{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,28]],"date-time":"2026-03-28T09:43:44Z","timestamp":1774691024386,"version":"3.50.1"},"reference-count":58,"publisher":"MDPI AG","issue":"8","license":[{"start":{"date-parts":[[2015,8,14]],"date-time":"2015-08-14T00:00:00Z","timestamp":1439510400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Canadian Breast Cancer Foundation"},{"DOI":"10.13039\/501100000038","name":"Natural Sciences and Engineering Research Council of Canada","doi-asserted-by":"publisher","id":[{"id":"10.13039\/501100000038","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100000024","name":"Canadian Institutes of Health Research","doi-asserted-by":"publisher","id":[{"id":"10.13039\/501100000024","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Control of oxygen over cell cultures in vitro is a topic of considerable interest, as chronic and cyclic hypoxia can alter cell behaviour. Both static and transient hypoxic levels have been found to affect tumour cell behaviour; it is potentially valuable to include these effects in early, in vitro stages of drug screening. A barrier to their inclusion is that rates of transient hypoxia can be a few cycles\/hour, which is difficult to reproduce in traditional in vitro cell culture environments due to long diffusion distances from control gases to the cells. We use a gas-permeable three-layer microfluidic device to achieve spatial and temporal oxygen control with biologically-relevant switching times. We measure the oxygen profiles with integrated, ratiometric optical oxygen sensors, demonstrate sensor and system stability over multi-day experiments, and characterize a pre-bleaching process to improve sensor stability. We show, with both finite-element modelling and experimental data, excellent control over the oxygen levels by the device, independent of fluid flow rate and oxygenation for the operating flow regime. We measure equilibration times of approximately 10 min, generate complex, time-varying oxygen profiles, and study the effects of oxygenated media flow rates on the measured oxygen levels. This device could form a useful tool for future long-term studies of cell behaviour under hypoxia.<\/jats:p>","DOI":"10.3390\/s150820030","type":"journal-article","created":{"date-parts":[[2015,8,18]],"date-time":"2015-08-18T02:36:16Z","timestamp":1439865376000},"page":"20030-20052","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":37,"title":["Designing a Microfluidic Device with Integrated Ratiometric Oxygen Sensors for the Long-Term Control and Monitoring of Chronic and Cyclic Hypoxia"],"prefix":"10.3390","volume":"15","author":[{"given":"Samantha","family":"Grist","sequence":"first","affiliation":[{"name":"Department of Electrical and Computer Engineering, The University of British Columbia,  2332 Main Mall, Vancouver V6T 1Z4, BC, Canada"}]},{"given":"Jonathan","family":"Schmok","sequence":"additional","affiliation":[{"name":"Department of Electrical and Computer Engineering, The University of British Columbia,  2332 Main Mall, Vancouver V6T 1Z4, BC, Canada"}]},{"given":"Meng-Chi","family":"Liu","sequence":"additional","affiliation":[{"name":"Department of Electrical and Computer Engineering, The University of British Columbia,  2332 Main Mall, Vancouver V6T 1Z4, BC, Canada"}]},{"given":"Lukas","family":"Chrostowski","sequence":"additional","affiliation":[{"name":"Department of Electrical and Computer Engineering, The University of British Columbia,  2332 Main Mall, Vancouver V6T 1Z4, BC, Canada"}]},{"given":"Karen","family":"Cheung","sequence":"additional","affiliation":[{"name":"Department of Electrical and Computer Engineering, The University of British Columbia,  2332 Main Mall, Vancouver V6T 1Z4, BC, Canada"}]}],"member":"1968","published-online":{"date-parts":[[2015,8,14]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"810","DOI":"10.1016\/j.drudis.2012.03.004","article-title":"Microtissue size and hypoxia in HTS with 3D cultures","volume":"17","author":"Asthana","year":"2012","journal-title":"Drug