Annelise E. Barron

Peptidomimetic polymers for antifouling surfaces

Exposure of therapeutic and diagnostic medical devices to biological fluids is often accompanied by interfacial adsorption of proteins, cells, and microorganisms. Biofouling of surfaces can lead to compromised device performance or increased cost and in some cases may be life-threatening to the patient. Although numerous antifouling polymer coatings have enjoyed short-term success in preventing protein and cell adsorption on surfaces, none have proven ideal for conferring long-term biofouling resistance. Here we describe a new biomimetic antifouling N-substituted glycine polymer (peptoid) containing a C-terminal peptide anchor derived from residues found in mussel adhesive proteins for robust attachment of the polymer onto surfaces. The methoxyethyl side chain of the peptoid portion of the polymer was chosen for its chemical resemblance to the repeat unit of the known antifouling polymer poly(ethylene glycol) (PEG), whereas the composition of the 5-mer anchoring peptide was chosen to directly mimic the DOPA- and Lys-rich sequence of a known mussel adhesive protein. Surfaces modified with this biomimetic peptide-peptoid conjugate exhibited dramatic reduction of serum protein adsorption and resistance to mammalian cell attachment for over 5 months in an in vitro assay. These new synthetic peptide based antifouling polymers may provide long-term control of surface biofouling in the physiologic, marine, and industrial environments.

Capillary electrophoresis of DNA in uncross-linked polymer solutions

We have used dilute and semi-dilute uncross-linked hydroxyethyl cellulose (HEC) solutions as separation matrices for capillary electrophoresis of DNA restriction fragments. In these experiments, we investigated the effects of HEC molecular weight and concentration on resolution, attempting to relate these parameters to the polymer entanglement threshold concentration. The entanglement thresholds of seven molecular weight fractions of hydroxyethyl cellulose were determined from viscosity-concentration data; the entanglement threshold was found to scale as N-1.2, where N = number of HEC monomers. This finding is not in agreement with classical scaling arguments. We present a relationship to predict the observed entanglement threshold of HEC in solution as a function of number average molecular weight. It was found that excellent separation of phi X174/HaeIII DNA restriction fragments (72-1353 base pairs) by capillary electrophoresis in HEC solutions can be achieved significantly below the entanglement threshold, depending on DNA size and HEC molecular weight. The mechanism of separation in these uncross-linked polymer solutions must therefore be reexamined. Our experiments show that the entanglement threshold is a useful parameter in predicting a range of HEC concentrations which will separate certain DNA fragments for a given HEC molecular weight. However, the presence of a fully entangled network is not a prerequisite for separation.

Mimicry of bioactive peptides via non-natural, sequence-specific peptidomimetic oligomers

Non-natural, sequence-specific peptidomimetic oligomers are being designed to mimic bioactive peptides, with potential therapeutic application. Cationic, facially amphipathic helical beta-peptide oligomers have been developed as magainin mimetics. Non-natural mimics of HIV-Tat protein, lung surfactant proteins, collagen, and somatostatin are also being developed. Pseudo-tertiary structure in beta-peptides and peptoids may herald the creation of entirely artificial proteins.

Bioinspired polymeric materials: in-between proteins and plastics

Chemical and biological researchers are making rapid progress in the design and synthesis of non-natural oligomers and polymers that emulate the properties of natural proteins. Whereas molecular biologists are exploring biosynthetic routes to non-natural proteins with controlled material properties, synthetic polymer chemists are developing bioinspired materials with well-defined chemical and physical properties that function or self-organize according to defined molecular architectures. Bioorganic chemists, on the other hand, are developing several new classes of non-natural oligomers that are bridging the gap between molecular biology and polymer chemistry. These synthetic oligomers have both sidechain and length specificity, and, in some cases, demonstrate capability for folding, self-assembly, and specific biorecognition. Continued active exploration of diverse backbone and sidechain chemistries and connectivities in bioinspired oligomers will offer the potential for self-organized materials with greater chemical diversity and biostability than natural peptides. Taken together, advances in molecular bioengineering, polymer chemistry, and bioorganic chemistry are converging towards the creation of useful bioinspired materials with defined molecular properties.

