Dynamic Light Scattering Analysis for the Determination of the Particle Size of Iron-Carbohydrate Complexes

Dynamic light scattering, or DLS, is a fundamental method to evaluate intact particle size and distribution. However, analysis of iron carbohydrate nanoparticles does pose some challenges. An advantage of DLS include wide available instrumentation, easy to perform the analysis, and establish protocols for the analysis of nanomaterials.

One of the goals of DLS is to evaluate the poly dispersity profile of the nanoparticles, which may ultimately affect the interaction with the biological milieu. For the demonstration of the procedure, will be Cintia Batista Marques, a PhD candidate from University of Geneva. After starting the machine in the instrument software, select the storage location in the opened window, name the measurement file, and confirm the details by clicking on save.

Select the required standard operating procedure from the dropdown list in the instrument interface. If an older SOP is needed, select browse for SOP from the list and confirm the selection by clicking on the green arrow. To begin the measurement process, click on the green start button at the bottom of the instrument interface screen.

Then, fill one milliliter of the undiluted particle standard into a polystyrene cuvette and close it with the lid. Once filled, ensure that there are no air bubbles. If any air bubbles are present, remove them by tapping lightly on the cuvette.

Place the cuvette in the cell holder of the instrument with the arrow mark facing forward and close the measuring chamber cover. Load the unit parameter SOP and enter sample name SST 20 nanometer particle standard in the start window. Additionally, add a note that includes an identifier number and the expiry date of the standard.

To measure iron sucrose solution, pipette 0.5 milliliters of an iron sucrose solution with 2%mass by volume iron content into a 25 milliliter volumetric flask and fill up to the mark with low particle water, resulting in a solution containing 0.4 milligrams iron per milliliter. Now place the plastic cuvette containing the measuring solution in the device with the arrow mark facing forward and close the lid. Load the parameter SOP again and enter sample name batch number in the start window.

Start the measurement and when it finishes, indicated by an acoustic signal, close the measurement window. Calculate the mean value of six individual measurements. Mark the individual measurements in the records view of measurement file and right click on create average result.

Add the name of the mean value under sample name. Then confirm by clicking on okay. Wait for the software to create a new record at the end of the list and look for a name entered as well as the average result in that record.

The size distribution plots by intensity, volume, and number are shown. Size distribution by intensity impacted by a second peak is provided as an example of a bad result. Poor quality data showed an additional signal at 5, 000 nanometers.

The size distribution by number differed by up to a factor of two from the proposed intensity based Z average. Only slightly lower values were calculated by the size distribution by volume. When using DLS to characterize iron carbohydrate nanoparticles, it is important to ensure correct SOP, sample dilution, and also cuvette filling.

Asymmetrical flow field flow fractionation and size exclusion chromatography and small angle x-ray scattering can be performed as additional orthogonal physico-chemical methods. Validated protocols for DLS greatly improve the robustness of initial and comparative characterization of iron carbohydrate nanoparticles. However, the sample preparation and the bias of the technique toward large particle sizes needs to be considered in the context of orthogonal methodologies.