Engineering Commons^™

Micropatterning Of Poly (N-Isopropylacrylamide) (Pnipaam) Hydrogels: Effects On Thermosensitivity And Cell Release Behavior, Huijie Hou, Yaping Hou, Melissa Grunlan, Dany Munoz Pinto, Mariah Hahn, Arum Han

Dany J. Munoz Pinto

The thermally driven, reversible change in the surface properties of poly (N-isopropylacrylamide) (PNIPAAm) hydrogels from a hydrophilic (water-swollen) state to a hydrophobic (deswollen) state when heated above the volume phase transition temperature (VPTT, ~35 oC) makes them useful in inducing controlled cell release. To improve the kinetics of swelling and deswelling, we have prepared microstructured (i.e., micropillared) thermoresponsive surfaces comprising pure PNIPAAm hydrogel and nanocomposite PNIPAAm hydrogel embedded with polysiloxane colloidal nanoparticles (~220 nm diameter, 1 wt%) via photopolymerization. The thermosensitivity (i.e., degree and rate of swelling/deswelling) of these surfaces and how it can be regulated using different micropillar sizes …

Influence Of Select Extracellular Matrix Proteins On Mesenchymal Stem Cell Osteogenic Commitment In Three-Dimensional Contexts, Silvia Becerra-Bayona, Viviana Guiza-Arguello, Xin Qu, Dany Munoz Pinto, Mariah Hahn

Dany J. Munoz Pinto

Growth factors have been shown to be powerful mediators of mesenchymal stem cell (MSC) osteogenic differentiation. However, their use in tissue engineered scaffolds not only can be costly but also can induce undesired responses in surrounding tissues. Thus, the ability to specifically promote MSC osteogenic differentiation in the absence of exogenous growth factors via the manipulation of scaffold material properties would be beneficial. The current work examines the influence of select extracellular matrix (ECM) proteins on MSC osteogenesis toward the goal of developing scaffolds with intrinsically osteoinductive properties. Fibrinogen (FG), fibronectin (FN) and laminin-1 (LN) were chosen for evaluation due …

Relative Impact Of Form-Induced Stress Vs. Uniaxial Alignment On Multipotent Stem Cell Myogenesis, Dany Munoz Pinto, Xin Qu, Loveleena Bansal, Heather Hayenga, Juergen Hahn, Mariah Hahn

Dany J. Munoz Pinto

Tissue engineering strategies based on multipotent stem cells (MSCs) hold significant promise for the repair or replacement of damaged smooth muscle tissue. To design scaffolds which specifically induce MSC smooth muscle lineage progression requires a deeper understanding of the relative influence of various microenvironmental signals on myogenesis. For instance, MSC myogenic differentiation has been shown to be promoted by increases in active RhoA and FAK, both of which can be induced via increased cell–substrate stress. Separate studies have demonstrated MSC myogenesis to be enhanced by uniaxial cell alignment. The goal of the present study was to compare the impact of …

Osteogenic Potential Of Poly(Ethylene Glycol)–Poly(Dimethylsiloxane) Hybrid Hydrogels, Dany Munoz Pinto, Andrea Jimenez-Vergara, Yaping Hou, Heather Hayenga, Alejandra Rivas, Melissa Grunlan, Mariah Hahn

Dany J. Munoz Pinto

Growth factors have been shown to be potent mediators of osteogenesis. However, their use in tissue-engineered scaffolds not only can be costly but also can induce undesired responses in surrounding tissues. Thus, the ability to specifically induce osteogenic differentiation in the absence of exogenous growth factors through manipulation of scaffold material properties would be desirable for bone regeneration. Previous research indicates that addition of inorganic or hydrophobic components to organic, hydrophilic scaffolds can enhance multipotent stem cell (MSC) osteogenesis. However, the combined impact of scaffold inorganic content and hydrophobicity on MSC behavior has not been systematically explored, particularly in three-dimensional …

A Comparative Study Of The Cytotoxicity And Corrosion Resistance Of Nickel–Titanium And Titanium–Niobium Shape Memory Alloys, Rebecca Mcmahon, Ji Ma, Stanislav Verkhoturov, Dany Munoz Pinto, Ibrahim Karaman, Felix Rubitschek, Hans Maier, Mariah Hahn

