Dimeric gold nanoparticle assemblies as tags for SERS-based cancer detection

Herein, a new class of multifunctional materials combining a clustered nanoparticle-based probe is presented for surface enhanced Raman scattering (SERS)-based microscopy and surface functionalization for tissue targeting. Controlled assembly of spherical gold nanoparticles into dimers (DNP-REP) is engineered using a small, rigid Raman-active dithiolated linking reporter (REP) to yield narrow internanoparticle gaps and to strategically generate the "hot spot" while concurrently placing the reporter within the region of highest SERS enhancement. Peptide functionalized DNP-REP materials are highly stable even upon incubation with living cells and show controlled levels of binding and intracellular endocytosis. To demonstrate the functionality of such probes for disease detection, differentially targeted DNP-REPs are incubated over various time points with cultured human glioblastoma cells. Using human glioblastoma cells, the SERS maps of targeted tumor cells show the markedly enhanced signals of the DNP-REP, compared to conventional confocal fluorescence based approaches, especially at low incubation times. Even with as few as 40 internalized DNP-REP, a relatively intense SERS signal is measured, demonstrating the high signal to noise ratio and inherent biocompatibility of the materials. Thus, these Raman reporter-based nanoparticle cluster probes present a promising and versatile optical imaging tool for fast, reliable, selective, and ultrasensitive tissue targeting and disease detection and screening.

Multifunctional albumin nanoparticles as combination drug carriers for intra-tumoral chemotherapy

Current cancer therapies are challenged by weakly soluble drugs and by drug combinations that exhibit non-uniform biodistribution and poor bioavailability. In this study, we have presented a new platform of advanced healthcare materials based on albumin nanoparticles (ANPs) engineered as tumor penetrating, delivery vehicles of combinatorially applied factors to solid tumors. These materials were designed to overcome three sequential key barriers: tissue level transport across solid tumor matrix; uptake kinetics into individual cancer cells; therapeutic resistance to single chemotherapeutic drugs. The ANPs were designed to penetrate deeper into solid tumor matrices using collagenase decoration and evaluated using a three-dimensional multicellular melanoma tumor spheroid model. Collagenase modified ANPs exhibited 1-2 orders of magnitude greater tumor penetration than unmodified ANPs into the spheroid mass after 96 hours, and showed preferential uptake into individual cancer cells for smaller sized ANPs (<100 nm). For enhanced efficacy, collagenase coated ANPs were modified with two therapeutic agents, curcumin and riluzole, with complementary mechanisms of action for combined cell cycle arrest and apoptosis in melanoma. The collagenase coated, drug loaded nanoparticles induced significantly more cell death within 3-D tumor models than the unmodified, dual drug loaded ANP particles and the kinetics of cytotoxicity was further influenced by the ANP size. Thus, multifunctional nanoparticles can be imbued with complementary size and protease activity features that allow them to penetrate solid tumors and deliver combinatorial therapeutic payload with enhanced cancer cytotoxicity but minimal collateral damage to healthy primary cells.

Nanoscale amphiphilic macromolecules with variable lipophilicity and stereochemistry modulate inhibition of oxidized low-density lipoprotein uptake

Amphiphilic macromolecules (AMs) based on carbohydrate domains functionalized with poly(ethylene glycol) can inhibit the uptake of oxidized low density lipoprotein (oxLDL) and counteract foam cell formation, a key characteristic of early atherogenesis. To investigate the influence of lipophilicity and stereochemistry on the AMs' physicochemical and biological properties, mucic acid-based AMs bearing four aliphatic chains (2a) and tartaric acid-based AMs bearing two (2b and 2l) and four aliphatic chains (2g and 2k) were synthesized and evaluated. Solution aggregation studies suggested that both the number of hydrophobic arms and the length of the hydrophobic domain impact AM micelle sizes, whereas stereochemistry impacts micelle stability. 2l, the meso analogue of 2b, elicited the highest reported oxLDL uptake inhibition values (89%), highlighting the crucial effect of stereochemistry on biological properties. This study suggests that stereochemistry plays a critical role in modulating oxLDL uptake and must be considered when designing biomaterials for potential cardiovascular therapies.

