Major design aspects for novel biomaterials are driven by the desire to mimic more varied and complex properties of a natural cellular environment with man-made materials. The development of stimulus responsive materials makes considerable contributions to the effort to incorporate dynamic and reversible elements into a biomaterial. This is particularly challenging for cell-material interactions that occur at an interface (biointerfaces); however, the design of responsive biointerfaces also presents opportunities in a variety of applications in biomedical research and regenerative medicine. This review will identify the requirements imposed on a responsive biointerface and use recent examples to demonstrate how some of these requirements have been met. Finally, the next steps in the development of more complex biomaterial interfaces, including multiple stimuli-responsive surfaces, surfaces of 3D objects and interactive biointerfaces will be discussed.

Cells adapt and move due to chemical, physical, and mechanical cues from their microenvironment. It is therefore important to create materials that mimic human tissue physiology by surface chemistry, architecture, and dimensionality to control cells in biomedical settings. The impact of the environmental architecture is particularly relevant in the context of cancer cell metastasis, where cells migrate through small constrictions in their microenvironment to invade surrounding tissues. Here, a synthetic hydrogel scaffold with an interconnected, random, 3D microchannel network is presented that is functionalized with collagen to promote cell adhesion. It is shown that cancer cells can invade such scaffolds within days, and both the microarchitecture and stiffness of the hydrogel modulate cell invasion and nuclear dynamics of the cells. Specifically, it is found that cell migration through the microchannels is a function of hydrogel stiffness. In addition to this, it is shown that the hydrogel stiffness and confinement, influence the occurrence of nuclear envelope ruptures of cells. The tunable hydrogel microarchitecture and stiffness thus provide a novel tool to investigate cancer cell invasion as a function of the 3D microenvironment. Furthermore, the material provides a promising strategy to control cell positioning, migration, and cellular function in biological applications, such as tissue engineering.

Controlling supramolecular self-assembly across multiple length scales to prepare gels with localised properties is challenging. Most strategies concentrate on fabricating gels with heterogeneous components, where localised properties are generated by...

Ring opening polymerization (ROP) of N-carboxy anhydride (NCA) amino acids presents a rapid way to synthesize high molecular weight polypeptides with different amino acid compositions. The compositional and functional versatility of polypeptides make these materials an attractive choice for biomaterials. The functional performance of polypeptide materials is equally linked to their conformation which is determined by the amino acid sequence in the polymer chains. Here, the interplay between composition and conformation of synthetic polypeptides obtained by NCA polymerization was explored. Various copolypeptides from Glu(Bzl) and Ser(Bzl) were prepared to investigate how polypeptide composition affected the conformation of the resulting copolymer. Polymerization kinetics indicated that the copolymerization of Glu(Bzl) and Ser(Bzl) preferentially yielded alternating copolymers. Both the polydispersity and the conformation of the polypeptides were dependent on the Ser(Bzl) content in the polymer, demonstrating that polypeptide functionalities could be tuned directly by altering the relative amounts of amino acids in the chain. This work presents the first step toward an improved understanding and control over polypeptide conformation through modulating the amino acid composition of the material. Understanding this sequence-functionality relationship is essential to advancing the use of ROP as a technique to design smart polypeptide based materials with specific functions.

Biogenic nanoparticles are attractive due to their unique surface chemistry compared to chemical counterparts. Underpinning the importance of the surface layer or corona is the interaction between the nanoparticles and the environment. The surface corona provides biological identity, physical structure, colloidal stability and a chemical scaffold for modification. Understanding the structure and composition of the corona that surrounds nanoparticles enables rational design for applications. Previous investigations examining biogenic nanoparticles have purported a coating comprised of biomolecules, however a defined structure is extremely limited. We address this limitation through a detailed examination involving both <i>in situ</i> analyses of silver nanoparticle dispersions (indirect) produced by <i>Fusarium oxysporum</i> and desorbing the surface corona (direct). Using a series of orthogonal characterization techniques we show evidence the surface corona of biogenic silver nanoparticles is comprised of a thin mixed layer of peptides and carbohydrates. We propose the origin of these peptides is from adaptive or protective proteins triggered by environmental stress. The differences and limitations in our two approaches are highlighted. Our findings make it clear that methods used to characterize the inherent surface corona of biogenic silver nanoparticles should be carefully documented for consistent and judicious interpretations.