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Yu J.Q.,Nanyang Technological University | Huang W.,Nanyang Technological University | Chin L.K.,Nanyang Technological University | Lei L.,Nanyang Technological University | And 7 more authors.
Lab on a Chip - Miniaturisation for Chemistry and Biology | Year: 2014

Bacteriophages are considered as attractive indicators for determining drinking water quality since its concentration is strongly correlated with virus concentrations in water samples. Previously, bacteriophage detection was based on a plague assay that required a complicated labelling technique and a time-consuming culture assay. Here, for the first time, a label-free bacteriophage detection is reported by using droplet optofluidic imaging, which uses host-cell-containing microdroplets as reaction carriers for bacteriophage infection due to a higher contact ratio. The optofluidic imaging is based on the effective refractive index changes in the microdroplet correlated with the growth rate of the infected host cells, which is highly sensitive, i.e. can detect one E. coli cell. The droplet optofluidic system is not only used in drinking water quality monitoring, but also has high potential applications for pathogenic bacteria detection in clinical diagnosis and food industry. © 2014 the Partner Organisations.


Liu Y.,Nanyang Technological University | Chin L.K.,Nanyang Technological University | Ser W.,Nanyang Technological University | Ayi T.C.,Defence Medical and Environmental Institute | And 4 more authors.
17th International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2013 | Year: 2013

This paper presents a biophysical method to characterize single bacterium in water by using an on-chip immersion refractometer. The working principle is based on immersion refractometry, whereby the refractive index of a single bacterium is measured using the difference between the various refractive indices. The preliminary results show that E. coli is larger in term of width and has a lower refractive index value as compared to bacillus subtilis. The database for protozoa will be expanded by measuring different kinds of bacteria using the on-chip immersion refractometer. Copyright © (2013) by the Chemical and Biological Microsystems Society All rights reserved.


Liu P.Y.,University Paris Est Creteil | Liu P.Y.,Nanyang Technological University | Chin L.K.,Nanyang Technological University | Ser W.,Nanyang Technological University | And 4 more authors.
Conference on Lasers and Electro-Optics Europe - Technical Digest | Year: 2015

This paper presents an optofluidic imaging system to detect influenza virus infection via the change of refractive index based on scattering signature. This method allows for a direct monitor of the influenza flu virus. © 2015 OSA.


Liu P.Y.,University Paris Est Creteil | Liu P.Y.,Nanyang Technological University | Chin L.K.,Nanyang Technological University | Ser W.,Nanyang Technological University | And 4 more authors.
Lab on a Chip - Miniaturisation for Chemistry and Biology | Year: 2014

In this paper, for the first time, an on-chip optofluidic imaging system is innovated to measure the biophysical signatures of single waterborne bacteria, including both their refractive indices and morphologies (size and shape), based on immersion refractometry. The key features of the proposed optofluidic imaging platform include (1) multiple sites for single-bacterium trapping, which enable parallel measurements to achieve higher throughput, and (2) a chaotic micromixer, which enables efficient refractive index variation of the surrounding medium. In the experiments, the distinctive refractive index of Echerichia coli, Shigella flexneri and Vibrio cholera are measured with a high precision of 5 × 10-3 RIU. The developed optofluidic imaging system has high potential not only for building up a database of biophysical signatures of waterborne bacteria, but also for developing single-bacterium detection in treated water that is in real-time, label-free and low cost. This journal is © the Partner Organisations 2014.


Liu P.Y.,University Paris Est Creteil | Liu P.Y.,Nanyang Technological University | Chin L.K.,Nanyang Technological University | Ser W.,Nanyang Technological University | And 4 more authors.
Procedia Engineering | Year: 2014

This paper presents a biophysical method to characterize single bacterium in water by using an on-chip optofluidic immersion refractometer. Water safety is a major factor in the well-being of people, but the presence of bacteria such as Escherichia coli (E. coli), bacillus subtilis, Shigella flexneri and vibrio cholera in drinking water can lead to infectious diseases such as typhoid fever. Hence, it is crucial to detect and identify bacteria to prevent bacterial outbreaks. In this paper, an optofluidic immersion refractometer is developed to measure three biophysical parameters, i.e. size, shape and refractive index. The refractive index of a single bacterium is measured in high sensitivity of 0.005 RIU. This system is an innovative method to allow on-site real-time detection of single bacterium in water. It significantly reduces the amount of detection time and do not require trained personnel or additional chemical and biological reagents. © 2014 The Authors. Published by Elsevier Ltd.


