Interactions between circulating nanoengineered polymer particles and extracellular matrix components in vitro.

The extracellular matrix (ECM) that surrounds cells in vivo represents a biological barrier for nanomaterials in biomedicine. Herein, we present a system for investigating the interactions between circulating polymer particles and ECM components in vitro using a commercially available flow-based device. We use this system to show how material-dependent interactions of two different particle types-one assembled using poly(ethylene glycol) (PEG) and one prepared using poly(methacrylic acid) (PMA)-affect their interactions with basement membrane extracts during in vitro circulation, with PEG particles remaining in circulation longer than PMA particles. Further, by comparing macroporous hyaluronic acid gel constructs (typically used for tissue engineering) with basement membrane extracts, we show that scaffold-effects (porosity and surface chemistry) impact on circulation time in vitro. The presented system is simple and modular, and can be used to rapidly screen fundamental interactions of engineered particles with biologically relevant microenvironments under flow-conditions.

Formation and characterisation of a modifiable soft macro-porous hyaluronic acid cryogel platform.

A facile method for the synthesis of cell supportive, highly macro-porous hyaluronic acid (HA) hydrogels via cryogelation is presented. Unmodified HA was chemically cross-linked via EDC/NHS zero-length cross-linking at sub-zero temperatures to yield cryogels with high porosity and high pore interconnectivity. The physical properties of the HA cryogels including porosity, average pore size, elasticity and swelling properties were characterised as a function of cryogelation conditions and composition of the precursor solution. The HA cryogels swell extensively in water, with the average porosities observed being ~90% under all conditions explored. The morphology of the cryogels can be controlled, allowing scaffolds with an average pore size ranging from 18 ± 2 to 87 ± 5 µm to be formed. By varying the cross-linking degree and HA concentration, a wide range of bulk elastic properties can be achieved, ranging from ~1 kPa to above 10 kPa. Preliminary cell culture experiments, with NIH 3T3 and HEK 293 cell lines, performed on biochemically modified and unmodified gels show the cryogels support cell proliferation and cell interactions, illustrating the biomedical potential of the platform.

Cryogels for biomedical applications.

The use of hydrogels as support materials for the growth and proliferation of mammalian cells has been well documented as they closely mimic the gel-like properties - and in some cases also the chemical properties - of the extracellular matrix (ECM), which naturally surrounds the cells of any biological tissue. Macro-porous hydrogels set below the freezing point of the solvent, so-called 'cryogels', have recently gained significant interest in the fields of tissue engineering and in vitro cell culture, thanks to their inherent interconnected macro-porous structure and ease of formation in comparison to other macro-pore forming techniques. This review highlights recent advances in cryogelation techniques and starting materials that can be utilised to synthesise biocompatible and biologically relevant cryogels as well as discussing physicochemical characterisation techniques for these materials. Lastly, emerging trends in the application of cryogels, particularly as three-dimensional ECM mimicking scaffolds for cell culture and tissue engineering, are discussed.