用于尿酸检测的氧化还原响应型光子晶体凝胶微球

Redox-responsive Photonic Crystal Gel Microspheres for Uric Acid Detection

摘要

针对目前尿酸检测存在依赖专业仪器、操作流程复杂的问题，提出一种直观简便的裸眼可视化检测尿酸含量的新方法。该方法采用四臂聚乙二醇丙烯酰胺（PEG）和N，N′‒双（丙烯酰）胱胺（BAC）作为双交联剂，聚乙烯吡咯烷酮包覆的四氧化三铁（Fe₃O₄@PVP）为构筑可显示结构色的光子晶体结构单元，通过微流控乳化和磁组装技术制备得到显色均匀的氧化还原响应型光子晶体凝胶微球（MPNC）；利用BAC内部的二硫键和巯基之间的可逆转换，可赋予凝胶还原条件下体积溶胀、氧化条件下收缩的性能，改变固定在微球基质中光子晶体的晶格间距，从而使其呈现出显著的色相变化。系统探究了Fe₃O₄@PVP纳米颗粒的粒径、浓度和施加的磁场强度对MPNC显色的影响，并考察最优条件制备的MPNC的循环稳定性、对不同尿酸浓度的响应变色性能和抗干扰性能。结果显示：在10 mT的磁场强度下，由粒径为182 nm、浓度为3 g⸱L^-1的Fe₃O₄@PVP制备的MPNC在氧化还原响应前后呈现从橙红色到蓝色的全色谱变化，并且在6次连续还原氧化的循环中表现出良好的稳定性；在尿酸酶的存在下，MPNC在检测0～0.60 mmol⸱L^-1的尿酸时，仅需100 µL的溶液体积即可实现从橙红色（616 nm）到蓝色（496 nm）的宽范围颜色变化，并且在人工血液和人工尿液中具有良好的抗干扰能力；当微球的颜色介于绿色和蓝色之间，则说明尿酸含量高于0.42 mmol⸱L^-1。研究表明，MPNC可作为比色传感器，为裸眼可视化检测尿酸水平提供一种简单直观的通用方法。

