We are working in the interdisciplinary area of research involving polymer chemistry, supramolecular chemistry and biomedical science. Primarily we engineer molecules or macromolecules by specific functionality to realize precision assembly over different length scales and explore them for functions in biomedical and material science. Recent research activity of our group may be classified under the following three broad areas:
We work on exploring structurally new amphiphilic polymers and study their stimuli responsive aggregation properties. We have established generally applicable step-growth polymerization methodology for functional polymers having pH-responsive β-thiopropionate ester or glutathione responsive disulfide group in the backbone and functional chain-ends. We conduct in-depth physical studies on the influence of structural parameters on the nature of the self-assembled structure (micelle, polymersome etc), exchange dynamics in these aggregates using FRET, drug encapsulation efficacy and pH/ redox-responsive drug release in vitro to cancer cells. We also work on covalent bioconjugation to such stimuli-responsive macromolecular scaffolds which are encoded with information for triggered cascade degradation for targeted drug delivery application. Our newly developed methodology for poly(disulfides) offer enormous opportunity for accessing new and tunable redox-responsive biomaterials with great potential in biomedical application.
Molecular Assembly of Engineered Amphiphiles:
We have developed supramolecularly engineered amphiphilic macromolecules (SEAM) which consist of a supramolecular structure directing unit (SSDU) in the terminal of a hydrophilic polymer/ protein. Specific supramolecular assembly motif of the SSDU (consisting of a H-bonding group and a naphthalene-diimide (NDI) chromophore) regulates the entropy-driven remarkably stable aqueous self-assembly of polymers and/ or proteins by superseding the packing parameters. In this way, we have pinned down the resolution of structure controlling parameters to molecular level which opens up new opportunities for controllable mesoscopic structure formation of synthetic polymers with molecular scale precision. Such SSDU appended small molecule amphiphiles exhibit highly stable self-assembled nanostructures, controls the surface functional group display and thus enables promising biological applications, including multivalent binding with protein, enzyme inhibition, and antimicrobial activity.
Pathway Diversity and Controlled Supramolecular Polymerization of π-Systems:
We have explored H-bonding driven controlled supramolecular polymerization (CSP) of D+A, D-π-A and D-σ-A type systems and developed thorough understanding of the various structural nuances and chirality on the internal order, mode of stacking (alternating/ segregated) and the thermodynamics and mechanistic aspects (cooperative/ isodesmic) of supramolecular polymerization. We have explored the pathway diversity in such complex molecular assemblies and established new methodologies for controlled supramolecular polymerization by chain growth mechanism using external trigger (light) or seed or other molecular entities as the initiating species to synthesize supramolecular polymers and copolymers of multiple building blocks. We have realized structural precision of such supramolecular polymers and copolymers over different length scales that are ubiquitous in biological systems. In an effort to combine the advantages of supramolecular (precise internal order) and covalent polymers (stability), we have explored intra-chain H-bonding driven folding followed by macroscopic assembly of chromophore-appended polyurethane as a versatile scaffold for constructing semiconducting organic nanotubes with percolated pathway for highly efficient charge-transport.