Indrajit Maity

Sonication induced peptide-appended bolaamphiphile hydrogels for in situ generation and catalytic activity of Pt nanoparticles

The self-assembly of peptide based bolaamphiphiles is investigated upon sonication. We show the ability of peptide bolaamphiphiles 1 and 2 to form strong and rigid self-supporting hydrogels under physiological conditions upon sonication. The self-assembly of higher order supramolecular structures occurs through a synergic effect of hydrogen bonding and π-stacking interactions. Phenylalanine rich peptide bolaamphiphile 2 self-assembles into well-defined nanoribbons whereas tyrosine rich functional material 1 self-assembles into nanofibrillar structures that can be used as a template for in situ generation of platinum nanoparticles. Furthermore, hydrogenation reactions are catalyzed by in situ synthesized Pt nanoparticles such as p-phenylenediamine, which is prepared by the reaction of p-nitroaniline with Pt nanoparticles.

Lipase-catalyzed dissipative self-assembly of a thixotropic Peptide bolaamphiphile hydrogel for human umbilical cord stem-cell proliferation.

We report lipase-catalyzed inclusion of p-hydroxy benzylalcohol to peptide bolaamphiphiles. The lipase-catalyzed reactions of peptide bolaamphiphiles with p-hydroxy benzylalcohol generate dynamic combinatorial libraries (DCL) in aqueous medium that mimic the natural dissipative system. The peptide bolaamphiphile 1 (HO-WY-Suc-YW-OH) reacts with p-hydroxy benzylalcohol in the presence of lipase forming an activated diester building block. The activated diester building block self-assembles to produce nanofibrillar thixotropic hydrogel. The subsequent hydrolysis results in the dissipation of energy to form nonassembling bolaamphiphile 1 with collapsed nanofibers. The thixotropic DCL hydrogel matrix is used for 3D cell culture experiments for different periods of time, significantly supporting the cell survival and proliferation of human umbilical cord mesenchymal stem cells.

Photophysical study of a π-stacked β-sheet nanofibril forming peptide bolaamphiphile hydrogel

We describe the state of molecular self-assembly of a peptide based bolaamphiphile molecule using spectroscopic and microscopic techniques. The tryptophan and phenylalanine containing peptide bolaamphiphile forms a hydrogel upon sonication under physiological conditions. Sonication helps to reorient the peptide molecules by providing the required energy for the self-assembly process. The disassembly and self-assembly processes are influenced by various stimuli, including heating–cooling and shaking–rest methods. The extensive hydrogen bonding and π–π stacking interactions are responsible for the self-assembly process, which is confirmed by FT-IR, temperature dependent NMR and fluorescence spectroscopy studies. FT-IR and powder X-ray diffraction studies reveal that the gelator molecules self-assemble into an antiparallel β-sheet type structure. The TEM image of the hydrogel shows a well-defined amyloid-like nanofibrillar structure. The amyloid-like behaviour of the fibril forming peptide bolaamphiphile hydrogel is confirmed by ThT and Congo red binding studies. The effect of concentration, time and temperature on the self-assembly mechanism of the peptide bolaamphiphile hydrogel is investigated by time resolved fluorescence spectroscopy.

Emerging π-stacked dynamic nanostructured library

We describe a general strategy to control the state of molecular self-assembly under thermodynamic control in which gelation facilitates formation of a predominating π-stacked nanostructured product.

Peptide nanofibers decorated with Pd nanoparticles to enhance the catalytic activity for C–C coupling reactions in aerobic conditions

We report the synergistic effects of peptide nanofibers decorated with Pd nanoparticles to enhance the catalytic activity for C–C coupling reactions in mild and aerobic conditions.

Self-programmed nanovesicle to nanofiber transformation of a dipeptide appended bolaamphiphile and its dose dependent cytotoxic behaviour

Nanostructural transition of a small peptide bolaamphiphile via molecular self-assembly is a challenging task. Here, we report the self-programmed morphological transformation from nanovesicles to nanofibers of a smart peptide bolaamphiphile in its self-assembling hydrogel state. The nanostructural transition occurs based on the structural continuity of the β-sheet structures. Spectroscopic studies confirmed the different molecular arrangements of the two different nanostructures. Furthermore, the smart bolaamphiphile shows a dose-dependent cytotoxicity and cell-proliferation behaviour.

Exploiting a self-assembly driven dynamic nanostructured library

A self-assembly driven dynamic peptide based nanostructured library is made using a reversible chemical fuel-catalyzed reaction. The reaction between peptide based bolaamphiphiles and dimethyl sulphate facilitates the formation of a predominant nanostructured product in a gel phase medium. The resultant product self-assembles into well-defined β-sheets which further self-assemble into hierarchical nanofibrils.

Colorimetric Enzyme Sensing Assays via In Situ Synthesis of Gold Nanoparticles

We report a successful facile and novel approach for in situ synthesis of gold nanoparticles (AuNPs) via enzymatic dephosphorylation reaction at room temperature. Fmoc-tyrosine phosphate and cytidine-5-mono phosphate are used to sense the activities of an enzyme alkaline phosphatase. Formation of AuNps is highly selective towards biomolecules and it is readily detected colorimetrically and UV–Vis analysis. In this procedure, dephosphorylated product plays both roles as reducing and stabilizing agent to direct the formation of AuNPs in aqueous media. Transmission electron microscopic study reveales that hexagonal AuNPs were synthesized by using Fmoc-tyrosine phosphate and alkaline phosphatase. Wide angle X-ray scattering data confirms the formation of AuNPs. FT-IR studies confirm that biomolecules play crucial role to stabilize the AuNPs by molecular interactions with the surface of AuNPs. In situ synthesized AuNPs are applied for the sensing of enzyme activity.