Bioengineering

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Open AccessCommunication

Freeze Drying Improves the Shelf-Life of Conductive Polymer Modified Neural Electrodes

by Himadri S. Mandal, Richard O. Cliff and Joseph J. Pancrazio

Bioengineering 2015, 2(3), 176-183; https://doi.org/10.3390/bioengineering2030176 - 7 Aug 2015

Cited by 3 | Viewed by 5226

Coating microelectrodes with conductive polymer is widely recognized to decrease impedance and improve performance of implantable neural devices during recording and stimulation. A concern for wide-spread use of this approach is shelf-life, i.e., the electrochemical stability of the coated microelectrodes prior to use. In this work, we investigated the possibility of using the freeze-drying process in order to retain the native low impedance state and, thereby, improve the shelf-life of conductive polymer poly(3,4-ethylenedioxythiophene) (PEDOT)-PSS modified neural electrodes. Control PEDOT-PSS coated microelectrodes demonstrated a significant increase in impedance at 1 kHz after 41–50 days of room temperature storage. Based on equivalent circuit modeling derived from electrochemical impedance spectroscopy, this increase in impedance could be largely attributed to a decrease in the interfacial capacitance consistent with a collapse and closing of the porous structure of the polymeric coating. Time-dependent electrochemical impedance measurements revealed higher stability of the freeze-dried coated microelectrodes compared to the controls, such that impedance values after 41–50 days appeared to be indistinguishable from the initial levels. This suggests that freeze drying PEDOT-PSS coated microelectrodes correlates with enhanced electrochemical stability during shelf storage. Full article

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6121 KiB

Open AccessArticle

In Vivo GFP Knockdown by Cationic Nanogel-siRNA Polyplexes

by Arun R. Shrivats, Yuji Mishina, Saadyah Averick, Krzysztof Matyjaszewski and Jeffrey O. Hollinger

Bioengineering 2015, 2(3), 160-175; https://doi.org/10.3390/bioengineering2030160 - 22 Jul 2015

Cited by 6 | Viewed by 8381

Abstract

RNA interference (RNAi) is a powerful tool to treat diseases and elucidate target gene function. Prior to clinical implementation, however, challenges including the safe, efficient and targeted delivery of siRNA must be addressed. Here, we report cationic nanogel nanostructured polymers (NSPs) prepared by atom transfer radical polymerization (ATRP) for in vitro and in vivo siRNA delivery in mammalian models. Outcomes from siRNA protection studies suggested that nanogel NSPs reduce enzymatic degradation of siRNA within polyplexes. Further, the methylation of siRNA may enhance nuclease resistance without compromising gene knockdown potency. NSP-mediated RNAi treatments against Gapdh significantly reduced GAPDH enzyme activity in mammalian cell culture models supplemented with 10% serum. Moreover, nanogel NSP-mediated siRNA delivery significantly inhibited in vivo GFP expression in a mouse model. GFP knockdown was siRNA sequence-dependent and facilitated by nanogel NSP carriers. Continued testing of NSP/siRNA compositions in disease models may produce important new therapeutic options for patient care. Full article

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Open AccessArticle

Ovarian Cancer Cell Adhesion/Migration Dynamics on Micro-Structured Laminin Gradients Fabricated by Multiphoton Excited Photochemistry

by Ruei-Yu He, Visar Ajeti, Shean-Jen Chen, Molly A. Brewer and Paul J. Campagnola

Bioengineering 2015, 2(3), 139-159; https://doi.org/10.3390/bioengineering2030139 - 16 Jul 2015

Cited by 5 | Viewed by 6002

Abstract

Haptotaxis, i.e., cell migration in response to adhesive gradients, has been previously implicated in cancer metastasis. A better understanding of cell migration dynamics and their regulation could ultimately lead to new drug targets, especially for cancers with poor prognoses, such as ovarian cancer. Haptotaxis has not been well-studied due to the lack of biomimetic, biocompatible models, where, for example, microcontact printing and microfluidics approaches are primarily limited to 2D surfaces and cannot produce the 3D submicron features to which cells respond. Here we used multiphoton excited (MPE) phototochemistry to fabricate nano/microstructured gradients of laminin (LN) as 2.5D models of the ovarian basal lamina to study the haptotaxis dynamics of a series of ovarian cancer cells. Using these models, we found that increased LN concentration increased migration speed and also alignment of the overall cell morphology and their cytoskeleton along the linear axis of the gradients. Both these metrics were enhanced on LN compared to BSA gradients of the same design, demonstrating the importance of both topographic and ECM cues on the adhesion/migration dynamics. Using two different gradient designs, we addressed the question of the roles of local concentration and slope and found that the specific haptotactic response depends on the cell phenotype and not simply the gradient design. Moreover, small changes in concentration strongly affected the migration properties. This work is a necessary step in studying haptotaxis in more complete 3D models of the tumor microenvironment for ovarian and other cancers. Full article

(This article belongs to the Special Issue MEMS/NEMS Fabricated Tissue Scaffolding Devices)

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Bioengineering, Volume 2, Issue 3 (September 2015) – 3 articles , Pages 139-183

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