Microneedle Arrays and Transdermal Patches for Peptide Delivery in Diabetes: Design, Skin Penetration Strategies, and Patient-Centric Advantages over Subcutaneous Injections

Diabetes management requires frequent administration of peptide therapeutics such as insulin and glucagon-like peptide-1 (GLP-1) receptor agonists, which are currently delivered almost exclusively via subcutaneous injections. Despite their efficacy, injections are associated with pain, needle phobia, injection-site reactions, lipohypertrophy, and poor patient adherence. Transdermal delivery using microneedle arrays and advanced patches has emerged as a promising minimally invasive alternative that can bypass the stratum corneum barrier while improving patient comfort and compliance. This review comprehensively examines the design, fabrication, and application of microneedle arrays (dissolving, coated, hollow, and hydrogel-forming) and transdermal patches for the delivery of peptides in diabetes. Particular focus is placed on skin penetration strategies, including chemical enhancers, physical assistance techniques, and nanotechnology integration, along with material selection, drug loading, and controlled release mechanisms. The pharmacokinetic performance, bioavailability, and safety profiles of these systems are critically compared with conventional subcutaneous injections. Furthermore, this review highlights patient-centric advantages, including reduced pain, improved adherence, dose flexibility, and better quality of life. Current challenges in regulatory approval, long-term stability, manufacturing scale-up, and clinical translation are discussed. Emerging trends such as smart, stimuli-responsive, and closed-loop microneedle systems are also explored as future directions for precision diabetes care.