Colloidosomes: Selectively Permeable Capsules Composed of Colloidal Particles

Abstract

We present an approach to fabricate solid capsules with precise control of size, permeability, mechanical strength, and compatibility. The capsules are fabricated by the self-assembly of colloidal particles onto the interface of emulsion droplets. After the particles are locked together to form elastic shells, the emulsion droplets are transferred to a fresh continuous-phase fluid that is the same as that inside the droplets. The resultant structures, which we call "colloidosomes," are hollow, elastic shells whose permeability and elasticity can be precisely controlled. The generality and robustness of these structures and their potential for cellular immunoisolation are demonstrated by the use of a variety of solvents, particles, and contents.Efficient encapsulation of active ingredients such as drugs, proteins, vitamins, flavors, gas bubbles, or even living cells is becoming increasingly important for a wide variety of applications and technologies, ranging from functional foods to drug delivery to biomedical applications (1-8). Increasingly sophisticated techniques are being developed to create physical structures that can meet the demanding requirements of these applications. A versatile technique should provide efficient encapsulation in structures whose size, permeability, mechanical strength, and compatibility can be easily controlled. Control of the size allows flexibility in applications and choice of encapsulated materials; control of the permeability allows selective and timed release; control of the mechanical strength allows the yield stress to be adjusted to withstand varying of mechanical loads and to enable release by defined shear rates; and control of compatibility allows encapsulation of fragile and sensitive ingredients, such as biomolecules and cells. Precise control of all these features would allow the strategic design of possible release mechanisms. Ideally, it should be feasible to construct these capsules from a wide variety of inorganic, organic, or polymeric materials to provide flexibility in their uses.A variety of techniques has been developed to address specific encapsulation requirements: Coacervation, or controlled gelation, of polymers at the surface of water drops can be used to fabricate nano-or microporous capsules (1-5, 9); other fluid extrusion methods can also be used to create the polymer coating (6, 7). Coating immiscible templates by electrostatic deposition of alternating layers of charged polymers or particles can be used to fabricate nanoporous capsules (10-18). Microfabrication technology can be used to create submillimeter-sized silicon capsules with exquisitely precise nanometer-scale holes for selective permeability and slow release (19). However, despite the enormous progress in encapsulation technologies, these methods can be limited in their applicability, in the range of materials that can be used, in the uniformity of pore sizes, in the accessible permeabilities and elasticities, or in the ease of synthesis, filling efficiency, and yield. We present a flexi...

Fabrication, Assembly, and Application of Patchy Particles

“…The particles adsorb at the oil-water interface and form colloidosomes, which allows surface functionalization of the particles in either the water or the oil phase. [83] The distance by which the particles penetrate into the wax determines the amount of functionalized area. In an oil-in-water emulsion, the embedment of particles in the wax is adjusted by controlling the hydrophobicity of the particles.…”

Physical ageing of the contact line on colloidal particles at liquid interfaces

“…But it is not clear whether the results of these experiments, which use spreading solvents to deposit the particles on the interface, should apply to systems such as Pickering emulsions 5 and colloidosomes 8,12 , which are prepared using a different method, mechanical agitation.…”

Potential applications of nanotechnology in the agro-food sector

“…Nano-encapsulates may consist of a core composed of one to several types of compounds surrounded by a wall or barrier (DINSMORE, 2002;LETCHFORD;BURT, 2007). These delivery systems have its roots in the pharmaceutical industry, where often synthetic polymeric nano-encapsulates are employed.…”