Fabrication of Robust Protein Films Using Nanoimprint Lithography.

A nanoimprint-lithography-based fabrication method to generate stable protein films is described. The process is environmentally friendly and generalizable with respect to the protein building blocks. These non-fouling surfaces are readily patternable, incorporate intrinsic protein charge into the film, and able to control cellular adhesion.

Fabrication of functional nanofibers through post-nanoparticle functionalization.

A facile method is developed to functionalize nanofiber surfaces with nanoparticles (NPs) through dithiocarbamate chemistry. Gold nanoparticles (AuNPs) and quantum dots (QDs) are immobilized on the nanofiber surface. These surfaces provide scaffolds for further supramolecular functionalization, as demonstrated through the Förster resonance energy transfer (FRET) pairing of QD-decorated fibers and fluorescent proteins.

Rapid coating of surfaces with functionalized nanoparticles for regulation of cell behavior.

A robust monolayer of nanoparticles is formed via dip-coating of cell culture plates. These surfaces provide cell type-specific modulation of growth behavior without the uptake of nanoparticles.

Stimuli responsive surfaces through recognition-mediated polymer modification.

Specific three-point hydrogen bonding between diamidopyridine (DAP) and thymine (Thy) was employed to reversibly anchor "brush-like" Tri-DAP end-functionalized polystyrene onto Thy-modified silica surfaces.

Recognition-induced polymersomes: structure and mechanism of formation.

Random polystyrene copolymers grafted with complementary recognition elements were combined in chloroform producing vesicular aggregates, that is, recognition-induced polymersomes (RIPs). Reflection interference contrast microscopy (RICM) in solution, coupled with optical microscopy (OM) and atomic force microscopy (AFM) on solid substrates, were used to determine the wall thickness of the RIPs. Rather than a conventional mono- or bilayer structure (approximately 10 or approximately 20 nm, respectively) the RIP membrane was 43+/-7 nm thick. Structural arrangement of the polymer chains on the RIP wall were characterized by using angle-resolved X-ray photoelectron spectroscopy (AR-XPS). The interior portion of the vesicle membrane was found to be more polar, containing more recognition units, than the exterior part. This gradient suggests that a rapid self-sorting of polymers takes place during the formation of RIPs, providing the likely mechanism for vesicle self-assembly.

A comparative analysis of localized and propagating surface plasmon resonance sensors: the binding of concanavalin a to a monosaccharide functionalized self-assembled monolayer.

A comparative analysis of the properties of two optical biosensor platforms: (1) the propagating surface plasmon resonance (SPR) sensor based on a planar, thin film gold surface and (2) the localized surface plasmon resonance (LSPR) sensor based on surface confined Ag nanoparticles fabricated by nanosphere lithography (NSL) are presented. The binding of Concanavalin A (ConA) to mannose-functionalized self-assembled monolayers (SAMs) was chosen to highlight the similarities and differences between the responses of the real-time angle shift SPR and wavelength shift LSPR biosensors. During the association phase in the real-time binding studies, both SPR and LSPR sensors exhibited qualitatively similar signal vs time curves. However, in the dissociation phase, the SPR sensor showed an approximately 5 times greater loss of signal than the LSPR sensor. A comprehensive set of nonspecific binding studies demonstrated that this signal difference was not the consequence of greater nonspecific binding to the LSPR sensor but rather a systematic function of the Ag nanoparticle's nanoscale structure. Ag nanoparticles with larger aspect ratios showed larger dissociation phase responses than those with smaller aspect ratios. A theoretical analysis based on finite element electrodynamics demonstrates that this results from the characteristic decay length of the electromagnetic fields surrounding Ag nanoparticles being of comparable dimensions to the ConA molecules. Finally, an elementary (2 x 1) multiplexed version of an LSPR carbohydrate sensing chip to probe the simultaneous binding of ConA to mannose and galactose-functionalized SAMs has been demonstrated.

Specific Hydrogen-Bond-Mediated Recognition and Modification of Surfaces Using Complementary Functionalized Polymers.

Specific hydrogen-bonding interactions between polymers and surface-tethered recognition elements were used to selectively modify self-assembled monolayers (SAMs) on gold. The interfacial recognition processes were followed by observing frequency changes of thymine-SAM modified quartz crystal microbalance (QCM) chips during adsorption of diamidopyridine-functionalized (DAP) polystyrene from a nonpolar solvent. QCM studies combined with X-ray photoelectron spectroscopy (XPS), water contact angle, and ellipsometry measurements of the polymer-modified surfaces demonstrate the selectivity of the polymer-surface hydrogen-bonding interactions. These studies also indicate that the degree of recognition element functionalization of both the polymer and the surface is crucial in determining the rate, selectivity, and coverage of polymer on the surface.

Surface modification via 'lock and key' specific self-assembly of polyhedral oligomeric silsequioxane (POSS) derivatives to modified gold surfaces.

Diaminopyridine (DAP) functionalized POSS derivatives self-assemble on thymine functionalized monolayers on gold surfaces affording hybrid inorganic/organic surfaces.