Technical Note pubs.acs.org/ac
Microfluidic Pipette Tip for High-Purity and High-Throughput Blood Plasma Separation from Whole Blood Byeongyeon Kim, Sein Oh, Dongwon You, and Sungyoung Choi* Department of Biomedical Engineering, Kyung Hee University, Yongin-si, Gyeonggi-do 17104, Republic of Korea S Supporting Information *
ABSTRACT: Blood plasma separation from whole blood is often limited by numerous blood cells which can compromise separation processes and thus deteriorate separation performance such as purity and throughput. To address this challenge, we present a microfluidic pipet tip composed of slant array ridges that enable autonomous blood cell focusing without significant deviation as well as facilitating a high degree of parallelization without compromising separation purity. With these advantages, we achieved high-purity (99.88%) and high-throughput (904.3 μL min−1) plasma separation from whole blood. In combination with a smart pipet, we successfully demonstrated rapid, inexpensive, and equipment-free blood plasma preparation for pretransfusion testing.
B
fouling or a limited separation capacity for the removal of blood cells. Continuous-flow approaches direct blood cells from all directions into defined flow streams upon the application of external forces such as acoustic11 and electric forces12 or inherent hydrodynamic phenomena including sedimentation,13 deterministic lateral displacement,14 inertial microfluidics15 and the Zweifach-Fung effect.16 These methods obviate the risk of clogging and ensure the continuous removal of blood cells, but they typically require large-scale, expensive equipment for operation (i.e., high-precision syringe pumps or signal generators) that can limit their widespread use and accessibility for subsequent diagnostic tests. In an effort to develop a rapid, inexpensive, and on-site sample preparation method, we recently introduced a smart pipetting system that can create a constant pressure by pressurizing an air chamber with a plunger and can thus enable the accurate transfer of biological samples through a microfluidic pipet tip.17 The pipet tip, a microchannel composed of slant ridges, was designed to separate blood plasma from whole blood by directing blood cells toward a side wall of the microchannel. The combination of the smart pipet and the microfluidic pipet tip allows continuous plasma separation by simple and hand-powered operation of the smart pipet. However, the separation process can cause the deviation of a few red blood cells (RBCs) to a separated plasma stream, leading to a reduction in plasma quality. Here, we present a microfluidic pipet tip designed to produce high-purity blood plasma from whole blood in a highthroughput manner (Figure 1), which offers the following
lood plasma contains critical solutes such as proteins and other organic compounds necessary for sustaining health which are often molecular targets for clinical diagnosis.1 Analysis of protein biomarkers in blood plasma allows clinical diagnosis of various diseases such as cardiovascular diseases,2 various cancers,3 and Alzheimer’s disease.4 Screening of cellfree fetal DNA in maternal blood provides a noninvasive means for examination of fetal abnormalities.5 In addition, the plasma portion of a recipient needs to be tested for compatibility with the donated blood prior to transfusion.6 For such applications, plasma separation from whole blood is an important sample preparation step to prevent blood cells from interfering with subsequent diagnostic tests and thus to improve the quality and reliability of test results. The preparation process is routinely accomplished in a laboratory setting with a benchtop centrifuge, but the equipment is not portable and is expensive, thereby limiting its use in point-of-care settings. Recent advances in microfluidics technology have enabled the miniaturization and integration of sample preparative techniques into a single chip, leading to shorter test times, lower costs per test, and reduced sample consumption.7 These advantages make microfluidics technology ideal for inexpensive on-site diagnosis. Microfluidic techniques for plasma separation from whole blood have been proposed; they can be categorized as filtration approaches, which incorporate filtering geometries smaller than blood cells,8−10 and continuous-flow approaches, which utilize the natural or forced deviation of the cells freely flowing in microchannels.11−16 Incorporating the filtration geometries into microchannels enables the efficient rejection of blood cells by interposing the geometries through which only blood plasma can pass.8−10 However, there are some limitations to the use of the filtration approaches, including a risk of clogging and © XXXX American Chemical Society
Received: November 21, 2016 Accepted: December 28, 2016
A
DOI: 10.1021/acs.analchem.6b04587 Anal. Chem. XXXX, XXX, XXX−XXX
Technical Note
Analytical Chemistry
Figure 1. Device designs for blood plasma separation. (a) Schematics showing the channel design for blood plasma separation from whole blood: (left) continuous slant array (CSA) and (right) discrete slant array (DSA) ridges. The microposts between the DSA ridges enable complete focusing of RBCs without significant deviation. The solid and dotted lines represent the possible flow paths of RBCs. (b) Three different types of separation devices. Each separation stage is composed of CSA or DSA ridges and denoted with r1−r6. (c) Bright-field micrographs showing the CSA and DSA ridges. Scale bars, 100 μm.
