Enteric-Coated Vitamin B12 Liposomes with Chitosan–PEG Dual Coating for Enhanced Oral Delivery: A Comprehensive Review

Vitamin B12 (cobalamin) is an essential water-soluble vitamin involved in erythropoiesis, neurological function, and DNA synthesis. Despite the widespread preference for oral administration, the bioavailability of vitamin B12 remains significantly limited due to degradation in the acidic gastric environment, enzymatic instability, low intestinal permeability, and dependence on intrinsic factor-mediated absorption. Conventional oral formulations, therefore, often fail to achieve therapeutic efficacy, leading to poor patient outcomes and the need for parenteral supplementation1. In recent years, nanotechnology-based drug delivery systems have emerged as promising tools to overcome these challenges. Among them, liposomes have gained considerable attention owing to their biocompatibility, ability to encapsulate hydrophilic molecules, and potential for surface modification. However, unmodified liposomes are unstable under gastrointestinal conditions, necessitating further advancements such as enteric coating and polymeric surface functionalization. This review critically evaluates enteric-coated vitamin B12-loaded liposomes with dual coating of chitosan and polyethene glycol (PEG) as an advanced oral delivery strategy. The mechanistic roles of enteric protection, chitosan-mediated mucoadhesion, and PEG-induced steric stabilisation are discussed in detail. Additionally, formulation challenges, characterisation techniques, biological evaluation approaches, and regulatory considerations are examined. The review highlights key research gaps and future perspectives, emphasising the need for systematic experimental investigations to translate this promising delivery system into clinically viable oral vitamin B12 therapies.