Potensi larutan reagen fenilfluoron untuk digunakan sebagai bahan reagen bagi pembangunan sensor optik pH dibincangkan dalam kajian ini. Reagen ini dipilih kerana ia belum pernah dilaporkan sebelum ini untuk digunakan sebagai bahan reagen bagi pembangunan sensor optik pH. Berdasarkan kajian larutan yang telah dijalankan, julat rangsangan linear pH bagi reagen fenilfluoron ialah antara pH 4–11. Perubahan warna dapat diperhatikan, iaitu warna kuning dalam asid kuat, warna oren dalam asid lemah serta bes lemah dan warna ungu dalam bes kuat. Perubahan warna yang berlaku adalah lebih kurang 5 saat. Reagen fenilfluoron mempunyai kestabilan foto yang baik dengan nilai RSD 0.33% untuk tempoh kajian selama 95 hari. Nilai RSD bagi kebolehulangan pada pH 2, pH 7 dan pH 12 adalah masing-masingnya sebanyak 2.6%, 0.9% dan 1.4%. Pemerhatian ini menunjukkan fenilfluoron mempunyai potensi yang baik untuk digunakan sebagai bahan reagen bagi pembangunan sensor optik pH.
The adsorption of CO at polycrystalline copper surface was investigated spectroscopically. It was found that CO adsorbed as a linear adsorbed CO, Cu-COL and was a dominant species on copper surface at low CO concentration. A Cu-COL was electrochemically converted to a bridge bonded CO, Cu-COB at a high CO concentration condition. Increasing the CO surface coverage, qCO will increase the formation of adsorbed bridge bonded CO. A nitrogen gas purging treatment was used to examine the stability of an adsorbed CO through the evacuation process. The result showed that Cu-COB remained intact while Cu-COL was completely removed from the copper surface. It suggests that Cu-COL may involve in a weak bonding to a copper surface such as in a physisorbed interaction, while Cu-COB consists much stronger bonding such as a chemisorbed interaction. The N2 purging treatment also gave an additional prove that Cu-COB was partly converted to Cu(I)-CO at anodic potential regions.
Empat puluh sampel batuan granit berbutir kasar daripada Kuala Kubu Bharu telah dikumpulkan daripada 14 lokaliti di sepanjang singkapan jalan daripada Taman Bukit Bunga hingga ke kampung Pertak. Sampel-sampel teras selinder dan blok empatsegi telah disediakan daripada sampel lapangan tersebut untuk menjalani ujian halaju sonik dan mekanik setelah pengukuran beberapa sifat fizik. Nilai purata porositi berkesan sampel-sampel tersebut ialah 1.33 % manakala purata ketumpatan kering dan tepu adalah 2542 dan 2555 kg/m3. Graviti spesifik yang dihitung berjulat 2.1-2.9. Halaju denyut ultrasonik min gelombang P dan S yang melalui bahan batuan yang diuji ialah 5359 m/s dan 2890 m/s. Ujian-ujian mampatan sepaksi menunjukkan purata kekuatan mampatan sepaksi sampel yang bernilai 138.6 MPa. Nilai purata bagi indeks kekuatan beban titik Is(50) pula ialah 5.63. Oleh itu perkaitan kekuatan mampatan sepaksi dengan kekuatan beban titik ialah dengan faktor multiplikasi 25.
Globalisasi dan dunia ICT masa kini telah meningkatkan lagi permintaan terhadap tenaga buruh yang berkualiti. Majikan pada hari ini sudah tidak lagi berpegang kepada persepsi bahawa pengetahuan akademik semata-mata adalah mencukupi malah mereka telah menyarankan agar institusi pengajian tinggi dapat melahirkan siswazah yang mempunyai kemahiran boleh-pindah yang tinggi demi meningkatkan peluang mereka untuk mendapatkan pekerjaan. Saranan sedemikian kian mendapat tempat memandangkan statistik kebelakangan ini menunjukkan pengangguran di kalangan siswazah adalah semakin meningkat di negara ini. Makalah ini membincangkan persepsi pelajar tahun akhir Universiti Kebangsaan Malaysia terhadap atribut pekerjaan dari segi kepentingannya dan tahap kemahiran atau keupayaan mereka sendiri. Kajian ini merangkumi pelajar jurusan sains dan sastera. Tahap kepuasan pelajar dari aspek program pengajian dan pengalaman di universiti secara keseluruhan turut dinilai. Seramai 200 orang pelajar pra-siswazah tahun akhir telah dipilih secara pensampelan rawak berstratum dan data yang diperoleh diproses menggunakan kaedah-kaedah analisis min, ujian-t dan analisis varians. Keputusan analisis mendapati pelajar menilai tahap kepentingan kemahiran-kemahiran itu lebih tinggi daripada tahap kemahiran mereka sendiri dan terdapat perbezaan di antara tahap kemahiran daripada aspek jurusan, jantina, PNGK dan etnik. Pada keseluruhannya, pelajar didapati berpuas hati dengan program pengajian, pengalaman di universiti dan persediaan kerjaya masing-masing. Walau bagaimanapun, daripada hasil kajian ini terdapat beberapa aspek yang perlu diberi tumpuan terutamanya aspek sokongan dan bimbingan dari staf akademik dan pihak universiti dalam perancangan kerjaya pelajar serta penambaikan kemudahan pelajar.
