Low Viscosity Highly Concentrated Injectable Nonaqueous Suspensions of Lysozyme Microparticles

Abstract

Subcutaneous injection of concentrated protein and peptide solutions, in the range of 100–400 mg/mL, is often not possible with a 25- to 27-gauge needle, as the viscosity can be well above 50 cP. Apparent viscosities below this limit are reported for suspensions of milled lysozyme microparticles up to nearly 400 mg/mL in benzyl benzoate or benzyl benzoate mixtures with safflower oils through a syringe with a 25- to 27-gauge needle at room temperature. These apparent viscosities were confirmed using a cone-and-plate rheometer. The intrinsic viscosity regressed from the Kreiger–Dougherty model was only slightly above the Einstein value of 2.5, indicating the increase in viscosity relative to that of the solvent was caused primarily by the excluded volume. Thus, the increases in viscosity from electrical double layer interactions (electroviscous effects), solvation of the particles, or deviations of the particle shape from a spherical geometry were minimal, and much smaller than typically observed for proteins dissolved in aqueous solutions. The small electroviscous effects are expected given the negligible zeta potential and thin double layers in the low dielectric constant organic solvent. The suspensions were resuspendable after a year, with essentially constant particle size after two months as measured by static light scattering. The lower apparent viscosities for highly concentrated protein suspensions relative to protein solutions, coupled with these favorable characteristics upon resuspension, may offer novel opportunities for subcutaneous injection of therapeutic proteins.

Antibody nanoparticle dispersions formed with mixtures of crowding molecules retain activity and In Vivo bioavailability

“…A standard curve using known solutions with various viscosities provided a linear correlation between the time to draw 50 μl from the conical vial to the viscosity with an r 2 value greater than 0.99 18 . These results are consistent with previous work with suspensions of model proteins and protein solutions which found that the time to draw up a specified amount of the sample in a syringe was correlated linearly to viscosity 15,18,22 .…”

“…This viscosity measurement was previously characterized for subcutaneous injections of highly concentrated solutions of monoclonal antibodies 15 and non-aqueous suspensions of lyosyzme 22 . Due to our very small sample volumes (~100 ul), we were concerned that evaporation would rapidly affect values measured with a traditional viscometer.…”

“…For example, concentrated suspensions of protein microparticles in water-insoluble organic solvents 22 and aqueous suspensions of protein crystals 7 with low viscosity have been reported. These formulations succeed by using micron-sized (5-20 μm) particles of proteins as opposed to protein monomers, thus increasing the average distance between protein particles for a given protein concentration.…”

Hydrophobic salts markedly diminish viscosity of concentrated protein solutions

“…Hundreds of protein therapeutics are currently in clinical use or advanced human trials due to their lower toxicity and more predictable and selective behavior in vivo compared to small-molecule drugs (Adama and Weiner, 2005;Danni et al, 2007;Frokjaer and Otzen, 2005;Miller et al, 2010).…”

Analytical solutions of nonlinear Poisson–Boltzmann equation for colloidal particles immersed in a general electrolyte solution by homotopy perturbation technique

“…All of the electrostatic phenomena occurring in presence of electrolyte solutions stems from the electric double layers (EDLs) formed near a charged surface, and the properties of the EDL are known to be critical concern in various applications [19][20][21][22][23][24][25], such as floatation, colloid systems, microfluidics, biological systems, and biomedical engineering. A quantitative understanding of the EDL is necessary to predict the influence of various control parameters on the occurrence of these phenomena, and the PB theory has been the core in EDL analysis to describe the electric potential and ion distributions near charged surfaces immersed in electrolyte solutions.…”