In silico design of anti-atherogenic biomaterials

Atherogenesis, the uncontrolled deposition of modified lipoproteins in inflamed arteries, serves as a focal trigger of cardiovascular disease (CVD). Polymeric biomaterials have been envisioned to counteract atherogenesis based on their ability to repress scavenger mediated uptake of oxidized lipoprotein (oxLDL) in macrophages. Following the conceptualization in our laboratories of a new library of amphiphilic macromolecules (AMs), assembled from sugar backbones, aliphatic chains and poly(ethylene glycol) tails, a more rational approach is necessary to parse the diverse features such as charge, hydrophobicity, sugar composition and stereochemistry. In this study, we advance a computational biomaterials design approach to screen and elucidate anti-atherogenic biomaterials with high efficacy. AMs were quantified in terms of not only 1D (molecular formula) and 2D (molecular connectivity) descriptors, but also new 3D (molecular geometry) descriptors of AMs modeled by coarse-grained molecular dynamics (MD) followed by all-atom MD simulations. Quantitative structure-activity relationship (QSAR) models for anti-atherogenic activity were then constructed by screening a total of 1164 descriptors against the corresponding, experimentally measured potency of AM inhibition of oxLDL uptake in human monocyte-derived macrophages. Five key descriptors were identified to provide a strong linear correlation between the predicted and observed anti-atherogenic activity values, and were then used to correctly forecast the efficacy of three newly designed AMs. Thus, a new ligand-based drug design framework was successfully adapted to computationally screen and design biomaterials with cardiovascular therapeutic properties.

Engineering the Design of Brightly-Emitting Luminescent Nanostructured Photonic Composite Systems

Rare-earth doped infrared emitting composites have extensive applications in integrated optical devices such as fibre amplifiers and waveguides for telecommunications, remote sensing, and optoelectronics. In addition, recent advancements in infrared optical imaging systems have expanded the biomedical applications for infrared-emitting composites in diagnosis and imaging of living tissue systems both in vitro and in vivo. Composite systems combine the advantages of polymers (light weight, flexibility, good impact resistance, improved biomedical compatibility, and excellent processability) and inorganic phosphor host materials (low phonon energy, intense emissions, chemical durability, and high thermal stability). This paper provides a brief review of our research progress in the design and synthesis of luminescent photonic nanocomposite systems comprised of rare-earth doped particulates dispersed in a continuous polymeric matrix. The design of brightly-emitting rare-earth doped materials and the influence of host and dopant chemistries on the emission properties are discussed. Methods used to assess and measure the phosphors’ performance are also evaluated in this work. This paper will also examine the solvothermal synthesis method used to control the physical and chemical characteristics of the rare-earth doped particles, and how these characteristics impact the infrared optical properties. Also presented here are recent advances reported with luminescent nanocomposite systems fabricated for optical waveguides and biomedical imaging.

A high content imaging-based approach for classifying cellular phenotypes

Current methods to characterize cell-biomaterial interactions are population-based and rely on imaging or biochemical analysis of end-point biological markers. The analysis of stem cells in cultures is further challenged by the heterogeneous nature and divergent fates of stem cells, especially in complex, engineered microenvironments. Here, we describe a high content imaging-based platform capable of identifying cell subpopulations based on cell phenotype-specific morphological descriptors. This method can be utilized to identify microenvironment-responsive morphological descriptors, which can be used to parse cells from a heterogeneous cell population based on emergent phenotypes at the single-cell level and has been successfully deployed to forecast long-term cell lineage fates and screen regenerative phenotype-prescriptive biomaterials.

