The Janus-SAM approach for the flexible functionalization of gold and titanium oxide surfaces

Utilizing DNA for functionalization of biomaterial surfaces

DNA sequences are widely used for gene transfer into cells including a number of substrate surface-based supporting systems, but due to its singular structure property profile, DNA also offers multiple options for noncanonical applications. The special case of using DNA and oligodeoxyribonucleotide (ODN) structures for surface functionalization of biomedical implants is summarized here with the major focus on (a) immobilization or anchoring of nucleic acid structures on substrate surfaces, (b) incorporation of biologically active molecules (BAM) into such systems, and (c) biological characteristics of the resulting surfaces in vitro and in vivo. Sterilizations issues, important for potential clinical applications, are also considered.

Spatial and Chemical Surface Guidance of NK Cell Cytotoxic Activity

Studying how different signaling pathways spatially integrate in cells requires selective manipulation and control of different transmembrane ligand-receptor pairs at the same time. This work explores a novel method for precisely arranging two arbitrarily chosen ligands on a micron-scale two-dimensional pattern. The approach is based on lithographic patterning of Au and TiO₂ films, followed by their selective functionalization with Ni-nitrilotriacetic acid-histidine and biotin-avidin chemistries, respectively. The selectivity of chemical and biological functionalizations is demonstrated by X-ray photoelectron spectroscopy and immunofluorescence imaging, respectively. This approach is applied to produce the first type of bifunctional surfaces with controllably positioned ligands for activating the receptors of natural killer (NK) immune cells. NK cells were used as a model system to demonstrate the potency of the surface in guiding site-selective cell attachment and activation. Upon applying the suitable ligand or ligand combination, the surfaces guided the appropriate single- or bifunctional attachment and activation. These encouraging results demonstrate the effectiveness of the system as an experimental platform aimed at the comprehensive understanding of the immunological synapse. The great simplicity, modularity, and specificity of this approach make it applicable for a myriad of combinations of other biomolecules and applications, turning it into the "Swiss knife" of biointerfaces.

Segregation versus colocalization: orthogonally functionalized binary micropatterned substrates regulate the molecular distribution in focal adhesions

Orthogonally functionalized binary micropatterned substrates are produced using a novel protocol. The use of adequate peptido-mimetics enables an unprecedented segregation of purified αvβ3 and α5β1 integrins in adjacent microislands and evidences the preference of U2OS cells to colocalize such receptors. Moreover, this tendency can be altered by varying the geometry and composition of the micropatterns.