Displaying publications 1 - 20 of 41 in total

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  1. Perumal V, Hashim U, Gopinath SC, Haarindraprasad R, Foo KL, Balakrishnan SR, et al.
    Sci Rep, 2015 Jul 16;5:12231.
    PMID: 26178973 DOI: 10.1038/srep12231
    Hybrid gold nanostructures seeded into nanotextured zinc oxide (ZnO) nanoflowers (NFs) were created for novel biosensing applications. The selected 'spotted NFs' had a 30-nm-thick gold nanoparticle (AuNP) layer, chosen from a range of AuNP thicknesses, sputtered onto the surface. The generated nanohybrids, characterized by morphological, physical and structural analyses, were uniformly AuNP-seeded onto the ZnO NFs with an average length of 2-3 μm. Selective capture of molecular probes onto the seeded AuNPs was evidence for the specific interaction with DNA from pathogenic Leptospirosis-causing strains via hybridization and mis-match analyses. The attained detection limit was 100 fM as determined via impedance spectroscopy. High levels of stability, reproducibility and regeneration of the sensor were obtained. Selective DNA immobilization and hybridization were confirmed by nitrogen and phosphorus peaks in an X-ray photoelectron spectroscopy analysis. The created nanostructure hybrids illuminate the mechanism of generating multiple-target, high-performance detection on a single NF platform, which opens a new avenue for array-based medical diagnostics.
  2. Balakrishnan SR, Hashim U, Gopinath SC, Poopalan P, Ramayya HR, Iqbal Omar M, et al.
    PLoS One, 2015;10(9):e0137891.
    PMID: 26368287 DOI: 10.1371/journal.pone.0137891
    Human chorionic gonadotropin (hCG), a glycoprotein hormone secreted from the placenta, is a key molecule that indicates pregnancy. Here, we have designed a cost-effective, label-free, in situ point-of-care (POC) immunosensor to estimate hCG using a cuneated 25 nm polysilicon nanogap electrode. A tiny chip with the dimensions of 20.5 × 12.5 mm was fabricated using conventional lithography and size expansion techniques. Furthermore, the sensing surface was functionalized by (3-aminopropyl)triethoxysilane and quantitatively measured the variations in hCG levels from clinically obtained human urine samples. The dielectric properties of the present sensor are shown with a capacitance above 40 nF for samples from pregnant women; it was lower with samples from non-pregnant women. Furthermore, it has been proven that our sensor has a wide linear range of detection, as a sensitivity of 835.88 μA mIU(-1) ml(-2) cm(-2) was attained, and the detection limit was 0.28 mIU/ml (27.78 pg/ml). The dissociation constant Kd of the specific antigen binding to the anti-hCG was calculated as 2.23 ± 0.66 mIU, and the maximum number of binding sites per antigen was Bmax = 22.54 ± 1.46 mIU. The sensing system shown here, with a narrow nanogap, is suitable for high-throughput POC diagnosis, and a single injection can obtain triplicate data or parallel analyses of different targets.
  3. Perumal V, Hashim U, Gopinath SC, Haarindraprasad R, Poopalan P, Liu WW, et al.
    Biosens Bioelectron, 2016 Apr 15;78:14-22.
    PMID: 26584078 DOI: 10.1016/j.bios.2015.10.083
    Creating novel nanostructures is a primary step for high-performance analytical sensing. Herein, a new worm like nanostructure with Zinc Oxide-gold (ZnO/Au) hybrid was fabricated through an aqueous hydrothermal method, by doping Au-nanoparticle (AuNP) on the growing ZnO lattice. During ZnO growth, fine tuning the solution temperature expedites random curving of ZnO nanorods and forms nano-worms. The nano-worms which were evidenced by morphological, physical and structural analyses, revealed elongated structures protruding from the surface (length: 1 µm; diameter: ~100 nm). The appropriate peaks for the face centred cubic gold were (111) and (200), as seen from X-ray diffractogram. The strong interrelation between Au and ZnO was manifested by X-ray photoelectron spectroscopy. The combined surface area increment from the nanoparticle radii and ZnO nanorod random curving gives raise an enhancement in detection sensitivity by increasing bio-loading. 'Au-decorated hybrid nano-worm' was immobilized with a probe DNA from Vibrio Cholera and duplexed with a target which was revealed by Fourier Transform Infrared Spectroscopy. Our novel Au-decorated hybrid nano-worm is suitable for high-performance bio-sensing, as evidenced by impedance spectroscopy, having higher-specificity and attained femtomolar (10 fM) sensitivity. Further, higher stability, reproducibility and regeneration on this sensing surface were demonstrated.