Discov. Today"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"381","DOI":"10.2174\/156800909788166637","article-title":"Hypoxia helps glioma to fight therapy","volume":"9","year":"2009","journal-title":"Curr. Cancer Drug Targets"},{"key":"ref_3","doi-asserted-by":"crossref","unstructured":"Favaro, E., Lord, S., Harris, A.L., and Buffa, F.M. (2011). Gene expression and hypoxia in breast cancer. Genome Med., 3.","DOI":"10.1186\/gm271"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"285","DOI":"10.1016\/S0360-3016(97)00101-6","article-title":"Tumor hypoxia adversely affects the prognosis of carcinoma of the head and neck","volume":"38","author":"Brizel","year":"1997","journal-title":"Int. J. Radiat. Oncol. Biol. Phys."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"8177","DOI":"10.1158\/1078-0432.CCR-04-1081","article-title":"Hypoxia is important in the biology and aggression of human glial brain tumors","volume":"10","author":"Evans","year":"2004","journal-title":"Clin. Cancer Res."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"21","DOI":"10.1634\/theoncologist.13-S3-21","article-title":"Hypoxia and aggressive tumor phenotype: Implications for therapy and prognosis","volume":"13","author":"Vaupel","year":"2008","journal-title":"Oncologist"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"55","DOI":"10.3233\/BD-2007-26105","article-title":"Hypoxia and metastasis in breast cancer","volume":"26","author":"Chaudary","year":"2007","journal-title":"Breast Dis."},{"key":"ref_8","unstructured":"Pettersen, E.O., Ebbesen, P., Gieling, R.G., Williams, K.J., Dubois, L., Lambin, P., Ward, C., Meehan, J., Kunkler, I.H., and Langdon, S.P. (2014). Targeting tumour hypoxia to prevent cancer metastasis. From biology, biosensing and technology to drug development: The metoxia consortium. J. Enzyme Inhib. Med. Chem., 1\u201333."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"423","DOI":"10.1158\/1541-7786.MCR-06-0150","article-title":"\u201cTranslating\u201d tumor hypoxia: Unfolded protein response (UPR)-Dependent and UPR-independent pathways","volume":"4","author":"Koumenis","year":"2006","journal-title":"Mol. Cancer Res."},{"key":"ref_10","doi-asserted-by":"crossref","unstructured":"Nagelkerke, A., Bussink, J., Mujcic, H., Wouters, B., Lehmann, S., Sweep, F., and Span, P. (2013). Hypoxia stimulates migration of breast cancer cells via the perk\/atf4\/lamp3-arm of the unfolded protein response. Breast Cancer Res., 15.","DOI":"10.1186\/bcr3373"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"503","DOI":"10.1182\/blood.V89.2.503","article-title":"Induction of hypoxia-inducible factor-1, erythropoietin, vascular endothelial growth factor, and glucose transporter-1 by hypoxia: Evidence against a regulatory role for src kinase","volume":"89","author":"Gleadle","year":"1997","journal-title":"Blood"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"2570","DOI":"10.1128\/MCB.00166-09","article-title":"Hypoxia-induced autophagy is mediated through hypoxia-inducible factor induction of BNIP3 and BNIP3L via their BH3 domains","volume":"29","author":"Bellot","year":"2009","journal-title":"Mol. Cell. Biol."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"285","DOI":"10.1038\/nrm2354","article-title":"The role of oxygen availability in embryonic development and stem cell function","volume":"9","author":"Simon","year":"2008","journal-title":"Nat. Rev. Mol. Cell. Biol."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"694","DOI":"10.1097\/MOT.0b013e3283329d53","article-title":"The effects of low oxygen on self-renewal and differentiation of embryonic stem cells","volume":"14","author":"Millman","year":"2009","journal-title":"Curr. Opin. Organ. Transplant."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"177","DOI":"10.1038\/nm0297-177","article-title":"Interstitial ph and po(2) gradients in solid tumors in vivo: High-resolution measurements reveal a lack of correlation","volume":"3","author":"Helmlinger","year":"1997","journal-title":"Nat. Med."},{"key":"ref_16","first-page":"4705","article-title":"Effect of longitudinal oxygen gradients on effectiveness of manipulation of tumor oxygenation","volume":"63","author":"Erickson","year":"2003","journal-title":"Cancer Res."