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Dr. Rajdip Roy

PhD Chemistry

Postdoctoral Research Fellow

Department of Chemical and Biomolecular Engineering

234 McCourtney Hall

University of Notre Dame

Notre Dame, IN 46556

United States of America

The main objectives of our current research goal at The University of Notre Dame are to develop peptide based supramolecular biomaterials for glucose recovery in biological systems. In a diabetic patient, when the glucose level in blood goes down to normal threshold margin (normoglycemia) upon treatment of insulin, the situation is called hypoglycemia that can be fatal. To rescue glucose, we deliver glucagon (a glucose inducing peptide hormone) via covalent or non-covalent pathway using peptide based soft biomaterials. Peptides were synthesized in a such a sequential way so that the positive charge of Arginine’s guanidium group and the negative charge of tetrahedral boronate ester (Coupling of 4-carboxy-3-fluorophenylboronic acid pinacol ester with the free N-terminus of the peptide [glucose sensing pendent]) are in a close proximity (Non-covalent interactions like electrostatic interactions along with peptide H-bonding for self-assembly). Thus, glucose sensing soft biomaterials were synthesized using Dissipative Non-equilibrium Self-assembly (DNESA) process. The glucagon loading and releasing are also studied using these peptide soft self-assembled materials which will be useful in various biomedical areas.

I was a postdoctoral research fellow working in the field of biomedical polymers at the Casali Center of Applied Chemistry in the Institute of Chemistry, The Hebrew University of Jerusalem, Israel. The main objectives of our research goal are to develop polymeric materials for 3D printing, injectable soft materials, nanocarriers for drug delivery, degradable reverse thermo-responsive multiblock copolymers, biodegradable tissue adhesives etc. My present research is focused on the study of a series of hollow nanoscale constructions which can display a large and reversible change in their dimensional size within a very short range of temperature interval and as well as change of pH. These thermoresponsive nanostructures are synthesized by crosslinking functionalized amphiphilic molecules, such as poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) (PEO–PPO–PEO) triblocks. These supramolecular architectures are generated by intra-micellarly crosslinking PEO–PPO–PEO dimethacrylate amphiphiles. The drug loading and releasing are also studied using these hollow nanocarriers which will be useful in various biomedical areas.

I was a Ph. D student in the Department of Organic Chemistry, Indian Association for the Cultivation of Science, Kolkata. For last 5 years I was working in the field of crystal engineering, supramolecular chemistry and self-assembly. Supramolecular chemistry is chemistry beyond the molecule. Conventional chemistry deals with covalent bonds while supramolecular chemistry examines the weaker and reversible non-covalent interactions like hydrogen bonding, hydrophobic forces, π-π interactions, electrostatic effects etc. between the molecules. The main objective of our research work was to develop various drugs based supramolecular gels (driven by self-assembly) for plausible biomedical applications.

Supramolecular gels obtained from low molecular weight gelators (LMWGs) have gained significant attention over the past few decades because of their wide range of applications including gels as cosmetics, sensors, biomineralization, liquid crystalline materials, drug delivery system etc. The main objective of my research work was to develop various drugs and/or bioactive agent based supramolecular gels for their plausible biomedical applications such as wound healing, drug delivery etc. The present work reports the rational design, syntheses and characterization of various new supramolecular gelators (organogelators and hydrogelators) resulting from different drug and/or bioactive molecules.

In one of our early works, supramolecular gelators were designed following molecular engineering approach – wherein well-known gelling scaffolds such as acid, amide, peptide etc. were covalently conjugated with various bioactive drug molecules [Chem. Asian J. 2014, 9, 3196–3206].

In another work, the gelators were developed following supramolecular synthon approach in the context of crystal engineering. Nonsteroidal anti-inflammatory drugs (NSAIDs) were reacted with a primary amine based antiviral and an antiparkinsonian drug amantadine to obtain 1D hydrogen bonded network (HBN) containing primary ammonium monocarboxylate (PAM) synthon. The fact that most of the salts were turned out to be gelator in methyl salicylate increased the scope of self-delivery in multi-drug-delivery fashion [Chem. Eur. J. 2014, 20, 15320–15324].

Most interestingly, in a recent work, a judicious combination of molecular and crystal engineering approaches were implemented as a new strategy for designing a series of simple organic salt based hydrogelators as a drug delivery vehicle in self-delivery fashion [Chem. Eur. J. 2016, 22, 14929–14939].

Another recent work has provided the development of salt metathesis technique to synthesize Zn(II)-NSAID (nonsteroidal anti-inflammatory drug) metallohydrogels that showed both anti-inflammatory and anti-bacterial properties making it appropriate for multi-drug-self-delivery application [Chem. Commun. 2016, 52, 13811-13814].

Lastly, we have described the importance of supramolecular synthon in gelation and application of in vivo supramolecular gel in mice model for treating skin inflammation in mice. Thus, different approaches were instigated in designing different drug and/or bioactive molecule based supramolecular gelators for their various applications [Chem. Eur. J. 2017, 23, 15623–15627].

Furthermore, the nonsteroidal anti-inflammatory drugs (NSAIDs) based supramolecular gel systems were developed for treating skin inflammation in mice by topical self-delivery fashion which did not require any additional polymeric gel matrix (such as carbomer, polysorbate, hydroxypropylcellulose, propylene glycol, glycerides, etc. commonly used in commercial topical gel formulation) thereby making this approach a step forward in developing supramolecular gel for various biomedical applications.