  4. Wang F, Gopinath SC, Lakshmipriya T
    Int J Nanomedicine, 2019;14:8469-8481.
    PMID: 31695375 DOI: 10.2147/IJN.S219976
    BACKGROUND: A pandemic influenza viral strain, influenza A/California/07/2009 (pdmH1N1), has been considered to be a potential issue that needs to be controlled to avoid the seasonal emergence of mutated strains.

    MATERIALS AND METHODS: In this study, aptamer-antibody complementation was implemented on a multiwalled carbon nanotube-gold conjugated sensing surface with a dielectrode to detect pandemic pdmH1N1. Preliminary biomolecular and dielectrode surface analyses were performed by molecular and microscopic methods. A stable anti-pdmH1N1 aptamer sequence interacted with hemagglutinin (HA) and was compared with the antibody interaction. Both aptamer and antibody attachments on the surface as the basic molecule attained the saturation at nanomolar levels.

    RESULTS: Aptamers were found to have higher affinity and electric response than antibodies against HA of pdmH1N1. Linear regression with aptamer-HA interaction displays sensitivity in the range of 10 fM, whereas antibody-HA interaction shows a 100-fold lower level (1 pM). When sandwich-based detection of aptamer-HA-antibody and antibody-HA-aptamer was performed, a higher response of current was observed in both cases. Moreover, the detection strategy with aptamer clearly discriminated the closely related HA of influenza B/Tokyo/53/99 and influenza A/Panama/2007/1999 (H3N2).

    CONCLUSION: The high performance of the abovementioned detection methods was supported by the apparent specificity and reproducibility by the demonstrated sensing system.

  5. Gopinath SC, Lakshmipriya T, Chen Y, Phang WM, Hashim U
    Biotechnol Adv, 2016 May-Jun;34(3):198-208.
    PMID: 26876017 DOI: 10.1016/j.biotechadv.2016.02.003
    Aptamers are single-stranded oligonucleotides that can be artificially generated by a method called Systematic evolution of ligands by exponential enrichment (SELEX). The generated aptamers have been assessed for high-performance sensing applications due to their appealing characteristics. With either aptamers alone or complementing with antibodies, several high sensitive and portable sensors have been demonstrated for use in 'point-of-care testing'. Due to their high suitability and flexibility, aptamers are conjugated with nanostructures and utilized in field applications. Moreover, aptamers are more amenable to chemical modifications, making them capable of utilization with most developed sensors. In this overview, we discuss novel, portable, and aptamer-based sensing strategies that are suitable for 'point-of-care testing'.
  6. Toh SY, Citartan M, Gopinath SC, Tang TH
    Biosens Bioelectron, 2015 Feb 15;64:392-403.
    PMID: 25278480 DOI: 10.1016/j.bios.2014.09.026
    The application of antibodies in enzyme-linked immunosorbent assay (ELISA) is the basis of this diagnostic technique which is designed to detect a potpourri of complex target molecules such as cell surface antigens, allergens, and food contaminants. However, development of the systematic evolution of Ligands by Exponential Enrichment (SELEX) method, which can generate a nucleic acid-based probe (aptamer) that possess numerous advantages compared to antibodies, offers the possibility of using aptamers as an alternative molecular recognition element in ELISA. Compared to antibodies, aptamers are smaller in size, can be easily modified, are cheaper to produce, and can be generated against a wide array of target molecules. The application of aptamers in ELISA gives rise to an ELISA-derived assay called enzyme-linked apta-sorbent assay (ELASA). As with the ELISA method, ELASA can be used in several different configurations, including direct, indirect, and sandwich assays. This review provides an overview of the strategies involved in aptamer-based ELASA.
  7. Citartan M, Gopinath SC, Tominaga J, Tan SC, Tang TH
    Biosens Bioelectron, 2012 Apr 15;34(1):1-11.
