Detection of Low-Concentration Biological Samples Based on a QBIC Terahertz Metamaterial Sensor.

Quasi-bound state in the continuum (QBIC) can effectively enhance the interaction of terahertz (THz) wave with matter due to the tunable high-Q property, which has a strong potential application in the detection of low-concentration biological samples in the THz band. In this paper, a novel THz metamaterial sensor with a double-chain-separated resonant cavity structure based on QBIC is designed and fabricated. The process of excitation of the QBIC mode is verified and the structural parameters are optimized after considering the ohmic loss by simulations. The simulated refractive index sensitivity of the sensor is up to 544 GHz/RIU, much higher than those of recently reported THz metamaterial sensors. The sensitivity of the proposed metamaterial sensor is confirmed in an experiment by detecting low-concentration lithium citrate (LC) and bovine serum albumin (BSA) solutions. The limits of detection (LoDs) are obtained to be 0.0025 mg/mL (12 µM) for LC and 0.03125 mg/mL (0.47 µM) for BSA, respectively, both of which excel over most of the reported results in previous studies. These results indicate that the proposed THz metamaterial sensor has excellent sensing performances and can well be applied to the detection of low-concentration biological samples.

Effects of SpsNAC042 transgenic Populus hopeiensis on root development, leaf morphology and stress resistance.

To identify the function of the SpsNAC042 gene and its response to salt and drought stress, the SpsNAC042 gene was transformed into Populus hopeiensis by the Agrobacterium-mediated leaf disc method, and the phenotypic, physiological changes and related genes expression of transgenic lines were analyzed. The results showed that the number and length of roots of transgenic lines increased significantly. The leaves of transgenic lines curled inward. Under salt and simulated drought stress, the transgenic lines showed improved tolerance to salt and drought. The activities of SOD, POD, CAT and proline content in the transgenic lines were significantly increased, and the reduction rates of total chlorophyll and MDA content were significantly decreased, which indicated that the transgenic lines showed strong physiological responses under stress. Meanwhile, the gene expression of MPK6, SOS1, HKT1 and P5CS1 were significantly upregulated, and the gene expression of PRODH1 was significantly downregulated, which preliminarily verified the stress regulation mechanism that SpsNAC042 might activate. The above results showed that the SpsNAC042 gene could promote root development, make leaf morphology curl, and enhance P. hopeiensis tolerance to stress.

Spectral filtering method for improvement of detection accuracy of Mg, Cu, Mn and Cr elements in aluminum alloys using femtosecond LIBS.

In this work, magnesium (Mg), copper (Cu), manganese (Mn) and chromium (Cr) in aluminum alloy samples were quantified by femtosecond laser-induced breakdown spectroscopy (fs-LIBS). The different parameters affecting the experimental results, including the laser pulse energy, moving speed of the 2D platform and spectral average number were optimized. The background signal preprocessing methods of median filtering (MF corrected) and Savitzky-Golay filtering (SG corrected) algorithms were used and the effect of the LIBS spectral analysis in the experiment investigated. The calibration curves of Mg, Cu, Mn and Cr elements were established separately and their corresponding detection limits (LODs) were calculated. After background correction, the LODs of Mg, Cu, Mn and Cr elements in MF corrected were 54.52, 11.69, 7.33 and 27.72 ppm, and in SG corrected were 59.15, 17.48, 14.75 and 31.97 ppm. The LODs of these elements in MF corrected and SG corrected have 1.4-5.2 and 1.2-2.5 improvement factors compared to those obtained using the fs-LIBS technique. This work demonstrates that background signal preprocessing methods are very helpful for improving analytical sensitivity and accuracy in quantitative analyses of aluminum alloys.

Terahertz spectroscopy detection of zinc citrate in flour and milk powder mixtures.

Zinc citrate (ZC) has been widely used in food as an important nutritional supplement. Accurate detection of ZC in food is important for health and safety. In this study, THz time-domain spectroscopy (THz-TDS) is used to quantitatively detect ZC in flour and milk powder mixtures. In our research, 15 different contents of ZC in flour and milk powder mixtures were prepared and measured by THz-TDS. A partial least squares (PLS) model was established based on the quantitative analysis of the absorption coefficient data of these two mixtures at 0.5-3.0 THz. The R2 and rms error (RMSE) given by the PLS model prediction were, respectively, 0.999 and 0.14% ZC in flour and 0.999 and 0.20% ZC in milk mixtures, indicating the predictions of the PLS model are in excellent agreement with the experimental measurements. The results show that combining THz-TDS with the PLS model can be used for accurate, quantitative analyses of ZC in food mixtures.

