Using terahertz spectroscopy to quantify bioactive flavonoids in Moxa Wool as predictor of rheumatoid arthritis treatment outcomes

BACKGROUND

Moxibustion, a traditional Chinese medicine practice, employs Moxa Wool, derived from Artemisia argyi. Flavonoids, the key pharmacological constituents in Moxa Wool, are known for their anti-inflammatory and analgesic properties. The purity of Moxa Wool, particularly its flavonoid content, directly influences the efficacy of moxibustion treatments. However, quantifying these bioactive flavonoids accurately and non-destructively has been a challenge.

PURPOSE

This study introduces terahertz spectroscopy as a non-destructive optical detection method for qualitative detection and quantitative analysis of flavonoids in Moxa Wool. By establishing a mathematical model between spectral signals and clinical efficacy, a reliable correlation between flavonoid concentration and the therapeutic effect of moxibustion can be established, providing a potential predictive model for the treatment outcomes of rheumatoid arthritis.

STUDY DESIGN

We adopted terahertz spectroscopy technology and combined it with terahertz metamaterial biosensors to achieve rapid, efficient, and non-destructive testing of the quality of Moxa Wool. This method reduces the detection time from hours to minutes while lowering the sample detection limit, overcoming the limitations of traditional detection methods in pharmacological research.

METHODS

Through terahertz metamaterial biosensors, rapid detection of the purity of Moxa Wool has been achieved. A combination of molecular simulation and terahertz spectroscopy was used to quantitatively analyze the flavonoid content in different purities of Moxa Wool. To ensure accuracy, the quantitative results of flavonoids obtained by terahertz spectroscopy were validated using high-performance liquid chromatography (HPLC). In addition, moxibustion treatment was performed on rats with rheumatoid arthritis using Moxa Wool, and medical indicator information was recorded. A mathematical analysis model was established to evaluate the correlation between flavonoid content and analgesic and anti-inflammatory effects.

RESULTS

Terahertz spectroscopy analysis shows that there is a direct correlation between the flavonoid content in moxibustion and the absorption peak intensity. The maximum R2 in the model analysis is 0.98, indicating a high accuracy in predicting the purity of Moxa Wool. These results were also validated by HPLC. In a rat model, the purity of 30:1 Moxa Wool samples showed a 50 % decrease in TNF-α, IL-1β, and IL-6 levels during treatment compared to low-purity samples, significantly reducing inflammation markers and pain symptoms. Meanwhile, The PLS prediction model established a correlation between terahertz-detected flavonoid levels and treatment outcomes (PWL and IL-1β). The maximum R2 in the model is 0.91, indicating a high correlation between flavonoid levels and the anti-inflammatory and analgesic effects of moxibustion treatment.

CONCLUSION

This study not only demonstrates the effectiveness of terahertz spectroscopy in the pharmacological quantification of bioactive compounds but also establishes a novel predictive model for the efficacy of moxibustion in rheumatoid arthritis treatment. It underscores the potential of integrating traditional medicine insights with advanced technology to enhance therapeutic strategies in pharmacology.

Fabrication and Enzymatic Disorganization of Multiresponse Worm-Like Micelles

How to fabricate multiresponse worm-like micelles (WLMs) and the corresponding green disposal is still challenging. A strategy of fabricating the surfactant-based WLMs that can respond simultaneously to light, heat, and pH was developed by using triple-response sodium (E)-2-(4-(phenyldiazenyl)phenoxy) acetate (AzoNa) and butyrylcholinesterase (BChE)-hydrolyzable palmitoylcholine bromide (PCB). Under the optimal molar ratio of AzoNa to PCB (∼0.5), the PCB-AzoNa WLMs formed with a maximum zero-shear viscosity (η0) value of about 2.1 × 105 mPa·s and an average diameter (D) of 4.1 ± 0.6 nm under conditions of 37 °C and pH 7.4. After irradiated with 365 nm UV light for 80 min, AzoNa underwent the trans-to-cis transition, by which the PCB-AzoNa WLMs was destroyed; however, the PCB-AzoNa WLMs could be reformed upon the irradiation of 455 nm blue light for 18 h or heating at 70 °C for 45 min due to the cis-to-trans isomerization of AzoNa. When pH changed from 7.4 to 2.0, the PCB-AzoNa WLMs was destroyed rapidly because of the conversion of AzoNa to the acid form of AzoH, whereas the PCB-AzoNa WLMs could be reformed after pH was restored to 7.4. The multiple responsiveness of the PCB-AzoNa WLMs was reversible due to the reversible trans-cis isomerization or protonation of AzoNa. Besides, the average D values of light, heat, and pH-regenerated PCB-AzoNa WLMs were 4.2 ± 0.7, 4.0 ± 0.7, and 4.0 ± 0.6 nm, respectively. Finally, the PCB-AzoNa WLMs could be enzymatically disorganized under conditions of 37 °C and pH 7.4 due to the BChE-catalyzed hydrolysis of PCB. We hope that the fabrication and enzymatic disorganization strategies for PCB-based multiresponse WLMs presented here will find potential applications in the formulation of antimicrobial household and personal care products containing PCB and in the green disposal of viscous waste containing PCB.

