title: Feasibility of using a two-wavelength photometer to estimate the concentration of circulating near-infrared extinguishing nanoparticles.
abstract: We demonstrate a photometer based on pulse oximeter technology designed to test the feasibility of using non-invasive optics to quantify in vivo circulation parameters of optically-active particles by measuring changes in optical extinction introduced by the particles in a murine animal model. A real-time estimate of relative concentration was produced by collecting log-scaled bandpass pulsatile and non-pulsatile intensity (760 nm or 940 nm) near the extinction peak of the employed gold nanoshells and mathematically subtracting the pre-injection intensity through the murine subject. The circulation half-lives in four mice were estimated between 3 and 43 minutes compared to direct optical measurement of 5 microL blood draws with UV/Vis spectrophotometry which demonstrated nanoparticle extinctions ranging from 0.246 to 7.408 optical density (OD). A linear model fit relating the two methods produced an R2 value of 0.75. The 1.795 OD negative bias (-4.98 x 10(9) nanoparticles/ml) between the two methods describes the 35.5% (or 12.0 minutes) average error of prediction of the half-life. This report demonstrates that the circulation parameters of optically-active particles employed at therapeutically-relevant concentrations can be monitored in real-time using non-invasive optical techniques and advises further refinement.
authors.affiliation: Louisiana Tech University, Department of Biomedical Engineering, 818 Nelson Ave, Ruston, LA 71272, USA.
authors.forename: Gregory J
authors.initials: GJ
authors.lastname: Michalak
authors.forename: Heather A
authors.initials: HA
authors.lastname: Anderson
authors.forename: D Patrick
authors.initials: DP
authors.lastname: O'Neal
mesh_terms: D000465:Algorithms; D000818:Animals; D001774:Blood Chemical Analysis / Q000379:methods*; D005260:Female; D016014:Linear Models; D051379:Mice; D008807:Mice, Inbred BALB C; D057145:Nanoshells / Q000737:chemistry*; D010092:Oximetry / Q000295:instrumentation / Q000379:methods; D010783:Photometry / Q000295:instrumentation / Q000379:methods*; D013056:Spectrophotometry, Ultraviolet; D019265:Spectroscopy, Near-Infrared / Q000295:instrumentation / Q000379:methods*