Terahertz Metamaterial Sensor for Sensitive Detection of Citrate Salt Solutions.

Citrate salts (CSs), as one type of organic salts, have been widely used in the food and pharmaceutical industries. Accurate and quantitative detection of CSs in food and medicine is very important for health and safety. In this study, an asymmetric double-opening ring metamaterial sensor is designed, fabricated, and used to detect citrate salts combined with THz spectroscopy. Factors that influence the sensitivity of the metamaterial sensor including the opening positions and the arrangement of the metal opening ring unit, the refraction index and the thickness of the analyte deposited on the metamaterial sensor were analyzed and discussed from electromagnetic simulations and THz spectroscopy measurements. Based on the high sensitivity of the metamaterial sensor to the refractive index of the analyte, six different citrate salt solutions with low concentrations were well identified. Therefore, THz spectroscopy combined with a metamaterials sensor can provide a new, rapid, and accurate detection of citrate salts.

Terahertz spectroscopy of citrate Salts: Effects of crystalline state and crystallization water.

Citrate salts are widely used as food additives and medicines for health and treatment. Accurate and fast detection of citrate salts is most important in food industry and medicine health. In this work, terahertz (THz) time-domain spectroscopy was used to detect and analyze different citrate salts and differentiate their crystalline hydrates. Effects of the crystalline state, the crystallization water and the metal cation on the THz spectra of citrate salts were investigated. Results indicate the crystalline states of the citrate salt samples strongly influence their THz featuring absorption peaks and citrate salts with crystallization water have larger absorption coefficients at the same frequency and higher possibility of existing featuring absorption peaks in comparison with citrate salts without crystallization water. Size of the metal cation also influences the THz absorption peak of the citrate salt and a small cation radius results in a large absorption peak frequency. This work illustrates the terahertz spectroscopy can be well used as a new technique to detect the citrate salts and differentiate their crystalline hydrates.

Terahertz spectroscopy detection of lithium citrate tetrahydrate and its dehydration kinetics.

Lithium citrate (LC) as a common food additive and also a psychiatric drug, usually in the form of tetrahydrate can gradually lose its crystalline water and convert into LC anhydrate at temperatures higher than the room temperature. In order to quickly distinguish the tetrahydrate from the anhydrate and to study the dehydration kinetics of the LC hydrates under the influence of the temperature, terahertz time-domain spectroscopy (THz-TDS) is utilized in this work. Experimental results show that the LC tetrahydrate at room temperature has an obvious absorption peak around 1.66 THz, while the LC anhydrate has no absorption peak at 0.5-3.0 THz. The absorption peak intensity of the LC tetrahydrate decreases continuously upon heating from 25 to 100 °C. Based on the normalized absorption peak area of the LC tetrahydrate around 1.66 THz, variation of its dehydration rate with the heating temperature is investigated and their relationship is fitted by the Arrhenius equation. The reaction activation energy of the LC tetrahydrate is derived to be 495.1 ±â€¯17.8 J/g with a deviation of about 3.7% from the traditional difference scanning calorimetry (DSC) measurement. These results indicate that THz-TDS can provide an efficient method to detect crystalline hydrates and can be applied to study the dehydration kinetics of crystalline hydrates with advantages of being fast, label-free and accurate.

LASP1 Induces Epithelial-Mesenchymal Transition in Lung Cancer through the TGF-ß1/Smad/Snail Pathway.

