RESUMEN
The high complexity of biological membranes has driven the development and application of a wide range of model membrane systems. Among these models, liposomes are extensively used because of their versatility in mimicking cellular membranes with a wide range of lipid compositions. However, the accurate quantification of lipid components, such as sterols, within these models remains a critical requirement for validation, data interpretation, and comparison. Here, we present a reliable and sensitive colorimetric assay using the Zak color reaction, which we have specifically adapted for the quantification of sterols at the micro-scale level. The assay was evaluated using cholesterol, ergosterol, and sitosterol standards, reflecting the diversity of sterol species across organisms. The reaction mechanism involves the dehydration of sterols to form carbonium ions, which are oxidized to form various enylic carbonium ions with specific absorption peaks. Due to the different chemical structures of cholesterol, ergosterol, and sitosterol, the resulting spectra show that the colored reaction products are formed in different proportions. The stability and interconversion of these species over time were analyzed. Cholesterol and sitosterol showed a clear peak at 555 nm, while ergosterol had prominent peaks at shorter wavelengths. Sterol assays on liposomal preparations showed accurate sterol incorporation with minimal loss during processing steps. These results demonstrate that this assay provides a robust and accurate measurement of sterol content in large unilamellar vesicles, making it a valuable tool for liposomal studies.
RESUMEN
Carbon-based nanomaterials have catalyzed breakthroughs across various scientific and engineering disciplines. The key to unlocking a new generation of tailor-made nanomaterials based on single-walled carbon nanotubes (SWCNTs) lies in the precise sorting of raw material into individual chiralities, each possessing unique properties. This can be achieved using conjugated polymer extraction (CPE), but to a very limited extent since the process generates only a few chirality-enriched suspensions. Therefore, it is imperative to comprehend the mechanism of the wrapping of SWCNTs by polymers to unleash CPE's full potential. However, the lack of a diverse palette of chirality-selective polymers with varying macromolecular parameters has hindered a comprehensive understanding of how the nature of the polymer affects the performance and selectivity of SWCNT isolation. To address this gap, multiple batches of such polymers are synthesized to elucidate the impact of molecular weight and dispersity on the purity and concentrations of the generated SWCNT suspensions. The obtained results explain the inconsistent outcomes reported in the literature, greatly improving the application potential of this promising SWCNT sorting approach. Concomitantly, the discovered significant influence of the macromolecular characteristics of conjugated polymers on the SWCNT isolation efficacy sheds considerable insight into the unresolved mechanism of this sorting technique.