PC12 Cell Adhesion Research Articles

Potential of Collagen/PLA-based Nanofibrous Scaffold to Support PC12 Cells and Neural Repair

Objective: This study attempts to modify Polylactic Acid (PLA) with the natural polymer Collagen (Coll), to develop materials such as an electrospun scaffold that have better mechanical stability and biocompatibility. Retinoic acid (RA), a bioactive material that promotes nerve growth, is to be added to the nanofiber scaffolds as part of this project.
 Methods: One of the most important methods we employed in this work to create nanofibrous scaffolds was electrospinning.
 Results: The synthesized nanofiber scaffold exhibited a diameter of 255±40 nm and a tensile strength of 175±10.4 N, providing sufficient support for native peripheral nerve repair. The inclusion of Coll enhanced the scaffold's hydrophilic behavior (contact angle: 56±4°), ensuring stability in aqueous solutions. In addition, cell adhesion and proliferation are demonstrated to be improved by PLA composite nanofibers based on Collagen, while PC12 cell adhesion and proliferation are further improved by RA.
 Conclusion: Based on their biodegradability, robust mechanical properties, and porous structure, these scaffolds are excellent choices for nerve tissue engineering, according to our findings. The significant increase in PC12 cells' adhesion and proliferation upon the addition of RA demonstrates the cells' potential for nerve repair.

Metal-Chelating Self-Assembling Peptide Nanofiber Scaffolds for Modulation of Neuronal Cell Behavior.

Synthetic peptides are promising structural and functional components of bioactive and tissue-engineering scaffolds. Here, we demonstrate the design of self-assembling nanofiber scaffolds based on peptide amphiphile (PA) molecules containing multi-functional histidine residues with trace metal (TM) coordination ability. The self-assembly of PAs and characteristics of PA nanofiber scaffolds along with their interaction with Zn, Cu, and Mn essential microelements were studied. The effects of TM-activated PA scaffolds on mammalian cell behavior, reactive oxygen species (ROS), and glutathione levels were shown. The study reveals the ability of these scaffolds to modulate adhesion, proliferation, and morphological differentiation of neuronal PC-12 cells, suggesting a particular role of Mn(II) in cell-matrix interaction and neuritogenesis. The results provide a proof-of-concept for the development of histidine-functionalized peptide nanofiber scaffolds activated with ROS- and cell-modulating TMs to induce regenerative responses.

Bisepoxide-Jeffamine microgel synthesis and application toward heterogeneous surface morphology for differential neuronal/non-neuronal cell responses in vitro

Herein, a new non-vinylic type of cationic microgels (MG) was readily prepared from ethylene glycol diglycidyl ether and Jeffamine T-403 in water. The MG was responsive to both temperature and pH, and oxidatively stable as demonstrated by the hydrogen peroxide study. Using glass as a model substrate, its surface was easily imparted with a heterogeneous morphology by simply adsorbing MG dispersed in basic solution. Specifically, the morphology features patches made of a monolayer of connected yet individually recognizable MG. Through in vitro cell studies, we show that a mere change of the extent of surface coverage by such a patchy morphology can strike a balance in promoting adhesion and differentiation of neuron-like PC-12 cells and primary cortical neurons of chick embryo, without soliciting proliferative response from non-neuronal cells of NIH3T3 fibroblast and CTX astrocyte. This simple yet unconventional surface morphology created by MG could be leveraged in the future as an alternative strategy for neural interface engineering.

