Background and Importance Autologous serum eye drops (ASEDs) are pharmaceutical preparations used in severe dry eye disease. Sterility is a specification for eye drops, which can be obtained by filtration. Any molecule with a mean diameter greater than the filter porosity is then retained. EGF (Epidermal Growth Factor) is one of the active molecules (AMs) in ASEDs. With an intermediate molecular mass (MM) (180 kDa), its investigation makes possible to predict the impact of filtration on the concentration of other molecules.

Aim and Objectives To evaluate the impact of this sterilisation method on AM by measuring EGF concentrations before/after filtration of collected sera.

Material and Methods Four 4 mL tubes of human serum (P1-P4) were used, all from a hospital biological collection. Each serum underwent the following operations: zero filtration, clarifying filtration (CF, at 0.45 µm porosity) and sterilising filtration (SF, at 0.20 µm). The assay was performed in duplicate using the ELISA technique (Quantikine® Human EGF Immunoassay kit, R&D System, USA). The impact of filtration is considered significant if the relative difference in concentrations after the process exceeds 7.5%.

Results The EGF concentration (pg/mL) in each unfiltered serum represents the maximum concentration (100%), allowing the impact of filtrations to be expressed as relative percentages of this maximum. Under CF, these percentages were respectively, for P1 to P4: 96.2%, 97.2%, 92.8% and 97.1%, representing a reduction in concentrations between 2.8% and 7.2%. Under SF, the percentages were: 94.8%, 93.4%, 91.1% and 95.9% respectively, representing a reduction of 4.1% to 8.9%.

Conclusion and Relevance As expected, EGF concentrations decrease after filtration, especially when the porosity of the filter used is low. Moreover, the significance threshold is reached for P3 under SF. We may suppose that smaller AMs (ie IGF-1, MM 7.6 kDa; TGF-β1, MM 25 kDa) will be less retained. For larger AMs such as fibronectin (MM around 450kDa), the decrease in concentration is likely to have an impact on the ASEDs efficacy, justifying a more specific study. Other methods of ensuring the microbiological safety of ASEDs should probably also be considered.

Conflict of Interest No conflict of interest.