Abstract

Objective Currently available methods for uric acid detection rely on specialized equipment and complex procedures, which are inconvenient for applications such as point-of-care testing. Therefore, a simple and intuitive strategy for visual monitoring of uric acid levels is highly desired. In this paper, redox-responsive photonic crystal gel microspheres (MPNC) exhibiting iridescent color changes are successfully prepared. Methods The MPNC were constructed using poly (N-isopropylacrylamide) (PNIPAM) as the gel matrix, with embedded poly(vinylpyrrolidone)-coated magnetite (Fe₃O₄@PVP) nanoparticles as one-dimensional photonic crystal elements. During UV-initiated polymerization, precursor droplets containing the monomer N-isopropylacrylamide (NIPAM) were cross-linked into microspheres by four-armed poly (ethylene glycol) acrylamide (PEG) and N,N′-bis (acryloyl) cystamine (BAC) as a double cross-linking system. Simultaneously, the Fe₃O₄@PVP nanoparticles suspended in the droplets formed well-ordered chain-like photonic crystal structures under a magnetic field and were immobilized in the PNIPAM gel matrix, producing structural color. To obtain the precursor solution, monomer NIPAM, co-crosslinkers PEG and BAC, Fe₃O₄@PVP nanoparticles, surfactant Triton X-100, and photoinitiator 2-hydroxy-2-methyl-1-phenyl-1-acetone (HMPP) were sequentially dissolved in ethylene glycol. During microfluidic emulsification, the precursor solution (internal phase) was dispersed into droplets by soybean oil containing the surfactant polyisobutylene succinimide (T-154) as the external phase. The reversible conversion between sulfhydryl and disulfide bonds in BAC during oxidation-reduction reactions caused swelling and shrinking of the redox-responsive gel, changing the lattice spacing of the photonic crystals and resulting in significant chromatic changes. The four-arm crosslinking of PEG improved the homogeneity of microsphere volume changes and also served as a stable scaffold. By optimizing the size and concentration of Fe₃O₄@PVP nanoparticles and the applied magnetic field strength, MPNC with iridescent color responses to hydrogen peroxide (H₂O₂) were obtained. The response properties of optimized MPNC toward uric acid, as well as their cyclic stability and anti-interference performance, were investigated. Before testing, the gel microspheres were placed in an aqueous solution of the reducing agent DL-dithiothreitol (DTT), forming sulfhydryl groups and fully swelling the microspheres. During detection, the microspheres were transferred into phosphate buffer solution containing uric acid. The H₂O₂ generated from uric acid catalyzed by uricase oxidized sulfhydryl groups into disulfide bonds. At this stage, the cross-linking degree increased, and the lattice spacing between adjacent nanoparticles fixed in the gel matrix decreased. Results and Discussions The redox-responsive photonic crystal gel microspheres were successfully prepared by microfluidic emulsification with an inner-phase flow rate of 400 μL⸱L^-1 and an outer-phase flow rate of 1 000 μL⸱L^-1, and with a molar ratio of PEG to BAC of 1∶28, showing regular spherical and uniform morphology. Compared with the high deswelling ratio (DSR) of 0.96 for microspheres without BAC (MPN‒0), all microspheres with BAC (MPN‒1, MPNC‒152, MPNC‒182, and MPNC‒209) showed a lower DSR of 0.38, indicating redox responsiveness. The addition of Fe₃O₄@PVP magnetic particles had no effect on the size or redox-responsive performance of the MPNC. One-dimensional photonic crystal chains formed by self-assembly of Fe₃O₄@PVP nanoparticles were observed in scanning electron microscope images of microsphere cross sections. By adjusting nanoparticle size and concentration, it was found that size significantly affected the redox-responsive color change of MPNC, while concentration mainly influenced structural color brightness. The color of MPNC gradually blue-shifted as the magnetic field strength increased from 6 to 16 mT during preparation. At 10 mT, MPNC‒182 prepared with Fe₃O₄@PVP nanoparticles of 182 nm size and 3 g⸱L^-1 concentration showed the widest color change from orange-red to blue before and after H₂O₂ response, with a diffraction wavelength variation of 140 nm. The diffraction wavelengths of the optimized MPNC under reduction by DTT and oxidation by H₂O₂ fluctuated slightly around their mean values over six consecutive cycles, demonstrating good stability and repeatability. In the presence of uricase, MPNC showed a wide color change from orange-red (616 nm) to blue (496 nm) for detecting uric acid in the range of 0～0.60 mmol⸱L^-1 with a solution volume of 100 µL. The linear correlation between uric acid concentration and diffraction wavelength indicates that MPNC‒182 has high accuracy. If the microsphere color is between green and blue, the uric acid level exceeds 0.42 mmol⸱L^-1, indicating a risk of hyperuricemia. To further verify practicality, artificial blood and urine environments were simulated to evaluate interference effects. The maximum wavelength deviation was only 10 nm, indicating satisfactory anti-interference performance and potential for use in body fluid detection. Conclusions The results show that MPNC can be used as a colorimetric sensor, providing a simple, intuitive, and versatile strategy for visualizing uric acid levels with the naked eye. This provides theoretical guidance and an experimental basis for the design and fabrication of redox-responsive photonic crystal gels.

Graphical abstract

关键词

尿酸 / 微流体技术 / 磁性颗粒 / 光子晶体凝胶微球 / 氧化还原 / 裸眼检测

Key words

uric acid / microfluidics / magnetite nanoparticles / photonic crystal gel microspheres / redox / naked-eye detection

本刊网刊

尿酸是体液中一种重要的生物分子，在调节人体代谢活动中发挥着重要作用^[1]，在血液和尿液中的含量正常范围分别为0.09～0.42 mmol⸱L^-1[2]和0.20～4.40 mmol⸱L^-1[3]。血尿酸含量超过0.42 mmol⸱L^-1会导致尿酸盐过饱和而在体内结晶析出，增加高尿酸血症的患病概率，易引起痛风^[4]、肾结石^[5]和肾功能受损^[6‒7]等多种并发症。迄今，高尿酸已成为除高血压、高血脂、高血糖外的“第四高”，因此，可视化尿酸含量检测在身体生理活动日常监测、痛风的早期诊断以及在高尿酸血症产生原因的排查等方面具有重要意义。

