# Nanocarrier-integrated multilayer films produced by 3D printing for improved skin adhesion and curcumin photostability

## TL;DR

This study shows how 3D printing can create skin-adhesive films that protect curcumin from light and improve its delivery for topical use.

## Contribution

The integration of nanocarriers with 3D printing to create multilayer films with enhanced bioadhesion and photoprotection for curcumin.

## Key findings

- Films with a chitosan layer showed the highest skin bioadhesion.
- A TiO2 top layer effectively prevented UVC-induced curcumin degradation.
- Nanocapsules improved both curcumin delivery and film adhesion.

## Abstract

This proof-of-concept study evaluated whether semi-solid extrusion (SSE) 3D printing could be used to fabricate multilayer topical films that simultaneously enhance skin bioadhesion and photoprotection of curcumin, a highly photolabile anti-inflammatory and antioxidant compound. The development of topical films for cutaneous delivery faces several challenges, including the need for strong skin adhesion and the protection of photolabile actives from light exposure. We hypothesized that multilayered films designed for the cutaneous delivery of curcumin and produced by SSE could address these limitations. To overcome its poor solubility and enhance bioadhesion, curcumin was encapsulated in polymeric nanocapsules (C-NCs), yielding a mean particle size of 218 ± 5 nm, a polydispersity index of 0.10 ± 0.02, a zeta potential of −11 ± 4 mV, and 100% encapsulation efficiency. Films were fabricated containing either C-NCs (FC-NC) or unloaded curcumin (FC) and consisted of three layers, namely, a chitosan-based bottom layer, a middle layer of carboxymethylcellulose and alginate, and a carboxymethylcellulose top layer incorporating titanium dioxide (TiO2). The lower and intermediate layers contained C-NC or curcumin. The final films (15 × 15 × 1.5 mm) contained 282.20 ± 7.75 µg and 246.80 ± 6.70 µg of curcumin in FC-NC and FC, respectively. Films containing the bottom chitosan layer exhibited the highest bioadhesion, while the presence of a TiO2 top layer effectively prevented UVC-induced photodegradation, supporting our hypothesis. Furthermore, the presence of C-NCs in FC-NC films promoted higher bioadhesion. This proof-of-concept study demonstrates the feasibility of integrating nanocarriers with 3D printing technology to engineer multilayer polymeric films for cutaneous application, offering enhanced bioadhesion and photoprotection. This work demonstrates how additive manufacturing can be used to design hierarchically structured, nanocarrier-integrated systems with spatially resolved functionalities.