Kaar Joel L, Oh Heung-Il, Russell Alan J, Federspiel William J
McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA 15219, USA.
Biomaterials. 2007 Jul;28(20):3131-9. doi: 10.1016/j.biomaterials.2007.03.021. Epub 2007 Mar 21.
Inefficient CO(2) removal due to limited diffusion represents a significant barrier in the development of artificial lungs and respiratory assist devices, which use hollow fiber membranes (HFMs) as the blood-gas interface and can require large blood-contacting membrane area. To offset the underlying diffusional challenge, "bioactive" HFMs that facilitate CO(2) diffusion were prepared via covalent immobilization of carbonic anhydrase (CA), an enzyme which catalyzes the conversion of bicarbonate in blood to CO(2), onto the surface of plasma-modified conventional HFMs. This study examines the impact of enzyme attachment on the diffusional properties and the rate of CO(2) removal of the bioactive membranes. Plasma deposition of surface reactive hydroxyls, to which CA could be attached, did not change gas permeance of the HFMs or generate membrane defects, as determined by scanning electron microscopy, when low plasma discharge power and short exposure times were employed. Cyanogen bromide activation of the surface hydroxyls and subsequent modification with CA resulted in near monolayer enzyme coverage (88%) on the membrane. The effect of increased plasma discharge power and exposure time on enzyme loading was negligible while gas permeance studies showed enzyme attachment did not impede CO(2) or O(2) diffusion. Furthermore, when employed in a model respiratory assist device, the bioactive membranes improved CO(2) removal rates by as much as 75% from physiological bicarbonate solutions with no enzyme leaching. These results demonstrate the potential of bioactive HFMs with immobilized CA to enhance CO(2) exchange in respiratory devices.
由于扩散受限导致的二氧化碳清除效率低下，是人工肺和呼吸辅助装置发展中的一个重大障碍，这些装置使用中空纤维膜（HFMs）作为血气界面，可能需要大面积的血液接触膜。为了应对潜在的扩散挑战，通过将碳酸酐酶（CA）共价固定在等离子体改性的传统HFMs表面，制备了促进二氧化碳扩散的“生物活性”HFMs。碳酸酐酶是一种催化血液中碳酸氢盐转化为二氧化碳的酶。本研究考察了酶附着对生物活性膜扩散特性和二氧化碳清除速率的影响。当采用低等离子体放电功率和短暴露时间时，扫描电子显微镜测定结果表明，可附着CA的表面反应性羟基的等离子体沉积，并未改变HFMs的气体渗透率，也未产生膜缺陷。用溴化氰活化表面羟基并随后用CA进行修饰，导致膜上酶覆盖率接近单层（88%）。等离子体放电功率和暴露时间增加对酶负载量的影响可忽略不计，而气体渗透率研究表明，酶附着并未阻碍二氧化碳或氧气的扩散。此外，当在模型呼吸辅助装置中使用时，生物活性膜可将生理碳酸氢盐溶液中的二氧化碳清除率提高多达75%，且没有酶渗漏。这些结果证明了固定有CA的生物活性HFMs在增强呼吸装置中二氧化碳交换方面的潜力。