PubMed | Defence Medical and Environmental Institute, Biodefence Center and London School of Hygiene and Tropical Medicine
Type: | Journal: Singapore medical journal | Year: 2016

Despite several phylogenetic studies on Plasmodium knowlesi (P. knowlesi), only cytochrome oxidase 1 (cox1) gene analysis has shown some geographical differentiation between the isolates of different countries.Phylogenetic analysis of locally acquired P. knowlesi infections, based on the circumsporozoite, small subunit ribosomal ribonucleic acid (SSU rRNA), merozoite surface protein 1 and cox1 gene targets, were performed. The results were compared with the published sequences of regional isolates from Malaysia and Thailand.Phylogenetic analysis of the circumsporozoite, SSU rRNA and merozoite surface protein 1 gene sequences for regional P. knowlesi isolates showed no obvious differentiation that could be attributed to their geographical origin. However, cox1 gene analysis showed that it was possible to differentiate between Singapore-acquired P. knowlesi infections and P. knowlesi infections from Peninsular Malaysia and Sarawak.The ability to differentiate between locally acquired P. knowlesi infections and imported P. knowlesi infections has important utility for the monitoring of P. knowlesi malaria control programmes in Singapore.


Liu P.Y.,University of Marne-la-Vallée | Liu P.Y.,Nanyang Technological University | Chin L.K.,Nanyang Technological University | Ser W.,Nanyang Technological University | And 4 more authors.
CLEO: QELS - Fundamental Science, CLEO_QELS 2015 | Year: 2015

This paper presents an optofluidic imaging system to detect influenza virus infection via the change of refractive index based on scattering signature. This method allows for a direct monitor of the influenza flu virus. 2015 © OSA 2015.


Chin L.K.,Nanyang Technological University | Ayi T.C.,Defence Medical and Environmental Institute | Yap P.H.,Defence Medical and Environmental Institute | Liu A.Q.,Nanyang Technological University
14th International Conference on Miniaturized Systems for Chemistry and Life Sciences 2010, MicroTAS 2010 | Year: 2010

This paper reports a continuous cell culture chip that employs droplet microfluidics to encapsulate suspension cells in a droplet and the cell droplet is passively stored in a storage chamber during the long-period cell culture process. The proposed system provides a closed micro-environment for cell culture which has advantages of cell droplet isolation to avoid cross contamination, simple droplet manipulation for fusion-division cycles and easy integration for further cell-based analytical techniques. In the demonstrated experiment, myeloma cells are successfully cultured using the developed integrated droplet cell culture system.


Chin L.K.,Nanyang Technological University | Ayi T.C.,Defence Medical and Environmental Institute | Yap P.H.,Defence Medical and Environmental Institute | Liu A.Q.,Nanyang Technological University
2011 16th International Solid-State Sensors, Actuators and Microsystems Conference, TRANSDUCERS'11 | Year: 2011

This paper presents an on-chip immersion refractometer for the measurement of size, shape and refractive index of protozoa in treated water. The key features of the on-chip immersion refractometer include (1) multiple single cyst trapping sites, which enable the measurement of multiple sample per test; and (2) zig-zag micromixer, which enables the refractive index variation of external medium as the key component of immersion refractometry. The results show that C. parvum oocysts have size of 3 to 7 m, spherical with ovality lower than 0.3, and refractive index of 1.418. G. lamblia cysts have size of 8 to 12 μm, oval with ovality higher than 0.3, and refractive index of 1.433. The refractive indices of the samples are measured with high precision of < 103. © 2011 IEEE.


Chin L.K.,Nanyang Technological University | Ayi T.C.,Defence Medical and Environmental Institute | Yap P.H.,Defence Medical and Environmental Institute | Liu A.Q.,Nanyang Technological University
15th International Conference on Miniaturized Systems for Chemistry and Life Sciences 2011, MicroTAS 2011 | Year: 2011

This paper presents an on-chip null-method immersion refractometer for the measurement of size, shape and refractive index of protozoa in treated water. The key features of the on-chip immersion refractometer include (1) multiple single cyst trapping sites, which enable the measurement of multiple sample per test; and (2) zig-zag micromixer, which enables the refractive index variation of external medium as the key component of immersion refractometry. The results show that Cryptosporidium parvum oocysts have size of 3 to 7 μm, spherical with ovality lower than 0.3, and refractive index of 1.418. Giardia lamblia cysts have size of 8 to 12 μm, oval with ovality higher than 0.3, and refractive index of 1.433. The refractive i ndices of the samples are measured with high precision of < 10-3. Copyright © (2011) by the Chemical and Biological Microsystems Society.

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