Synthetic tripeptide based noncytotoxic hydrogelators have been discovered for releasing an anticancer drug at physiological pH and temparature. Interestingly, gel stiffness, drug release capacity and proteolytic stability of these hydrogels have been successfully modulated by incorporating d-amino acid residues, indicating their potential use for drug delivery in the future.

A dipeptide with a long fatty acid chain at its N-terminus gives hydrogels in phosphate buffer in the pH range 7.0-8.5. The hydrogel with a gelator concentration of 0.45% (w/v) at pH 7.46 (physiological pH) provides a very good platform to study dynamic changes within a supramolecular framework as it exhibits remarkable change in its appearance with time. Interestingly, the first formed transparent hydrogel gradually transforms into a turbid gel within 2 days. These two forms of the hydrogel have been thoroughly investigated by using small angle X-ray scattering (SAXS), powder X-ray diffraction (PXRD), field emission scanning electron microscopic (FE-SEM) and high-resolution transmission electron microscopic (HR-TEM) imaging, FT-IR and rheometric analyses. The SAXS and low angle PXRD studies substantiate different packing arrangements for the gelator molecules for these two different gel states (the freshly prepared and the aged hydrogel). Moreover, rheological studies of these two gels reveal that the aged gel is stiffer than the freshly prepared gel.

A histidine based amphiphile containing a C14 fatty acyl chain, N-histidyl N-myristry ethyl amine (AM1, 14.7mM) forms hydrogels in the presence of Fe 3+ (within the range 1.47 to 4.41mM) and Hg 2+ (within the range 3.67 to 11.02 mM) ions in aqueous dispersions at pH 6.6 (27C). The imidazole ring of the histidine residue plays a vital role to interact with these metalions. The thermal and mechanical stability of these metallo-hydrogels can be tuned by changing the proportion of amphiphile to metal ion ratio (1:0.1 to 1:0.3 for Fe 3+ containing gel and 1:0.25 to 1:0.75 for Hg 2+ containing gel). The metallo-hydrogels were characterized by different spectroscopic and microscopic techniques, low-and wide-angle powder X-ray diffraction and small-angle X-ray scattering studies. FT-IR and NMR spectroscopic studies indicate the participation of the imidazole ring in metal-ion binding. Low-and wide-angle powder X-ray diffraction and small-angle X-ray scattering data are in favour of a layered structure of the supramolecular assembly of the AM1 in presence of metal-ions. Both, the amphiphiles and the metal ion induced hydrogels reveal catalytic activity of p-nitrophenyl esters hydrolysis for the acetyl, n-butyl and n-octyl esters. Ferric ion containing metallo-hydrogel exhibits higher catalytic activity than the corresponding AM1 aggregate in the absence of metal-ions.

A. (2019) Selfassembling peptide-based hydrogel: regulation of mechanical stiffness and thermal stability and 3D cell culture of fibroblasts. ACS Applied Bio Materials, 2 (12). pp. 5235-5244.

A large-scale, easy synthesis of red fluorescent copper nanoclusters (CuNCs) from a cheap source copper acetate, monohydrate has been reported. A proteinaceous amino acid cysteine has been used to stabilize these clusters at room temperature. These nanoclusters have been thoroughly characterized by UV–vis absorption, fluorescence spectroscopy, matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) spectrometry, transmission electron microscopy (TEM), X-ray powder diffraction analysis, cyclic voltametry (CV), and X-ray photoelectron spectroscopy. MALDI-TOF analysis indicates that the nanocluster is a Cu5(Cys)3 species. Computational studies revealed the energy optimized structure of Cu5(Cys)3 with most possible arrangements of Cu atoms and their interactions with stabilizing ligands. It is evident from the structure that vacant Cu sites are available; hence, these sites can be used for binding with substrate molecules for catalytic reactions. Interestingly, these as-synthesized red-emitting nanocluster catalyze the degradation of 4-nitrophenol (toxic chemical used in industries) to almost nontoxic 4-aminophenol at room temperature. These nanoclusters (powdered) can also be recycled as catalyst for another time. This type of new nanocatalyst for the organic transformation of a toxic to nontoxic material holds future promise for the development of novel large-scale nanocatalytic materials.