Displaying publications 1 - 20 of 65 in total

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  1. Yuhana Ariffin E, Heng LY, Tan LL, Abd Karim NH, Hasbullah SA
    Sensors (Basel), 2020 Feb 26;20(5).
    PMID: 32111092 DOI: 10.3390/s20051279
    A novel label-free electrochemical DNA biosensor was constructed for the determination of Escherichia coli bacteria in environmental water samples. The aminated DNA probe was immobilized onto hollow silica microspheres (HSMs) functionalized with 3-aminopropyltriethoxysilane and deposited onto a screen-printed electrode (SPE) carbon paste with supported gold nanoparticles (AuNPs). The biosensor was optimized for higher specificity and sensitivity. The label-free E. coli DNA biosensor exhibited a dynamic linear response range of 1 × 10-10 µM to 1 × 10-5 µM (R2 = 0.982), with a limit of detection at 1.95 × 10-15 µM, without a redox mediator. The sensitivity of the developed DNA biosensor was comparable to the non-complementary and single-base mismatched DNA. The DNA biosensor demonstrated a stable response up to 21 days of storage at 4 ℃ and pH 7. The DNA biosensor response was regenerable over three successive regeneration and rehybridization cycles.
  2. Yu X, Ng SF, Putri LK, Tan LL, Mohamed AR, Ong WJ
    Small, 2021 12;17(48):e2006851.
    PMID: 33909946 DOI: 10.1002/smll.202006851
    Graphitic carbon nitride (g-C3 N4 ) is a kind of ideal metal-free photocatalysts for artificial photosynthesis. At present, pristine g-C3 N4 suffers from small specific surface area, poor light absorption at longer wavelengths, low charge migration rate, and a high recombination rate of photogenerated electron-hole pairs, which significantly limit its performance. Among a myriad of modification strategies, point-defect engineering, namely tunable vacancies and dopant introduction, is capable of harnessing the superb structural, textural, optical, and electronic properties of g-C3 N4 to acquire an ameliorated photocatalytic activity. In view of the burgeoning development in this pacey field, a timely review on the state-of-the-art advancement of point-defect engineering of g-C3 N4 is of vital significance to advance the solar energy conversion. Particularly, insights into the intriguing roles of point defects, the synthesis, characterizations, and the systematic control of point defects, as well as the versatile application of defective g-C3 N4 -based nanomaterials toward photocatalytic water splitting, carbon dioxide reduction and nitrogen fixation will be presented in detail. Lastly, this review will conclude with a balanced perspective on the technical and scientific hindrances and future prospects. Overall, it is envisioned that this review will open a new frontier to uncover novel functionalities of defective g-C3 N4 -based nanostructures in energy catalysis.
  3. Yong SS, Kwan Z, Ch'ng CC, Yong ASW, Tan LL, Han WH, et al.
    BMC Geriatr, 2020 06 24;20(1):223.
    PMID: 32580764 DOI: 10.1186/s12877-020-01610-y
    BACKGROUND: The ageing skin is more susceptible to pruritic dermatoses, which are associated with adverse psychosocial effects and reduced quality of life among older adults. This cross-sectional study aimed to identify the burden of pruritus and factors associated with its presence and severity among older adults recruited to the Malaysian Elders Longitudinal Research study.

    METHODS: Seven hundred seventy individuals aged 55 years (lower age limit) and above were interviewed as to whether they experienced pruritus during the preceding week and the locations involved if present. The association between generalised pruritus, sleep quality, and major systemic risk factors were explored.

    RESULTS: 5.97% of respondents reported generalised pruritus. Generalised pruritus was associated with poorer sleep quality, with Pittsburgh Sleep Quality Index score above 6. Mean haemoglobin level was lower in subjects with generalised pruritus (13.14 g/dL) but there was no significant difference in the frequency of generalised pruritus and severe generalized pruritus between subjects with clinically defined anaemia. Also, there were no significant associations between other major systemic risk factors and generalised pruritus in this population-based study. There was no association between generalised pruritus with depression, anxiety or stress.

    CONCLUSION: The negative effect of pruritus on sleep quality suggests a possible deleterious effect of pruritus on health and quality of life. Further prospective research on the longer-term effects of pruritus on health status is now warranted. (222 words).

