Development of a novel method for determining the molecular weight of pharmaceutical polymers by rheometry

Introduction Polyethylene glycol (PEG) is one of the most widely used polymers in the pharmaceutical field. It has been extensively used in the formulation of nanoparticles as the shielding group for preventing the removal of nanoparticles from the bloodstream by the mononuclear phagocytic system (MPS). This polymer is one of the most selected polymers in the pharmaceutical industry due to its characteristics such as high hydrophilicity, and electrical neutrality (1). The consumption of PEG can have significant effects on the stability, targeting capability, and improving the physicochemical properties of nanoparticles. The molecular weight of PEG is a very important factor as it can have effects on the coverage degree , shell thickness and therefore the zeta potential, flexibility, and protein adsorption capability of the nanoparticles (2). The most commonly used method for measuring the molecular weight of polymers is gel permeation chromatography (GPC). This method is sometimes difficult to apply and time-consuming, requiring costly equipment and standard polymers, organic solvents, and columns designed for specific molecular weight ranges(3). In this research, an alternative novel method for measuring the molecular weight of PEG-based polymers by the use of rheometry was developed. This method is cheaper, less time-consuming, and solvent-free which makes it suitable for research and industrial use. References 1.Baumann A, Tuerck D, Prabhu S, Dickmann L, Sims JJDDT. Pharmacokinetics, metabolism and distribution of PEGs and PEGylated proteins: quo vadis? 2014;19(10):1623-31. 2.Shi L, Zhang J, Zhao M, Tang S, Cheng X, Zhang W, et al. Effects of polyethylene glycol on the surface of nanoparticles for targeted drug delivery. Nanoscale. 2021;13(24):10748-64. 3.Burgess RRJPe, purification. A brief practical review of size exclusion chromatography: rules of thumb, limitations, and troubleshooting. 2018;150:81-5. 4.Morea F, Agnusdei J, Zerbino RJM, structures. Comparison of methods for measuring zero shear viscosity in asphalts. 2010;43(4):499-507. 5.Lobo H, Bonilla JV. Handbook of plastics analysis: Crc Press; 2003