Background: LIM and SH3 domain protein 1 (LASP1), highly expressed in a variety of tumors, is considered as a novel tumor metastasis biomarker. However, it is unknown which signaling pathway works and how the signal transduces into cell nucleus to drive tumor progression by LASP1. The aim of this study is to explore the essential role of LASP1 in TGF-ß1-induced epithelial-mesenchymal transition (EMT) in lung cancer cells. Methods: The gene and protein levels of LASP-1 were successfully silenced or overexpressed by LASP-1 shRNA lentivirus or pcDNA in TGF-ß1-treated lung cancer cell lines, respectively. Then, the cells were developed EMT by TGF-ß1. The cell abilities of invasion, migration, and proliferation were measured using Transwell invasion assay, wound healing assay, and MTT assay, respectively. Western blotting was used to observe the protein levels of EMT-associated molecules, including N-cadherin, vimentin, and E-cadherin, and the key molecules in the TGF-ß1/Smad/Snail signaling pathway, including pSmad2 and Smad2, pSmad3 and Smad3, and Smad7 in cell lysates, as well as Snail1, pSmad2, and pSmad3 in the nucleus. Results: TGF-ß1 induced higher LASP1 expression. LASP1 silence and overexpression blunted or promoted cell invasion, migration, and proliferation upon TGF-ß1 stimulation. LASP1 also regulated the expression of vimentin, N-cadherin, and E-cadherin in TGF-ß1-treated cells. Activity of key Smad proteins (pSmad2 and pSmad3) and protein level of Smad7 were markedly regulated through LASP1. Furthermore, LASP1 affected the nuclear localizations of pSmad2, pSmad3, and Snail1. Conclusion: This study reveals that LASP1 regulates the TGF-ß1/Smad/Snail signaling pathway and EMT markers and features, involving in key signal molecules and their nuclear levels. Therefore, LASP1 might be a drug target in lung cancer.

GTSE1 Facilitates the Malignant Phenotype of Lung Cancer Cells via Activating AKT/mTOR Signaling.

The expression of G2 and S phase-expressed-1 (GTSE1) was upregulated in human cancer. However, its expression and roles in lung cancer have not been identified yet. In our study, we reported that GTSE1 expression was statistically higher in lung tissues than in the adjacent noncancerous tissues which might be a consequence of hypomethylation of the GTSE1 promoter. The upregulated expression of GTSE1 mRNA predicted the poorer survival of the lung patients. Ectopic expression of GTSE1 in lung cancer cells significantly increased while knockdown of GTSE1 decreased cell proliferation, cell migration, and cell invasion in H460 and A549 cells. Furthermore, knockdown of GTSE1 regulated the cell cycle and promoted cell apoptosis in H460 and A549 cells. Finally, we presented that GTSE1 was able to activate AKT/mTOR signaling in H460 and A549 cells. In conclusion, these results indicated that the overexpressed GTSE1 was involved in the progress of lung cancer by promoting proliferation migration and invasion and inhibiting apoptosis of lung cancer cells via activating AKT/mTOR signaling.

Struvite-type AMgPO4·6H2O (A = NH4, K): Two Natural Deep-Ultraviolet Transparent Nonlinear Optical Crystals.

Deep-ultraviolet (DUV) nonlinear optical (NLO) materials play vital roles in diverse fields. Unfortunately, only the KBe2BO3F2 crystal has found commercial applications so far. Therefore, the discovery of new DUV NLO crystals is still urgent. As we all know, digging into the properties of existing crystals is also an effective way to obtain new NLO crystals. Herein, two natural asymmetric orthophosphates AMgPO4·6H2O (A = NH4, K) are proposed. Although their structures and some properties such as infrared spectra, thermal properties, and dielectric properties have been previously characterized, their NLO properties have not been reported. Thus, in this work, these two natural DUV transparent orthophosphates NH4MgPO4·6H2O (NMP) and KMgPO4·6H2O (KMP) were successfully acquired by a simple slow evaporation method. The single-crystal X-ray diffraction data indicate that NMP and KMP are isomorphic and that both belong to the Pmn21 space group of the orthorhombic system. Remarkably, NMP and KMP possess short cutoff edges below 190 nm, and their second-harmonic generation (SHG) efficiencies are 0.62 and 0.80 times that of KH2PO4(KDP), respectively; furthermore, they can achieve type-I phase matching at 1064 nm.

hsa_circ_0058357 acts as a ceRNA to promote non­small cell lung cancer progression via the hsa­miR­24­3p/AVL9 axis.

