Lipid-anchor display on peptoid nanosheets via co-assembly for multivalent pathogen recognition.

Biological systems have evolved sophisticated molecular assemblies capable of exquisite molecular recognition across length scales ranging from angstroms to microns. For instance, the self-organization of glycolipids and glycoproteins on cell membranes allows for molecular recognition of a diversity of ligands ranging from small molecules and proteins to viruses and whole cells. A distinguishing feature of these 2D surfaces is they achieve exceptional binding selectivity and avidity by exploiting multivalent binding interactions. Here we develop a 2D ligand display platform based on peptoid nanosheets that mimics the structure and function of the cell membrane. A variety of small-molecule lipid-conjugates were co-assembled with the peptoid chains to create a diversity of functionalized nanosheet bilayers with varying display densities. The functional heads of the lipids were shown to be surface-exposed, and the carbon tails immobilized into the hydrophobic interior. We demonstrate that saccharide-functionalized nanosheets (e.g., made from globotriaosylsphingosine or 1,2-dipalmitoyl-sn-glycero-3-phospho((ethyl-1',2',3'-triazole)triethyleneglycolmannose)) can have very diverse binding properties, exhibiting specific binding to multivalent proteins as well as to intact bacterial cells. Analysis of sugar display densities revealed that Shiga toxin 1 subunit B (a pentameric protein) and FimH-expressing Escherichia coli (E. coli) bind through the cooperative binding behavior of multiple carbohydrates. The ability to readily incorporate and display a wide variety of lipidated cargo on the surface of peptoid nanosheets makes this a convenient route to soluble, cell-surface mimetic materials. These materials hold great promise for drug screening, biosensing, bioremediation, and as a means to combat pathogens by direct physical binding through a well-defined, multivalent 2D material.

Uniform, Large-Area, Highly Ordered Peptoid Monolayer and Bilayer Films for Sensing Applications.

The production of atomically defined, uniform, large-area 2D materials remains as a challenge in materials chemistry. Many methods to produce 2D nanomaterials suffer from limited lateral film dimensions, lack of film uniformity, or limited chemical diversity. These issues have hindered the application of these materials to sensing applications, which require large-area uniform films to achieve reliable and consistent signals. Furthermore, the development of a 2D material system that is biocompatible and readily chemically tunable has been a fundamental challenge. Here, we report a simple, robust method for the production of large-area, uniform, and highly tunable monolayer and bilayer films, from sequence-defined peptoid polymers, and their application as highly selective molecular recognition elements in sensor production. Monolayers and bilayer films were produced on the centimeter scale using Langmuir-Blodgett methods and exhibited a high degree of uniformity and ordering as evidenced by atomic force microscopy, electron diffraction, and grazing incidence X-ray scattering. We further demonstrated the utility of these films in sensing applications by employing the biolayer interferometry technique to detect the specific binding of the pathogen derived proteins, shiga toxin and anthrax protective antigen, to peptoid-coated sensors.

One low-dose exposure of gold nanoparticles induces long-term changes in human cells.

We report the in vitro long-term (20 wk) changes in cells exposed to well-characterized gold nanoparticles (Au NPs) with varying shapes and surface coatings under both chronic (exposure to Au NPs continuously over 20 wk) and nonchronic (initial acute cell exposure to Au NPs, followed by 20 wk in NP-free cell media) conditions. Both chronic and nonchronic Au NPs exposures at low dose induce modifications at the gene level after long periods. In attempt to overcome from the injuries caused by nanoparticle exposure, genes related to oxidative stress, cell cycle regulation, and inflammation are among those presenting differential expression levels. Surprisingly, the nonchronic exposure induced more gene expression changes than its chronic counterpart and the stress effects caused by this type of exposure were sustained even after 20 wk without any additional NP exposure. NP surface chemistry played an important role in the alteration of gene regulation. Overall, our data suggest that (i) cells can adaptively respond to chronic, low-level NP insults; (ii) the cell stress response is not reversible over time upon removal of NPs upon acute, nonchronic exposure; and (iii) polyethylene glycol is not as benign a surface chemistry as is generally supposed.

New Advances in Nanotechnology-Based Diagnosis and Therapeutics for Breast Cancer: An Assessment of Active-Targeting Inorganic Nanoplatforms.