    PMID: 22326894 DOI: 10.1016/j.bios.2012.01.002
    Aptamers are single stranded DNA or RNA oligonucleotides that have high affinity and specificity towards a wide range of target molecules. Aptamers have low molecular weight, amenable to chemical modifications and exhibit stability undeterred by repetitive denaturation and renaturation. Owing to these indispensable advantages, aptamers have been implemented as molecular recognition element as alternative to antibodies in various assays for diagnostics. By amalgamating with a number of methods that can provide information on the aptamer-target complex formation, aptamers have become the elemental tool for numerous biosensor developments. In this review, administration of aptamers in applications involving assays of fluorescence, electrochemistry, nano-label and nano-constructs are discussed. Although detection strategies are different for various aptamer-based assays, the core of the design strategies is similar towards reporting the presence of specific target binding to the corresponding aptamers. It is prognosticated that aptamers will find even broader applications with the development of new methods of transducing aptamer target binding.
  8. Gopinath SC, Tang TH, Chen Y, Citartan M, Lakshmipriya T
    Biosens Bioelectron, 2014 Oct 15;60:332-42.
    PMID: 24836016 DOI: 10.1016/j.bios.2014.04.014
    The ubiquitous nature of bacteria enables them to survive in a wide variety of environments. Hence, the rise of various pathogenic species that are harmful to human health raises the need for the development of accurate sensing systems. Sensing systems are necessary for diagnosis and epidemiological control of pathogenic organism, especially in the food-borne pathogen and sanitary water treatment facility' bacterial populations. Bacterial sensing for the purpose of diagnosis can function in three ways: bacterial morphological visualization, specific detection of bacterial component and whole cell detection. This paper provides an overview of the currently available bacterial detection systems that ranges from microscopic observation to state-of-the-art smartphone-based detection.
  9. Velusamy P, Su CH, Venkat Kumar G, Adhikary S, Pandian K, Gopinath SC, et al.
    PLoS One, 2016;11(6):e0157612.
    PMID: 27304672 DOI: 10.1371/journal.pone.0157612
    In the current study, facile synthesis of carboxymethyl cellulose (CMC) and sodium alginate capped silver nanoparticles (AgNPs) was examined using microwave radiation and aniline as a reducing agent. The biopolymer matrix embedded nanoparticles were synthesized under various experimental conditions using different concentrations of biopolymer (0.5, 1, 1.5, 2%), volumes of reducing agent (50, 100, 150 μL), and duration of heat treatment (30 s to 240 s). The synthesized nanoparticles were analyzed by scanning electron microscopy, UV-Vis spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy for identification of AgNPs synthesis, crystal nature, shape, size, and type of capping action. In addition, the significant antibacterial efficacy and antibiofilm activity of biopolymer capped AgNPs were demonstrated against different bacterial strains, Staphylococcus aureus MTCC 740 and Escherichia coli MTCC 9492. These results confirmed the potential for production of biopolymer capped AgNPs grown under microwave irradiation, which can be used for industrial and biomedical applications.
  10. Gopinath SC, Anbu P, Lakshmipriya T, Tang TH, Chen Y, Hashim U, et al.
    Biomed Res Int, 2015;2015:140726.
    PMID: 26180780 DOI: 10.1155/2015/140726
    Keratinases are proteolytic enzymes predominantly active when keratin substrates are available that attack disulfide bridges in the keratin to convert them from complex to simplified forms. Keratinases are essential in preparation of animal nutrients, protein supplements, leather manufacture, textile processing, detergent formulation, feather meal processing for feed and fertilizer, the pharmaceutical and biomedical industries, and waste management. Accordingly, it is necessary to develop a method for continuous production of keratinase from reliable sources that can be easily managed. Microbial keratinase is less expensive than conventionally produced keratinase and can be obtained from fungi, bacteria, and actinomycetes. In this overview, the expansion of information about microbial keratinases and important considerations in keratinase production are discussed.
  11. Gopinath SC, Anbu P, Arshad MK, Lakshmipriya T, Voon CH, Hashim U, et al.
    Biomed Res Int, 2017;2017:1272193.