On the Effects of Different trans and cis Populations in Azobenzene Liquid Crystal Elastomers: A Monte Carlo Investigation

We investigate main-chain liquid crystal elastomers (LCEs) formed by photoresponsive azobenzene units with different populations of trans and cis conformers (from fully trans to fully cis). We study their macroscopic properties as well as their molecular organization using extensive Monte Carlo simulations of a simple coarse-grained model where the trans and cis conformers are represented by soft-core biaxial Gay-Berne particles with size and interaction energy parameters obtained by fitting a bare bone azobenzene moiety represented at atomistic level. We find that increasing the fraction of cis conformers, as could be obtained by near-UV irradiation, shifts the nematic-isotropic transition to a lower temperature, consistently with experiment, while generating internal stress in a clamped sample. An analysis of pair distributions shows that the immediate surroundings of a bent cis molecule are slightly less dense and more orientationally disordered in comparison with that of a trans conformer. Comparing nematic and smectic LCEs, actuation in the smectic phase proved less effective, disrupting the smectic layers to some extent but preserving orientational order of the azobenzene moieties.

Machine Learning Enhanced Optical Spectroscopy for Disease Detection

Optical spectroscopy plays an important role in disease detection. Improving the sensitivity and specificity of spectral detection has great importance in the development of accurate diagnosis. The development of artificial intelligence technology provides a great opportunity to improve the detection accuracy through machine learning methods. In this Perspective, we focus on the combination of machine learning methods with the optical spectroscopy methods widely used for disease detection, including absorbance, fluorescence, scattering, FTIR, terahertz, etc. By comparing the spectral analysis with different machine learning methods, we illustrate that the support vector machine and convolutional neural network are most effective, which have potential to further improve the classification accuracy to distinguish disease subtypes if these machine learning methods are used. This Perspective broadens the scope of optical spectroscopy enhanced by machine learning and will be useful for the development of disease detection.

Acid-catalysed liquid-to-solid transitioning of arylazoisoxazole photoswitches

Molecular photoswitches play a vital role in the development of responsive materials. These molecular building blocks are particularly attractive when multiple stimuli can be combined to bring about physical changes, sometimes leading to unexpected properties and functions. The arylazoisoxazole molecular switch was recently shown to be capable of efficient photoreversible solid-to-liquid phase transitions with application in photoswitchable surface adhesion. Here, we show that the arylazoisoxazole forms thermally stable and photoisomerisable protonated Z- and E-isomers in an apolar aprotic solvent when the pK a of the applied acid is sufficiently low. The tuning of isomerisation kinetics from days to seconds by the pK a of the acid not only opens up new reactivity in solution, but also the solid-state photoswitching of azoisoxazoles can be efficiently reversed with selected acid vapours, enabling acid-gated photoswitchable surface adhesion.

Probing lattice vibration of alkali halide crystals by broadband terahertz spectroscopy

Terahertz spectral features of alkali halide crystals were studied with the combination of broadband terahertz time-domain spectroscopy and the solid-state-based density functional theory calculations. To understand the particular modes of the observed terahertz features of the alkali halide crystals, the resonant modes of KCl and CsCl were analyzed using face-centered cubic and body-centered cubic lattice models, respectively. The results show that the characteristic terahertz absorption peaks could be assigned to the lattice vibration of the ionic crystals. Furthermore, the terahertz responses of a series of alkali halides were recorded, and obvious absorption peaks were observed in each salt in the frequency region below 8.5 THz. What is more interestingly is that the frequencies of these observed peaks are red-shifted with the increases of the mass and radius of the ions. This correlation between the resonant frequency of the lattice vibration, the reduced atomic mass, and the equilibrium distance between the ions agrees well with the harmonic oscillator model.

