Computational Screening of Infrared Resonant Bands in Cholesterol Monohydrate for Selective Laser Lithotripsy of Cholesterol Gallstones

Abstract Cholelithiasis remains a common digestive disorder, with cholesterol gallstones accounting for the vast majority of cases. Current laser lithotripsy for cholesterol gallstones relies primarily on nonselective photothermal and photoacoustic effects, which do not fully exploit the crystallographic and molecular structural features of cholesterol monohydrate (CMH). To address this, we propose a frequency-screening framework based on photon-phonon resonant absorption (PPRA) for evaluating the CMH intermolecular hydrogen-bonded interface. Using a truncated cholesterol monohydrate (TCMH)model that preserves the core interlayer interaction network, we combined density functional theory (DFT) with atoms in molecules (AIM) topological analysis to characterize the localized interfacial O–H modes and their hydrogen-bond environments. Four interfacial O–H stretching modes at 3007, 3162, 3207, and 3272 cm–1 were retained based on their displacement patterns and relative infrared (IR) intensities. A water spectrum calculated at the same theoretical level was then used to characterize the relative water background. The static score, relative TCMH IR score, and low-water-background score were combined through an equal-exponent geometric mean. The four modes show different characteristics across these scores, indicating that candidate bands should be compared using multiple factors. The resulting scores provide a relative testing order of the candidate mid-infrared regions within the present model. They do not constitute an absolute TCMH-to-water absorption comparison.