Monodisperse PEG

Monodisperse PEG has uniform chain length and molecular weight, unlike polydisperse PEG, which contains polymer chains of different lengths. Monodisperse PEG is synthesized using iterative chain expansion techniques that control polymer size and dispersion precisely. Monodisperse PEG products are generally a small molecule monodisperse pure PEG reagent consisting of two, three, or four PEG repeating units, with a small overall molecular weight, and their molecular weight is related to the number of repeating units in the PEG, with more repeating units increasing the molecular weight. The monodisperse PEG offered by BOC Sciences retains the good solubility of polyethylene glycol in water, and it also confers modified biomolecules flexibility, anticoagulant, and anti-macrophage phagocytosis.

Fig. 1. Synthetic Strategies for Monodisperse PEG (Molecular Pharmaceutics, 2017, 14(10): 3473-3479).

Structural Features of Monodisperse PEG

Hydroxyl Ends

PEG carries hydroxyl (-OH) groups at both ends, which makes PEG highly hydrophilic. These hydroxyl ends can be reacted with other compounds, such as binding to drug molecules to form PEG drug conjugates or chemically modifying material surfaces.

Narrow Molecular Weight Distribution

A distinctive feature of monodisperse PEG is its narrow molecular weight distribution, i.e., the molecular weights are relatively uniform with no significant molecular weight deviation. This monodispersity allows PEG to provide more accurate and controlled performance in experimental and applied research, providing greater reliability and consistency.

Advantages of Monodisperse PEG

• Improved pharmacokinetics: Enhanced solubility; improved stability.
• Increased circulation time: Reduced amount of drug required; reduced frequency of administration; decreased renal clearance increases circulation time.
• Reduces toxicity: Improved safety; reduced immunogenicity; reduced antigenicity; reduced protein hydrolysis.
• Facilitates purification and characterization: Monodisperse PEG simplifies the purification process due to the absence of multiple molecular weight classes.
• Precise functionalization and conjugation: The homogeneous structure of monodisperse PEG allows for precise functionalization and conjugation at specific chain ends.

Preparation of Monodisperse PEG

(1) PEG Preparation by Hydroxyl-Terminated

• First, a suitable starting agent is selected and reacted with a certain molar ratio of ethylene oxide to form a starting agent containing hydroxyl groups.
• Then, under an inert atmosphere, the starting agent is reacted with excess ethylene oxide at a certain temperature to polymerize to form PEG.
• At the end of the reaction, unreacted starting agent and low molecular weight impurities are removed by an appropriate purification step to obtain monodisperse PEG.

(2) PEG Preparation with Molecular Weight Control

• First, a suitable starting agent and a catalyst for the polymerization reaction, such as an alkali metal or alkaline earth metal salt, are selected.
• In a suitable reaction solvent, mix the starting agent with ethylene oxide at a certain molar ratio and add the catalyst.
• The reaction temperature, reaction time and the molar ratio of the starting agent to ethylene oxide are controlled to control the extent of the polymerization reaction and the molecular weight distribution.
• At the end of the reaction, the unreacted starting agent and impurities are removed to obtain the target product monodisperse PEG.

Applications of Monodisperse PEG

Bionic Materials

Monodisperse PEG can be used to prepare nanoparticles, microcapsules and microspheres with specific shapes and functions. These bionanomaterials can be applied in the fields of drug delivery, tissue engineering and biosensing.

Biological Separation and Purification

Monodisperse PEG has important applications in biological separation and purification processes. It can be used as a precipitant for proteins and nucleic acids to promote aggregation and separation of target molecules. In addition, PEG is commonly used in column chromatography, gel filtration and solvent precipitation steps of protein purification.

Chemical Synthesis and Catalysis

Monodisperse PEG also has applications in chemical synthesis and catalytic reactions. It can be used as a catalyst or solvent to catalyze chemical reactions and improve reaction efficiency and selectivity. In addition, PEG can be used as a protective agent for reactants or as a stabilizer for intermediates.

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Reference

1. Yu, Z. et al. Application of monodisperse PEGs in pharmaceutics: monodisperse polidocanols. Molecular Pharmaceutics. 2017, 14(10): 3473-3479.