Sejak taburan normal ditemui dan ianya merupakan salah satu taburan yang penting dalam statistik, terdapat banyak pengujian statistik yang dibangunkan untuk menguji kenormalan data. Namun begitu masih tidak banyak kajian yang dilakukan untuk melihat kembali keupayaan pengujian statistik yang sedia ada. Sebahagian daripada pengujian statistik didapati mudah tetapi hanya sesuai untuk sesuatu keadaan. Dalam kajian ini, pengujian statistik berdasarkan statistik Cramer-von Mises cuba diperbaiki berdasarkan rumus Weibull. Kekuatan statistik yang baru ini dibandingkan kekuatan dengan statistik traditional Anderson-Darling (AD), Cramer von-Mises (CR), Kolmogorov-Smirnov (KS) dan Shapiro-Wilk (SW). Kajian simulasi berdasarkan beberapa taburan yang berbeza menunjukkan pengujian statistik yang dicadangkan paling sesuai untuk menguji kenormalan.
Perubahan beberapa nutrien dan parameter kualiti air Sungai Sarawak telah dikaji melalui pensampelan serta analisis air secara intensif, iaitu empat kali pensampelan di sebelah pagi dan empat kali pada waktu petang. Stesen pensampelan air terletak di Waterfront, bandaraya Kuching dan satu lagi stesen yang terletak di bahagian hulu iaitu Batu Kitang yang berdekatan dengan tapak pengambilan air. Stesen pensampelan Batu Kitang diadakan untuk tujuan perbandingan kualiti air. Nutrien yang telah dianalisis terdiri daripada ammonium, nitrat, fosfat terlarut, sulfat dan kation utama (K, Na, Ca, Mg). Aras ion ammonium, nitrat, fosfat terlarut dan sulfat dalam Sungai Sarawak di stesen Waterfront ialah 0.03 – 0.67, 0.03 – 0.14, 0.03 – 0.74 dan 0.02-0.38 mg/L masing-masing. Perubahan maksimum yang dicerap dalam sehari untuk ammonium ialah 25 kali ganda, untuk fosfat terlarut dan sulfat ialah hampir 11 kali ganda dan untuk nitrat dan kation utama, perubahan maksimum hanya kurang daripada dua kali ganda.
Characterisation of the leaching behaviour of coal fly ash from Tenaga Nasional Berhad (TNB) by using tank leaching test method has been reported. The leachability of the constituents such as major elements and toxic metals in the coal fly ash was studied. Eight renewed leachant solutions after 6 hours, 1, 2, 5, 8, 21, 36 and 64 days were investigated after filtration. The parameters namely pH, cumulative release regarding the major elements and toxic metals to duration were presented. The results showed that the pH solutions increased from pH 4 to neutral and remained stable during the test. It might have resulted from the large buffering capacity of the coal fly ashes. Five major elements namely Al, Ca, K, Mg and Na were detected with Ca concentration in the leachant solutions was the highest for all samples. Toxic metals such as As, Ba, Co, Cr, Mn, Ni, Pb, Se and Zn were found and the test showed consistent results on the As, Ba, Mn, Se and Zn in leachant solutions. The findings also showed that some of the toxic metal concentrations namely As, Ba, Cr, Pb and Se exceeded the maximum allowance of the guideline of drinking water quality in Malaysia and WHO. Obviously, proper waste management has to be applied in this scenario.
