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Cerebrospinal fluid nitric oxide metabolite levels as a biomarker in severe traumatic brain injury

Kandasamy R, Kanti Pal H, Swamy M, Abdullah J

Int J Neurosci, 2013 Jun;123(6):385-91.
PMID: 23270401 DOI: 10.3109/00207454.2012.761983

Nitric oxide has a definitive role in the complex pathophysiology of traumatc brain injury (TBI). This prospective cohort study investigated the changes in nitric oxide metabolite (NOx) levels in cerebrospinal fluid (CSF) and their correlation with factors associated with severity and prognosis after severe TBI. NOx levels were measured in CSF obtained via ventriculostomy in 44 adult patients admitted after severe TBI (Glasgow Coma Scale ≤ 8/15). The overall mean level of CSF NOx in the study population was 7.40 ± 1.59 μmol/L. Levels of CSF NOx were found to be significantly higher in subgroups of patients with poorer outcome measured by Glasgow Outcome Scale score (p < 0.042), in patients with high intracranial pressure (ICP) readings (p < 0.027) and in those with higher Marshall computed tomography (CT) grading scores (p < 0.026). Simple logistic regression demonstrated that CSF NOx levels were a significant predictor of ICP (b = 0.493, 95%CI: 1.03, 2.58, p = 0.033). A patient with 1 μmol/L increase in NOx level had 1.6 times the odds to have an ICP ≥ 20 mmHg when other confounders were not adjusted. NOx level is also a significant predictor of Marshall CT grading (b = 0.473, 95%CI: 1.02, 2.50, p = 0.037). A patient with 1 μmol/L increase in NOx level had 1.6 times the odds to have a high Marshall grade when other confounders were not adjusted. It can be concluded that CSF NOx levels may serve as a potentially useful biomarker in severe TBI given its significant association with ICP readings as well as Marshall CT grading.
Which mild head injured patients should have follow-up after discharge from an accident and emergency ward? A study in a university hospital setting in Kelantan, Malaysia

Chan HC, Adnan WA, Jaalam K, Abdullah MR, Abdullah J

Southeast Asian J. Trop. Med. Public Health, 2005 Jul;36(4):982-93.
PMID: 16295557

Mild head injury (MHI) is a common presentation to many hospitals in both rural and urban settings in Southeast Asia, but it is not well studied. We studied 330 patients that presented to Hospital Universiti Sains Malaysia Emergency Department with possible MHI, with the intentions to identify prognostic factors that may improve the diagnosis of MHI in the emergency setting as well as to determine which patients would need follow-up. Patients' one-year outcomes were classified as discharged well (DW) for patients without post-traumatic signs and symptoms and discharged with long term follow-up (DFU) for patients with such signs and symptoms. Four patients died and 82 were DFU. An abnormal skull X ray was associated with mode of accident and type of transportation, older age, presence of vomiting, confusion, bleeding from ear, nose or throat, abnormal pupil size on the right side associated with orbital trauma, unequal pupillary reflexes, absence of loss of consciousness (LOC), a lower Glasgow Coma Scale (GCS) score, multiple clinical presentations, and DFU. An abnormal CT scan was associated with older age, multiple clinical presentation, skull X-ray findings, and DFU. A similar analysis on outcomes revealed that mode of accident, older age, vomiting, confusion, headache, bleeding from ear, nose and throat, neurological deficits, absence of LOC, pupil size, multiple presentation, abnormal skull X ray, CT scan of the brain, and a GCS of 13 was associated with DFU. In conclusion, all patients involved in motor vehicle accidents (MVAs), especially motorcycles, aged over 30 years of age, with multiple clinical presentations, including a lower GCS, and with abnormal radiological findings should have a longer follow-up due to persistent post-traumatic symptomatology.
Combination of vascularized outer-table calvarial bone graft based on the superficial temporal vessels and allomatrix for the repair of an orbito-frontal blow-out fracture in a child

Ali F, Halim AS, Najihah SZ, Ibrahim M, Abdullah J

J Craniomaxillofac Surg, 2005 Oct;33(5):326-30.
PMID: 16125400

A vascularized outer-table calvarial bone graft was used for repairing a Posnick type 2 traumatic orbito-frontal bone defect supported by the use of a calcium-based putty (Allomatrix) in a 7-year-old girl. Gaps between the donor and recipient sites were filled with Allomatrix containing demineralized bone matrix particles. Four years later there was a good cosmetic result using an artificial left eye.
Bovine pericardium for dural graft: clinical results in 22 patients

