Bioactive Surfaces

Stimuli-responsive macromolecules (i.e., pH-, thermo-, photo-, chemo-, and bioresponsive polymers) have gained exponential importance in materials science, nanotechnology, and biotechnology during the last two decades. This chapter describes the usefulness of this class of polymer for preparing smart surfaces (e.g., modified planar surfaces, particles surfaces, and surfaces of three-dimensional scaffolds). Some efficient pathways for connecting these macromolecules to inorganic, polymer, or biological substrates are described. In addition, some emerging bioapplications of smart polymer surfaces (e.g., antifouling surfaces, cell engineering, protein chromatography, tissue engineering, biochips, and bioassays) are critically discussed.

The merger of biology and modern microsystem technology bears challenges literally at the interface. Precise control of the interaction between an artificial surface and a biological environment is a prerequisite for a successful interplay of the “living world” with man-made technology. Any design of a chip for a spatially controlled attachment and outgrowth of living cells has to meet two fundamental yet apparently opposing requirements: it has to divide the surface into areas that favor cell adhesion and those that resist it. In the first part of this article, we provide a basis for an understanding of how to achieve both tasks by discussing basic considerations concerning cell adhesion to matrices in vivo and ways to control the interactions between biomacromolecules and surfaces. We also include an overview of current strategies for the integration of living cells on planar devices that aims to provide a starting point for the exploration of the emerging field of cell-chip technology.

Over the last 20 years, integrins have proven to be key players in connecting the internal cell machinery to the extracellular environment. Because the properties of the extracellular milieu strongly influence developmental programs triggered by integrin-mediated adhesion, the development of culture platforms with tunable chemical and physical properties is important for further understanding of the complexity of integrin functions. This chapter introduces biochemically modified gold surface models that have been designed to investigate cell adhesion. Specific emphasis is placed on micellar nanolithography, a technique enabling the preparation of gold nanopatterns. Such substrates are used as an analytical tool to control the activation of single-cell surface receptors for the study of integrin-mediated adhesion and signalling in a quantitative manner.

In recent years, the surface chemistry community has actively pursued the design and generation of stimuli-responsive platforms or dynamic surfaces to control the interface between cells and a solid support. Surface properties can be manipulated through photoactivation, electrochemical potential, pH change, and the addition of a biochemical signal, with the aim of mimicking the extracellular matrix and inducing cellular behavior. This chapter describes recent advances in the development and utility of self-assembled monolayers (SAMs) as dynamic, model substrates for cell biology.

This review presents recent progress in utilizing polymeric films made by the layer-by-layer (LbL) technique (so-called multilayered films) as reservoirs for hosting and releasing bioactive molecules. This relatively new technique is distinguished by its high modularity and structural control at the nanometer level, giving polymeric surface films with tuneable physicochemical properties. A significant increase in research activities regarding the bioapplications of the multilayered films has taken place over the last decade. In this review, we address the bioapplications of LbL films and will focus on the loading and release of the film-embedded bioactive compounds and their bioactivity. Planar and free-standing 3D multilayered polyelectrolyte films (microcapsules) are considered. Special attention is paid to light-stimulated release, interaction of cells with the LbL films, and intracellular light-triggered delivery.

Modern approaches to the production of 3D materials with bioactive interfaces for tissue engineering, biointegrated materials, and biomimetic materials are reviewed. Recent advances in the understanding of how materials passively interact or actively communicate with biological systems via designed material–biology interfaces demand precise means to fabricate macroscopic nanostructured materials. We review modern materials and technology that are available for the production of bioactive scaffolds having spatial control of mechanical, chemical, and biochemical signals at the interface, as well as tailored pore architecture and surface topology.

In this review, the general principles of antimicrobial surfaces will be discussed in detail. Because many common products that keep microbes off surfaces have been banned in the past decade, the search for alternatives is in full run. In recent research, numerous new ways to produce so-called self-sterilizing surfaces have been introduced. These technologies are discussed with respect to their mechanism, particularly focusing on the distinction between biocide-releasing and non-releasing contact-active systems. New developments in the catalytic formation of biocides and their advantages and limitations are also covered. The combination of several mechanisms in one surface modification has considerable benefits, and will be discussed.