Rati Ranjan Nayak

Ring-opening metathesis polymerization-based synthesis of polymeric nanoparticles for enhanced tumor imaging in vivo: Synergistic effect of folate-receptor targeting and PEGylation.

We have synthesized amphiphilic copolymers using ring-opening metathesis polymerization (ROMP), a copper-catalyzed dipolar click reaction, and osmium-catalyzed dihydroxylation. The resulting copolymers were easily conjugated with folate and dye (indocyanine green) moieties, using a transamidation method. The copolymers exhibited high water solubility and formed nanometer-sized self-assemblies in aqueous medium. The amphiphilic copolymers modified by dihydroxylation of the polymer backbone exhibited much lower cmc values than the non dihydroxylated copolymer. Copolymers conjugated with folate moieties reduced the fluorescence intensity of aqueous polymer solutions both in vitro and in vivo, but their self-assemblies efficiently accumulated at tumor sites because of folate-receptor recognition at tumor tissue. The PEGylation of copolymers improved the stability of the self-assemblies in aqueous medium as well as the tumor site selectivity in vivo. Furthermore, the fluorescent nanoparticles consisting of PEG- and folate-conjugated ROMP-based copolymers accumulated in tumor tissue selectively and efficiently, whereas accumulation in all other normal organs was reduced. The PEGylation and folate conjugation can synergistically improve the in vivo tumor site selectivity of ROMP-based copolymers.

Effect of amide hydrogen bonding on spontaneously formed gel-emulsions by two pyridyl carboxylic acid based amphiphiles, sodium salt of 2-dodecylpyridine-5-carboxylic acid and sodium salt of [2-dodecylpyridine-5-carboxylic]glycine: entrapment and release of vitamin B12

The present study offers the demonstration and rational design of two synthesized single chain pyridyl carboxylic acid (nicotinic acid) based amphiphilic gelators named the sodium salt of 2-dodecylpyridine-5-carboxylic acid (SDDPC) and the sodium salt of [2-dodecylpyridine-5-carboxylic]glycine (SDDPCG). The gelation abilities were tested in a series of organic solvents, by a number of physical methods including X-ray diffraction, FTIR spectroscopy, rheology, DSC, optical and electron microscopy. The minimum gelation concentration and gelation number of the gelators in different solvents were determined. No gelation was observed when pure solvents were employed. The gelation properties of these two compounds found that the gelation depends on H-bonding of the amide linkage. X-ray diffraction study indicates the presence of two recognizable morphologies for SDDPC in a gel-emulsion, whereas for SDDPCG a single type of aggregate is predominant. FTIR spectra suggest that the presence of intermolecular hydrogen bonding facilitates the gelation process. Rheological measurements demonstrated that the gel-emulsions are mechanically stable and exhibit typical viscoelastic properties. Optical microscopy images show a network structure in the gel phase and a fibril structure in the xerogel. SEM images confirmed the presence of network as well as a flex-like thick fibrous network for both the amphiphiles, forming three dimensional (3-D) networks. Both the gelators showed a remarkable response toward external pH. The gel-emulsions were used in the controlled and/or pH triggered release of entrapped (within the gel-emulsions) vitamin B12 at different pHs.

Non-Surface Activity of Cationic Amphiphilic Diblock Copolymers

Cationic amphiphilic diblock copolymers containing quaternized poly (2-vinylpyridine) chain as a hydrophilic segment (PIp-b-PNMe2VP) were synthesized by living anionic polymerization. By IR measurement, we confirmed the quaternization of the polymer (PIp-b-PNMe2VP), and determined the degree of quaternization by conductometric titration. The surface tension experiment showed that the polymers are non-surface active in nature. The foam formation of the polymer solutions was also investigated with or without added salt. Almost no foam formation behavior was observed without added salt, while a little foam was observed in the presence of 1M NaCl. The critical micelle concentration (cmc) of the diblock copolymers with 3 different chain lengths was measured by the static light scattering method. The cmc values obtained in this study were much lower than the values obtained for anionic non-surface active diblock polymers studied previously. The hydrodynamic radii of the polymer micelle increased slightly in the presence of 1 M NaCl. The transmission electron microscopic images revealed spherical micelles in pure water. In the presence of salt, the cmc values increased as was the case for anionic polymers, which is unlike conventional surfactant systems but consistent with non-surface active anionic block copolymers. The microviscosity of the micelle core was evaluated using Coumarin-153 as a fluorescent anisotropy probe using steady-sate fluorescence depolarization. Non-surface activity has been proved to be universal for ionic amphiphilic block copolymers both for anionic and cationic. Hence, the origin of non-surface activity is not the charged state of water surface itself, but should be an image charge repulsion at the air/water interface.

