Quantitative and Mathematical Estimation of Artificial Tears Viscosity Based on FTIR Spectroscopy

Source abstract

Viscosity plays a key role in determining the stability and effectiveness of ophthalmic drops. The proposed study aims to develop a mixed analytical methodology combining medical engineering and mathematical modeling techniques to estimate the concentrations and viscosities of nine different polymer formulations containing hyaluronic acid (HA), cellulose derivatives (HPMC, CMC), and cross-linked polymers. The study used Fourier transform infrared spectroscopy (FTIR) as a quantitative analysis tool, applying a data processing protocol that included water removal and linear baseline correction to ensure the accuracy of the readings. This spectral methodology is characterized by its ability to analyze polymers in a true steady state, preserving the integrity of the polymer chains without subjecting them to shear stress or rotational motion caused by conventional devices, which may lead to a temporary change in the arrangement of molecules. The results showed high efficiency for the external calibration model based on the measurement of net peak height, achieving a coefficient of determination of (R²) 0.837 with low root mean square error (RMSE) values, confirming the accuracy of the polymer concentration prediction. From a biophysical view, spectral data were integrated with the Huggins equation to estimate intrinsic viscosity, with the cross-linked sample (D9) showing the highest viscosity levels at 8.95 (mPa·s), consistent with reference standards. The significance of this study lies in providing an engineering model that allows for the adjustment of the rheological properties of eye solutions and the design of customized drug formulations that ensure maximum comfort and stability on the corneal surface, opening new possibilities for the quality of advanced tear substitute manufacturing.