Fabrication and characterization of chitosan-based composite scaffolds for neural tissue engineering

With the development of peripheral nerve tissue engineering, study of biodegradable materials have extensive applied prospect. Chitosan (Cs) is a promising candidate for neural tissue engineering due to its similar chemical structure to glycosaminoglycan. However, due to its lack of elasticity and flexibility, Cs often needs to be used in combination with other materials. In this study, three composite scaffolds were prepared by freeze-drying method: Cs/hyaluronic acid (HA)/gelatin (Gel), Cs/collagen (Col), and Cs/polyethylene glycol (PEG). Mechanical properties, swelling behavior, porosity, and conductivity of these materials have been characterized. Compared with pure Cs, the addition of other materials reduced the average pore size, while improved the mechanical properties of the composite scaffold. Furthermore, 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), live/dead staining, cell morphology, and immunofluorescence staining were performed to evaluate the cytotoxicity, biocompatibility, and differentiation of rat pheochromocytoma (PC12) cells on Cs/HA/Gel, Cs/Col, and Cs/PEG composite scaffolds. Our results indicated that all these Cs-based composite scaffolds had good biocompatibility without cytotoxicity, while Cs/PEG scaffolds possessed higher cell survival rate and could promote the adhesion, proliferation, and differentiation of PC12 cells. The Cs-based composite scaffolds developed in this study can serve as promising substitutes for neural tissue regeneration.

Transparent Conductive Silk Film with a PEDOT-OH Nano Layer as an Electroactive Cell Interface.

Bioelectronics based on biomaterial substrates are advancing toward biomedical applications. As excellent conductors, poly(3,4-ethylenedioxythiophene) (PEDOT) and its derivatives have been widely developed in this field. However, it is still a big challenge to obtain a functional layer with a good electroconductive property, transparency, and strong adhesion on the biosubstrate. In this work, poly(hydroxymethyl-3,4-ethylenedioxythiophene) (PEDOT-OH) was chemically polymerized and deposited on the surface of a regenerated silk fibroin (RSF) film in an aqueous system. Sodium dodecyl sulfate (SDS) was used as the surfactant to form micelles which are beneficial to the polymer structure. To overcome the trade-off between transparency and the electroconductive property of the PEDOT-OH coating, a composite oxidant recipe of FeCl3 and ammonium persulfate (APS) was developed. Through electrostatic interaction of oppositely charged doping ions, a well-organized conductive nanoscale coating formed and a transparent conductive RSF/PEDOT-OH film was produced, which can hardly be achieved in a traditional single oxidant system. The produced film had a sheet resistance (Rs) of 5.12 × 104 Ω/square corresponding to a conductivity of 8.9 × 10-2 S/cm and a maximum transmittance above 73% in the visible range. In addition, strong adhesion between PEDOT-OH and RSF and favorable electrochemical stability of the film were demonstrated. Desirable transparency of the film allowed real-time observation of live cells. Furthermore, the PEDOT-OH layer provided an improved environment for adhesion and differentiation of PC12 cells compared to the RSF surface alone. Finally, the feasibility of using the RSF/PEDOT-OH film to electrically stimulate PC12 cells was demonstrated.

Integrated transcriptomic and proteomic study on the different molecular mechanisms of PC12 cell growth on chitosan and collagen/chitosan films.

The purpose of this article is to integrate the transcriptomic analysis and the proteomic profiles and to reveal and compare the different molecular mechanisms of PC12 cell growth on the surface of chitosan films and collagen/chitosan films. First, the chitosan films and the collagen/chitosan films were prepared. Subsequently, the cell viability assay was performed; the cell viability of the PC12 cells cultured on the collagen/chitosan films for 24 h was significantly higher than that on the chitosan films. Then, with cDNA microarray, the numbers of differentially expressed genes of PC12 cells on the surface of chitosan and collagen/chitosan films were 13349 and 5165, respectively. Next, the biological pathway analysis indicated that the differentially expressed genes were involved in 40 pathways directly related to cell adhesion and growth. The integrated transcriptomic and our previous proteomic analysis revealed that three biological pathways—extracellular matrix–receptor interaction, focal adhesion and regulation of actin cytoskeleton—were regulated in the processes of protein adsorption, cell adhesion and growth. The adsorbed proteins on the material surfaces further influenced the expression of important downstream genes by regulating the expression of related receptor genes in these three pathways. In comparison, chitosan films had a strong inhibitory effect on PC12 cell adhesion and growth, resulting in the significantly lower cell viability on its surface; on the contrary, collagen/chitosan films were more conducive to promoting PC12 cell adhesion and growth, resulting in higher cell viability.