    PMID: 28280725 DOI: 10.1155/2017/1272193
    Amylase is an important and indispensable enzyme that plays a pivotal role in the field of biotechnology. It is produced mainly from microbial sources and is used in many industries. Industrial sectors with top-down and bottom-up approaches are currently focusing on improving microbial amylase production levels by implementing bioengineering technologies. The further support of energy consumption studies, such as those on thermodynamics, pinch technology, and environment-friendly technologies, has hastened the large-scale production of the enzyme. Herein, the importance of microbial (bacteria and fungi) amylase is discussed along with its production methods from the laboratory to industrial scales.
  12. Lakshmipriya T, Gopinath SC, Tang TH
    PLoS One, 2016;11(3):e0151153.
    PMID: 26954237 DOI: 10.1371/journal.pone.0151153
    Enzyme Linked Immunosorbent Assay (ELISA) is the gold standard assay for detecting and identifying biomolecules using antibodies as the probe. Improving ELISA is crucial for detecting disease-causing agents and facilitating diagnosis at the early stages of disease. Biotinylated antibody and streptavidin-conjugated horse radish peroxide (streptavidin-HRP) often are used with ELISA to enhance the detection of various kinds of targets. In the present study, we used a competition-based strategy in which we pre-mixed free biotin with streptavidin-HRP to generate high-performance system, as free biotin occupies some of the biotin binding sites on streptavidin, thereby providing more chances for streptavidin-HRP to bind with biotinylated antibody. ESAT-6, which is a protein secreted early during tuberculosis infection, was used as the model target. We found that 8 fM of free biotin mixed with streptavidin-HRP anchored the higher detection level of ESAT-6 by four-fold compared with detection without free biotin (only streptavidin-HRP), and the limit of detection of the new method was 250 pM. These results suggest that biotin-streptavidin competition can be used to improve the diagnosis of analytes in other types of sensors.
  13. Arshad MK, Bin Mohamad Fathil MF, Gopinath SC, Ruslinda AR, Md Nor MN, Lam HY, et al.
    Curr Med Chem, 2016;23(37):4270-4284.
    PMID: 27719655
    Cardiovascular disease (CVD) is a major threat to global health, estimated to be the cause 30 % (17.3 million in 2008) of deaths every year, and the number of deaths caused by CVD is expected to increase further, reaching 23.3 million by 2030. Hence, there is a growing demand for simpler sample extraction, rapid screening results, and intervention of the subsequent analysis in emergency units. In this paper, we reviewed CVD biomarkers in blood- and saliva-based specimens. The history of cardiac biomarkers indicates that in the beginning, cardiac troponin I (cTnI) was a widely accepted 'gold standard' marker due to its high specificity and selectivity. Considering the advantages of salivary-based cardiac biomarkers, we examined correlations between non-invasive (salivary) and invasive (blood) diagnoses, and it was found that C-reactive protein (CRP) provides a better correlation. Despite the low abundance of salivary CRP, several reports displayed the detection limit down to pg/ml using existing technologies. Thus, salivary CRP has the potential to be used for future forefront diagnostics for the early assessment of cardiac risks.
  14. Gopinath SC, Lakshmipriya T, Chen Y, Arshad MK, Kerishnan JP, Ruslinda AR, et al.
    Appl Microbiol Biotechnol, 2016 Aug;100(16):6955-69.
    PMID: 27350620 DOI: 10.1007/s00253-016-7686-2
    Aptamers are single-stranded nucleic acids or peptides identified from a randomized combinatorial library through specific interaction with the target of interest. Targets can be of any size, from small molecules to whole cells, attesting to the versatility of aptamers for binding a wide range of targets. Aptamers show drug properties that are analogous to antibodies, with high specificity and affinity to their target molecules. Aptamers can penetrate disease-causing microbial and mammalian cells. Generated aptamers that target surface biomarkers act as cell-targeting agents and intracellular delivery vehicles. Within this context, the "cell-internalizing aptamers" are widely investigated via the process of cell uptake with selective binding during in vivo systematic evolution of ligands by exponential enrichment (SELEX) or by cell-internalization SELEX, which targets cell surface antigens to be receptors. These internalizing aptamers are highly preferable for the localization and functional analyses of multiple targets. In this overview, we discuss the ways by which internalizing aptamers are generated and their successful applications. Furthermore, theranostic approaches featuring cell-internalized aptamers are discussed with the purpose of analyzing and diagnosing disease-causing pathogens.
