Biomedical subjects

R S Popovic

Publications and source records attributed to R S Popovic.

2 recordsLinked to original sources

PubMed2005

Sample patterning on NMR surface microcoils.

Aligned microcontact printing for patterning the sample in areas of homogeneous RF-field on the highly sensitive surface of planar NMR microprobes is presented. We experimentally demonstrate that sample patterning allows drastic improvement of the spin excitation uniformity. The NMR microprobes are designed for cell analysis and characterized using lipid vesicles as cell substitutes. Lipid vesicles are advantageous as composition and concentration of the confined solution are precisely controlled and because of their similarity to living cells. Using aligned microcontact printing, a monolayer of lipid vesicles is immobilized on the surface of the planar NMR microprobe in a patterned way. 1H NMR spectra and CPMG spin echoes of sucrose solution confined within the lipid vesicles are successfully recorded. Nutation curves of the sample structured in different patterns demonstrate the impact of patterning on the spin excitation uniformity. The total detection volumes are between 1 and 2 nL and derived with help of a theoretic model based on 3D finite element simulation. This model predicts the signal-to-noise ratio and the progression of the nutation curves.

Avidin↗

PubMed2003

Planar microcoil-based microfluidic NMR probes.

Microfabricated small-volume NMR probes consisting of electroplated planar microcoils integrated on a glass substrate with etched microfluidic channels are fabricated and tested. 1H NMR spectra are acquired at 300 MHz with three different probes having observed sample volumes of respectively 30, 120, and 470 nL. The achieved sensitivity enables acquisition of an 1H spectrum of 160 microg sucrose in D2O, corresponding to a proof-of-concept for on-chip NMR spectroscopy. Increase of mass-sensitivity with coil diameter reduction is demonstrated experimentally for planar microcoils. Models that enable quantitative prediction of the signal-to-noise ratio and of the influence of microfluidic channel geometry on spectral resolution are presented and successfully compared to the experimental data. The main factor presently limiting sensitivity for high-resolution applications is identified as being probe-induced static magnetic field distortions. Finally, based on the presented model and measured data, future performance of planar microcoil-based microfluidic NMR probes is extrapolated and discussed.

Electronics↗