Application of electrospun polycaprolactone fibers embedding lignin nanoparticle for peripheral nerve regeneration: In vitro and in vivo study

Lignin displays attractive properties in peripheral nerve applications. Here, aligned polycaprolactone (PCL) fibers with various percentages of lignin nanoparticles were fabricated using the electrospinning method. The morphologies, contact angles, mechanical properties, in vitro degradation, and water uptake of the PCL/lignin fibers were characterized. Cell viability and adhesion of PC12 and human adipose-derived stem cells (hADSCs) were studied employing MTT assay and SEM, respectively. SEM, immunocytochemistry, and Real-Time PCR were utilized to characterize neural differentiation and neurite length of PC12 and hADSCs. To further study on lignin effect on nerve regeneration, in vivo studies were performed. The results indicated that all nanocomposite fibers were smooth and bead-free. With increasing the lignin content, the water contact angle decreased while in vitro degradation, water uptake, and Young's modulus increased compared to the PCL fibers. Cell viability, and differentiation along with neurite length extension were promoted by increasing lignin content. The neural markers expression for differentiated cells were upregulated by the increase of lignin percent. In vivo investigation also demonstrates that sample groups incorporating 15% lignin nanoparticles showed better regeneration among others. Therefore, PCL with 15% of lignin nanoparticles shows great potential to be applied for nerve regeneration.

VPA/PLGA microfibers produced by coaxial electrospinning for the treatment of central nervous system injury

The central nervous system shows limited regenerative capacity after injury. Spinal cord injury (SCI) is a devastating traumatic injury resulting in loss of sensory, motor, and autonomic function distal from the level of injury. An appropriate combination of biomaterials and bioactive substances is currently thought to be a promising approach to treat this condition. Systemic administration of valproic acid (VPA) has been previously shown to promote functional recovery in animal models of SCI. In this study, VPA was encapsulated in poly(lactic-co-glycolic acid) (PLGA) microfibers by the coaxial electrospinning technique. Fibers showed continuous and cylindrical morphology, randomly oriented fibers, and compatible morphological and mechanical characteristics for application in SCI. Drug-release analysis indicated a rapid release of VPA during the first day of the in vitro test. The coaxial fibers containing VPA supported adhesion, viability, and proliferation of PC12 cells. In addition, the VPA/PLGA microfibers induced the reduction of PC12 cell viability, as has already been described in the literature. The biomaterials were implanted in rats after SCI. The groups that received the implants did not show increased functional recovery or tissue regeneration compared to the control. These results indicated the cytocompatibility of the VPA/PLGA core-shell microfibers and that it may be a promising approach to treat SCI when combined with other strategies.

Paper-based 3D culture device integrated with electrochemical sensor for the on-line cell viability evaluation of amyloid-beta peptide induced damage in PC12 cells

In this communication, a paper-based 3D cell culture device integrated with electrochemical biosensor was applied to on-line monitoring of dopamine release from PC12 cell damage models induced by amyloid-beta peptide (Aβ25-35) and cell intervene models protected by curcumin (Cur) and marrow mesenchymal stem cells (MSC) supernatant. The adhesion and proliferation of PC12 cells cultured on the paper scaffold was characterized by scanning electron microscopy and laser scanning confocal microscopy, which verify unique biocompatibility and 3D microarchitecture similar to human body microenvironment of paper substrate, so an artificial model simulating 3D microenvironment in vivo was constructed easily. The PC12 cells in paper-based devices consisted of four groups containing control group, Aβ25-35 group, Aβ25-35+Cur group and Aβ25-35+MSC supernatant group. Under optimal conditions, this proposed device displayed a wide linear range from 0.05 to 1 μmol/L with a detection limit of 0.009 μmol/L (S/N = 3) and exhibited high sensitivity, good selectivity and excellent reproducibility. Furtherly, electrochemcial analysis and MTT assay gave a clue that the cell viability of Aβ25-35+MSCs supernatant group was higher than that of Aβ25-35+Cur group. Therefore, the detachable paper-based 3D device paves the way to a direct detection of exocytosis DA from neuron cells for on-line cell viability evaluation of neurodegenerative disease cell damage models.

