example, Wooley and co-workers have also used NCA ROPs to develop di- and triblock conjugates consisting of oligopeptides whose secondary structure can drive the formation of gels. 82,83 …”

Reversible photo-patterning of soft conductive materials via spatially-defined supramolecular assembly

“…The heat-induced sol-to-gel transitions were attributed to the constrution of β sheets and dehydration of PEG, resulting in the formation of β-sheet-rich peptide nanofibrils (Scheme 1a); while the sonication-triggered gel-to-sol transitions were assigned to the disruption of long range interactions between these nanofibrils. 12, 13 In this way, the sol-gel transitions were correlated with reversible noncovalent transformation of supramolecularly-assembled nanostructures instead of chemical bond conversion, thus, no additional chemicals, such as a photoacid generator or exchange reagent, were needed.…”