Clay nanotube patches for sustained topical delivery of proteins with enhanced skin penetration.

50-nm diameter and 15 nm lumen clay nanotubes (HNT) were developed for through-skin topical delivery of proteins. The halloysite nanotube Al2O3 lumen is positively charged while its outer SiO2 surface is negative, allowing for selective inner / outer loading of charged proteins. The nanotubes were loaded with myoglobin, hemoglobin, glucose oxidase, albumin, insulin, and pepsin (at pH above their isoelectric point) via vacuum-assisted technique, achieving encapsulation efficiencies of 5-9 wt%. Dextrin-based capping was applied to modulate release kinetics, extending in vitro protein release from tens of hours to over one week. Polysaccharide tube coatings provided an option for external HNT loading of vaccines containing larger virus envelope protein aggregates. Protein-loaded HNTs were incorporated into gelatine-gel patches, and the delivery was evaluated using porcine skin models. Controlled rubbing of the clay-based gel patch disrupts the upper stratum corneum, enhancing interfacial contact and facilitating penetration. In vitro monitoring showed extended protein release for prolonged periods, while microscopy confirmed that HNTs partially localized below the skin surface, functioning as reservoir systems. 4 cm2 HNT-gelatine patch allows for sustain release of ca 0.2 mg myoglobin for 7 days, indicating the way for the sufficient amount of protein vaccine delivery. Biocompatibility studies in piglet skin cells showed high viability (>75%) and minimal pro-inflammatory cytokine response at HNT concentrations ≤0.5 mg/mL. Protein based therapeutics face delivery challenges due to poor stability, rapid degradation, short half-life, and dependence on invasive needle-based injections. The epithelial stratum corneum forms a strong barrier against macromolecular transport, preventing other types of topical delivery. Halloysite nanotubes may serve as natural, biocompatible carriers, enabling minimally invasive, localized protein-HNT deposition with hundreds micro-meter dermal permeation. We suggest a halloysite nanotube based epidermal delivery platform for sustained needle-free administration of protein therapeutics. We foresee clay nanotube formulations for sustained through-skin delivery of protein vaccines.