Carbohydrate composition of amphiphilic macromolecules influences physicochemical properties and binding to atherogenic scavenger receptor A

Amphiphilic macromolecules (AMs) based on carbohydrate domains functionalized with poly(ethylene glycol) can inhibit the uptake of oxidized low density lipoprotein (oxLDL) mediated by scavenger receptor A (SR-A) and counteract foam cell formation, the characteristic "atherosclerotic" phenotype. A series of AMs was prepared by altering the carbohydrate chemistry to evaluate the influence of backbone architecture on the physicochemical and biological properties. Upon evaluating the degree of polymer-based inhibition of oxLDL uptake in human embryonic kidney cells expressing SR-A, two AMs (2a and 2c) were found to have the most efficacy. Molecular modeling and docking studies show that these same AMs have the most favorable binding energies and most close interactions with the molecular model of the SR-A collagen-like domain. Thus, minor changes in the AMs' architecture can significantly affect the physicochemical properties and inhibition of oxLDL uptake. These insights can be critical for designing optimal AM-based therapeutics for the management of cardiovascular disease.

Cell-cell interactions are essential for maintenance of hepatocyte function in collagen gel but not on matrigel

The objective of this study was to examine the importance of cellular aggregation for the maintenance of liver-specific functions in hepatocytes. We used two culture matrix systems (collagen sandwich and Matrigel) to examine the responsiveness of albumin secretory function in cultured rat hepatocytes under various seeding conditions. With high cell seeding, both culture systems elicited comparable levels of elevated function. Under conditions of sparse seeding, however, their responses were quite distinct: collagen sandwiched cells exhibited a significant deterioration in secretion, while Matrigel-cultured cells retained their basal levels of function. This indicates that a critical degree of cell-cell interactions is essential for promoting function in the collagen sandwich, and in the Matrigel-cultured cells functions may be preserved by constitutive matrix-related phenomena, even in the absence of aggregation. (c) 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 56: 706-711, 1997.

High-content imaging-based screening of microenvironment-induced changes to stem cells

Effective screening methodologies for cells are challenged by the divergent and heterogeneous nature of phenotypes inherent to stem cell cultures, particularly on engineered biomaterial surfaces. In this study, we showcase a high-content, confocal imaging-based methodology to parse single-cell phenotypes by quantifying organizational signatures of specific subcellular reporter proteins and applied this profiling approach to three human stem cell types (embryonic-human embryonic stem cell [hESC], induced pluripotent-induced pluripotent stem cell [iPSC], and mesenchymal-human mesenchymal stem cell [hMSC]). We demonstrate that this method could distinguish self-renewing subpopulations of hESCs and iPSCs from heterogeneous populations. This technique can also provide insights into how incremental changes in biomaterial properties, both physiochemical and mechanical, influence stem cell fates by parsing the organization of stem cell proteins. For example, hMSCs cultured on polymeric films with varying degrees of poly(ethylene glycol) to modulate osteogenic differentiation were parsed using high-content organization of the cytoskeletal protein F-actin. In addition, hMSCs cultured on a self-assembled monolayer platform featuring compositional gradients were screened and descriptors obtained to correlate substrate variations with adipogenic lineage commitment. Taken together, high-content imaging of structurally sensitive proteins can be used as a tool to identify stem cell phenotypes at the single-cell level across a diverse range of culture conditions and microenvironments.

Impact of ionizing radiation on physicochemical and biological properties of an amphiphilic macromolecule

An amphiphilic macromolecule (AM) was exposed to ionizing radiation (both electron beam and gamma) at doses of 25 kGy and 50 kGy to study the impact of these sterilization methods on the physicochemical properties and bioactivity of the AM. Proton nuclear magnetic resonance and gel permeation chromatography were used to determine the chemical structure and molecular weight, respectively. Size and zeta potential of the micelles formed from AMs in aqueous media were evaluated by dynamic light scattering. Bioactivity of irradiated AMs was evaluated by measuring inhibition of oxidized low-density lipoprotein uptake in macrophages. From these studies, no significant changes in the physicochemical properties or bioactivity were observed after the irradiation, demonstrating that the AMs can withstand typical radiation doses used to sterilize materials.