  4. Yong SS, Han WH, Faheem NAA, Puvan N, Tan LL, Wong SM, et al.
    Photodermatol Photoimmunol Photomed, 2022 Nov;38(6):541-547.
    PMID: 35324018 DOI: 10.1111/phpp.12787
    BACKGROUND: Airline pilots face significant ultraviolet radiation exposure resulting in an increased risk of sun damage and skin cancers. We aimed to evaluate sun-protective practices and associated factors among airline pilots.

    METHODS: We disseminated an online questionnaire evaluating the use of sunscreen, sunglasses, hats and protective clothing during daytime hours in the cockpit and during outdoor activities to 346 global commercial airline pilots, and we received 220 completed responses. The Pearson chi-squared test or Fisher's exact test where necessary were used to determine possible factors associated with the use of sun-protective practices. Potential confounders were adjusted for using multivariate analyses.

    RESULTS: The most common sun protective behaviour was the wearing of sunglasses during daytime flights (89.5%), followed by the use of caps during outdoor activities (47.7%). More pilots applied sunscreen during daytime flights (14.1%) compared with walk-arounds (8.2%). Males were less likely to use sunscreen during flights (adjusted odds ratio, aOR = 0.76), use sunscreen for walk-arounds (aOR = 0.175) and wear long sleeves (aOR = 0.013). Pilots who flew less than 30 h a month in high latitude regions were less likely to use a cap or hat outdoors (aOR = 0.419) or use sunscreen during walk-arounds (aOR = 0.241). Younger pilots were also less likely to use caps or hats outdoors (aOR = 0.446).

    CONCLUSION: Male pilots and those who spent less time in high latitudes were less likely to practice sun protection. Targeted educational efforts may be implemented to reduce occupational ultraviolet exposure.

  5. Yong SS, Robinson S, Kwan Z, Khoo EM, Han WH, Tan LL, et al.
    Psychol Health Med, 2023 Feb;28(2):324-335.
    PMID: 35057684 DOI: 10.1080/13548506.2022.2029914
    Patients with chronic spontaneous urticaria (CSU) have an increased risk of psychological distress. This cross-sectional study aimed to determine factors associated with psychological burden, quality of life (QoL) and patient satisfaction among adults living with CSU. Participants completed the self-administered Urticaria Activity Score-7 (UAS-7), Depression Anxiety Stress Scale (DASS 21), Dermatology Life Quality Index (DLQI), and Short Assessment Patient Satisfaction (SAPS) questionnaires. Multivariate logistic regression was used to determine the independent predictors of depression, anxiety, stress, QoL and patient satisfaction. From a total of 115 subjects with a median age of 42.6 years, range (19-89 years). 60.9% subjects reported moderate-to-severe CSU, 26.1% reported symptoms of depression, 54.8% had anxiety, 40.0% had stress, and 36.5% reported severely impaired QoL. The median UAS-7 score was 20 (IQR 11-27) while the median score of DLQI was 8 (IQR 4-13). The median score of SAPS was 20 (IQR 17-21). Low-income and severe disease were the significant predictors for depression while severe disease was predictive of impaired QoL and depression. Subjects who were diagnosed at older ages and those who required medical leave due to flares of CSU were less likely to be satisfied with their care. (192 words).
  6. Vaani VV, Tang MM, Tan LL, Asmah J
    Med J Malaysia, 2018 06;73(3):125-130.
    PMID: 29962494 MyJurnal
    INTRODUCTION: Ultraviolet phototherapies are important treatment modalities for a wide range of dermatological conditions. We aim to describe the utilization of phototherapy in the Department of Dermatology Hospital Kuala Lumpur.

    METHODS: This is a 5-year retrospective audit on patients who underwent phototherapy between 2011 and 2015.

