Publications by authors named "Chiu-Wing Chan"

4 Publications

  • Page 1 of 1

"Barcode" cell sensor microfluidic system: Rapid and sample-to-answer antimicrobial susceptibility testing applicable in resource-limited conditions.

Biosens Bioelectron 2021 Nov 21;192:113516. Epub 2021 Jul 21.

Department of Chemistry, Hong Kong Baptist University. Waterloo Road, Kowloon, Hong Kong, China; HKBU Institute of Research and Continuing Education, Shenzhen, China; State Key Laboratory of Environmental and Biological Analysis, The Hong Kong Baptist University, Waterloo Road, Kowloon, Hong Kong, China. Electronic address:

Many rapid antimicrobial susceptibility testing (AST) methods have been proposed to contain clinical antimicrobial resistance (AMR) and preserve the effectiveness of remaining antimicrobials. However, far fewer methods have been proposed to test AMR in resource-limited conditions, such as for frequent safety screenings of water/food/public facilities, urgent surveys of massive samples during a pandemic, or AMR tests in low-income countries. Rapid AST methods realized thus far have a variety of drawbacks when used for such surveys, e.g., high cost and the requirement of expensive instruments such as microscopy. A more reasonable strategy would be to screen samples via onsite testing first, and then send any sample suspected to contain AMR bacteria for advanced testing. Accordingly, a cost-efficient AST is demanded, which can rapidly process a large number of samples without using expensive equipment. To this end, current work demonstrates a novel "barcode" cell sensor based on an adaptive linear filter array as a fully automatic and microscope-free method for counting very small volumes of cells (~1.00 × 10 cells without pre-incubation), wherein suspended cells concentrate into microbars with length proportional to the number of cells. We combined this sensor with an on-chip culture approach we had demonstrated for rapid and automated drug exposure and realized a low-cost and resource-independent platform for portable AST, from which results can be obtained simply through a cell phone. This method has a much shorter turnaround time (2-3 h) than that of standard methods (16-24 h). Thanks to its microscopy-free analysis, affordability, portability, high throughput, and user-friendliness, our "barcode" AST system has the potential to fulfill the various demands of AST when advanced facilities are not available, making it a promising new tool in the fight against AMR.
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http://dx.doi.org/10.1016/j.bios.2021.113516DOI Listing
November 2021

Defect-induced activity enhancement of enzyme-encapsulated metal-organic frameworks revealed in microfluidic gradient mixing synthesis.

Sci Adv 2020 01 29;6(5):eaax5785. Epub 2020 Jan 29.

Department of Chemistry, Hong Kong Baptist University, Hong Kong, P. R. China.

Mimicking the cellular environment, metal-organic frameworks (MOFs) are promising for encapsulating enzymes for general applications in environments often unfavorable for native enzymes. Markedly different from previous researches based on bulk solution synthesis, here, we report the synthesis of enzyme-embedded MOFs in a microfluidic laminar flow. The continuously changed concentrations of MOF precursors in the gradient mixing on-chip resulted in structural defects in products. This defect-generating phenomenon enables multimodal pore size distribution in MOFs and therefore allows improved access of substrates to encapsulated enzymes while maintaining the protection to the enzymes. Thus, the as-produced enzyme-MOF composites showed much higher (~one order of magnitude) biological activity than those from conventional bulk solution synthesis. This work suggests that while microfluidic flow synthesis is currently underexplored, it is a promising strategy in producing highly active enzyme-MOF composites.
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http://dx.doi.org/10.1126/sciadv.aax5785DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6989138PMC
January 2020

Reliable and reusable whole polypropylene plastic microfluidic devices for a rapid, low-cost antimicrobial susceptibility test.

Lab Chip 2019 09 1;19(17):2915-2924. Epub 2019 Aug 1.

Department of Chemistry, Hong Kong Baptist University, Waterloo Rd, Kowloon, Hong Kong, China. and HKBU Institute of Research and Continuing Education, Shenzhen, China and State Key Laboratory of Environmental and Biological Analysis, The Hong Kong Baptist University, Waterloo Rd, Kow-loon, Hong Kong, China.

