A novel luminescent bifunctional POSS as a molecular platform for biomedical applications

Abstract

A novel luminescent polyhedral oligomeric silsesquioxane (POSS) containing in the structure a fluorescein derivative molecule and a carboxylic functionality, suitable to anchor different organic compounds (dyes, markers, drugs, contrast agents, …), was successfully synthesized and characterized in this manuscript by a multidisciplinary approach. An emission enhancement of the dye of ca. four times was found after reaction with POSS, rendering this new hybrid compound a promising contrast agent for optical imaging. In vitro tests on tumoral HeLa cells demonstrated that the luminescent POSS (namely POSS_F), here described, is able to be taken up in the cell cytosol by an efficient and selective process. Its high chemical versatility and peculiar properties could render this novel bifunctional POSS a molecular platform for biomedical applications.

Controlled Click‐Assembly of Well‐Defined Hetero‐Bifunctional Cubic Silsesquioxanes and Their Application in Targeted Bioimaging

“…The structures of the new POSS products were unambiguously confirmed by high-resolution mass spectrometry and multinuclear ( 1 H, 13 C, 29 Si) NMR spectroscopy (see the Supporting Information). For example, the combination (in the appropriate order) of CuAAC heptafunctionalization with either alkene homo/cross-metathesis (8, 9), transition-metalcatalyzed cross-coupling (8, 9, 10), deprotection followed by ester (12) or amide bond formation (11,12), amine deprotection followed by diazo-transfer and subsequent CuAAC reaction (11), or Diels-Alder cycloaddition (13) could provide access to a large variety of new hetero-bifunctional POSS. This set of hetero-bifunctional POSS allows for the selective, stepwise modification of the cage functionality at either the azido groups or the other orthogonal functionality for the preparation of new bifunctional hybrid materials with welldefined structures.…”

“…Within the last two decades, polyhedral oligosilsesquioxanes (POSS) [2] have emerged as an increasingly important group of 3D nano-building-blocks for the preparation of a variety of hybrid functional-materials. [3,4] POSS are usually synthesized by hydrolytic condensation of organosilicon monomers RSiX 3 (R = organic group; X = halogen or alkoxide group) and can be readily modified both on the inorganic cage (e.g., T 8 , T 10 , T 12 , and so on) [5] and the peripheral organic functionality (mono-, multi-, homo-or heterofunctionalized). Due to their rigid inorganic core, these unique nanometer-sized hybrid molecules have superior mechanical and thermal stabilities that are partially transmitted to their derived materials.…”

“…POSS containing an assortment of two different organic groups (hetero-bifunctional POSS) [11] are the simplest class among these multifunctional derivatives and possibly the most useful, but those allowing independent derivatization of both functionalities have scarcely been reported. [4,12] The preparation of Janus-type POSS particles is also a very promising application that is being actively pursued. [4,12] The preparation of Janus-type POSS particles is also a very promising application that is being actively pursued.…”

“…Applications in areas as diverse as polymers, composite materials, dendrimers, optical materials, coatings, liquid crystals, metal catalysts, drug carriers, and tissue engineering have been described, particularly in the patent literature. [3,4] POSS are usually synthesized by hydrolytic condensation of organosilicon monomers RSiX 3 (R = organic group; X = halogen or alkoxide group) and can be readily modified both on the inorganic cage (e.g., T 8 , T 10 , T 12 , and so on) [5] and the peripheral organic functionality (mono-, multi-, homo-or heterofunctionalized).…”

“…For example, the functionalization of the POSS cage with both a biorecognition element (e.g., a pepA C H T U N G T R E N N U N G tidic, nucleic acid, or carbohydrate epitope) and an "active" molecule, such as a fluorescent dye, a magnetic resonance imaging probe, a drug or other functional molecules, is of great interest for potential applications in bio-A C H T U N G T R E N N U N G imaging, vectorized drug-transport, or for the study of biological receptors. [4,12] The preparation of Janus-type POSS particles is also a very promising application that is being actively pursued. [13,14] Five different strategies have been described in the literature for the preparation of hetero-bifunctional POSS: 1) direct co-hydrolytic condensation of mixtures of different organosilicon monomers; [5d, 15] 2) nucleophile-induced cage reshuffling of mixtures of different preformed POSS; [16] 3) cross-condensation of two cyclic tetrasiloxane tetraols ("half-cube" silsesquioxanes); [13b, 17] 4) corner-capping of incompletely condensed silsesqui- 18,38] and 5) partial functionalization of homo-octafunctional POSS.…”