We report on the fabrication of efficient antibacterial substrates selective for bacteria, i.e., noncytotoxic against mammalian cells. The strategy proposed is based on the different size of bacteria (1-4 μm) in comparison with mammalian cells (above 20 μm) that permit the bacteria to enter in contact with the inner part of micrometer-sized pores where the antimicrobial functionality are placed. On the contrary, mammalian cells, larger in terms of size, remain at the top surface, thus reducing adverse cytotoxic effects and improving the biocompatibility of the substrates. For this purpose, we fabricated well-ordered functional microporous substrates (3-5 μm) using the breath figures approach that enabled the selective functionalization of the pore cavity, whereas the rest of the surface remained unaffected. Microporous surfaces were prepared from polymer blends comprising a homopolymer (i.e., polystyrene) and a block copolymer (either polystyrene-b-poly(dimethylaminoethyl methacrylate) (PDMAEMA) or a quaternized polystyrene-b-poly(dimethylaminoethyl methacrylate)). As a result, porous surfaces with a narrow size distribution and a clear enrichment of the PDMAEMA or the quaternized PDMAEMA block inside the pores were obtained that, in the case of the quaternized PDMAEMA, provided an excellent antimicrobial activity to the films.

We describe herein a novel strategy for the fabrication of efficient 3D printed antibacterial scaffolds. For this purpose, both the surface topography as well as the chemical composition of 3D scaffolds fabricated by additive manufacturing were modified. The scaffolds were fabricated by fused deposition modeling (FDM) using high-impact polystyrene (HIPS) filaments. The surface of the objects was then topographically modified providing materials with porous surfaces by means of the Breath Figures approach. The strategy involves the immersion of the scaffold in a polymer solution during a precise period of time. This approach permitted the modification of the pore size varying the immersion time as well as the solution concentration. Moreover, by using polymer blend solutions of polystyrene and polystyrene-b-poly(acrylic acid) (PS-b-PAA) and a quaternized polystyrene-b-poly(dimethylaminoethyl methacrylate) (PS-b-PDMAEMAQ), the scaffolds were simultaneously chemically modified. The surfaces were characterized by scanning electron microscopy and infrared spectroscopy. Finally, the biological response toward bacteria was explored. Porous surfaces prepared using quaternized PDMAEMA as well as those prepared using PAA confer antimicrobial activity to the films, i.e., were able to kill on contact Staphylococcus aureus employed as model bacteria.

We designed and fabricated highly efficient and selective antibacterial substrates, i.e. surface non-cytotoxic against mammalian cells but exhibiting strong antibacterial activity. For that purpose, microporous substrates (pore sizes in the range of 3-5 m) were fabricated using the breath figures approach (BFs). These substrates have additionally a defined chemical composition in the pore cavity (herein either a poly(acrylic acid) or the antimicrobial peptide Nisin) while the composition of the rest of the surface is identical to the polymer matrix. As a result, considering the differences in size of bacteria (1-4 m) in comparison to mammalian cells (above 10 µm) the bacteria were able to enter in contact with the inner part of the pores where the antimicrobial functionality has been placed. On the opposite, mammalian cells remain in contact with the top surface thus preventing cytotoxic effects and enhancing the biocompatibility of the substrates. The resulting antimicrobial surfaces were exposed to Staphylococcus aureus as a model bacteria and murine endothelial C166-GFP cells. Superior antibacterial performance while maintaining an excellent biocompatibility was obtained by those surfaces prepared using PAA while no evidence of significant antibacterial activity was observed at those surfaces prepared using Nisin.

