Polyelectrolyte Complex: A Pharmaceutical Review

This review work gives a lot of information on polyelectrolyte complexes (PECs). The complex formed is generally applied in different dosage forms for the formulation of stable aggregated macromolecules. Many properties like diffusion coefficient, chain conformation, viscosity, polarizability, miscibility, etc., are drastically changed due to the introduction of a polyelectrolyte. The formation of PECs is influenced not only by chemical properties like stereochemical fitting, their molecular weight, charge densities, etc. but also by secondary experimental conditions like concentration of polyelectrolytes prior to mixing, their mixing ratio, ionic strength of the solution, mixing order, etc. The formation of PECs is described in this article and it is divided into three main classes, i.e., primary complex formation, formation process within intracomplexes and intercomplex aggregation process. There are different types of PECs obtained according to binding agents such as polymers, proteins, surfactants, drugs, etc. Other factors which affect the formation of PECs are also discussed. There are a number of pharmaceutical applications of polyelectrolytes, such as in controlled release systems, for the enzyme and cell support, for different types of tissue reconstitution, etc. solution viscosity, polarizability, miscibility, etc. are drastically altered if ionic groups are introduced. In the solid state as well as in apolar solvents, the low molar mass counterions (LMMC) are strongly bound to the polymer ion group and the chain has no net charge. In aqueous solution, the ionic moieties are solvated and the LMMC become mobile, a process comparable to the dissolution of a simple low molar mass salt. Only a small fraction of the counterions can move away from the polymer into the bulk solution, however, due to the accumulation of charge in the polyelectrolyte domain. The remaining LMMC can move more or less freely but are restricted to the polymer domain by the electrostatic attraction of the polyelectrolyte. Polyelectrolyte complex Polyelectrolyte or polysalt complexes are formed when macromolecules of opposite charge are allowed to interact. The interaction usually involves a polymeric acid or its salt with a polymeric base or its salt. Depending on a variety of factors, it may cause the system to separate into a dilute phase and a concentrated complex coacervate phase, or it may result in a more-or-less compact precipitate or gel. The complexes can also remain in solution. Electrostatic interactions constitute the main attractive forces, but hydrogen bonding, ion dipole forces, and hydrophobic interactions frequently play a significant role in determining the ultimate structures. The formation, properties and applications of such polyelectrolyte complexes (PECs) [Figure 1] have been described in a large number Access this article online Website: www.sysrevpharm.org Quick Response Code: DOI: 10.4103/0975-8453.75046