Zetasizer nano zs 3600

Particle size, Polydispersity Index, and Zeta Potential were determined by Dynamic Light Scattering (DLS) technique performed by Zetasizer Nano ZS 3600 (Malvern Instruments, Worcestershire, United Kingdom) device. The mentioned factors were measured twice; firstly, immediately after preparation, and secondly, after lyophilization [13 (link)].

Dynamic light scattering (DLS) and zeta potential analyses were used as part of a quality control routine for the preparation of all MWNT suspensions, as previously described [50 (link),51 (link),54 (link)]. The particle size distributions, in terms of hydrodynamic diameter, of the BSA-MWNT suspensions were determined by DLS. In brief, aliquots of purified pMWNT or cMWNT suspensions were diluted 1:10 in a 0.10 mg/mL BSA working solution and analyzed with a Zetasizer Nano-ZS 3600 (Malvern Instruments, Worcestershire, UK) using a 633-nm laser and a backscatter measurement angle of 173°. The instrument was calibrated with Polybead^® standards (Polysciences, Warrington, PA, USA) and ten consecutive 30-s runs were taken per measurement at 25 °C. The hydrodynamic diameter was calculated using a viscosity and refractive index of 0.8872 cP and 1.330, respectively for deionized water, and an absorption and refractive index of 0.010 and 1.891, respectively, for MWNTs. Zeta potential values were also determined for purified BSA-coated MWNT suspensions that were diluted 1:10 with deionized water. In addition, DLS and zeta potential analyses were performed periodically on purified MWNT suspensions stored at 4 °C. Typically, MWNT suspensions were stable in storage for months, indicated by the lack of aggregates detected by DLS and constant zeta potential results.

The particle size distributions, in terms of hydrodynamic diameter, of BSA-MWNT suspensions were determined by dynamic light scattering (DLS). In brief, aliquots of purified pMWNT or cMWNT suspensions were diluted 1:10 in a 0.10 mg/mL BSA working solution and analyzed using a 633-nm laser and a backscatter measurement angle of 173° (Zetasizer Nano-ZS 3600, Malvern Instruments, Worcestershire, UK). The instrument was calibrated with Polybead^® standards (Polysciences, Warrington, PA, USA) and ten consecutive 30-s runs were taken per measurement at 25 °C. The hydrodynamic diameter was calculated using a viscosity and refractive index of 0.8872 cP and 1.330, respectively, for deionized water, and an absorption and refractive index of 0.010 and 1.891, respectively, for MWNTs. Zeta potential values were also determined for purified BSA-coated MWNT suspensions that were diluted 1:10 with deionized water, medium with serum, or serum-free medium. In addition, DLS and zeta potential analyses were performed periodically on purified MWNT suspensions stored at 4 °C to detect any changes. Typically, MWNT suspensions were stable in storage for months, indicated by the lack of aggregates detected by DLS and constant zeta potential results.

α_S1-casein (1 mL, 50 µM) in phosphate buffer was incubated for 3 h at 37 °C. Samples were transferred into a quartz cuvette. Proteinoligomer diameter and oligomers’ population PI were analyzed by PCS (Zetasizer NanoZS3600, Malvern Instruments, Worcestershire, UK). Before each measurement, samples were equilibrated for at least 2 min. The mean of 15 single measurements was recorded. Samples were recorded with an attenuator value of 8. Temperature denaturation was recorded by a heating rate resolution of 0.5 °C.

The hydrodynamic diameter for MFer colloidal solutions was determined by dynamic light scattering (DLS) performed at Zetasizer Nano ZS 3600 (Malvern Instruments, Malvern, UK) using the Stokes-Einstein’s equation:
$$D_T=\frac{k T}{6 \pi \eta R_h}$$
where D_T is the diffusion coefficient, k is the Boltzmann constant, T is the temperature, η is the solvent viscosity, and R_h is the Stokes, or hydrodynamic, radius of a spherical particle. The hydrodynamic diameter D_HYDR was measured using disposable polystyrene cuvettes in the protein mode of the data analysis at 25 °C. The size distribution was displayed in the Zetasizer software as a dependence of the relative number of particles on their size, and the hydrodynamic diameter represented the maximum of the curve. The temperature trend was followed using glass cuvettes in the protein mode of the data analysis.