Dany J. Munoz Pinto

Nickel–titanium (NiTi) shape memory alloys (SMAs) are commonly used in a range of biomedical applications. However, concerns exist regarding their use in certain biomedical scenarios due to the known toxicity of Ni and conflicting reports of NiTi corrosion resistance, particularly under dynamic loading. Titanium–niobium (TiNb) SMAs have recently been proposed as an alternative to NiTi SMAs due to the biocompatibility of both constituents, the ability of both Ti and Nb to form protective surface oxides, and their superior workability. However, several properties critical to the use of TiNb SMAs in biomedical applications have not been systematically explored in comparison with …

Influence Of Glycosaminoglycan Identity On Vocal Fold Fibroblast Behavior, Andrea Jimenez-Vergara, Dany Munoz Pinto, Silvia Becerra-Bayona, Bo Wang, Alexandra Iacob, Mariah Hahn

Dany J. Munoz Pinto

Poly(ethylene glycol) (PEG) hydrogels have recently begun to be studied for the treatment of scarred vocal fold lamina propria due, in part, to their tunable mechanical properties, resistance to fibroblast-mediated contraction, and ability to be polymerized in situ. However, pure PEG gels lack intrinsic biochemical signals to guide cell behavior and generally fail to mimic the frequency-dependent viscoelastic response critical to normal superficial lamina propria function. Recent results suggest that incorporation of viscoelastic bioactive substances, such as glycosaminoglycans (GAGs), into PEG networks may allow these gels to more closely approach the mechanical responses of normal vocal fold lamina propria while …

Thermoresponsive Nanocomposite Hydrogels: Transparency, Rapid Deswelling And Cell Release, Yaping Hou, Ruochong Fei, Jonathan Burkes, Shin Lee, Dany Munoz Pinto, Mariah Hahn, Melissa Grunlan

Dany J. Munoz Pinto

Thermal modulation reversibly switches poly(N-isopropylacrylamide) (PNIPAAm) hydrogels between a water-swollen and a deswollen state which is useful for a variety of biomedical applications. The utility and efficiency of PNIPAAm hydrogels requires tailoring their rate of deswelling/reswelling, mechanical properties and/or optical clarity. In the current work, we prepared novel thermoresponsive nanocomposite hydrogels comprised of a PNIPAAm hydrogel matrix and polysiloxane colloidal nanoparticles (∼54 nm ave. diameter) via in situ photopolymerization of aqueous solutions of NIPAAm monomer, N, N′-methylenebisacrylamide (BIS, crosslinker), photoinitiator and 0.5–4.0 wt% polysiloxane nanoparticles (wt% solids of nanoparticles with respect to NIPAAm weight) at ∼7 °C. At these nanoparticle …

Regulation Of Smooth Muscle Cell Phenotype By Glycosaminoglycan Identity, Xin Qu, Andrea Jimenez-Vergara, Dany Munoz Pinto, Diana Ortiz, Rebecca Mcmahon, Deissy Cristancho, Silvia Becerra-Bayona, Viviana Guiza-Arguello, K Grande-Allen, Mariah Hahn

Dany J. Munoz Pinto

The retention of lipoproteins in the arterial intima is an initial event in early atherosclerosis and occurs, in part, through interactions between negatively charged glycosaminoglycans (GAGs) and the positively charged residues of apolipoproteins. Smooth muscle cells (SMCs) which infiltrate into the lipoprotein-enriched intima have been observed to transform into lipid-laden foam cells. This phenotypic switch is associated with SMC acquisition of a macrophage-like capacity to phagocytose lipoproteins and/or of an adipocyte-like capacity to synthesize fatty acids de novo. The aim of the present work was to explore the impact of GAG identity on SMC foam cell formation using a scaffold …

Bioactive Hydrogels Based On Designer Collagens, Elizabeth Cosgriff-Hernandez, Mariah Hahn, Brooke Russell, Thomas Wilems, Dany Munoz Pinto, Mary Beth Browning, Jose Rivera, Magnus Höök