目前常见的尿酸检测方法有高效液相色谱法^[8‒10]，电化学法^[11‒15]和紫外分光光度法^[16‒19]等，但这些方法往往需要专业仪器和复杂的操作流程，耗费的时间长、成本高，而比色法可通过裸眼可见的颜色变化直观分析，具有操作简单、价格低廉并且实用性强的优点，在便携使用方面具有突出的优势^[20‒22]。光子晶体作为一种人造的周期性结构，能通过调制晶格间距在可见光区域产生明亮的彩虹色变化，且具有不易褪色的优势^[23]。智能水凝胶能感知外界环境刺激而发生显著体积变化，与光子晶体结合制成的生物化学传感器已逐渐成为研究热点^[24‒26]。由于尿酸的化学性质相对不活泼，目前鲜有通过光子晶体凝胶直接检测尿酸的报道，但有对尿酸酶与尿酸的特异性反应产物过氧化氢（H₂O₂）检测的相关研究^[27‒29]。Liu等^[27]制备了二维光子晶体，并将牛血清蛋白和过氧化物酶通过戊二醛交联复合，得到蛋白水凝胶传感器。该传感器利用过氧化物酶特异性识别H₂O₂，使凝胶结构由环状裂解为链状，引发水凝胶体积溶胀，进而增大光子晶体的晶格，其晶体颜色由绿色变化到红色，波长迁移为49 nm。Sun等^[28]通过紫外光引发聚合制备了一种多糖基半互穿网络的聚丙烯酰胺（PAM）三维光子晶体水凝胶，利用白芨多糖能清除H₂O₂产生的·OH自由基，降低与PAM中氢键的相互作用，导致水凝胶溶胀，从而改变光子晶体衍射出的结构色，最大波长迁移值约为100 nm。然而，二维和三维光子晶体均存在制备流程复杂且色相不均一的问题，导致裸眼辨别存在较大误差^[30]。因此，开发一种显色均匀、操作简便且裸眼可视化检测尿酸的新方法仍有挑战。

本文以四臂聚乙二醇丙烯酰胺（PEG）和N,N′‒双（丙烯酰）胱胺（BAC）为双交联剂，聚乙烯吡咯烷酮包覆的四氧化三铁（Fe₃O₄@PVP）磁性纳米颗粒为一维光子晶体结构单元，采用微流控乳化技术制备油包水型凝胶预聚液微液滴，在外加磁场和紫外光的条件下聚合制备得到以聚异丙基丙烯酰胺（PNIPAM）为凝胶基质的氧化还原响应型光子晶体凝胶微球（MPNC）。其中，大分子PEG的四臂交联不仅能提高凝胶微球网络结构的均匀性，而且可作为一种固定的交联剂增加凝胶的强度。而BAC作为一种功能交联剂，其内部的二硫键和巯基之间的可逆转换能赋予凝胶氧化还原响应条件下体积收缩和溶胀的性能^[31‒32]。检测尿酸前，将凝胶微球浸没在还原剂DL‒二硫苏糖醇（DTT）水溶液中，微球中的二硫键会被还原而断裂为巯基，此时凝胶微球溶胀。检测时，利用尿酸酶特异性催化尿酸产生的H₂O₂，将巯基氧化为二硫键，此时凝胶微球的交联程度增加、体积收缩，使得固定于凝胶基质中的相邻磁性颗粒间的晶格间距减小、结构色蓝移。本文系统探究了Fe₃O₄@PVP纳米颗粒的粒径、浓度和施加磁场强度对MPNC显色的影响，并考察最优条件制备的MPNC的循环稳定性、对不同尿酸浓度的响应变色性能和抗干扰性能。

1 实验材料和方法

1.1 实验材料

N‒异丙基丙烯酰胺（NIPAM，纯度＞98%），2‒羟基2‒甲基‒1‒苯基‒1‒丙酮（HMPP，分析纯），上海梯希爱；D(+)‒无水葡萄糖（分析纯），乙二醇（EG，分析纯），曲拉通（Triton-X-100，纯度>98%），国药化试；聚异丁烯双丁二酰亚胺（T-154，纯度>98%），广州锐圣研；PEG（纯度>95%，分子量为5 000 Da），上海芃硕；BAC（纯度>98%），尿酸酶（酶活性⩾20 U⸱mg^-1），尿素（纯度>99%），上海麦克林；DTT，磷酸盐缓冲溶液（PBS，pH=7.2），尿酸，抗坏血酸，多巴胺，肌酐，纯度>99%，上海阿拉丁；H₂O₂，分析纯，成都科隆；二次纯水来自Integral 5纯水系统，电阻率>18.2 MΩ⸱cm，美国Millipore。