Microfibrous substrate geometry as a critical trigger for organization, self-renewal, and differentiation of human embryonic stem cells within synthetic 3-dimensional microenvironments

Substrates used to culture human embryonic stem cells (hESCs) are typically 2-dimensional (2-D) in nature, with limited ability to recapitulate in vivo-like 3-dimensional (3-D) microenvironments. We examined critical determinants of hESC self-renewal in poly-d-lysine-pretreated synthetic polymer-based substrates with variable microgeometries, including planar 2-D films, macroporous 3-D sponges, and microfibrous 3-D fiber mats. Completely synthetic 2-D substrates and 3-D macroporous scaffolds failed to retain hESCs or support self-renewal or differentiation. However, synthetic microfibrous geometries made from electrospun polymer fibers were found to promote cell adhesion, viability, proliferation, self-renewal, and directed differentiation of hESCs in the absence of any exogenous matrix proteins. Mechanistic studies of hESC adhesion within microfibrous scaffolds indicated that enhanced cell confinement in such geometries increased cell-cell contacts and altered colony organization. Moreover, the microfibrous scaffolds also induced hESCs to deposit and organize extracellular matrix proteins like laminin such that the distribution of laminin was more closely associated with the cells than the Matrigel treatment, where the laminin remained associated with the coated fibers. The production of and binding to laminin was critical for formation of viable hESC colonies on synthetic fibrous scaffolds. Thus, synthetic substrates with specific 3-D microgeometries can support hESC colony formation, self-renewal, and directed differentiation to multiple lineages while obviating the stringent needs for complex, exogenous matrices. Similar scaffolds could serve as tools for developmental biology studies in 3-D and for stem cell differentiation in situ and transplantation using defined humanized conditions.

Oriented, multimeric biointerfaces of the L1 cell adhesion molecule: an approach to enhance neuronal and neural stem cell functions on 2-D and 3-D polymer substrates

This article focuses on elucidating the key presentation features of neurotrophic ligands at polymer interfaces. Different biointerfacial configurations of the human neural cell adhesion molecule L1 were established on two-dimensional films and three-dimensional fibrous scaffolds of synthetic tyrosine-derived polycarbonate polymers and probed for surface concentrations, microscale organization, and effects on cultured primary neurons and neural stem cells. Underlying polymer substrates were modified with varying combinations of protein A and poly-D-lysine to modulate the immobilization and presentation of the Fc fusion fragment of the extracellular domain of L1 (L1-Fc). When presented as an oriented and multimeric configuration from protein A-pretreated polymers, L1-Fc significantly increased neurite outgrowth of rodent spinal cord neurons and cerebellar neurons as early as 24 h compared to the traditional presentation via adsorption onto surfaces treated with poly-D-lysine. Cultures of human neural progenitor cells screened on the L1-Fc/polymer biointerfaces showed significantly enhanced neuronal differentiation and neuritogenesis on all protein A oriented substrates. Notably, the highest degree of βIII-tubulin expression for cells in 3-D fibrous scaffolds were observed in protein A oriented substrates with PDL pretreatment, suggesting combined effects of cell attachment to polycationic charged substrates with subcellular topography along with L1-mediated adhesion mediating neuronal differentiation. Together, these findings highlight the promise of displays of multimeric neural adhesion ligands via biointerfacially engineered substrates to "cooperatively" enhance neuronal phenotypes on polymers of relevance to tissue engineering.

Interconnected contribution of tissue morphogenesis and the nuclear protein NuMA to the DNA damage response