Dany J. Munoz Pinto

Designer Collagens are based on streptococcal collagen-like (Scl) proteins that form a triple helix similar to mammalian collagens but that are non-platelet aggregating. In contrast to the numerous cell-binding sites on collagen, Scl2 from Streptococcus pyogenes serotype M28 does not contain any known cell-binding sites and thus provides a blank slate in terms of cellular interactions. In the current study, Scl2 protein was modified to include receptor binding motifs that interact with α1 and/or α2 integrin subunits. The modfied Scl2 proteins have been demonstrated to mediate differential endothelial cell (EC) and smooth muscle cell (SMC) adhesion via these integrins and …

Approach For Fabricating Tissue Engineered Vascular Grafts With Stable Endothelialization, Andrea Jimenez-Vergara, Viviana Guiza-Arguello, Silvia Becerra-Bayona, Dany Munoz Pinto, Rebecca Mcmahon, Anabel Morales, Lynnette Cubero-Ponce, Mariah Hahn

Dany J. Munoz Pinto

A major roadblock in the development of tissue engineered vascular grafts (TEVGs) is achieving construct endothelialization that is stable under physiological stresses. The aim of the current study was to validate an approach for generating a mechanically stable layer of endothelial cells (ECs) in the lumen of TEVGs. To accomplish this goal, a unique method was developed to fabricate a thin EC layer using poly(ethylene glycol) diacrylate (PEGDA) as an intercellular “cementing” agent. This EC layer was subsequently bonded to the lumen of a tubular scaffold to generate a bi-layered construct. The viability of bovine aortic endothelial cells (BAECs) through …

Inorganic–Organic Hybrid Scaffolds For Osteochondral Regeneration, Dany Munoz Pinto, Rebecca Mcmahon, Melissa Kanzelberger, Andrea Jimenez-Vergara, Melissa Grunlan, Mariah Hahn

Dany J. Munoz Pinto

Ligament graft failure frequently results from poor integration of the replacement tissue with associated bone. Thus, the ability to regenerate the bone-ligament osteochondral interface would be advantageous in ligament reconstruction. At the osteochondral interface, the tissue transitions from a bone-like matrix to fibrocartilage. Therefore, a scaffold which promotes a spatially regulated transition in cell behavior from osteoblast-like to chondrocyte-like would be desirable. Previous research indicates that addition of inorganic components to organic scaffolds can enhance the deposition of bone-like matrix by associated osteoblasts. We therefore reasoned that a gradient in the inorganic content of a hybrid inorganic-organic scaffold may induce …

Photo-Cross-Linked Pdmsstar-Peg Hydrogels: Synthesis, Characterization, And Potential Application For Tissue Engineering Scaffolds, Yaping Hou, Cody Schoener, Katherine Regan, Dany Munoz Pinto, Mariah Hahn, Melissa Grunlan

Dany J. Munoz Pinto

Inorganic−organic hydrogels with tunable chemical and physical properties were prepared from methacrylated star polydimethylsiloxane (PDMSstar-MA) and diacrylated poly(ethylene glycol) (PEG-DA) for use as tissue engineering scaffolds. A total of 18 compositionally unique hydrogels were prepared by photo-cross-linking, varying weight ratios of PEG-DA and PDMSstar-MA of different molecular weights (Mn): PEG-DA (Mn = 3.4k and 6k g/mol) and PDMSstar-MA (Mn = 1.8k, 5k, and 7k g/mol). Introduction of PDMSstar-MA caused formation of discrete PDMS-enriched microparticles dispersed within the PEG matrix. The swelling ratio, mechanical properties in tension and compression, nonspecific protein adhesion, controlled introduction of bioactivity, and cytotoxicity of hydrogels were …

Probing Vocal Fold Fibroblast Response To Hyaluronan In 3d Contexts, Dany Munoz Pinto, Andrea Jimenez-Vergara, L Gelves, Rebecca Mcmahon, Viviana Guiza-Arguello, Mariah Hahn