1.2 光子晶体凝胶微球的制备

根据文献[33‒34]报道的溶剂热法，在200 ℃下合成得到水合粒径为152、182、209 nm的Fe₃O₄@PVP磁性颗粒，均具有良好的单分散性。采用如图1所示的单级微流控装置制备凝胶微球，其中注射管和收集管均为圆柱形中空玻璃管，内径分别为550 μm（锥口内径为200 μm）和700 μm，外径均为960 μm。将0.226 2 g NIPAM、0.02 g PEG、0.029 2 g BAC、Fe₃O₄@PVP磁性颗粒、22 μL表面活性剂Triton-X-100和3 μL光引发剂HMPP依次溶于600 μL EG中得到内相流体，流速为400 μL⸱h^-1。大豆油和表面活性剂T-154以28∶1的质量比混合得到外相流体，流速为1 000 μL⸱h^-1。用大豆油收集由微流控乳化制备的凝胶微球预聚液微液滴。Fe₃O₄@PVP磁性颗粒在垂直磁场中迅速自组装成一维链状并衍射出明亮的结构色，再由紫外光引发聚合120 s形成MPNC。将清洗后的微球放入还原剂DTT溶液中，使BAC中的二硫键完全还原巯基，再转移至含有尿酸和尿酸酶的PBS溶液中，其反应产物H₂O₂可将巯基氧化成二硫键使微球体积收缩，同时光子晶体的晶格间距减小，色相发生蓝移，从而实现比色检测尿酸的目的。

通过改变BAC含量、Fe₃O₄@PVP的粒径以及磁场强度制备得到不同性能的凝胶微球，凝胶微球的配方见表1。

1.3 凝胶微球的形貌和微观结构表征

采用生物显微镜（Axio Scope. A1，上海蔡司）拍摄微球的光学显微图片并测量直径，通过式（1）计算微球粒径的偏差系数C_V：

C_{\mathrm{V}}=\frac{\mathrm{1}}{\overline{d}}\sqrt[]{\frac{\mathrm{1}}{n-\mathrm{1}}{\displaystyle \sum _{i=\mathrm{1}}^n}(d_i{-\overline{d})}^{\mathrm{2}}}\times \mathrm{100}\mathrm{\%}（1）

式中：\overline{d}为微球的算术平均直径，nm；d_i 为第i个微球的直径，nm；n为微球总数目。

将微球在-50 ℃下真空冷冻干燥12 h，获得干燥的凝胶微球样品。利用台式扫描电子显微镜（SEM；Phenom Pro 6，上海复纳科学）和能量色散X射线光谱仪（EDS；X-MaxN，英国Oxford）对其微观结构和元素组成进行分析。

1.4 凝胶微球的氧化还原响应性能表征

利用生物显微镜分别拍摄微球在DTT水溶液和含有H₂O₂或不同尿酸浓度的PBS溶液中响应12 h达到平衡后的光学照片，并测量微球直径。利用式（2）计算凝胶微球被H₂O₂或尿酸氧化后和初始还原状态的体积比，即退溶胀率D_SR为：

D_{\mathrm{S}\mathrm{R}}=\frac{V_{\mathrm{1}}}{V_{\mathrm{0}}}={\left(\frac{D_{\mathrm{1}}}{D_{\mathrm{0}}}\right)}^{\mathrm{3}}（2）

式中：V₀和V₁分别为凝胶微球在含有H₂O₂或尿酸的PBS溶液中响应前和响应后的体积，μm³；D₀和D₁分别为凝胶微球在响应前后的直径，μm。

1.5 光子晶体微球的光学性能表征

用数码相机和光纤光谱仪（FLAME-S-VIS-NIR-ES，美国Ocean optics）记录MPNC在DTT溶液（响应前）和含有H₂O₂或不同尿酸浓度的PBS溶液（响应后）中的光学照片和反射光谱，比较响应前后的颜色变化和波长迁移，并通过6个循环测试其在DTT和H₂O₂溶液中平衡12 h的波长响应来评估其重复稳定性。

1.6 光子晶体微球的尿酸响应性能表征

用数码相机和光纤光谱仪记录MPNC在含有0～0.60 mmol⸱L^-1尿酸和2 μL 1.6 g⸱L^-1的尿酸酶溶液的PBS溶液（100 μL）中响应12 h达到平衡后的光学图片和反射光谱，来表征其对不同尿酸浓度的响应性能。实验证明，在浓度为0.60 mmol⸱L^-1的尿酸PBS溶液中，凝胶微球可在5 h内达到响应平衡。

以含有0.42 mmol⸱L^-1尿酸和2 μL 1.6 g⸱L^-1尿酸酶的PBS溶液为空白对照组，在此基础上分别添加抗坏血酸、葡萄糖、多巴胺以及三者的混合物配置血液干扰体系，并添加尿素、肌酐以及二者的混合物配置尿液干扰体系，通过比较MPNC在上述体系中衍射波长值的差异表征抗干扰性能。

