Resumen de Ionic complexes of naturally-occurring biopolymers and cationic surfactants: a platform for industrial and biomedical applications
In recent years, the increasing public concern about the environmental pollution caused by persistent plastic wastes has stimulated the interest in replacing synthetic polymers by biopolymers. The term biopolymer refers to polymers that are renewable or biodegradable or both. Biopolymers are capable of bio-assimilation at accelerated rates so they are biocompatible with the environment. Furthermore, their sustainability is of exceptional interest; the renewable origin of biopolymers makes them inexhaustible in contrast with the uncertain accessibility at medium-term of synthetic polymers produced from fossil sources. Nevertheless, biopolymers often have inferior properties compared to commodity polymers.
Modification is a way to improve properties and achieve property combinations required for specific applications. Therefore the synthesis, characterization and property evaluation of new biopolymers derivatives are essential tasks that have to be done for the development of new materials able to replace the traditional plastics in areas such as industrial, medical, food, consumer products, and pharmaceutical applications.
In the present Thesis, the chemical modification of two kinds of carboxylic biopolymers has been studied to respond to the necessity of creating new biopolymer derivatives with advanced properties at reasonable cost. Poly (gamma-glutamic acid) (PGGA) and hyaluronic acid (HyA) were the biopolymers selectedin this Thesis for their capacity to form stable ionic complexes with cationic surfactants to generate stable materials with new properties. These complexes are currently object of intensive research in our group due to their outstanding features. They are easily prepared and they tend to be selfassembled in well-ordered amphiphilic structures able to respond reversibly to thermal effects. This behaviour is of high scientific interest and also of practical relevance in the design of medical devices for thermally and chemically controlled store and delivery of drugs.
The main goal of this Thesis is the preparation of ionic complexes of the two mentioned polyacids using different cationic surfactants depending on the desired final properties. The first part of the work is devoted to provide physicochemical knowledge of the structure and properties of alkyltrimethylphosphonium surfactants which have potential interest for novel applications. Then these surfactants were coupled to both PGGA and HyA to obtain the respective ionic complexes with biocide activity and thermal stability higher than those made by their ammonium analogs. PGGA complexes, abbreviated as nATMP·PGGA, have high interest as food preserving and packaging applications displaying as main advantage the edibility of the polymer and the possibility of improving their basic properties through blending with nanoclays. On the other hand, HyA complexes, nATMP·HyA, are useful to obtain HyA derivatives with antimicrobial activity. In addition, the preparation of nanoparticles of nATMP·HyA with antimicrobial properties was feasible using the ionotropic gelation method.
The s econd part of the Thes is was devoted to the preparation of “greener” complexes of hyaluronic acid. For this regard, alkanoylcholine surfactants were used to prepare the ionic complexes nACh·HyA. These complexes constitute a highly promising biocompatible/biodegradable platform for the design of systems suitable for drug transport and targeting delivery in anticancer chemotherapy because it was demonstrated that non-cytotoxic nanoparticles can be prepared from these systems.
The third part of the Thesis is dedicated to the preparation of biocompatible antimicrobial complexes using as cationic surfactant one of the most potent food preservative agents that is known today, that is the ethyl alpha-N-lauroyl L-arginate chloride surfactant (also known as LAE). These complexes (LAE·PGGA and LAE·HyA) are shown to be potential candidates to develop antimicrobial materials.