Abnormal circular RNAs (circRNAs) are associated with biological processes in cancer; however, the function of circRNAs remains largely unknown in non­small cell lung cancer (NSCLC). The present study aimed to investigate the role of hsa_circ_0058357 on the progression of NSCLC. Cell proliferation, migration and apoptosis were determined using Cell Counting Kit­8, Transwell and flow cytometry assays, respectively. Gene [circRNA and microRNA (miR)] and protein expression levels were determined via reverse transcription­quantitative PCR and immunoblotting. A luciferase assay was employed to detect the binding of miR­24­3p with AVL9 cell migration associated (AVL9), while a cancer xenograft model was established to evaluate cancer growth in vivo. The results demonstrated that hsa_circ_0058357 was highly expressed in human NSCLC tissues and NSCLC cells compared with para­cancerous tissues and human bronchial epithelial (HBE) cells, respectively. Knockdown of hsa_circ_0058357 significantly suppressed cell viability, migration and tumor growth, while it promoted apoptosis in NSCLC cells. As a competing endogenous RNA, hsa_circ_0058357 knockdown contributed to the increase of miR­24­3p expression in NSCLC cells. Of note, overexpression of miR­24­3p markedly abolished the exogenous hsa_circ_0058357­induced excessive proliferation, migration and apoptosis resistance of NSCLC cells. Mechanistically, as a signaling molecule in late secretory pathway, AVL9 was also expressed at a high level in NSCLC tissues and cells, which could be directly suppressed by miR­24­3p. In the tumor tissues, along with growth inhibition, hsa_circ_0058357 knockdown also mediated the elevation of miR­24­3p and the reduction of AVL9. Thus, it was suggested that hsa_circ_0058357 may be a crucial regulation factor in NSCLC by sponging hsa­miR­24­3p, leading to a decrease in miR­24­3p expression, and subsequent increase in AVL9 expression. Therefore, hsa_circ_0058357 may serve as a potential target for diagnosis and gene therapy for NSCLC.

A first-principles study on the electronic and optical properties of a type-II C2N/g-ZnO van der Waals heterostructure.

The structural, electronic and optical properties of a new van der Waals heterostructure, C2N/g-ZnO, composed of C2N and g-ZnO monolayers with an intrinsic type-II band alignment and a direct bandgap of 0.89 eV at the Γ point, are extensively studied using first-principles density functional theory calculations. The results indicate that the special optoelectronic properties of the constructed heterostructure mainly originate from the interlayer coupling and electron transfer between the C2N and g-ZnO monolayers, and the photogenerated electrons and holes are located on the C2N and g-ZnO layers, respectively, which reduces the recombination probability of the electron-hole pairs. According to Bader charge analysis, there are 0.029 electrons transferred from g-ZnO to C2N to form a built-in electric field of ∼9.5 eV at the interface. Furthermore, the tunability of the electronic properties of the C2N/g-ZnO heterostructure under vertical strain and electric field is explored. Under different strains, the type-II band alignment properties of the heterostructure are retained and the vertical compressive strain has a greater influence on the bandgap modulation than the vertical stretching strain. The implemented electric field also does not change the type-II band alignment but changes the bandgap of the heterostructure from 1.30 to 0.58 eV when the electric field strength varies from -0.6 to 0.6 V Å-1. In addition, the absorption spectrum of the C2N/g-ZnO heterostructure under solar light is also studied. The absorption range of the heterostructure varies from the ultraviolet to near-infrared region with the absorption intensity in the order of 105 cm-1. All of these studies indicate that the C2N/g-ZnO heterostructure has excellent electronic and optical properties and promising applications in nanoelectronics and optoelectronics.

Study of Thermal Expansion Coefficient of Graphene via Raman Micro-Spectroscopy: Revisited.

The thermal expansion coefficient (TEC) of a 2D material is a fundamental parameter for both material property and applications. A joint study is hereby reported, using Raman microspectroscopy and molecular dynamics (MD) simulations, of the substrate effects on thermal properties of graphene. It is found that besides the lateral strain induced by the substrate, out-of-plane coupling strongly affects the temperature-dependent vibrational modes and TEC of graphene. MD simulation shows significant reduction of the density of states for longer wavelength out-of-plane vibrations when the graphene is supported on an alkane substrate. The negative TEC of freestanding graphene becomes smaller when out-of-plane rippling is suppressed. In order to measure TEC of 2D materials with the out-of-plane coupling being taken into consideration, a Raman microspectroscopic scheme to separate the contributions of lateral strain and out-of-plane coupling to TEC is developed. The TEC of graphene on octadecyltrichlorosilane substrate is found to be (-0.6 ± 0.5) × 10-6 K-1 at room temperature, which is fundamentally smaller than that of freestanding graphene. These results shed light on the fundamental understanding of the interaction between 2D material and substrate, and offer a general recipe for studying separately in-plane and out-of-plane couplings on supported materials.

Incidence, severity and tolerability of pneumothorax following low-dose CT-guided lung biopsy in different severities of COPD.

