Vaddiraju Santhisagar, Singh Hardeep, Burgess Diane J, Jain Faquir C, Papadimitrakopoulos Fotios
Nanomaterials Optoelectronics Laboratory, Polymer Program, Institute of Materials Science, University of Connecticut, Storrs, Connecticut 06269, USA.
J Diabetes Sci Technol. 2009 Jul 1;3(4):863-74. doi: 10.1177/193229680900300434.
High linearities, sensitivities, and low oxygen dependence constitute prime requisites for electrochemical glucose sensors. However, for implantable sensors the need to control tissue inflammation requires the use outer membranes that permit inward analyte diffusion while continuously releasing anti-inflammatory drugs and other tissue response-modifying (TRM) agents. We have shown previously that while outer membranes based on layer-by-layer (LBL) assembly enhance linearity, poly(vinyl alcohol)(PVA) hydrogels loaded with TRM-containing microspheres enable a significant reduction in tissue inflammation. This article discusses amperometric performance of glucose sensors coated with stacked LBL/PVA hydrogel outer membranes.
Sensors were fabricated by immobilizing glucose oxidase enzyme on a 50-microm platinum wire followed by deposition of stacked LBL/PVA hydrogel outer membranes. The sensor response to various glucose concentrations was determined by applying 0.7 V vs an Ag/AgCl reference electrode in phosphate-buffered saline (37 degrees C). Michaelis-Menten analysis was performed to quantify sensor performance in terms of linearity (K(m,glu)(app)) and oxygen dependence (K(m,O(2))(app)/[Glucose]).
When overlaid onto LBL-assembled outer membranes, PVA hydrogels improved sensor linearity by 60% from 10 to 16 mM of glucose and resulted in a twofold decrease in oxygen dependence.
Enhancement in the performance of a PVA-coated sensor is attributed to the oxygen-storing capability of PVA hydrogel due to the formation of hydrophobic domains during its freezing and thawing employed to physical cross-link the PVA. Such membranes with the capability to release TRMs continuously while storing oxygen constitute a major improvement over current outer membrane technologies.
高线性度、灵敏度以及低氧依赖性是电化学葡萄糖传感器的主要要求。然而，对于可植入传感器而言，控制组织炎症的需求要求使用能够允许分析物向内扩散，同时持续释放抗炎药物和其他组织反应调节（TRM）剂的外膜。我们之前已经表明，基于层层（LBL）组装的外膜可增强线性度，而负载含TRM微球的聚乙烯醇（PVA）水凝胶能够显著减轻组织炎症。本文讨论了涂覆有堆叠LBL/PVA水凝胶外膜的葡萄糖传感器的安培性能。
通过将葡萄糖氧化酶固定在一根50微米的铂丝上，随后沉积堆叠的LBL/PVA水凝胶外膜来制造传感器。在磷酸盐缓冲盐水（37℃）中，相对于Ag/AgCl参比电极施加0.7V电压，测定传感器对各种葡萄糖浓度的响应。进行米氏分析以根据线性度（表观葡萄糖米氏常数K(m,glu)(app)）和氧依赖性（表观氧米氏常数K(m,O(2))(app)/[葡萄糖]）来量化传感器性能。
当覆盖在LBL组装的外膜上时，PVA水凝胶使传感器在葡萄糖浓度从10mM至16mM范围内的线性度提高了60%，并使氧依赖性降低了两倍。
涂覆PVA的传感器性能的提高归因于PVA水凝胶的储氧能力，这是由于在用于对PVA进行物理交联的冻融过程中形成了疏水区域。这种能够在储存氧气的同时持续释放TRM的膜是对当前外膜技术的重大改进。
