Nanostructures are often on the same size scale as many biomolecules and biological structures. This makes them readily accessible to these molecules and provides the basis for single-molecule detection. As a result of the quantum confinement, which occurs when the size of a nanostructure or nanocrystal approaches the wavelength of an electron, the optical and electrical properties of the nanomaterial become dependent on their size and thus to a certain level adjustable.

At the Fraunhofer IMS, we are conducting research on these nanoscale materials with a view to their applicability as building blocks in biofunctional sensors. Carbon-based nanomaterials have especially useful properties for this purpose. For example, carbon nanotubes have proven to be an ideal platform for nanosensors. They consist of a rolled-up single layer of carbon (graphene) with a nanoscale cross-section and are therefore often described as "one-dimensional systems". The low dimensionality results in unique physical properties. This way electrons can, for example, only propagate along the axis of the nanotubes. Their optical properties, such as the wavelength at which they can be excited or emit light, can up to a certain degree be tuned by their size. More precisely, the fluorescence properties are directly related to the curvature of the nanotubes and thus their diameter. In addition, the angle at which the carbon layer is rolled up into a tube affects the optical properties. Typically, the tubes have a diameter in the range of up to fifty nanometers and a length of several hundred nanometers. Usually, the nanotubes fluoresce in the near-infrared, a region of light that can penetrate deeper into tissue than visible light. In addition, their small size makes them highly sensitive to change in their immediate environment, which is the basis for detection on a molecular level.

In addition, the nanotubes can be modified modularly which enables the generation of versatile nanosensor structures. They can be chemically modulated that the reversible binding of different analytes to their sensitive surface, changes their optical and electrical properties. For example, fluorescence behavior, such as fluorescence intensity, can change when the nanotubes encounter certain molecules in their environment.

Due to this property, carbon nanotubes can be used to detect a large range of structures: from individual biological signal molecules such as the neurotransmitters dopamine and serotonin, indicators of oxidative stress in plants such as hydrogen peroxide, to proteins, enzymes, viruses and bacteria. Due to their high sensitivity and the fact that the detection is based on the initiation of biochemical processes and therefore takes place in real time, complex biological and chemical systems can be studied in a completely new way. One example is the dynamic imaging of individual chemical signal molecules released from cells with the highest time and spatial resolution. (High-resolution imaging of cellular dopamine efflux using a fluorescent nanosensor array | PNAS, Imaging of Monoamine Neurotransmitters with Fluorescent Nanoscale Sensors - Dinarvand - 2020 - ChemPlusChem - Wiley Online Library). Arrays of fluorescent carbon nanotubes placed under and around neural progenitor cells were used to image the release of the neurotransmitters dopamine and serotonin following chemical stimulation of the cells. Compared to existing analytical methods such as microelectrodes, which are limited to only a few probes per cell and thus cannot capture the spatial and temporal dependence to this extent, carbon nanotube-based sensors allow the influence of cellular morphology on molecule release to be studied. Using the functionalized arrays, such processes were dynamically imaged with a spatial resolution of 20,000 nanosensors per cell and a time resolution of 100 ms.

A different strategy is used to differentiate pathogens: since imaging with high spatial resolution is usually not needed here, but instead specific identification is required, the modular versatility of nanomaterials is used for multiplexing. This means that many differently functionalized nanosensors, which are thus sensitive to different substances, are applied to an array. This way bacteria can be identified by their specific metabolites, which provide a characteristic "fingerprint". (

In addition, quantum defects which are covalently introduced into the carbon lattice have recently been shown to be versatile tools for tuning both, the photophysical properties as well as the surface chemistry of carbon nanotubes (Quantum Defects as a Toolbox for the Covalent Functionalization of Carbon Nanotubes with Peptides and Proteins - Mann - 2020 - Angewandte Chemie International Edition - Wiley Online Library). Until now, these methods have been little explored for functionalization purposes because they usually compromised near-infrared fluorescence. By covalently equipping the nanosensors with biomolecules, it has now been possible to open up completely new application possibilities in the field of biosensors and biomedicine, since it has been possible to preserve fluorescence in the near-infrared.

High resolution imaging

High-resolution imaging of cellular dopamine efflux using a fluorescent nanosensor array.

Imaging of Monoamine Neurotransmitters with Fluorescent Nanoscale Sensors

Dinarvand - 2020 - ChemPlusChem

Quantum Defects

As a Toolbox for the Covalent Functionalization of Carbon Nanotubes with Peptides and Proteins - Mann - 2020 - Angewandte Chemie International Edition - Wiley Online Library.

Remote near infrared identification of pathogens with multiplexed nanosensors

Remote near infrared identification.

Our technologies - Innovations for your products

Biofunctional interfaces

At the  Fraunhofer IMS, biosensors are nanomaterials, which can be used to detect viruses and bacteria, among other things.

Near Infrared Detection

To explore new materials and the structure of biomolecules located on their surface, we use near infrared detection.

Our technology areas - Our technologies for your development

Image Sensors

Development of individual sub-steps up to the complete customer-specific process.

MEMS Technologies

Low temperature processes for post-CMOS integration of MEMS sensors or actuators.

Specialized technologies

The Fraunhofer IMS also offers special technologies e.g. high-temperature technology.


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