    RESULTS: There were 892 patients, M:F=1.08:1, aged from 4- 88 years, with a median age of 38.8 years who underwent phototherapy. Majority (58.9%) had skin phototype IV, followed by type III (37.7%) and type II (0.7%). There were 697(78.1%) who underwent NBUVB, 136 (15.2%) had topical PUVA, 22(2.5%) had oral PUVA, 12(1.4%) had UVA1 and 23(2.6%) had NBUVB with topical or oral PUVA/UVA1 at different time periods. The indications were psoriasis (46.6%), vitiligo (26.7%), atopic eczema (9.8%), pityriasis lichenoides chronica (5.3%), mycosis fungoides (3.9%), lichen planus (2.5%), nodular prurigo (2.2%), scleroderma (1.2%), alopecia areata (0.7%) and others. The median number of session received were 27 (range 1-252) for NBUVB, 30 (range 1-330) for topical PUVA, 30 (range 3-190) for oral PUVA and 24.5 (range 2-161) for UVA1. The acute adverse effects experienced by patients were erythema (18%), pruritus (16.3%), warmth (3.3%), blister formation (3.1%), cutaneous pain (2.4%), and xerosis (0.8%), skin swelling (0.7%) and phototoxicity (0.2%).

    CONCLUSION: Narrow-band UVB was the most frequently prescribed phototherapy modality in our center. The most common indication for phototherapy in our setting was psoriasis. Acute adverse events occurred in a third of patients, although these side effects were mild.

