Abdul Razak Khairunisak

Formation of ZnO Nanorods via Seeded Growth Hydrothermal Reaction

In this study, ZnO nanorods was formed on a seeded substrates prepared by thermal oxidation of Zn foil followed by hydrothermal reaction. ZnO seed was prepared via thermal oxidation process at 300°C for 10 minutes to form uniform circular nanosize grains that were suitable as a seeded template for the growth of ZnO nanorods via hydrothermal reaction. Several hydrothermal reaction parameters were studied; hydrothermal reaction temperature, ratio of zinc nitrate to hexamethylamine and pH. In hydrothermal reaction, the formation of ZnO nanorods occurs due to thermal degradation of hexamethylamine (HMT) which released hydroxyl ions that react with Zn ions in the precursor solution. Well aligned, ZnO nanorods with length of ~700 nm, base diameter of ~200 nm and top diameter of less than 30 nm needle-like structure were formed on seeded Zn substrate with concentration ratio of zinc nitrate to hexamethylamine 0.1M:0.1M, pH 6-7 at hydrothermal reaction temperature of 80°C

Properties of Amorphous Silica Entrapped Isoniazid Drug Delivery System

This work describes the properties of silica drug delivery system (DDS) produced using micelles entrapment approach. Isoniazid, which is a water soluble drug for tuberculosis was used in the system. The effects of synthesis parameters were systematically studied such as synthesis temperature (38-70°C), amount of butanol co-solvent (6-18 ml), and amount of Si organic precursor (2-8 ml). From transmission electron microscope (TEM) images, the size of DDS could be tuned from 21-104 nm by changing the reaction temperature. The increase of butanol co-solvent enlarged the size of DDS in the range of 40-94 nm. A similar trend was observed for DDS with increasing organic Si precursor whereby the particle size could be tuned from 40-132 nm. However, at high organic Si precursor of > 2 ml, a bimodal structure of DDS was observed. Stability study in biological media at 37°C of selected sample showed that the produced DDS had acceptable degree of agglomeration.

Properties of ZnO Nanorods Arrays Growth via Low Temperature Hydrothermal Reaction

This work describes properties of 1-D ZnO nanorods arrays growth using low temperature hydrothermal method on a seeded substrate. The properties of ZnO seed were studied by varying thermal oxidation temperature from 250-450°C. The formation of ZnO nanorods was studied by varying the growth time during hydrothermal process. The optimum oxidation temperature to produce seeded ZnO template was 400°C. The formation of ZnO nanorods was further studied by varying hydrothermal reaction growth time from 1 to 24 hours. The optimum hydrothermal growth time of 4 hours produced blunt tip-like nanorods with length of ~735 nm and top diameter of ~66 nm. I-V characteristics of ZnO nanorods photodetector in dark, ambient light and UV light were also studied. The change in the photoconductivity under UV illumination was found to be 1 order of magnitude higher compared to dark and ambient light. With an incident wavelength of 370 nm and applied bias of 3V, the responsivity of photodetector was 5.0 mA/W, which was higher compared to other reported works. The increase of photosensitivity indicated that the produced ZnO nanorods were suitable for UV photodetector applications.

Green Synthesis of 10 nm Gold Nanoparticles via Seeded-Growth Method and its Conjugation Properties on Lateral Flow Immunoassay

In this work, 10 nm gold nanoparticles (AuNPs) was successfully synthesized via seeded-growth method. The green chemically synthesis of this AuNPs becomes attractive because the growth process does not involve heat. Moreover, this technique has advantages of quick, simple, and low cost process. Sodium borohydrate (NaBH4) was used as a reducing agent while trisodium citrate was used as a source of OH- ions in the seed stage. Hydroxylamine hydrochloride (NH4.3H2O) was used as a slow reducing agent to enlarge 4 nm seeds to 10 nm AuNPs. A 4 ml AuNPs seed was the optimized volume to produce 10 nm AuNPs with great homogeneity and dispersity. A sharp peak of surface plasmon resonance (SPR) measurement at 517 nm proved that 10 nm AuNPs was successfully synthesized via this method. Optical properties of the seeds and grown AuNPs were analyzed using UV-Vis spectroscopy while size and surface morphology were observed using a transmission electron microscopy (TEM). Particle size distribution was measured using Zetasizer. 10 nm AuNPs was then conjugated with streptavidin and goat anti-human IgA. Depending on type of protein, 10 µg/ml of streptavidin and 11.2 µg/ml of goat anti-human IgA were required to conjugate with 10 nm AuNPs. The produced products had binding capability on lateral flow immunoassay (LFI). A few nanometer red-shifted absorption spectrum of 10 nm AuNPs conjugated protein revealed successful conjugation instead of agglomeration. 1% BSA was determined as the optimum concentration to stabilize 10 nm AuNPs conjugated biomolecules.

