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- Cholinium-Based Good’s Buffers Ionic Liquids as Remarkable Stabilizers and Recyclable Preservation Media for Recombinant Small RNAsPublication . Pedro, Augusto; Pereira, Patrícia; Quental, Maria J.; Carvalho, André P.; Santos, Sérgio M.; Queiroz, João; Sousa, Fani; Freire, Mara G.RNA is a biopolymer of high relevance in the biopharmaceuticals field and in fundamental and applied research; however, the preservation of the RNA stability is still a remarkable challenge. Herein, we demonstrate the enhanced potential of aqueous solutions of self-buffering cholinium-based Good's buffers ionic liquids (GB-ILs), at 20 and 50 % (w/w), as alternative preservation media of recombinant small RNAs. The thermal stability of RNA is highly enhanced by GB-ILs, with an increase of 14 °C in the biopolymer melting temperature - the highest increase observed up to date with ILs. Most GB-ILs investigated improve the stability of RNA at least up to 30-days, both at 25 °C and at 4 °C, without requiring the typical samples freezing. Molecular dynamics simulations were applied to better understand the molecular-level mechanisms responsible for the observed RNA improved stability. The number of IL cations surrounding the RNA chain is similar, yet with differences found for the IL anions, which are responsible for the overall charge of the biopolymer first solvation sphere. No cytotoxicity of the studied solutions containing RNA and ILs at 20 % (w/w) was observed onto two distinct human cell lines, reinforcing their potential to act as preservation media when foreseeing biopharmaceutical applications. Finally, RNA was successfully recovered from the ILs aqueous solutions, without changes in its structural integrity, and the ILs successfully recycled and reused.
- Integrated Extraction-Preservation Strategies for RNA Using Biobased Ionic LiquidsPublication . Quental, Maria V.; Pedro, Augusto; Pereira, Patrícia; Sharma, Mukesh; Queiroz, João; Coutinho, João A.P.; Sousa, Fani; Freire, Mara G.The ubiquitous instability of RNA along with issues associated with its purity degree have been preventing its widespread use as low-cost biotherapeutics. On the basis of the well-known capacity of amino acids to specifically interact with RNA when used as chromatographic ligands, a set of amino-acid-based ionic liquids (AA-ILs) was herein investigated, both to act as preservation media and as phase-forming agents of aqueous biphasic systems (ABS). This set of strategies was combined with the goal of developing integrated extraction-preservation platforms. AA-ILs comprising the cholinium cation and anions derived from l-lysine ([Ch][Lys]), l-arginine ([Ch][Arg]), l-glutamic acid ([Ch][Glu]), and dl-aspartic acid ([Ch][Asp]) were studied. It is shown that the stability of RNA is preserved in aqueous solutions of the studied AA-ILs, even in the presence of ribonucleases (RNases). Furthermore, almost all the investigated AA-ILs display no cytotoxicity onto two distinct human cell lines. After identifying the most promising ILs, ABS formed by AA-ILs and polypropylene glycol with a molecular weight of 400 g mol–1 (PPG 400) were investigated as extraction and purification platforms for RNA. Both with pure RNA and bacterial lysate samples, RNA is successfully extracted to the IL-rich phase without compromising its integrity and stability. On the basis of these results, the integrated extraction-preservation process for RNA is finally demonstrated. RNA is initially extracted from the bacterial lysate sample using ABS, after which the IL-rich phase can be used as the preservation medium of RNA up to its use. RNA can be then recovered from the IL-rich phase by ethanol precipitation, and the ABS phase-forming components recovered and reused. Although improvements in the purity level of RNA are still required, the approach here reported represents a step forward in the development of sustainable processes to overcome the critical demand of high-quality/high-purity RNA to be used as biotherapeutics.