  7. Tan LL, Lau TY, Timothy W, Prabakaran D
    ScientificWorldJournal, 2014;2014:935846.
    PMID: 25574497 DOI: 10.1155/2014/935846
    Chloroquine resistance (CQR) in falciparum malaria was identified to be associated with several mutations in the chloroquine resistance transporter gene (pfcrt) that encodes the transmembrane transporter in digestive vacuole membrane of the parasite. This study aimed to investigate the point mutations across the full-length pfcrt in Plasmodium falciparum isolates in Sabah, Malaysia. A total of 31 P. falciparum positive samples collected from Keningau, Kota Kinabalu, and Kudat, Sabah, were analyzed. pfcrt was PCR amplified and cloned prior to sequence analysis. This study showed that all the previously described 10 point mutations associated with CQR at codons 72, 74, 75, 76, 97, 220, 271, 326, 356, and 371 were found with different prevalence. Besides, two novel point mutations, I166V and H273N, were identified with 22.5% and 19.3%, respectively. Three haplotypes, namely, CVMNK (29%), CVIET (3.2%), and SVMNT (67.7%), were identified. High prevalence of SVMNT among P. falciparum isolates from Sabah showed that these isolates are closer to the P. falciparum isolates from Papua New Guinea rather than to the more proximal Southeast Asian CVIET haplotype. Full-length analysis of pfcrt showed that chloroquine resistant P. falciparum in Sabah is still prevalent despite the withdrawal of chloroquine usage since 1979.
  8. Tan LL, Ong WJ, Chai SP, Mohamed AR
    Chem Commun (Camb), 2014 Jul 4;50(52):6923-6.
    PMID: 24841282 DOI: 10.1039/c4cc01304b
    A facile and dopant-free strategy was employed to fabricate oxygen-rich TiO2 (O2-TiO2) with enhanced visible light photoactivity. Such properties were achieved by the in situ generation of oxygen through the thermal decomposition of the peroxo-titania complex. The O2-TiO2 photocatalyst exhibited high photoactivity towards CO2 reduction under visible light.
  9. Tan LL, Ong WJ, Chai SP, Mohamed AR
    Nanoscale Res Lett, 2013;8(1):465.
    PMID: 24195721 DOI: 10.1186/1556-276X-8-465
    Photocatalytic reduction of carbon dioxide (CO2) into hydrocarbon fuels such as methane is an attractive strategy for simultaneously harvesting solar energy and capturing this major greenhouse gas. Incessant research interest has been devoted to preparing graphene-based semiconductor nanocomposites as photocatalysts for a variety of applications. In this work, reduced graphene oxide (rGO)-TiO2 hybrid nanocrystals were fabricated through a novel and simple solvothermal synthetic route. Anatase TiO2 particles with an average diameter of 12 nm were uniformly dispersed on the rGO sheet. Slow hydrolysis reaction was successfully attained through the use of ethylene glycol and acetic acid mixed solvents coupled with an additional cooling step. The prepared rGO-TiO2 nanocomposites exhibited superior photocatalytic activity (0.135 μmol gcat-1 h-1) in the reduction of CO2 over graphite oxide and pure anatase. The intimate contact between TiO2 and rGO was proposed to accelerate the transfer of photogenerated electrons on TiO2 to rGO, leading to an effective charge anti-recombination and thus enhancing the photocatalytic activity. Furthermore, our photocatalysts were found to be active even under the irradiation of low-power energy-saving light bulbs, which renders the entire process economically and practically feasible.
  10. Tan LL, Chai SP, Mohamed AR
    ChemSusChem, 2012 Oct;5(10):1868-82.
    PMID: 22987439 DOI: 10.1002/cssc.201200480
    Graphene is one of the most promising materials in the field of nanotechnology and has attracted a tremendous amount of research interest in recent years. Due to its large specific surface area, high thermal conductivity, and superior electron mobility, graphene is regarded as an extremely attractive component for the preparation of composite materials. At the same time, the use of photocatalysts, particularly TiO(2), has also been widely studied for their potential in addressing various energy and environmental-related issues. However, bare TiO(2) suffers from low efficiency and a narrow light-response range. Therefore, the combination of graphene and TiO(2) is currently one of the most active interdisciplinary research areas and demonstrations of photocatalytic enhancement are abundant. This Review presents and discusses the current development of graphene-based TiO(2) photocatalysts. The theoretical framework of the composite, the synthetic strategies for the preparation and modification of graphene-based TiO(2) photocatalysts, and applications of the composite are reviewed, with particular attention on the photodegradation of pollutants and photocatalytic water splitting for hydrogen generation.
  11. Tan LL, Musa A, Lee YH
    Sensors (Basel), 2011;11(10):9344-60.
    PMID: 22163699 DOI: 10.3390/s111009344