Baharuddin A, Go BT, Firdaus MN, Abdullah J

Clin Neurol Neurosurg, 2002 Sep;104(4):342-4.
PMID: 12140102

Bovine pericardium has widely been used for grafts in cardiac surgery and seems to have suitable properties for use as a dural graft. We report our experience of using locally processed bovine pericardium for dural grafts in 22 patients undergoing cranial operations.
Malignant paraganglioma of frontoethmoidal region

Sharma HS, Madhavan M, Othman NH, Muhamad M, Abdullah JM

Auris Nasus Larynx, 1999 Oct;26(4):487-93.
PMID: 10530746

Nonchromaffin paragangliomas are unusual tumours arising from widely distributed paraganglionic tissues probably of neural crest origin. In the head and neck region they are usually seen as carotid body or jugulotympanic tumours. Other rarely reported sites in the head and neck region are the orbit, nose and larynx. This report deals with a case of sinonasal paraganglioma which was initially treated with surgery and radiotherapy. Twenty two years later the tumour recurred and showed a rapid growth due to malignant transformation which we believe is late effect of radiotherapy. The clinical features, histopathology and role of radiotherapy in sinonasal paragangliomas together with a review of the medical literature have been discussed.
Spontaneous intracerebral hemorrhage in northeast Malaysian patients: a four-year study

Muiz AJ, Abdullah J, Naing NN, Ghazaime G, Ariff AR

Neuroepidemiology, 2003 May-Jun;22(3):184-95.
PMID: 12711851

The aim of this study was to compare nonsurgical versus stereotactic aspiration of intracerebral hematomas in relation to clinical aspects, computed tomographic imaging features of the brain, laboratory parameters and specific risk factors that may influence the outcome in southeast Asian Malay patients. Fifty-five of the patients with intracerebral hemorrhage (ICH) underwent stereotactic aspiration and 57 did not. Analysis was done on risk factors, locations and treatments of ICH, and the final outcomes measured by the Glasgow Outcome Scale. A total of 112 patients were evaluated. Mean age was 52 years with ages ranging from 12 to 80 years. Hypertension was seen in 60.7% of patients with ICH. The mortality rate was 25% by 3 months. 58.9% had a poor final outcome, while 41.1% had a good outcome. The selected variables were incorporated into models generated by multiple logistic regression method analysis to define the significant predictors of outcome. Significant predictors of outcome were the Glasgow Coma Scale score on admission, the duration of surgery and the total volume of the hematoma. Significant predictors of mortality were high total white blood cell differential count, low plasma protein, and high plasma lactate dehydrogenase and brain edema. The study suggests that stereotactic aspiration of patients with ICH does not offer any definite advantage over conservative treatment.
Fulltext Two-stage management of mega occipito-encephalocele

Mardzuki AI, Abdullah J, Ghazaime G, Ariff AR, Ghazali M

Med J Malaysia, 2003 Mar;58(1):115-9.
PMID: 14556336 MyJurnal

We report three cases of large occipito-encephaloceles that were managed in the Neurosciences Unit, Hospital Universiti Sains Malaysia over the last 5 years. All patients had pre-operative MRI (magnetic resonance imaging) evolution and mapping of the sagittal sinus tract. The cerebrospinal fluid (CSF) of all three patients were initially diverted by means of ventricular shunt two weeks prior to shunt removal. The slow drainage of CSF prevented electrolyte and volume disturbances due to sudden decompression during their definitive occipital encephalocele operations. After 3 years follow-up, all these patients are progressing well.
Outcome of children with traumatic brain injury in rural Malaysia

Kumaraswamy N, Naziah A, Abdullah J, Ariff MMed AR, Abdullah MR, Ghazaime G

J Clin Neurosci, 2002 May;9(3):251-5.
PMID: 12093129

Malaysia had the second highest crude accident rate in the world until 1998. Most children who were involved in these road traffic accidents required intensive neurosurgical care management. We report a prospective study on 36 paediatric neurotrauma patients in rural North East West Malaysia who underwent uniform intensive therapy and were subsequently followed up over a period of 2 years. The modified paediatric Glasgow Coma Scale with support of the revised Wechlser Intelligence Scale for children was used to test the outcome of these children over a period of two years. All patients were managed aggressively in our intensive care as well as our high dependency units. Our results indicate that improvement in outcome is seen after a six month period. Midline shift, duration of coma and duration of transport were found to be significant variables associated with bad outcome. Other variables i.e. age, sex, Glasgow Coma Scale on admission and on site, and lesions of the dominant lobe were not found to be associated with good outcome in these patients.
Teratocarcinosarcoma of the nasal cavity and ethmoid