Epithelial tissue morphogenesis is accompanied by the formation of a polarity axis--a feature of tissue architecture that is initiated by the binding of integrins to the basement membrane. Polarity plays a crucial role in tissue homeostasis, preserving differentiation, cell survival and resistance to chemotherapeutic drugs among others. An important aspect in the maintenance of tissue homeostasis is genome integrity. As normal tissues frequently experience DNA double-strand breaks (DSBs), we asked how tissue architecture might participate in the DNA damage response. Using 3D culture models that mimic mammary glandular morphogenesis and tumor formation, we show that DSB repair activity is higher in basally polarized tissues, regardless of the malignant status of cells, and is controlled by hemidesmosomal integrin signaling. In the absence of glandular morphogenesis, in 2D flat monolayer cultures, basal polarity does not affect DNA repair activity but enhances H2AX phosphorylation, an early chromatin response to DNA damage. The nuclear mitotic apparatus protein 1 (NuMA), which controls breast glandular morphogenesis by acting on the organization of chromatin, displays a polarity-dependent pattern and redistributes in the cell nucleus of basally polarized cells upon the induction of DSBs. This is shown using high-content analysis of nuclear morphometric descriptors. Furthermore, silencing NuMA impairs H2AX phosphorylation--thus, tissue polarity and NuMA cooperate to maintain genome integrity.

Kinetically assembled nanoparticles of bioactive macromolecules exhibit enhanced stability and cell-targeted biological efficacy

Kinetically assembled nanoparticles are fabricated from an advanced class of bioactive macromolecules that have potential utility in counteracting atherosclerotic plaque development via receptor-level blockage of inflammatory cells. In contrast to micellar analogs that exhibit poor potency and structural integrity under physiologic conditions, these kinetic nanoparticle assemblies maintain structural stability and demonstrate superior bioactivity in mediating oxidized low-density lipoprotein (oxLDL) uptake in inflammatory cells.

E-cadherin-expressing feeder cells promote neural lineage restriction of human embryonic stem cells

Human embryonic stem cells (hESCs) represent a promising source of tissues of different cell lineages because of their high degree of self-renewal and their unique ability to give rise to most somatic cell lineages. In this article, we report on a new approach to differentiate hESCs into neural stem cells that can be differentiated further into neuronal restricted cells. We have rapidly and efficiently differentiated hESCs into neural stem cells by presenting the cell adhesion molecule, E-cadherin, to undifferentiated hESCs via E-cadherin transfected fibroblast monolayers. The neural restricted progenitor cells rapidly express nestin and beta-III-tubulin, but not glial fibrillary acidic protein (GFAP) during the 1-week E-cadherin induction phase, suggesting that E-cadherin promotes rapid neuronal differentiation. Further, these cells are able to achieve enhanced neuronal differentiation with the addition of exogenous growth factors. Cadherin-induced hESCs show a loss in Oct4 and nestin expression associated with positive staining for vimentin, neurofilament, and neural cell adhesion molecule. Moreover, blocking by functional E-cadherin antibody and failure of paracrine stimulation suggested that direct E-cadherin engagement is necessary to induce neural restriction. By providing hESCs with molecular cues to promote differentiation, we are able to utilize a specific cell-cell adhesion molecule, E-cadherin, to influence the nature and degree of neural specialization.

Polymer-based therapeutics: nanoassemblies and nanoparticles for management of atherosclerosis

Coronary arterial disease, one of the leading causes of adult mortality, is triggered by atherosclerosis. A disease with complex etiology, atherosclerosis results from the progressive long-term combination of atherogenesis, the accumulation of modified lipoproteins within blood vessel walls, along with vascular and systemic inflammatory processes. The management of atherosclerosis is challenged by the localized flare-up of several multipronged signaling interactions between activated monocytes, atherogenic macrophages and inflamed or dysfunctional endothelial cells. A new generation of approaches is now emerging founded on multifocal, targeted therapies that seek to reverse or ameliorate the atheroinflammatory cascade within the vascular intima. This article reviews the various classes and primary examples of bioactive configurations of nanoscale assemblies. Of specific interest are polymer-based or polymer-lipid micellar assemblies designed as multimodal receptor-targeted blockers or drug carriers whose activity can be tuned by variations in polymer hydrophobicity, charge, and architecture. Also reviewed are emerging reports on multifunctional nanoassemblies and nanoparticles for improved circulation and enhanced targeting to atheroinflammatory lesions and atherosclerotic plaques.

