Maria A. Bonifacio

Insight Into Halloysite Nanotubes-Loaded Gellan Gum Hydrogels For Soft Tissue Engineering Applications

A tri-component hydrogel, based on gellan gum (GG), glycerol (Gly) and halloysite nanotubes (HNT), is proposed in this work for soft tissue engineering applications. The FDA-approved GG polysaccharide has been recently exploited as biomaterial because its biomimetic features. Gly is added as molecular spacer to improve hydrogel viscosity and mechanical properties. HNT incorporation within the hydrogel offers the versatility to improve the GG-Gly biocompatibility with potential incorporation of target biomolecules. In this work, hydrogels with different composition ratios are physically crosslinked for tuning physico-mechanical properties. An accurate physico-chemical characterization is reported. HNT addition leads to a water uptake decrease of 30-35% and tuneable mechanical properties with a compressive Youngs modulus ranging between 20 and 75kPa. Finally, in vitro study with human fibroblasts on GG-Gly hydrogels loaded with 25% HNT offered the higher metabolic activities and cell survival up to 7days of incubation.

Gallium-modified chitosan/poly(acrylic acid) bilayer coatings for improved titanium implant performances

A gallium-modified chitosan/poly(acrylic acid) bilayer was obtained by electrochemical techniques on titanium to reduce orthopaedic and/or dental implants failure. The bilayer in vitro antibacterial properties and biocompatibility were evaluated against Escherichia coli and Pseudomonas aeruginosa and on MG63 osteoblast-like cells, respectively. Gallium loading into the bilayer was carefully tuned by the electrochemical deposition time to ensure the best balance between antibacterial activity and cytocompatibility. The 30min deposition time was able to reduce in vitro the viable cell counts of E. coli and P. aeruginosa of 2 and 3 log cfu/sheet, respectively. Our results evidenced that the developed antibacterial coating did not considerably alter the mechanical flexural properties of titanium substrates and, in addition, influenced positively MG63 adhesion and proliferation. Therefore, the gallium-modified chitosan/poly(acrylic acid) bilayer can be exploited as a promising titanium coating to limit bacterial adhesion and proliferation, while maintaining osseointegrative potential.

Data from two different culture conditions of Thalassiosira weissflogii diatom and from cleaning procedures for obtaining monodisperse nanostructured biosilica

Diatoms microalgae produce biosilica nanoporous rigid outershells called frustules that exhibit an intricate nanostructured pore pattern. In this paper two specific Thalassiosira weissflogii culture conditions and size control procedures during the diatoms growth are described. Data from white field and fluorescence microscopy, evaluation of cell densities and cell parameters (k value and R value) according to cell culture conditions are listed. Different cleaning procedures for obtaining bare frustules are described. In addition, FTIR and spectrofluorimetric analyses of cleaned biosilica are shown. The data are related to the research article “Chemically Modified Diatoms Biosilica for Bone Cell Growth with Combined Drug-Delivery and Antioxidant Properties” [1].

Exploiting a new glycerol-based copolymer as a route to wound healing: Synthesis, characterization and biocompatibility assessment.

The use of biocompatible materials based on naturally derived monomers plays a key role in pharmaceutical and cosmetic industries. In this paper we describe the synthesis of a new low molecular weight copolymer, based on glycerol and l-tartaric acid, useful to develop biocompatible dermal patches with drug delivery properties. The copolymers chemical composition was assessed by FT-IR (Fourier transform infrared spectroscopy), (1)H NMR ((1)H Nuclear Magnetic Resonance) and XPS (X-ray photoelectron spectroscopy), while its molecular weight distribution was estimated by SEC (size exclusion chromatography). Copolymer thermal properties were studied by TGA (thermogravimetric analysis). Biological evaluations by MTT assay and SEM (scanning electron microscopy) observations performed with murine fibroblasts and human keratinocytes (HaCaT) revealed a good compatibility of the proposed copolymer. Ciprofloxacin was selected as model drug and its release was evaluated by HPLC (high performance liquid chromatography), showing that the new copolymer supplied promising results as drug delivery system for wound healing applications. Furthermore, investigations on Skin-Mesenchymal stem cells (S-MSCs) behaviour and gene expression showed that the copolymer and its combination with ciprofloxacin did not affect their stemness. In this regard, the fabrication of dermal patches with new, low cost materials for local treatment of skin infections represents an attractive strategy in order to bypass the worrying side effects of systemic antibiotic therapy. Overall, the performed physico-chemical characterization, drug release test and biological evaluations showed that this new copolymer could be a promising tool for the in situ delivery of bioactive molecules during skin lesions treatment.