Promoting neural cell proliferation and differentiation by incorporating lignin into electrospun poly(vinyl alcohol) and poly(glycerol sebacate) fibers.

Electrospinning of natural and synthetic polymers open a new practical approach to tissue engineering by producing fibers. In this study, aligned electrospun poly(vinyl alcohol) (PVA)-poly(glycerol sebacate) (PGS) fibers with various percentages of lignin (0, 1, 3, and 5%wt) fabricated for nerve tissue engineering. The effect of the different amount of lignin on the morphology and diameter of the fibers was investigated by scanning electron microscopy (SEM). The physicochemical properties of fibers were studied using FTIR, tensile strain, contact angle, water uptake, and degradation test. MTT assay and SEM were employed to evaluate PC12 cell proliferation and adhesion, respectively. Immunocytochemistry and gene expression were utilized to study how the lignin affected on cell differentiation. The results revealed the smooth with a uniform diameter of the fabricated fibers, and the increased amount of lignin reduced the fiber diameter from 530 to 370 nm. The modulus of elasticity increased from 0.1 to 0.4 MPa by increasing the lignin percentage. The PC12 cell culture indicated that the lignin enhanced cell proliferation. The mRNA expression level for Gfap, β-Tub III, and Map2 and immunocytochemistry (Map2) revealed the positive effect of lignin on neural cell differentiation. Finally, the results suggest PVA-PGS/5% lignin as a promising material for nerve tissue engineering.

A comparative study on the shape-dependent biological activity of nanostructured zinc oxide

Monitoring and stimulating in biological systems are strongly dependent on the nature of the interfaces between biological systems and devices; in addition, one-dimensional nanostructures show high-charge accumulation at their surfaces which result in forming a conductive pathway between devices and cells. ZnO nanostructures because of their dual semiconducting properties and their piezoelectricity show a great potential to deploy in optoelectronic devices, biosensors and transducers in biological systems. For this purpose, we introduced a novel one-step hydrothermal nanowire array fabrication and compared it with ZnO nanorods array and ZnO compact film. Grazing incidence X-ray Diffraction (GIXRD), field-emission scanning electron microscope (FE-SEM), disperse X-ray spectroscopy (EDS) detector and inductively couples plasma optical emission spectrometry (ICP-OES) were used for physical and chemical characterizations of the arrays. In addition, we investigated the ability of zinc oxide nanostructures to control cell adhesion and viability of neuron-like PC12 cells. Furthermore, we examined the zinc oxide solubility and our results indicated that cytotoxicity were occurred in 2.23 ± 0.41 µg/ml concentration of zinc ions which was much less than the safe amount of zinc ions (10.23 ± 0.41 µg/ml) reported in previous studies. It is believed that ZnO dissociation behavior crucially affects cell fates even in rare amounts.

Hydroxyapatite coated magnesium alloy for peripheral nerve regeneration

Magnesium (Mg) has been used as a neuroprotective agent and for orthopedic and cardiovascular stent applications for a long time. Mg is a promising material for neural regeneration own to its metallic nature, biodegradability, and biocompatibility. To evaluate the benefit of hydroxyapatite (HA) coated Mg alloy (WE43) nerve conduit in peripheral nerve injury regeneration. In vitro cell adhesion and proliferation of PC12 cells and Schwann cells over pure Mg, WE43, HA coated pure Mg (HA-Mg), and HA coated WE43 (HA-WE43) disks were assessed using scanning electron microscope and EZ-CYTOX assay. In vivo study was also performed for sham, silicone nerve conduits, and HA-WE43 nerve conduits to evaluate rat sciatic nerve regeneration over 10 mm gap. These rats were observed for three months with weekly functional assessment using sciatic functional index. Regeneration was evaluated through retrograde neuron labeling and histomorphometric analysis at the end of the experiment. Non-coated pure Mg and WE43 conduits showed fast resorption rate and high gas formation. Higher adhesion and proliferation of PC12 cells were found in HA-WE43 disks. At the end of three months, HA-WE43 nerve conduit showed mild resorption without detectable gas formation in the surrounding tissue. However, only scanty regenerated neural tissue was found within the conduit. HA-WE43 nerve conduit showed controlled degradation and absence of gas formation with scanty regenerated neural tissue.

