3D printed antibacterial and anti-inflammatory scaffold containing vanillin-loaded Soluplus nanomicelles for healing of infected wounds

Abstract

Treating infected wounds is a major clinical challenge, and concerns about bacterial resistance have driven the shift toward natural antimicrobials over antibiotics. Herein, a 3D printed scaffold wound dressing consisting of alginate (Alg) and fucoidan (F) was prepared, and Soluplus (Sol) nanomicelles (NMs) were used to load vanillin (Vn) as a lipophilic antibacterial agent into the 3D printed scaffold. Characterization analyses revealed that the fabricated scaffold exhibited a peak swelling capacity of 294.3 ± 24.1% and underwent a weight loss of 38.0 ± 2.25% following a seven-day immersion in PBS. The Vn release from the Alg-F-VnNMs scaffold reached 80.6 ± 5.3% after seven days of immersion in PBS. The controlled release of Vn from the scaffold resulted in inhibition zones of 21.4 ± 1.15 mm against S. aureus and 23.2 ± 0.9 mm against E. coli within 24 h, while further analysis displayed a potent bactericidal effect, eradicating more than 80% of the bacterial population. In vivo studies on a full-thickness rat wound model showed that the Alg-F-VnNMs scaffold reduced inflammation, enhanced collagen deposition, and accelerated regeneration, leading to complete wound healing in 14 days, confirming its efficacy in wound management and skin repair.

Introduction

The skin serves as a protective barrier, blocking exogenous and pathogenic microorganisms from entering the body. When severe damage occurs, these microorganisms can infiltrate the tissue, leading to infection. Infected wounds deviate from normal healing processes due to intense inflammation, causing delayed tissue repair. In critical cases, severe infection can result in tissue loss or even fatal outcomes1. The most common approach to combating infections is the administration of antibiotics. However, oral administration or injection of antibiotics reduces bioavailability in the wound site, and their use is always limited due to the probability of bacterial resistance2,3.

Beyond infection control, supporting the regeneration of damaged skin tissue is a vital clinical approach. In recent decades, advancements in skin tissue engineering have emerged to overcome the limitations of conventional wound treatment methods4. 3D printing is a pivotal technique in tissue engineering, enabling the rapid and precise fabrication of customized scaffolds with exceptional structural integrity and reproducibility5. Natural biomaterials, such as biopolymers, are favored in biomedical applications like wound healing due to their renewability, biodegradability, biocompatibility, and ability to be metabolized in the human body, while also minimizing immune response compared to synthetic alternatives6. Alginate (Alg) is a linear anionic polysaccharide derived from brown algae, consisting of β-1,4-linked D-mannuronic acid and β-1,4-linked L-guluronic acid units. The deprotonated carboxyl groups in α-L-guluronic acid provide a negative charge, facilitating cross-linking with divalent cations such as Ca2+. This unique chemical composition, characterized by excellent gelation properties and high viscosity, has positioned Alg as a promising material for biomedical applications, especially in the fabrication of 3D-printed tissue engineering constructs7. Additionally, Alg possesses hemostatic properties and enhances wound healing by modulating chemokine expression, promoting anti-inflammatory markers such as CXCL4, CCL3, CCL12, and CXCL12, while suppressing pro-inflammatory ones like CXCL5, CXCL8, CCL1, CCL2, CCL5, and CCL118,9. However, one significant drawback of Alg-based biomaterials in treating infected wounds is their lack of antibacterial properties10. Fucoidan (F), a sulfated biopolymer derived from brown algae, is both biodegradable and biocompatible. It demonstrates strong antibacterial properties and excellent cytocompatibility, contributing to wound healing by regulating inflammation through the modulation of pro-inflammatory factors and cytokine secretion. Moreover, F can play a crucial role in the early stages of wound repair by acting as an effective hemostatic agent5,11.

As previously noted, conventional antibiotics frequently encounter the significant hurdle of bacterial resistance, while systemic administration compromises their bioavailability. To overcome the bioavailability challenges, antibacterial delivery systems have been seamlessly integrated with tissue-engineered constructs to enhance the effectiveness against infected wounds. Notably, natural products represent a rich source of novel compounds with potent antibacterial properties, which minimize the possibility of bacterial resistance12. Vanillin (Vn) (4-hydroxy-3-methoxybenzaldehyde), a phenolic aldehyde extracted from vanilla orchid pods and commonly used as a flavoring agent in the food industry, exhibits favorable biocompatibility compared to other phenolic compounds13. Due to its phenolic groups and lipophilic nature, it is also recognized as a potent antibacterial agent against both Gram-negative and Gram-positive bacteria14,15. However, the lipophilic nature of Vn poses challenges for its incorporation into hydrophilic polymer solutions. To facilitate the loading of lipophilic compounds in aqueous systems, amphiphilic nanocarriers are commonly utilized. Amphiphilic polymers, such as Soluplus® (Sol), can undergo self-assembly to form nanomicelles with a hydrophilic shell and a lipophilic core. Sol is a biocompatible copolymer composed of polyvinylcaprolactam, polyvinylacetate, and polyethylene glycol, where polyethylene glycol serves as the hydrophilic portion, while the polyvinylcaprolactam-polyvinylacetate side chains form the hydrophobic segments16,17.

Building on the aforementioned points, this study focuses on the fabrication of a 3D-printed Alg-F scaffold incorporating Vn-loaded nanomicelles and evaluating its effectiveness in treating infected wounds. To the best of our knowledge, no prior research has examined the application of 3D-printed Alg-F scaffolds for wound healing, particularly the encapsulation of Vn within Sol nanomicelles and its integration into skin tissue engineering scaffolds. This innovative strategy presents a distinct approach to enhancing infected wound healing by integrating a 3D-printed alginate–fucoidan scaffold with vanillin-loaded nanomicelles as a targeted drug delivery system, thereby bridging a specific gap not addressed in the current literature.

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Materials

Sodium alginate (Alg) was purchased from Sinopharm Chemical Reagent Co. Ltd. Shanghai, China (Mw = 153,300 g/mol, the ratio of mannuronic acid (M blocks) to guluronic acid (G blocks), i.e., M/G ratio = 0.8). Soluplus® (Sol) was purchased from BASF Company (Ludwigshafen, Germany) and Vanillin (Vn) from Merck (Germany). Fucoidan (F) (≥ 85% purity, ∼72 kDa) and dimethyl thiazole diphenyltetrazolium bromide (MTT) were bought from Sigma-Aldrich, USA. For animal studies, ketamine (Rotexmedica, Germany), and xylazine (Rompun®, Germany) were also obtained.

Shafeeq, Z.F., Al-Saedi, F., Rajab, E.S. et al. 3D printed antibacterial and anti-inflammatory scaffold containing vanillin-loaded Soluplus nanomicelles for healing of infected wounds. Sci Rep 15, 32244 (2025). https://doi.org/10.1038/s41598-025-18174-9

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