Advances in optical and electrochemical techniques for biomedical imaging

Yi-Tao Long and Thomas J. Meade introduce the Chemical Science retrospective themed collection on advances in optical and electrochemical techniques for biomedical imaging.

As the agship journal of the Royal Society of Chemistry, this retrospective themed collection in Chemical Science collects some exceptionally signicant and highly representative publications from the imaging eld.The types of articles include both edge articles and minireviews, mainly covering optical imaging (for minireviews please see ref. 1-3) and electrochemical imaging (for a minireview please see ref. 4).
Optical methods serve as widely practicable techniques for biological imaging.Fluorescence in the NIR region (>700 nm) is superior in biomedical sensing due to the high penetration depths and low autouorescence interference.To make this technique more applicable for in vivo detection, novel biocompatible uorescent probes with high selectivity and sensitivity are urgently needed in this eld.This motivation drives various new strategies in molecular design.
For example, a small molecule NIR uorescent probe, ACy7, was designed for the in situ visualization of ozone in the brains of mice, which incorporates a Cy7like molecule as the precursor of the uorophore and 3-butenyl as the recognition group. 5The plasma membrane could be specically imaged by a water-soluble near-infrared (NIR)-emissive uorescent molecule with aggregation-induced emission (AIE). 6This uorescent "lightup" probe allows a short staining period (at the second-level) with a wash-free process.Further, a uorophore-peptide conjugate was developed for tumor imaging in the "transparent" nearinfrared II (NIR-II) window with rapid renal excretion and low off-target tissue exposure. 7Meanwhile, a semiconducting polymer nanoparticle is designed for efficient NIR-II image-guided tumor surgery by using multiple pathological models. 8These methods promote clinical translation in disease diagnosis and surgical treatment.We are pleased to see that machine learning has been involved in predicting material properties, 9 and could be expected to facilitate the design of novel uorescence probes.
In addition, new highly sensitive optical methods have been developed for sensing and imaging.For example, a unique hand-held surface enhanced spatially offset resonance Raman spectroscopy (SESORRS) has been reported.This technique has the ability to yield enhanced Raman signals at a far greater sub-surface level for non-invasive detection of cancerous tumors. 10To achieve 3D chemical imaging of a complete organ, a high throughput infrared microscopy method was established by combining Xray tomography and subsequent data analysis. 11oreover, optoacoustic imaging has been proven to be a new sensing method capable of deep penetration with a higher spatial resolution compared to uorescence imaging.In addition, a library screening approach was utilized to identify and evaluate the available dyes for multi-spectral optoacoustic tomography (MSOT) imaging. 12egarding the study of enantiomers, polarized X-rays provide an original approach for the investigation of chirality and symmetry in single crystals.This exible technique based on an anion exchange strategy was proposed for the enantiomeric resolution of an extended metal atom chain (EMAC). 13o promote the fundamental understanding of single entities, electrochemistry shows remarkable advances in the development of various electrochemical microcopy techniques.Specically, the electrochemical impedance spectroscopy of individual nanoparticles was imaged on a dark-eld microscope with an optical-to-electrochemical conversion. 14ccordingly, the electrocatalytic activity of 2D materials could be imaged directly by electrochemiluminescence microscopy (ECL), presenting nonuniform ECL distribution at single particles. 15ECL microscopy could facilitate the imaging and study of electrochemistry collision behavior of single ECL nano-emitters. 16ince the design of new ECL emitters has attracted growing interest, a new nearinfrared aggregation-induced enhanced ECL emitter has been developed that shows high ECL efficiency and excellent rsc.li/chemical-science biocompatibility. 17The thriving research on nanoscale electrochemistry will likely accelerate the exploration of new chemistry through single entities.
As guest editors of this themed collection, we thank all the authors for their outstanding contributions.We have brought together high-quality articles on the theme of imaging, especially optical and electrochemical imaging, in this themed collection.We hope researchers from various elds will enjoy examining this themed collection.