Bioelectronics Bioelectronics l The emerging field of Bioelectronics

Bioelectronics

Bioelectronics l The emerging field of “Bioelectronics” seeks to exploit biology in conjunction with electronics in a wider context encompassing, for example, biomaterials for information processing, information storage, electronic components and actuators.

Bioelectronics l Biomolecules and biological cells can, moreover, be used as the building blocks of higher-level functional devices for recognition or sensing within biosensors. l Bioelectronics research also seeks to use biomolecules to perform the electronic functions that semiconductor devices currently perform.

Bioelectronics l Research activities in both of the following general domains can be distinguished: ¡Micro/Nano-electronics for Life-Sciences, i. e. how micro/nano electronic systems can help to solve important problems in life sciences. l. Examples include integrated devices for detection of cells, DNA, Proteins, and small molecules.

Bioelectronics ¡Life-Sciences for micro/nano electronic systems, i. e. how we can learn from nature to build micro and nano electronic devices. l. Examples include protein mediated electronic devices and neuro-electronic circuitries.

Bioelectronics l One example of a key aspect in bioelectronics research is the interface between biological and electronic materials. l A major challenge in bioelectronics is the patterning of functional components and the interfacing with electrical components.

Bioelectronic interfaces l In the past few years, substantial progress has been made in understanding the interactions between cells and electronic substrates. l Monitoring the electrochemical activity of living cells with electronic sensors represents an emerging technique ranging from basic research in neuroelectronics to various fields of pharmacological analyses.

Electrochemical monitoring in cells l The realization of this approach requires several steps: ¡development and fabrication of electronic devices for the low noise registration of cellular signals ¡development and fabrication of electronic devices for the stimulation of cells, and ¡the effective coupling between the cellular systems and the electronic devices as well as the control over the cellular connections

Electrochemical monitoring in cells l Patterning extracellular matrix proteins and structured surfaces enables the controlled and selective adhesion and growth of cells onto chips, and the realization and investigation of cellular networks of controlled complexity and geometry

Bioelectronic interfaces

NANO AND MICROTECHNOLOGIES OF HYBRID BIOELECTRONIC SYSTEMS

Cell Patterning Approaches • Direct protein lithography • Micro-contact printing/micro fluidics • Proteins • SAMs • Dry lithography • Patterned polymers • Temperature sensitive polymers • Nano-topography • Ordered nano-patterning • Disordered nano-patterning • Wells

Approaches (V) : Nanotopography l Ancient methods l Micro-methods ¡ Silicon pillars ¡ Silicon grass l Nano-methods ¡ Carbon nanotubes

Approaches (V) : Nanotopography Thermally grown Si. O 2 Resist Exposure, development RIE, CHF 3: oxide etch Photoresist removal RIE: Cl 2, BCl 3 Si etch HF: Oxide removal

Approaches (V) : Nanotopography http: //www. hgc. cornell. edu/neupostr/lrie. htm

Approaches (V) : Nanotopography http: //www. wadsworth. org/divisions/nervous/nanobio/DG 06. htm

Approaches (V) : Nanotopography RIE: Cl 2, CF 4, O 2 Photoresist Wet etching: HF, nitric acid, H 2 O Resist removal, Cleaning Craighead

Approaches (V) : Nanotopography LRM 55 Astroglial cells – prefer smooth surfaces Cortical astrocytes – Preferred rough surface

Culture of neural cells on silicon wafers with nano-scale surface topograph l Y. W. Fan et al, “Culture of neural cells on silicon wafers with nanoscale surface topograph” : l Si surfaces with variable roughness (without surface treatment) Morphology of adherent cells remarkably differs on differently rough surfaces

Cells and nanotopography l Cells respond to surface topography l The mechanisms involving cell adhesion and migration on surfaces is poorly understood l Extremely important in the field of tissue engineering and biomaterials l Important in lab-on a chip/micro bio-sensors

Cells React to Nanoscale Order and Symmetry in Their Surroundings A. S. G. Curtis*, N. Gadegaard, M. J. Dalby, M. O. Riehle, C. D. W. Wilkinson, and G. Aitchison

Methods Arrays of nano-pits were prepared in a three -step process: l Electron Beam Lithography l Nickel die fabrication l Hot embossing into polymers

Cell Cultures Primary human fibroblasts (connective tissue cells)/ rat epithenon cells were seeded on patterned PCL or PMMA 1. Short term experiments: measurements taken at intervals from 2 -24 hr 2. Long term experiments: cells cultured for up to 71 days