The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/mabi.201900179. Hierarchical BiomaterialMagnesium-based implants present several advantages for clinical applications, in particular due to their biocompatibility and degradability. However, degradation products can affect negatively the cell activity. In this work, a combined coating strategy to control the implant degradation and cell regulation processes is evaluated, including plasma electrolytic oxidation (PEO) that produces a 13 µm-thick Ca, P, and Si containing ceramic coating with surface porosity, and breath figures (BF) approach that produces a porous polymeric poly(ε-caprolactone) surface. The degradation of PCL-PEO-coated Mg hierarchical scaffold can be tailored to promote cell adhesion and proliferation into the porous structure. As a result, cell culture can colonize the inner PEOceramic coating structure where higher amount of bioelements are present. The Mg/PEO/PCL/BF scaffolds exhibit equally good or better premyoblast cell adhesion and proliferation compared with Ti CP control. The biological behavior of this new hierarchical functionalized scaffold can improve the implantation success in bone and cardiovascular clinical applications.

We report on the fabrication of a microfluidic device in which the reservoir contains a porous surface with enzymatic catalytic activity provided by the reversible immobilization of horseradish peroxidase onto micrometer size pores. The porous functional reservoir was obtained by the Breath Figures approach by casting in a moist environment a solution containing a mixture of high molecular weight polystyrene (HPS) and a poly(styrene-co-cyclodextrin based styrene) (P(S-co-SCD)) statistical copolymer. The pores enriched in CD were employed to immobilize horseradish peroxidase (previously modified with adamantane) by host-guest interactions (HRP-Ada). These surfaces exhibit catalytic activity that remains stable during several reaction cycles. Moreover, the porous platforms could be recovered by using free water-soluble β-CD with detergents. An excess of β-CD/TritonX100 in solution disrupts the interactions between HRP-Ada and the CD-modified substrate thus allowing us to recover the employed enzyme and reuse the platform.

Gelatin methacryloyl (GelMA) hydrogels have been widely used for different biomedical applications due to their tunable physical characteristics and appropriate biological properties. In addition, GelMA could be modified with the addition of functional groups providing inherent antibacterial capabilities. Here, GelMA-based hydrogels were developed through the combination of a GelMA unmodified and modified polymer with quaternary ammonium groups (GelMAQ). The GelMAQ was synthesized from GelMA with a low degree of substitution of methacrylamide groups (DSMA) and grafted with glycidyltrimethylammonium chloride in the free amine groups of the lysine moieties present in the original gelatin. GelMAs with high DSMA and GelMAQ were combined 50/50% or 25/75% (w/w), respectively, and compared to controls GelMA and GelMA with added chlorhexidine (CHX) at 0.2%. The different hydrogels were characterized using 1H-NMR spectroscopy and swelling behavior and tested in (1) Porphyromonas gingivalis to evaluate their antibacterial properties and (2) human gingival fibroblast to evaluate their cell biocompatibility and regenerative properties. GelMA/GelMAQ 25/75% showed good antibacterial properties but also excellent biocompatibility and regenerative properties toward human fibroblasts in the wound healing assay. Taken together, these results suggest that the modification of GelMA with quaternary groups could facilitate periodontal tissue regeneration, with good biocompatibility and added antibacterial properties.

We described the fabrication of functional and microstructured surfaces from polymer blends by spray deposition. This simple technique offers the possibility to simultaneously finely tune the microstructure as well as the surface chemical composition. Whereas at lower polymer concentration, randomly distributed surface micropatterns were observed, an increase of the concentration leads to significant changes on these structures. On the one hand, using pure homopolystyrene fiber-like structures were observed when the polymer concentration exceeded 30 mg/mL. Interestingly, the incorporation of 2,3,4,5,6-pentafluorostyrene changed the morphology, and, instead of fibers, micrometer size particles were identified at the surface. These fluorinated microparticles provide superhydrophobic properties leading to surfaces with contact angles above 165°. Equally, in addition to the microstructures provided by the spray deposition, the use of thermoresponsive polymers to fabricate interfaces with responsive properties is also described. Contact angle measurements revealed variations on the surface wettability upon heating when blends of polystyrene and polystyrene-b-poly(dimethylaminoethyl methacrylate) are employed. Finally, the use of spraying techniques to fabricate gradient surfaces is proposed. Maintaining a constant orientation, the surface topography and thus the contact angle varies gradually from the center to the edge of the film depending on the spray angle.

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