Preparation of Cell-Embedded Colloidosomes in an Oil-in-Water Emulsion

Abstract

Cell encapsulation by locking the interfacial microgels in a water-in-oil Pickering emulsion has currently been attracting intensive attention because of the biofriendly reaction condition. Various kinds of functional microgels can only stabilize an oil-in-water Pickering emulsion, and it is thus difficult to encapsulate cells in the emulsion where the cells are usually dispersed in the continuous phase. Herein, we introduce a facile method for preparing cell-embedded colloidosomes in an oil-in-water emulsion via polyelectrolyte complexation. Escherichia coli (E. coli) was chosen as a model cell and embedded in the thin shell of chitosan/poly(N-isopropylacrylamide-co-acrylic acid) (P(NIPAM-co-AAc)) microcapsules. This is beneficial for expressing cell function because of the little resistance of mass exchange between the embedded cells and the external environment. Cells can be used in biocatalysis or biomedicine and our product will hold great promises to improve the performance in those fields. The synthesis route presents a platform to prepare cell-embedded microcapsules in an oil-in-water Pickering emulsion in a facile and biocompatible way. First, an emulsion stabilized by P(NIPAM-co-AAc) microgels was prepared. Then, the interfacial microgels in the emulsion were locked by chitosan to form colloidosomes. The mechanism of cell encapsulation in this system was studied via fluorescent labeling. The viability of E. coli after encapsulation is ca. 90%. Encapsulated E. coli is able to metabolize glucose from solution, and exhibits a slower rate than free E. coli. This demonstrates a diffusion constraint through the colloidosome shell.

The behavior of hydrophobic-core/hydrophilic-shell structured microgels at an interface: from Mickering emulsion to colloidosomes with dual-level controlled permeability

“…The P(NIPAM-co-AAc) microgels without a core-shell structure were synthesized based on the literature. 3 The zeta-potential and hydrodynamic diameter of the microgels were measured by a Malvern Zetasizer Nano ZS. A 30 mL aliquot of the microgel dispersion was placed onto a silicon substrate and characterized using the PeakForce QNM (Quantitative NanoMechanics) mode of the AFM (Veeco Metrology) aer being dried at 50 C for 2 hours.…”

“…Colloidosomes are hollow microcapsules with a wall composed of particles at the colloidal scale. Colloidosomes has received considerable attention due to their promising applications in drug delivery systems, 1 cell encapsulation, 2,3 biotechnology, 4 catalysis, [5][6][7] and sensors. 8 In general, colloidosomes are synthesized through the self-assembly of colloidal particles at the surface of emulsion droplets.…”

“…10 The colloidal particles tend to pack close together at the surface of the droplets in the emulsion to minimize the free energy of the system. A certain number of techniques, such as annealing, 9 polyelectrolyte complexation 3,11 and covalent cross-linking, 12,13 are capable of being applied to "lock" these particles for the formation of the wall of the microcapsules. Since the wall of the colloidosomes is composed of integrated colloidal particles, the functionality of the colloidal particles can be inherited by the asformed colloidosomes 14 to meet practical requirements.…”

Preparation of pH Responsive Polystyrene and Polyvinyl Pyridine Nanospheres Stabilized by Mickering Microgel Emulsions

“…The amphiphilic soft microgels with stimuli-responsive properties are used to produce controllable advanced nanomaterials and smart emulsions. These emulsions are applied in food, cosmetics, pharmacy, and petroleum industries, and enzyme catalysis [12][13][14][15][16][17][18][19][20][21][22]. The mechanism to illustrate the emulsion stability using soft gel particles is still under debate.…”

Encapsulation of oils and fragrances by core-in-shell structures from silica particles, polymers and surfactants: The brick-and-mortar concept

“…The term colloidosomes was coined later [27]. Colloidosomes have been used to encapsulate various substances [28][29][30][31] and even biological cells [32,33]. The electrostatically stabilized colloidosomes composed of positively and negatively charged colloid particles represent interesting class of carriers [34,35].…”