Surface‐engineered microparticles with a biodegradable polymer core and a programmable thermoresponsive biocompatible copolymer corona are produced. The particles form free‐flowing dispersions below 37 °C, but form porous space‐filling gels above this temperature, as a result of chain collapse of the copolymer corona. When particles are mixed with biological materials, they form encapsulating gels that can support cell growth.

A dual thermoresponsive and magnetic colloidal gel matrix is described for enhanced stem‐cell culture. The combined properties of the material allow enzyme‐free passaging and expansion of mesenchymal stem cells, as well as isolation of cells postculture by the simple process of lowering the temperature and applying an external magnetic field. The colloidal gel can be reconfigured with thermal and magnetic stimuli to allow patterning of cells in discrete zones and to control movement of cells within the porous matrix during culture.

In this paper we report a novel thermogelling matrix that can be assembled in the presence of cells, support cell growth, and revert to a free-flowing colloidal suspension in simple and rapid stages. These reversibly gelling suspensions are prepared from a thermoresponsive component, poly(polyethylene glycol methacrylate ethyl ether) (polyPEGMA-EE 246 ) together with polycaprolactone microparticles. Aqueous dispersions of these materials are free flowing at temperatures below 20 C but switch reversibly over periods of $1 minute to form space filling gels at body temperature (37 C). The viscoelastic properties of the formed gels can be tuned by temperature and composition, enabling these gels to be tailored for specific biomedical applications. We exemplify this by repeated cycles of subculture of fibroblast cells in the gels with the maintenance of viability. As only a temperature change is required to liquefy the gel, subculture of cells was performed without the need for enzymatic or physical cell removal from a substrate. The combination of ease of preparation, the potential for scale-up and positive cell response make these microparticle gels promising as a new class of materials for applications in cell culture, as supports for tissue growth and in cell delivery systems.

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Thermoreversible hydrogels for tissue engineering (TE) purposes have gained increased attention in recent years as they can be combined with cells and drugs and directly injected into the body. Following the fate of transplanted cells in situ is essential in characterizing their distribution and survival, as well as the expression of specific markers or cell-matrix interactions. Existing histological embedding methods, such as paraffin wax embedding, can mechanically damage some biomaterials during processing. In this study, we describe a broadly applicable preparation protocol that allows the handling of delicate, thermoreversible scaffolds for histological sectioning. The gelatin solution permits the embedding of samples at 37 °C, which suits the solid phase of most TE scaffolds. A thermoreversible scaffold of polycaprolactone microparticles, combined with poly(polyethylene glycol methacrylate ethyl ether) and containing human adipose-derived stem cells, was prepared for histology by an initial gelatin embedding step in addition to the standard cryosectioning and paraffin processing protocols. Sections were evaluated by hematoxylin eosin staining and immunostaining for human vimentin. The gelatin embedding retained the scaffold particles and permitted the complete transfer of the construct. After rapid cooling, the solid gelatin blocks could be cryosectioned and paraffin infiltrated. In contrast to direct cryosectioning or paraffin infiltration, the extended protocol preserved the scaffold structure as well as the relevant cell epitopes, which subsequently allowed for immunostaining of human cells within the material. The gelatin embedding method proposed is a generalizable alternative to standard preparations for histological examination of a variety of delicate samples.