Hairul Anuar Tajuddin

Influence of nonionic branched-chain alkyl glycosides on a model nano-emulsion for drug delivery systems

The effect of incorporating new nonionic glycolipid surfactants on the properties of a model water/nonionic surfactant/oil nano-emulsion system was investigated using branched-chain alkyl glycosides: 2-hexyldecyl-β(/α)-D-glucoside (2-HDG) and 2-hexyldecyl-β(/α)-D-maltoside (2-HDM), whose structures are closely related to glycero-glycolipids. Both 2-HDG and 2-HDM have an identical hydrophobic chain (C16), but the former consists a monosaccharide glucose head group, in contrast to the latter which has a disaccharide maltose unit. Consequently, their hydrophilic-lipophilic balance (HLB) is different. The results obtained have shown that these branched-chain alkyl glycosides affect differently the stability of the nano-emulsions. Compared to the model nano-emulsion, the presence of 2-HDG reduces the oil droplet size, whereas 2-HDM modify the properties of the model nano-emulsion system in terms of its droplet size and storage time stability at high temperature. These nano-emulsions have been proven capable of encapsulating ketoprofen, showing a fast release of almost 100% in 24h. Thus, both synthetically prepared branched-chain alkyl glycosides with mono- and disaccharide sugar head groups are suitable as nano-emulsion stabilizing agents and as drug delivery systems in the future.

Physicochemical Characterization of Natural-like Branched-Chain Glycosides toward Formation of Hexosomes and Vesicles

Synthetic branched-chain glycolipids have become of great interest in biomimicking research, since they provide a suitable alternative for natural glycolipids, which are difficult to extract from natural resources. Therefore, branched-chain glycolipids obtained by direct syntheses are of utmost interest. In this work, two new branched-chain glycolipids are presented, namely, 2-hexyldecyl β(α)-D-glucoside (2-HDG) and 2-hexyldecyl β(α)-D-maltoside (2-HDM) based on glucose and maltose, respectively. The self-assembly properties of these glycolipids have been studied, observing the phase behavior under thermotropic and lyotropic conditions. Due to their amphiphilic characteristics, 2-HDG and 2-HDM possess rich phase behavior in dry form and in aqueous dispersions. In the thermotropic study, 2-HDG formed a columnar hexagonal liquid crystalline phase, whereas in a binary aqueous system, 2-HDG formed an inverted hexagonal liquid crystalline phase in equilibrium with excess aqueous solution. Furthermore, aqueous dispersions of the hexagonal liquid crystal could be obtained, dispersions known as hexosomes. On the other hand, 2-HDM formed a lamellar liquid crystalline phase (smectic A) in thermotropic conditions, whereas multilamellar vesicles have been observed in equilibrium with aqueous media. Surprisingly, 2-HDM mixed with sodium dodecyl sulfate or aerosol OT induced the formation of more stable unilamellar vesicles. Thus, the branched-chain glycolipids 2-HDG and 2-HDM not only provided alternative nonionic surfactants with rich phase behavior and versatile nanostructures, but also could be used as new drug carrier systems in the future.

Generic Methods for Micrometer- And Nanometer-Scale Surface Derivatization Based on Photochemical Coupling of Primary Amines to Monolayers of Aryl Azides on Gold and Aluminum Oxide Surfaces

A series of aryl azide terminated thiols and phosphonic acids has been synthesized, and used to prepare self-assembled monolayers on (respectively) gold and aluminum oxide surfaces. The rates of photoactivation were determined using contact angle measurement and X-ray photoelectron spectroscopy (XPS). The behavior of a diazirine functionalized aryl thiol was also studied. The rates of activation were found to be similar for all five adsorbates. However, the extent of photochemical coupling of a primary amine was significantly greater for the aryl azides than for the diazirine. A range of primary amines was successfully coupled to all of the azides with high yield. Little difference in reactivity was observed following perfluorination of the aromatic ring. Micrometer-scale patterns were fabricated by carrying out exposures of the aryl azide terminated SAMs through a mask submerged under a film of primary amine. Contrasting amines could be introduced to unreacted regions in a subsequent maskless step. A scanning near-field optical microscope was used to fabricate nanopatterns. Exposure of the azides to irradiation at 325 nm in air enabled selective deactivation of azides. The surrounding surface was functionalized with a primary amine in a maskless process; when a protein-resistant oligo(ethylene glycol) functionalized amine was used it was possible to produce protein nanopatterns, by adsorbing protein to features defined using near-field exposure.

