Human Insulin Enhances Avobenzone Photostability while Retaining Its Biological Activity

Area of Science:

• Photochemistry
• Biophysics
• Dermatology

Background:

• Avobenzone (AVB), a key UVA filter in sunscreens, degrades under UV exposure, reducing its effectiveness.
• Human insulin, relevant in diabetes therapy and dermatology, was explored for its potential to stabilize AVB.
• Understanding AVB photodegradation is crucial for developing more effective photoprotective formulations.

Purpose of the Study:

• To investigate the interaction between human insulin and avobenzone (AVB).
• To evaluate the impact of insulin on AVB photostability and binding.
• To assess the preservation of insulin's biological activity upon complexation with AVB.

Main Methods:

• UV spectroscopy for photodegradation studies.
• Electrospray ionization-tandem mass spectrometry (ESI-MS/MS) for complex identification.
• Fluorescence spectroscopy and 19F Nuclear Magnetic Resonance (NMR) for binding analysis.
• Molecular dynamics (MD) simulations for interaction mechanism elucidation.

Main Results:

• Insulin significantly enhanced AVB photostability under simulated sunlight and UV irradiation.
• A noncovalent insulin-AVB complex formed, with up to three AVB molecules binding per insulin.
• Binding affinity was determined (52.1 μM), with interactions involving hydrogen bonding and AVB tautomer stabilization.
• Insulin's biological activity was preserved in the insulin-AVB complex.

Conclusions:

• Human insulin acts as a photoprotective agent for avobenzone, enhancing its stability.
• The insulin-avobenzone complex formation stabilizes AVB without compromising insulin bioactivity.
• This finding offers a potential strategy for improving sunscreen efficacy and managing diabetes-related skin issues.