Biotin-decorated silica coated PbS nanocrystals emitting in the second biological near infrared window for bioimaging

Abstract

Nanoparticles (NPs) emitting in the second biological near infrared (NIR) window of the electromagnetic spectrum have been successfully synthesized by growing a silica shell on the hydrophobic surface of OLEA/TOP PbS nanocrystals (NCs), by means of a reverse microemulsion approach, and subsequently decorated with biotin molecules. The fabrication of very uniform and monodisperse NPs, formed of SiO₂ shell coated single core PbS NCs, has been demonstrated by means of a set of complementary optical and structural techniques (Vis-NIR absorption and photoluminescence spectroscopy, transmission electron microscopy) that have highlighted how experimental parameters, such as PbS NC and silica precursor concentration, are crucial to direct the morphology and optical properties of silica coated PbS NPs. Subsequently, the silica surface of the core-shell NPs has been grafted with amino groups, in order to achieve covalent binding of biotin to NIR emitting silica coated NPs. Finally the successful reaction with a green-fluorescent labelled streptavidin has verified the molecular recognition response of the biotin molecules decorating the PbS@SiO₂ NP surface. Dynamic light scattering (DLS) and ζ-potential techniques have been used to monitor the hydrodynamic diameter and colloidal stability of both PbS@SiO₂ and biotin decorated NPs, showing their high colloidal stability in physiological media, as needed for biomedical applications. Remarkably the obtained biotinylated PbS@SiO₂ NPs have been found to retain emission properties in the 'second optical window' of the NIR region of the electromagnetic spectrum, thus representing attractive receptor-targeted NIR fluorescent probes for in vivo tumour imaging.

Millisecond‐Timescale Monitoring of PbS Nanoparticle Nucleation and Growth Using Droplet‐Based Microfluidics

“…PbS quantum dots have a reduced band gap and exhibit exceptional electronic and optoelectronic properties for near‐IR (NIR) applications . Since their luminescence can span a broad spectrum of wavelengths in the NIR, they have found significant application in Schottky‐based solar cells, photodiodes and in both in vitro and in vivo biological imaging . It is surprising therefore that the mechanism of PbS nanoparticle formation, particularly at early reaction times, is relatively unexplored .…”

Simultaneous broadband near-infrared emission and magnetic properties of single phase Ni2+-doped β-Ga2O3 nanocrystals via mediated phase-controlled synthesis

“…In recent years, near-infrared (NIR) luminescence nanomaterials have aroused extensive attention due to their considerable promise in the fields of optical communication and bioimaging applications [1][2] . As known to all, the central wavelengths sited at 1310 nm and 1550 nm within NIR range are the second and third windows of optical communication, respectively, presenting a low optical absorption, which play an indispensable role in the advancement of the optical communication technology.…”

Encapsulation of Dual Emitting Giant Quantum Dots in Silica Nanoparticles for Optical Ratiometric Temperature Nanosensors

“…In particular, in the biomedical field, it is a reliable indicator of the occurrence of active intracellular chemical reactions, also able to provide basic information useful for understanding specific physiological conditions Among the different functionalization strategies developed to ensure that QDs and NPs are water dispersible and covered by biocompatible matrix, we recall encapsulation in molecular micelles or lipid-based structures [29,30], polymeric [31] or inorganic shell coating [32][33][34][35]. Here we chose the growth of a hydrophilic silica shell, as it represents a versatile and low cost approach [32][33][34]. The silica shell has been reported to be chemically stable in water, although solubility depends on the silica structure and solution pH, it has a low cytotoxicity and can be easily chemically modified [35][36][37].…”

“…In addition, the silica shell, being optically transparent in the visible range, brings a limited contribution to the absorption, which is a critical requirement for being integrated in a fluorescence based temperature sensor [39]. However, a silica shell growth process presents several issues concerning the structure and the properties of the final NP [32][33][34]. In general, while single core nanostructures preserve the optical properties of the core, the formation of multiple cores entrapped within a single silica particle, in close proximity with each other, may result in detrimental absorption broadening, fluorescent shift and quenching.…”