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Ultrasensitive microfluidic chip could improve diabetes diagnoses

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Researchers from Zhejiang University (Zhejiang, China) and Hong Kong Polytechnic University (Kowloon, Hong Kong, China) are developing an ultrasensitive lab-on-a-chip device that may improve diabetes diagnosis and monitoring. The device integrates fiber optic glucose sensors into a microfluidic chip, which the researchers suggest may lead to a highly sensitive and low cost solution for bioanalysis of blood glucose concentration.

The device, reported in Biomedical Optics Express last week, utilizes the properties of both photonic sensing and microfluidic technologies.

Ping Zhang, Hong Kong Polytechnic University, commented: “Today, photonic approaches are recognized as the most promising techniques for ultrasensitive sensing. In particular, the synergistic integration of photonic sensing and microfluidics led to the state of the art technology known as ‘optofluidics’ for biological and chemical analysis.”

The researchers also highlighted the benefit of fiber optic sensors in comparison to electrochemical glucose sensors. Traditional electrochemical sensors may suffer from electroactive interference, whereas fiber optic sensors are immune to electromagnetic interference.

Zhang and the team developed the interference-free optofluidic device by inscribing a long-period grating in a small-diameter single-mode fiber for use as an optical refractive-index sensor.

Zhang explained: “Such fiber optic devices induce strong codirectional mode coupling through a resonant scattering process. And the resulting central wavelength is very sensitive to changes of the refractive index of the surrounding media via the evanescent field of optical fiber cladding mode.”

The team then employed glucose oxidase as a sensor to react with glucose in solution. A polyethylenimine and polyacrylic acid film was added to the sensor surface before immobilization of the sensing film, which detects glucose oxidation and reacts by swelling or contracting.

Experimental testing demonstrated that the fiber optic sensor is capable of detecting glucose oxidase at concentrations as low at 1 nM. Additionally, the sensor’s sensitivity was improved in terms of both detection range and response time following integration into the microfluidic chip.

The team hope that the device could ultimately be used in a clinical setting to rapidly detect glucose concentrations in small samples: for example, in a droplet of sweat.

“This makes it an extremely appealing technology to develop for early diagnosis of diabetes via monitoring glucose content within sweat,” Zhang added.

Going forward, the researchers aim to development multifunctional lab-on-a-chip devices, utilizing photonics, microfluidic and functional materials. Zhang commented: “Such a technology will enable a broad range of research and development in biomedical diagnostics, environmental monitoring and even aid drug discovery.”

Sources: Yin M-J, Huang B, Gao S, Zhang P and Ye X. Optical fiber LPG biosensor integrated microfluidic chip for ultrasensitive glucose detection. Biomed. Opt. Express 7, 2067–2077 doi:10.1364/BOE.7.002067 (2016); The Optical Society press release

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