Nanomaterials can dynamically steer cell responses to biological ligands

Traditional tissue regeneration approaches to activate cell behaviors on biomaterials rely on the use of extracellular-matrix-based or soluble growth-factor cues. In this article, a novel approach is highlighted to dynamically steer cellular phenomena such as cell motility based on nanoscale substratum features of biological ligands. Albumin-derived nanocarriers (ANCs) with variable nanoscale-size features are functionalized with fibronectin III9-10 matrix ligands, and their effects on primary human keratinocyte activation are investigated. The presentation of fibronectin fragments from ANCs significantly enhances cell migration as compared to free ligands at equivalent concentrations. Notably, cell migration is influenced by the size of the underlying ANCs even for variably sized ANCs covered in comparable levels of fibronectin fragment. For equivalent ligand concentrations, cell migration on the smaller-sized ANCs (30 and 50 nm) is significantly enhanced as compared to that on larger-sized ANCs (75 and 100 nm). In contrast, the enhancement of cell migration on nanocarriers is abolished by the use of immobilized, biofunctionalized ANCs, indicating that "dynamic" nanocarrier internalization events underlie the role of nanocarrier geometry on the differential regulation of cell migration kinetics. Uptake studies using fluorescent ANCs indicate that larger-sized ANCs cause delayed endocytic kinetics and hence could present barriers for internalization during the cell adhesion and motility processes. Motile cells exhibit diminished migration upon exposure to clathrin inhibitors, but not caveolin inhibitors, suggesting the role of clathrin-mediated endocytosis in facilitating cell migratory responsiveness to the nanocarriers. Overall, a monotonic relationship is found between the nanocarrier cytointernalization rate and the cell migration rate, suggesting the possibility of designing biointerfacial features for the dynamic control of cell migration. Thus, the functionalization of a mobile nanocarrier by a biorelevant ligand can be used to sensitize cellular motility activation to the adhesion ligands, and such nanocarrier interfaces can dynamically attune cell migration kinetics by modulating the uptake of the ligand-nanocarrier complex via nanocarrier size.

Albumin nanoshell encapsulation of near-infrared-excitable rare-Earth nanoparticles enhances biocompatibility and enables targeted cell imaging

The use of traditional fluorophores for in vivo imaging applications is limited by poor quantum yield, poor tissue penetration of the excitation light, and excessive tissue autofluorescence, while the use of inorganic fluorescent particles that offer a high quantum yield is frequently limited due to particle toxicity. Rare-earth-doped nanoparticles that utilize near-infrared upconversion overcome the optical limitations of traditional fluorophores, but are not typically suitable for biological application due to their insolubility in aqueous solution, lack of functional surface groups for conjugation of biomolecules, and potential cytotoxicity. A new approach to establish highly biocompatible and biologically targetable nanoshell complexes of luminescent rare-earth-doped NaYF(4) nanoparticles (REs) excitable with 920-980 nm near-infrared light for biomedical imaging applications is reported. The approach involves the encapsulation of NaYF(4) nanoparticles doped with Yb and Er within human serum albumin nanoshells to create water-dispersible, biologically functionalizable composite particles. These particles exhibit narrow size distributions around 200 nm and are stable in aqueous solution for over 4 weeks. The albumin shell confers cytoprotection and significantly enhances the biocompatibility of REs even at concentrations above 200 microg REs mL(-1). Composite particles conjugated with cyclic arginine-glycine-aspartic acid (cRGD) specifically target both human glioblastoma cell lines and melanoma cells expressing alpha(v)beta(3) integrin receptors. These findings highlight the promise of albumin-encapsulated rare-earth nanoparticles for imaging cancer cells in vitro and the potential for targeted imaging of disease sites in vivo.