curing agent of PDMS in a 10:1 weight ratio, pouring and baking the mixture onto the SU-8 molds, cutting the PDMS replicas into individual devices, punching to form inlet and outlet holes, and irreversible bonding between each PDMS device and a glass slide after exposure to oxygen plasma for 60 s. The channel height, h, of the devices was set to 12 μm to ensure the hydrophoretic focusing of RBCs as previously reported (Figure 1a).17 The ridge width, wr, for continuous slant array (CSA) ridges was set to 10 μm due to the dependence of the width of a cell-depleted stream on wr (Figure 1a). As wr was narrowed to 10 μm, a clear plasma stream where RBCs were depleted was generated.17 The wr for the DSA ridges was set to 15 μm, because in principle, the RBC deviation is minimized by forming the microposts between DSA ridges, not by narrowing wr, and it is difficult to fabricate narrow microposts. As a pneumatic device for hand-powered operation of the microfluidic devices, a smart pipet was fabricated by assembling a conventional 1 mL pipet tip (Corning, USA), a 3D-printed air chamber, and a 60 mL BD syringe (BD Biosciences, USA). Details of the fabrication of the smart pipet are provided in the Supporting Information. Sample Preparation. Canine blood samples were purchased from the Korea Animal Blood Bank, and human blood samples were obtained from the Korean Red Cross in compliance with safety regulations. Hematocrit (Hct) levels were measured as the ratio of the length of the packed RBCs to the length of the injected blood sample in a capillary tube after centrifugation. For the quantification of blood aggregation, blood samples were incubated with a nucleic-acid staining fluorescent dye, SYTO 13 (Thermo Fisher Scientific, USA), which can stain white blood cells trapped in blood aggregation,
novel features: (1) the microposts between discrete slant array (DSA) ridges prevent the deviation of RBCs to achieve highpurity plasma, (2) the simple microfluidic geometry with a single inlet enables a high degree of parallelization to allow high-throughput separation by processing 1 mL of whole blood in less than 70 s, and (3) the combination of the new microfluidic pipet tip with the smart pipet enables simple microfluidics implementation without requiring auxiliary equipment such as a centrifuge and syringe pump to be potentially useful in point-of-care settings. With these advantages, we demonstrate the utility of our separation platform to prepare recipient blood samples for cross-match tests as a pretransfusion test.
■
EXPERIMENTAL SECTION Device Design and Fabrication. Microfluidic devices were fabricated in polydimethylsiloxane (PDMS; Dow Corning, USA) by two-step photolithography and soft lithography. Master molds for PDMS replica molding were fabricated by repeating standard photolithography processes twice including spin-coating of SU-8 photoresist (Microchem, USA), UV exposure through a photomask (Microtech, Korea), photoresist development for removal of the unexposed photoresist areas, and baking for removal of the residual solvent and solidification of the resulting photoresist structures. The first and second photoresist layers were defined as the base channel structures and the ridge patterns, respectively. After silanization with trichloro(1H,1H,2H,2H-per-fluorooctyl)silane (Sigma-Aldrich, USA), microfluidic devices were fabricated in PDMS through PDMS replication processes including mixing of the base and B
DOI: 10.1021/acs.analchem.6b04587 Anal. Chem. XXXX, XXX, XXX−XXX
Technical Note
Analytical Chemistry thereby making the aggregation fluorescently visible.18 For the quantification of separation efficiencies, blood cells in loading and collected samples were manually counted using a hemocytometer (Invitrogen, USA) after dilution. Experimental Setup. A syringe pump (KD Scientific, USA) was used for device characterization over a range of flow rates (100 to 400 μL min−1); otherwise, the smart pipet was used for device operation. Flow trajectories of blood cells were observed using a charge-coupled device camera (Nikon, Japan) and a high-speed camera (Vision Research, USA) equipped with a fluorescence microscope (Nikon). The fluorescence intensities of the blood aggregation were analyzed using the image analysis software, ImageJ (National Institutes of Health, USA).