    The use of the enzyme alanine dehydrogenase (AlaDH) for the determination of ammonium ion (NH(4)(+)) usually requires the addition of pyruvate substrate and reduced nicotinamide adenine dinucleotide (NADH) simultaneously to effect the reaction. This addition of reagents is inconvenient when an enzyme biosensor based on AlaDH is used. To resolve the problem, a novel reagentless amperometric biosensor using a stacked methacrylic membrane system coated onto a screen-printed carbon paste electrode (SPE) for NH(4)(+) ion determination is described. A mixture of pyruvate and NADH was immobilized in low molecular weight poly(2-hydroxyethyl methacrylate) (pHEMA) membrane, which was then deposited over a photocured pHEMA membrane (photoHEMA) containing alanine dehydrogenase (AlaDH) enzyme. Due to the enzymatic reaction of AlaDH and the pyruvate substrate, NH(4)(+) was consumed in the process and thus the signal from the electrocatalytic oxidation of NADH at an applied potential of +0.55 V was proportional to the NH(4)(+) ion concentration under optimal conditions. The stacked methacrylate membranes responded rapidly and linearly to changes in NH(4)(+) ion concentrations between 10-100 mM, with a detection limit of 0.18 mM NH(4)(+) ion. The reproducibility of the amperometrical NH(4)(+) biosensor yielded low relative standard deviations between 1.4-4.9%. The stacked membrane biosensor has been successfully applied to the determination of NH(4)(+) ion in spiked river water samples without pretreatment. A good correlation was found between the analytical results for NH(4)(+) obtained from the biosensor and the Nessler spectrophotometric method.
  12. Tan LL, Ahmad K, Kareem BA, Harwant S
    Med J Malaysia, 2001 Jun;56 Suppl C:52-6.
    PMID: 11814250 MyJurnal
    An epidemiological study of 101 consecutive musculoskeletal sarcomas seen at the Institute of Radiotherapy and Oncology between 1995 and 1999 inclusive was carried out. The commonest sarcomas seen were osteosarcoma, rhabdomyosarcoma, Ewing's Sarcoma, liposarcoma, leimyosarcoma, malignant fibrous histiocytoma and chondrosarcoma; which collectively accounted for 84.2% of the group. Thirty patients (29.7%) presented with metastases. The commonest site of occurrence was lower extremity with 47.5%, followed by 34.7% in the trunk and peritoneum/axial skeleton, 9.9% in the head and neck region; and 7.90 in the upper extremity. We found no apparent relationship between race and incidence osteosarcoma and Ewing's sarcoma, as was reported by previous workers.
  13. Tan LL, Ahmed SA, Ng SK, Citartan M, Raabe CA, Rozhdestvensky TS, et al.
    Food Chem, 2020 Mar 30;309:125654.
    PMID: 31678669 DOI: 10.1016/j.foodchem.2019.125654
    A specialized DNA extraction method and a SYBR Green quantitative polymerase chain reaction (SyG-qPCR) assay were combined to generate a ready-to-use kit for rapid detection of porcine admixtures in processed meat products. Our qPCR assay utilized repetitive LINE-1 elements specific to the genome of Sus scrofa domesticus (pig) as a target and incorporated internal controls. We improved the genomic DNA extraction method, and reduced extraction times to the minimum. The method was validated for specificity, sensitivity (0.001% w/w) and robustness, and values were compared with those of a commercially available kit. We also tested our method using 121 processed food products and consistently detected amplification only in samples containing pork. Due to its efficiency and cost-effectiveness, our method represents a valuable new method for detecting food adulteration with pork that is superior to existing quality control approaches.
  14. Taib M, Tan LL, Abd Karim NH, Ta GC, Heng LY, Khalid B
    Talanta, 2020 Jan 15;207:120321.
    PMID: 31594568 DOI: 10.1016/j.talanta.2019.120321
    An optical aptasensor-based sensing platform for rapid insulin detection was fabricated. Aminated porous silica microparticles (PSiMPs) were synthesized via a facile mini-emulsion method to provide large surface area for covalent immobilization of insulin-binding DNA aptamer (IGA3) by glutaraldehyde cross-linking protocol. A Nickel-salphen type complex with piperidine side chain [Ni(II)-SP] was synthesized with a simple one-pot reaction, and functionalized as an optical label due to strong π-π interaction between aromatic carbons of G-quadruplex DNA aptamer and planar aromatic groups of Ni(II)-SP to form the immobilized IGA3-Ni(II)-SP complex, i.e. the dye-labeled aptamer, thereby bringing yellow colouration to the immobilized G-quartet plane. Optical characterization of aptasensor towards insulin binding was carried out with a fiber optic reflectance spectrophotometer. The maximum reflectance intensity of the immobilized IGA3-Ni(II)-SP complex at 656 nm decreased upon binding with insulin as aptasensor changed to brownish orange colouration in the background. This allows optical detection of insulin as the colour change of aptasensor is dependent on the insulin concentration. The linear detection range of the aptasensor is obtained from 10 to 50 μIU mL-1 (R2 = 0.9757), which conformed to the normal fasting insulin levels in human with a limit of detection (LOD) at 3.71 μIU mL-1. The aptasensor showed fast response time of 40 min and long shelf life stability of >3 weeks. Insulin detection using healthy human serums with informed consent provided by participants suggests the DNA aptamer biosensor was in good agreement with ELISA standard method using BIOMATIK Human INS (Insulin) ELISA Kit.
