Fading microscopic codes to protect pharmaceuticals from counterfeiting

Abstract

To protect pharmaceuticals from counterfeiting there is a growing interest in the incorporation of labels in tablets and capsules. All types of labels applied in drugs and goods today contain ‘static’ codes, which are easily copied or falsified. To improve the protection level we introduce ‘dynamic codes’ (DYNcodes) whose structure changes in a predictable manner over time. DYNcodes are created through photobleaching fluorescent molecules embedded in a polymeric film. They appear as dark microscopic spots whose size and contrast can be easily varied, which makes the number of unique DYNcodes virtually unlimited. Choosing a polymeric film in which the photobleached molecules slowly diffuse results in microscopic spots which gradually fade in time. We show that the time dependent fading of the codes uniquely depends on initial features of the spots just after bleaching, like size and contrast.

Therefore, knowing the code as it was initially applied on the product together with the fading kinetics, it can be confirmed whether a code is genuine or perhaps falsified at a later time. We found that DYNcodes lasting for more than half a year could be designed in polyglycerol films loaded with slowly diffusing fluorescent nanobeads. In addition we showed that writing DYNcodes on the surface of drug tablets is very feasible. Compared to static codes we foresee that fading microscopic codes will be highly difficult to copy by criminals who harm patients through fake medicines.

Highlights

Dynamic anti-counterfeiting codes created by photobleaching fluorescence
Fading patterns arise from slow diffusion of bleached fluorophores in films
Each DYNcode shows unique, predictable time-dependent fading behavior
Long-lasting DYNcodes (>6 months) achieved in polyglycerol nanobead films
Enables direct, secure in-drug labeling on tablet surface

Preparation of FD150-gelatin films

To investigate the concept of dynamic encoding we made use of FITC-dextran, as a model probe, encapsulated in a gelatin hydrogel film (matrix). FITC-dextran (FD150; average molecular weight 150 kDa; Sigma-Aldrich, Belgium) was dissolved in distilled water to prepare an FD150 solution (40 mg/mL). Gelatin powder (Type A, gel strength~300 g Bloom, Sigma-Aldrich, Belgium) was dissolved in distilled water at 40 °C (12.5% w/v).

Dawei Hua, Tao Lu, Aranit Harizaj, Toon Brans, Herlinde De Keersmaecker, Chris Vervaet, Sandra Van Vlierberghe, Peter Dubruel, Kevin Braeckmans, Ranhua Xiong, Chaobo Huang, Stefaan C. De Smedt,
Fading microscopic codes to protect pharmaceuticals from counterfeiting,
Chemical Engineering Journal, Volume 530, 2026, 173470, ISSN 1385-8947,
https://doi.org/10.1016/j.cej.2026.173470.