A proteomics study to explore the role of adsorbed serum proteins for PC12 cell adhesion and growth on chitosan and collagen/chitosan surfaces.

The aim of this article is to apply proteomics in the comparison of the molecular mechanisms of PC12 cell adhesion and growth mediated by the adsorbed serum proteins on the surfaces of chitosan and collagen/chitosan films. First, the chitosan and the collagen/chitosan films were prepared by spin coating; and their surface morphologies were characterized by scanning electron microscopy, X-ray energy dispersive spectroscopy, contact angle measurement and Fourier transform infrared spectroscopy. Subsequently, cell proliferation experiments on two materials were performed and the dynamic curves of protein adsorption on their surfaces were measured. Then, proteomics and bioinformatics were used to analyze and compare the adsorbed serum proteins on the surfaces of two biomaterials; and their effects on cell adhesion were discussed. The results showed that the optimum concentration of chitosan film was 2% w/v. When compared with chitosan film, collagen/chitosan film promoted the growth and proliferation of PC12 cells more significantly. Although the dynamic curves showed no significant difference in the total amount of the adsorbed proteins on both surfaces, proteomics and bioinformatics analyses revealed a difference in protein types: the chitosan surface adsorbed more vitronectin whereas collagen/chitosan surface adsorbed more fibronectin 1 and contained more cell surface receptor binding sites and more Leu-Asp-Val sequences in its surface structure; the collagen/chitosan surface were more conducive to promoting cell adhesion and growth.

The cellular response of nerve cells on poly-l-lysine coated PLGA-MWCNTs aligned nanofibers under electrical stimulation

Tissue engineering scaffold provide an effective alternative for peripheral nerve repair. Nanofibrous nerve conduits fabricated with various synthetic and natural materials have great potential to support nerve regeneration as a bridge between adjacent ends. The physical, chemical and electrical properties of the scaffolds affect the outcome of nerve regeneration and recovery of function. In this paper, a surface modified, electrically conductive, aligned nanofibrous scaffold composed of poly(lactic-co-glycolic acid) (PLGA) and multi-walled carbon nanotubes (MWCNTs), referred to as L-PC_A was fabricated for nerve regeneration. The morphology, surface chemistry and hydrophilicity of nanofibers were characterized by Scanning Electron Microscopy (SEM), Energy-dispersive X-ray (EDX) and water contact angle, respectively. The mechanical property of the nanofibrous scaffold was also evaluated using a universal materials tester. The effects of these scaffolds on PC12 cell adhesion, proliferation and neuronal differentiation were all evaluated. A hydrophilic surface was created by poly-l-lysine coating, which was able to provide a better environment for cell attachment. Furthermore aligned fibers were proved to be able to guide PC12 cells and DRG neurons growing along the fiber direction and be beneficial for neurite outgrowth. The cellular responses of PC12 cells and DRG neurons on L-PC_A scaffold under electrical stimulation were evaluated by neurofilament proteins expression. As a result, the PC12 cells and DRG neurons stimulated with electrical shock showed longer neurite length, indicating that electrical stimulation with a voltage of 40 mV based on the scaffold with MWCNTs could enhance the neurite extension. Moreover, the cellular response of Schwann cells including cell attachment, proliferation and MBP expression were also enhanced with the synergistic effect of aligned nanofibers and electrical stimulation. In summary, the L-PC_A nanofibrous scaffold supported the cellular response of nerve cells in terms of cell proliferation, differentiation, neurite outgrowth, and myelination in the presence of electrical stimulation, which could be a potential candidate for nerve regeneration application.

