Raman spectroscopy compatible PDMS droplet microfluidic culture and analysis platform towards on-chip lipidomics.

Lipids produced by microalgae are viewed as a potential renewable alternative to fossil fuels, however, significant improvements in productivity are required for microalgal biofuels to become economically feasible. Here we present a method that allows for the use of Raman spectroscopy with poly(dimethylsiloxane) (PDMS) droplet microfluidic devices, which not only overcomes the high Raman background of PDMS, but also achieves pairing of the high-throughput single-cell resolution advantages of droplet microfluidics with the direct, chemically specific, label-free, and non-destructive nature of Raman spectroscopy. The platform was successfully utilized for in situ characterization of microalgal lipid production over time within droplets, paving the way towards high-throughput microalgal lipidomics assays.

[1]  K. Jefimovs,et al.  Analysis of single algal cells by combining mass spectrometry with Raman and fluorescence mapping. , 2013, The Analyst.

[2]  D Hümmer,et al.  Single cells in confined volumes: microchambers and microdroplets. , 2016, Lab on a chip.

[3]  Kishan Dholakia,et al.  Waveguide confined Raman spectroscopy for microfluidic interrogation. , 2011, Lab on a chip.

[4]  Arum Han,et al.  A high-throughput microfluidic single-cell screening platform capable of selective cell extraction. , 2015, Lab on a chip.

[5]  Jihye Kim,et al.  Growth kinetics of microalgae in microfluidic static droplet arrays , 2012, Biotechnology and bioengineering.

[6]  Huabing Yin,et al.  Raman-activated cell sorting based on dielectrophoretic single-cell trap and release. , 2015, Analytical chemistry.

[7]  Jean-Paul Cadoret,et al.  The use of fluorescent Nile red and BODIPY for lipid measurement in microalgae , 2015, Biotechnology for Biofuels.

[8]  S. Liaaen-Jensen,et al.  Primary and secondary carotenoids in two races of the green alga Botryococcus braunii , 1989 .

[9]  Hyun Soo Kim,et al.  Microfabricated devices in microbial bioenergy sciences. , 2013, Trends in biotechnology.

[10]  H. Martinho,et al.  Rapid and noninvasive technique to assess the metabolomics profile of bovine embryos produced in vitro by Raman spectroscopy. , 2015, Biomedical optics express.

[11]  W. Huck,et al.  One drop at a time: toward droplet microfluidics as a versatile tool for single-cell analysis , 2014 .

[12]  R. Levine,et al.  Cytochrome f and plastocyanin: their sequence in the photosynthetic electron transport chain of Chlamydomonas reinhardi. , 1965, Proceedings of the National Academy of Sciences of the United States of America.

[13]  T. Baldacchini,et al.  Coherent anti-Stokes Raman scattering and spontaneous Raman spectroscopy and microscopy of microalgae with nitrogen depletion , 2012, Biomedical optics express.

[14]  S. Mayfield,et al.  Exploiting diversity and synthetic biology for the production of algal biofuels , 2012, Nature.

[15]  Patrik R. Callis,et al.  Fluorometric determination of the neutral lipid content of microalgal cells using Nile Red , 1987 .

[16]  Q. Hu,et al.  Microalgal triacylglycerols as feedstocks for biofuel production: perspectives and advances. , 2008, The Plant journal : for cell and molecular biology.

[17]  Kamila Kochan,et al.  Raman spectroscopy of lipids: a review , 2015 .

[18]  Yusuf Chisti,et al.  Constraints to commercialization of algal fuels. , 2013, Journal of biotechnology.

[19]  Cornelis Otto,et al.  A microfluidic chip for high resolution Raman imaging of biological cells , 2015 .

[20]  D. Weitz,et al.  Single-cell analysis and sorting using droplet-based microfluidics , 2013, Nature Protocols.

[21]  Dongyuan Zhang,et al.  Increased lipid productivity and TAG content in Nannochloropsis by heavy-ion irradiation mutagenesis. , 2013, Bioresource technology.

[22]  L. Rodolfi,et al.  Microalgae for oil: Strain selection, induction of lipid synthesis and outdoor mass cultivation in a low‐cost photobioreactor , 2009, Biotechnology and bioengineering.

[23]  T. Merkel,et al.  Gas sorption, diffusion, and permeation in poly(dimethylsiloxane) , 2000 .

[24]  E. Amis,et al.  Raman spectroscopic monitoring of droplet polymerization in a microfluidic device. , 2006, The Analyst.

[25]  Arum Han,et al.  A droplet microfluidics platform for rapid microalgal growth and oil production analysis , 2016, Biotechnology and bioengineering.

[26]  Robert J. Horvat,et al.  Raman spectroscopic analysis of thecis/trans isomer composition of edible vegetable oils , 1972 .

[27]  D. Talaga,et al.  Chemical reaction imaging within microfluidic devices using confocal raman spectroscopy: the case of water and deuterium oxide as a model system. , 2008, Analytical chemistry.

[28]  Hye Jin Chun,et al.  Raman Spectroscopy Analysis of Botryococcene Hydrocarbons from the Green Microalga Botryococcus braunii* , 2010, The Journal of Biological Chemistry.

[29]  Hyun Soo Kim,et al.  A microfluidic photobioreactor array demonstrating high-throughput screening for microalgal oil production. , 2014, Lab on a chip.

[30]  B. Milman.  Identification of chemical compounds , 2005 .

[31]  Arum Han,et al.  A three-dimensional electrode for highly efficient electrocoalescence-based droplet merging , 2015, Biomedical microdevices.

[32]  S. Sim,et al.  Microdroplet photobioreactor for the photoautotrophic culture of microalgal cells. , 2016, The Analyst.

[33]  Pavel Zemánek,et al.  Characterization of oil-producing microalgae using Raman spectroscopy , 2011 .

[34]  James P Freyer,et al.  Comparison of vibrational spectroscopy to biochemical and flow cytometry methods for analysis of the basic biochemical composition of mammalian cells. , 2006, Journal of biomedical optics.

[35]  Seema Singh,et al.  In vivo lipidomics using single-cell Raman spectroscopy , 2011, Proceedings of the National Academy of Sciences.

[36]  Hiro-o Hamaguchi,et al.  Quantitative coherent anti-Stokes Raman scattering (CARS) microscopy. , 2011, The journal of physical chemistry. B.

[37]  Pavel Zemánek,et al.  Raman Microspectroscopy of Individual Algal Cells: Sensing Unsaturation of Storage Lipids in vivo , 2010, Sensors.

[38]  Jürgen Popp,et al.  Droplet formation via flow-through microdevices in Raman and surface enhanced Raman spectroscopy--concepts and applications. , 2011, Lab on a chip.

[39]  J. Walter,et al.  Liquid seaweed extracts identified using 1H NMR profiles , 2008, Journal of Applied Phycology.

[40]  G. Charles Dismukes,et al.  Increased Lipid Accumulation in the Chlamydomonas reinhardtiista7-10 Starchless Isoamylase Mutant and Increased Carbohydrate Synthesis in Complemented Strains , 2010, Eukaryotic Cell.