Stability of peptides during iontophoretic transdermal delivery

Transdermal iontophoresis of insulin. Part 1: A study on the issues associated with the use of platinum electrodes on rat skin

“…In our study, the pH shift was studied at both electrode polarities and was higher during AI than during CI at pH 7.4 ( Figure 3). There was a significant degradation of insulin during AI at pH 7.4 ( Figure 5A) and the extent of degradation was comparable with that reported by Huang & Wu (1996). The earlier authors attributed the degradation to temperature (37¯C) and proteolytic degradation (using rabbit skin) in addition to the electrochemical degradation.…”

Laser-engineered dissolving microneedle arrays for protein delivery: potential for enhanced intradermal vaccination

“…Moreover, it is also possible that OVA may have been enzymatically degraded by residual skin‐derived proteases, including skin esterases and serine proteases,[35,36] while diffusing through the skin and this may have further contributed to its reduced detection. The lytic activity of skin proteases has been reported for biomolecules, such as insulin, delivered into the skin by iontophoresis [37]. Further studies are needed to investigate the contribution of OVA enzymatic degradation to its permeation across the skin in the in‐vitro scenario, thus addressing the question of whether enzymes residing in the skin are still active post freeze‐thaw and are, therefore, capable of degrading the protein target.…”

“…The lytic activity of skin proteases has been reported for biomolecules, such as insulin, delivered into the skin by iontophoresis. [37] Further studies are needed to investigate the contribution of OVA enzymatic degradation to its permeation across the skin in the in-vitro scenario, thus addressing the question of whether enzymes residing in the skin are still active post freeze-thaw and are, therefore, capable of degrading the protein target. To this end, evidence from the food industry suggests that enzyme levels are increased in those meat samples which have been freeze-thawed, [38] thus suggesting that the freeze-thaw cycle undergone by the neonatal porcine skin used in these experiments may in fact have resulted in increased enzyme activity in the skin, leading to an increased propensity for degradation of the protein.…”

Laser-Engineered Dissolving Microneedle Arrays for Transdermal Macromolecular Drug Delivery

“…The proteolytic degradation of insulin in the skin could be another potential factor affecting its transport across the skin. Huang and Wu observed significant degradation of insulin during iontophoresis, which, in addition to the electrochemical degradation and temperature, was attributed to the proteolytic degradation (42). On the contrary, Srinivasan et al did not report insulin degradation in human skin at pH 7.4 under iontophoresis (43).…”