MeSH terms: Aluminum; Coal; Lead; Malaysia; World Health Organization; Zinc; Waste Management; Coal Ash; Water Quality; Drinking Water
Jaafar S, Suhaili MR, Mohd Noh K, Zainal Ehsan F, Lee FS
Citation: Jaafar S, Suhaili MR, Mohd Noh K, Zainal Ehsan F, Lee FS. Primary Healh Care: Key To Intersectoral Action For Health And Equity. World Health Organization; 2007
MeSH terms: Malaysia; Primary Health Care; Rural Health; Rural Health Services
Citation: Efroymson D, Velasco MG. Tobacco Use in Southeast Asia: Key Evidences for Policy Development. Bangkok, Thailand: Southeast Asia Tobacco Control Alliance; 2007
TABLE OF CONTENTS
Acknowledgement 3
Introduction to SEATCA Research on Tobacco 4
Tobacco and Poverty: Lessons from Cambodia and Vietnam 6
Demand Analysis and Tobacco Taxes in Vietnam and Malaysia 9
ASEAN Free Trade Area and Tobacco: A Regional Summary 12
Health Costs of Tobacco 14
Socio-demographic and Psychological Trends of Youth Smoking 17
Knowledge, Attitudes, and Practice: Tobacco Use among Health Professionals, Medical Students and Monks 20
Analysis of Smoking Behavior in Cambodia 23
Women and Tobacco: Smoke_]free Homes in Cambodia, Malaysia and Vietnam 26
Women and Tobacco: Reasons for Use, and Prevention Strategies in Cambodia, Malaysia and Thailand 29
Citation: Institute of Medicine (US). Committee on Cancer Control in Low- and Middle-Income Countries, Frank A. Sloan, Hellen Gelband (Eds.). Cancer Control Opportunities in Low- and Middle-Income Countries. Washington DC: Institute of Medicine, National Academies Press, 2007
Full text contains Malaysian data:
Appendix A. Cancer Control in Malaysia and Tanzania. page 305
Whitefly-transmitted, cucurbit-infecting begomoviruses (genus Begomovirus, family Geminiviridae) have been detected on cucurbit crops in Bangladesh, China, Egypt, Israel, Malaysia, Mexico, the Philippines, Thailand, United States, and Vietnam. Pumpkin plants showing leaf curling, blistering, and yellowing symptoms were observed in the AVRDC fields (Tainan, Taiwan) during 2001 and in nearby farmers' fields during 2005. Two samples from symptomatic plants were collected in 2001 and six collected in 2005. Viral DNAs were extracted (2), and the PCR, with previously described primers, was used to detect the presence of begomoviral DNA-A (4), DNA-B (3), and associated satellite DNA (1). Begomoviral DNA-A was detected in one of the 2001 samples and in all 2005 samples. The PCR-amplified 1.5 kb viral DNA-A from one positive sample each from the 2001 and 2005 collections was cloned and sequenced. On the basis of the 1.5-kb DNA-A sequences, specific primers were designed to completely sequence the DNA-A component. The overlap between fragments obtained using primer walking ranged from 43 to 119 bp with 100% nt identities. The complete DNA-A sequences were determined for the two isolates as 2,734 bp (2001) (GenBank Accession No. DQ866135) and 2,733 bp (2005) (GenBank Accession No. EF199774). Sequence comparisons and analyses were performed using the DNAMAN Sequence Analysis Software (Lynnon Corporation, Vaudreuil, Quebec, Canada). The DNA-A of the begomovirus isolates each contained the conserved nanosequence-TAATATTAC and six open reading frames, including two in the virus sense and four in the complementary sense. On the basis of a 99% shared nucleotide sequence identity, they are considered isolates of the same species. BLASTn analysis and a comparison of the sequence with others available in the GenBank database ( http://www.ncbi.nlm.nih.gov ) indicated that the Taiwan virus shared its highest nt identity (more than 95%) with the Squash leaf curl Philippines virus (GenBank Accession No. AB085793). Virus-associated satellite DNA was not found in any of the samples. DNA-B was found in both samples, providing further evidence that the virus was the same as the bipartite Squash leaf curl Philippines virus. To our knowledge, this is the first report of Squash leaf curl Philippines virus in Taiwan. References: (1) R. W. Briddon et al. Virology 312:106, 2003. (2) R. L. Gilbertson et al. J. Gen. Virol. 72:2843, 1991. (3) S. K. Green et al. Plant Dis. 85:1286, 2001. (4) M. R. Rojas et al. Plant Dis. 77:340, 1993.