Using an antimicrobial susceptibility test (AST) as an example, this work demonstrates a practical method to fabricate microfluidic chips entirely from polypropylene (PP) and the benefits for potential commercial use. Primarily caused by the misuse and abuse of antibiotics, antimicrobial resistance (AMR) is a major threat to modern medicine. The AST is a promising technique to help with the optimal use of antibiotics for reducing AMR. However, current phenotypic ASTs suffer from long turnaround time, while genotypic ASTs suffer from low reliability, and both are unaffordable for routine use. New microfluidics based AST methods are rapid but still unreliable as well as costly due to the PDMS chip material. Herein, we demonstrate a convenient method to fabricate whole PP microfluidic chips with high resolution and fidelity. Unlike PDMS chips, the whole PP chips showed better reliability due to their inertness; they are solvent-compatible and can be conveniently reused and recycled, which largely decreases the cost, and are environmentally friendly. We specially designed 3D chambers that allow for quick cell loading without valving/liquid exchange; this new hydrodynamic design satisfies the shear stress requirement for on-chip bacterial culture, which, compared to reported designs for similar purposes, allows for a simpler, more rapid, and high-throughput operation. Our system allows for reliable tracking of individual cells and acquisition of AST results within 1-3 hours, which is among the group of fastest phenotypic methods. The PP chips are more reliable and affordable than PDMS chips, providing a practical solution to improve current culture-based AST and benefiting the fight against AMR through helping doctors prescribe effective, narrow-spectrum antibiotics; they will also be broadly useful for other applications wherein a reliable, solvent-resistant, anti-fouling, and affordable microfluidic chip is needed.
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http://dx.doi.org/10.1039/c9lc00502aDOI Listing
September 2019

A one-step strategy for ultra-fast and low-cost mass production of plastic membrane microfluidic chips.

Lab Chip 2016 10;16(20):3909-3918

Department of Chemistry, Hong Kong Baptist University, Waterloo Rd, Kowloon, Hong Kong, China. and HKBU Institute of Research and Continuing Education, Shenzhen, China and State Key Laboratory of Environmental and Biological Analysis, The Hong Kong Baptist University, Waterloo Rd, Kowloon, Hong Kong, China.

An ultra-fast, extremely cost-effective, and environmentally friendly method was developed for fabricating flexible microfluidic chips with plastic membranes. With this method, we could fabricate plastic microfluidic chips rapidly (within 12 seconds per piece) at an extremely low cost (less than $0.02 per piece). We used a heated perfluoropolymer perfluoroalkoxy (often called Teflon PFA) solid stamp to press a pile of two pieces of plastic membranes, low density polyethylene (LDPE) and polyethylene terephthalate (PET) coated with an ethylene-vinyl acetate copolymer (EVA). During the short period of contact with the heated PFA stamp, the pressed area of the membranes permanently bonded, while the LDPE membrane spontaneously rose up at the area not pressed, forming microchannels automatically. These two regions were clearly distinguishable even at the micrometer scale so we were able to fabricate microchannels with widths down to 50 microns. This method combines the two steps in the conventional strategy for microchannel fabrication, generating microchannels and sealing channels, into a single step. The production is a green process without using any solvent or generating any waste. Also, the chips showed good resistance against the absorption of Rhodamine 6G, oligonucleotides, and green fluorescent protein (GFP). We demonstrated some typical microfluidic manipulations with the flexible plastic membrane chips, including droplet formation, on-chip capillary electrophoresis, and peristaltic pumping for quantitative injection of samples and reagents. In addition, we demonstrated convenient on-chip detection of lead ions in water samples by a peristaltic-pumping design, as an example of the application of the plastic membrane chips in a resource-limited environment. Due to the high speed and low cost of the fabrication process, this single-step method will facilitate the mass production of microfluidic chips and commercialization of microfluidic technologies.
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http://dx.doi.org/10.1039/c6lc00957cDOI Listing
October 2016
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