# Novel sterol-spiropyran derivatives: synthesis and photoactivity in Langmuir monolayers

## TL;DR

Researchers created light-sensitive cholesterol-like molecules that can change the properties of lipid layers when exposed to light.

## Contribution

The paper introduces new sterol-spiropyran compounds that show light-induced changes in Langmuir monolayers.

## Key findings

- The compounds form stable and light-responsive Langmuir monolayers when mixed with lipids.
- Light-induced conformational changes in the spiropyran moiety significantly alter monolayer pressure-area isotherms.
- Monolayer response kinetics depend on compressional elasticity, suggesting potential for controlling complex lipid systems with light.

## Abstract

We describe the synthesis of novel sterol-spiropyran conjugates based on either cholesterol or ergosterol and designed to easily incorporate in lipid membranes. We demonstrate that these compounds, in mixtures with a lipid, form stable and light-responsive Langmuir monolayers on aqueous surfaces. Large differences in the monolayer pressure-area isotherms are observed upon light-induced conformational switch of the spiropyran moiety of the sterol-spiropyran compound in the monolayer. We present evidence that the kinetics of monolayer response to photoisomerisation is controlled by the monolayer compressional (dilatational) elasticity. The results suggest that these sterol-spiropyran conjugates would likely readily incorporate in more complex lipid systems such as bilayers and could provide a coupling mechanism to control their properties, lateral organisation and morphology by light.

The online version contains supplementary material available at 10.1038/s41598-026-39881-x.