BioMEMS Laboratory, Department of Biomedical Engineering, Rutgers, The State University of New Jersey, 599 Taylor Road, Piscataway, New Jersey 08854, USA.
Lab Chip. 2011 Sep 7;11(17):2858-68. doi: 10.1039/c1lc20080a. Epub 2011 Jul 12.
This report describes the design, fabrication, and testing of a cross-flow filtration microdevice, for the continuous extraction of blood plasma from a circulating whole blood sample in a clinically relevant environment to assist in continuous monitoring of a patient's inflammatory response during cardiac surgeries involving cardiopulmonary bypass (CPB) procedures (about 400,000 adult and 20,000 pediatric patients in the United States per year). The microfiltration system consists of a two-compartment mass exchanger with two aligned sets of PDMS microchannels, separated by a porous polycarbonate (PCTE) membrane. Using this microdevice, blood plasma has been continuously separated from blood cells in a real-time manner with no evidence of bio-fouling or cell lysis. The technology is designed to continuously extract plasma containing diagnostic plasma proteins such as complements and cytokines using a significantly smaller blood volume as compared to traditional blood collection techniques. The microfiltration device has been tested using a simulated CPB circulation loop primed with donor human blood, in a manner identical to a clinical surgical setup, to collect plasma fractions in order to study the effects of CPB system components and circulation on immune activation during extracorporeal circulatory support. The microdevice, with 200 nm membrane pore size, was connected to a simulated CPB circuit, and was able to continuously extract ~15% pure plasma volume (100% cell-free) with high sampling frequencies which could be analyzed directly following collection with no need to further centrifuge or modify the fraction. Less than 2.5 ml total plasma volume was collected over a 4 h sampling period (less than one Vacutainer blood collection tube volume). The results tracked cytokine concentrations collected from both the reservoir and filtrate samples which were comparable to those from direct blood draws, indicating very high protein recovery of the microdevice. Additionally, the cytokine concentration increased significantly compared to baseline values over the circulation time for all cytokines analyzed. The high plasma protein recovery (over 80%), no indication of hemolysis and low level of biofouling on the membrane surface during the experimental period (over 4 h) were all indications of effective and reliable device performance for future clinical applications. The simple and robust design and operation of these devices allow operation over a wide range of experimental flow conditions and blood hematocrit levels to allow surgeons and clinicians autonomous usage in a clinical environment to better understand the mechanisms of injury resulting from cardiac surgery, and allow early interventions in patients with excessive postoperative complications to improve surgical outcomes. Ultimately, monolithic integration of this microfiltration device with a continuous microimmunoassay would create an integrated microanalysis system for tracking inflammation biomarkers concentrations in patients for point-of-care diagnostics, reducing blood analysis times, costs and volume of blood samples required for repeated assays.
本报告介绍了一种用于连续从循环全血样本中提取血浆的横流过滤微器件的设计、制造和测试，该样本来自于临床相关环境中的患者，以辅助在涉及体外循环（CPB）手术的心脏手术期间连续监测患者的炎症反应。（每年约有 40 万成年患者和 2 万儿科患者在美国接受此类手术）。该微过滤系统由一个带有两个对齐的 PDMS 微通道的两室质量交换器组成，由多孔聚碳酸酯（PCTE）膜隔开。使用该微器件，可以实时连续地将血浆与血细胞分离，且没有生物污垢或细胞裂解的迹象。该技术旨在使用比传统采血技术显著更小的血量来连续提取包含补体和细胞因子等诊断性血浆蛋白的血浆。该微过滤装置已使用模拟 CPB 循环回路进行了测试，该回路使用供体人血预充，与临床手术设置完全相同，以收集血浆级分，从而研究 CPB 系统组件和循环对体外循环支持期间免疫激活的影响。该微器件的膜孔径为 200nm，与模拟 CPB 回路相连，能够以高采样频率连续提取约 15%的纯血浆量（100%无细胞），可直接在收集后进行分析，无需进一步离心或修改级分。在 4 小时的采样期内，仅收集了不到 2.5 毫升的总血浆量（不到一个 Vacutainer 采血管的体积）。结果表明，与直接采血相比，从储液器和滤液样本中收集的细胞因子浓度具有很好的跟踪性，表明该微器件的蛋白质回收率非常高。此外，与所有分析的细胞因子的基线值相比，在循环过程中细胞因子浓度显著增加。在实验期间（超过 4 小时），膜表面的高血浆蛋白回收率（超过 80%）、无溶血迹象和低生物污垢水平均表明该设备具有可靠的性能，适用于未来的临床应用。这些设备的简单而强大的设计和操作允许在广泛的实验流量条件和血液红细胞压积水平下运行，从而允许外科医生和临床医生在临床环境中自主使用，以更好地了解心脏手术引起的损伤机制，并允许对术后并发症过多的患者进行早期干预，以改善手术结果。最终，将这种微过滤装置与连续微免疫分析的单片集成将为跟踪患者炎症生物标志物浓度创建一个集成的微分析系统，用于即时诊断，减少血液分析时间、成本和重复分析所需的样本量。
