Magneto-responsive alginate capsules

Abstract

Upon incorporation of magnetic nanoparticles (mNPs) into gels, composite materials called ferrogels are obtained. These magneto-responsive systems have a wide range of potential applications including switches and sensors as well as drug delivery systems. In this article, we focus on the properties of calcium alginate capsules, which are widely used as carrier systems in medicine and technology. We studied the incorporation of different kinds of mNPs in matrix capsules and in the core and the shell of hollow particles. We found out that not all particle-alginate or particle-CaCl2 solution combinations were suitable for a successful capsule preparation on grounds of a destabilization of the nanoparticles or the polymer. For those systems allowing the preparation of switchable beads or capsules, we systematically studied the size and microscopic structure of the capsules, their magnetic behavior and mechanical resistance.

Strong Deformation of Ferrofluid-Filled Elastic Alginate Capsules in Inhomogenous Magnetic Fields

“…On the other hand, magnetic deformation of capsules filled with magnetic particles was reported in Refs. 23,24; these magnetic particles, however, aggregated and did not remain in a stable ferrofluid state. The aim of this work is a reliable capsule system, into which a stable ferrofluid can be loaded at high concentra-tion such that it can strongly deform in magnetic fields, which is important for possible applications of capsules as actuators, switches, or valves.…”

“…Magnetic nanoparticles, which are sterically stabilized by amphiphiles such as lauric acid or electrostatically stabilized, destabilize and flocculate in the presence of calcium ions if both ions and nanoparticles are in the aqueous phase in the liquid core of the capsule. 24 To reduce this effect oil-soluble magnetic particles can be used, which are encapsulated in an oil in water emulsion, where calcium is solved in the aqueous emulsion phase. 26 In previous work, we showed that encapsulation of a stable ferrofluid is possible with this technique and that a significant deformation in magnetic fields can be achieved.…”

“…In emulsion encapsulation, the moduli were lowered by the addition of nanoparticles. 24 As the main goal was to obtain easily deformable capsules, this was achieved by creating very thin shells. A remarkable result is the high surface Poisson ratio, which points to an areaincompressible shell.…”

Shape Tuning and Size Prediction of Millimeter-Scale Calcium-Alginate Capsules with Aqueous Core

“…where d D is the Caps displacement, F is the measured force, h is the membrane thickness, which is imported as a fixed value of 0.20 mm, r is the radius of the Caps and υ s is the surface Poisson ratio for which a value of 1/2 was assumed for the alginate hydrogel [25]. The permeability of mm-CaSA-Caps was measured by the diffusion of glucose from bulk solution into intra-hollow Caps.…”

Magnetically Aligned Nanorods in Alginate Capsules (MANiACs): Soft Matter Tumbling Robots for Manipulation and Drug Delivery

“…Owing to its biodegradability, non-toxicity, non-immunogenicity, ease of processing, and low cost, alginate has been broadly employed across a variety of medical devices [11]. Capsules of alginate ranging in size from tens of nanometers [12] to several millimeters [13] can be implanted in humans with minimal side effects [14]. As a result, alginate capsules incorporating a broad array of payloads have been deployed for a variety of purposes, including drug delivery, cell encapsulation, bone regeneration, wound healing, and regenerative medicine [15].…”