title: Single nucleotide polymorphism detection using gold nanoprobes and bio-microfluidic platform with embedded microlenses.
abstract: The use of microfluidics platforms combined with the optimal optical properties of gold nanoparticles has found plenty of application in molecular biosensing. This paper describes a bio-microfluidic platform coupled to a non-cross-linking colorimetric gold nanoprobe assay to detect a single nucleotide polymorphism associated with increased risk of obesity fat-mass and obesity-associated (FTO) rs9939609 (Carlos et al., 2014). The system enabled significant discrimination between positive and negative assays using a target DNA concentration of 5 ng/µL below the limit of detection of the conventionally used microplate reader (i.e., 15 ng/µL) with 10 times lower solution volume (i.e., 3 µL). A set of optimization of our previously reported bio-microfluidic platform (Bernacka-Wojcik et al., 2013) resulted in a 160% improvement of colorimetric analysis results. Incorporation of planar microlenses increased 6 times signal-to-loss ratio reaching the output optical fiber improving by 34% the colorimetric analysis of gold nanoparticles, while the implementation of an optoelectronic acquisition system yielded increased accuracy and reduced noise. The microfluidic chip was also integrated with a miniature fiber spectrometer to analyze the assays' colorimetric changes and also the LEDs transmission spectra when illuminating through various solutions. Furthermore, by coupling an optical microscope to a digital camera with a long exposure time (30 s), we could visualise the different scatter intensities of gold nanoparticles within channels following salt addition. These intensities correlate well to the expected difference in aggregation between FTO positive (none to small aggregates) and negative samples (large aggregates).
authors.affiliation: Departamento de Ciência dos Materiais, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Campus de Caparica, CENIMAT/I3N, Caparica, 2829-516, Portugal. ib@uninova.pt.
authors.forename: Iwona
authors.initials: I
authors.lastname: Bernacka-Wojcik
authors.forename: Hugo
authors.initials: H
authors.lastname: Águas
authors.forename: Fabio Ferreira
authors.initials: FF
authors.lastname: Carlos
authors.forename: Paulo
authors.initials: P
authors.lastname: Lopes
authors.forename: Pawel Jerzy
authors.initials: PJ
authors.lastname: Wojcik
authors.forename: Mafalda Nascimento
authors.initials: MN
authors.lastname: Costa
authors.forename: Bruno
authors.initials: B
authors.lastname: Veigas
authors.forename: Rui
authors.initials: R
authors.lastname: Igreja
authors.forename: Elvira
authors.initials: E
authors.lastname: Fortunato
authors.forename: Pedro Viana
authors.initials: PV
authors.lastname: Baptista
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Martins
mesh_terms: D015374:Biosensing Techniques / Q000379:methods*; D003124:Colorimetry / Q000379:methods; D015342:DNA Probes; D020022:Genetic Predisposition to Disease; D006046:Gold; D006801:Humans; D044085:Microfluidics / Q000379:methods*; D036103:Nanotechnology / Q000379:methods*; D009765:Obesity / Q000235:genetics; D061848:Optical Imaging / Q000379:methods; D020641:Polymorphism, Single Nucleotide; D013057:Spectrum Analysis / Q000379:methods
chemical_list: D015342:DNA Probes; D006046:Gold
keywords: DNA; fiber-optics; gold nanoparticles; microfluidics; single nucleotide polymorphism