2 结果与讨论

2.1 凝胶微球的形貌结构和化学成分表征

2.1.1 光学形貌表征

图2为微球的光学显微图像。从图2可看出，5种微球（制备配方见表1）均为规则球形，并由式（1）计算得到它们的C_V值均小于2%，证明由微流控制备的微球单分散性优异。MPN‒0和MPN‒1呈无色透明（图2（a）～（b）、（f）～（g）），由式（2）计算出充分响应H₂O₂后得到的退溶胀率D_SR分别为0.96和0.38，差异较大是由于MPN‒1中添加的BAC赋予微球氧化还原响应性能，从而表现出显著的体积变化。MPNC‒152、MPNC‒182、MPNC‒209中由于添加了深色Fe₃O₄@PVP而呈不透明状态（图2（c）～（e）、（h）～（j）），它们的D_SR与MPN‒1一致，并且绝对直径与MPN‒1响应前（828 μm）和响应后（598 μm）均相近，证明Fe₃O₄@PVP的添加不影响凝胶微球的粒径和氧化还原响应性能。

2.1.2 微观结构和化学成分表征

图3为微球断面SEM图。从图3可以看出，5种凝胶微球在微观上均呈现多孔结构。MPN‒0和MPN‒1中由于未添加磁性颗粒，因此基质的空腔内壁十分光滑（图3（a）～（b）、（f）～（g）），而在图3（c）～（e）、（h）～（j）中观察到MPNC内部出现大量颗粒呈一维有序规则链状分布。结合表1的EDS元素分析可知，除MPN‒0外，其余4种微球均检测到S元素（表1），证明BAC成功参与了凝胶微球的形成。与MPN‒0和MPN‒1相比，MPNC‒152、MPNC‒182、MPNC‒209均有Fe元素出现，表明SEM图中观察到的颗粒为投料添加的Fe₃O₄@PVP磁性颗粒，并且在磁场作用下自组装成的一维链状光子晶体结构成功嵌入到凝胶微球基质中。

2.2 光子晶体微球的响应变色性能

MPNC的色相变化与构筑光子晶体结构的Fe₃O₄@PVP磁性颗粒的粒径和浓度以及制备时施加的磁场强度有关。因此，在固定磁场强度为10 mT的条件下，首先探究与MPN‒1复合制备得到的、含有3种不同粒径和浓度的Fe₃O₄@PVP构成的MPNC被H₂O₂氧化前后的变色性能，结果如图4所示。当磁性颗粒粒径过小（152 nm）时，MPNC在响应前的还原溶胀会使磁性颗粒之间的晶格间距过大，从而难以观察到结构色。对于含有182 nm磁性颗粒的光子晶体凝胶微球，可裸眼观察到微球从橙红色迁移至蓝色的结构色变化。而对于含有209 nm Fe₃O₄@PVP的光子晶体微球，裸眼可直接观察到响应前后其从橙红到黄的结构色变化，色相变化区间窄，不能实现全色谱变化。浓度为2 g⸱L^-1制备的微球颜色略暗，这是因为低浓度下的磁颗粒构筑的一维光子晶体链分布密度较小，导致衍射波长的叠加效应弱。当浓度增加为3 g⸱L^-1时，MPNC显示出最明亮的结构色；但由于Fe₃O₄@PVP是一种深色材料，当浓度进一步增加至4 g⸱L^-1时，光吸收率增加，导致光子晶体反射强度降低，颜色偏暗。可见，磁性颗粒的粒径影响光子晶体微球色相变化范围，而浓度仅影响结构色明亮程度。粒径为182 nm、浓度为3 g⸱L^-1的Fe₃O₄@PVP制备的MPNC在氧化还原响应时具有最宽的色相变化范围。

在上述最佳的粒径和浓度的条件下，研究施加的磁场强度对光子晶体微球显色范围的影响。如图5（a）所示，随着磁场强度的增大，MPNC的颜色逐渐蓝移，这是由于Fe₃O₄@PVP产生的磁吸引力增加，相邻磁性颗粒的晶格间距减小，衍射波长变短。在6 mT下制备的MPNC在响应前观察不到结构色是由于磁场强度过小，产生的磁吸引力不足以使磁性颗粒有序排列以产生结构色。在12、14和16 mT时制备的微球在响应后完全失去结构色，这是由微球收缩破坏了光子晶体有序链状结构导致的。在响应前后均能观察到结构色的磁场强度只有8 mT和10 mT。根据图5（b）的响应前后的反射光谱图可得，8 mT和10 mT对应的波长迁移值分别为93 nm和140 nm。相比之下，由磁场强度为10 mT制备的MPNC‒182具有最宽的衍射波长区间。