Formation of Anodic Oxide Nanotubes in H2O2 - Fluoride Ethylene Glycol Electrolyte as Template for Electrodeposition of α-Fe2O3

Anodic oxidation of titanium (Ti), zirconium (Zr) and niobium (Nb) foils in fluoride ethylene glycol (EG) added to it 1 H2O2 as oxidant was done to produce oxide film with nanostructures at 40 V. Whilst arrays of aligned nanotubes were successfully formed on the surface of Ti and Zr respectively, anodic Nb2O5 was found to consist of nanoporous structure with pore size of ~ 20 nm. Despite long nanotubes were formed on both Ti (2 μm) and Zr (3 μm), the surface of the nanotubes suffered from severe dissolution, thinning the wall and collapsing them. Well defined, ordered surface structure of the nanotubes is required as they will be used as template for subsequent deposition of nanoparticles. This was achieved when Ti anodised in 5 ml H2O2 fluoride EG. With excess H2O2 etching at the surface occur more uniformly forming homogenous surface structure. α-Fe2O3 were then electrodeposited on this surface at-3 V from chloride solution and the mode of formation is believed to be due to electrogeneration of base at the surface of the TiO2.

The Effect of Amount of Surfactant and Types of Drug on Amorphous Silica Drug Delivery System (DDS)

This study describes the formation of silica nanocolloids for drug delivery system (DDS) via micelles formation approach. Micelles formed above critical micelle concentration (CMC) of the surfactant in aqueous solution. In this study, non-ionic Tween 80 was used as a surfactant and its effect on size and distribution of silica nanocolloids DDS was systematically studied. From transmission electron microscope (TEM) images, the size of silica increased from 30 nm to 50 nm with increasing amount of Tween 80 from 0.02 wt%, 0.0275wt%, 0.035wt% and 0.045 wt% respectively. Silica DDS with 0.0275wt% as optimum amount of Tween 80 encapsulated poor water soluble drug, Rifampicin has larger size (~53.8 nm) with better encapsulation efficiency compared to silica DDS encapsulated water soluble drug, Isoniazid (~39.9 nm). X-ray diffraction spectrum shows that silica DDS produced is in amorphous structure. Stability test of silica DDS encapsulated Rifampicin in 1M Sodium Chloride (NaCl) and 1% mouse serum are 42.78 % and 64.91%, respectively, which is inacceptable range for drug delivery application.

Study on Controlled Size, Shape and Dispersity of Gold Nanoparticles (AuNPs) Synthesized via Seeded-Growth Technique for Immunoassay Labeling

This study describes the formation of spherical gold nanoparticles (AuNPs) using a simple seeded-growth technique. The size and surface morphology of AuNPs were investigated using transmission electron microscopy (TEM) and UV-Vis spectrophotometer was used to determine the wavelength and absorption of AuNPs. In the seed stage, the effect of trisodium citrate volume was studied. The size of AuNPs at seed stage was varied from 15 to 40 nm with decreasing volume of trisodium citrate. In the growth stage, the effects of seed solution volume and concentration of hydroxylamine were studied. The size of AuNPs produced became larger when the amount of seed solution was reduced. This approach was beneficial to produce AuNPs with the size range from 15 to 150 nm. The increase of hydroxylamine concentration increased the size of AuNPs. However, after the concentration of hydroxylamine reached supersaturation condition (3 M NH2OH.HCl), the AuNPs formed in a bulk and clusters. Selected sizes of AuNPs were then conjugated to antibody and proved by testing on the immunoassay test strip. The observation using naked eyes for the appearance of red lines on the immunoassay test strip showed that AuNPs were successfully conjugated to antibody and specifically bound to the antigen drawn on the strip assay by tested with positive and negative serum of the disease.

