Chinese Optics Letters,Issue 8, 2024,Editors’ Pick：

The chirality of small molecules is important in controlling physiological processes and indicating the health status of humans. Abnormal enantiomeric ratios of chiral molecules in biofluids and tissues occur in many diseases, including cancers and kidney and brain diseases. Moreover, in pharmaceutical industry, the chiral medicine molecules with different chirality are chalk and cheese that one may act as a drug and another can be inactive or even lead to serious side effects due to the different biological activities and toxicities, leading to urgent desire for the ability to discern chirality with high sensitivity and high speed.Recently, there are kinds of methods to detect chirality of molecule. The circular dichroism (CD) and optical rotation (OR) are utilized to distinguish chiral systems due to chiroptical effect (the different extinction coefficients and different phase velocities for left-handed and right-handed circularly polarized light). Meanwhile, high-performance liquid chromatography (HPLC) is characterized by chirality detection owing to chiral solid phase separation. However, these methods are hindered form biomolecular applications by low sensitivity for the chiroptical effect or the complexity and high-cost chiral columns of HPLC.

In order to address the aforementioned issues, Professor Chen Xianfeng and his team from the Shanghai Jiao Tong University designed a novel method of using double metal metal-cladding waveguide-cavity (DMWC) to detect chirality with higher resolution, easy preparation and low cost, due to the high sensitivity to the dielectric coefficient of the guided layer. To demonstrate the ability to distinguish chiral molecules, we monitored the real-time metabolism processing of two chiral drugs (methotrexate and amlodipine) in vitro and vivo, respectively. The experimental results showed excellent consistency with the theoretic results. The research results are published in Chinese Optics Letters, Vol. 22, Issue 8, 2024.

Fig. 1 Schematic of the double metal-cladding waveguide-cavity and the discerning process. (a), the double metal-cladding waveguide-cavity consists of a coupling layer, guide layer (containing cavity) and base layer. When chiral molecules with different chiralities are injected into the cavity, the reflected beam is altered. For example, the R-limonene molecules exhibit high reflectivity for left-handed circularly polarized lasers, while S-limonene exhibits high reflectivity for right-handed circularly polarized lasers. (b) Theoretical results of the difference in reflectivity.

Comparing results with current technology, our method possesses several advantage factors: (1) It provides a real-time chiral molecules discrimination method with higher resolution and low cost, which may have important implications for pharmacokinetics and pharmacodynamics and present new prospects for exploring biological processes. (2) The analysis of chiral molecular metabolic in vitro and vivo is achieved without complexed system, which is significant to disease monitoring and treatment due to the strong correlation between molecular chirality and pathological processes. (3) This method provides an important way to identification and detection of distinct chiral molecule for disease, evaluating disease progression and even the development of therapeutics by bio-photonics technology.

This research given the increasing importance of chirality detection in various fields such as pharmacodynamics, catalytic science, optoelectronics, and biomedical sciences. Meanwhile, this approach provides a new way to achieve important chiral discrimination for pharmacokinetics and pharmacodynamics and may present new opportunities in the detection of sophisticated structures in living organisms.

This work is published at “Qiheng Wei, Hongrui Shan, Xueqian Wang, Yi Lai, He Li, Hailang Dai*, and Xianfeng Chen*, Chirality discerning and monitoring in metal cladding optofluidic chip, Chinese Optics Letters, 22(8), (2024)”。

Link：https://opg.optica.org/col/abstract.cfm?uri=col-22-8-081202