Extending the spectral database of laser-induced breakdown spectroscopy with generative adversarial nets.

As a famous spectroscopy method for substance detection and classification, laser-induced breakdown spectroscopy (LIBS) is not a nondestructive detection method. Considering the precious samples and the experimental environment, sometimes it is difficult to get enough spectra to build the classification model, which is important for qualitative analysis. In this paper, a spectral generation method for extending the spectral database of LIBS is proposed based on generative adversarial nets (GAN). After enough interactive training, the generated spectra looked very similar to the experimental spectra. Evaluated with unsupervised clustering methods PCA and K-means, the generated spectra could not be distinguished from the real spectra. For each type of sample, most of the simulated spectra and experimental spectra were clustered into the same class, which meant the proposed method was effective to extend the spectral database. Using the spectral database extended by this method as training set data to build the SVM model, the results showed that when there were only a few experimental spectra, the combination of the generated spectra and the experimental spectra for building the classification model could achieve better identification results.

Meningeal inflammatory response and fibrous tissue remodeling around intracortical implants: An in vivo two-photon imaging study.

Meningeal inflammation and encapsulation of neural electrode arrays is a leading cause of device failure, yet little is known about how it develops over time or what triggers it. This work characterizes the dynamic changes of meningeal inflammatory cells and collagen-I in order to understand the meningeal tissue response to neural electrode implantation. We use in vivo two-photon microscopy of CX3CR1-GFP mice over the first month after electrode implantation to quantify changes in inflammatory cell behavior as well as meningeal collagen-I remodeling. We define a migratory window during the first day after electrode implantation hallmarked by robust inflammatory cell migration along electrodes in the meninges as well as cell trafficking through meningeal venules. This migratory window attenuates by 2 days post-implant, but over the next month, the meningeal collagen-I remodels to conform to the surface of the electrode and thickens. This work shows that there are distinct time courses for initial meningeal inflammatory cell infiltration and meningeal collagen-I remodeling. This may indicate a therapeutic window early after implantation for modulation and mitigation of meningeal inflammation.

Enhancing surface immobilization of bioactive molecules via a silica nanoparticle based coating.

Surface modification is of significant interest in biomaterials, biosensors, and device biocompatibility. Immobilization of bioactive or biomimetic molecules is a common method of disguising a foreign body as host tissue to decrease the foreign body response (FBR) and/or increase device-tissue integration. For example, in neural interfacing devices, immobilization of L1, a neuron-specific adhesion molecule, has been shown to increase neuron adhesion and reduce inflammatory gliosis on and around the implants. However, the activity of modified surfaces is limited by the relatively low concentration of the immobilized component, in part due to the low surface area of flat surfaces available for modification. In this work, we demonstrate a novel method for increasing the device surface area by attaching a layer of thiolated silica nanoparticles (TNPs). This coating method results in an almost two-fold increase in the immobilized L1 protein. L1 immobilized nanotextured surfaces showed a 100% increase in neurite outgrowth than smooth L1 immobilized surfaces without increasing the adhesion of astrocytes in vitro. The increased bioactivity observed in the cell assay was determined to be mainly due to the higher protein surface density, not the increase in surface roughness. In addition, we tested immobilization of a superoxide dismutase mimic (SODm) on smooth and roughened substrates. The SODm immobilized rough surfaces demonstrated an increase of 145% in superoxide scavenging activity compared to chemically matched smooth surfaces. These results not only show promise in improving biomimetic coating for neural implants, but may also improve surface immobilization efficacy in other fields such as catalysts, protein purification, sensors, and tissue engineering devices.

A graphene oxide/conducting polymer nanocomposite for electrochemical dopamine detection: origin of improved sensitivity and specificity.

Neuromodulatory dopamine (DA) acts as an essential signaling molecule in the central nervous system (CNS), and its dysfunction has been implicated in neurological disorders such as Parkinson's disease and schizophrenia. Due to its inherent redox properties, DA can be detected electrochemically by monitoring changes in current as the molecule is oxidized. Many electrode materials for electrochemical detection have been developed to monitor DA, but properties such as sensitivity and specificity must be optimized. We describe a conducting polymer (CP) nanocomposite of poly(3,4-ethylendioxythiophene) (PEDOT) doped with GO nanosheets, and report its superior DA detection performance over bare glassy carbon electrode (GCE) substrates. The GO/PEDOT electrode exhibits favorable electrical properties such as lowered impedance and increased charge storage capacity. The nanocomposite demonstrates improved sensitivity to the oxidation of DA at its surface. Meanwhile, interference from competing analyte, ascorbic acid (AA), is minimized. Mechanistic studies indicate that electrostatic interactions drive the increased sensitivity toward DA, and improved electrocatalysis of AA oxidation by the nanocomposite enables the selective discrimination of DA signals from those of AA. The described performance of the GO/PEDOT nanocomposite accentuates its promise for improving detection capabilities of electrochemical biosensors for the accurate and reliable detection of DA signals in biological samples.

