nanoprecipitation

Nanoprecipitation, also known as the solvent displacement method, is a technique used to prepare polymeric nanoparticles. A polymer is dissolved in a water-miscible organic solvent and then added to or injected into an aqueous phase containing a stabilizer under gentle stirring. The rapid transfer of solvent into the water causes the polymer to become supersaturated and precipitate as nanoscale particles. Stabilizers adsorb onto the particle surface to prevent aggregation, yielding relatively narrow size distributions.

Typical process steps involve preparing an organic phase with the polymer and solvent, preparing an aqueous phase with a surfactant or stabilizer, and then mixing the two phases under controlled rate and stirring. The organic solvent diffuses into the water, leading to particle formation. Residual solvent is removed by evaporation or dialysis, and the suspension is often purified by centrifugation or filtration.

Key parameters that influence outcomes include the polymer type and concentration, solvent choice, stabilizer type and concentration, temperature, addition rate, and stirring conditions. Particle sizes commonly fall in the range of about 10 to 200 nanometers, with the polydispersity index indicating the distribution width.

Advantages of nanoprecipitation include its simplicity, low energy input, and compatibility with hydrophobic polymers and sensitive cargos. It is often conducted under mild aqueous conditions and can be scalable with proper mixing strategies. Limitations include possible residual organic solvent and the need for stabilizers to control aggregation; encapsulation efficiency depends on polymer–drug interactions and may vary with formulation.

Applications span drug delivery, imaging, and theranostics, with polymers such as PLGA, PCL, and PLA frequently used to form the nanoparticle matrix.