Current research has revealed the importance of a class of cell surface proteins called integrins in various vital physiological functions such as blood clotting, regulation of blood pressure, tissue blood flow, and vascular remodeling. The key to integrin functionality is its ability to mediate force transmission by interacting with the extracellular matrix and cytoskeleton. In addition, they play a role in signal transduction via their connection with the proteins in focal adhesion (FA) points. To understand the complex mechanism of cell-cell and cell-extracellular matrix (ECM) adhesion that is responsible for these diverse biochemical interactions, it is necessary to identify the integrins on cells and monitor their interaction with various ligands. To this end, for the first time, we employ surface-enhanced Raman spectroscopy (SERS) to detect integrins. The results show the capability using SERS to detect the integrins to the nanomolar concentration regime and to distinguish between two different kinds of integrins, V3 and 51, that are present in vascular smooth muscle cells (VSMCs). It is anticipated that the SERS approach will potentially help elucidate the mechanism of integrin-ligand interactions in a variety of phenomena of physiological importance.
Integrins play an important role in the adhesion of cells to extracellular matrix and to other cells around them, more specifically fibronectin. The ultimate goal of this research is to detect these integrins on the surface of the cell with a combined atomic force microscopy (AFM) system coupled with a surface enhanced Raman spectroscopy (SERS) system. For this paper the focus was on identifying whether SERS is capable of being used to generate a unique spectrum for integrins. This was done using silver colloidal particles and the integrins a5B1 and aVB3. It was shown that a unique spectrum could be identified for each of these integrins at the nanomolar level.
A preliminary in vivo study using photopolymerized poly(ethylene glycol) (PEG) microspheres containing tetramethylrhodamine isothiocyanate labeld concanavalin A (TRITC-Con A) fluroescein isothiocyanate labeld dextran (FITX-dextran) as an implantable glucose sensor was performed using hairless rats. The glucose sensor works by affinity reaction between the two fluorescent labeled molecules binding together to form a fluorescent energy transfer system in which the FITC peak is quenched by the TRITC peak. The addition of glucose to the sensors local environment displces the dextran disrupting the FRET pair and the quenching. The change in fluroescent peak ratio (TRITC/FITC) therefore can be related to glucose. The microspheres in this study were implanted below the dermal skin layer of the lower abdomen by injection. A bolus injection of glucose was given through the tail vein to simulate glucose consumption. Spectra were obtained by shining and collecting light through the skin using an optical fiber delivery system via a 488nm argon laser and a spectrophometer. The preliminary results showed quantifiable changes in the ratio between the two peaks in response to the changae in glucose levels in the interstitial fluid of the rat.