BACKGROUND: The feasibility of pneumothorax following low-dose CT-guided puncture lung biopsy in different severities of COPD has not been reported. METHODS: The data of the patients with pulmonary lesion who underwent low-dose CT-guided lung biopsy by one experienced operator in our hospital from January 1st to September 30th in 2019 were retrospectively collected. They were divided into COPD group and non-COPD group. The risk factors, incidence and severity of pneumothorax with the severity of COPD and changes in MMRC score, treatment way and discharge time after pneumothorax were assessed. RESULTS: Two hundred and nineteen patients were retrospectively enrolled in this study with 64 in the COPD group and 155 in the non-COPD group. The average age, MMRC score and the incidence of pneumothorax after biopsy were significantly higher in the COPD group (64.7 ± 1.27 years, 1.02 ± 0.13, 31.3%) than in the non-COPD group (58.8 ± 1.16 years, 0.35 ± 0.06, 17.4%, P < 0.05). The incidence of pneumothorax between I-II and III-IV in COPD did not reach the significant difference (P = 0.863). COPD was the only independent risk factor for pneumothorax after biopsy in a multivariable regression (P < 0.05). MMRC score was significantly increased at post-pneumothorax in the two groups (P < 0.001). There was no significant difference in diagnostic rate, severity of pneumothorax, the proportion of delayed pneumothorax, the changes in treatment way and discharge time between the two groups (P > 0.05). CONCLUSION: Although the incidence of pneumothorax after low dose CT-guided lung biopsy is increased in COPD, there was no difference in the severity of pneumothorax amongst the different severities of COPD and it is well-tolerated without increasing medical burden.

Detection of gene mutation responsible for Huntington's disease by terahertz attenuated total reflection microfluidic spectroscopy.

Terahertz absorption spectroscopy based on attenuated total reflection (ATR) from a microfluidic sample cell was designed and implemented to detect gene mutations leading to Huntington's disease (HD). The self-developed compact ATR microfluidic system was employed to detect two groups of base-repeated DNA molecules combined with a terahertz time-domain spectrometer in a marker-free manner. The first group featured different repetition patterns of oligonucleotide fragments, and the second group included the HD gene. For the oligonucleotides of different repetition patterns, there were significant differences among the three oligonucleotides with three repeats of the double bases, which could be unambiguously classified and identified; For the HD gene, it was found that the magnitude of the terahertz absorption coefficients of the four oligonucleotide solutions was, in ascending order, CAG-4 < CAG-16 < CAG-32 < CAG-40 (the numbers are the repeat times of the CAG base segment, with 40 repeats belonging to the HD gene), when the concentration of oligonucleotide was 1 mg/mL. Principal component analysis result indicated that the spectral differences of the four oligonucleotide solutions with different CAG repeat times were statistically significant and clearly distinguishable. These results demonstrate the potential of terahertz spectroscopy as a noninvasive, unmarked, fast and low-cost assay for gene diagnosis and clinical disease detection.

FKBP4 Accelerates Malignant Progression of Non-Small-Cell Lung Cancer by Activating the Akt/mTOR Signaling Pathway.

OBJECTIVE: To study the expression, biological function, and mechanism of FKBP4 in non-small-cell lung cancer (NSCLC). METHODS: First of all, the expression of FKBP4 in NSCLC tissues and cell lines was detected by qRT-PCR; then, the effects of FKBP4 on proliferation, apoptosis, migration, and invasion of NSCLC were studied by CCK-8 assays, flow cytometry assays, wound-healing assays, and Transwell assays. After that, tumor xenografts were used to explore the effect of FKBP4 on NSCLC tumor growth in vivo, and the phosphorylation of Akt and mTOR was measured by western blot. RESULTS: FKBP4 was highly expressed in NSCLC tissues and cells, and its expression was closely related to NSCLC tumor size, lymph node metastasis, and patient prognosis. In vitro, FKBP4 can promote NSCLC cell proliferation, migration, and invasion and inhibit NSCLC cell apoptosis. In vivo, FKBP4 can promote NSCLC tumor growth. Furthermore, FKBP4 can promote Akt and mTOR phosphorylation and activate the Akt/mTOR signaling pathway and an mTOR inhibitor can neutralize the functions of FKBP4 in NSCLC cells. CONCLUSION: FKBP4 serves as an oncogene to promote malignant processes in NSCLC, and it has the potential to be used as a biological marker and therapeutic target for NSCLC.

Detection of single-base mutation of DNA oligonucleotides with different lengths by terahertz attenuated total reflection microfluidic cell.

