Nanocomposite Capsules with Directional, Pulsed Nanoparticle Release

(a) Illustration of the different interaction mechanisms of the proteins, salt, and interface. (b) Sketch of protein adsorption on the attractive surface by increasing cs=cp. Copyright: Authors, reprinted with permission from DOI: 10.1103/PhysRevLett.119.228001.
Multivalent Ion-Activated Protein Adsorption Reflecting Bulk Reentrant Behavior
8th February 2018

The precise spatio-temporal delivery of nanoparticles from polymeric capsules is required for applications ranging from medicine to materials science. Such capsules derive key performance. Facile and robust approaches for nanocomposite capsule fabrication, exhibiting triggered nanoparticle release, remain however elusive due to the complex coupling of polymer-nanoparticle phase behaviour, diffusion, phase inversion and directional solidification. Droplet extraction provides an attractive route to fabricate a range of spherical and anisotropic polymer nanoparticle capsules with controllable internal microstructure. The assembly mechanism is predicated on the engineering of the mixture thermodynamics, demixing and coarsening, phase inversion, and directional solidification during solvent extraction. We demonstrate that microporosity and capsule morphology can be precisely controlled without resorting to complex synthetic routes. We investigate a model system of polyelectrolyte sodium poly(styrene sulfonate) and 22-nm colloidal silica and demonstrate a robust capsule morphology diagram, achieving a range of internal morphologies, including nucleated and bicontinuous microstructures, as well as isotropic and non-isotropic external shapes. Upon dissolution in water, we find that capsules formed with either neat polymers or neat nanoparticles dissolve rapidly and isotropically, whereas bicontinuous, hierarchical, composite capsules dissolve via directional pulses of nanoparticle clusters without disrupting the scaffold, with time scales tuneable from seconds to hours. The versatility, facile assembly, and response of these nanocomposite capsules thus show great promise in precision delivery.

 

Read more:
Udoh E. et al.,
Sci. Adv. 2017; 3:eaao3353

DOI: 10.1126/sciadv.aao3353

SoftComp partner: Imperial College London

 

Phase map and accompanying SEM images of shape and internal structure of polymer-silica composite capsules, as a function of NaPSS and SiO2. Spherical polymer capsules with increasing size and smaller pore dimensions are obtained with increasing NaPSS concentration, shown in grey region. Compact and dimpled capsules are obtained in the absence of polymer, with increasing size with silica content, shown in the pink region. At most NaPSS/ SiO2 compositions, non-spherical capsules with folded geometries are found, shown in light blue region. Within a narrow composition range, indicated in dark blue, dimpled capsules with a bicontinuous internal structure are obtained, comprising hierarchical silica microparticles, and a composite polymer-nanoparticle shell and scaffold. Copyright: Authors

Phase map and accompanying SEM images of shape and internal structure of polymer-silica composite capsules, as a function of NaPSS and SiO2. Spherical polymer capsules with increasing size and smaller pore dimensions are obtained with increasing NaPSS concentration, shown in grey region. Compact and dimpled capsules are obtained in the absence of polymer, with increasing size with silica content, shown in the pink region. At most NaPSS/ SiO2 compositions, non-spherical capsules with folded geometries are found, shown in light blue region. Within a narrow composition range, indicated in dark blue, dimpled capsules with a bicontinuous internal structure are obtained, comprising hierarchical silica microparticles, and a composite polymer-nanoparticle shell and scaffold. Copyright: Authors, taken without changes from 10.1126/sciadv.aao3353 which has been published under Creative Commons Licence CC BY 4.0.

 

 

 

Optical images of dissolution of capsules with compositions highlighted in the figure showing (A-C) instantaneous, (D-E) sustained, pulsed and diffuse release. (F) High magnification images of the surface cracks of the capsule and (G) the emanating micron-sized nanoparticle clusters. (H) The droplet radius of the composite (D) capsule was found to remain approximately constant over time, and release of micron-sized nanoparticle clusters occurs in bursts, over long timescales, tuneable with pH. Lines shown are fits of the well-known Weibull empirical model to the experimental data. Copyright: Authors

Optical images of dissolution of capsules with compositions highlighted in the figure showing (A-C) instantaneous, (D-E) sustained, pulsed and diffuse release. (F) High magnification images of the surface cracks of the capsule and (G) the emanating micron-sized nanoparticle clusters. (H) The droplet radius of the composite (D) capsule was found to remain approximately constant over time, and release of micron-sized nanoparticle clusters occurs in bursts, over long timescales, tuneable with pH. Lines shown are fits of the well-known Weibull empirical model to the experimental data. Copyright: Authors, taken without changes from 10.1126/sciadv.aao3353 which has been published under Creative Commons Licence CC BY 4.0.

 

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