Note Cyrene™ as an Alternative Sustainable Solvent for the Preparation of Poly(lactic-co-glycolic acid) Nanoparticles Christian Grune a , Jana Thamm a , Oliver Werz b, c , Dagmar Fischer a, c, * a Pharmaceutical Technology and Biopharmacy, Friedrich Schiller University Jena, Lessingstr. 8, 07743 Jena, Germany b Pharmaceutical and Medicinal Chemistry, Friedrich Schiller University Jena, Philosophenweg 14, 07743 Jena, Germany c Jena Center for Soft Matter (JCSM), Friedrich Schiller University Jena, Philosophenweg 7, 07743 Jena, Germany article info Article history: Received 13 May 2020 Revised 29 September 2020 Accepted 25 November 2020 Available online 1 December 2020 Keywords: Biocompatibility Nanoparticles Poly(lactic-co-glycolic acid) (PLGA) Drug delivery system Differential scanning calorimetry (DSC) Light scattering (dynamic) Nanomedicine Poorly water-soluble drug Solvent evaporation Biodegradable polymer abstract Toxic and environmental harmful organic solvents are widely applied to prepare poly(lactic-co-glycolic acid) (PLGA)-based nanoparticles (NP) in standard preparation methods. Alternative non-toxic solvents suffer from disadvantages like high viscosity and plasticizing effects. To overcome these hurdles, Cyrene™ as a new sustainable, non-toxic and low viscous solvent was used to formulate PLGA NPs. A new preparation method was developed and optimized. Small sized blank NPs around 220 nm with a narrow size distribution and highly negative charge (<23 mV) were obtained. To test the application for drug delivery, the lipophilic model drug atorvastatin was encapsulated in high drug loads with com- parable physicochemical characteristics as the blank NPs, and a total drug release within 24 h. No changes of the crystallinity or plasticizing effects could be observed. Highly purified NPs were obtained with a residual Cyrene™ content <2.5%. Finally, the biocompatibility of Cyrene™ itself and of the NPs formed in the presence of Cyrene™ was demonstrated in a hen's egg test. Conclusively, the use of Cyrene™ as solvent offers a simple, fast and non-toxic procedure for preparation of PLGA NPs as drug delivery systems circumventing the downsides of standard methods. © 2020 Published by Elsevier Inc. on behalf of the American Pharmacists Association. Introduction Poly(lactic-co-glycolic acids) (PLGA) are the most widely used biodegradable polymers for applications in humans due to their excellent biocompatibility, tailorable degradability, controlled drug release as well as commercial availability in high quality. Many different technologies have been developed to prepare nano- particulate drug delivery systems on the basis of PLGA, preferen- tially with two standard techniques, the emulsion-diffusion- evaporation method and the nanoprecipitation procedure. 1 How- ever, these techniques suffer from the use of organic solvents like acetonitrile, chloroform, dichloromethane, ethyl acetate or acetone for the dissolution of the hydrophobic PLGA polymer, which are potentially harmful to human health, critical for the natural envi- ronment as well as difficult and expensive to waste. According to the International Conference of Harmonization (ICH) they are categorized in classes II (acetonitrile, chloroform, dichloro- methane) and III (ethyl acetate, acetone). 2 Efforts must be made to purify the final product from solvent residuals, to protect the operator and to recycle the solvent which is often associated with high costs in industrial settings. Consequently, there is a growing demand for alternative sus- tainable and non-toxic solvents for the preparation of PLGA nano- particles (NP). Several reports described the application of glycofurol, low molar mass poly(ethylene glycol), propylene car- bonate, methyl propionate and ethyl formate as substitutes. 3 Additional requirements of the solvents include low viscosity, complete or partly miscibility with water, high drug and solvent stability, and non-volatility. In the present study, Cyrene™ (dihydrolevoglucosenone), a biodegradable, non-toxic, sustainable, and green solvent, produced in a simple two-step synthesis from cellulose by an almost energy neutral process, 4 was investigated regarding its applicability as organic phase for the preparation of PLGA NPs. Cyrene™ is already Abbreviations: DL, drug load; EE, encapsulation efficiency; NP, nanoparticles; PEG 400, 400 g/mol poly(ethylene glycol); PLGA, poly(lactic-co-glycolic acid); PVA, poly(vinyl alcohol); SEM, scanning electron microscopy; TEM, transmission electron microscopy; DLS, dynamic light scattering; HD, hydrodynamic diameter; PDI, polydispersity index; ZP, zeta potential; HPLC, high-performance liquid chroma- tography; PBS, phosphate-buffered saline; Tg, glass transition temperature; LOD, limit of detection; LOQ, limit of quantification; HET-CAV, hen's egg test on the chick area vasculosa. * Corresponding author. Pharmaceutical Technology and Biopharmacy, Friedrich Schiller University Jena, Lessingstr. 8, 07743 Jena, Germany. E-mail address: dagmar.fischer@uni-jena.de (D. Fischer). Contents lists available at ScienceDirect Journal of Pharmaceutical Sciences journal homepage: www.jpharmsci.org https://doi.org/10.1016/j.xphs.2020.11.031 0022-3549/© 2020 Published by Elsevier Inc. on behalf of the American Pharmacists Association. Journal of Pharmaceutical Sciences 110 (2021) 959-964