  15. Perumal V, Hashim U, Gopinath SC, Rajintra Prasad H, Wei-Wen L, Balakrishnan SR, et al.
    Nanoscale Res Lett, 2016 Dec;11(1):31.
    PMID: 26787050 DOI: 10.1186/s11671-016-1245-8
    Generation of hybrid nanostructures has been attested as a promising approach to develop high-performance sensing substrates. Herein, hybrid zinc oxide (ZnO) nanorod dopants with different gold (Au) thicknesses were grown on silicon wafer and studied for their impact on physical, optical and electrical characteristics. Structural patterns displayed that ZnO crystal lattice is in preferred c-axis orientation and proved the higher purities. Observations under field emission scanning electron microscopy revealed the coverage of ZnO nanorods by Au-spots having diameters in the average ranges of 5-10 nm, as determined under transmission electron microscopy. Impedance spectroscopic analysis of Au-sputtered ZnO nanorods was carried out in the frequency range of 1 to 100 MHz with applied AC amplitude of 1 V RMS. The obtained results showed significant changes in the electrical properties (conductance and dielectric constant) with nanostructures. A clear demonstration with 30-nm thickness of Au-sputtering was apparent to be ideal for downstream applications, due to the lowest variation in resistance value of grain boundary, which has dynamic and superior characteristics.
  16. Gopinath SC, Tang TH, Citartan M, Chen Y, Lakshmipriya T
    Biosens Bioelectron, 2014 Jul 15;57:292-302.
    PMID: 24607580 DOI: 10.1016/j.bios.2014.02.029
    Sensing applications can be used to report biomolecular interactions in order to elucidate the functions of molecules. The use of an analyte and a ligand is a common set-up in sensor development. For several decades, antibodies have been considered to be potential analytes or ligands for development of so-called "immunosensors." In an immunosensor, formation of the complex between antibody and antigen transduces the signal, which is measurable in various ways (e.g., both labeled and label-free based detection). Success of an immunosensor depends on various factors, including surface functionalization, antibody orientation, density of the antibody on the sensor platform, and configuration of the immunosensor. Careful optimization of these factors can generate clear-cut results for any immunosensor. Herein, current aspects, involved in the generated immunosensors, are discussed.
  17. Kerishnan JP, Gopinath SC, Kai SB, Tang TH, Ng HL, Rahman ZA, et al.
    Int J Med Sci, 2016;13(6):424-31.
    PMID: 27279791 DOI: 10.7150/ijms.14475
    The association between human papillomavirus type 16 (HPV16) and oral cancer has been widely reported. However, detecting anti-HPV antibodies in patient sera to determine risk for oral squamous cell carcinoma (OSCC) has not been well studied. In the present investigation, a total of 206 OSCC serum samples from the Malaysian Oral Cancer Database & Tissue Bank System, with 134 control serum samples, were analyzed by enzyme-linked immunosorbant assay (ELISA) to detect HPV16-specific IgG and IgM antibodies. In addition, nested PCR analysis using comprehensive consensus primers (PGMY09/11 and GP5(+)/6(+)) was used to confirm the presence of HPV. Furthermore, we have evaluated the association of various additional causal factors (e.g., smoking, alcohol consumption, and betel quid chewing) in HPV-infected OSCC patients. Statistical analysis of the Malaysian population indicated that OSCC was more prevalent in female Indian patients that practices betel quid chewing. ELISA revealed that HPV16 IgG, which demonstrates past exposure, could be detected in 197 (95.6%) OSCC patients and HPV16-specific IgM was found in a total of 42 (20.4%) OSCC patients, indicating current exposure. Taken together, our study suggest that HPV infection may play a significant role in OSCC (OR: 13.6; 95% CI: 3.89-47.51) and HPV16-specific IgG and IgM antibodies could represent a significant indicator of risk factors in OSCC patients.
  18. Fathil MF, Md Arshad MK, Gopinath SC, Hashim U, Adzhri R, Ayub RM, et al.
    Biosens Bioelectron, 2015 Aug 15;70:209-20.
