Catalina Vallejo-Giraldo

Biofunctionalisation of electrically conducting polymers

During a single decade of research, evidence has emerged that glial scar formation around the electro-tissue interface drives neural loss and increases the signal impedance of the electrodes, compromising the efficiency of the stimulating systems. Studies with conducting polymers (CPs) as electrode coatings have shown enhanced tissue integration and electrode performance in situ through biochemical and physicomechanical functionalisation. In this review, recent findings on CP modifications are provided in the context of neurospecific biomaterials, shedding light on the valuable impact of multifunctionalised strategies for biomedical applications.

Polyhydroxyalkanoate/carbon nanotube nanocomposites: flexible electrically conducting elastomers for neural applications

AIM Medium chain length-polyhydroxyalkanoate/multi-walled carbon nanotube (MWCNTs) nanocomposites with a range of mechanical and electrochemical properties were fabricated via assisted dispersion and solvent casting, and their suitability as neural interface biomaterials was investigated. MATERIALS & METHODS Mechanical and electrical properties of medium chain length-polyhydroxyalkanoate/MWCNTs nanocomposite films were evaluated by tensile test and electrical impedance spectroscopy, respectively. Primary rat mesencephalic cells were seeded on the composites and quantitative immunostaining of relevant neural biomarkers, and electrical stimulation studies were performed. RESULTS Incorporation of MWCNTs to the polymeric matrix modulated the mechanical and electrical properties of resulting composites, and promoted differential cell viability, morphology and function as a function of MWCNT concentration. CONCLUSION This study demonstrates the feasibility of a green thermoplastic MWCNTs nanocomposite for potential use in neural interfacing applications.

Attenuated Glial Reactivity on Topographically Functionalized Poly(3,4-Ethylenedioxythiophene):P-Toluene Sulfonate (PEDOT:PTS) Neuroelectrodes Fabricated by Microimprint Lithography

Following implantation, neuroelectrode functionality is susceptible to deterioration via reactive host cell response and glial scar-induced encapsulation. Within the neuroengineering community, there is a consensus that the induction of selective adhesion and regulated cellular interaction at the tissue-electrode interface can significantly enhance device interfacing and functionality in vivo. In particular, topographical modification holds promise for the development of functionalized neural interfaces to mediate initial cell adhesion and the subsequent evolution of gliosis, minimizing the onset of a proinflammatory glial phenotype, to provide long-term stability. Herein, a low-temperature microimprint-lithography technique for the development of micro-topographically functionalized neuroelectrode interfaces in electrodeposited poly(3,4-ethylenedioxythiophene):p-toluene sulfonate (PEDOT:PTS) is described and assessed in vitro. Platinum (Pt) microelectrodes are subjected to electrodeposition of a PEDOT:PTS microcoating, which is subsequently topographically functionalized with an ordered array of micropits, inducing a significant reduction in electrode electrical impedance and an increase in charge storage capacity. Furthermore, topographically functionalized electrodes reduce the adhesion of reactive astrocytes in vitro, evident from morphological changes in cell area, focal adhesion formation, and the synthesis of proinflammatory cytokines and chemokine factors. This study contributes to the understanding of gliosis in complex primary mixed cell cultures, and describes the role of micro-topographically modified neural interfaces in the development of stable microelectrode interfaces.

Publisher Correction: Stimulation of 3D osteogenesis by mesenchymal stem cells using a nanovibrational bioreactor

In the version of this Article originally published, in Fig. 4f, the asterisk was missing; in Fig. 6a–c, the labels ‘Wnt/β-catenin signalling’, ‘Wnt/Ca+ pathway’ and ‘ERK’ and their associated lines/arrows were missing; and in Fig. 6d and in the sentence beginning “In MSCs that were...”, ‘myosin’ and ‘nanostimulated’, respectively, were spelt incorrectly. These errors have now been corrected in all versions of the Article.

Electrochemical Analysis of Accelerated Aging of PEDOT-PTS Coated Screen-printed Electrodes

We have developed a deposition method that enhances charge delivery of screen printed electrodes by up to six times through electrochemical deposition of poly (3,4-ethylenedioxythiophene):p-toluenesulfonate (PEDOT-PTS). In order to elucidate the effects of PEDOT-PTS deposition on the long-term electrochemical characterization of screen-printed electrodes we characterized electrode stability with cyclic voltammetry and impedance spectroscopy at room temperature and at 47 °C. A deposition current of 0.4 mA/cm2 guarantees coverage of the working electrode conductive area with no spill of the conductive polymer through the insulating tracks. Control electrodes show charge storage capacity of 0.25 mC. PEDOT-PTS deposited electrodes are stable for over 4 months and present cathodic charge storage capacity of 1.25 mC.