Many human genetic diseases are caused by single-base mutation in the gene sequence. Since DNA molecules with single-base mutation are extremely difficult to differentiate, existing detection methods are invariably complex and time-consuming. We propose a new label-free and fast terahertz (THz) spectroscopic technique based on a home-made terahertz attenuated total reflection (ATR) microfluidic cell and a terahertz time-domain spectroscopy (THz-TDS) system to detect single-base-mutated DNA molecules. The detected object DNA molecules are normal hemoglobin gene, sickle cell anemia gene (15 nt), JAK2 gene wild type and JAK2 V617F gene mutation (39 nt) from sickle cell anemia and thrombocytopenia, respectively. Results show that the oligonucleotide fragments with single-base mutation can be identified by THz spectroscopy combined with the ATR microfluidic cell, and the recognition effect of short oligonucleotide fragments with single-base mutation is better than that of long oligonucleotide fragments. The terahertz biosensor is shown to have high sensitivity and can be used to detect DNA molecules directly in the solution environment.

Image fusion based on multiscale transform and sparse representation to enhance terahertz images.

High-quality terahertz (THz) images are vital to integrated circuit (IC) manufacturing. Due to the unique sensitivity of THz waves to different materials, the images obtained from the point-spread function (PSF) model have fewer image details and less texture information in some frequency bands. This paper presents an image fusion technique to enhance the resolution of THz IC images. The source images obtained from the PSF model are processed by a fusion method combining a multiscale transform (MST) and sparse representation (SR). The low-pass band is handled by sparse representation, and the high-pass band is fused by the conventional "max-absolute" rule. From both objective and visual perspectives, four popular multiscale transforms-the Laplacian pyramid, the ratio of low-pass pyramids, the dual-tree complex wavelet transform and the curvelet transform-are thoroughly compared at different decomposition levels ranging from one to four. This work demonstrates the feasibility of using image fusion to enhance the resolution of THz IC images.

Photoacoustic imaging of microenvironmental changes in facial cupping therapy.

As a traditional medicine practice, cupping therapy has been widely used to relieve symptoms like fatigue, tension, and muscle pain. During the therapy, negative pressure is applied to the skin for a while with an intention to enhance blood circulation or induce micro-bleeding. The therapeutic effect, however, is not clear due to the lack of direct quantification. Aiming at a quantitative assessment of the treatment effect, we explore optical-resolution photoacoustic microscopy (OR-PAM) in monitoring the structural and functional changes after cupping. We find that, after 5-minutes of ∼ 20 kPa negative pressure cupping, more capillaries appear in the focus, and micro-blooding is observed from the capillaries. We quantify the images and find the blood vessel density is increased by 64%, and the total hemoglobin concentration in both the veins and the arteries exhibits 62% and 40% elevation, respectively. Oxygen saturation in the vein and artery decreased by 17% and 3% right after cupping, respectively. After two hours of recovery, the three blood-related parameters return to their original levels, indicating that the effects in the tissue last only a short period after cupping at the given pressure and time duration. Note that no significant cupping marks are induced with the treatment parameters in this study. This work proposes OR-PAM to quantitatively monitor and evaluate the effect of cupping therapy from the perspective of imaging. The method is also useful for accurate control of the therapeutic outcome.

An Optically Tunable THz Modulator Based on Nanostructures of Silicon Substrates.

Nanostructures can induce light multireflection, enabling strong light absorption and efficient photocarrier generation. In this work, silicon nanostructures, including nanocylinders, nanotips, and nanoholes, were proposed as all-optical broadband THz modulators. The modulation properties of these modulators were simulated and compared with finite element method calculations. It is interesting to note that the light reflectance values from all nanostructure were greatly suppressed, showing values of 26.22%, 21.04%, and 0.63% for nanocylinder, nanohole, and nanotip structures, respectively, at 2 THz. The calculated results show that under 808 nm illumination light, the best modulation performance is achieved in the nanotip modulator, which displays a modulation depth of 91.63% with a pumping power of 60 mW/mm2 at 2 THz. However, under shorter illumination wavelengths, such as 532 nm, the modulation performance for all modulators deteriorates and the best performance is found with the nanohole-based modulator rather than the nanotip-based one. To further clarify the effects of the nanostructure and wavelength on the THz modulation, a graded index layer model was established and the simulation results were explained. This work may provide a further theoretical guide for the design of optically tunable broadband THz modulators.