Sharma HS, Abdullah JM, Othman NH, Muhamad M

J Laryngol Otol, 1998 Jul;112(7):682-6.
PMID: 9775307

Sinonasal teratocarcinosarcoma is very unusual malignant neoplasm histologically consisting of an epithelial element and one or more mesenchymal components. This is a report of teratocarcinosarcoma, in a 74-year-old male, involving the right nasal cavity and ethmoids with intracranial extension. The tumour was totally resected via the craniofacial approach and the patient was given post-operative chemotherapy. Extensive tumour necrosis, rapid growth and local destruction are the prominent features of this tumour. The clinical presentation, pathological features and clinical course of this rare malignancy are discussed with a review of the literature.
Intracranial Volume Post Cranial Expansion Surgery Using Three-Dimensional Computed Tomography Scan Imaging in Children With Craniosynostosis

Sulong S, Alias A, Johanabas F, Yap Abdullah J, Idris B

J Craniofac Surg, 2019 8 14;31(1):46-50.
PMID: 31403510 DOI: 10.1097/SCS.0000000000005810

BACKGROUND: Craniosynostosis is a congenital defect that causes ≥1 suture to fuse prematurely. Cranial expansion surgery which consists of cranial vault reshaping with or without fronto-orbital advancement (FOA) is done to correct the skull to a more normal shape of the head as well as to increase the intracranial volume (ICV). Therefore, it is important to evaluate the changes of ICV after the surgery and the effect of surgery both clinically and radiologically.
OBJECTIVE: The aim of this study is to evaluate the ICV in primary craniosynostosis patients after the cranial vault reshaping with or without FOA and to compare between syndromic and nonsyndromic synostosis group, to determine factors that associated with significant changes in the ICV postoperative, and to evaluate the resolution of copper beaten sign and improvement in neurodevelopmental delay after the surgery.
METHODS: This is a prospective observational study of all primary craniosynostosis patients who underwent operation cranial vault reshaping with or without FOA in Hospital Kuala Lumpur from January 2017 until Jun 2018. The ICV preoperative and postoperative was measured using the 3D computed tomography (CT) imaging and analyzed. The demographic data, clinical and radiological findings were identified and analyzed.
RESULTS: A total of 14 cases (6 males and 8 females) with 28 3D CT scans were identified. The mean age of patients was 23 months. Seven patients were having syndromic synostosis (4 Crouzon syndromes and 3 Apert syndromes) and 7 nonsyndromic synostosis. The mean preoperative ICV was 880 mL (range, 641-1234 mL), whereas the mean postoperative ICV was 1081 mL (range, 811-1385 mL). The difference was 201 mL which was statistically significant (P 1.0). However, there was 100% (n = 13) improvement of this copper beaten sign. However, the neurodevelopmental delay showed no improvement which was statistically not significant (P > 1.0).
CONCLUSION: Surgery in craniosynostosis patient increases the ICV besides it improves the shape of the head. From this study, the syndromic synostosis had better increment of ICV compared to nonsyndromic synostosis.
Voltammetric determination of iodide in iodized table salt using cetyltrimethylammonium bromide as ion-pairing

Jamilan MA, Abdullah J, Alang Ahmad SA, Md Noh MF

J Food Sci Technol, 2019 Aug;56(8):3846-3853.
PMID: 31413410 DOI: 10.1007/s13197-019-03855-x

