Chiral Sensing of Amino Acids under Visible Light via Hydroxypropyl Cellulose Gels

The identification of Chiral molecules is essential in pharmaceutical and food science. However, conventional methods are complex and cost-prohibitive. This study introduces a sustainable method using hydroxypropyl cellulose (HPC) gel to identify amino acids enantiomers, such as phenylalanine and alanine, through visible light. By integrating the structural color properties of HPC, this research demonstrates the HPC gel's capability to distinguish L (Levo)-phenylalanine (L-Phe), D (Dextro)-phenylalanine (D-Phe), and DL (racemic mixture)-phenylalanine (DL-Phe) supplemented with visible circular dichroism (CD) spectra or hydrochloric acid (HCl) as visual indicators. Similar chiral sensing results are observed with D-alanine, L-alanine, and DL-alanine. Unlike traditional UV-based detection requiring expensive equipment, this approach simplifies the process while maintaining sensitivity. Varying phenylalanine concentrations altered the CD response without disrupting the gel's helical structure, and color changes in response to HCl addition facilitated visual identification of enantiomers. Furthermore, adding various salts generates colorful HPC/Phe gels, demonstrating their suitability for 3D printing. Meanwhile, the HPC gels remained functional for three months, indicating long-term stability. These advancements are significant for pharmaceutical and biotechnological industries, facilitating efficient low-concentration chirality detection (0.2 wt.%). Continued development and refinement of this technology are expected to expand its applications and improve analytical capabilities for future chirality-related studies and photonic gel 3D printing.