Communicating assemblies of biomimetic nanocapsules

Abstract

Communication assemblies between biomimetic nanocapsules in a 3D closed system with self-regulating and self-organization functionalities were demonstrated for the first time. Two types of biomimetic nanocapsules, TiO2/polydopamine capsules and SiO2/polyelectrolytes capsules with different stimuli-responsive properties were prepared and leveraged to sense the external stimulus, transmit chemical signaling, and autonomic communication-controlled release of active cargos. The capsules have clear core-shell structures with average diameters of 30 nm and 25 nm, respectively. The nitrogen adsorption-desorption isotherms and thermogravimetric analysis displayed their massive pore structures and encapsulation capacity of 32% of glycine pH buffer and 68% of benzotriazole, respectively. Different from the direct release mode of the single capsule, the communication assemblies show an autonomic three-stage release process with a "jet lag" feature, showing the internal modulation ability of self-controlled release efficiency. The control overweight ratios of capsules influences on communication-release interaction between capsules. The highest communication-release efficiency (89.6% of benzotriazole) was achieved when the weight ratio of TiO2/polydopamine/SiO2/polyelectrolytes capsules was 5 : 1 or 10 : 1. Communication assemblies containing various types of nanocapsules can autonomically perform complex tasks in a biomimetic fashion, such as cascaded amplification and multidirectional communication platforms in bioreactors.

Fig. 1. Schematic representation of the self-controlled artificial nanocapsule networks. Stable reverse microemulsion templates were first prepared by mixing cyclohexane, deionized water, and non-ionic surfactant polyoxyethylene nonylphenylether (CO-520). The as-formed microemulsion was ultrasonicated for 15 min to obtain uniform and monodisperse droplets, followed by growing inorganic shells (TiO₂/SiO₂) on the templates. Subsequently, the formation of biomimetic nanocapsules was present by cargo loading and exterior shell building through dopamine polymerisation and polyelectrolyte layer-by-layer (LBL) assembly, respectively. Then, the mixed solution containing TiO₂–pH@PDA and SiO₂–BTA@PEs was illuminated by visible light for 400 min using a 100 W Xe lamp under continuous stirring. The pH change of the solution was tested at the given interval. The fluorescence intensity at the emission maximum of BTA was plotted as a function of time to obtain a final communication-controlled release profile.

Fig. 2. TEM image of a typical (a) TiO₂; (b) TiO₂–pH@PDA capsules; (c) N₂ sorption isotherms of TiO₂ and SiO₂ (77.3 K): (i) filled circles, adsorption experiments; (ii) unfilled circle, desorption experiments. (d) TEM images of SiO₂; and (e) SiO₂–BTA@PEs capsules; (f) the enlarged view of a single SiO₂–BTA@PEs capsule.

Fig. 3. ATR-FTIR spectra of (a) TiO₂ (black), TiO₂–pH@PDA capsules (red); (b) SiO₂ (black), SiO₂–BTA@PEs capsules (purple).

Fig. 4. Dynamic release behaviour controlled by chemical information exchange between different capsules. (a) UV-vis spectra of BTA released from SiO₂–BTA@Pes capsules (TiO₂–pH@PDA/SiO₂–BTA@PEs = 5 : 1); (b) the release profile of BTA controlled by single SiO₂–BTA@PEs capsules (red dotted line) and communication-controlled by mixed capsules (red line), and pH change (blue line); (c) the release profile of BTA under different ratio of TiO₂–pH@PDA to SiO₂–BTA@Pes capsules; (d) the cumulative release efficiency of BTA under different ratio of TiO₂–pH@PDA to SiO₂–BTA@Pes capsules.

Fig. 5. Schematic representation of the communication mechanism of self-controlled artificial nanocapsule networks. The different weight ratios of TiO₂–pH@PDA/SiO₂–BTA@PEs capsules create different self-communication strategy. The lower ratio leads to incomplete release of BTA with a negative feedback loop. The higher ratios trigger complete release of BTA with positive feedback loop.