and each row is shifted horizontally relative to the previous row by Δδ, where Δδ is the row shift distance and is 9 μm and δ is the ridge length and is typically 160 μm (Figures 1a and S1). The horizontal shift of the DSA ridges for each row with respect to the previous row facilitates the deflection of RBCs along the shifting direction or the focusing path (see the right panels of Figure 1a). Figure S2 clearly shows distinct flow patterns inside the CSA and DSA ridges: a continuous flow pattern along the CSA ridge and a discontinuous, recirculating flow pattern inside the DSA ridge. The microposts between the DSA ridges completely block the flow of RBCs through themselves, thus terminating the deviation path within the short length of each DSA ridge. The discontinuity of the DSA ridges in each row enables effective RBC separation without RBC deviation across the entire channel width, thereby significantly improving plasma quality. To prove the separation principle and demonstrate its effectiveness for blood plasma separation, we fabricated three different types of microfluidic devices which have three serial separation stages (Figure 1b). The first separation stage is designed as a preseparation step to remove significant amounts of RBCs from blood plasma. A channel opposite to RBC outlet 1 leads to the second and third stages, where RBCs can be separated from blood plasma with higher efficiency, thereby improving plasma quality. Device types 1 and 2 are composed of CSA ridges and DSA ridges for the separation stages, respectively. The first stage of the type 3 device consists of CSA ridges, followed by DSA ridges in the second and third stages. We first examined whether the microposts arranged between DSA ridges can promote channel clogging by blood aggregation. We observed visible aggregation in the whole blood samples obtained from the Korean Animal Blood Bank. The aggregation can cause channel clogging and affect device performance by altering flow patterns. For the quantification of blood aggregation, the canine blood samples (Hct = 46%) incubated with a nucleic-acid staining fluorescent dye, SYTO 13, were injected into the type 1 and type 2 devices using a syringe pump at a flow rate (q) of 100 μL min−1. As shown in Figure 2, channel clogging occurred due to nonspecific adsorption of blood aggregation on the microposts in the type 2 device and became more severe over time, while no clogging was observed in the type 1 device (Figure 2). The microposts likely contributed to clogging by providing nonspecific adsorption sites for blood aggregation. The channel clogging can lead to irreproducible separation and device failure. Interestingly, CSA ridges focused blood aggregation toward the left sidewall of the channel without significant clogging and eliminated them, directing them to RBC outlet 1. We thus designed the type 3 device to utilize the blood aggregation-cleaning effect of CSA ridges as well as the improved separation performance of DSA ridges. As expected, there was no significant blood aggregation adsorbed on the microposts between the DSA ridges in the second separation stage of the type 3 device during device operation lasting over 5 min (Figure 2). These results indicate that the CSA ridges in the first separation stage can effectively remove blood aggregation and prevent clogging of the downstream channel. The type 1 and type 3 devices, which can obviate the issue of channel clogging, were selected for further performance evaluation. We then explored the capability of the devices to separate blood plasma from whole blood. We determined the separation purity (φ) or plasma quality for all experiments by calculating
■
RESULTS AND DISCUSSION We designed and fabricated three different microfluidic devices for blood plasma separation by adopting design features from previous works on hydrophoretic separation17,19,20 and deterministic migration21 and then determined a device design to be used as a microfluidic pipet tip through the following empirical studies. Since numerous RBCs (approximately 4 to 6 million cells per μL in whole blood) need to be removed from blood plasma and hydrodynamic interactions between RBCs can complicate the process of blood cell separation using previous ridge designs,17,19,20 we developed a new ridge design, DSA ridges for the high-purity and high-throughput separation of blood plasma (Figure 1). In comparison with previous ridge designs,17,19−21 a major advancement is to introduce microposts between slant ridges which are bound onto the bottom surface and completely segregate the ridge spaces, thereby enabling the following capabilities: generation of a focused RBC stream