Designing nanostructured block copolymer surfaces to control protein adhesion.

The profile and conformation of proteins that are adsorbed onto a polymeric biomaterial surface have a profound effect on its in vivo performance. Cells and tissue recognize the protein layer rather than directly interact with the surface. The chemistry and morphology of a polymer surface will govern the protein behaviour.

Bioadhesion: a review of concepts and applications.

Bioadhesion refers to the phenomenon where natural and synthetic materials adhere to biological surfaces. An understanding of the fundamental mechanisms that govern bioadhesion is of great interest for various researchers who aim to develop new biomaterials, therapies and technological applications such as biosensors. This review paper will first describe various examples of the manifestation of bioadhesion along with the underlying mechanisms.

Protein conformation changes on block copolymer surfaces detected by antibody-functionalized atomic force microscope tips.

Conformational changes of fibronectin (Fn) deposited on poly(methyl methacrylate) and poly(acrylic acid) block copolymers with identical chemical compositions were detected using an antibody-functionalized atomic force microscope (AFM) tip. Based on the antibody-protein adhesive force maps and phase imaging, it was found that the nanomorphology of the triblock copolymer is conducive to the exposure of the arginine-glycine-aspartic acid (RGD) groups in Fn. For the first time, X-ray photoelectron spectroscopy was used to elucidate surface chemical composition and confirm AFM results.

Bioadhesion of various proteins on random, diblock and triblock copolymer surfaces and the effect of pH conditions.

The adhesive interactions of block copolymers composed of poly(methyl methacrylate) (PMMA)/poly(acrylic acid) (PAA) and poly(methyl methacrylate)/poly(2-hydroxyethyl methacrylate) (PHEMA) with the proteins fibronectin, bovine serum albumin and collagen were studied by atomic force microscopy. Adhesion experiments were performed both at physiological pH and at a slightly more acidic condition (pH 6.2) to model polymer-protein interactions under inflammatory or infectious conditions.

Synthesis and morphological characterization of block copolymers for improved biomaterials.

Biocompatible polymers are known to act as scaffolds for the regeneration and growth of bone. Block copolymers are of interest as scaffold materials because a number of the blocks are biocompatible, and their nanostructure is easily tunable with synthetic techniques. In this paper, we report the synthesis of a novel class of biomaterials from block copolymers containing a hydrophobic block of methyl methacrylate and a hydrophilic block of either acrylic acid, dimethyl acrylamide, or 2-hydroxyethyl methacrylate.

Nanotribological properties of novel lubricants for magnetic tapes.

Two classes of novel lubricants, perfluoropolyethers (PFPE) and ionic liquids (ILs), were deposited on metal film magnetic tapes. The adhesive force and coefficient of friction of lubricated and unlubricated tapes were investigated at the nanoscale with an atomic force microscope (AFM) as a function of various humidity and temperature conditions. Microscale tests with a ball-on-flat tribometer were also performed in order to study the length-scale effects on friction.

A nanoscale friction investigation during the manipulation of nanoparticles in controlled environments.

Future micro/nanodevices will contain very small features such that liquid lubrication is not practical and inherent lubricity is needed. In this study, a nanoscale friction investigation was carried out during the manipulation of Au and SiO(2) nanoparticles on silicon using atomic force microscopy (AFM). Nanoparticle sliding was characterized by quantifying the lateral force associated with the AFM tip twisting as it hits the particle edge.

Nanomechanical and nanotribological characterization of noble metal-coated AFM tips for probe-based ferroelectric data recording.

Probe-based data recording is being developed as an alternative technology for ultrahigh areal density. In ferroelectric data storage, a conductive atomic force microscope (AFM) probe with a noble metal coating is placed in contact on lead zirconate titanate (PZT) film, which serves as the ferroelectric material. A crucial mechanical reliability concern is tip wear during contact of the ferroelectric material with the probe.

AFM-based nanotribological and electrical characterization of ultrathin wear-resistant ionic liquid films.

Ionic liquids (ILs) are considered as lubricants for micro/nanoelectromechanical systems (MEMS/NEMS) due to their excellent thermal and electrical conductivity. So far, only macroscale friction and wear tests have been conducted on these materials. Evaluating the nanoscale tribological performance of ILs when applied as a few nanometers-thick film on a substrate is a crucial step to understand how these novel materials can efficiently lubricate MEMS/NEMS devices.

Surface potential and resistance measurements for detecting wear of chemically-bonded and unbonded molecularly-thick perfluoropolyether lubricant films using atomic force microscopy.

The wear of perfluoropolyether (PFPE) lubricants applied on Si(100) and an Au film on Si(100) substrate at ultralow loads was investigated by using atomic force microscopy (AFM)-based surface potential and resistance measurements. Surface potential data is used in detecting lubricant removal and the initiation of wear on the silicon substrate. The surface potential change is attributed to the change in the work function of the silicon after wear, and electrostatic charge build-up of debris in the lubricant.