Molecular Engineering Approaches to Highly Structured Materials

Design and synthesis of novel supramolecular architectures is an interesting area of research in the last two decades. Intermolecular interactions assisted self-assembly of molecular and macromolecular building blocks play an important role in obtaining the desired shape and function of the supramolecular architectures. A combination of the classical covalent synthesis with the self-assembly assisted formation of well-defined architectures (noncovalent synthesis) allows us to develop novel multifunctional materials. Our approach in this area is focused on the design of novel molecular and biomolecular building blocks and the optimization of structure-property relationship of the materials using self-assembly approach. This presentation will focus on our recent efforts on the design and synthesis of polymers and oligopeptides for investigation of the self-assembly and fine-tuning the structure-property relationship. Also, some highlights will be given on our initial investigation on how hard minerals are synthesized by natural molecules through the self-assembly processes.Singapore-MIT Alliance (SMA

Molecular Engineering of Conjugated Polymers for Sensor Applications

In recent years, the application of fluorescent conjugated polymers for sensing chemical and biological analytes has received much attention from many researchers. A promising development in this direction was the fabrication of conducting polymer-based sensors for the detection of metal ions, small organic molecules and biomolecules. Herein, we have designed, synthesized and studied a series of copolymers containing alternate phenylene and 2,5- or 2,6-substituted pyridine rings. The basic N-atom of the pyridine ring and the adjacent –OH group from the phenyl ring provide binding sites for metal ions. Another series of water-soluble conjugated polymers with propoxy sulfonate side chains are investigated for biosensor applications. Significant quenching of the polymer fluorescence upon addition of viologen derivatives was also observed. The quenching effect on the polymer fluorescence confirmed that the newly synthesized polymers can be useful in the application of metal and biological sensors.Singapore-MIT Alliance (SMA

Molecular Engineering of Amphiphilic Pyridine Incorporated Conjugated Polymers for Metal Ion Sensors

Recent developments in the synthesis and structure-property investigation studies of conjugated polymers have led to the design of novel polymeric materials with tailored properties for advanced technological applications. A promising development in this direction involves the fabrication of conducting polymer based sensors for the detection of metal ions and small organic molecules. Herein, we designed, synthesized and studied a series of amphiphilic copolymers containing alternate phenylene and 2,5- or 2,6- or 3,5-substituted pyridine rings. The basic N-atom of the pyridine ring and the adjacent –OH group from the phenyl ring provide binding sites for metal ions. Thermal properties, and optical properties of polymers in presence of acid, base and metal ions are investigated. A few target polymers showed high sensitivities for metal ions in solution.Singapore-MIT Alliance (SMA

Synthesis, Optical properties and Applications of Water Soluble Conjugated PPPs for Biosensors

In recent years, application of fluorescent conjugated polymers to sense chemical and biological analytes has received much attention owing to its technological significance. Water soluble conjugated polymers are interesting towards the developing sensors for biomolecules. In this present contribution, we describe the syntheses and characterization of a series of water soluble conjugated polymers with sulfonic acid groups in the side chain. Such anionic conjugated polymers are designed to interact with biomolecules such as cytochrome-C. All polymers are water soluble and showed strong blue emission. Significant quenching of the fluorescence from our functionalized PPP was observed upon addition of viologen derivatives or cytochrome -C.Singapore-MIT Alliance (SMA

Anti-proliferative activity of silver nanoparticles

This is an Open Access article distributed under the terms of the Creative Commons Attribution Licens

Eggshell Matrix Protein Mimetics: Elucidation of Molecular Mechanism of Goose Eggshell Calcification using Designed Peptides

Model peptides were designed, synthesized and conducted a detailed structure-property study to unravel the molecular mechanism of goose eggshell calcification. The peptides were designed based on the primary structural features of the eggshell matrix proteins ansocalcin and OC-17. In vitro CaCO₃ crystal growth experiments in presence of these peptides showed calcite crystal aggregation as observed in the case of the parent protein ansocalcin. The structure of these peptides in solution was established using intrinsic tryptophan fluorescence studies and quasi-elastic light scattering experiments. The structural features are correlated with observed results of the in vitro crystallization studies.Singapore-MIT Alliance (SMA

Designer peptides to understand the mineralization of calcium salts

Recently, we reported the extraction, purification and amino acid sequence of ansocalcin, the major goose eggshell matrix protein. In vitro studies showed that ansocalcin induces spherical calcite crystal aggregates. We designed two peptides using the unique features of the sequence of ansocalcin and the role of these peptides in CaCO₃ crystallization was investigated. The peptides showed similar activities as compared to ansocalcin, but at a higher concentration. The full characterization of the peptides and a rational for the observed morphology for the calcite crystals are discussed in detail.Singapore-MIT Alliance (SMA

Deposition of Thin Films of Biocompatible Calcium Carbonate via Template-Driven Mineralization

Natural bone is a composite of collagen based hydrogel and inorganic dahilite crystals. The unusual combination of a hard inorganic material and an underlying elastic hydrogel network endows native bone with unique mechanical properties, such as low stiffness, resistance to tensile and compressive forces and high fracture toughness. Throughout the cavities of the bone, there are bone cells and myriads of soluble and extracellular matrix components that are constantly involved in the bone formation and remodeling process. Among the extra cellular component the acidic matrix proteins that are attached to the collagen scaffold play important templating and inhibitory roles during the mineralization process. It would be interesting to generate such functional scaffolds that mimic a template driven mineralization and which can assist cell adhesion, proliferation, migration and differentiation. Towards this direction, we have chosen one synthetic (Nylon 66 membrane) and one natural (eggshell membrane) scaffold and carried out a template driven mineralization of CaCO₃ as model systems. The surface modifications were carried out by the pre-adsorption of acidic polymers before the deposition of the CaCO₃. The deposition of the crystalline calcium carbonate on these modified templates were archived from a supersaturated solution of Ca(HCO₃)₂.Singapore-MIT Alliance (SMA

Differential regulation of intracellular factors mediating cell cycle, DNA repair and inflammation following exposure to silver nanoparticles in human cells

10.1186/2041-9414-3-2Genome Integrity3

Atomic Force Microscopy and Optical Studies of Organic Thin Films with Hydrogen-Bonded Networks

Brewster angle microscopy and atomic force microscopy were used to characterize the surface morphology of thin films in situ or after transfer onto solid supports. Two acids were studied, differing in carboxylic acid head groups, resulting in significantly different morphological features for thin films formed from these two amphiphiles on a Langmuir trough. Differences in self-assembly and domain sizes were correlated with the formation of hydrogen-bonded networks. The influence of surface hydrophobicity or hydrophilicity during deposition on morphology was also characterized, with spherulitic features appearing in some samples