without the distinct spread and scattering of RBCs; maintenance of device integrity without significant PDMS bulging under pressure. These new capabilities can allow high-purity and high-throughput plasma separation from whole blood, which was not achievable with previous ridge designs. The microposts can effectively block the undesired transport of RBCs guided through the CSA ridges or neighboring slant ridges, thereby enabling highly focused RBC separation. In addition, the microposts can effectively prevent deformation of PDMS channels, thereby maintaining device integrity. Figure 1a shows a comparison of RBC separation between CSA and DSA ridges. Conventional CSA ridges generate transverse flows, which are mainly composed of two oppositely flowing currents. Inside the ridges, the flow direction is dictated by the ridge structure and is parallel to the deviation path, while under the ridge structure, the flow direction is reversed as indicated by the focusing path (see the left panels of Figure 1a). If a cell is large enough (d ≥ h/2, where d is the cell diameter), it can be displaced into the adjacent streamline under the present one via physical collision against the groove structure, which can force the cell to remain outside the ridges, where it is exposed to the focusing flow.17,19,20 This hydrodynamic phenomenon, known as hydrophoresis, ensures autonomous cell separation from blood plasma.17 Hydrodynamic interactions between numerous RBCs in whole blood, however, push them to the ridges and lead to undesired deviation along the deviation path, thereby impairing plasma quality. To maximize RBC separation with minimal deviation, we designed the DSA ridges as an array of slant ridges such that each ridge in a row is completely separated by a micropost (g = 30 μm) C
DOI: 10.1021/acs.analchem.6b04587 Anal. Chem. XXXX, XXX, XXX−XXX
Technical Note
Analytical Chemistry
Figure 2. Channel clogging by blood aggregation. (a) Fluorescence images showing adsorbed blood aggregation on the microposts between DSA ridges. Significant clogging occurred on the microposts in the type 2 device and became more severe over time. Scale bars, 200 μm. (b) Fluorescence intensity measurements with time show the continual increase only in the type 2 device composed solely of DSA ridges. The injection flow rate was 100 μL min−1. Figure 3. Characterization of the type 1 and type 3 devices. (a) Undesired deviation of RBCs from the focused RBC stream in the type 1 device. Complete focusing of RBCs to the left sidewall in the type 3 device. The flow direction is from top to bottom in each image. The injection flow rate was 100 μL min−1. Scale bars, 200 μm. (b) Comparison of the purity of blood plasma separated using the type 1 and type 3 devices. Effect of flow rate on the purity of blood plasma separated using the type 3 device (n = 3).
the number of cells rejected in a separated plasma sample divided by the number of cells injected. The plasma recovery (γ) was defined as the volume of plasma collected in the plasma outlet divided by the plasma volume of whole blood injected. Canine whole blood (Hct = 47%) was injected into the type 1 and type 3 devices using a syringe pump over a range of flow rates (100 to 400 μL min−1). As can be seen in Figure 3a as well as Videos S1 and S2, the microposts between DSA ridges could effectively prevent RBC deviation along the whole width of the channel, while the CSA ridges without the posts allowed the RBC deviation. At q = 100 μL min−1, the presence of the microposts resulted in a significant improvement in φ from 94.18 ± 1.95% (type 1) to 99.99 ± 0.01% (type 3) (Figure 3b). As q increased to 400 μL min−1 in the type 3 device, φ decreased gradually to 93.96 ± 3.98%, while γ remained unchanged over the range of q: γ = 15.59 ± 0.58%, 15.46 ± 0.73%, 14.31 ± 0.20%, and 15.17 ± 1.29% for q = 100, 200, 300, and 400 μL min−1, respectively (n = 3). The type 1 device was tested at a flow-rate condition (100 μL min−1) due to its low separation purity and its inability for blood plasma separation at higher flow rates as previously reported.17 The reduction in φ with increased q is likely due to increased inertial forces such as inertial lift and Dean drag forces and the elastic deformation of the PDMS device under high pressure which can destabilize the focusing process in the first separation stage.17 The deteriorated focusing process in the first stage resulted in an increase in the number of RBCs being passed on the second and third stages (Figure S3) and consequently affected φ. These results indicate that there is an optimal flow rate for the type 3 device to achieve high-purity blood plasma separation.
