This paper describes the use of surface plasmon resonance spectroscopy and self-assembled monolayers (SAMs) of alkanethiols on gold to evaluate the ability of surfaces terminating in different combinations of charged groups to resist the nonspecific adsorption of proteins from aqueous buffer. Mixed SAMs formed from a 1:1 combination of a thiol terminated in a trimethylammonium group and a thiol terminated in a sulfonate group adsorbed less than 1% of a monolayer of two proteins with different characteristics:  fibrinogen and lysozyme. Single-component SAMs formed from thiols terminating in groups combining a positively charged moiety and a negatively charged moiety were also capable of resisting the adsorption of proteins. Single-component SAMs presenting single charges adsorbed nearly a full monolayer of protein. The amount of protein that adsorbed to mixed zwitterionic SAMs did not depend on the ionic strength or the pH of the buffer in which the protein was dissolved. The amount of protein that adsorbe...

Zwitterionic SAMs that Resist Nonspecific Adsorption of Protein from Aqueous Buffer

Protein adsorption on solid surfaces

The ubiquitous fungal pathogen Metarhizium anisopliae kills a wide range of insects. Host hemocytes can recognize and ingest its conidia, but this capacity is lost on production of hyphal bodies. We show that the unusual ability of hyphal bodies to avoid detection depends on a gene (Mcl1) that is expressed within 20 min of the pathogen contacting hemolymph. A mutant disrupted in Mcl1 is rapidly attacked by hemocytes and shows a corresponding reduction of virulence to Manduca sexta. Mcl1 encodes a three domain protein comprising a hydrophilic, negatively charged N-terminal region with 14 cysteine residues, a central region comprising tandem repeats (GXY) characteristic of collagenous domains, and a C-terminal region that includes a glycosylphosphatidylinositol-dependent cell wall attachment site. Immunofluorescence assay showed that hyphal bodies are covered by the N-terminal domains of MCL1. The collagen domain became antibody accessible after treatment with DTT, suggesting that the N termini are linked by interchain disulfide bonds and are presented on the cell surface by extended collagenous fibers. Studies with staining reagents and hemocyte monolayers showed that MCL1 functions as an antiadhesive protective coat because it masks antigenic structural components of the cell wall such as β-glucans, and because its hydrophilic negatively charged nature makes it unattractive to hemocytes. A survey of 54 fungal genomes revealed that seven other species have proteins with collagenous domains suggesting that MCL1 is a member of a patchily distributed gene family.

https://www.pnas.org/content/pnas/103/17/6647.full.pdf

A collagenous protective coat enables Metarhizium anisopliae to evade insect immune responses.

Hyperbranched polymers (HBPs), an important subclass of dendritic macromolecules, are highly branched, three-dimensional globular nanopolymeric architectures. Attractive features like highly branched topological structures, adequate spatial cavities, numerous terminal functional groups and convenient synthetic procedures distinguish them from the available polymers (the linear, branched, and crosslinking polymers). Due to their unique physical/chemical properties, applications of HBPs have been explored in a large variety of fields. In particular, HBPs exhibit unique advantages in the biological and biomedical systems and devices. Firstly, the way to prepare HBPs usually only involves simple one-pot reactions and avoids the complicated synthesis and purification procedures, which makes the manufacturing process more convenient, thus reducing production costs. Secondly, the large number of end-groups of HBPs provides a platform for conjugation of the functional moieties and can also be employed to tailor-make the properties of HBPs, enhancing their versatility in biological applications. Thirdly, HBPs possess excellent biocompatibility and biodegradability, controlled responsive nature, and ability to incorporate a multiple array of guest molecules through covalent or noncovalent approaches. All of these features of HBPs are of great significance for designing and producing biomaterials. To date, significant progress has been made for the HBPs in solving some of the fundamental and technical questions toward their bioapplications. The present review highlights the contribution of HBPs to biological and biomedical fields with intent to aid the researchers in exploring HBPs for bioapplications.

Bioapplications of hyperbranched polymers

Platelet adhesion onto segmented polyurethane film surfaces modified by addition and crosslinking of PEO-containing block copolymers

Low protein adsorbing polymer films have been prepared with which to fabricate intravenous containers, designed for compatibility with low concentrations of protein drugs. The material is economically manufactured utilizing physical melt blending of water-soluble surface-modifying polymers (PEO, PEOX, PVA, and PNVP) with a base polymer (EVA, PP, PETG, PMMA, SB, and nylon). Permanency of the hydrophilic surfaces so generated was confirmed by surface contact angle experiments and total organic carbon leachables analysis of the aqueous contacting solutions. Binding of IgG, albumin and insulin was studied. A sixfold reduction of protein adsorption was obtained by adding 5% PVA13K to EVA, for IgG at a bulk concentration of 2.5 ppm. Surface bound protein measured by micro-BCA colorimetry, agreed with the solution protein lost, as determined by the Fluoraldehyde procedure. Imaging of the protein exposed plastic surfaces by silver enhanced protein conjugated gold staining agreed with the quantitative assay determinations.

B E Rabinow

Papers

Biomaterials with permanent hydrophilic surfaces and low protein adsorption properties.