    PMID: 25841117 DOI: 10.1016/j.bios.2015.03.037
    Acute myocardial infarction or myocardial infarction (MI) is a major health problem, due to diminished flow of blood to the heart, leads to higher rates of mortality and morbidity. Data from World Health Organization (WHO) accounted 30% of global death annually and expected more than 23 million die annually by 2030. This fatal effects trigger the need of appropriate biomarkers for early diagnosis, thus countermeasure can be taken. At the moment, the most specific markers for cardiac injury are cardiac troponin I (cTnI) and cardiac troponin T (cTnT) which have been considered as 'gold standard'. Due to higher specificity, determination of the level of cardiac troponins became a predominant indicator for MI. Several ways of diagnostics have been formulated, which include enzyme-linked immunosorbent assay, chemiluminescent, fluoro-immunoassays, electrical detections, surface plasmon resonance, and colorimetric protein assay. This review represents and elucidates the strategies, methods and detection levels involved in these diagnostics on cardiac superior biomarkers. The advancement, sensitivity, and limitations of each method are also discussed. In addition, it concludes with a discussion on the point-of care (POC) assay for a fast, accurate and ability of handling small sample measurement of cardiac biomarker.
  19. Haarindraprasad R, Hashim U, Gopinath SC, Perumal V, Liu WW, Balakrishnan SR
    Anal Chim Acta, 2016 Jun 21;925:70-81.
    PMID: 27188319 DOI: 10.1016/j.aca.2016.04.030
    Diabetes is a metabolic disease with a prolonged elevated level of glucose in the blood leads to long-term complications and increases the chances for cardiovascular diseases. The present study describes the fabrication of a ZnO nanowire (NW)-modified interdigitated electrode (IDE) to monitor the level of blood glucose. A silver IDE was generated by wet etching-assisted conventional lithography, with a gap between adjacent electrodes of 98.80 μm. The ZnO-based thin films and NWs were amended by sol-gel and hydrothermal routes. High-quality crystalline and c-axis orientated ZnO thin films were observed by XRD analyses. The ZnO thin film was annealed for 1, 3 and 5 h, yielding a good-quality crystallite with sizes of 50, 100 and 110 nm, and the band gaps were measured as 3.26, 3.20 and 3.17 eV, respectively. Furthermore, a flower-modeled NW was obtained with the lowest diameter of 21 nm. Our designed ZnO NW-modified IDE was shown to have a detection limit as low as 0.03 mg/dL (correlation coefficient = 0.98952) of glucose with a low response time of 3 s, perform better than commercial glucose meter, suitable to instantly monitor the glucose level of diabetes patients. This study demonstrated the high performance of NW-mediated IDEs for glucose sensing as alternative to current glucose sensors.
  20. Ge Y, Lakshmipriya T, Gopinath SC, Anbu P, Chen Y, Hariri F, et al.
    Int J Nanomedicine, 2019;14:7851-7860.
    PMID: 31632005 DOI: 10.2147/IJN.S222238
    BACKGROUND: Gestational diabetes mellitus is a commonly occurring metabolic disorder during pregnancy, affecting >4% of pregnant women. It is generally defined as the intolerance of glucose with the onset or initial diagnosis during pregnancy. This illness affects the placenta and poses a threat to the baby as it affects the supply of proper oxygen and nutrients.

    PURPOSE: Due to the high percentage of affected pregnant women, it should be mandatory to evaluate glucose levels during pregnancy and there is a need for a continuous monitoring system.

    METHODS: Herein, the investigators modified the interdigitated (di)electrodes (IDE) sensing surface to detect the glucose on covalently immobilized glucose oxidase (GOx) with the graphene. The characterization of graphene and gold nanoparticle (GNP) was performed by high-resolution microscopy.

    RESULTS: Sensitivity was found to be 0.06 mg/mL and to enhance the detection, GOx was complexed with GNP. GNP-GOx was improved the sensitive detection twofold from 0.06 to 0.03 mg/mL, and it also displayed higher levels of current changes at all the concentrations of glucose that were tested. High-performance of the above IDE sensing system was attested by the specificity, reproducibility and higher sensitivity detections. Further, the linear regression analysis indicated the limit of detection to be between 0.02 and 0.03 mg/mL.

    CONCLUSION: This study demonstrated the potential strategy with nanocomposite for diagnosing gestational diabetes mellitus.

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