  15. Sonthanasamy RSA, Sulaiman NMN, Tan LL, Lazim AM
    PMID: 30954801 DOI: 10.1016/j.saa.2019.03.108
    Carbon dots (C-dots) were used to study the binding mechanisms with serum protein, bovine serum albumin (BSA) by using two notable binding systems known as non-covalent and covalent interaction. Interaction between C-dots and BSA were estimated by Stern-Volmer equation and Double Log Regression Model (DLRM). According to the fluorescent intensity, quenching of model carrier protein by C-dots was due to dynamic quenching for non-covalent and static quenching for covalent binding. The binding site constant, KA and number of binding site, for covalent interaction is 1754.7L/mol and n≈1 (0.6922) were determined by DLRM on fluorescence quenching results. The blue shift of the fluorescence spectrum, from 450nm to 421nm (non-covalent) and 430nm (covalent) and suggested that both the microenvironment of C-dots and protein changed in relation to the protein concentration. The fluorescence intensity results show that protein structure has a significant role in Protein-C-dots interactions and type of binding influence physicochemical properties of C-dots differently. Understanding to this bio interface is important to utilize both quantum dots and biomolecules for biomedical field. It can be a useful guideline to design further applications in biomedical and bioimaging.
  16. Seng RX, Tan LL, Lee WPC, Ong WJ, Chai SP
    J Environ Manage, 2020 Feb 01;255:109936.
    PMID: 32063312 DOI: 10.1016/j.jenvman.2019.109936
    Growing concerns of water pollution by dye pollutants from the textile industry has led to vast research interest to find green solutions to address this issue. In recent years, heterogeneous photocatalysis has harvested tremendous attention from researchers due to its powerful potential applications in tackling many important energy and environmental challenges at a global level. To fully utilise the broad spectrum of solar energy has been a common aim in the photocatalyst industry. This study focuses on the development of an efficient, highly thermal and chemical stable, environmentally friendly and metal-free graphitic carbon nitride (g-C3N4) to overcome the problem of fast charge recombination which hinders photocatalytic performances. Nitrogen-doped carbon quantum dots (NCQDs) known for its high electronic and optical functionality properties is believed to achieve photocatalytic enhancement by efficient charge separation through forming heterogeneous interfaces. Hence, the current work focuses on the hybridisation of NCQDs and g-C3N4 to produce a composite photocatalyst for methylene blue (MB) degradation under LED light irradiation. The optimal hybridisation method and the mass loading required for maximum attainable MB degradation were systematically investigated. The optimum photocatalyst, 1 wt% NCQD/g-C3N4 composite was shown to exhibit a 2.6-fold increase in photocatalytic activity over bare g-C3N4. Moreover, the optimum sample displayed excellent stability and durability after three consecutive degradation cycles, retaining 91.2% of its original efficiency. Scavenging tests were also performed where reactive species, photon-hole (h+) was identified as the primary active species initiating the pollutant degradation mechanism. The findings of this study successfully shed light on the hybridisation methods of NCQDs which improve existing g-C3N4 photocatalyst systems for environmental remediation by utilising solar energy.
  17. Sahudin MA, Su'ait MS, Tan LL, Lee YH, Abd Karim NH
    Anal Bioanal Chem, 2019 Sep;411(24):6449-6461.
    PMID: 31392436 DOI: 10.1007/s00216-019-02025-4
    Biogenic amines have attracted interest among researchers because of their importance as biomarkers in determining the quality of food freshness in the food industry. A rapid and simple technique that is able to detect biogenic amines is needed. In this work, a new optical sensing material for one of the biogenic amines, histamine, based on a new zinc(II) salphen complex was developed. The binding of zinc(II) complexes without an electron-withdrawing group (complex 1) and with electron-withdrawing groups (F, complex 2; Cl, complex 3) to histamine resulted in enhancement of fluorescence. All complexes exhibited high affinity for histamine [binding constant of (7.14 ± 0.80) × 104, (3.33 ± 0.03) × 105, and (2.35 ± 0.14) × 105 M-1, respectively]. Complex 2 was chosen as the sensing material for further development of an optical sensor for biogenic amines in the following step since it displayed enhanced optical properties in comparison with complexes 1 and 3. The optical sensor for biogenic amines used silica microparticles as the immobilisation support and histamine as the analyte. The optical sensor had a limit of detection for histamine of 4.4 × 10-12 M, with a linear working range between 1.0 × 10-11 and 1.0 × 10-6 M (R2 = 0.9844). The sensor showed good reproducibility, with a low relative standard deviation (5.5 %). In addition, the sensor exhibited good selectivity towards histamine and cadaverine over other amines, such as 1,2-phenylenediamine, triethylamine, and trimethylamine. Recovery and real sample studies suggested that complex 2 could be a promising biogenic amine optical sensing material that can be applied in the food industry, especially in controlling the safety of food for it to remain fresh and healthy for consumption.