A neurotrophic peptide-functionalized self-assembling peptide nanofiber hydrogel enhances rat sciatic nerve regeneration

Nerve guidance conduit (NGC) is a potential alternative to autologous nerve for peripheral nerve regeneration. A promising therapeutic strategy is to modify the nerve guidance conduit intraluminal microenvironment using physical and/or chemical guidance cues. In this study, a neurotrophic peptide-functionalized self-assembling peptide nanofiber hydrogel that could promote PC12 cell adhesion, proliferation, and neuronal differentiation in vitro was prefilled in the lumen of a hollow chitosan tube (hCST) to accelerate axonal regeneration in a rat sciatic nerve defect model. The functionalized self-assembling peptide was developed by introducing a neurotrophic peptide (RGI, RGIDKRHWNSQ) derived from brain-derived neurotrophic factor (BDNF) to the C-terminus of the self-assembling peptide RADA16-I (Ac-(RADA)4-CONH2). Morphological, histological, electrophysiological, and functional analyses demonstrated that the RGI-functionalized, self-assembling, peptide nanofiber hydrogel RAD/RGI could produce a neurotrophic microenvironment that markedly improved axonal regeneration with enhanced re-myelination and motor functional recovery.

Elaboration of Materials with Functionality Gradients by Assembly of Chitosan-Collagen Microspheres Produced by Microfluidics

Biopolymers extracted from renewable resources like chitosan and collagen exhibit interesting properties for the elaboration of materials designed for tissue engineering applications, among which are their hydrophilicity, biocompatibility and biodegradability. In many cases, functional recovery of an injured tissue or organ requires oriented cell outgrowth, which is particularly critical for nerve regeneration. Therefore, there is a growing interest for the elaboration of materials exhibiting functionalization gradients able to guide cells. Here, we explore an original way of elaborating such gradients by assembling particles from a library of functionalized microspheres. We propose a simple process to prepare chitosan-collagen hybrid microspheres by micro- and milli-fluidics, with adaptable dimensions and narrow size distributions. The adhesion and survival rate of PC12 cells on hybrid microspheres were compared to those on pure chitosan ones. Finally, functionalized microspheres were assembled into membranes exhibiting a functionalization gradient.

The Effect of Plasma Treated PLGA/MWCNTs-COOH Composite Nanofibers on Nerve Cell Behavior.

Electrospun nanofibrous scaffolds which can mimic the architecture of the natural extracellular matrix (ECM) are potential candidates for peripheral nerve repair application. Multi-walled carbon nanotubes (MWCNTs) are used in peripheral nerve repair due to their ability to promote neurite extension and support neural network formation. In this study, surface-modified nanofibrous scaffolds composed of poly(lactic-co-glycolic acid) (PLGA) and various ratios of carboxyl-modified MWCNTs (MWCNTs-COOH) (PC0, PC2, PC4 and PC8) were fabricated by electrospinning. The effects of MWCNTs-COOH on the fibers’ morphology, diameter distribution, mechanical properties and surface hydrophilicity were characterized by Scanning Electron Microscopy (SEM), ImageJ software, tensile testing and water contact angle. Furthermore, air plasma treatment was applied to improve the surface hydrophilicity of the scaffolds, and the optimal treatment condition was determined in terms of surface morphology, water contact angle and PC12 cell adhesion. Plasma treated nanofibers (p-PC0, p-PC2, p-PC4 and p-PC8) under optimal treatment conditions were used for further study. PC12 cell proliferation and differentiation were both improved by the addition of MWCNTs-COOH in scaffolds. Additionally, the proliferation and maturation of Schwann cells were enhanced on scaffolds containing MWCNTs-COOH. The neurite outgrowth of rat dorsal root ganglia (DRG) neurons was promoted on MWCNTs-COOH-containing scaffolds, and those cultured on p-PC8 scaffolds showed elongated neurites with a length up to 78.27 μm after 3 days culture. Our results suggested that plasma treated nanofibers under appropriate conditions were able to improve cell attachment. They also demonstrated that plasma treated scaffolds containing MWCNTs-COOH, especially the p-PC8 nanofibrous scaffold could support the proliferation, differentiation, maturation and neurite extension of PC12 cells, Schwann cells and DRG neurons. Therefore, p-PC8 could be a potential candidate for peripheral nerve regeneration application.

