Differential centrifugal sedimentation (DCS) is an established high-resolution analysis method for determining the particle size from the speed of particles moving by centrifugal force and passing a light scatter detector in a single step. It enables to characterize (in)organic nano- and micron-sized particles in colloidal suspension within minutes in a wide area of applications from materials science to biomedical. For complex biological samples, however, a major disadvantage of the technique is that it is not possible to differentiate between materials which are (bio)chemically distinct, but have similar physical properties (particle size and/or density).
We have built a novel configuration of the DCS technology capable of characterizing fluorescently labeled particles for both size and (bio)chemical composition in complex sample matrix requiring minimal purification. To this end, an existing benchtop disc centrifuge has been equipped with a 4-channel laser configuration and a detection set-up consisting of CMOS Scientific cameras, dichroic mirrors, and filters, to excite and capture signals emitted from fluorescent particles traveling through a density gradient in the spinning disc and passing the laser beam. Additionally, custom software has been created to extract the fluorescent signal from the camera images. Using fluorescently labeled polymer nanoparticles we have shown the novel device with fluorescent modality to gain in both sensitivity and specificity of detection compared to the original set-up, thus generating additional, in-depth information on the analyzed particle samples.
In conclusion, our novel technology offers a fast, easy and sensitive tool to acquire multi-parameter data on (nano)particles in complex fluid for use in research, industrial and clinical settings.