Ho Nga T, Fan Andy, Klapperich Catherine M, Cabodi Mario
Boston University, Department of Biomedical Engineering, USA.
Annu Int Conf IEEE Eng Med Biol Soc. 2012;2012:2396-9. doi: 10.1109/EMBC.2012.6346446.
The ability to increase the concentration of target analytes in a fixed sample volume can potentially lower the limit of detection for many biosensing techniques, and thus is key in sample preparation for infectious disease diagnosis. Concentration by evaporation is an effective method to achieve target enrichment. However, concentrating human samples, including blood and plasma, by evaporation-based methods is made challenging by high concentrations of proteins and electrolytes. Dehydration of the proteins causes the sample to turn into a gel, hindering further analysis. At the same time, decreasing the volume increases the overall concentration of electrolytes, causing bacterial or viral particle lysis, and making them more difficult to detect in affinity-based biosensors. Thus, we fabricated a microfluidic chip that incorporates both dialysis and concentration in a single design. The chip dialyzes the proteins from the plasma, while maintaining an appropriate concentration of electrolytes and concentrating the sample targets. The process to concentrate plasma or serum samples by a factor of 10 takes less than 30 minutes. As a proof-of-concept, we demonstrated the chip using a defective Human Immunodeficiency Virus (HIV). To distinguish patients on antiretroviral therapy who are failing therapy from those who are not, a diagnostic must be able to detect HIV in plasma down to at least 1000 particles per milliliter. For a number of technical reasons, it is difficult to get on-chip PCR reactions to reach this level of sensitivity, so concentration of HIV from lower viral load samples has the potential to improve the sensitivity of many types of molecular point-of-care viral load tests.
在固定样本体积中提高目标分析物浓度的能力，有可能降低许多生物传感技术的检测限，因此是传染病诊断样本制备的关键。通过蒸发进行浓缩是实现目标富集的有效方法。然而，基于蒸发的方法对包括血液和血浆在内的人体样本进行浓缩时，会因蛋白质和电解质的高浓度而面临挑战。蛋白质脱水会使样本变成凝胶，阻碍进一步分析。同时，体积减小会增加电解质的总体浓度，导致细菌或病毒颗粒裂解，使其在基于亲和力的生物传感器中更难检测。因此，我们制造了一种微流控芯片，该芯片在单一设计中结合了透析和浓缩功能。该芯片能从血浆中透析出蛋白质，同时保持适当的电解质浓度并浓缩样本目标物。将血浆或血清样本浓缩10倍的过程耗时不到30分钟。作为概念验证，我们使用缺陷型人类免疫缺陷病毒（HIV）展示了该芯片。为了区分接受抗逆转录病毒治疗但治疗失败的患者和未失败的患者，诊断必须能够检测出血浆中每毫升至少1000个颗粒的HIV。由于一些技术原因，芯片上的聚合酶链反应很难达到这种灵敏度水平，因此从低病毒载量样本中浓缩HIV有可能提高许多类型分子即时检测病毒载量测试的灵敏度。
