Photo-responsive Polymer Nanocapsules

Considerable progress in the design and the synthesis of light-responsive polymer micro- and nanocapsules has been made in recent decades. Diversification of capsule preparation techniques and fine-tuning of materials chemical design provide a wide an almost infinite number of strategies to obtain customer-tailored products. In particular, research and development in the nano-sized range is currently experiencing a burst development and is in constant need for new carriers to further impact frontier applications such as theranostics, nanomedicine, and drug delivery. We have reported a straightforward route for the preparation of solid shell nanocapsules with controlled UV-triggered release. A miniemulsion interfacial polymerization technique has been employed to synthesize in-situ a polyamide shell containing azobenzene segments in the main chain. The trans to cis photo-isomerization of azobenzene, occurring upon UV-light irradiation (360 nm), leads to major rearrangements in the capsules shell inducing the release of encapsulated materials. The feasibility and reliability of the release mechanism has been assessed by monitoring the UV-induced release of a fluorescent probe molecule, Coumarin 6, dispersed in the toluene core. Collectively, these findings outline the efficacy of the proposed approach in view of engineering the delivery of active agents according to specific applications. Moreover, encapsulation and light-triggered release of basil and thyme essential oils was also studied in detail proving the versatility and reliability of the miniemulsion interfacial polycondensation in the preparation of stimuli-responsive capsules. The essential oils have the dual role of active core material and solvent for the azo-monomer in the miniemulsion reaction, thus implying the elimination of potentially toxic organic solvents from the procedure. The photo-induced release mechanism in azo-polymers makes these capsules promising candidate for a wide variety of applications, such as food-packaging, agriculture, household and cosmetics. Moreover, the study regarding Coumarin-6 encapsulation and release, as a model drug, strongly hints at future application in biological environments. Thyme and basil essential oils are renowned antimicrobial agents, used in many food packaging applications. Herein, for the first time to our knowledge, the encapsulation of these essential oils in a packaging material was reported. The coating process of PE and PLA with EO-loaded capsules was efficiently assessed. Both release experiments and antimicrobial tests confirmed the feasibility of the active packaging system. UV-light is poorly available and poses threats to human health as well. Therefore, a red-shift of the azobenzene trans-cis photoisomerization wavelength towards visible range in the radiation spectrum would be preferable. Visible light in the wavelength range of 500-600 nm represents a valid alternative since it is readily provided by natural sunlight or any white desk lamp. We report on the synthesis and characterization of a modified azobenzene, where photo-isomerization is triggered by visible-light. This monomer could be employed in encapsulation of a wide variety of active agents, such as pesticides for crop protection, fragrances for household products and flavors for food engineering, as well as active molecules for cosmetics and medicin