中国激光, 2023, 50 (17): 1714017, 网络出版: 2023-09-01  

基于太赫兹超材料的牛血清白蛋白传感器研究 下载: 506次

Research of Bovine Serum Albumin Sensor Based on Terahertz Metamaterials
作者单位
1 中国科学院上海光学精密机械研究所强场激光物理国家重点实验室,上海 201800
2 华中科技大学光学与电子信息学院,湖北 武汉 430074
3 上海理工大学光电信息与计算机工程学院,上海 200093
4 中国科学院大学材料与光电研究中心,北京 100049
摘要
太赫兹波具有非电离、对非极性物质穿透性高、对氢键等弱共振敏感等特性,是生物、材料、化学等领域的重要研究对象。蛋白质、糖类等生物大分子的转动频率和基团的振动频率以及分子之间弱相互作用的特征频率恰好处于太赫兹频段,这赋予了太赫兹光谱技术在生物医学领域中极大的发展潜力。然而,由于待测物尺寸一般小于太赫兹波长(0.03~3.00 mm),微量的待测物难以引起谱线的改变,太赫兹光谱检测灵敏度较低。能够灵活操控电磁波特性的超材料为解决上述问题提供了新的思路,通过设计不同的结构及参数,能够得到谐振频率位于太赫兹波段的超材料,微量的待测物即可引起谱线的明显变化。基于共振型太赫兹超材料构建了牛血清白蛋白(BSA)传感器,实验结果表明,当BSA溶液的体积质量为2.0~8.0 mg/mL时,传感器共振频率偏移量与溶液浓度呈线性关系,传感器的最低浓度检测限为0.3 mg/mL。
Abstract
Objective

Terahertz waves are electromagnetic waves with frequencies of 0.1-10.0 THz. They have the characteristics of wide bandwidth,strong penetration,and low photon energy. Notably,the energy levels of the terahertz spectrum correspond to the rotational and vibrational energy levels of several biological macromolecules. Therefore,the terahertz spectroscopy technology can be used to study the properties of biomolecules,such as their molecular structures and their molecular interactions with the surrounding environment. Because the wavelength of a terahertz wave (0.03-3.00 mm) is not in the same order of magnitude as the characteristic size of common biological macromolecules,it is difficult to produce sufficient interaction between the trace levels of biological macromolecules contained in the sample and the terahertz wave,and the weak change in the terahertz spectral line is difficult to capture. Metamaterial is an artificial material whose electromagnetic properties can be manipulated artificially. By combining terahertz spectroscopy technology with metamaterials,the small disturbance to the metamaterial caused by trace-level objects can result in significant changes in the spectra of metamaterials,and thus make high-sensitivity detection of biomacromolecules possible. In this study,a resonant terahertz metamaterial is used to enhance the interaction between terahertz wave and the determinand,and a bovine serum albumin (BSA) solution is selected as the analyte. An efficient BSA sensor is constructed using terahertz spectroscopy technology. The relationship between the concentration of the BSA solution and the resonance frequency offset of the sensor is analyzed,and the limit of detection of the sensor is examined.

Methods

To achieve rapid and highly sensitive detection of BSA solution,the unit structure designed by Sengupta et al. is adopted. Because of the C4 symmetry of the structure,the metamaterial-based sensor is insensitive to polarization. The electromagnetic properties of the metamaterial are simulated by full-wave numerical simulation. According to the simulation results,the above structure has resonance absorption near 0.8 THz. When the refractive index of the material at the surface of the metamaterial changes,the resonance frequency of the metamaterial shifts. By combining the terahertz spectrum technology,the relationship between the resonance frequency shift of the metamaterial and the concentration of determinand is established. The schematic of the experimental setup is shown in Fig. 1. First,the transmission spectrum of the metamaterial without a determinand is measured with a terahertz spectrometer and used as the background. Second,quantitative BSA is dissolved in distilled water to prepare a certain concentration of BSA solution,and the 20 μL solution is collected through a microsampler and dropped onto the metamaterial. The metamaterial is heated at 70 ℃ for 10 min. The transmission spectra of the metamaterials are measured using a terahertz spectrometer to provide a sample group. During the experiment,to reduce error,the linear weighted average processing is carried out on the data of the adjacent points in a single scanning. The final data for each sample is the average of the three scanning results. A second-order Gaussian fitting method is used to fit the transmission spectral data of the background and sample groups nonlinearly,and the resonance frequency shift of the metamaterial is obtained by comparing the fitted curves.

Results and Discussions

A resonance absorption peak of approximately 0.8 THz for the metamaterial without a determinand is found (Fig.2). According to the fitting curves,a BSA solution with a volume mass of 2 mg/mL can induce a 10.43-GHz redshift in the resonant frequency of the metamaterial. Using the control variable method,several groups of solutions with different volume mass values (2,3,4,and 8 mg/mL) are configured,and their terahertz transmission spectra are measured and compared with the transmission spectrum of the bare metamaterial (Fig.3). With a gradual increase in the concentration of the determinand,the resonance frequency of the metamaterial gradually moves in the lower frequency direction (Table 1). When the solution volume mass is in the range of 2-8 mg/mL,a linear relationship exists between the resonance frequency shift of the metamaterial and the volume mass of the determinand (Fig.4). The concentration of the BSA solution is determined according to a linear relationship. When the concentration of the BSA solution is reduced continuously and when the volume mass is decreased to 0.3 mg/mL,the frequency offset of the resonance chip is 0.87 GHz. When the volume mass is further decreased to 0.2 mg/mL,the resonance shift is less than 0.04 GHz,which is significantly lower than the sampling step size of the spectrometer (Fig.5 and Table 2). Furthermore,0.3 mg/mL exhibites the lowest detection limit. By optimizing the experimental environment,considering the change in transmittance and resonance frequency,and shortening the frequency step size,the detection sensitivity can be further improved,the limit of detection can be reduced,and the sensor specificity can be enhanced.

Conclusions

Based on metamaterials and terahertz spectroscopy, an efficient sensor for biological macromolecules is constructed. The experimental results show that the addition of determinand can cause a significant shift in the terahertz transmission spectrum and the variation in the resonant frequency of the sensor increases with an increase in the concentration of the determinand. When the volume mass of the BSA solution is in the range of 2-8 mg/mL, the offset of the resonant frequency is linearly correlated with the volume mass, demonstrating the potential of the proposed sensor for detecting the substance concentration. In addition, the limit of detection is 0.3 mg/mL. In conclusion, the proposed BSA sensor has high sensitivity, simple operation, and high efficiency. Subsequently, by further optimizing the materials and parameters of metamaterials, comprehensively utilizing the position and amplitude information of the resonance peak, and improving the test environment, it should be possible to obtain biological macromolecule sensors with higher specificity and sensitivity.

郑卓锐, 钟慧, 聂勇潇, 林婷, 方依霏, 宋立伟, 田野. 基于太赫兹超材料的牛血清白蛋白传感器研究[J]. 中国激光, 2023, 50(17): 1714017. Zhuorui Zheng, Hui Zhong, Yongxiao Nie, Ting Lin, Yifei Fang, Liwei Song, Ye Tian. Research of Bovine Serum Albumin Sensor Based on Terahertz Metamaterials[J]. Chinese Journal of Lasers, 2023, 50(17): 1714017.

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