Effect of the Dispersion State in Y5O4F7 Suspension on YOF Coating Deposited by Suspension Plasma Spray

The stable Y5O4F7 suspension for dense yttrium oxyfluoride (YOF) coating by suspension plasma spraying (SPS) was developed. Electrostatically and electrosterically stabilized aqueous Y5O4F7 suspensions were prepared and compared with a commercially available Y5O4F7 suspension without dispersant. The wettability and dispersibility of the Y5O4F7 suspensions were evaluated in terms of the zeta potential, average particle size, and size distribution with electrophoretic light scattering (ELS) and dynamic light scattering (DLS). The viscosity was measured and the sedimentation was tested to examine the fluidity and stability of the Y5O4F7 suspensions. When electrostatic (BYK-154) and electrosteric (BYK-199) dispersants were added to the Y5O4F7 suspension, the isoelectric point (IEP) of Y5O4F7 particles in the suspension shifted to lower pH. The zeta potential of both of electrostatically and electrosterically stabilized Y5O4F7 suspensions were higher than ±40 mV at pH of 8.6, respectively, which were much higher than of the Y5O4F7 suspension without dispersant. Meanwhile, the average particle size of the electrosterically stabilized Y5O4F7 suspension was much smaller than that of the electrostatically stabilized one. The electrosteric stabilization had a great effect on improving the wettability and dispersibility of the Y5O4F7 suspension. The coating rate of the electrosterically stabilized Y5O4F7 suspension was the highest among the three tested suspensions. In addition, the YOF coating deposited with the electrosterically stabilized Y5O4F7 suspension had the highest hardness and the lowest porosity.

Delivery of mRNA Vaccine against SARS-CoV-2 Using a Polyglucin:Spermidine Conjugate

One of the key stages in the development of mRNA vaccines is their delivery. Along with liposome, other materials are being developed for mRNA delivery that can ensure both the safety and effectiveness of the vaccine, and also facilitate its storage and transportation. In this study, we investigated the polyglucin:spermidine conjugate as a carrier of an mRNA-RBD vaccine encoding the receptor binding domain (RBD) of the SARS-CoV-2 spike protein. The conditions for the self-assembling of mRNA-PGS complexes were optimized, including the selection of the mRNA:PGS charge ratios. Using dynamic and electrophoretic light scattering it was shown that the most monodisperse suspension of nanoparticles was formed at the mRNA:PGS charge ratio equal to 1:5. The average hydrodynamic particles diameter was determined, and it was confirmed by electron microscopy. The evaluation of the zeta potential of the investigated complexes showed that the particles surface charge was close to the zero point. This may indicate that the positively charged PGS conjugate has completely packed the negatively charged mRNA molecules. It has been shown that the packaging of mRNA-RBD into the PGS envelope leads to increased production of specific antibodies with virus-neutralizing activity in immunized BALB/c mice. Our results showed that the proposed polycationic polyglucin:spermidine conjugate can be considered a promising and safe means to the delivery of mRNA vaccines, in particular mRNA vaccines against SARS-CoV-2.

Development and Validation of Optical Methods for Zeta Potential Determination of Silica and Polystyrene Particles in Aqueous Suspensions

Zeta potential is frequently used to examine the colloidal stability of particles and macromolecules in liquids. Recently, it has been suggested that zeta potential can also play an important role for grouping and read-across of nanoforms in a regulatory context. Although the measurement of zeta potential is well established, only little information is reported on key metrological principles such as validation and measurement uncertainties. This contribution presents the results of an in-house validation of the commonly used electrophoretic light scattering (ELS) and the relatively new particle tracking analysis (PTA) methods. The performance characteristics were assessed by analyzing silica and polystyrene reference materials. The ELS and PTA methods are robust and have particle mass working ranges of 0.003 mg/kg to 30 g/kg and 0.03 mg/kg to 1.5 mg/kg, respectively. Despite different measurement principles, both methods exhibit similar uncertainties for repeatability (2%), intermediate precision (3%) and trueness (4%). These results confirm that the developed methods can accurately measure the zeta potential of silica and polystyrene particles and can be transferred to other laboratories that analyze similar types of samples. If direct implementation is impossible, the elaborated methodologies may serve as a guide to help laboratories validating their own methods.

Electrophoretic Light Scattering and Electrochemical Impedance Spectroscopy Studies of Lipid Bilayers Modified by Cinnamic Acid and Its Hydroxyl Derivatives

Pharmacological efficiency of active compounds is largely determined by their membrane permeability. Thus, identification of drug-membrane interactions seems to be a crucial element determining drug-like properties of chemical agents. Yet, knowledge of this issue is still lacking. Since chemoprevention based on natural compounds such as cinnamic acid (CinA), p-coumaric acid (p-CoA) and ferulic (FA) is becoming a strong trend in modern oncopharmacology, determination of physicochemical properties of these anticancer compounds is highly important. Here, electrophoretic light scattering and impedance spectroscopy were applied to study the effects of these phenolic acids on electrical properties of bilayers formed from 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), 1,2-diacyl-sn-glycero-3-phospho-l-serine (PS) or DOPC-PS mixture. After phenolic acid treatment, the negative charge of membranes increased in alkaline pH solutions, but not in acidic ones. The impedance data showed elevated values of both the electrical capacitance and the electrical resistance. We concluded that at acidic pH all tested compounds were able to solubilize into the membrane and permeate it. At neutral and alkaline pH, the CinA could be partially inserted into the bilayers, whereas p-CoA and FA could be anchored at the bilayer surface. Our results indicate that the electrochemical methods might be crucial for predicting pharmacological activity and bioavailability of phenolic acids.