Innovative applications of ionic solvents in the chemistry of biopolymers, environmental chemistry, and in formulations for drugs with very low water solubility

Abstract

Solvents can be classified into molecular (MSs; e.g., alcohols) and ionic (ISs), for example ionic liquids (ILs) and deep eutectic solvents (DESs). The objectives of this project are: (i) To synthesize LIs and DESs suitable for the intended applications; (ii) To develop innovative applications for such solvents in the fields of biopolymers (dissolution-, and derivatization of cellulose, Cel, and chitin/chitosan (Qn/Qs); environmental chemistry (water decontamination and CO2 capture); (iii) To develop formulations to solve the problem of very low water solubility of active pharmacological ingredients (APIs), in particular curcumin, niclosamide, and isoliquiritigenin; all are investigated in the topical treatment of chronic skin inflammation; inhibition of cancerous tissues, and inhibition of cancer metastasis. As the difference between Qn and Qs is the degree of de-acetylation, we use the abbreviation Qn/Qs generally, specifying one of the two, where appropriate. The physical dissolution (without the formation of covalent bonds) of Cel, Qn/Qs and Cel + Qn/Qs in ISs has the following objectives: (iv) Regeneration of the dissolved biopolymers, for example as nanoparticles (NPs) that will be used to combat water and air pollution;(v) Conversion of the dissolved biopolymers into derivatives of varyed/controlled average degrees of substitution (DSs). These products include the amide formed by reaction of edetic acid with Qs (Qs-EDTA), and mixed carboxylic esters of Cel (acetate/butyrate, CAB, and acetate/propionate, CAP). The synthesis of these products serves to establish quantitative correlations between DS and the experimental variables of the synthesis (e.g. composition of the medium, time and temperature). Qs-EDTA will be used to decontaminate water from heavy metal ions. (vi) Formulation of biocompatible hydrogels based on ISs that are candidates for the transportation/release of APIs with very low solubility in water, a problem that results in low bioavailability. The above-mentioned applications have in common that the properties of ISs (high polarity, Lewis acid/base character, hydrophobic interactions) lead to strong IS-solute interactions (biopolymer, API) which are fundamental to the success of the intended applications, namely: dissolution of-, and derivatization of biopolymers; decontamination of air (CO2 capture), and water (complexation of heavy metal ions) and, finally, transport/release of APIs. The favorable properties of SIs (thermal stability, dispersible vapor pressure) make it possible to recycle them using simple physical techniques, emphasizing their environmentally friendly nature. (AU)