Abhishek Baral

Assembly of an injectable noncytotoxic peptide-based hydrogelator for sustained release of drugs.

A new synthetic tripeptide-based hydrogel has been discovered at physiological pH and temperature. This hydrogel has been thoroughly characterized using different techniques including field emission scanning electron microscopic (FE-SEM) and high-resolution transmission electron microscopic (HR-TEM) imaging, small- and wide-angle X-ray diffraction analyses, FT-IR, circular dichroism, and rheometric analyses. Moreover, this gel exhibits thixotropy and injectability. This hydrogel has been used for entrapment and sustained release of an antibiotic vancomycin and vitamin B12 at physiological pH and temperature for about 2 days. Interestingly, MTT assay of these gelator molecules shows almost 100% cell viability of this peptide gelator, indicating its noncytotoxicity.

An Amino‐Acid‐Based Self‐Healing Hydrogel: Modulation of the Self‐Healing Properties by Incorporating Carbon‐Based Nanomaterials

An amino-acid-based (11-(4-(pyrene-1-yl)butanamido)undecanoic acid) self-repairing hydrogel is reported. The native hydrogel, as well as hybrid hydrogels, have been thoroughly characterized by using various microscopic techniques, including transmission electron microscopy (TEM), atomic force microscopy (AFM), Raman spectroscopy, fluorescence spectroscopy, FTIR spectroscopy, X-ray diffraction, and by using rheological experiments. The native hydrogel exhibited interesting fluorescence properties, as well as a self-healing property. Interestingly, the self-healing, thixotropy, and stiffness of the native hydrogel can be successfully modulated by incorporating carbon-based nanomaterials, including graphene, pristine single-walled carbon nanotubes (Pr-SWCNTs), and both graphene and Pr-SWCNTs, within the native gel system. The self-recovery time of the gel was shortened by the inclusion of reduced graphene oxide (RGO), Pr-SWCNTs, or both RGO and Pr-SWCNTs. Moreover, hybrid gels that contained RGO and/or Pr-SWCNTs exhibited interesting semiconducting behavior.

Tuning of Silver Cluster Emission from Blue to Red Using a Bio-Active Peptide in Water

Blue, green, and red emitting silver quantum clusters have been prepared through green chemical approach by using a bio-active peptide glutathione (reduced) in a 50 mM phosphate buffer at pH 7.46. This study describes fluorescence emission tuning of the silver clusters by making different sized Ag clusters using slightly different reaction conditions keeping the same stabilizing ligand, reducing agent, solvent system, and silver salt precursor. The preparation procedure of these silver quantum clusters is new and highly reproducible. Each of these clusters shows very interesting fluorescence properties with large stokes shifts, and the quantum yields of blue, green, and red clusters are 2.08%, 0.125%, and 1.39%, respectively. These silver quantum clusters have been characterized by using different techniques including fluorescence spectroscopy, UV-vis spectroscopy, field-emission gun transmission electron microscopic (FEG-TEM) imaging and MALDI-TOF MS analyses. MALDI-TOF MS analyses show that the size of these blue, green and red emitting silver clusters are Ag5 (NC1, nanoclusters 1), Ag8 (NC2, nanoclusters 2) and Ag13 (NC3, nanoclusters 3), respectively, by using 2,5-dihydroxybenzoic acid as a matrix. These clusters are stable in broad ranges of pH. The NC3 (red emitting) has been successfully utilized for selective and sensitive detection of toxic Hg(II) ions in water by using even naked eyes, fluorometric, and calorimetric studies. The lower limit of detection of Hg(II) ions in water has been estimated to be 126 and 245 nM from fluorometric and UV-vis analyses, respectively. Enthalpy change (ΔH) during this Hg(II) sensing process is 2508 KJ mol(-1).

A Peptide-Based Mechano-sensitive, Proteolytically Stable Hydrogel with Remarkable Antibacterial Properties

A long-chain amino acid containing dipeptide has been found to form a hydrogel in phosphate buffer whose pH ranges from 6.0 to 8.8. The hydrogel formed at pH 7.46 has been characterized by small-angle X-ray scattering (SAXS), wide-angle powder X-ray diffraction (PXRD), Fourier transform infrared (FT-IR) spectroscopy, field-emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HR-TEM) imaging and rheological analyses. The microscopic imaging studies suggest the formation of a nanofibrillar three-dimensional (3D) network for the hydrogel. As observed visually and confirmed rheologically, the hydrogel at pH 7.46 exhibits thixotropy. This thixotropic property can be exploited to inject the peptide. Furthermore, the hydrogel exhibits remarkable antibacterial activity against Gram-negative bacteria Escherichia coli and Pseudomonas aeruginosa, which are responsible for many common diseases. The hydrogel has practical applicability due to its biocompatibility with human red blood cells and human fibroblast cells. Interestingly, this hydrogel shows high resistance toward proteolytic enzymes, making it a new potential antimicrobial agent for future applications. It has also been observed that a small change in molecular structure of the gelator peptide not only turns the gelator into a nongelator molecule under similar conditions, but it also has a significant negative impact on its bactericidal character.

Peptide based hydrogels for cancer drug release: modulation of stiffness, drug release and proteolytic stability of hydrogels by incorporating D-amino acid residue(s)

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 fluorescent gold-cluster containing a new three-component system for white light emission through a cascade of energy transfer

Fluorescent gold clusters (blue emitter) have been judiciously utilized to initiate an energy transfer process as a donor to the green emitting riboflavin (acceptor) and then riboflavin relays the energy transfer to the red emitting dye Rhodamine B in a controlled fashion to generate white light emission in a novel three component system (gold cluster, riboflavin and Rhodamine B). The CIE coordinate of (0.32, 0.35) has been achieved for the white light emitting solution. The solution processable white light emitting material has been prepared using a non-toxic, eco-friendly solvent, in the aqueous medium. It can be soaked or coated over a solid surface to generate white light emission. Writing can also be achieved on the silica surface by using this new white light emitting eco-friendly solution.

A Dipeptide-based Superhydrogel: Removal of Toxic Dyes and Heavy Metal Ions from Waste-water.

A short peptide‐based molecule has been found to form a strong hydrogel at phosphate buffer solution of pH 7.46. The hydrogel has been characterized thoroughly using various techniques including field emission scanning electron microscopy (FE‐SEM), wide angle powder X‐ray diffraction (PXRD), and rheological analysis. It has been observed from FE‐SEM images that entangled nanofiber network is responsible for gelation. Rheological investigation demonstrates that the self‐assembly of this synthetic dipeptide results in the formation of mechanically strong hydrogel with storage modulus (G′) around 104 Pa. This gel has been used for removing both cationic and anionic toxic organic dyes (Brilliant Blue, Congo red, Malachite Green, Rhodamine B) and metal ions (Co2+ and Ni2+) from waste water. Moreover, only a small amount of the gelator is required (less than 1 mg/mL) for preparation of this superhydrogel and even this hydrogel can be reused three times for dye/metal ion absorption. This signifies the importance of the hydrogel towards waste water management.