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"237","DOI":"10.1023\/A:1022939318102","article-title":"The hypoxic tumour microenvironment and metastatic progression","volume":"20","author":"Subarsky","year":"2003","journal-title":"Clin. Exp. Metastasis"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"88","DOI":"10.1038\/379088a0","article-title":"Hypoxia-mediated selection of cells with diminished apoptotic potential in solid tumours","volume":"379","author":"Graeber","year":"1996","journal-title":"Nature"},{"key":"ref_19","doi-asserted-by":"crossref","unstructured":"Verduzco, D., Lloyd, M., Xu, L., Ibrahim-Hashim, A., Balagurunathan, Y., Gatenby, R.A., and Gillies, R.J. (2015). Intermittent hypoxia selects for genotypes and phenotypes that increase survival, invasion, and therapy resistance. PLoS ONE, 10.","DOI":"10.1371\/journal.pone.0120958"},{"key":"ref_20","first-page":"597","article-title":"Intermittent blood flow in a murine tumor: Radiobiological effects","volume":"47","author":"Chaplin","year":"1987","journal-title":"Cancer Res."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"5812","DOI":"10.1158\/0008-5472.CAN-07-6387","article-title":"The pervasive presence of fluctuating oxygenation in tumors","volume":"68","author":"Mace","year":"2008","journal-title":"Cancer Res."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"367","DOI":"10.1007\/978-1-4613-0333-6_48","article-title":"Detection of microregional fluctuations in erythrocyte flow using laser doppler microprobes","volume":"Volume 388","author":"Ince","year":"1996","journal-title":"Oxygen Transport to Tissue XVII"},{"key":"ref_23","first-page":"8903","article-title":"Acute (cyclic) hypoxia enhances spontaneous metastasis of kht murine tumors","volume":"61","author":"Cairns","year":"2001","journal-title":"Cancer Res."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"10019","DOI":"10.1158\/0008-5472.CAN-10-2821","article-title":"Imaging cycling tumor hypoxia","volume":"70","author":"Matsumoto","year":"2010","journal-title":"Cancer Res."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"388","DOI":"10.1039\/B920401F","article-title":"Generation of oxygen gradients with arbitrary shapes in a microfluidic device","volume":"10","author":"Groisman","year":"2010","journal-title":"Lab Chip"},{"key":"ref_26","doi-asserted-by":"crossref","unstructured":"Lam, R.H.W., Kim, M.-C., and Thorsen, T. (2007, January 10\u201314). A microfluidic oxygenator for biological cell culture. Proceedings of the International Solid-State Sensors, Actuators and Microsystems Conference, Lyon, France.","DOI":"10.1109\/SENSOR.2007.4300676"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"5918","DOI":"10.1021\/ac9006864","article-title":"Culturing aerobic and anaerobic bacteria and mammalian cells with a microfluidic differential oxygenator","volume":"81","author":"Lam","year":"2009","journal-title":"Anal. Chem."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"8821","DOI":"10.1021\/ac202300g","article-title":"Regulating oxygen levels in a microfluidic device","volume":"83","author":"Thomas","year":"2011","journal-title":"Anal. Chem."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"4041","DOI":"10.1039\/c1lc20505f","article-title":"On-chip CO2 control for microfluidic cell culture","volume":"11","author":"Forry","year":"2011","journal-title":"Lab Chip"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"3626","DOI":"10.1039\/c1lc20325h","article-title":"Generation of oxygen gradients in microfluidic devices for cell culture using spatially confined chemical reactions","volume":"11","author":"Chen","year":"2011","journal-title":"Lab Chip"},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"695","DOI":"10.1039\/C2LC40661F","article-title":"Construction of oxygen and chemical concentration gradients in a single microfluidic device for studying tumor cell-drug interactions in a dynamic hypoxia microenvironment","volume":"13","author":"Wang","year":"2013","journal-title":"Lab