Repeating Spatial-Temporal Motifs of CA3 Activity Dependent on Engineered Inputs from Dentate Gyrus Neurons in Live Hippocampal Networks.

Anatomical and behavioral studies, and in vivo and slice electrophysiology of the hippocampus suggest specific functions of the dentate gyrus (DG) and the CA3 subregions, but the underlying activity dynamics and repeatability of information processing remains poorly understood. To approach this problem, we engineered separate living networks of the DG and CA3 neurons that develop connections through 51 tunnels for axonal communication. Growing these networks on top of an electrode array enabled us to determine whether the subregion dynamics were separable and repeatable. We found spontaneous development of polarized propagation of 80% of the activity in the native direction from DG to CA3 and different spike and burst dynamics for these subregions. Spatial-temporal differences emerged when the relationships of target CA3 activity were categorized with to the number and timing of inputs from the apposing network. Compared to times of CA3 activity when there was no recorded tunnel input, DG input led to CA3 activity bursts that were 7× more frequent, increased in amplitude and extended in temporal envelope. Logistic regression indicated that a high number of tunnel inputs predict CA3 activity with 90% sensitivity and 70% specificity. Compared to no tunnel input, patterns of >80% tunnel inputs from DG specified different patterns of first-to-fire neurons in the CA3 target well. Clustering dendrograms revealed repeating motifs of three or more patterns at up to 17 sites in CA3 that were importantly associated with specific spatial-temporal patterns of tunnel activity. The number of these motifs recorded in 3 min was significantly higher than shuffled spike activity and not seen above chance in control networks in which CA3 was apposed to CA3 or DG to DG. Together, these results demonstrate spontaneous input-dependent repeatable coding of distributed activity in CA3 networks driven by engineered inputs from DG networks. These functional configurations at measured times of activation (motifs) emerge from anatomically accurate feed-forward connections from DG through tunnels to CA3

Guided Wave Resonant Optical Structures and LED Micro Resonators for Biosensing Applications

Integrated opto-electronic and nanophotonic devices for sensing application in the fields of medicine, microbiology, environmental, safety and defense have attracted considerable attention due to their potential for achieving greater compactness, shorter response times and higher sensitivities as compared to non-optical sensing systems. Optical cavity resonant devices such as Fabry--Perot interferometers have been extensively used in lasing applications and optical sensing has been accomplished through many similar technologies.;Fiber optic and planar waveguide based resonant devices which use evanescent waves for detection of refractive index changes are one of the most widely used approaches for photonic sensors. In this work we investigate the simulations, fabrication and characterization of resonant optical cavity devices for sensing applications. Morphology Dependent Resonances (MDRs) of planar, micro-spherical and micro-cylindrical cavities were reviewed for resonance line widths, spacing between modes, and density of resonances and experimental observations of internal and external field distributions. We focus on planar thin film stacked resonant waveguide geometries, microsphere-waveguide coupled resonances, cylindrical Gallium Nitride (GaN) microdisks for passive detection of Whispering Gallery Modes (WGMs) and electrically pumped active Resonant Cavity (RC) LED disk geometries for Vertical Cavity Modes (VCMs) as structures of interest.;Advances in stacked thin film coupled waveguide sensors enhance the selectivity and sensitivity by measuring the changes of the resonant optical modes and provide an integrated platform for label-free molecular detection. The effective surface loading detection sensitivity of the planar coupled alumina waveguide transducer was determined to be 20 pg/mm2 with a bulk index sensitivity of 5.6x10-4 Refractive Index Units (RIU) for aqueous sucrose solutions. For circular geometry based resonators, as the physical device size approaches the wavelength of light the MDRs are enhanced by retaining longer photon path length times and enhancing detection due to its high Q factors. Circular micro-cavities not only modify the optical resonances but also distribute the resonant frequencies as compared to a planar macro-cavity. The waveguide-coupled microspheres were experimentally detected to have a minimum surface coverage limit of 0.192%. Passive WGMs in GaN micro-disks showed a variation in mode spacing of 3nm to 7nm (lambda2/2piRn) as disk radius was reduced from 4.5microm to 2microm. Micro-cylindrical Distributed Bragg Reflector (DBR) RCLEDs were designed for layer thicknesses and Multi Quantum Well (MQW) placement to enhance VCMs and LED emission output. Experimental and simulated LED spectral minima matched at 432 nm and 451 nm confirming VCMs related to (lambda/2) cavity resonances

Molecular communication networks with general molecular circuit receivers

In a molecular communication network, transmitters may encode information in concentration or frequency of signalling molecules. When the signalling molecules reach the receivers, they react, via a set of chemical reactions or a molecular circuit, to produce output molecules. The counts of output molecules over time is the output signal of the receiver. The aim of this paper is to investigate the impact of different reaction types on the information transmission capacity of molecular communication networks. We realise this aim by using a general molecular circuit model. We derive general expressions of mean receiver output, and signal and noise spectra. We use these expressions to investigate the information transmission capacities of a number of molecular circuits

A portable device for time-resolved fluorescence based on an array of CMOS SPADs with integrated microfluidics