Dany J. Munoz Pinto

A number of treatments are being investigated for vocal fold (VF) scar, including designer implants. The aim of the present study was to validate a 3D model system for probing the effects of various bioactive moieties on VF fibroblast (VFF) behavior toward rational implant design. We selected poly(ethylene glycol) diacrylate (PEGDA) hydrogels as our base-scaffold due to their broadly tunable material properties. However, since cells encapsulated in PEGDA hydrogels are generally forced to take on rounded/stellate morphologies, validation of PEGDA gels as a 3D VFF model system required that the present work directly parallel previous studies involving more permissive scaffolds. …

Uncoupled Investigation Of Scaffold Modulus And Mesh Size On Smooth Muscle Cell Behavior, Dany Munoz Pinto, Allen Bulick, Mariah Hahn

Dany J. Munoz Pinto

Although scaffold material properties are known to critically impact cell behavior, it has proven difficult to correlate specific cell responses to isolated scaffold parameters, inhibiting rational design of scaffold material properties. The aim of this study was to validate a systematic approach for evaluating the influence of initial scaffold modulus and mesh size on cell extracellular matrix (ECM) deposition and phenotype. Poly(ethylene glycol) diacrylate (PEGDA) hydrogels were selected for this study because of their tunable material properties. Following screening of six distinct PEGDA hydrogels, three formulations were identified which permitted uncoupled investigation of scaffold mesh size and modulus within the …

Lamina Propria Cellularity And Collagen Composition: An Integrated Assessment Of Structure In Humans, Dany Munoz Pinto, Peter Whittaker, Mariah Hahn

Dany J. Munoz Pinto

Objectives: In this study, we quantitatively examined cell density, collagen types I and III, and regional variations in collagen fiber thickness and orientation in the human midmembranous vocal fold lamina propria (LP).

Methods: Lamina propria samples were solubilized with proteinase K or with cyanogen bromide. Cell density was assessed in proteinase K digests by measuring DNA and normalizing it to tissue total protein. Collagen types I and III were quantified by enzyme-linked immunosorbent assay–based detection of collagen type–specific peptides generated by cyanogen bromide digestion. In addition, LP total collagen was determined by measuring sample hydroxyproline levels. Variations in collagen fiber …

Impact Of Endothelial Cells And Mechanical Conditioning On Smooth Muscle Cell Extracellular Matrix Production And Differentiation, Allen Bulick, Dany Munoz Pinto, Xin Qu, Mousami Mani, Deissy Cristancho, Matthew Urban, Mariah Hahn

Dany J. Munoz Pinto

The aim of the current study was to explore the separate and coupled effects of endothelial cell (EC) presence and mechanical conditioning on smooth muscle cell (SMC) responses by combining bilayered poly(ethylene glycol) diacrylate (PEGDA) hydrogels with a pulsatile flow bioreactor. Each construct was composed of an outer PEGDA layer containing SMC and an inner PEGDA layer, either with or without EC. After an initial 3 days of static culture, EC+ and EC− constructs were each further divided into two subgroups, half of which received mechanical conditioning mimetic of late gestation (mean pressures of ∼50 mmHg and peak-to-trough pressure differentials …

Influence Of Hydrogel Mechanical Properties And Mesh Size On Vocal Fold Fibroblast Extracellular Matrix Production And Phenotype, Huimin Liao, Dany Munoz Pinto, Xin Qu, Yaping Hou, Melissa Grunlan, Mariah Hahn

Dany J. Munoz Pinto

Current clinical management of vocal fold (VF) scarring produces inconsistent and often suboptimal results. Researchers are investigating a number of alternative treatments for VF lamina propria (LP) scarring, including designer implant materials for functional LP regeneration. In the present study, we investigate the effects of the initial scaffold elastic modulus and mesh size on encapsulated VF fibroblast (VFF) extracellular matrix (ECM) production toward rational scaffold design. Poly(ethylene glycol) diacrylate (PEGDA) hydrogels were selected for this study since their material properties, including mechanical properties, mesh size, degradation rate and bioactivity, can be tightly controlled and systematically modified. Porcine VFF were encapsulated …