Hydrogel Nanosensors for Biophotonic Imaging of Chemical Analytes

H₂O₂ : Hydrogen peroxide; OH: Hydroxyl radical.

Authors and Disclosures

Aniruddha Ray¹ & Raoul Kopelman*<sup>1

1</sup>Department of Chemistry & Biophysics, University of Michigan, 930 N University Avenue, Ann Arbor, MI 48109, USA

Financial & competing interests disclosure
The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.
No writing assistance was utilized in the production of this manuscript.

*Author for correspondence
kopelman@umich.edu

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Executive Summary

Background

• The mapping of chemical analytes that are related to physiological activities within cells and tissues is of great interest; it can contribute to a fundamental understanding of biological systems and can also be applied to disease diagnosis and prognosis.

Nanosensors

• Several types of molecular and polymeric nanoparticle-based indicator probes have been utilized for sensing of chemical analytes. Utilizing the nanoparticle design overcomes some of the inherent drawbacks associated with the traditional 'naked' molecular probes.

• Polyacrylamide (PAA) is a hydrogel polymer with excellent biocompatibility and has been one of the most widely used matrices for chemical nanosensors. The small pores of the PAA matrix allow a flow of ions and small molecules into the matrix containing the indicator probes, but limit probe interactions with other cellular components, thus, preserving the probes' indicating properties, both in vitro and in vivo. Other advantages include noninterference with the proper functioning of the cell, the ability to load multiple agents into the matrix, for ratiometric and/or synergistic operation, as well as specific targeting and easy uptake by cells.

• PAA hydrogel nanosensors have already been utilized successfully for intracellular chemical imaging, with high sensitivity and specificity, of a variety of important analytes, such as oxygen, glucose, pH, free Ca, Na, K and Cl, as well as for various reactive oxygen species. A start has also been made for such chemical/molecular imaging in vivo .

Future Perspective

• Future challenges include targeted subcellular sensing and improving the nanoparticle design towards routine application of these nanosensors in vivo for diagnosing, monitoring and studying diseases, such as cancer, and cardiac and neurodegenerative diseases.