Human fibroblast cells grown on PCL Adhesion on spaced nanopatterened areas is much lower than on planar areas, but on the smallest closest spaced pits is the same as on the planar area! Rat epitenon cells grown on PCL surfaces for 24 h

Many cells possess surface nanometric features Filopodia and microspikes may be the organelle whose major function is to explore nanofeatures around the cell It is interesting to note that the filopodia follows the nanopattern, and seems to be directed by it

Reaction of cells to different symmetries l 1. 2. Cathrine C. Berry et al, “The influence of microscale topography on fibroblast attachment and motility”: fibroblasts were grown on arrays of pits, 7, 15 and 25 diameter, 20 and 40 mm spacing Cells “prefer” entering the larger diameter pits, meaning they might be sensitive to differences in radius of curvature The smallest pits allow the highest proliferation rate and the highest migration rate of a single cell

Orientation is nonrandom l On orthogonal patterns: cells show preference of 90° separated orientations l On hexagonal patterns: cells show preference of 120° separated orientations

l Fredrick Johansson et al, “Axonal outgrowth on nano-imprinted patterns” l Investigated guidance of axons on patterns of parallel grooves of PMMA, with depths of 300 nm, widths of 100 -400 nm and distance between grooves 100 -1600 nm. -axons display contact guidance on all patterns -preferred to grow on edges and elevations in the patterns rather than in grooves- this may be due to edge effects, as concentration of charges

How cells sense ORDER and SYMMETRY of surfaces? What makes cells adhere to surfaces? Why do differences in diameters and spacing of micro and nano features have such dramatic effect on cell adhesion?

Two possible explanations The effect is caused by the nonliving surfaces alone Nanofeatures are known to affect orientations in nonliving systems It is unknown whether nanofeatures affect protein adsorption on the nanoscale, (exposure to protein rich culture media- showed no difference) The effect is caused by interaction of cellular processes and interfacial forces

Types of nano-topography Ordered conducting grooves Ordered insulating grooves Perturbed ordered insulating grooves Nanofiber topography Random nano-topography insulating substrate Rough conducting substrate

Carbon nanotube based neurochips for engineering and recording of cultured neural networks

Recording from cultured neural networks Ben-Jacob, TAU Gross, UNT Bauman, URos Fromherz, MPI

Multi electrode arrays Large electrically active networks, Long term (weeks), Relevant biological activity BUT Large electrodes, Poor sealing, Average (many neurons) signal, Poor electrode-cell coupling, Random networks E. Ben-Jacob

Multi electrode arrays

l How can we make better/new MEA l How do we manipulate cells on substrates? l Properties of our new MEAs

Cell-substrate interactions Wong et al. Surface chemistry 2004

Nano-topography Craighead, Cornell Hu et al. Mattson et al. J. Mol. Neurosci 2000

Electronic properties (CNTs) zigzag armchair

Carbon nanotube multi-electrode arrays Carbon nanotubes § Biocompatible § Super capacitors § Compatibility with micro fabrication CNT electrodes § Self-cell-organization § Network engineering § Excellent recording

CNT based MEA Mo electrodes SOG passivation RIE etch PDMS stencil CNTs

Engineered Networks Tension competes with adhesion to surface

Neuronal tissue on CNT electrodes

Electrical activity (CNTs) Spontaneous electrical activity

Cell-surface interaction Mo electrode Craighead, Cornell

Summary l CNT are excellent substrates for neuronal growth l Self-organization of neurons l Engineered networks l Very good recording properties

Approaches (V) : Topography Peter Fromherz, Max Planck Institute

Approaches (V) : Topography Fromherz (http: //www. biochem. mpg. de/mnphys/)

CNT FET Bio-sensors

Approaches (V) : Topography

Approaches (V) : Topography

Approaches (VII) : Wells Pine, Caltech

Approaches (VII) : Wells Neuro-wells / neuro-cages Space for neurite growth

Approaches (VI) : Wells

Some technical areas of opportunity for bioelectronics 1. Real-time and massively parallel molecular and cellular characterization for systems biology 2. Biologically-based sensors and fabrication 3. Protection and restoration of health

Challenges l In order to achieve necessary innovations in moving bioelectronics forward, experts in government agencies, academic research institutions, and industry will need to be coordinated and brought to bear in overcome cross-cutting challenges that stem from the lack of technology, biological understanding or a combination of both.

Challenges l Cellular and biomolecular measurements and analyses l Fabrication l Device and material biocompatibility l Power sources