We next developed a parallelized device as a microfluidic pipet tip to achieve high-throughput blood plasma separation while maintaining high plasma quality (Figure 4). The device contains eight parallel separation channels of type 3, and a common reservoir for RBC outlets was assembled before plasma separation (Figure 4a). For its potential use in point-ofcare settings, the parallelized device was operated using the smart pipet, a pneumatic device used to generate a constant pressure for the hand-powered operation of microfluidic devices (Figure S4 and Video S3). The smart pipet works by creating a vacuum in a liquid-holding tip (1 mL pipet tip) and an air chamber by withdrawing the plunger to draw up blood, assembling the microfluidic pipet tip to the liquid-holding tip, and applying pressure by pushing the plunger to infuse blood into the microfluidic pipet tip at a certain pressure. After 1.5 mL of whole blood was drawn and the microfluidic pipet tip was assembled at the liquid-holding tip of the smart pipet, compressing the air chamber by depressing the plunger by 40 mL generated an average flow rate of 904.3 ± 15.6 μL min−1 (n = 3). These conditions yielded a high φ of 99.88 ± 0.01% at a plasma extraction rate of 51 ± 1 μL min−1 (n = 3). This throughput capability is considerably higher than other state of the art microfluidic separators, while maintaining high plasma quality (Table S1). The proposed platform is capable of enhancing plasma separation throughput by up to 0.9 mL D
DOI: 10.1021/acs.analchem.6b04587 Anal. Chem. XXXX, XXX, XXX−XXX
Technical Note
Analytical Chemistry
Figure 5. Clinical application of the microfluidic pipet tip to blood plasma preparation for pretransfusion testing. (a) A major crossmatching procedure. (b) Test results showing the compatibility between the donors’ RBCs and the recipient’s plasma prepared by the microfluidic pipet tip and the smart pipet. The bright-field images were taken using the microscope with a 2× objective lens.
tested different types of human blood by separating blood plasma from the blood of a recipient with blood type B through the combined use of the smart pipet and the microfluidic pipet tip and then mixing the resulting plasma with the RBCs of donor 1 with blood type A and the RBCs of donor 2 with blood type B (Figure 5b). For the tests, 20 μL of the separated plasma from the recipient’s blood was mixed with 1 μL of the donors’ cell suspensions in a PDMS well of 6 mm in diameter. After 20 min of incubation, we could clearly observe blood cell aggregation only in the case of incompatible blood types (donor 1 and recipient), supporting that the microfluidic pipet tip, together with the smart pipet, enables the hand-powered and rapid preparation of high-quality blood plasma without the need for large-scale, auxiliary instruments for clinical tests. The agglutination is a result of the antigen−antibody interaction between anti-A antibodies in the recipient’s plasma and A antigens on donor 1’s RBCs. The cross-match test can check for unexpected antibodies in a recipient’s blood and thus avoid potentially lethal hemolytic reactions. The presence of agglutination as a result of cross-match incompatibility can be detected by centrifuging the blood mixture through a microporous gel matrix and trapping the clumped cells in the matrix.25 Microfluidic devices have been also developed for the automated detection of agglutination based on fiber optics,22 droplet microfluidics,23 and surface plasmon resonance.24 The above methods can be further adopted for rapid identification of agglutination and automated decision of a positive crossmatch. The high-throughput nature of the proposed platform can facilitate blood compatibility tests with multiple donors in a single transfusion as well as further expansion of the range of applications of the platform which require highthroughput separation of blood plasma.