Investigation of surface topography and stiffness on adhesion and neurites extension of PC12 cells on crosslinked silica aerogel substrates.

Fundamental understanding and characterization of neural response to substrate topography is essential in the development of next generation biomaterials for nerve repair. Aerogels are a new class of materials with great potential as a biomaterial. In this work, we examine the extension of neurites by PC12 cells plated on matrigel-coated and collagen-coated mesoporous aerogel surfaces. We have successfully established the methodology for adhesion and growth of PC12 cells on polyurea crosslinked silica aerogels. Additionally, we have quantified neurite behaviors and compared their response on aerogel substrates with their behavior on tissue culture (TC) plastic, and polydimethylsiloxane (PDMS). We found that, on average, PC12 cells extend longer neurites on crosslinked silica aerogels than on tissue culture plastic, and, that the average number of neurites per cluster is lower on aerogels than on tissue culture plastic. Aerogels are an attractive candidate for future development of smart neural implants and the work presented here creates a platform for future work with this class of materials as a substrate for bioelectronic interfacing.

Persistent Photoconductivity, Nanoscale Topography, and Chemical Functionalization Can Collectively Influence the Behavior of PC12 Cells on Wide Bandgap Semiconductor Surfaces

Wide bandgap semiconductors such as gallium nitride (GaN) exhibit persistent photoconductivity properties. The incorporation of this asset into the fabrication of a unique biointerface is presented. Templates with lithographically defined regions with controlled roughness are generated during the semiconductor growth process. Template surface functional groups are varied using a benchtop surface functionalization procedure. The conductivity of the template is altered by exposure to UV light and the behavior of PC12 cells is mapped under different substrate conductivity. The pattern size and roughness are combined with surface chemistry to change the adhesion of PC12 cells when the GaN is made more conductive after UV light exposure. Furthermore, during neurite outgrowth, surface chemistry and initial conductivity difference are used to facilitate the extension to smoother areas on the GaN surface. These results can be utilized for unique bioelectronics interfaces to probe and control cellular behavior.

Dual peptide-presenting hydrogels for controlling the phenotype of PC12 cells

Controlling the cell-matrix interaction is a critical factor in the design and fabrication of tissue engineering scaffolds. A particular peptide sequence, Arg-Gly-Asp (RGD peptide), is often used as an adhesion ligand in the engineering of different types of tissues. While in some cases this has been adequate, the use of multiple ligands may be required for the successful engineering of some tissue types. We hypothesized that hydrogels presenting both the RGD peptide and the YIGSR peptide (Tyr-Ile-Gly-Ser-Arg) could successfully regulate the phenotype of PC12 cells, thereby providing a new platform for effective tissue engineering applications. We prepared alginate hydrogels modified with both RGD and YIGSR peptides at several different bulk ligand densities and determined the ways in which PC12 cells can respond to them in vitro. We demonstrate that alginate hydrogels presenting both RGD and YIGSR peptides successfully regulate the proliferation, morphological change, and neuronal differentiation of PC12 cells in vitro. Successful adhesion and proliferation of PC12 cells were dependent on the bulk density of RGD peptides, while neuronal differentiation was significantly enhanced by increasing the YIGSR density. These results suggest that hydrogels presenting multiple adhesion ligands offer many useful applications in tissue engineering approaches.