New research could improve detection of chiral molecules in pharmaceuticals and biotechnology

New research led by Ohio University’s Distinguished Professor Alexander Govorov has introduced a groundbreaking method for detecting chiral molecules, potentially revolutionizing fields such as pharmaceuticals and biotechnology. Published in Science Advances, the study outlines a novel technique using spiral plasmonic metastructures to achieve ultra-sensitive detection of molecular chirality, often referred to as “handedness.” The collaborative effort involves researchers from Wuhan University in China and the Istituto Italiano di Tecnologia in Italy. Chirality is a fundamental property of many molecules, determining how they interact with light and biological systems. It plays a crucial role in biochemical processes and drug functionality, yet traditional methods for measuring chirality often yield weak signals, making detection challenging. This issue is especially relevant in pharmaceuticals, where only one form of a chiral molecule might be effective or safe, while its mirror image could be inert or toxic. Thalidomide, a notorious example, illustrates this danger, one enantiomer was therapeutic, while the other caused severe birth defects. The research team addressed these limitations by engineering specialized spiral gold plasmonic metastructures. These nanostructures amplify both electric and superchiral optical near fields, enhancing nonlinear optical processes, specifically circularly polarized second-harmonic generation. When chiral molecules interact with these surfaces, the resulting optical signal becomes significantly stronger, enabling detection at unprecedented sensitivity levels. According to the study, the platform achieved a detection limit of around 11 picomolar for adsorbed bovine serum albumin, a protein commonly used in biochemical assays. Additionally, the system demonstrated a figure of merit as high as 3,260 μM⁻¹, placing it among the most effective chiral plasmonic sensors reported to date. A notable advantage of this system is its ability to differentiate between enantiomers even when they exist together in a racemic mixture, without requiring prior separation through chromatography. In an interview, Govorov emphasized the significance of shifting from linear to nonlinear chiroptical sensing. Traditional methods, such as circular dichroism and optical rotatory dispersion spectroscopy, rely on linear responses, where the enhanced optical signal scales proportionally with the plasmonic electromagnetic enhancement factor. However, the nonlinear approach allows for a squared relationship, meaning the signal strength increases exponentially with the enhancement factor. This dramatic amplification enables the detection of chirality at extremely low concentrations, offering a substantial improvement over existing techniques. Looking ahead, the potential applications of this technology span multiple domains. In pharmaceuticals, it could facilitate rapid and accurate detection of chiral compounds during drug development and quality control, reducing the time and resources required for analysis. In biomedical settings, it might enable real-time monitoring of molecular interactions within complex biological matrices. Beyond healthcare, the technology could prove valuable in agricultural and environmental monitoring, as well as forensic science, where identifying specific molecular configurations is essential. The research team highlighted the possibility of integrating this technology into compact, on-chip platforms capable of operating in diverse environments, including aqueous solutions or biological media. Such adaptability would make the system suitable for point-of-care diagnostics and field-based testing, further broadening its impact. The findings represent a significant step forward in overcoming the challenges associated with detecting molecular chirality. By leveraging advanced nanophotonic materials and nonlinear optical phenomena, the study opens new avenues for developing more efficient and sensitive analytical tools. As the technology matures, it could lead to transformative changes in how scientists and industries analyze and utilize chiral molecules.