Surface and Antimicrobial Properties of N-Palmitoyl Amino Acid–Based Surfactants

Synthesized sodium N-pamitoyl amino acids were evaluated for surface and antimicrobial properties and compared with sodium lauryl sulfate (SLS). Emulsion stability of the amino acid surfactants and calcium tolerance of the sodium N-palmitoyl isoleucine were better as compared to SLS. Wetting ability and foaming properties of the palmitic acid-based surfactants were inferior to SLS. N-Acyl amino acids exhibited better antibacterial activity compared to sodium salts of N-acyl amino acids and standard compounds against Staphylococcus aureus MLS-16 and Bacillus subtilis. These studies revealed that the palmitoyl amino acid surfactants can be exploited in household, skin care formulations, and industrial applications. GRAPHICAL ABSTRACT

Low temperature oxygen plasma assisted surface modification of raw silk fibre and their characterizations

Raw silk fibre was treated with low temperature oxygen plasma with an aim to improve its dyeability. The XRD study reveals that a fraction of the macromolecules on the surface and in the inner part of silk fibres are oxidized during plasma treatment. The overall crystallinity of the fibre surface is reduced and the short range order is increased. Plasma treated fibre showed gradual increase of peak intensity in the Raman spectrum, and the peak shifts to lower wave numbers. Change in the micro-structural properties was observed in the scanning electron microscope images but the mechanical property of silk fibre was found to be insignificant. Smooth and homogeneous coating of a natural dye extracted from the Indian mulberry (Morinda citrifolia) was observed in the case of plasma-etched silk fibre.

Studies on hydroquinone based maleate bolaamphiphile organogels and their drug formulations

ABSTRACT Now a day’s there is an upsurge in topical gel formulations, they can be prepared by varying physico-chemical methods and provide better localized action. A maleate based symmetric bolaamphiphile was synthesized by using cost-effective starting materials under mild reaction condition. The gelation ability of bolaamphiphile in aqueous medium was examined for a series of organic solvents. In hexane, the gelator showed better gelation ability with relatively higher critical strain (54 Pa) values. Further, the microscopic images of the gel revealed flakes like morphology, both the XRD and DFT studies revealed the presence of non covalent interactions. These gels showed a high internal-phase mole ratio of the topical drugs in the order of curcumin < salicylic acid < Ibuprofen. Formation of aqueous and organic gel-phase formulation may facilitate the topical medications for various applications related to ophthalmic and skin infections.

Impact of Glycolipid Hydrophobic Chain Length and Headgroup Size on Self-Assembly and Hydrophobic Guest Release

Encapsulation of a hydrophobic guest molecule inside a micelle and its stimuli-sensitive release is a useful strategy for target-specific drug delivery. Herein, nine biobased glycolipids were derived from plant sources. The influence of headgroup on the stability and aggregation pattern in water with different alkyl chain lengths was investigated to deduce the structure-property relationship. External factors, such as temperature, pH, and NaCl and urea concentrations, were employed to explore stimuli response of glycolipid nanoassemblies. Furthermore, solvatochromic dyes, such as pyrene, N-phenyl-1-naphthylamine, and curcumin, were utilized to examine hydrophobe loading capacities of these glycolipid assemblies. A fluorescence study was performed to investigate the enzyme-sensitive hydrophobe release. Interestingly, the pH-sensitive hydrophobic guests showed pH-responsive release from dynamic micelles. Finally, the synthesized glycolipids revealed their nanoassemblies as smart carriers for hydrophobic cargo.

Synthesis and Surface Properties of Anionic Vinylguaiacol Based Surfactants

Abstract By changing amino acid head group four biobased anionic surfactants were synthesized using 4-vinylguaiacol and methylbromo undecanoate. The synthesized surfactants were characterized by NMR and mass spectrometry analysis. The surface active properties such as surface tension, wetting power, foaming characteristic, emulsion stability, calcium tolerance were studied and compared with those of sodium lauryl sulfate (SLS). Excellent emulsion stabilities and calcium tolerances were observed for the synthesized surfactants. These surfactants show a lower critical micelle concentration as compared to the conventional surfactants. The bulk micellization properties were studied using dynamic light scattering and fluorescence anisotropy technique. The antimicrobial and cytotoxicity studies were also carried out.