Bigels: a comprehensive review of properties, preparation techniques, applications in pharmaceuticals, food, cosmetic products, and emerging patents

In recent years, bigels (BGs) have garnered increasing attention as an innovative class of semisolid formulations, distinguished by their unique ability to combine two immiscible gels through high shear mixing, resulting in a uniform dispersion. This distinctive composition imparts BGs with a wide range of advantageous properties. They not only facilitate the delivery of both hydrophilic and lipophilic drugs but also demonstrate rapid spreadability and easy washability, which are crucial for patient comfort and compliance. Furthermore, BGs are noted for their capacity to enhance skin hydration, particularly within the stratum corneum, thereby potentially improving therapeutic outcomes. This review aims to comprehensively explore the classification, advantages, limitations, various preparation methods, and characterization techniques employed for BGs. Key analytical approaches discussed include microscopy for detailed structural analysis, droplet size distribution assessments, Fourier transform infrared spectroscopy to examine chemical properties, and mechanical tests such as viscosity, spreadability, and texture evaluations. Furthermore, skin irritation tests and determination of the zone of inhibition are crucial to assess the antimicrobial activity and ensure the safety and efficacy of the formulations. Studies on in vitro drug release, ex vivo skin permeation experiments, and stability assessments are crucial for understanding their performance in pharmaceutical and cosmetic applications. In vitro drug release studies help in predicting the release kinetics of drugs from BGs, while ex vivo skin permeation experiments provide insights into the ability of BGs to deliver drugs through the skin. Stability assessments, including physical, chemical, and microbiological stability, are essential to ensure the long-term effectiveness of bigel formulations. Despite not yet being commercially available, research has shown BGs to be effective carriers for controlled drug release in topical, transdermal, buccal, and vaginal drug delivery systems. Their ability to incorporate and deliver both hydrophilic and lipophilic drugs makes them versatile and promising candidates for a variety of therapeutic applications. Moving forward, BGs hold substantial promise as versatile platforms to enhance therapeutic efficacy and patient experience in diverse formulations. Their unique properties and multifunctional capabilities could potentially revolutionize the field of drug delivery, paving the way for more effective and patient-friendly treatments.