2.3 光子晶体微球响应变色的循环稳定性

MPNC‒182交替在DTT溶液和含有H₂O₂的PBS溶液中6个循环的衍射波长值如图6所示。MPNC‒182在被DTT还原和被H₂O₂氧化的衍射波长均在各自平均值附近微小波动。经计算，MPNC‒182在6次循环中还原态和氧化态的衍射波长平均值分别为618±2 nm和476±3 nm，最大波长偏差仅为3 nm，说明制备的MPNC在还原和氧化等环境下均具有良好的稳定性和可重复性，可多次循环使用。

2.4 光子晶体微球对不同尿酸浓度的响应变色性能

尿酸的溶解度不高，在超过临界浓度0.42 mmol⸱L^-1时易结晶析出，因此考察了MPNC‒182对尿酸浓度范围为0～0.60 mmol⸱L^-1的响应变色性能，结果如图7（a）、（b）所示。随着尿酸浓度的增加，MPNC‒182的颜色从橙红色（616 nm）迁移至蓝色（496 nm），这是因为微球中的BAC含量固定，当尿酸浓度增大时，尿酸酶特异性识别尿酸生成的H₂O₂也随之增多，进而使微球被氧化收缩的程度加剧；同时缩小了固定在微球基质中的一维光子晶体的晶格间距，最终表现为结构色蓝移。从尿酸浓度和衍射波长之间进行相关性拟合的结果（图7（c））可知，尿酸浓度与衍射波长呈线性负相关，说明MPNC‒182对尿酸浓度检测具有良好的准确性。为了更直观地比较结构色之间的差异，将图7（b）中的衍射波长转化为国际照明委员会标准（CIE1931）色度坐标，如图7（d）所示。可见，色度坐标在色度图中相互独立、均匀分布且覆盖范围广，说明MPNC‒182检测不同尿酸浓度的色相差异明显，有利于裸眼识别。综上，MPNC‒182检测0～0.60 mmol⸱L^-1的尿酸时，仅需100 µL溶液体积即可具有宽范围的响应变色性能，并且当裸眼观测到MPNC‒182的颜色介于绿色和蓝色之间，可视为尿酸含量高于0.42 mmol⸱L^-1，存在患高尿酸的风险。

2.5 光子晶体凝胶微球的抗干扰性能

采用100 µL含有0.42 mmol⸱L^-1尿酸的PBS缓冲溶液为空白对照组，在此基础上分别加入抗坏血酸、多巴胺、葡萄糖及三者的混合物模拟人工血液，以及加入肌酐、尿素及两者混合物模拟人工尿液，来探究血液和尿液中的干扰成分对衍射波长的影响。不同干扰体系中物质的种类和含量以及微球响应后的衍射波长见表2。将MPNC‒182分别置于上述体系中，并加入2 μL 1.6 g⸱L^-1的尿酸酶溶液，响应12 h后的衍射波长如图8所示。无论是血液体系还是尿液体系，MPNC‒182响应尿酸的衍射波长均在522～538 nm之间。与空白对照组的波长（528 nm）相比，最大波长差值仅为10 nm，说明MPNC‒182具有良好的抗干扰能力，有望被应用于体液的尿酸检测。

3 结 论

通过微流控和磁组装技术成功制备得到以二硫键为官能团的氧化还原响应型MPNC。在10 mT的磁场强度下，由粒径为182 nm、浓度为3 g⸱L^-1的Fe₃O₄@PVP磁性颗粒制备的MPNC‒182被H₂O₂氧化前后呈现从橙红色到蓝色的宽色谱变化，并在6次连续循环中表现出良好的稳定性和可重复性。MPNC在检测0～0.60 mmol⸱L^-1的尿酸时，仅需100 µL的溶液体积即可实现从橙红色（616 nm）到蓝色（496 nm）的宽范围颜色变化。当微球的颜色介于绿色和蓝色之间，则可视为尿酸含量高于0.42 mmol⸱L^-1。此外，MPNC在人工血液和尿液中具有良好的抗干扰能力。研究成果为裸眼可视化监测尿酸含量提供了新思路。

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基金资助

四川省杰出青年科技基金项目(2019JDJQ0026)

四川大学工科特色团队项目(2020SCUNG112)