Controllable inhibition of cellular uptake of oxidized low-density lipoprotein: structure-function relationships for nanoscale amphiphilic polymers

A family of anionic nanoscale polymers based on amphiphilic macromolecules (AMs) was developed for controlled inhibition of highly oxidized low-density lipoprotein (hoxLDL) uptake by inflammatory macrophage cells, a process that triggers the escalation of a chronic arterial disease called atherosclerosis. The basic AM structure is composed of a hydrophobic portion formed from a mucic acid sugar backbone modified at the four hydroxyls with lauroyl groups conjugated to hydrophilic poly(ethylene glycol) (PEG). The AM structure-activity relationships were probed by synthesizing AMs with six key variables: length of the PEG chain, carboxylic acid location, type of anionic charge, number of anionic charges, rotational motion of the anionic group, and PEG architecture. All AM structures were confirmed by nuclear magnetic resonance spectroscopy and their ability to inhibit hoxLDL uptake in THP-1 human macrophage cells was compared in the absence and presence of serum. We report that AMs with one, rotationally restricted carboxylic acid within the hydrophobic portion of the polymer was sufficient to yield the most effective AM for inhibiting hoxLDL internalization by THP-1 human macrophage cells under serum-containing conditions. Further, increasing the number of charges and altering the PEG architecture in an effort to increase serum stabilization did not significantly impair the ability of AMs to inhibit hoxLDL internalization, suggesting that selected modifications to the AMs could potentially promote multifunctional characteristics of these nanoscale macromolecules.

Interplay of anionic charge, poly(ethylene glycol), and iodinated tyrosine incorporation within tyrosine-derived polycarbonates: Effects on vascular smooth muscle cell adhesion, proliferation, and motility

Regulation of smooth muscle cell adhesion, proliferation, and motility on biomaterials is critical to the performance of blood-contacting implants and vascular tissue engineering scaffolds. The goal of this study was to examine the underlying substrate-smooth muscle cell response relations, using a selection of polymers representative of an expansive library of multifunctional, tyrosine-derived polycarbonates. Three chemical components within the polymer structure were selectively varied through copolymerization: (1) the content of iodinated tyrosine to achieve X-ray visibility; (2) the content of poly(ethylene glycol) (PEG) to decrease protein adsorption and cell adhesivity; and (3) the content of desaminotyrosyl-tyrosine (DT), which regulates the rate of polymer degradation. Using quartz crystal microbalance with dissipation, we quantified differential serum protein adsorption behavior because of the chemical components DT, iodinated tyrosine, and PEG: increased PEG content within the polymer structure progressively decreased protein adsorption but the simultaneous presence of both DT and iodinated tyrosine reversed the effects of PEG. The complex interplay of these components was next tested on the adhesion, proliferation, and motility behavior cultured human aortic smooth muscle cells. The incorporation of PEG into the polymer reduced cell attachment, which was reversed in the presence of iodinated tyrosine. Further, we found that as little as 10% DT content was sufficient to negate the PEG effect in polymers containing iodinated tyrosine, whereas in non-iodinated polymers, the PEG effect on cell attachment was reversed. Cross-functional analysis of motility and proliferation revealed divergent substrate chemistry related cell response regimes. For instance, within the series of polymers containing both iodinated tyrosine and 10% of DT, increasing PEG levels lowered smooth muscle cell motility without a change in the rate of cell proliferation. In contrast, for non-iodinated tyrosine and 10% of DT, increasing PEG levels increased cell proliferation significantly while reducing cell motility. Clearly, the polycarbonate polymer library offers a sensitive platform to modulate cell adhesion, proliferation, and motility responses, which, in turn, may have implications for controlling vascular remodeling in vivo. Additionally, our data suggests unique biorelevant properties following the incorporation of iodinated subunits in a polymeric biomaterial as a potential platform for X-ray visible devices.