  18. Sahudin MA, Su'ait MS, Tan LL, Abd Karim NH
    PMID: 33281086 DOI: 10.1016/j.saa.2020.119129
    Histamine is one of the important biomarkers for food spoilage in the food sectors. In the present study, a rapid and simple analytical tool has been developed to detect histamine as an indirect strategy to monitor food freshness level. Optical histamine sensor with carboxyl-substituted Schiff base zinc(II) complex with hydroxypropoxy side chain deposited onto titanium dioxide nanoparticles was fabricated and was found to respond successfully to histamine. The Schiff base zinc(II) complex-histamine binding generated an enhancement of the fluorescent signal. Under the optimal reaction condition, the developed sensor can detect down to 2.53 × 10-10 M in the range of between 1.0 × 10-9 and 1.0 × 10-5 M (R2 = 0.9868). Selectivity performance of the sensor towards histamine over other amines was confirmed. The sensor also displayed good reproducibility performances with low relative standard deviation values (1.45%-4.95%). Shelf-life studies suggested that the developed sensor remains stable after 60 days in histamine detection. More importantly, the proposed sensor has been successfully applied to determine histamine in salmon fillet with good recoveries. This strategy has a promising potential in the food quality assurance sectors, especially in controlling the food safety for healthy consumption among consumers.
  19. Raja Jamaluddin RZA, Yook Heng L, Tan LL, Chong KF
    Sensors (Basel), 2018 Apr 26;18(5).
    PMID: 29701688 DOI: 10.3390/s18051343
    A new biosensor for the analysis of nitrite in food was developed based on hemoglobin (Hb) covalently immobilized on the succinimide functionalized poly(n-butyl acrylate)-graphene [poly(nBA)-rGO] composite film deposited on a carbon-paste screen-printed electrode (SPE). The immobilized Hb on the poly(nBA)-rGO conducting matrix exhibited electrocatalytic ability for the reduction of nitrite with significant enhancement in the reduction peak at −0.6 V versus Ag/AgCl reference electrode. Thus, direct determination of nitrite can be achieved by monitoring the cathodic peak current signal of the proposed polyacrylic-graphene hybrid film-based voltammetric nitrite biosensor. The nitrite biosensor exhibited a reproducible dynamic linear response range from 0.05⁻5 mg L−1 nitrite and a detection limit of 0.03 mg L−1. No significant interference was observed by potential interfering ions such as Ca2+, Na⁺, K⁺, NH₄⁺, Mg2+, and NO₃− ions. Analysis of nitrite in both raw and processed edible bird’s nest (EBN) samples demonstrated recovery of close to 100%. The covalent immobilization of Hb on poly(nBA)-rGO composite film has improved the performance of the electrochemical nitrite biosensor in terms of broader detection range, lower detection limit, and prolonged biosensor stability.
  20. Raja Jamaluddin RZA, Tan LL, Chong KF, Heng LY
    Nanotechnology, 2020 Nov 27;31(48):485501.
    PMID: 32748805 DOI: 10.1088/1361-6528/abab2e
    Graphene decorated with graphitic nanospheres functionalized with pyrene butyric acid (PBA) is used for the first time to fabricate a DNA biosensor. The electrode was formed by attaching a DNA probe onto PBA, which had been stacked onto a graphene material decorated with graphene nanospheres (GNSs). The nanomaterial was drop-coated onto a carbon screen-printed electrode (SPE) to create the GNS-PBA modified electrode (GNS-PBA/SPE). A simple method was used to produce GNS by annealing graphene oxide (GO) solution at high temperature. Field emission scanning electron micrographs confirmed the presence of a spherical shape of GNS with a diameter range of 40-80 nm. A stable and uniform PBA-modified GNS (GNS-PBA) was obtained with a facile ultrasonication step. Thus allowing aminated DNA probes of genetically modified (GM) soybean to be attached to the nanomaterials to form the DNA biosensor. The GNS-PBA/SPE exhibited excellent electrical conductivity via cyclic voltammetry (CV) and differential pulse voltammetry (DPV) tests using potassium ferricyanide (K3[Fe(CN)6]) as the electroactive probe. By employing an anthraquinone monosulfonic acid (AQMS) redox intercalator as the DNA hybridization indicator, the biosensor response was evaluated using the DPV electrochemical method. A good linear relationship between AQMS oxidation peak current and target DNA concentrations from 1.0 × 10-16 to 1.0 × 10-8 M with a limit of detection (LOD) of less than 1.0 × 10-16 M was obtained. Selectivity experiments revealed that the voltammetric GM DNA biosensor could discriminate complementary sequences of GM soybean from non-complementary sequences and hence good recoveries were obtained for real GM soybean sample analysis. The main advantage of using GNS is an improvement of the DNA biosensor analytical performance.
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