Breast cancer is a major cause of suffering and mortality among women. Limitations in the current diagnostic methods and treatment approaches have led to new strategies to positively impact the survival rates and quality of life of breast cancer patients. Nanotechnology offers a real possibility of mitigating breast cancer mortality by early-stage cancer detection and more precise diagnosis as well as more effective treatments with minimal side effects. The current nanoplatforms approved for breast cancer therapeutics are based on passive tumor targeting using organic nanoparticles and have not provided the expected significant improvements in the clinic. In this review, we present the emerging approaches in breast cancer nanomedicine based on active targeting using versatile inorganic nanoplatforms with biomedical relevance, such as gold, silica, and iron oxide nanoparticles, as well as their efficacy in breast cancer imaging, drug and gene delivery, thermal therapy, combinational therapy, and theranostics in preclinical studies. The main challenges for clinical translation and perspectives are discussed.

Surface Chemistry of Gold Nanorods.

Gold nanorods have garnered a great deal of scientific interest because of their unique optical properties, and they have the potential to greatly impact many areas of science and technology. Understanding the structure and chemical makeup of their surfaces as well as how to tailor them is of paramount importance in the development of their successful applications. This Feature Article reviews the current understanding of the surface chemistry of as-synthesized gold nanorods, methods of tailoring the surface chemistry of gold nanorods with various inorganic and organic coatings/ligands, and the techniques employed to characterize ligands on the surface of gold nanorods as well as the associated measurement challenges. Specifically, we address the challenges of determining how thick the ligand shell is, how many ligands per nanorod are present on the surface, and where the ligands are located in regiospecific and mixed-ligand systems. We conclude with an outlook on the development of the surface chemistry of gold nanorods leading to the development of a synthetic nanoparticle surface chemistry toolbox analogous to that of synthetic organic chemistry and natural product synthesis.

Impact of Closed System Transfer Device (CSTD) Handling Procedure for Low-Transfer-Volume Dose Preparation of Biologic Drug Products.

Many challenges have been identified for ensuring compatibility of closed system transfer devices (CSTDs) with biologic drug products. One challenge is large hold-up volumes (HUVs) of CSTD components, which can be especially problematic with early-stage biologics when low transfer volumes smaller than the nominal fill volume may be used to achieve a wide range of doses with a single drug product configuration. Here, we identified possible CSTD handling techniques during dose preparation of a drug product requiring small volume transfers during reconstitution, intermediate dilution, and dilution in an IV bag, and systematically evaluated the impact of these handling procedures on the ability to deliver an accurate dose to the next step. We show that small changes to CSTD procedures can have a major impact on dose accuracy, depending on both CSTD HUVs and drug product-specific transfer volumes. We demonstrate that it is possible to craft CSTD instructions for use to mitigate these issues, and that the dose accuracy for specific drug product/CSTD combinations can be estimated using theoretical equations. Finally, we explored potential downsides of these mitigations. Our results emphasize key factors for consideration by both drug and CSTD manufacturers when assessing compatibility and providing CSTD instructions for use with biologics requiring low transfer volumes during dose preparation.

Discovery of Stable and Selective Antibody Mimetics from Combinatorial Libraries of Polyvalent, Loop-Functionalized Peptoid Nanosheets.

The ability of antibodies to bind a wide variety of analytes with high specificity and high affinity makes them ideal candidates for therapeutic and diagnostic applications. However, the poor stability and high production cost of antibodies have prompted exploration of a variety of synthetic materials capable of specific molecular recognition. Unfortunately, it remains a fundamental challenge to create a chemically diverse population of protein-like, folded synthetic nanostructures with defined molecular conformations in water. Here we report the synthesis and screening of combinatorial libraries of sequence-defined peptoid polymers engineered to fold into ordered, supramolecular nanosheets displaying a high spatial density of diverse, conformationally constrained peptoid loops on their surface. These polyvalent, loop-functionalized nanosheets were screened using a homogeneous Förster resonance energy transfer (FRET) assay for binding to a variety of protein targets. Peptoid sequences were identified that bound to the heptameric protein, anthrax protective antigen, with high avidity and selectivity. These nanosheets were shown to be resistant to proteolytic degradation, and the binding was shown to be dependent on the loop display density. This work demonstrates that key aspects of antibody structure and function-the creation of multivalent, combinatorial chemical diversity within a well-defined folded structure-can be realized with completely synthetic materials. This approach enables the rapid discovery of biomimetic affinity reagents that combine the durability of synthetic materials with the specificity of biomolecular materials.

