Insights into polyelectrolyte complexes: advances in understanding mechanisms to applications in drug delivery, biomedicine, and food technology

Polyelectrolyte complexes (PECs) have attracted considerable interest recently due to their diverse applications. PECs are produced by electrostatic interactions between oppositely charged polyelectrolytes, exhibiting unique properties such as self-assembly, stimulus responsiveness, mechanical adaptability, enhanced encapsulation efficiency, interpenetrating polymer networks formation, etc. PECs have been utilized in drug delivery to control drug release, targeted distribution, and improve drug stability. In biomedicine, they are employed in tissue engineering, wound healing, and biosensors. They are used in the food industry for texture improvement, encapsulation of bioactive chemicals, and coating. They are synthesized by various methods, such as mixing oppositely charged polycations and polyanions in a solution, ion gelation, complex coacervation, and others. However, the complexation process is influenced by factors such as pH, ionic strength, temperature, polymer concentration, molecular weight, and mixing ratio. The characterization techniques help to understand the dimensions, shapes, and surface charges of PECs, given their wide range of applications. This review highlights the rationale for PECs, including chemistry and mechanisms, synthesis, characterization, special properties, and applications. It discusses various PEC-based nanoparticles, films, and hydrogels reported in this context. Additionally, this review identifies key challenges and offers suggestions regarding the potential of PECs in drug delivery, biomedicine, and food applications.