Chip"},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"4305","DOI":"10.1039\/C4LC00853G","article-title":"Oxygen control with microfluidics","volume":"14","author":"Brennan","year":"2014","journal-title":"Lab Chip"},{"key":"ref_33","doi-asserted-by":"crossref","unstructured":"Wood, D.K., Soriano, A., Mahadevan, L., Higgins, J.M., and Bhatia, S.N. (2012). A biophysical indicator of vaso-occlusive risk in sickle cell disease. Sci. Transl. Med., 4.","DOI":"10.1126\/scitranslmed.3002738"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"9286","DOI":"10.3390\/s101009286","article-title":"Optical oxygen sensors for applications in microfluidic cell culture","volume":"10","author":"Grist","year":"2010","journal-title":"Sensors"},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"115","DOI":"10.1595\/003214097X413115127","article-title":"Optical oxygen sensors","volume":"41","author":"Mills","year":"1997","journal-title":"Platin. Metals Rev."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"506","DOI":"10.1016\/S0925-4005(97)80120-7","article-title":"Miniaturized luminescence lifetime-based oxygen sensor instrumentation utilizing a phase modulation technique","volume":"36","author":"Trettnak","year":"1996","journal-title":"Sens. Actuators B Chem."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"548","DOI":"10.1366\/0003702001949726","article-title":"Luminescence lifetime imaging of oxygen, pH, and carbon dioxide distribution using optical sensors","volume":"54","author":"Liebsch","year":"2000","journal-title":"Appl. Spectrosc."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"4124","DOI":"10.1021\/ac0102718","article-title":"A real-time ratiometric method for the determination of molecular oxygen inside living cells using sol-gel-based spherical optical nanosensors with applications to rat c6 glioma","volume":"73","author":"Xu","year":"2001","journal-title":"Anal. Chem."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"472","DOI":"10.1016\/j.snb.2008.09.039","article-title":"Ratiometric porphyrin-based layers and nanoparticles for measuring oxygen in biosamples","volume":"135","author":"Cywinski","year":"2009","journal-title":"Sens. Actuators B Chem."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"6541","DOI":"10.1021\/ac900662x","article-title":"Light harvesting as a simple and versatile way to enhance brightness of luminescent sensors","volume":"81","author":"Mayr","year":"2009","journal-title":"Anal. Chem."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"456","DOI":"10.1016\/j.proeng.2010.09.145","article-title":"Oxygen imaging in microfluidic devices with optical sensors applying color cameras","volume":"5","author":"Ungerbock","year":"2010","journal-title":"Procedia Eng."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"1593","DOI":"10.1039\/c3lc41315b","article-title":"Microfluidic oxygen imaging using integrated optical sensor layers and a color camera","volume":"13","author":"Ungerbock","year":"2013","journal-title":"Lab Chip"},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"4924","DOI":"10.1039\/C4AN00783B","article-title":"Low cost referenced luminescent imaging of oxygen and pH with a 2-CCD colour near infrared camera","volume":"139","author":"Ehgartner","year":"2014","journal-title":"Analyst"},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"1073","DOI":"10.1039\/b816191g","article-title":"Fine temporal control of the medium gas content and acidity and on-chip generation of series of oxygen concentrations for cell cultures","volume":"9","author":"Groisman","year":"2009","journal-title":"Lab Chip"},{"key":"ref_45","doi-asserted-by":"crossref","unstructured":"Oppegard, S.C., Nam, K.H., Carr, J.R., Skaalure, S.C., and Eddington, D.T. (2009). Modulating temporal and spatial oxygenation over adherent cellular cultures. PLoS ONE, 4.","DOI":"10.1371\/journal.pone.0006891"},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"2366","DOI":"10.1039\/c004856a","article-title":"Precise control over the oxygen conditions within the boyden chamber using a microfabricated insert","volume":"10","author":"Oppegard","year":"2010","journal-title":"Lab Chip"},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"1987","DOI":"10.1021\/ac2030909","article-title":"Islet preconditioning via multimodal microfluidic modulation of intermittent hypoxia","volume":"84","author":"Lo","year":"2012","journal-title":"Anal. Chem."