Miniaturized probes for cell microenvironment: Development, characterization, and application of fluorescent oxygen-sensing microparticles.

摘要

Oxygen concentration is a key parameter in tissue culture and tissue engineering. As such, oxygen diffusion through biomaterials plays an important role in maintaining healthy tissues. As such, oxygen is one of the most important cues within the cell microenvironment, playing a role in the regulation of cellular responses that concern such cellular phenomena as cell migration, proliferation, and apoptosis. Oxygen supply has become a limiting factor during the growth of highly metabolic tissues and large tissue masses, mainly as a result of insufficient vascularization and the low aqueous solubility of oxygen. In addition, limited oxygen supply has been linked to the propagation of bacterial infections due to bacterial detachment from biofilms within the body. Therefore, gaining an understanding of the cellular response to changes in soluble cues, such as oxygen concentration, through their microenvironment may potentially lead to optimized oxygen delivery within biomaterials, improved methods to control cell behavior in engineered tissues, and improved therapies to treat bacterial infections. However, mapping oxygen concentration and characterizing oxygen transport in three-dimensional culture systems has proven difficult due to the lack of adequate tools.;To address this need, we have developed oxygen-sensing microparticles that can be suspended through the volume of a transparent biomaterial and measure oxygen concentration and characterize oxygen transport in a non-invasive manner. These microparticles sense oxygen by fluorescence quenching of the oxygen-sensitive fluorophore tris (4,7-diphenyl-1,10-phenanthroline) ruthenium (II) dichloride, or Ru(Ph2phen3)Cl2, while immobilized onto silica carriers. These microparticles are geared towards applications in both mammalian and bacterial cell culture where oxygen concentration and transport can be directly correlated to cell function. We provide a detailed description of the synthesis processes of these microparticles, their characterization, and calibration. Subsequently, we show that they are suited for their intended applications by demonstrating that they can be suspended through the volume of a biomaterial and are compatible with both mammalian and bacterial culture. Finally, we propose methodologies for the intended applications of the microparticles regarding the correlation cell function to oxygen transport during 3D mammalian cell culture and bacterial biofilm culture. This correlation will mark the first time oxygen concentration is linked to cellular functions that it directly impacts during three-dimensional culture.