Emergence of two near-infrared windows for in vivo and intraoperative SERS

Abstract

Two clear windows in the near-infrared (NIR) spectrum are of considerable current interest for in vivo molecular imaging and spectroscopic detection. The main rationale is that near-infrared light can penetrate biological tissues such as skin and blood more efficiently than visible light because these tissues scatter and absorb less light at longer wavelengths. The first clear window, defined as light wavelengths between 650nm and 950nm, has been shown to be far superior for in vivo and intraoperative optical imaging than visible light. The second clear window, operating in the wavelength range of 1000-1700nm, has been reported to further improve detection sensitivity, spatial resolution, and tissue penetration because tissue photon scattering and background interference are further reduced at longer wavelengths. Here we discuss recent advances in developing biocompatible plasmonic nanoparticles for in vivo and intraoperative surface-enhanced Raman scattering (SERS) in both the first and second NIR windows. In particular, a new class of 'broad-band' plasmonic nanostructures is well suited for surface Raman enhancement across a broad range of wavelengths allowing a direct comparison of detection sensitivity and tissue penetration between the two NIR window. Also, optimized and encoded SERS nanoparticles are generally nontoxic and are much brighter than near-infrared quantum dots (QDs), raising new possibilities for ultrasensitive detection of microscopic tumors and image-guided precision surgery.

Ultrabright gap-enhanced Raman tags for high-speed bioimaging

“…Single-NP SERS detection raises new potential for multiplexed molecular diagnosis and in vivo Raman spectroscopy and imaging 48–50 . Therefore, we further challenge the sensitivity and the photostability of P-GERTs down to a single-NP level.…”

Near-Infrared-II (NIR-II) Bioimaging via Off-Peak NIR-I Fluorescence Emission

“…These NIR-II organic dyes combined the improved imaging performance as expected at progressively longer imaging wavelengths with the favorable pharmacokinetic excretion profile of small molecules. Besides organic NIR-I/II dyes for NIR-II window bioimaging, ultrasmall luminescent inorganic nanoparticles or nanoclusters, with large surface/volume ratios, tunable and diverse material properties, are potential choices for preclinical/clinical using 73 , 74 . For example, Zhou et al developed ultrasmall Au nanoparticles with efficient renal clearance with not only low RES uptake and high biocompatibility but also passive tumor targeting capability 74 .…”

Recent Advances in Micro-Electro-Mechanical Devices for Controlled Drug Release Applications

“…The proposed device herein sought to improve these aspects by offering a promising and minimally invasive strategy for on-demand and pulsatile drug delivery, based on light activation. Near infrared light wavelength range between 650 and 950 nm (this device used 808 nm), is considered as one of the optical windows in biological tissues, also known as therapeutic windows ( Weissleder, 2001 ; Lane et al, 2018 ). However, the activation process to open the reservoirs could appear uncomfortable for human application, since it supposes the need for a light source localized outside the body.…”