An NIR-IIb emissive transmembrane voltage nano-indicator for the optical monitoring of electrophysiological activities in vivo

In vivo transmembrane-voltage detection reflected the electrophysiological activities of the biological system, which is crucial for the diagnosis of neuronal disease. Traditional implanted electrodes can only monitor limited regions and induce relatively large tissue damage. Despite emerging monitoring methods based on optical imaging have access to signal recording in a larger area, the recording wavelength of less than 1000 nm seriously weakens the detection depth and resolution in vivo. Herein, a Förster resonance energy transfer (FRET)-based nano-indicator, NaYbF4:Er@NaYF4@Cy7.5@DPPC (Cy7.5-ErNP) with emission in the near-infrared IIb biological window (NIR-IIb, 1500-1700 nm) is developed for transmembrane-voltage detection. Cy7.5 dye is found to be voltage-sensitive and is employed as the energy donor for the energy transfer to the lanthanide nanoparticle, NaYbF4:Er@NaYF4 (ErNP), which works as the acceptor to achieve electrophysiological signal responsive NIR-IIb luminescence. Benefiting from the high penetration and low scattering of NIR-IIb luminescence, the Cy7.5-ErNP enables both the visualization of action potential in vitro and monitoring of Mesial Temporal lobe epilepsy (mTLE) disease in vivo. This work presents a concept for leveraging the lanthanide luminescent nanoprobes to visualize electrophysiological activity in vivo, which facilitates the development of an optical nano-indicator for the diagnosis of neurological disorders.

Spin-Vibronic Control of Intersystem Crossing in Iodine-Substituted Heptamethine Cyanines

Spin-orbit coupling between electronic states of different multiplicity can be strongly coupled to molecular vibrations, and this interaction is becoming recognized as an important mechanism for controlling the course of photochemical reactions. Here, we show that the involvement of spin-vibronic coupling is essential for understanding the photophysics and photochemistry of heptamethine cyanines (Cy7), bearing iodine as a heavy atom in the C3' position of the chain and/or a 3H-indolium core, as potential triplet sensitizers and singlet oxygen producers in methanol and aqueous solutions. The sensitization efficiency was found to be an order of magnitude higher for the chain-substituted than the 3H-indolium core-substituted derivatives. Our ab initio calculations demonstrate that while all optimal structures of Cy7 are characterized by negligible spin-orbit coupling (tenths of cm^-1) with no dependence on the position of the substituent, molecular vibrations lead to its significant increase (tens of cm^-1 for the chain-substituted cyanines), which allowed us to interpret the observed position dependence.

Dissolution-enhanced emission of 1,3,6,8-tetrakis(p-benzoic acid)pyrene for selectively detecting protamine and “on-to-on” heparin detection in water

A small molecule TBAPy was used as a turn-on fluorescent probe to selectively detect protamine and heparin based on the dissolution-enhanced emission (DEE) phenomenon.

RNA-targeting low-molecular-weight fluorophores for nucleoli staining: synthesis, in silico modelling and cellular imaging

Herein we present our work on the synthesis, investigation of the photophysical properties, interactions with nucleic acids, molecular docking, and imaging application of three carbocyanine dyes.

Improvement of Photostability and NIR Activity of Cyanine Dye through Nanohybrid Formation: Key Information from Ultrafast Dynamical Studies

Near-infrared (NIR) light harvesting has enormous importance for different potential applications in the modern era of research. Some NIR cyanine dyes such as IR820 have achieved great success in energy harvesting and cancer therapy. However, their action is limited for low photostability, considerable thermal degradation, short circulation times, and nonspecific biodistribution. Our present study is an attempt to overcome such limitations by attaching a model cyanine dye IR820 with ZnO nanoparticles. We prepared an IR820-ZnO nanohybrid and characterized it using microscopic and optical spectroscopic tools. Thermogravimetric analysis depicted greater thermal stability of the IR820-ZnO nanohybrid compared to free dye. We explored the enhancement in the photostability of IR820 upon nanohybrid formation. We detected generation of photoinduced reactive oxygen species (ROS) such as superoxide, singlet oxygen, and so forth using appropriate molecular probes. The formation of IR820-ZnO nanohybrid reduced production of photoinduced singlet oxygen. However, it revealed an alternative trend in overall ROS formation (increases total ROS) under red light illumination. To correlate the enhanced photostability of IR820 on the ZnO surface, we explored excited-state dynamical processes at the interface in nanohybrids. We illustrated the photoinduced excited-state electron-transfer process from the lowest unoccupied molecular orbital of IR820 to the conduction band of ZnO. This photoelectron-transfer process enhances the production of ROS and decreases the formation of singlet oxygen that altogether leads to improvement in photostability and overall activity. A quencher of singlet oxygen sodium azide (NaN₃) was used to further confirm the direct association of singlet oxygen generation with the photostability issue of IR820. Also, ZnO is able to deliver the dye selectively in acidic environment, which suggests its diseased site-specific targeted activity. Our results provide promising improvement for potential use of IR820 through formation of a nanohybrid that could be translated for other NIR cyanine dyes.