[eng] Traditionally, molecular analysis is performed in laboratories equipped with desktop instruments operated by specialized technicians. This paradigm has been changing in recent decades, as biosensor technology has become as accurate as desktop instruments, providing results in much shorter periods and miniaturizing the instrumentation, moving the diagnostic tests gradually out of the central laboratory. However, despite the inherent advantages of time-resolved fluorescence spectroscopy applied to molecular diagnosis, it is only in the last decade that POC (Point Of Care) devices have begun to be developed based on the detection of fluorescence, due to the challenge of developing high-performance, portable and low-cost spectroscopic sensors. This thesis presents the development of a compact, robust and low-cost system for molecular diagnosis based on time-resolved fluorescence spectroscopy, which serves as a general-purpose platform for the optical detection of a variety of biomarkers, bridging the gap between the laboratory and the POC of the fluorescence lifetime based bioassays. In particular, two systems with different levels of integration have been developed that combine a one-dimensional array of SPAD (Single-Photon Avalanch Diode) pixels capable of detecting a single photon, with an interchangeable microfluidic cartridge used to insert the sample and a laser diode Pulsed low-cost UV as a source of excitation. The contact-oriented design of the binomial formed by the sensor and the microfluidic, together with the timed operation of the sensors, makes it possible to dispense with the use of lenses and filters. In turn, custom packaging of the sensor chip allows the microfluidic cartridge to be positioned directly on the sensor array without any alignment procedure. Both systems have been validated, determining the decomposition time of quantum dots in 20 nl of solution for different concentrations, emulating a molecular test in a POC device.[cat] Tradicionalment, l'anàlisi molecular es realitza en laboratoris equipats amb instruments de sobretaula operats per tècnics especialitzats. Aquest paradigma ha anat canviant en les últimes dècades, a mesura que la tecnologia de biosensor s'ha tornat tan precisa com els instruments de sobretaula, proporcionant resultats en períodes molt més curts de temps i miniaturitzant la instrumentació, permetent així, traslladar gradualment les proves de diagnòstic fora de laboratori central. No obstant això i malgrat els avantatges inherents de l'espectroscòpia de fluorescència resolta en el temps aplicada a la diagnosi molecular, no ha estat fins a l'última dècada que s'han començat a desenvolupar dispositius POC (Point Of Care) basats en la detecció de la fluorescència, degut al desafiament que suposa el desenvolupament de sensors espectroscòpics d'alt rendiment, portàtils i de baix cost. Aquesta tesi presenta el desenvolupament d'un sistema compacte, robust i de baix cost per al diagnòstic molecular basat en l'espectroscòpia de fluorescència resolta en el temps, que serveixi com a plataforma d'ús general per a la detecció òptica d'una varietat de biomarcadors, tancant la bretxa entre el laboratori i el POC dels bioassaigs basats en l'anàlisi de la pèrdua de la fluorescència. En particular, s'han desenvolupat dos sistemes amb diferents nivells d'integració que combinen una matriu unidimensional de píxels SPAD (Single-Photon Avalanch Diode) capaços de detectar un sol fotó, amb un cartutx microfluídic intercanviable emprat per inserir la mostra, així com un díode làser UV premut de baix cost com a font d'excitació. El disseny orientat a la detecció per contacte de l'binomi format pel sensor i la microfluídica, juntament amb l'operació temporitzada dels sensors, permet prescindir de l'ús de lents i filtres. Al seu torn, l'empaquetat a mida de l'xip sensor permet posicionar el cartutx microfluídic directament sobre la matriu de sensors sense cap procediment d'alineament. Tots dos sistemes han estat validats determinant el temps de descomposició de "quantum dots" en 20 nl de solució per a diferents concentracions, emulant així un assaig molecular en un dispositiu POC

Potential of microfluidics and lab-on-chip platforms to improve understanding of 'prion-like' protein assembly and behavior

Human aging is accompanied by a relevant increase in age-associated chronic pathologies, including neurodegenerative and metabolic diseases. The appearance and evolution of numerous neurodegenerative diseases is paralleled by the appearance of intracellular and extracellular accumulation of misfolded proteins in affected brains. In addition, recent evidence suggests that most of these amyloid proteins can behave and propagate among neural cells similarly to infective prions. In order to improve understanding of the seeding and spreading processes of these 'prion-like' amyloids, microfluidics and 3D lab-on-chip approaches have been developed as highly valuable tools. These techniques allow us to monitor changes in cellular and molecular processes responsible for amyloid seeding and cell spreading and their parallel effects in neural physiology. Their compatibility with new optical and biochemical techniques and their relative availability have increased interest in them and in their use in numerous laboratories. In addition, recent advances in stem cell research in combination with microfluidic platforms have opened new humanized in vitro models for myriad neurodegenerative diseases affecting different cellular targets of the vascular, muscular, and nervous systems, and glial cells. These new platforms help reduce the use of animal experimentation. They are more reproducible and represent a potential alternative to classical approaches to understanding neurodegeneration. In this review, we summarize recent progress in neurobiological research in 'prion-like' protein using microfluidic and 3D lab-on-chip approaches. These approaches are driven by various fields, including chemistry, biochemistry, and cell biology, and they serve to facilitate the development of more precise human brain models for basic mechanistic studies of cell-to-cell interactions and drug discovery