3D-printed biomaterial patch incorporating bioactive extract and probiotics for cosmetic applications.

This thesis focuses on the design and development of innovative 3D-printed hydrogel patches that combine biocompatible materials, plant-derived bioactive compound, and probiotics for advanced skin treatment. The central idea behind the project is to create smart wound dressings capable of actively supporting the different phases of skin regeneration while also offering cosmetic benefits such as scar reduction. By integrating natural ingredients and living bacteria into a tunable hydrogel matrix, this work bridges biomaterials science with natural product research and microbiome-inspired therapy, proposing a novel, multifunctional solution for skin repair. he base of the hydrogel patch consists of gellan gum (Phytagel) and sodium alginate, two naturally derived polysaccharides known for their excellent biocompatibility, gel-forming ability, and wide use in biomedical applications. These materials were mixed with water to form a printable bioink, optimized for extrusion-based 3D printing. The addition of basil extract, enriched the formulation with antioxidant and anti-inflammatory properties. Characterization of these extract was performed through HPLC for chemical profiling, the Folin-Ciocalteu assay to determine the total polyphenol content, and DPPH radical scavenging assays to evaluate antioxidant activity. The goal of incorporating basil extract was not only to promote faster healing but also to limit inflammation and oxidative stress, which are key contributors to scar formation. The printing process was refined to allow for the creation of patches with distinct geometries tailored to the various phases of wound healing. A grid-like structure with 10% nfill was designed for fresh wounds, maximizing fluid drainage and delivering a high concentration of active ingredients to control early inflammation. An intermediate geometry with a denser infill was intended for the mid-phase of healing, providing a moderate barrier function while supporting tissue regeneration. Finally, a fully filled patch with 100% infill was developed for the final stages of healing, reducing oxygen exposure to the tissue and thereby minimizing the risk of hypertrophic scar formation. A key innovation of this work lies in the integration of probiotics within the same hydrogel system. Probiotics have recently gained attention for their role in maintaining skin health, modulating the immune response, and even supporting wound healing through microbiome balance. The selected probiotics were introduced into the bioink formulation and tested both before and after the 3D printing process to assess their viability in the printed structure. Additional tests were conducted to assess the swelling behavior and degradation of the patches in PBS (phosphate-buffered saline), simulating physiological conditions. These experiments showed that the hydrogels could absorb significant amounts of fluid, a desirable feature for wound dressings, while also degrading gradually over time, aligning with the natural progression of wound closure. Rheological testing of the bioink revealed shear-thinning behavior and suitable viscoelastic properties, confirming its printability and stability post-deposition. Altogether, the mechanical and biological characterization of the hydrogel patches supported their potential use as a topical treatment for wounds, scars, or other skin conditions requiring both structural support and biological stimulation. On a broader level, this project reflects a growing interest in using nature-inspired strategies to enhance biomedical solutions. By combining the mechanical advantages of 3D printing with the therapeutic effects of natural extracts and the biological benefits of probiotics, this thesis proposes a new class of multifunctional skin patches. These patches are not only passive barriers but active participants in the healing process, offering localized delivery of antioxidants, inflammation modulators, and microbiome support in a form that can be tailored to the individual needs of the patient. The work aligns with current trends in regenerative medicine, where personalized, bioactive materials are increasingly sought after.