Neurorestorative effect of urinary bladder matrix-mediated neural stem cell transplantation following traumatic brain injury in rats.

Traumatic brain injury (TBI) is a leading cause of cell death and disability among young adults and lacks a successful therapeutic strategy. The multiphasic injuries of TBI severely limit the success of conventional pharmacological approaches. Recent successes with transplantation of stem cells in bioactive scaffolds in other injury paradigms provide new hope for the treatment of TBI. In this study, we transplanted neural stem cells (0.5x10(5) cells/µl) cultured in a bioactive scaffold derived from porcine urinary bladder matrix (UBM; 4 injection sites, 2.5µl each) into the rat brain following controlled cortical impact (CCI, velocity, 4.0 m/sec; duration, 0.5 sec; depth, 3.2mm). We evaluated the effectiveness of this strategy to combat the loss of motor, memory and cognitive faculties. Before transplantation, compatibility experiments showed that UBM was able to support extended proliferation and differentiation of neural stem cells. Together with its reported anti-inflammatory properties and rapid degradation characteristics in vivo, UBM emerged to be an ideal scaffold. The transplants reduced neuron/tissue loss and white matter injury, and also significantly ameliorated motor, memory, and cognitive impairments. Furthermore, exposure to UBM alone was sufficient to decrease the loss of sensorimotor skills from TBI (examined 3-28 days post-CCI). However, only UBMs that contained proliferating neural stem cells helped attenuate memory and cognitive impairments (examined 26-28 days post-CCI). In summary, these results demonstrate the therapeutic efficacy of stem cells in bioactive scaffolds against TBI and show promise for translation into future clinical use.

In vivo effects of L1 coating on inflammation and neuronal health at the electrode-tissue interface in rat spinal cord and dorsal root ganglion.

The spinal cord (SC) and dorsal root ganglion (DRG) are target implantation regions for neural prosthetics, but the tissue-electrode interface in these regions is not well-studied. To improve understanding of these locations, the tissue reactions around implanted electrodes were characterized. L1, an adhesion molecule shown to maintain neuronal density and reduce gliosis in brain tissue, was then evaluated in SC and DRG implants. Following L1 immobilization onto neural electrodes, the bioactivities of the coatings were verified in vitro using neuron, astrocyte and microglia cultures. Non-modified and L1-coated electrodes were implanted into adult rats for 1 or 4 weeks. Hematoxylin and eosin staining along with cell-type specific antibodies were used to characterize the tissue response. In the SC and DRG, cells aggregated at the electrode-tissue interface. Microglia staining was more intense around the implant site and decreased with distance from the interface. Neurofilament staining in both locations decreased or was absent around the implant, compared with surrounding tissue. With L1, neurofilament staining was significantly increased while neuronal cell death decreased. These results indicate that L1-modified electrodes may result in an improved chronic neural interface and will be evaluated in recording and stimulation studies.

Rapid modulation of local neural activity by controlled drug release from polymer-coated recording microelectrodes.

We demonstrate targeted perturbation of neuronal activity with controlled release of neurochemicals from conducting polymer-coated microelectrodes. Polymer coating and chemical incorporation are achieved through individually addressable electrodeposition, a process that does not compromise the recording capabilities of the electrodes. Release is realized by the application of brief voltage pulses that electrochemically reduce the polymer and dissociate incorporated neurochemicals; whereby they can diffuse away and achieve locally effective concentrations. Inhibition of evoked synaptic currents in neurons within 200 µm of a 6-cyano-7-nitroquinoxaline-2,3-dione releasing electrode lasts for several seconds. Spiking activity of neurons in local circuits recorded extracellularly near the releasing electrode is silenced for a similar duration following release. This methodology is compatible with many neuromodulatory chemicals and various recording electrodes, including in vitro and implantable neural electrode arrays, thus providing an inexpensive and accessible technique capable of achieving sophisticated patterned chemical modulation of neuronal circuits.