New molecular device that can do Record and manipulate its surrounding bioelectric field

Significance 

Bioelectricity, the current that flows between our cells, is fundamental to our ability to think and talk and walk. In addition, there is a growing body of evidence that recording and altering the bioelectric fields of cells and tissue plays a vital role in wound healing and even potentially fighting diseases like cancer and heart disease. Now, for the first time, researchers at the USC Viterbi School of Engineering have created a molecular device that can do both: Record and manipulate its surrounding bioelectric field. The triangle-shaped device is made of two small, connected molecules—much smaller than a virus and similar to the diameter of a DNA strand.

It’s a completely new material for “reading and writing” the electric field without damaging nearby cells and tissue. Each of the two molecules, linked by a short chain of carbon atoms, has its own separate function: One molecule acts as a “sensor” or detector that measures the local electric field when triggered by red light; a second molecule, “the modifier,” generates additional electrons when exposed to blue light. Notably, each function is independently controlled by different wavelengths of light. The work, published in the Journal of Materials Chemistry C, was spearheaded by USC Viterbi professors Andrea Armani and Rehan Kapadia. The Armani Lab was responsible for creating the new organic molecule, while the Kapadia Lab played a key role in testing how efficiently the “modifier” was generating electricity when activated by light.

Because the reporter molecule can insert into tissue, it has the possibility to measure electric fields non-invasively, providing ultra-fast, 3D, high-resolution imaging of neural networks. This can play a crucial role for other researchers testing the effects of new drugs, or changes in conditions like pressure and oxygen. Unlike many other previous tools, it will do so without damaging healthy cells or tissue or requiring genetic manipulation of the system.

The new multi-functional imaging agent is compatible with existing microscopes so it will enable a wide range of researchers—from biology to neuroscience to physiology—to study biological systems and their response to different stimuli: Drugs and environmental factors. The new frontiers are endless. In addition, the modifier molecule, by altering the nearby electric field of cells, can precisely damage a single point, allowing future researchers to determine the cascading effects throughout, say, an entire network of brain cells or heart cells.

One of the key challenges in designing multifunctional molecules is reducing the cross-talk between the different excitation mechanisms. This type of interference can reduce the overall system efficiency and performance.19,20 With recent advances in machine learning and computational design algorithms, material chemists are able to optimize molecular designs accelerating experimental efforts

The authors developed and characterized an all-optical multifunctional molecular device designed to simultaneously sense and modulate electric fields. The molecule, named as NAI–TPE-PyS, is comprised of two non-interacting modules that are tethered together by a non-interacting spacer. The sensor module is derived from tetraphenylethylene (TPE), which is a two-photon (2p) fluorophore that is excited in the near-IR (NIR). The modulator module is an organic photoconductor, naphthalimide (NAI), whose resistivity can be tuned using an ultraviolet optical source. The non-interacting alkyl chain does not affect the photophysical properties of the modules but rather reduces Dexter energy transfer between modules by physical spacing.

In summary, the multifunctional molecular device, NAI–TPE-PyS, has been successfully designed, synthesized, and characterized. Electric field sensing and modulation abilities are derived from its two covalently coupled modules: a TPE-derived module connected by an alkyl chain to an NAI-derived module. To prove the potential of NAI–TPE-PyS as a multifunctional electric field molecular probe, the photophysical and optoelectronic properties have been investigated experimentally and theoretically.

The TPE-module is designed for voltage imaging where the TPE core is the donor and is conjugated with a pyridinium inner salt (Py+SO3−) serving as the acceptor, forming the D–π–A backbone required by a PeT dye. The module exhibits a broad absorption profile and a solvent-dependent emission owing to the intramolecular charge transfer between the donor and acceptor. The CT-component of the excited state has been further confirmed through theoretical calculations. In addition, the module displays two-photon excited emission upon NIR irradiation. Photo-induced current is observed when the module is actuated with UV illumination, which results from hole-electron generation and transportation within the NAI moieties.

The new study provides a new strategy for developing multifunctional molecules by synergistically combining the emerging fields of small molecule photoconductors and small molecule multi-photon fluorophores. In the future, the multifunctional molecule demonstrated here could prove to be a valuable tool in understanding the complex field of bioelectricity and in designing integrated optoelectronic quantum circuits.

New molecular device that can do Record and manipulate its surrounding bioelectric field - Advances in Engineering

About the author

Andrea Martin Armani is the Ray Irani Chair in Engineering and Materials Science and Professor of Chemical Engineering and Materials Science at the USC Viterbi School of Engineering. She was awarded the 2010 Presidential Early Career Award for Scientists and Engineers from Barack Obama and is a World Economic Forum Young Global Leader.

The over-arching mission of the research group is to develop novel nonlinear materials and integrated optical devices that can be used in understanding disease progression and in quantum optics. As part of these efforts, we have numerous collaborations in tool and technology development to enable research and discovery across a wide range of fields.

Reference

Yingmu Zhang, Jinghan He, Patrick J. G. Saris, Hyun Uk Chae, Subrata Das, Rehan Kapadia and Andrea M. Armani. Multifunctional photoresponsive organic molecule for electric field sensing and modulation, Journal of Materials Chemistry C (2021). DOI: 10.1039/D1TC05065F

Go To Journal of Materials Chemistry C

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