Department of Chemistry, University of North Carolina, Chapel Hill, NC 27599, USA.
Biomaterials. 2010 Nov;31(33):8810-7. doi: 10.1016/j.biomaterials.2010.07.087. Epub 2010 Aug 16.
Microfabricated devices possessing magnetic properties are of great utility in bioanalytical microdevices due to their controlled manipulation with external magnets. Current methods for creating magnetic microdevices yield a low-transparency material preventing light microscopy-based inspection of biological specimens on the structures. Uniformly transparent magnetic photoresists were developed for microdevices that require high transparency as well as consistent magnetism across the structure. Colloidal formation of 10 nm maghemite particles was minimized during addition to the negative photoresists SU-8 and 1002F through organic capping of the nanoparticles and utilization of solvent-based dispersion techniques. Photoresists with maghemite concentrations of 0.01-1% had a high transparency due to the even dispersal of maghemite nanoparticles within the polymer as observed with transmission electron microscopy (TEM). These magnetic photoresists were used to fabricate microstructures with aspect ratios up to 4:1 and a resolution of 3 μm. Various cell lines showed excellent adhesion and viability on the magnetic photoresists. An inspection of cells cultured on the magnetic photoresists with TEM showed cellular uptake of magnetic nanoparticles leeched from the photoresists. Cellular contamination by magnetic nanoparticles was eliminated by capping the magnetic photoresist surface with native 1002F photoresist or by removing the top layer of the magnetic photoresist through surface roughening. The utility of these magnetic photoresists was demonstrated by sorting single cells (HeLa, RBL and 3T3 cells) cultured on arrays of releasable magnetic micropallets. 100% of magnetic micropallets with attached cells were collected following release from the array. 85-92% of the collected cells expanded into colonies. The polymeric magnetic materials should find wide use in the fabrication of microstructures for bioanalytical technologies.
微制造设备具有磁性，由于可以在外磁场的控制下进行操作，因此在生物分析微器件中非常有用。目前制造磁性微器件的方法会产生低透明度的材料，从而阻止基于光的显微镜对结构上的生物样本进行检查。开发了均匀透明的磁性光致抗蚀剂，用于需要高透明度和整个结构一致磁性的微器件。通过纳米颗粒的有机封端和溶剂分散技术的利用，最大限度地减少了 10nm 磁铁矿颗粒在添加到负性光致抗蚀剂 SU-8 和 1002F 中的胶体形成。由于在聚合物中均匀分散了磁铁矿纳米颗粒，因此具有 0.01-1%磁铁矿浓度的光致抗蚀剂具有很高的透明度，这可以通过透射电子显微镜（TEM）观察到。这些磁性光致抗蚀剂用于制造高达 4:1 的纵横比和 3μm 的分辨率的微结构。各种细胞系在磁性光致抗蚀剂上表现出良好的粘附和活力。用 TEM 检查在磁性光致抗蚀剂上培养的细胞显示出从光致抗蚀剂中浸出的磁性纳米颗粒被细胞摄取。通过用原始的 1002F 光致抗蚀剂覆盖磁性光致抗蚀剂表面或通过通过表面粗糙化去除磁性光致抗蚀剂的顶层来消除磁性纳米颗粒对细胞的污染。通过在可释放的磁性微托盘阵列上培养的单细胞（HeLa、RBL 和 3T3 细胞）的分选，证明了这些磁性光致抗蚀剂的实用性。从阵列上释放后，收集到了 100％带有细胞的磁性微托盘。收集到的细胞中有 85-92％扩展成了菌落。这些聚合物磁性材料应该在生物分析技术的微结构制造中得到广泛应用。