In this work, voltammetric study based on cetyltrimethylammonium bromide (CTAB) as an ion-pairing agent for the determination of iodine level in iodized table salt has been explored. CTAB was used as an intermediate compound between iodide (I-) and the electrode due to its ability to dissociate to produce cetyltrimethylammonium ions ([CTA]+). The [CTA]+ with a long hydrophobic alkyl chain can be directly adsorbed onto the surface of the working electrode, and this in turns coated the electrode with cationic charge and enhance the electrode ability to bind to iodide (I-) and other molecular iodine ions. A mixture of iodide and CTAB ([CTA]+I-) was prepared and potential of 1.0 V for 60.0 s was applied to pre-concentrate the solution on the working electrode causing the [CTA]+I- to oxidize to iodine (I2). The produced I2 immediately react with chloride ion (Cl-) from the electrolyte of hydrochloric acid (HCl) to produce I2Cl- and form ion-pair with CTA+ as [CTA]+I2Cl-. The linear calibration curve of the developed method towards iodide was in the concentration range of 0.5-4.0 mg/L with sensitivity of - 1.383 µA mg/L-1 cm-2 (R2 = 0.9950), limit of detection (LOD) of 0.3 mg/L and limit of quantification (LOQ) of 1.0 mg/L, respectively. The proposed method indicates good agreement with the standard method for iodine determination with recovery range from 95.0 to 104.3%. The developed method provided potential application as a portable on-site iodine detector.
Fulltext A simple, portable, electrochemical biosensor to screen shellfish for Vibrio parahaemolyticus

Nordin N, Yusof NA, Abdullah J, Radu S, Hushiarian R

AMB Express, 2017 Dec;7(1):41.
PMID: 28205102 DOI: 10.1186/s13568-017-0339-8

An earlier electrochemical mechanism of DNA detection was adapted and specified for the detection of Vibrio parahaemolyticus in real samples. The reader, based on a screen printed carbon electrode, was modified with polylactide-stabilized gold nanoparticles and methylene blue was employed as the redox indicator. Detection was assessed using a microprocessor to measure current response under controlled potential. The fabricated sensor was able to specifically distinguish complementary, non-complementary and mismatched oligonucleotides. DNA was measured in the range of 2.0 × 10(-8)-2.0 × 10(-13) M with a detection limit of 2.16 pM. The relative standard deviation for 6 replications of differential pulse voltammetry (DPV) measurement of 0.2 µM complementary DNA was 4.33%. Additionally, cross-reactivity studies against various other food-borne pathogens showed a reliably sensitive detection of the target pathogen. Successful identification of Vibrio parahaemolyticus (spiked and unspiked) in fresh cockles, combined with its simplicity and portability demonstrate the potential of the device as a practical screening tool.
Fulltext Electrochemical Detection of Arsenite Using a Silica Nanoparticles-Modified Screen-Printed Carbon Electrode

Ismail S, Yusof NA, Abdullah J, Abd Rahman SF

Materials (Basel), 2020 Jul 16;13(14).
PMID: 32708531 DOI: 10.3390/ma13143168

Arsenic poisoning in the environment can cause severe effects on human health, hence detection is crucial. An electrochemical-based portable assessment of arsenic contamination is the ability to identify arsenite (As(III)). To achieve this, a low-cost electroanalytical assay for the detection of As(III) utilizing a silica nanoparticles (SiNPs)-modified screen-printed carbon electrode (SPCE) was developed. The morphological and elemental analysis of functionalized SiNPs and a SiNPs/SPCE-modified sensor was studied using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), and Fourier transform infrared spectroscopy (FTIR). The electrochemical responses towards arsenic detection were measured using the cyclic voltammetry (CV) and linear sweep anodic stripping voltammetry (LSASV) techniques. Under optimized conditions, the anodic peak current was proportional to the As(III) concentration over a wide linear range of 5 to 30 µg/L, with a detection limit of 6.2 µg/L. The suggested approach was effectively valid for the testing of As(III) found within the real water samples with good reproducibility and stability.
Sensitive detection of multiple pathogens using a single DNA probe

Nordin N, Yusof NA, Abdullah J, Radu S, Hushiarian R

Biosens Bioelectron, 2016 Dec 15;86:398-405.
PMID: 27414245 DOI: 10.1016/j.bios.2016.06.077

A simple but promising electrochemical DNA nanosensor was designed, constructed and applied to differentiate a few food-borne pathogens. The DNA probe was initially designed to have a complementary region in Vibrio parahaemolyticus (VP) genome and to make different hybridization patterns with other selected pathogens. The sensor was based on a screen printed carbon electrode (SPCE) modified with polylactide-stabilized gold nanoparticles (PLA-AuNPs) and methylene blue (MB) was employed as the redox indicator binding better to single-stranded DNA. The immobilization and hybridization events were assessed using differential pulse voltammetry (DPV). The fabricated biosensor was able to specifically distinguish complementary, non-complementary and mismatched oligonucleotides. DNA was measured in the range of 2.0×10(-9)-2.0×10(-13)M with a detection limit of 5.3×10(-12)M. The relative standard deviation for 6 replications of DPV measurement of 0.2µM complementary DNA was 4.88%. The fabricated DNA biosensor was considered stable and portable as indicated by a recovery of more than 80% after a storage period of 6 months at 4-45°C. Cross-reactivity studies against various food-borne pathogens showed a reliably sensitive detection of VP.
Orbital Morphometry: A Computed Tomography Analysis

