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  1. Citartan M, Gopinath SC, Tominaga J, Tang TH
    Analyst, 2013 Jul 7;138(13):3576-92.
    PMID: 23646346 DOI: 10.1039/c3an36828a
    Reporting biomolecular interactions has become part and parcel of many applications of science towards an in-depth understanding of disease and gene regulation. Apart from that, in diagnostic applications where biomolecules (antibodies and aptamers) are vastly applied, meticulous monitoring of biomolecular interaction is vital for clear-cut diagnosis. Several currently available methods of analyzing the interaction of the ligands with the appropriate analytes are aided by labeling using fluorescence or luminescence techniques. However, labeling is cumbersome and can occupy important binding sites of interactive molecules to be labeled, which may interfere with the conformational changes of the molecules and increase non-specificity. Optical-based sensing can provide an alternative way as a label-free procedure for monitoring biomolecular interactions. Optical sensors affiliated with different operating principles, including surface plasmon changes, scattering and interferometry, can impart a huge impact for in-house and point-of-care applications. This optical-based biosensing permits real-time monitoring, obviating the use of hazardous labeling molecules such as radioactive tags. Herein, label-free ways of reporting biomolecular interactions by various optical biosensors were gleaned.
  2. Gopinath SC, Tang TH, Chen Y, Citartan M, Tominaga J, Lakshmipriya T
    Biosens Bioelectron, 2014 Nov 15;61:357-69.
    PMID: 24912036 DOI: 10.1016/j.bios.2014.05.024
    Influenza viruses, which are RNA viruses belonging to the family Orthomyxoviridae, cause respiratory diseases in birds and mammals. With seasonal epidemics, influenza spreads all over the world, resulting in pandemics that cause millions of deaths. Emergence of various types and subtypes of influenza, such as H1N1 and H7N9, requires effective surveillance to prevent their spread and to develop appropriate anti-influenza vaccines. Diagnostic probes such as glycans, aptamers, and antibodies now allow discrimination among the influenza strains, including new subtypes. Several sensors have been developed based on these probes, efforts made to augment influenza detection. Herein, we review the currently available sensing strategies to detect influenza viruses.
  3. Citartan M, Gopinath SC, Tominaga J, Chen Y, Tang TH
    Talanta, 2014 Aug;126:103-9.
    PMID: 24881539 DOI: 10.1016/j.talanta.2014.03.043
    Label-free-based detection is pivotal for real-time monitoring of biomolecular interactions and to eliminate the need for labeling with tags that can occupy important binding sites of biomolecules. One simplest form of label-free-based detection is ultraviolet-visible-near-infrared (UV-vis-NIR) spectroscopy, which measure changes in reflectivity as a means to monitor immobilization and interaction of biomolecules with their corresponding partners. In biosensor development, the platform used for the biomolecular interaction should be suitable for different molecular recognition elements. In this study, gold (Au)-coated polycarbonate was used as a platform and as a proof-of-concept, erythropoietin (EPO), a doping substance widely abused by the athletes was used as the target. The interaction of EPO with its corresponding molecular recognition elements (anti-EPO monoclonal antibody and anti-EPO DNA aptamer) is monitored by UV-vis-NIR spectroscopy. Prior to this, to show that UV-vis-NIR spectroscopy is a suitable method for measuring biomolecular interaction, the interaction between biotin and streptavidin was demonstrated via this strategy and reflectivity of this interaction decreased by 25%. Subsequent to this, interaction of the EPO with anti-EPO monoclonal antibody and anti-EPO DNA aptamer resulted in the decrease of reflectivity by 5% and 10%, respectively. The results indicated that Au-coated polycarbonate could be an ideal biosensor platform for monitoring biomolecular interactions using UV-vis-NIR spectroscopy. A smaller version of the Au-coated polycarbonate substrates can be derived from the recent set-up, to be applied towards detecting EPO abuse among atheletes.
  4. Marimuthu C, Tang TH, Tominaga J, Tan SC, Gopinath SC
    Analyst, 2012 Mar 21;137(6):1307-15.
    PMID: 22314701 DOI: 10.1039/c2an15905h
    The discovery that synthetic short chain nucleic acids are capable of selective binding to biological targets has made them to be widely used as molecular recognition elements. These nucleic acids, called aptamers, are comprised of two types, DNA and RNA aptamers, where the DNA aptamer is preferred over the latter due to its stability, making it widely used in a number of applications. However, the success of the DNA selection process through Systematic Evolution of Ligands by Exponential Enrichment (SELEX) experiments is very much dependent on its most critical step, which is the conversion of the dsDNA to ssDNA. There is a plethora of methods available in generating ssDNA from the corresponding dsDNA. These include asymmetric PCR, biotin-streptavidin separation, lambda exonuclease digestion and size separation on denaturing-urea PAGE. Herein, different methods of ssDNA generation following the PCR amplification step in SELEX are reviewed.
  5. 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.
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