Figure 4. High-throughput separation of blood plasma from whole blood. (a) Photographs showing the microfluidic pipet tip comprising eight parallel separation channels. A common reservoir for RBC outlets was assembled before separation. (b) Hand-held operation of the microfluidic pipet tip using the smart pipet, which generated a flow rate of 904.3 ± 15.6 μL min−1. The purity of the separated plasma was 99.88 ± 0.01% at a plasma extraction rate of 51 ± 1 μL min−1 (n = 3).
min−1 and improving separation purity by up to 99.88% compared with the throughput of 0.1 mL min−1 and the purity of 93% previously achieved using CSA devices.17 The enhanced device performance will facilitate downstream diagnostics and analysis of blood plasma by decreasing sample processing time and increasing sample quality. The platform exhibits a relatively low plasma recovery, as compared with previous blood-plasma separators based on filtration and centrifugation (Section S2). Further improvement in γ can be achieved by repeating the separation process with the sorted blood in the RBC reservoir. Since the separation channels of the microfluidic pipet tip are readily scalable, further throughput enhancement can be easily achieved by massive parallelization for large-scale blood processing. Connecting the outlet ports via tubing to collection tubes can further facilitate easy and safe recovery of separated blood components for their downstream clinical use. We then applied our platform to determine the compatibility between the blood of a donor and a recipient’s blood for blood transfusion, referred as a blood cross-match. A cross-match test needs to be done prior to any blood transfusion to prevent transfusion reactions and requires plasma separation from a recipient’s blood. A major cross-match is performed by mixing a recipient’s plasma with the RBCs of a donor and seeing if agglutination occurs (Figure 5a).22−24 As a model system, we
■
CONCLUSIONS In summary, our results demonstrate that the microfluidic pipet tip composed of CSA and DSA ridges has the advantages of reliable blood plasma separation without channel clogging, E
DOI: 10.1021/acs.analchem.6b04587 Anal. Chem. XXXX, XXX, XXX−XXX
Technical Note
Analytical Chemistry
(5) Edlow, A. G.; Bianchi, D. W. Biochim. Biophys. Acta, Mol. Basis Dis. 2012, 1822, 1970−1980. (6) Beck, M. L.; Tilzer, L. L. Transfus. Med. Rev. 1996, 10, 118−130. (7) Cui, F.; Rhee, M.; Singh, A.; Tripathi, A. Annu. Rev. Biomed. Eng. 2015, 17, 267−286. (8) Liu, C.; Liao, S. C.; Song, J.; Mauk, M. G.; Li, X.; Wu, G.; Ge, D.; Greenberg, R. M.; Yang, S.; Bau, H. H. Lab Chip 2016, 16, 553−560. (9) Gong, M. M.; Macdonald, B. D.; Vu Nguyen, T.; Van Nguyen, K.; Sinton, D. Biomicrofluidics 2013, 7, 44111. (10) Liu, C.; Mauk, M.; Gross, R.; Bushman, F. D.; Edelstein, P. H.; Collman, R. G.; Bau, H. H. Anal. Chem. 2013, 85, 10463−10470. (11) Lenshof, A.; Ahmad-Tajudin, A.; Järås, K.; Swärd-Nilsson, A. M.; Åberg, L.; Marko-Varga, G.; Malm, J.; Lilja, H.; Laurell, T. Anal. Chem. 2009, 81, 6030−6037. (12) Jiang, H.; Weng, X.; Chon, C. H.; Wu, X.; Li, D. J. Micromech. Microeng. 