Singh J, Rahman RA, Rajion ZA, Abdullah J, Mohamad I

J Craniofac Surg, 2017 Jan;28(1):e64-e70.
PMID: 27922969 DOI: 10.1097/SCS.0000000000003218

INTRODUCTION: The human orbit is a complex anatomic region, which plays predominant role in the evaluation of craniofacial complex. A thorough understanding of the relationship of the distance from orbital rim to the important vital structures of the orbital apex is required for the surgeon to perform safe and effective surgery.
OBJECTIVES: To evaluate and compare the depth and distances from various points of the orbital rim to the fissures and foramina of the orbital apex between genders in the local population.
METHODOLOGY: Linear measurements were conducted on 60 orbits from 30 patients who had undergone head computed tomography scan. These measurements were done utilizing the multiplanar reconstruction modes on computed tomography images with minimum slice thickness of 1 mm.
RESULTS: Males have statistically significant larger orbits than females with higher mean measurements in all parameters, except for the distance from posterior ethmoidal foramen to the optic canal which was the same. However, there were no significant differences in all parameters between the right and left orbits.
CONCLUSION: This study provides the absolute limit of safe internal orbital dissection in respect to the local population. Despite males having larger orbits than females, it is clinically negligible.
Fulltext Transcriptome profiling of sulfate deprivation responses in two agarophytes Gracilaria changii and Gracilaria salicornia (Rhodophyta)

Lee WK, Namasivayam P, Ong Abdullah J, Ho CL

Sci Rep, 2017 04 24;7:46563.
PMID: 28436444 DOI: 10.1038/srep46563

Seaweeds survive in marine waters with high sulfate concentration compared to those living at freshwater habitats. The cell wall polymer of Gracilaria spp. which supplies more than 50% of the world agar is heavily sulfated. Since sulfation reduces the agar quality, it is interesting to investigate the effects of sulfate deprivation on the sulfate contents of seaweed and agar, as well as the metabolic pathways of these seaweeds. In this study, two agarophytes G. changii and G. salicornia were treated under sulfate deprivation for 5 days. The sulfate contents in the seaweed/agar were generally lower in sulfate-deprivated samples compared to those in the controls, but the differences were only statistically significant for seaweed sample of G. changii and agar sample of G. salicornia. RNA sequencing (RNA-Seq) of sulfate-deprivated and untreated seaweed samples revealed 1,292 and 3,439 differentially expressed genes (DEGs; ≥1.5-fold) in sulfate-deprivated G. changii and G. salicornia, respectively, compared to their respective controls. Among the annotated DEGs were genes involved in putative agar biosynthesis, sulfur metabolism, metabolism of sulfur-containing amino acids, carbon metabolism and oxidative stress. These findings shed light on the sulfate deprivation responses in agarophytes and help to identify candidate genes involved in agar biosynthesis.
Fulltext Patterned Array of Poly(ethylene glycol) Silane Monolayer for Label-Free Detection of Dengue

Rosly NZ, Ahmad SA, Abdullah J, Yusof NA

Sensors (Basel), 2016 Aug 25;16(9).
PMID: 27571080 DOI: 10.3390/s16091365

In the present study, the construction of arrays on silicon for naked-eye detection of DNA dengue was demonstrated. The array was created by exposing a polyethylene glycol (PEG) silane monolayer to 254 nm ultraviolet (UV) light through a photomask. Formation of the PEG silane monolayer and photomodifed surface properties was thoroughly characterized by using atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and contact angle measurements. The results of XPS confirmed that irradiation of ultraviolet (UV) light generates an aldehyde functional group that offers conjugation sites of amino DNA probe for detection of a specific dengue virus target DNA. Employing a gold enhancement process after inducing the electrostatic interaction between positively charged gold nanoparticles and the negatively charged target DNA hybridized to the DNA capture probe allowed to visualize the array with naked eye. The developed arrays demonstrated excellent performance in diagnosis of dengue with a detection limit as low as 10 pM. The selectivity of DNA arrays was also examined using a single base mismatch and noncomplementary target DNA.
Fulltext Secure Trust-Based Blockchain Architecture to Prevent Attacks in VANET

