Near-infrared investigations of novel anti-HIV tenofovir liposomes.

Near-infrared (NIR) approaches is considered one of the most well-studied process analyzers evolving from the process analytical technology initiatives. The objective of this study was to evaluate NIR spectroscopy and imaging to assess individual components within a novel tenofovir liposomal formulation. By varying stearylamine, as a positive charge imparting agent, five batches were prepared by the thin film method. Each formulation was characterized in terms of drug entrapment efficiency, release characteristics, particle sizing, and zeta potential. Drug excipients compatibility was tested using Fourier transform infrared spectroscopy, differential scanning calorimetry, and X-ray diffraction. The obtained results showed an increase in drug entrapment and a slower drug release by increasing the incorporated percentage of stearylamine. The compatibility testing revealed a significant interaction between the drug and some of the investigated excipients. The developed NIR calibration model was able to assess drug, phospholipid, and stearylamine levels along the batches. The calibration and prediction plots were linear with correlation coefficients of more than 0.9. The root square standard errors of calibration and prediction did not attain 5% of the measured values confirming the accuracy of the model. In contrast, NIR spectral imaging was capable of clearly distinguishing the different batches, both qualitatively and quantitatively. A linear relationship was obtained correlating the actual drug entrapped and the predicted values obtained from the partial least squares images.