Mango (Mangifera indica L.; family Anacardiaceae) is one of the world's most important fruit crops and is widely grown in tropical and subtropical regions. Since 2001, a leaf spot disease was found in mango orchards of Taiwan. Now, the disease was observed throughout (approximately 21,000 ha) Taiwan in moderate to severe form, thus affecting the general health of mango trees and orchards. Initial symptoms were small, yellow-to-brown spots on leaves. Later, the irregularly shaped spots, ranging from a few millimeters to a few centimeters in diameter, turned white to gray and coalesced to form larger gray patches. Lesions had slightly raised dark margins. On mature lesions, numerous black acervuli, measuring 290 to 328 μm in diameter, developed on the gray necrotic areas. Single conidial isolates of the fungus were identified morphologically as Pestalotiopsis mangiferae (Henn.) Steyaert (2,3) and were consistently isolated from the diseased mango leaves on acidified (0.06% lactic acid) potato dextrose agar (PDA) medium incubated at 25 ± 1°C. Initially, the fungus grew (3 mm per day) on PDA as a white, chalky colony that subsequently turned gray after 2 weeks. Acervuli developed in culture after continuous exposure to light for 9 to 12 days at 20 to 30°C. Abundant conidia oozed from the acervulus as a creamy mass. The conidia (17.6 to 25.4 μm long and 4.8 to 7.1 μm wide) were fusiform and usually straight to slightly curved with four septa. Three median cells were olivaceous and larger than the hyaline apical and basal cells. The apical cells bore three (rarely four) cylindrical appendages. Pathogenicity tests were conducted with either 3-day-old mycelial discs or conidial suspension (105 conidia per ml) obtained from 8- to 10-day-old cultures. Four leaves on each of 10 trees were inoculated. Before inoculation, the leaves were washed with a mild detergent, rinsed with tap water, and then surface sterilized with 70% ethanol. Leaves were wounded with a needle and exposed to either a 5-mm mycelial disc or 0.2 ml of the spore suspension. The inoculated areas were wrapped with cotton pads saturated with sterile water and the leaves were covered with polyethylene bags for 3 days to maintain high relative humidity. Wounded leaves inoculated with PDA discs alone served as controls. The symptoms described above were observed on all inoculated leaves, whereas uninoculated leaves remained completely free from symptoms. Reisolation from the inoculated leaves consistently yielded P. mangiferae, thus fulfilling Koch's postulates. Gray leaf spot is a common disease of mangos in the tropics and is widely distributed in Africa and Asia (1-3); however, to our knowledge, this is the first report of gray leaf spot disease affecting mango in Taiwan. References: (1) T. K. Lim and K. C. Khoo. Diseases and Disorders of Mango in Malaysia. Tropical Press. Malaysia, 1985. (2) J. E. M. Mordue. No. 676 in: CMI Descriptions of Pathogenic Fungi and Bacteria. Surrey, England, 1980. (3) R. C. Ploetz et al. Compendium of Tropical Fruit Diseases. The American Phytopathological Society. St. Paul, MN, 1994.
A stem canker disease on rambutan (Nephelium lappaceum L.) and litchi (Litchi chinensis Sonn. (Sapindaceae) was found in plants in Hawaii and Puerto Rico. A fungus associated with cankers was identified as Dolabra nepheliae C. Booth & Ting (1). Numerous black, stipitate, elongate ascomata were produced within cracks of cankers. These ascomata contain elongate, bitunicate asci amid unbranched, interthecial elements and thin, cylindrical, hyaline ascospores measuring 96 to 136 × 2.5 to 3.5 μm. This fungus was originally described from Malaysia on N. lappaceum (1) and is also known on pulasan (N. mutabile Blume) in Australia (2). Classified by the Food and Agriculture Organization as a 'minor disease', the canker appears to be relatively common in Hawaii and was most likely introduced into Puerto Rico on imported germplasm. Nevertheless, efforts are underway to study the potential damage of this disease as well as mechanisms of control, including introduction of disease resistant clones. Specimens have been deposited at the U.S. National Fungus Collections (Hawaii on Nephelium BPI 878189, Puerto Rico (PR) on Nephelium BPI 878188, and PR on Litchi BPI 878190). Although a specimen of D. nepheliae on L. chinensis was collected from Hawaii in 1984 by G. Wong and C. Hodges and deposited as BPI 626373, this fungus was not known on Nephelium spp. in Hawaii and was not previously known from Puerto Rico on either host. References: (1) C. Booth and W. P. Ting. Trans. Brit. Mycol. Soc. 47:235, 1964. (2) T. K. Lim and Y. Diczbalis. Rambutan. Page 306 in: The New Rural Industries. Online publication. Rural Industries Research and Development Corporation, Australia, 1997.
