• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2688-2691
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• 2008

This study addresses a microfluidic method to uniformly form diacetylene (DA) liposomes and control their size. DA liposomes are biochemical sensor materials with a unique property such that when they are polymerized to polydiacetylene (PDA) they exhibit non-fluorescent blue to fluorescent red phase transition upon chemical or thermal stress. The liposome size and distribution are important because they significantly affect the phase transition. So far, DA Liposomes, have been prepared by mixing of bulk phases leading to heterogeneous, polydisperse distribution in size. Therefore, additional post-processes are required such as sonication or membrane extrusion to obtain an appropriate size of liposomes. Here, we report a novel strategy using a microfluidic chip and hydrodynamic focusing to form DA liposomes and control their size. Preliminary results obtained by scanning electron microscope (SEM) and dynamic light scattering (DLS) show that the microfluidic strategy generates more monodispersed liposomes than a bulk method.

• Polymer Science and Technology
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• v.23 no.6
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• pp.608-614
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• 2012

• Korean Chemical Engineering Research
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• v.49 no.4
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• pp.400-404
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• 2011

Many studies on polydiacetylene(PDA) have been investigated to apply to chemical and biological sensors due to their unique optical properties of color change from blue to red and fluorescence change from non-fluorescence to red fluorescence. Especially, high sensitivity against specific molecules is very important to apply polydiacetylenes to various sensors. In this study, we examined the effect of sensitivity enhancement of 10,12-pentacosadynoic acid(PCDA) vesicles in detection ${\alpha}$-cyclodextrin(CD) according to control of vesicle size by filters with different pore sizes and polymerization temperature. Colorimetric response(CR) was calculated using visible spectrometer. In order to investigate the effect of vesicle size on sensitivity of PDA vesicles, two PCDA vesicles were filtered without filtration and with 0.22 ${\mu}m$ filter. The two PCDA vesicles were polymerized at $25^{\circ}C$ and were incubated with ${\alpha}$-CD(5 mM) for 30 min. The CRs of the former and latter vesicles were 31.4% and 74.0%, respectively. Then, two PCDA vesicles filtered with 0.22 ${\mu}m$ filter were polymerized at $25^{\circ}C$ and $5^{\circ}C$ and were reacted with ${\alpha}$-CD(5 mM) for 30 min to examine the effect of polymerization temperature. The CRs of the former and latter vesicles were 74.0 and 99.2%, respectively. This suggests that vesicle sizes and polymerization temperature are key factors in enhancing the sensitivity of PDA vesicles. In addition, these results are expected to be useful to apply the PDA vesicles as biosensors to detect DNA, protein, and cells.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2415-2418
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• 2008

Polydiacetylenes (PDAs) are very attractive chemical substances which have distinctive features of color change and fluorescence emission by thermal or chemical stress. Especially, when PDAs contact with solutions of a particular pH, such as a strong alkaline sodium hydroxide (NaOH) solution or a strong acidic hydrogen chloride (HCl) solution, PDAs change their color from non-fluorescent blue to fluorescent red. In this study, we propose a novel method to detect alkaline pH using PDAs and NaOH solutions by hydrodynamic focusing on a microfluidic chip. Preliminary results indicate that the fluorescent intensity of PDAs increases in respond to the NaOH solution concentrations. Also, the fluorescence is quenched back when the PDAs are in contact with a HCl solution. These results are useful in a microfluidic PDA sensor chip design for pH detection.

• Korean Chemical Engineering Research
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• v.49 no.3
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• pp.348-351
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• 2011

In this research, we developed a sensor system which can easily detect several chelating agents using polydiacetylene(PDA) vesicles. In comparison to other sensors, PDA based sensor has several advantages. First, detection method is much simpler and faster because it does not require any labeling step in the experiment procedure. Second, significant color-transition from blue to red based upon external stimulus allows us the detection by naked eyes. Finally, it is also possible to perform quantitative analysis of the concentration of the chelating agent by measuring the colorimetric response. In this paper, five types of chelating agents were used, including EDTA, EGTA, NTA, DCTA and DTPA. Among them, EDTA and DCTA triggered especially strong color-transition. In conclusion, this study has led to a successful development of a color transition-based PDA sensor system for easy and rapid detection of chelating agents.

• Polymer Science and Technology
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• v.18 no.4
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• pp.326-330
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• 2007

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2692-2695
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• 2008

Polydiacetylene (PDA) is chemosensor materials that exhibit non-fluorescent-to-fluorescent transition as well as blue-to-red visible color change upon chemical or thermal stress. They have been studied in forms of film or microarray chip, so far. In this paper, we provide a novel technique to fabricate continuous micro-fiber PDA sensor using in-situ laser-polymerization technique and 3-D hydrodynamic focusing on a microfluidic chip. The flow of a monomer solution with diacetylene (DA) monomer is focused by a sheath flow on a 3-D microfluidic chip. The focused flow is exposed to 365 nm UV laser beam for in-situ polymerization which generates a continuous fiber containing DA monomers. Then, the fiber is exposed to 254 nm UV light to polymerize DA monomers to PDA. Preliminary results indicate that the fiber size can be controlled by the flow rates of the monomer solution and sheath flows and that a PDA sensor fiber successively responds to chemical and thermal stress.