Rapid diagnosis of amoebic liver abscess using recombinant Entamoeba histolytica pyruvate phosphate dikinase

Abstract Introduction Amoebiasis, caused by the protozoan parasite Entamoeba histolytica, is an important parasitic cause of death in humans; and mortality is mainly due to amoebic liver abscess (ALA). Accurate and early diagnosis is thus important; however its diagnosis still poses many challenges due to the limitations of the available detection tools. Previously, we have reported that an excretory-secretory protein of E. histolytica, pyruvate phosphate dikinase (PPDK), is a potential diagnostic marker for ALA, hence it may be exploited in the development of a new test for ALA. Objective To develop lateral flow dipstick (LFD) test using recombinant PPDK (rPPDK) and evaluate its potential for diagnosis of ALA. Methods rPPDK was expressed, purified and evaluated by Western blot. In parallel recombinant Gal/GaNAc lectin (rGal/GalNAc), as control antigen, was produced and tested similarly. The LFD test using rPPDK was subsequently developed (rPPDK-LFD) and evaluated for serodiagnosis of ALA. Results & Discussion The rPPDK protein expressed had an estimated molecular mass of 98 kDa as determined by SDS-PAGE, and purification using Ni-NTA resin yielded 1.5 mg of rPPDK from 1 L of culture. The protein identity was confirmed by MALDI-TOF/TOF. Western blots using sera from patients with ALA, healthy individuals and other diseases probed with antihuman IgG4-HRP showed the highest sensitivity (93.3%) and specificity (100%); as compared to blots using IgG and IgG1 as secondary antibodies. Additionally, rPPDK showed better specificity when compared to rGal/GalNAc. In the development of the LFD test, the optimum concentration of rPPDK and optical density of colloidal gold conjugated anti-human IgG4 were 1.25 mg/ml and 5, respectively. Evaluation of rPPDK-LFD using ALA patients and control serum samples showed 87% diagnostic sensitivity and 100% specificity. Conclusion The laboratory prototype rPPDK-LFD showed good potential for rapid diagnosis of ALA, and merit further multicentre validation using larger number of serum samples.

Physical Properties of the Amorphous Silica Encapsulated Fluorescence Dye

Amorphous nanosilica entrapped fluorescence dye intended to be used as tracing agent for imaging of cell or tissue in human cell was prepared using micelle entrapment approach. Micelles were produced by mixing a surfactant in water with additives such as butanol and ammonia in a preheated bioreactor. Then, 1,1%-dioctadecyl-3,3,3%,3% tetramethylindocarbocyanine perchlorate (DiI) dye tracing agent was added into the mixture followed by the addition of silica precursor. The parameters studied including effect of surfactant amount, effect of temperature and amount of Si precursor. Silica encapsulated DiI produced were then characterized using Transmission Electron Microscope (TEM), X-ray diffraction (XRD) and UV-Vis NIR spectrophotometer. Dynamic light scattering (DLS) showed that tunable size of nanoparticles in the range of 30-150 nm can be produced by varying synthesis parameters. The results showed that the silica encapsulated DiI became bigger and uniform in size with the increase of temperature and amount of surfactant. The silica encapsulated with DiI is photostable which the intensity of fluorescence value is 279.12 after 90 minutes exposure to halogen lamp (200W) compared to bare DiI that degraded to 100.61.

Iron Salt Concentration Effect to the Precipitation of Iron Oxide Nanoparticles Conjugated Antibody

This study covers the effect of ferrous chloride (FeCl2) concentration on the formation of iron oxide nanoparticles (IONPs) via the precipitation method. IONPs with appropriate surface functionalization were synthesized in order to obtain a stable colloidal IONPs (ferrofluid) for the conjugation process. The electrostatic repulsion using percloric acid (HClO4) and steric stabilization using silane polyethelene glycol (SiPEG) were generated. The optimum concentration of FeCl2 was at 0.3 M. From the transmission electron microscopy (TEM) image, the size of IONPs obtained was ~13 nm. The stable IONPs were then conjugated to the antibody and tested in the lateral flow immunoassay as the labelling agent. The conjugated IONPS with the antibody was proven sensitive to the Brugian Filiarisis disease.