Advantages and limitations of next-generation sequencing technologies: A comparison of electrophoresis and non-electrophoresis methods

The reference human genome provides an adequate basis for biological researchers to study the relationship between genotype and the associated phenotypes, but a large push is underway to sequence many more genomes to determine the role of various specificities among different individuals that control these relationships and to enable the use of human genome data for personalized and preventative healthcare. The current electrophoretic methodology for sequencing an entire mammalian genome, which includes standard molecular biology techniques for genomic sample preparation and the separation of DNA fragments using capillary array electrophoresis, remains far too expensive (

Polymeric matrices for DNA sequencing by capillary electrophoresis

5 million) to make genome sequencing ubiquitous. The National Human Genome Research Institute has put forth goals to reduce the cost of human genome sequencing to

Protein, cell and bacterial fouling resistance of polypeptoid-modified surfaces: effect of side-chain chemistry

100 000 in the short term and

Soft X-ray tomography of phenotypic switching and the cellular response to antifungal peptoids in Candida albicans

1000 in the long term to spur the innovative development of technologies that will permit the routine sequencing of human genomes for use as a diagnostic tool for disease. Since the announcement of these goals, several companies have developed and released new, non‐electrophoresis‐based sequencing instruments that enable massive throughput in the gathering of genomic information. In this review, we discuss the advantages and limitations of these new, massively parallel sequencers and compare them with the currently developing next generation of electrophoresis‐based genetic analysis platforms, specifically microchip electrophoresis devices, in the context of three distinct types of genetic analysis.

Critical factors for high-performance physically adsorbed (dynamic) polymeric wall coatings for capillary electrophoresis of DNA

We review the wide range of polymeric materials that have been employed for DNA sequencing separations by capillary electrophoresis. Intensive research in the area has converged in showing that highly entangled solutions of hydrophilic, high molar mass polymers are required to achieve high DNA separation efficiency and long read length, system attributes that are particularly important for genomic sequencing. The extent of DNA‐polymer interactions, as well as the robustness of the entangled polymer network, greatly influence the performance of a given polymer matrix for DNA separation. Further fundamental research in the field of polymer physics and chemistry is needed to elucidate the specific mechanisms by which DNA is separated in dynamic, uncross‐linked polymer networks.

Antimicrobial Peptoids Are Effective Against Pseudomonas aeruginosa Biofilms

Peptidomimetic polymers consisting of poly-N-substituted glycine oligomers (polypeptoids) conjugated to biomimetic adhesive polypeptides were investigated as antifouling surface coatings. The polymers were immobilized onto TiO(2) surfaces via an anchoring peptide consisting of alternating residues of 3,4-dihydroxyphenylalanine (DOPA) and lysine. Three polypeptoid side-chain compositions were investigated for antifouling performance and stability toward enzymatic degradation. Ellipsometry and XPS analysis confirmed that purified polymers adsorbed strongly to TiO(2) surfaces, and the immobilized polymers were resistant to enzymatic degradation as demonstrated by mass spectrometry. All polypeptoid-modified surfaces exhibited significant reductions in adsorption of lysozyme, fibrinogen and serum proteins, and were resistant to 3T3 fibroblast cell attachment for up to seven days. Long-term in vitro cell attachment studies conducted for six weeks revealed the importance of polypeptoid side-chain composition, with a methoxyethyl side chain providing superior long-term fouling resistance compared to hydroxyethyl and hydroxypropyl side chains. Finally, attachment of both gram-positive and gram-negative bacteria for up to four days under continuous-flow conditions was significantly reduced on the polypeptoid-modified surfaces compared to unmodified TiO(2) surfaces. The results reveal the influence of polypeptoid side-chain chemistry on short-term and long-term protein, cell and bacterial fouling resistance.