Roselle, Hibiscus sabdariffa var. sabdariffa, is an annual that is grown primarily for its inflated calyx, which is used for drinks and jellies. It is native from India to Malaysia, but was taken at an early date to Africa and is now widely grown in the tropics and subtropics (2). In late 2005, dying plants were noted by a producer in South Florida. Plants wilted, became chlorotic, and developed generally unthrifty, sparse canopies. Internally, conspicuous vascular discoloration was evident in these plants from the roots into the canopy. After 5 days on one-half-strength potato dextrose agar (PDA), salmon-colored fungal colonies grew almost exclusively from surface-disinfested 5 mm2 pieces of vascular tissue. On banana leaf agar, single-spored strains produced the following microscopic characters of Fusarium oxysporum: copious microconidia on monophialides, infrequent falcate macroconidia, and terminal and intercalary chlamydospores. Partial, elongation factor 1-α (EF1-α) sequences were generated for two of the strains, O-2424 and O-2425, and compared with previously reported sequences for the gene (3). Maximum parsimony analysis of sequences showed that both strains fell in a large, previously described clade of the F. oxysporum complex (FOC) that contained strains from agricultural hosts, as well as human clinical specimens (2; clade 3 in Fig. 4); many of the strains in this clade have identical EF1-α sequences. Strains of F. oxysporum recovered from wilted roselle in Egypt, O-647 and O-648 in the Fusarium Research Center collection, were distantly related to the Florida strains. We are not aware of other strains of F. oxysporum from roselle in other international culture collections. Roselle seedlings were inoculated with O-2424 and O-2425 by placing a mycelial plug (5 mm2, PDA) over a small incision 5 cm above the soil line and then covering the site with Parafilm. Parafilm was removed after 1 week, and plants were incubated under ambient temperatures (20 to 32°C) in full sun for an additional 5 weeks (experiment 1) or 7 weeks (experiment 2). Compared with mock-inoculated (wound + Parafilm) control plants, both O-2424 and O-2425 caused significant (P < 0.05) vascular disease (linear extension of discolored xylem above and below wound site) and wilting (subjective 1 to 5 scale); both isolates were recovered from affected plants. F. oxysporum-induced wilt of roselle has been reported in Nigeria (1) and Malaysia (4) where the subspecific epithet f. sp. rosellae was used for the pathogen. We are not aware of reports of this disease elsewhere. To our knowledge, this is the first report of F. oxysporum-induced wilt of roselle in the United States. Research to determine whether the closely related strains in clade 3 of the FOC are generalist plant pathogens (i.e., not formae speciales) is warranted. References: (1) N. A. Amusa et al. Plant Pathol. J. 4:122, 2005. (2) J. Morton. Pages 81-286 in: Fruits of Warm Climates. Creative Resource Systems, Inc., Winterville, NC, 1987. (3) K. O'Donnell et al. J. Clin. Microbiol. 42:5109, 2004. (4) K. H. Ooi and B. Salleh. Biotropia 12:31, 1999.
Foreword. M K Rajakumar
Introduction: The transformation of health care in Malaysia. p1. CHEE HENG LENG AND SIMON BARRACLOUGH
PART I: The state and the private sector in the financing and provision of health care. p17
1 The growth of corporate health care in Malaysia. p19. CHEE HENG LENG AND SIMON BARRACLOUGH
2 Regulating Malaysia’s private health care sector. p40. NIK ROSNAH WAN ABDULLAH
3 Rising health care costs: the contradictory responses of the Malaysian state. p59. PHUA KAI LIT
4 Malaysian health policy in comparative perspective. p72. M. RAMESH
5 The welfarist state under duress: global influences and local contingencies in Malaysia. p85. CHAN CHEE KHOON
6 Equity in Malaysian health care: an analysis of public health expenditures and health care facilities. p102. WEE CHONG HUI AND JOMO K.S.
