NIR-Light Activable 3D Printed Platform Nanoarchitectured with Electrospun Plasmonic Filaments for On Demand Treatment of Infected Wounds

Abstract

Bacterial infections can lead to severe complications that adversely affect wound healing. Thus, the development of effective wound dressings has become a major focus in the biomedical field, as current solutions remain insufficient for treating complex, particularly chronic wounds. Designing an optimal environment for healing and tissue regeneration is essential. This study aims to optimize a multi-functional 3D printed hydrogel for infected wounds. A dexamethasone (DMX)-loaded electrospun mat, incorporated with gold nanorods (AuNRs), is structured into short filaments (SFs). The SFs are 3D printed into gelatine methacrylate (GelMA) and sodium alginate (SA) scaffold. The photo-responsive AuNRs within SFs significantly enhanced DXM release when exposed to near-infrared (NIR) light. The material exhibits excellent photothermal properties, biocompatibility, and antibacterial activity under NIR irradiation, effectively eliminating Staphylococcus aureus and Escherichia coli in vitro. In vivo, material combined with NIR light treatment facilitate infectes wound healing, killing S. aureus bacteria, reduced inflammation, and induced vascularization. The final materials' shape can be adjusted to the skin defect, release the anti-inflammatory DXM on-demand, provide antimicrobial protection, and accelerate the healing of chronic wounds.

Keywords: 3D printing; NIR light‐responsive; infected wound healing; plasmonic short‐filaments; smart drug delivery.

Scheme 1

Illustration representing a) preparation process of the material and its composition and b) main application and mechanism of wound healing.

Figure 1

Electrospun fibers characterization. a) Schematic representation of the SFs preparation process. b) FE‐SEM of random fiber PLGA mat. c) FE‐SEM visualizing the aligned PLGA mat. d) FE‐SEM visualization of single fibers morphology after the structurization process. e) TEM image of AuNRs dispersed inside the fiber structure. f) FTIR analysis of DXM‐incorporated SFs showing the drug presence after material structurization. g) DSC analysis of the polymeric material indicating the Tg before (45.5°C) and after (44.3 °C) SFs preparation.

Figure 2

Characterization of the 3D printed hydrogel composite. a) Scheme representing 3D printed material preparation b) SEM image of GelMA component. c) SEM image of the SA component. d) SEM image of the GelMA/SA composite. e) SEM representing the cross‐linked GelMA/SA component with evenly dispersed 1% SFs (w/w) within the hydrogel matrix. f) Photo representing the 3D printer machine used for the scaffold preparation. g) Stereoscope photo panel showing the structure of a different material composition – layers and SFs influence material thickness. h) Cross‐section of 5 layered prints showing round filament structure. i) FE‐SEM image of the printed structure with a PI ≈ 1.0021. j) 3D printed single filament revealed the presence of SFs within its structure.

Figure 3

Physical characterization of the materials. a) Compressive stress‐strains curves of bulk hydrogels with different SFs concentrations and corresponding b) average compressive modulus. c) Tensile stress‐strain curves show the elongation of the 3D scaffolds with different printed layers, and the SFs' influence on this parameter shows the elongation at break and corresponding d) tensile strength. e) Sample mass change in time of 3D scaffolds and f) Equilibrium moisture content for the 3D print without and with 1% of SFs.

Figure 4

Photo‐thermal optimization of 3D printed material and drug release studies. a) Photo‐thermal properties comparison of the 3D printed material containing 0%, 1%, and 2% SFs. b) Photo‐thermal responsiveness of the 3D printing material containing 1% of SFs incorporated with 0.00%, 0.08%, and 0.16% of AuNRs. c) Panel with thermal camera images showing the reference 3D print without SFs/AuNRs and with SFs/AuNRs at 0.08% and 0.16% concentration. Sample temperature was shown before and after 10 min of NIR exposure. d) Temporal plots of different laser powers‐temperature dependence of 3D print over time using optimized 1% SFs/0.16% AuNRs concentration. e) Multiple NIR irradiation cycles demonstrate platform stability, with temperatures reaching consistent levels across every cycle and cooling down within 5 min after turning off the laser. f) Hydrogel influence on the DXM release profile. g) Gradual release of DXM under NIR laser irradiation from GelMA/SA+1%AuNRs/DXM 3D printed hydrogels. h) The graph quantifies DXM release at different intervals with and without NIR irradiation.

Figure 5

Direct cytotoxicity and antibacterial tests of GelMA/SA + 1% SFs/AuNRs, GelMA/SA + 1% SFs, GelMA/SA prints. a) Viability of L929 fibroblasts seeded on 3D printed structures. Live/Dead images captured on days 1 and 3 of culture: viable cells are stained green, while dead cells are marked red. Scale bar: 100 µm. b) Cell proliferation was assessed on days 1, 3, and 7, showing consistent cell increase over time in all tested samples. c) Morphological analysis of L929 fibroblasts seeded on printed structures at days 3 and 7. The actin cytoskeleton is stained green (Actin), while nuclei are stained blue (DAPI). Scale bar: 50 µm. Photothermal inactivation of d) S. aureus and e) E. coli via GelMA/SA+1%SFs/AuNRs material irradiated with NIR light. The survival percentage of bacteria was measured after 10 min for E. coli and 15 min for S. aureus or in the absence of irradiation (bacteria suspension was used as the control). Results are shown as mean ± standard deviation on a logarithmic scale.

Figure 6

In vivo skin tissue healing of cutaneous and S. aureus infected wound on rats. a) Photographs of skin wounds on days 0, 3, 7, and 14 in the I – control group NIR (+), II – GelMA/SA NIR (+), III – GelMA/SA + 1% SFs NIR (+), IV – GelMA/SA+1% SFs/DXM NIR (+), V – GelMA/SA+1% SFs/AuNRs/DXM NIR (+), VI – GelMA/SA + 1% SFs/AuNRs/DXM NIR (‐) groups. b) The graphical visualization of the remaining wound area, and corresponding c) Healing rate of groups on 0, 3, 7, and 14 days. d) H&E staining results of the skin wound. The arrows show the edge and size of the immature granulated tissue. e) Masson's trichrome staining of infected wound tissue sections after 14 days of treatment. f) Representative images of CD31 immunohistochemistry staining of infected wounds after 14 days. The red arrows show new blood vascular networks. g) Quantitative collagen volume fraction corresponding to Masson's staining images quantified using ImageJ. h) Positive area of CD31 immunohistochemistry staining images showing the new blood vessel networks.