Can Biobased Ionic Liquids act as Cryoprotectants?

Biomaterials research increasingly relies on multifunctional platforms that integrate structural performance with biological activity. In this context, transfersomes have attracted considerable attention due to their adaptability, biocompatibility, and potential for controlled delivery of bioactive compounds. Additionally, ionic liquids (ILs) have been explored as functional compounds in biomaterial design due to their tunable physicochemical properties, low volatility, and capacity to modulate interfacial interactions. When incorporated into nanovesicular systems, they give rise to TransfersomILs, an advanced hybrid nanosystem that combines membrane flexibility with enhanced colloidal stability.

A critical challenge in the development of vesicular biomaterials is ensuring structural integrity and functional preservation during storage. Freeze–thawing and freeze-drying are widely employed stabilization strategies; however, they may induce membrane disruption, aggregation, and loss of encapsulated compounds. Therefore, identifying effective cryo- and lyoprotective agents is essential to maintain nanosystem performance and extend shelf life.

Within this framework, the present study explores biobased ILs as multifunctional excipients in unloaded and loaded TransfersomILs, evaluating their role in preserving physicochemical stability and antioxidant functionality after lyophilization.

Two ILs, (2-hydroxyethyl)-trimethylammonium-L-phenylalaninate [Cho][Phe] and (2-hydroxyethyl)-trimethylammonium glycinate [Cho][Gly], were synthesized and incorporated at 0.2% (v/v). Physicochemical properties of all produced nanoparticles, as well as association and retention efficiencies of caffeic acid-loaded systems, were assessed before and after the freezing strategies. Antioxidant activity was also determined using the DPPH radical scavenging assay.

Results demonstrated that both produced TransfersomILs maintained suitable particle size distribution and colloidal stability after freeze–thawing, demonstrating that biobased ILs exhibited cryoprotective performance comparable to conventional cryoprotectants. In freeze-drying studies, although retention efficiency was lower than that achieved with classical lyoprotectants, structural integrity and antioxidant activity were preserved.

Overall, biobased ILs show potential as alternative cryoprotective compounds for nanovesicular systems, warranting further optimization to enhance their lyoprotective capacity.