Application of terahertz spectroscopy on monitoring crystallization and isomerization of azobenzene

Terahertz spectroscopy provides a powerful and informative link between infrared spectroscopy and microwave spectroscopy, and is now beginning to make its transition from initial development to broader use by chemists, materials scientists and biologists. In this study, utilizing terahertz spectroscopy we monitored the crystallization and isomerization of azobenzene. In flash-frozen trans-azobenzene solutions, the processes of crystallization and phase transition were observed. A new phase has been experimentally confirmed to exist stably at low temperatures. The results on gradual-frozen experiment indicate that the formation of the observed new phase is determined by the cooling rate. Besides, based on the distinctive spectral features of the isomers, the thermal- and photo-induced isomerization processes of azobenzene were investigated. This work presents that the terahertz spectroscopy has a great potential to study the phase transitions and crystallization of liquid samples under different freezing conditions.

Measurement of the conformational switching of azobenzenes from the macro- to attomolar scale in self-assembled 2D and 3D nanostructures

We compare the cis–trans conformational switching of commercial azobenzene molecules in different chemical environments, ranging from isolated molecules in liquid to attomolar-2D and macro-scale 3D self-assembled structures.

Molecular methylation detection based on terahertz metamaterial technology

Terahertz wave has a good ability to identify biomolecules due to its fingerprint spectrum characteristics. However, the minimum detectable limit of terahertz technology by the conventional tablet pressing method is on the order of milligrams, which cannot meet the application requirements of low concentration detection in the biomedical field-near or below micrograms. Here, we proposed a method to enhance the detection sensitivity by designing a metamaterial chip with the absorption-induced transparency (AIT) effect, which can enhance the interaction between terahertz waves and biomolecules and lower the detectable limit. Taking 7-methylguanine (7-MG) as an example, based on its terahertz characteristic absorption peak, we designed a split-ring resonator (SRR) metamaterial chip, which has the advantages of high sensitivity, unlabeled detection, fast response and simple measurement. Its quantitative detection limit can reach 6.30 μg, which is about 500 times smaller than that of the traditional tablet pressing method (2.95 mg). In addition, for methylated and unmethylated substances, the chip exhibits different frequency shifts, which also realizes the qualitative identification effectively. These results provide a reference for the rapid and accurate diagnosis of diseases associated with molecular methylation in clinical medicine.

Analysis of Flavonoid Compounds by Terahertz Spectroscopy Combined with Chemometrics

Flavonoids are a large class of polyphenols widely distributed in plants in the free form or as glycosides, and they have antioxidation, antibacterial, antitumor growth, and other pharmacological effects. As an important active component of traditional Chinese medicine, they have high medicinal value and development prospects. In this work, the biomolecular properties of 10 common flavonoids, including baicalein, baicalin, apigenin, quercetin, naringenin, hesperetin, daidzein, genistein, puerarin, and gastrodin, are studied by terahertz time-domain spectroscopy (THz-TDS) in the range of 0.2-2.5 THz. The results reveal that these flavonoids have different characteristic absorption peaks in the terahertz band. Moreover, the terahertz absorption characteristics of samples in the temperature range of 78-320 K are studied. The results show that the characteristic absorption peaks gradually increase with the decrease in temperature, and the frequency position of the absorption peak has a slight blue shift. Furthermore, qualitative identification and quantitative analysis of flavonoids are carried out by terahertz spectra combined with chemometrics. Specifically, a series of mixtures of three flavonoids with similar molecular structures under various concentrations are analyzed. The partial least-squares regression (PLSR) model and the artificial neural network (ANN) model are applied to quantitatively analyze the ternary mixture. The results confirm that the ANN model obtains the best predicted value, with the root-mean-square errors in the prediction set (RMSEP) of 1.27% for daidzein. In summary, the biomolecular properties of flavonoids are studied by the THz-TDS technique, and a rapid, effective, and nondestructive method for qualitative identification and quantitative analysis of flavonoids is provided. The results demonstrate that this method has potential application value in the detection of Chinese herbal medicine and has better referential significance for the study of other biomolecules, especially for isomers or similar molecular structures.