Noor Hasyierah Mohd Salleh

Design Development of Acoustic Waves Based Sensitive Sensors for Escherichia coli O157:H7 Detection

Food contamination has become critical issue and is being worse due to the insensitive detection devices. One of the dangerous food contaminations is by Escherichia coli (E.coli) O157:H7, one of the harmful bacterial pathogens which is distributed in soil, marine and estuarine waters, the intestinal tract of animals, or water contaminated with fecal matter. A small amount of E.coli with the dose fewer than 100 organisms in food products or water is enough to cause serious gastrointestinal illness to human. Hence, the ultra-high sensitive, label free biosensors have been designed in this research for the low concentration E.coli detection. Surface acoustic waves (SAW) devices have been initially developed and used for the high-volume low-cost TV component. Due to the ultra-sensitivity to the surface perturbation, SAW based devices have been modified to be sensors. Initially, SAW sensors were developed for gas detections and have been moving towards biological detections recently. Shear horizontal surface acoustic wave (SHSAW), one of the SAW based types is most suitable for the liquid based application as it has the advantage of acoustic energy is not being radiated into liquid. However, the main SHSAW design components are the operating frequency and wave length. These are strictly depended on the inter digital transducers (IDTs) design. Therefore, this paper is presenting the IDTs design concept and pattern development by using computer aid design (CAD) software.

Evaluation of Protease Enzyme on Pomacea canaliculata Eggs

Pomacea canaliculata (PC) is one of the most destructive pests as it causes severe damage to the paddy field. Most of the approaches are targeting its flesh rather than its egg; however in the same time, it has high fecundity and hatchability rate. Thus, effective approach is necessary to control the hatchability, which in turn affects its life cycle. Protease has been shown to have the capability to suppress the hatchability of Pomacea canaliculata eggs (PCE). The objective of this study is to further support the findings, where it discusses the chemical assessment of protease-treated PCE. The assessment focuses on the effect of protease treatment on the PCE in terms of the following factors, namely non-hatchability, cuticle protein reduction, gas exchange and water loss activity. Non-hatchability of 42 and 91% after treating with 0.75 and 5 U/ml protease, respectively, was recorded. With these findings, it is safe to consider that protease applicable to be used as biocontrol against PCE. The non-hatchability of protease-treated eggs occurred as a result of cuticle disruption as supported by the present chemical studies.

Modeling Development of a High-Sensitivity Escherichia coli O157:H7 Detection Based on SH SAW Sensor

Surface acoustic waves based devices were initially developed for the telecommunication purpose such as signal filters and resonators. The acoustic energy is strongly confined on the surface of the surface acoustic waves (SAW) based devices and consequent their ultra-sensitivity to the surface perturbation. This has made SAW permits the highly sensitive detection of utterly diminutive charges on the surface. Hence, SAW based devices have been modified to be sensors. Food contamination has become critical issue and sensitive detection devices are needed urgently as small amount of harmful bacterial pathogens such as Escherichia coli (E.coli) O157:H7with the dose fewer than 100 organisms in food products or water is enough to cause serious gastrointestinal illness to human. Therefore, ultra-high sensitive, label free biosensors have been designed in this research for the low concentration E.coli detection. After the saturated development in telecommunication filed, SAW sensors were developed for gas detections and have been moving towards biological detections recently. Shear horizontal surface acoustic wave (SHSAW), one of the SAW based types is most suitable for the liquid based application as it has the advantage of acoustic energy is not being radiated into liquid. Therefore, SHSAW device has the potential to provide high-performance sensing platform in this research. There have been a lot of complicated theoretical models for the SAW devices development since 1960 as signal filters and resonators such as from delta function model, equivalent circuit model, to the current SAW models such as coupling-of-modes (COM) model, P-matrix model and finite element analysis (FEA) model. However, SHSAW device in this research is not meant for signal filter or resonators but used for surface sensing purpose, therefore the simplicity method of the modeling is presented in the paper for the E.coli detection sensor development.

Synthesis of MCM-41 from Rice Husk Ash and its Utilization for Lipase Immobilization

Mesoporous materials are favorable for enzyme immobilization due to their unique properties of large surface area, uniform pore system and functionalizable surfaces. Immobilization on these materials enhances enzyme stability, activity and resistance towards harsh environmental conditions such as temperature and pH. The present study deals with synthesis of mesoporous materials namely MCM-41. For that purpose, the MCM-41 was synthesized using cetyltrimethylammonium bromide (CTAB) as a template and extractable silica from rice husk ash as a silica source. The synthesis was performed under alkaline conditions to produce white fine solid particles, followed by grafting with 3-aminopropyltriethoxysilane and activation with carbodiimide before it was immobilized with lipase. Characterization of those fine particles using Nitrogen physisorption gives BET surface area, as BET, and the pore diameterto be 1184 m²/g and 2.58 nm respectively. Fourier Transform Infrared spectra show peak of SiO2, NH2 and COOH functional group which confirms the existence of those compounds in covalent bonding formation between amine-grafted MCM-41 and lipase enzyme. Immobilized enzyme shows an increase in pH stability when compared to free enzyme at fixed temperature of 20°C in time range from 30 to 180 minutes.