Chitosan in textiles: towards a greener and functional solution

In later years demands upon the manufacturing of consumer goods have increased, with special attention being given to industrials sectors and companies environmental footprint. The textile sector while being one of the largest worldwide sectors in terms of sales is also one of the most polluting ones, as it is a resource intensive (water, energy, etc.) industry, which employs hazardous and poisonous chemicals, large quantities of water and produces heavily polluted wastewaters. In an effort to be more environment friendly, the wastewater management concept of this industry has shifted from treatment to prevention, as such technologies/approaches favoring a “pollution prevention” concept are of great interest and advantageous from an industrial and economic standpoint. The first step of the present work aimed to optimize and characterize the production of the chitosan nanoparticles to be used throughout the work. A study of the impact of three physical parameters (TPP addition time, reaction time and rotation velocity) at two different pH levels upon chitosan nanoparticles production through ionic gelation was carried out in order to define the optimum conditions for nanoparticle production. The results showed that nanoparticles were more homogeneously produced at pH 5 and that it was possible to define a set of optimum production conditions. Additionally, through particle characterization it was possible to validate the biocompatibility of chitosan nanoparticles towards HaCat cells and to establish that they were stable to be freeze dried and stored in the presence of 10 (w/v) of mannitol. The second stage of this thesis focused on the production of nanoencapsulated textile dyes and on screening their connection to textiles. Reactive and disperse textile dyes were successfully nanoencapsulated through ionic gelation with average entrapment efficacies obtained being above 90% and the nanoparticles produced presenting positive charge and sizes between 190 and 800 nm. Furthermore, nanoencapsulated dyes presented no toxicity towards HaCat cells and, above all, no dye-fabric specificity was observed with the produced nanoparticles being capable of dyeing, with various efficacies of dye uptake, the synthetic and natural fabrics tested. Once a successful nanoencapsulation of textiles dyes was achieved the thesis focus shifted towards validation of the biological properties of the nanoparticles and their constituents. To do so a multistep approach was taken, where on an initial phase chitosan solution, first, and then void nanoparticles were used as benchmarks. Their biological activity was validated against various pathogenic microorganisms associated with skin diseases, including drug resistant ones (e.g. MRSA, MRSE, VRSA, A. baumannii), with low minimal inhibitory and bactericidal concentrations, rapid reduction of bacterial counts and high inhibition percentages of bacterial adhesion and biofilm formation being registered. Furthermore, void nanoparticles were also capable of reducing bacterial counts in a HaCat cellular infection model. Based on these results it was then decided to evaluate the biological potential of dye nanoparticles against skin pathogens. The results obtained showed that for the skin pathogens tested low MICs (0.5 – 2 mg/mL) and MBCs (1-3 mg/mL) were registered and effective inhibition of biofilm formation and quorum sensing signaling was observed. Additionally, dye nanoparticles did not impair HaCat metabolism or damaged its cell wall and were capable of managing MRSA capacity to infect HaCat cells as they significantly reduced intracellular and extracellular bacterial counts. The last phase of this thesis focused upon textiles dyed with nanoencapsulated dyes and on answering the question - are the dyed textiles biologically active? The results obtained showed that nanoparticle dyed cotton had no cytotoxic effect upon HaCat cells and that the dyeing process imparted functionality upon cotton, as nanoparticle dyed cotton effectively reduced MSSA, MRSA and A. baumannii bacterial counts. Additionally, dye nanoparticles interaction with cotton was shown to occur through ionic interaction and hydrogen bonding with particles flattening themselves upon the fibre surfaces and coating cotton individual fibres. Overall, the dyeing methodology hereby proposed exhibited capacity to in an easy, onestep process dye and functionalize textiles. With no textile-dye specificity being observed and no salts and chemical adjuvants being used, this process has the potential to alter the way the textile industry operates and diminish its environmental footprint.