Polyethylene glycol (PEG)

Definition

Polyethylene glycol (PEG) is a polyether compound that is widely used in pharmaceuticals, cosmetics, and as a surfactant due to its hydrophilic properties. It plays a crucial role in steric stabilization, helping to prevent particles from aggregating by creating a protective layer around them, which enhances the stability of colloidal systems.

5 Must Know Facts For Your Next Test

1. PEG molecules can vary in molecular weight, affecting their physical properties and applications, with low molecular weight PEGs being more fluid and high molecular weight PEGs being more viscous.
2. In drug formulation, PEGylation involves attaching PEG chains to drugs or proteins to improve their solubility, stability, and circulation time in the body.
3. PEG provides steric stabilization by creating a hydration shell around particles, which helps to minimize van der Waals attractions and prevent aggregation.
4. PEG is biocompatible and non-toxic, making it suitable for various medical applications, including drug delivery systems and medical devices.
5. When used in emulsions or suspensions, PEG can significantly enhance the stability of formulations by reducing the tendency for phase separation.

Review Questions

• How does polyethylene glycol contribute to steric stabilization in colloidal systems?
  • Polyethylene glycol contributes to steric stabilization by forming a protective layer around colloidal particles. This layer creates a hydration shell that minimizes attractive forces between particles, such as van der Waals interactions. As a result, PEG effectively prevents aggregation and maintains a stable dispersion of the particles in the system.
• Discuss the implications of PEGylation in pharmaceutical formulations and how it enhances drug performance.
  • PEGylation involves attaching PEG chains to drugs or proteins, which significantly enhances their performance in pharmaceutical formulations. By improving solubility and stability, PEGylation allows for better bioavailability and longer circulation times in the bloodstream. This modification reduces the rate at which drugs are cleared from the body, leading to prolonged therapeutic effects and potentially reducing the frequency of administration.
• Evaluate the importance of hydrophilicity and steric hindrance provided by polyethylene glycol in maintaining colloidal stability.
  • Hydrophilicity and steric hindrance are critical factors that contribute to colloidal stability when using polyethylene glycol. The hydrophilic nature of PEG allows it to interact favorably with water, forming a hydration shell around particles that prevents aggregation. Additionally, the steric hindrance created by the bulky PEG chains further reduces interactions between particles. Together, these characteristics ensure that colloidal systems remain stable over time, avoiding issues such as sedimentation or flocculation.

Related terms

Steric Hindrance:

The phenomenon where the size of groups within a molecule prevents chemical reactions or interactions due to spatial constraints.

Hydrophilicity: The property of a molecule to interact favorably with water, often leading to increased solubility in aqueous solutions.

Colloidal Stability:

The ability of a colloid to remain uniformly dispersed without settling or agglomerating over time.