2011, 21, 085019. (13) Dimov, I. K.; Basabe-Desmonts, L.; Garcia-Cordero, J. L.; Ross, B. M.; Ricco, A. J.; Lee, L. P. Lab Chip 2011, 11, 845−850. (14) Davis, J. A.; Inglis, D. W.; Morton, K. J.; Lawrence, D. A.; Huang, L. R.; Chou, S. Y.; Sturm, J. C.; Austin, R. H. Proc. Natl. Acad. Sci. U. S. A. 2006, 103, 14779−14784. (15) Tripathi, S.; Kumar, Y. V.; Agrawal, A.; Prabhakar, A.; Joshi, S. S. Sci. Rep. 2016, 6, 26749. (16) Kersaudy-Kerhoas, M.; Kavanagh, D. M.; Dhariwal, R. S.; Campbell, C. J.; Desmulliez, M. P. Lab Chip 2010, 10, 1587−1595. (17) Kim, B.; Choi, S. Small 2016, 12, 190−197. (18) D’Silva, J.; Austin, R. H.; Sturm, J. C. Lab Chip 2015, 15, 2240− 2247. (19) Yan, S.; Zhang, J.; Li, M.; Alici, G.; Du, H.; Sluyter, R.; Li, W. Sci. Rep. 2014, 4, 5060. (20) Choi, S.; Song, S.; Choi, C.; Park, J. K. Anal. Chem. 2009, 81, 50−55. (21) Kim, B.; Choi, Y. J.; Seo, H.; Shin, E. C.; Choi, S. Small 2016, 12, 5159−5168. (22) Ramasubramanian, M. K.; Alexander, S. P. Biomed. Microdevices 2009, 11, 217−229. (23) Makulska, S.; Jakiela, S.; Garstecki, P. Lab Chip 2013, 13, 2796− 2801. (24) Ashiba, H.; Fujimaki, M.; Awazu, K.; Fu, M.; Ohki, Y.; Tanaka, T.; Makishima, M. Sensing and Bio-Sensing Research 2015, 3, 59−64. (25) Langston, M. M.; Procter, J. L.; Cipolone, K. M.; Stroncek, D. F. Transfusion 1999, 39, 300−305.
high-purity separation with no significant contamination by RBCs, and high-throughput separation with a high extraction rate of blood plasma. In combination with the smart pipet, the operational simplicity and cost-effectiveness of the microfluidic pipet tip can accelerate the translation of point-of-care technologies that require plasma sample preparation to be used in resource-limited clinical settings. For use of the proposed platform in clinical applications, the smart pipet tip and the smart pipet can be sterilized by autoclaving and packaged together in an aseptic container, thereby preventing potential contamination and making the platform suitable for use with clinical samples.
■
ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.analchem.6b04587. Detailed experimental methods including the principle and fabrication of the smart pipet, computational fluid dynamic simulation, and supporting figures (PDF) Supporting video 1 showing the focusing behavior of red blood cells in the r6 region of the type 1 device composed of continuous slant array ridges, taken at 1000 fps and played at 50 fps (AVI) Supporting video 2 showing the focusing behavior of red blood cells in the r6 region of the type 3 device composed of discrete slant array ridges, taken at 1000 fps and played at 50 fps (AVI) Supporting video 3 showing the entire operation to separate blood plasma using the microfluidic pipet tip and the smart pipet (AVI)
■
AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. ORCID
Sungyoung Choi: 0000-0002-9344-5943 Author Contributions
S.C. conceptualized and directed the research project. S.C. and B.K. prepared the manuscript. B.K., S.O., and D.Y. performed the experiments and data analysis with S.C. All authors discussed the results and commented on the manuscript. Notes
The authors declare no competing financial interest.
■
ACKNOWLEDGMENTS This research was supported by the Pioneer Research Center Program through the National Research Foundation (NRF) of Korea funded by the Ministry of Science, ICT & Future Planning (MSIP) (2013M3C1A3064777), a NRF grant funded by the Korea government (MSIP) (2014R1A2A2A09052449), and a NRF grant funded by the Korea government (MSIP) (2015R1C1A1A01053990).
■
REFERENCES
(1) Kersaudy-Kerhoas, M.; Sollier, E. Lab Chip 2013, 13, 3323−3346. (2) Gervais, L.; Delamarche, E. Lab Chip 2009, 9, 3330−3337. (3) Fan, R.; Vermesh, O.; Srivastava, A.; Yen, B. K.; Qin, L.; Ahmad, H.; Kwong, G. A.; Liu, C. C.; Gould, J.; Hood, L.; Heath, J. R. Nat. Biotechnol. 2008, 26, 1373−1378. (4) Humpel, C. Trends Biotechnol. 2011, 29, 26−32. F
DOI: 10.1021/acs.analchem.6b04587 Anal. Chem. XXXX, XXX, XXX−XXX