Feasibility study on the use of the seeding growth technique in producing a highly stable gold nanoparticle colloidal system

Stable colloidal gold nanoparticles (Au NPs) are synthesized successfully using a seeding growth technique. The size of the nanoparticles is determined using transmission electron microscopy (TEM), and it is observed that the size of the nanoparticles ranges from 7 to 30 nm. The TEM images and optical absorption spectra of the Au NPs reveal that the suspension is well dispersed and consistent with the particle size. The feasibility of the seeding growth technique is investigated using Turbiscan Classic MA 2000 screening stability tester. Based on the peak thickness kinetics and mean value kinetics, the backscattered light profiles indicate that the suspension is highly stable without particle sedimentation as well as negligible agglomeration. In addition, the Au NPs are proven to remain stable over a period of 2 months. Particle sedimentation eventually occurs due to the weight of nanoparticles. It is concluded that the seeding growth technique is feasible in synthesizing stable Au NPs. Controlling the stability, size and shape of Au NPs are technologically important because of the strong correlation between these parameters and the optical, electrical, and catalytic properties of the nanoparticles.

N-linked glycolipids by Staudinger coupling of glycosylated alkyl diazides with fatty acids

Aiming for new glycolipids with enhanced chemical stability and close structural similarity to natural cell membrane lipids for the development of a drug delivery system, we have synthesized double amide analogs of glyco-glycerolipids. The synthesis applied a Staudinger reaction based coupling of a 1,3-diazide with fatty acid chlorides. While the concept furnished the desired glucosides in reasonable yields, the corresponding lactosides formed a tetrahydropyrimidine based 1:1 coupling product instead. This unexpected coupling result likely originates from steric hindrance at the iminophosphorane intermediate and provides an interesting core structure for potentially bioactive surfactants. The assembly behavior of both glycolipid types was investigated by optical polarizing microscopy, DSC and surface tension studies.

Phenyl quinoxalin-2-yl ether.

The aromatic ring systems in the title compound, C14H10N2O, form a dihedral angle of 63.8 (1)°, resulting in an opening up of the ether-O atom angle to 118.2 (1)°.

2-Naphthyl quinoxalin-2-yl ether

In the crystal structure of the title compound, C18H12N2O, the two fused rings are aligned at 64.2 (1)°; the C—O—C angle is 118.73 (12)°.

4-(4-Hydroxymethyl-1H-1,2,3-triazol-1-yl)benzoic acid.

In the title compound, C10H9N3O3, there is a small twist between the benzene and triazole rings [dihedral angle = 6.32 (7)°]; the carboxylic acid residue is almost coplanar with the benzene ring to which it is attached [O—C—C—C torsion angle = 1.49 (19)°]. The main deviation from coplanarity of the non-H atoms is found for the hydroxy group which is almost perpendicular to the remaining atoms [N—C—C—O torsion angle = −75.46 (16)°]. In the crystal, the presence of O—H⋯O (between carboxyl groups) and O—H⋯N (between the hydroxy group and the triazole ring) hydrogen bonds leads to supramolecular chains along [03]. The chains are connected into sheets via C—H⋯O(hydroxy) interactions.

2,2 '- Nonane-1,9-diylbis(nitrilomethylidyne) Diphenol

In the title Schiff base compound, C23H30N2O2, the complete molecule is generated by crystallographic twofold symmetry, with one C atom lying on the rotation axis. The nonane chain adopts a linear conformation and the hydroxy group forms an intramolecular O—H⋯N hydrogen bond to the imine group.

Electronic Properties of Synthetic Shrimp Pathogens-derived DNA Schottky Diodes

The exciting discovery of the semiconducting-like properties of deoxyribonucleic acid (DNA) and its potential applications in molecular genetics and diagnostics in recent times has resulted in a paradigm shift in biophysics research. Recent studies in our laboratory provide a platform towards detecting charge transfer mechanism and understanding the electronic properties of DNA based on the sequence-specific electronic response, which can be applied as an alternative to identify or detect DNA. In this study, we demonstrate a novel method for identification of DNA from different shrimp viruses and bacteria using electronic properties of DNA obtained from both negative and positive bias regions in current-voltage (I–V) profiles. Characteristic electronic properties were calculated and used for quantification and further understanding in the identification process. Aquaculture in shrimp industry is a fast-growing food sector throughout the world. However, shrimp culture in many Asian countries faced a huge economic loss due to disease outbreaks. Scientists have been using specific established methods for detecting shrimp infection, but those methods do have their significant drawbacks due to many inherent factors. As such, we believe that this simple, rapid, sensitive and cost-effective tool can be used for detection and identification of DNA from different shrimp viruses and bacteria.