An Overview of Inverted Colloidal Crystal Systems for Tissue Engineering

Abstract

Scaffolding is at the heart of tissue engineering but the number of techniques available for turning biomaterials into scaffolds displaying the features required for a tissue engineering application is somewhat limited. Inverted colloidal crystals (ICCs) are inverse replicas of an ordered array of monodisperse colloidal particles, which organize themselves in packed long-range crystals. The literature on ICC systems has grown enormously in the past 20 years, driven by the need to find organized macroporous structures. Although replicating the structure of packed colloidal crystals (CCs) into solid structures has produced a wide range of advanced materials (e.g., photonic crystals, catalysts, and membranes) only in recent years have ICCs been evaluated as devices for medical/pharmaceutical and tissue engineering applications. The geometry, size, pore density, and interconnectivity are features of the scaffold that strongly affect the cell environment with consequences on cell adhesion, proliferation, and differentiation. ICC scaffolds are highly geometrically ordered structures with increased porosity and connectivity, which enhances oxygen and nutrient diffusion, providing optimum cellular development. In comparison to other types of scaffolds, ICCs have three major unique features: the isotropic three-dimensional environment, comprising highly uniform and size-controllable pores, and the presence of windows connecting adjacent pores. Thus far, this is the only technique that guarantees these features with a long-range order, between a few nanometers and thousands of micrometers. In this review, we present the current development status of ICC scaffolds for tissue engineering applications.

Artificial opal photonic crystals and inverse opal structures – fundamentals and applications from optics to energy storage

“…17(b) and (c)) under tissue (chicken breast) of between 2 and 5 mm, Sunghwan Kim and colleagues confirm the ability to still detect the photonic stop-band even under a high scattering environment (see Fig. 152,153 C. Inverted opals for thermophotovoltaics and dye-sensitized solar cells Metallic IOs are not normally favoured for optical applications due to their high absorbance in the visible range, but are showing increasing potential for modifying thermal emission as a result of the periodic modulation in the IO structure. The biocompatibility and the degradable, implantable nature of silk IOs present a number of possible applications within biological environments, in particular once the photonic response can still be detected, under living tissue.…”

A colloidoscope of colloid-based porous materials and their uses

“…These studies are particularly useful for membrane and sensing applications, and are related to the diffusion through the pores that is necessary for catalytic and electrode applications. CBPM have also been used in other transport applications such as for cell culture, 210,211 for drug delivery, 212,213 and as membranes and filters, 214 applications we do not cover in this review. 86 Reproduced with permission from the American Chemical Society.…”

Inverse Opal Scaffolds and Their Biomedical Applications

“…[85] Taken together, inverse opal scaffolds present a highly favorable microenvironment for cells to reside in and respond to. [5,24] …”

“…[5,24] Functional biomolecules can be grafted onto the pore surface via covalent cross-linking, non-covalent modification, or physical adsorption to mediate cell adhesion and motility ( e.g., chemotaxis). Using PEG-based inverse opal scaffolds, Irvine and co-workers studied the migration of T lymphocytes between adjacent pores.…”

“…Originating from the concept of salt-leaching or gas-foaming but with an unprecedented control, inverse opal scaffolds are fabricated by templating against cubic close packed ( ccp ) lattices of monodispersed microspheres. [5,19-24] Owing to the monodispersity of the microspheres, the resulting scaffolds possess uniform pores and interconnecting windows across each sample, together with excellent reproducibility in their physical properties across different batches. [5,25] With the use of inverse opals, finally we can achieve a quantitative analysis and understanding of the tissue regeneration process.…”