Crystallisation is a critical step for structural analysis in fields such as pharmaceuticals and materials science. Traditional small molecule crystallisation methods often demand substantial amounts of material and lengthy crystallisation times, posing challenges for high-throughput applications. This study presents an innovative high-throughput crystallisation method for small molecules using polyethylene glycol (PEG) and crystallisation oils, which adapts techniques traditionally employed in protein crystallisation. The approach significantly enhances the efficiency and quality of crystallisation, making it suitable for subsequent analysis via X-ray crystallography or MicroED. This study leverages the unique properties of PEG and crystallisation oils to streamline the crystallisation process. PEG's versatility, with its range of molecular weights, allows for the fine-tuning of crystallisation conditions, enhancing nucleation and crystal growth. The use of crystallisation oils and PEG’S helps maintain stable environments, control evaporation/diffusion and contamination. The method successfully crystallised a variety of compounds, including pharmaceutical drugs, sugars, metal-organic frameworks (MOFs), inorganic complexes, and organic molecules.
The experimental process involved preparing crystallisation solutions by dissolving target small molecules in appropriate organic solvents and also creating a range of PEG and oil as reservoir solutions. These solutions were dispensed into 96-well crystallisation plates using the Mosquito liquid handler and the hanging drop method. The complete set-up takes under 2 minutes without requiring a wash step or the creation of a duplicate source plate. The use of automated nano liquid handler and imaging systems, specifically the Mosquito and ROCK IMAGER® by Formulatrix, allowed for efficient crystallisation plate set up, monitoring and optimisation of crystallisation conditions through high-resolution images using visible light, UV fluorescence, and cross-polarisation.
In conclusion, this high-throughput crystallisation method, utilising PEG, crystallisation oils, nano liquid handler and advanced automated imaging systems, represents a significant advancement in small molecule crystallisation. By reducing resource consumption and time, while enhancing reproducibility and quality, this method offers a robust and efficient tool for structural analysis. Future work will focus on refining these techniques and exploring their applicability to a broader range of compounds, extending the benefits of high-throughput crystallisation to the wider scientific community.