},{"key":"ref_48","doi-asserted-by":"crossref","unstructured":"Mauleon, G., Fall, C.P., and Eddington, D.T. (2012). Precise spatial and temporal control of oxygen within in vitro brain slices via microfluidic gas channels. PLoS ONE, 7.","DOI":"10.1371\/journal.pone.0043309"},{"key":"ref_49","first-page":"153","article-title":"Reversible alteration of calcium dynamics in cardiomyocytes during acute hypoxia transient in a microfluidic platform","volume":"4","author":"Martewicz","year":"2012","journal-title":"Integr. Biol. Quant. Biosci. Nano Macro"},{"key":"ref_50","doi-asserted-by":"crossref","unstructured":"Yu, L., Ni, C., Grist, S.M., Bayly, C., and Cheung, K.C. (2015). Alginate core-shell beads for simplified three-dimensional tumor spheroid culture and drug screening. Biomed. Microdevices, 17.","DOI":"10.1007\/s10544-014-9918-5"},{"key":"ref_51","doi-asserted-by":"crossref","unstructured":"Yu, L., Grist, S.M., Nasseri, S.S., Cheng, E., Hwang, Y.C.E., Ni, C., and Cheung, K.C. (2015). Core-shell hydrogel beads with extracellular matrix for tumor spheroid formation. Biomicrofluidics, 9.","DOI":"10.1063\/1.4918754"},{"key":"ref_52","unstructured":"Grist, S.M., Cheng, E., Yu, L.F., and Cheung, K.C. (2014, January 26\u201330). Modulated two-photon imaging of whole spheroids for three-dimensional cell cultures. Proceedings of the 18th International Conference on Miniaturized Systems for Chemistry and Life Sciences, San Antonio, TX, USA."},{"key":"ref_53","doi-asserted-by":"crossref","first-page":"5718","DOI":"10.1039\/C4AN00765D","article-title":"Fabrication and laser patterning of polystyrene optical oxygen sensor films for lab-on-a-chip applications","volume":"139","author":"Grist","year":"2014","journal-title":"Analyst"},{"key":"ref_54","doi-asserted-by":"crossref","first-page":"285","DOI":"10.1007\/s10404-013-1142-8","article-title":"Mathematical analysis of oxygen transfer through polydimethylsiloxane membrane between double layers of cell culture channel and gas chamber in microfluidic oxygenator","volume":"15","author":"Kim","year":"2013","journal-title":"Microfluid. Nanofluid."},{"key":"ref_55","first-page":"S49","article-title":"Limit of blank, limit of detection and limit of quantitation","volume":"29","author":"Armbruster","year":"2008","journal-title":"Clin. Biochem. Rev."},{"key":"ref_56","doi-asserted-by":"crossref","first-page":"173","DOI":"10.1016\/j.snb.2012.04.062","article-title":"Stable optical oxygen sensing materials based on click-coupling of fluorinated platinum(ii) and palladium(ii) porphyrins-a convenient way to eliminate dye migration and leaching","volume":"169","author":"Koren","year":"2012","journal-title":"Sens. Actuators B Chem."},{"key":"ref_57","doi-asserted-by":"crossref","first-page":"711","DOI":"10.1016\/j.snb.2008.06.022","article-title":"Ratiometric fiber-optic oxygen sensors based on sol-gel matrix doped with metalloporphyrin and 7-amino-4-trifluoromethyl coumarin","volume":"134","author":"Chu","year":"2008","journal-title":"Sens. Actuators B Chem."},{"key":"ref_58","doi-asserted-by":"crossref","unstructured":"Lehner, P., Staudinger, C., Borisov, S.M., and Klimant, I. (2014). Ultra-sensitive optical oxygen sensors for characterization of nearly anoxic systems. Nat. Commun., 5.","DOI":"10.1038\/ncomms5460"}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/15\/8\/20030\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T20:50:42Z","timestamp":1760215842000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/15\/8\/20030"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2015,8,14]]},"references-count":58,"journal-issue":{"issue":"8","published-online":{"date-parts":[[2015,8]]}},"alternative-id":["s150820030"],"URL":"https:\/\/doi.org\/10.3390\/s150820030","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2015,8,14]]}}}