Khan AS, Balan K, Javed Y, Tarmizi S, Abdullah J

Sensors (Basel), 2019 Nov 14;19(22).
PMID: 31739437 DOI: 10.3390/s19224954

Vehicular ad hoc networks (VANET) are also known as intelligent transportation systems. VANET ensures timely and accurate communications between vehicle to vehicle (V2V) and vehicle to infrastructure (V2I) to improve road safety and enhance the efficiency of traffic flow. Due to its open wireless boundary and high mobility, VANET is vulnerable to malicious nodes that could gain access into the network and carry out serious medium access control (MAC) layer threats, such as denial of service (DoS) attacks, data modification attacks, impersonation attacks, Sybil attacks, and replay attacks. This could affect the network security and privacy, causing harm to the information exchange within the network by genuine nodes and increase fatal impacts on the road. Therefore, a novel secure trust-based architecture that utilizes blockchain technology has been proposed to increase security and privacy to mitigate the aforementioned MAC layer attacks. A series of experiment has been conducted using the Veins simulation tool to assess the performance of the proposed solution in the terms of packet delivery ratio (PDR), end-to-end delay, packet loss, transmission overhead, and computational cost.
Voltammetric determination of hydroquinone, catechol, and resorcinol by using a glassy carbon electrode modified with electrochemically reduced graphene oxide-poly(Eriochrome black T) and gold nanoparticles

Mohammed Modawe Alshik Edris N, Abdullah J, Kamaruzaman S, Sulaiman Y

Mikrochim Acta, 2019 03 29;186(4):261.
PMID: 30927085 DOI: 10.1007/s00604-019-3376-y

A nanocomposite consisting of electrochemically reduced graphene oxide, poly(Eriochrome black T) and gold nanoparticles (ERGO-pEBT/AuNPs) was prepared for the simultaneous detection of resorcinol (RC), catechol (CC), and hydroquinone (HQ). The electrochemical oxidation of HQ, CC, and RC was analysed by using cyclic voltammetry and differential pulse voltammetry. Three well-separated potentials were found at 166, 277, and 660 mV (vs. Ag/AgCl) for HQ, CC, and RC, respectively The linear ranges were 0.52-31.4, 1.44-31.2, and 3.8-72.2 μM for HQ, CC, and RC, respectively. The limits of detections (LODs) for both individual and simultaneous detections are negligibly different are (15, 8, and 39 nM, respectively). Graphical abstract Voltammetric determination of hydroquinone, catechol, and resorcinol at ERGO-pEBT/AuNPs resulted in high peak currents and outstanding oxidation potential separation of the analytes.
An Optical Biosensor based on Immobilization of Laccase and MBTH in Stacked Films for the Detection of Catechol

Abdullah J, Ahmad M, Heng LY, Karuppiah N, Sidek H

Sensors (Basel), 2007 Oct 11;7(10):2238-2250.
PMID: 28903224 DOI: 10.3390/s7102238

The fabrication of an optical biosensor by using stacked films where 3-methyl-2-benzothiazolinone hydrazone (MBTH) was immobilized in a hybrid nafion/sol-gelsilicate film and laccase in a chitosan film for the detection of phenolic compounds wasdescribed. Quinone and/or phenoxy radical product from the enzymatic oxidation ofphenolic compounds was allowed to couple with MBTH to form a colored azo-dye productfor spectrophometric detection. The biosensor demonstrated a linear response to catecholconcentration range of 0.5-8.0 mM with detection limit of 0.33 mM and response time of10 min. The reproducibility of the fabricated biosensor was good with RSD value of 5.3 %(n = 8) and stable for at least 2 months. The use of the hybrid materials of nafion/sol-gelsilicate to immobilize laccase has altered the selectivity of the enzyme to various phenoliccompounds such as catechol, guaicol, o-cresol and m-cresol when compared to the non-immobilized enzyme. When immobilized in this hybrid film, the biosensor response onlyto catechol and not other phenolic compounds investigated. Immobilization in this hybridmaterial has enable the biosensor to be more selective to catechol compared with the non-immobilized enzyme. This shows that by a careful selection of different immobilizationmatrices, the selectivity of an enzyme can be modified to yield a biosensor with goodselectivity towards certain targeted analytes.

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