To recognize the information of ischemia-induced blood vessel permeability would be valuable to formulate the drugs for optimal local delivery, we constructed an implantable needle type fiber-optic microprobe for the monitoring of in vivo fluorescent substances in anesthetized rats. This fiber-optic microprobe was composed of coaxial optical fibers and catheterized using a thin wall tubing of stainless steel (~400 um O.D. and ~300 um I.D.). The central fiber, with 100 um core diameter and 20 um cladding, coated with a 30 um layer of gold, was surrounded by 10 fibers with 50 um cores. The central fiber carried the light from the 488 nm Argon laser to the tissue while the surrounding fibers collected the emitted fluorescence to the detector. When the fiber-optic microprobe was placed in the solutions containing various concentrations of fluorescent nanospheres (20 nm), either with or without 10% lipofundin as optical phantom, nanosphere concentration-dependent responses of the fluorescence intensity were observed. The microprobe was then implanted into the liver and the brain of anesthetized rats to monitor the in situ extravasation of pre-administered fluorescent nanospheres from vasculature following the ischemic insults. Both the hepatic and cerebral ischemic insults showed immediate increases of the extracellular 20 nm fluorescent nanospheres. The implantable fiber-optic microprobe constructed in present study provides itself as a minimally-invasive technique capable of investigating the vascular permeability for in vivo nanosphere delivery in both ischemic liver and brain.
This paper proposes a novel fiber optic immunoassay biosensor based on the Fabry-Perot (F-P) interferometry. The PDMS dip coating and self-assembly monolayers coating are employed to prepare the fiber probes in the formation of F-P cavity and modification of the tip surface respectively. As the fiber probe inserting into the target solution, the immunoreaction will be introduced on the fiber tip. The covalent binding of the Rabbit IgG and Anti Rabbit IgG-Cy3 molecules on the fiber tip will contribute to the variation of the refractive index of interface as well as the reflectance. The interference spectrum will be shifted due to the reflectance variation. The time response is also implemented by taking the in-situ measurement of spectrum valley shift and the signal will reach the steady state within 15 minutes. Finally, the sensitivity of this immunoassay biosensor has also been demonstrated that the lowest detectable concentration of the target sample Anti Rabbit IgG-Cy3 is 10-12 g/ml, which is lower than the detection limit of ELISA of 5*10-11 g/ml. This fiber optic immunoassay biosensor will be applied in the brain resarch for in-vivo and in-situ monitoring the biochemical reactions of the neurocytes.