Anisotropic Nanoparticles and Anisotropic Surface Chemistry.

Anisotropic nanoparticles are powerful building blocks for materials engineering. Unusual properties emerge with added anisotropy-often to an extraordinary degree-enabling countless new applications. For bottom-up assembly, anisotropy is crucial for programmability; isotropic particles lack directional interactions and can self-assemble only by basic packing rules. Anisotropic particles have long fascinated scientists, and their properties and assembly behavior have been the subjects of many theoretical studies over the years. However, only recently has experiment caught up with theory. We have begun to witness tremendous diversity in the synthesis of nanoparticles with controlled anisotropy. In this Perspective, we highlight the synthetic achievements that have galvanized the field, presenting a comprehensive discussion of the mechanisms and products of both seed-mediated and alternative growth methods. We also address recent breakthroughs and challenges in regiospecific functionalization, which is the next frontier in exploiting nanoparticle anisotropy.

Gold Nanorods Indirectly Promote Migration of Metastatic Human Breast Cancer Cells in Three-Dimensional Cultures.

Gold nanomaterials are intensively studied for applications in disease detection, diagnosis and therapeutics, and this has motivated considerable research to determine their interaction with biomolecules, cells and cell behaviors. However, few studies look at how nanomaterials alter the extracellular matrix (ECM) and cell-ECM interactions. Nanomaterials in the body would interact with the entire cellular environment, and it is imperative to account for this when studying the impact of nanomaterials on living systems. Furthermore, recent evidence finds that migration rates of cells in 2D can be affected by nanomaterials, and uptake of the nanomaterials is not necessary to exert an effect. In this study, three-dimensional nested type I collagen matrices were utilized as a model ECM to study how gold nanorods affect the migration of MDA-MB-231 human breast cancer cells. Spontaneous cell migration through collagen containing gold nanorods was found to increase with increasing concentrations of gold nanorods, independent of intracellular uptake of the nanorods. Gold nanorods in the collagen matrix were found to alter collagen mechanical properties and structure, molecular diffusion, cellular adhesion, cell morphology, mode of migration and protease expression. Correlation between decreased cellular adhesion and rounded cell morphology and locomotion in nanorod-containing collagen suggests the induction of an amoeboid-like migratory phenotype.

Magnetic, Fluorescent, and Copolymeric Silicone Microspheres.

Silicone microspheres are exceedingly difficult to make. Here, polydimethylsiloxane microspheres (≈1 µm diameter) are synthesized using ultrasonic spray pyrolysis, the first demonstration of a scalable synthetic procedure for crosslinked silicone microspheres. This continuous, aerosol process is also used to directly produce fluorescent, magnetic, and copolymeric derivatives; the potential biomedical applications of these microspheres are explored.

Adsorption of cellular proteins to polyelectrolyte-functionalized gold nanorods: a mechanism for nanoparticle regulation of cell phenotype?

Cell behavior in the presence of nanomaterials is typically explored through simple viability assays, but there is mounting evidence that nanomaterials can have more subtle effects on a variety of cellular functions. Previously our lab demonstrated that gold nanorods functionalized with polyelectrolyte multi-layers inhibited rat cardiac fibroblast-mediated remodeling of type I collagen scaffolds by altering fibroblast phenotype and the mechanical properties of the collagen network. In this work, we examine a possible mechanism for these effects: adsorption of cellular proteins by the nanorods. Mass spectrometric and gel electrophoresis of media collected from cultured cells suggests that a number of proteins, some of which mediate cell-cell and cell-matrix interactions, adsorb onto the surface of these nanoparticles in vitro. Polyethylene glycol coating of the nanorods largely mitigates protein adsorption and fibroblast-mediated collagen remodeling. These results suggest that adsorption of proteins by nanorods could have a significant effect on cell functions, including fibroblast-mediated matrix remodeling.