title: A multiple path photonic lab on a chip for parallel protein concentration measurements.
abstract: We propose a PDMS-based photonic system for the accurate measurement of protein concentration with minute amounts of the sample. As opposed to the state of the art approach, in the multiple path photonic lab on a chip (MPHIL), analyte concentration or molar absorptivity is obtained with a single injection step, by performing simultaneous parallel optical measurements varying the optical path length. Also, as opposed to the standard calibration protocol, the MPHIL approach does not require a series of measurements at different concentrations. MPHIL has three main advantages: firstly the possibility of dynamically selecting the path length, always working in the absorbance vs. concentration linear range for each target analyte. Secondly, a dramatic reduction of the total volume of the sample required to obtain statistically reliable results. Thirdly, since only one injection is required, the measurement time is minimized, reducing both contamination and signal drifts. These characteristics are clearly advantageous when compared to commercial micro-spectrophotometers. The MPHIL concept was validated by testing three commercial proteins, lysozyme (HEWL), glucose isomerase (d-xylose-ketol-isomerase, GI) and Aspergillus sp. lipase L (BLL), as well as two proteins expressed and purified for this study, B. cereus formamidase (FASE) and dihydropyrimidinase from S. meliloti CECT41 (DHP). The use of MPHIL is also proposed for any spectrophotometric measurement in the UV-VIS range, as well as for its integration as a concentration measurement platform in more advanced photonic lab on a chip systems.
authors.affiliation: Institut de Microelectrònica de Barcelona (IMB-CNM, CSIC), Campus UAB, 08193 Bellaterra, Spain. isaac.rodriguez@imb-cnm.csic.es.
authors.forename: Isaac
authors.initials: I
authors.lastname: Rodríguez-Ruiz
authors.forename: Mayte
authors.initials: M
authors.lastname: Conejero-Muriel
authors.forename: Tobias N
authors.initials: TN
authors.lastname: Ackermann
authors.forename: José A
authors.initials: JA
authors.lastname: Gavira
authors.forename: Andreu
authors.initials: A
authors.lastname: Llobera
mesh_terms: D019747:Aldose-Ketose Isomerases / Q000032:analysis* / Q000378:metabolism; D000581:Amidohydrolases / Q000032:analysis* / Q000378:metabolism; D001230:Aspergillus / Q000201:enzymology; D001409:Bacillus cereus / Q000201:enzymology; D004129:Dimethylpolysiloxanes / Q000737:chemistry; D056656:Lab-On-A-Chip Devices; D008049:Lipase / Q000032:analysis* / Q000378:metabolism; D009113:Muramidase / Q000032:analysis* / Q000378:metabolism; D017785:Photons; D016962:Sinorhizobium meliloti / Q000201:enzymology
chemical_list: D004129:Dimethylpolysiloxanes; C013830:baysilon; D008049:Lipase; D009113:Muramidase; D000581:Amidohydrolases; C101846:formamidase; C020047:dihydropyrimidinase; D019747:Aldose-Ketose Isomerases; C023298:xylose isomerase