Abstract

The delivery of therapeutic agents is often hindered by various biological barriers that impede their absorption, distribution, metabolism, and excretion. This article explores the primary physiological, cellular, and molecular barriers to drug delivery, including the gastrointestinal tract, blood-brain barrier, mucosal barriers, cell membranes, efflux transporters, and enzymatic degradation. It also examines the immune response as a significant challenge in the delivery of biologics. To address these challenges, several innovative strategies are discussed, such as nanoparticlebased drug delivery, prodrug approaches, transporter inhibition, peptide and protein modification, chemical penetration enhancers, BBB penetration carriers, and mucus-penetrating particles. These advancements aim to enhance drug stability, bioavailability, and targeted delivery, ultimately improving therapeutic efficacy and patient outcomes. As the field of biopharmaceutics evolves, overcoming these biological barriers remains crucial for the development of more effective treatments for various diseases