PART II: People’s access to health care. p117
7 Health care for the Orang Asli: consequences of paternalism and non-recognition. p119. COLIN NICHOLAS AND ADELA BAER
8 Women’s access to health care services in Malaysia. p137. CHEE HENG LENG AND WONG YUT LIN
9 HIV/AIDS health care policy and practice in Malaysia. p154. HUANG MARY S.L. AND MOHD NASIR MOHD TAIB
10 Health care and long-term care issues for the elderly. p170. ONG FON SIM
11 Health care in Sarawak: model of a public system. p187. KHOO KHAY JIN
Epilogue: Civil society and health care policy in Malaysia. p208. CHEE HENG LENG AND SIMON BARRACLOUGH
Index
MeSH terms: Aged; Delivery of Health Care; Economics; Health Expenditures; Health Policy; Health Services Accessibility; Malaysia; Rural Health; HIV Infections; Review; Health Care Costs; Private Sector; Public Sector; Healthcare Financing
Evaluation of: Jada SR, Lim R, Wong CI et al.: Role ofUGT1A1*6, UGT1A1*28 and ABCG2 c.421C>A polymorphisms in irinotecan-induced neutropenia in Asian cancer patients. Cancer Sci. 98(9), 1461-1467 (2007). The pharmacokinetics and toxicity of irinotecan vary widely among patients. This review focuses primarily on a study of the role of UGT1A1*6, UGT1A1*28, and ABCG2 421C>A in three Asian cancer patient populations treated with a 3-weekly regimen of irinotecan. In that study, a statistically significantly higher level of SN-38 and a relatively lower degree of glucuronidation occurred in patients with the UGT1A1*6 homozygote genotype than in patients with the reference genotype. The UGT1A1*6 allele was associated with an increased risk of severe neutropenia. In addition, the study of gene allele frequencies in three healthy Asian populations indicated that the allelic frequency of UGT1A1*6 was higher in the healthy Chinese subjects than in the Malaysian or Indian subjects. UGT1A1*28 and ABCG2 421C>A were not associated with the pharmacokinetics of SN-38 or the severity of neutropenia. In this evaluation, we put this study into the context of similar studies of irinogenetics (irinotecan pharmacogenetics) in Asians and discuss the application of UGT1A1 testing in Asian cancer patients treated with irinotecan-containing regimens.
During 2005, 764 children were brought to a large children's hospital in Ho Chi Minh City, Vietnam, with a diagnosis of hand, foot, and mouth disease. All enrolled children had specimens (vesicle fluid, stool, throat swab) collected for enterovirus isolation by cell culture. An enterovirus was isolated from 411 (53.8%) of the specimens: 173 (42.1%) isolates were identified as human enterovirus 71 (HEV71) and 214 (52.1%) as coxsackievirus A16. Of the identified HEV71 infections, 51 (29.5%) were complicated by acute neurologic disease and 3 (1.7%) were fatal. HEV71 was isolated throughout the year, with a period of higher prevalence in October-November. Phylogenetic analysis of 23 HEV71 isolates showed that during the first half of 2005, viruses belonging to 3 subgenogroups, C1, C4, and a previously undescribed subgenogroup, C5, cocirculated in southern Vietnam. In the second half of the year, viruses belonging to subgenogroup C5 predominated during a period of higher HEV71 activity.
MeSH terms: Adolescent; Animals; Cercopithecus aethiops; Child; Hand, Foot and Mouth Disease/epidemiology*; Hand, Foot and Mouth Disease/transmission; Hand, Foot and Mouth Disease/virology*; Humans; Phylogeny; Vero Cells; Vietnam/epidemiology; Reverse Transcriptase Polymerase Chain Reaction/methods; Enterovirus A, Human/genetics; Enterovirus A, Human/isolation & purification; Capsid Proteins/genetics; Cell Line, Tumor
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.
MeSH terms: Catechols; Cresols; Guaiacol; Reaction Time; Reproducibility of Results; Laccase; Chitosan; Benzothiazoles; Limit of Detection
An optical urea biosensor was fabricated by stacking several layers of sol-gelfilms. The stacking of the sol-gel films allowed the immobilization of a Nile Bluechromoionophore (ETH 5294) and urease enzyme separately without the need of anychemical attachment procedure. The absorbance response of the biosensor was monitoredat 550 nm, i.e. the deprotonation of the chromoionophore. This multi-layer sol-gel filmformat enabled higher enzyme loading in the biosensor to be achieved. The urea opticalbiosensor constructed from three layers of sol-gel films that contained urease demonstrateda much wider linear response range of up to 100 mM urea when compared with biosensorsthat constructed from 1-2 layers of films. Analysis of urea in urine samples with thisoptical urea biosensor yielded results similar to that determined by a spectrophotometricmethod using the reagent p-dimethylaminobenzaldehyde (R² = 0.982, n = 6). The averagerecovery of urea from urine samples using this urea biosensor is approximately 103%.