Parsing the early cytoskeletal and nuclear organizational cues that demarcate stem cell lineages

Our recent report suggests that subtle changes in early cytoskeletal protein-level organization correlate with long-term stem cell lineage commitment. In this extra-view, we dissect changes in the expression of both cytoskeletal and nuclear-regulating genes that may precede and, possibly, govern the formative lineage-specific organizational cues. Human mesenchymal stem cells cultured on glass under basal, osteogenic, and adipogenic induction media were analyzed for gene expression profiles within the first 24 hours. Several key actin organization regulating genes and nuclear and cell cycle regulatory genes were found to be upregulated in osteogenic media compared to adipogenic and basal conditions. Given the role of both cytoskeletal and nuclear genes, we examined the possibility of classifying stem cell subpopulations using high content imaging approaches based on the organization of both actin, as previously proposed, as well as nuclear organization and distribution of a nuclear organizational protein, the nuclear mitotic apparatus (NuMA). A pool of combined cytoskeletal and nuclear descriptors were merged into a composite feature space via dimensionality reduction, data fusion, and classification methodologies. This composite approach enabled feature-based identification of specific lineage committed as well as non-differentiating cell populations. Using the improved classification of this high-content imaging-based profiling tool, we demonstrate that MSCs induced to differentiate to either osteogenic or adipogenic lineages are discernable within the first 24 hours from each other and from non-differentiating cells.

Osteogenic differentiation of human mesenchymal stem cells on poly(ethylene glycol)-variant biomaterials

This study evaluated the osteogenic differentiation of human mesenchymal stem cells (MSCs), on tyrosine-derived polycarbonates copolymerized with poly(ethylene glycol) (PEG) to determine their potential as a scaffold for bone tissue engineering applications. The addition of PEG in the backbone of polycarbonates has been shown to alter mechanical properties, degradation rates, degree of protein adsorption, and subsequent cell adhesion and motility in mature cell phenotypes. Its effect on MSC behavior is unknown. MSC morphology, motility, proliferation, and osteogenic differentiation were evaluated on polycarbonates containing 0-5% PEG over a 14 day culture. MSCs on polycarbonates containing 0% or 3% PEG content upregulated the expression of osteogenic markers as demonstrated by alkaline phosphatase activity and osteocalcin expression although at different stages in the 14 day culture. Cells on polycarbonates containing no PEG were characterized as having early onset of cell spreading and osteogenic differentiation. Cells on 3% PEG surfaces were delayed in cell spreading and osteogenic differentiation, but had the highest motility as compared with cells on substrates containing no PEG and substrates containing 5% PEG at early time points. Throughout the culture, cells on polycarbonates containing 5% PEG had the lowest levels of osteogenic markers, displayed poor cell-substrate adhesion, and established cell-cell aggregates. Thus, designing substrates with minute variations in PEG may serve as a tool to guide MSC adhesion and motility accompanying osteogenic differentiation, and may be beneficial for abundant bone tissue formation in vivo.

Synthesis and Cytotoxicity of Y(2)O(3) Nanoparticles of Various Morphologies

As the field of nanotechnology continues to grow, evaluating the cytotoxicity of nanoparticles is important in furthering their application within biomedicine. Here, we report the synthesis, characterization, and cytotoxicity of nanoparticles of different morphologies of yttrium oxide, a promising material for biological imaging applications. Nanoparticles of spherical, rod-like, and platelet morphologies were synthesized via solvothermal and hydrothermal methods and characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), light scattering, surface area analysis, thermogravimetric analysis (TGA), and zeta potential measurements. Nanoparticles were then tested for cytotoxicity with human foreskin fibroblast (HFF) cells, with the goal of elucidating nanoparticle characteristics that influence cytotoxicity. Cellular response was different for the different morphologies, with spherical particles exhibiting no cytotoxicity to HFF cells, rod-like particles increasing cell proliferation, and platelet particles markedly cytotoxic. However, due to differences in the nanoparticle chemistry as determined through the characterization techniques, it is difficult to attribute the cytotoxicity responses to the particle morphology. Rather, the cytotoxicity of the platelet sample appears due to the stabilizing ligand, oleylamine, which was present at higher levels in this sample. This study demonstrates the importance of nanoparticle chemistry on in vitro cytotoxicity, and highlights the general importance of thorough nanoparticle characterization as a prerequisite to understanding nanoparticle cytotoxicity.