Near‐Infrared Fluorescent Nanomaterials for Bioimaging and Sensing

Abstract

A great challenge in noninvasive biomedical imaging is the acquisition of images inside a biological system at the cellular level. Common modalities used today such as magnetic resonance or computed tomography imaging have the advantage that any part of a living organism can be imaged at any depth, but are limited to millimeter resolution and can usually not be employed e.g., for surgical guidance. Optical imaging techniques offer resolution on the 100 nanometer scale, but are limited by the strong attenuation of visible light by biological matter and are traditionally used to image on the surface. Near‐infrared light in the “biological windows” can penetrate much deeper into biological samples, rendering fluorescence‐based imaging a viable alternative. In the past two decades, many fluorescent nanomaterials have been developed to operate in the near infrared, yet only few materials emitting above 1000 nm exist and none are approved for clinical use. This review describes recent advances in the development and use of near‐infrared fluorescent nanomaterials for biomedical imaging and sensing applications. The physical and chemical properties as well as the bioconjugation and application of materials such as organic fluorophores, semiconductor quantum dots, carbon‐based materials, rare earth materials, and polymer particles are discussed.

Not All Fluorescent Nanodiamonds Are Created Equal: A Comparative Study

“…This is noteworthy as it sets HPHT nanodiamonds apart from the almost spherical 3–6 nm sized primary particles found in detonation nanodiamonds . It also differentiates them from many other types of fluorescent nanomaterials, such as semiconductor quantum dots, polymer NPs, or lanthanide‐based upconversion NPs, all of which show highly regular or spherical shapes . Histograms of the particle sizes and aspect ratios of the particles investigated in the p + sample (50 particles in total) are plotted in Figure B,C and show a wide distribution of both parameters.…”

Glass and Process Development for the Next Generation of Optical Fibers: A Review

“…However, the majority of NCs that can be made via alternative synthesis methods cannot be grown in-situ in glass. For example, it is not possible to grow nanodiamond or heterogeneous nanostructures in glass, which limits the ability to engineering optical properties at the nanoscale [56][57][58][59][60]. For NCs that can be grown in-situ, it is still challenging to reach a high level of compositional and nanostructural control over the NCs.…”

“…The ever-advancing synthetic techniques of NCs using a wide range of techniques such as wet chemistry [72][73][74], laser ablation [75], ball milling [58,59] and detonation [60] have shown exceptional control over emitting center concentration, crystallite phase, size, shape, composition and nanostructure. The technique, which consists of the synthesis of the NCs and then of their addition in the glass, gives a clear advantage as compared to the glass-ceramic technique for the synthesis of hybrid material, as with this novel fabrication technique, one can control the composition and nanostructure of the as-prepared NCs and glasses, overcoming the limitation of the glass ceramics method.…”

Versatile Multicolor Nanodiamond Probes for Intracellular Imaging and Targeted Labeling

“…Therefore, FNDs containing centers with narrowband emission at the near IR (NIR) spectral range are particularly advantageous to achieve a better signal to noise ratio imaging for long term cellular imaging. [18] In addition, excitation of NIR emitters can be achieved using a longer wavelength, therefore minimizing tissue light absorption. Finally, use of NIR luminescent probes is valuable in bio-imaging as it presents a greater tissue penetration depth comparing to visible range fluorophores.…”

“…Finally, use of NIR luminescent probes is valuable in bio-imaging as it presents a greater tissue penetration depth comparing to visible range fluorophores. [18] One particular defect that meets these criteria is the silicon vacancy (SiV) color center in diamond that has narrowband emission at 738 nm. Despite clear advantages of SiV ND properties, reliable fabrication and application of SiV FNDs for sustained biological applications remains a pressing issue and challenge.…”