Antibacterial effectiveness meets improved mechanical properties: Manuka honey/gellan gum composite hydrogels for cartilage repair

Biomaterials for cartilage repair are still far from clinical requirements, even if several studies recently focused on this topic. In this respect, Nature-derived hydrogels are a promising class of scaffolds for cartilage tissue engineering, mimicking the native cellular microenvironment. However, they frequently lack mechanical features required for cartilage applications and are commonly subjected to infection threat. This work describes the innovative use of Manuka honey as molecular spacer for preparing gellan gum-based composites with intrinsic antibacterial properties and superior compressive Youngs modulus in respect of several Nature-derived gels based on chitosan, hyaluronic acid or alginate. The addition of Manuka honey made hydrogels able to inhibit the proliferation of S. aureus and S. epidermidis clinical isolates. Furthermore, no cytotoxic effects were detected on human mesenchymal stem cells seeded on the hydrogels. Moreover, chondrogenesis experiments showed a consistent expression of collagen II and high synthesis of GAGs and proteoglycans, thus indicating the formation of cartilage matrix. Overall, these data suggest that the developed smart composites have a great potential as tools for cartilage tissue engineering.

Multi-compartment scaffold fabricated via 3D-printing as in vitro co-culture osteogenic model

The development of in vitro 3D models to get insights into the mechanisms of bone regeneration could accelerate the translation of experimental findings to the clinic, reducing costs and duration of experiments. This work explores the design and manufacturing of multi-compartments structures in poly(ε-caprolactone) (PCL) 3D-printed by Fused Filament Fabrication technique. The construct was designed with interconnected stalls to host stem cells and endothelial cells. Cells were encapsulated within an optimised gellan gum (GG)-based hydrogel matrix, crosslinked using strontium (Sr2+) ions to exploit its bioactivity and finally, assembled within compartments with different sizes. Calcium (Ca2+)-crosslinked gels were also used as control for comparison of Sr2+ osteogenic effect. The results obtained demonstrated that Sr2+ ions were successfully diffused within the hydrogel matrix and increased the hydrogel matrix strength properties under compressive load. The in vitro co-culture of human-TERT mesenchymal stem cells (TERT- hMSCs) and human umbilical vein endothelial cells (HUVECs), encapsulated within Sr2+ ions containing GG-hydrogels and inter-connected by compartmentalised scaffolds under osteogenic conditions, enhanced cell viability and supported osteogenesis, with a significant increase of alkaline phosphatase activity, osteopontin and osteocalcin respect with the Ca2+-crosslinked GG-PCL scaffolds. These outcomes demonstrate that the design and manufacturing of compartmentalised co-culture of TERT-hMSCs and HUVEC populations enables an effective system to study and promote osteogenesis.

Data on Manuka Honey/Gellan Gum composite hydrogels for cartilage repair

This work contains original data supporting our research paper “Antibacterial effectiveness meets improved mechanical properties: Manuka Honey/Gellan Gum composite hydrogels for cartilage repair”, Bonifacio et al., in press [1], in which innovative composite hydrogels, based on Gellan Gum/Manuka honey/Halloysite nanotubes were described as biomaterials for cartilage regeneration. Here the composites were further examined by means of Fourier Transform Infrared Spectroscopy, in Attenuated Total Reflectance mode (FT-IR/ATR). Materials devoted to cartilage replacement must possess adequate fluid permeability and lubricating capability, therefore, a deeper investigation on water uptake kinetics of freeze-dried specimens up to 21 days in PBS was carried out. Moreover, since the degradation rate of a biomaterial plays a pivotal role in tissue engineering, weight loss measurements of the prepared hydrogels were performed in simulated synovial fluid, in phosphate buffer solution (PBS) and in lysozyme. Scanning Electron Microscopy images provide insight into the morphology of the freeze-dried samples. Finally, additional information on Staphylococcus aureus and Staphylococcus epidermidis ability to adhere onto the prepared hydrogel composites in short times were obtained, as well as the chondrogenic potential of the composites assessed by SDS-PAGE followed by Coomassie blue gel staining.

Simulating Bacteria-Materials Interactions via Agent-Based Modeling

This work reports the outcomes of in silico simulations of the interactions between S. aureus bacteria and an antibacterial polymeric coating developed onto titanium substrates. The aim of the theoretical analysis is to develop a computational approach suitable of predicting the effective amount of antibacterial agents to load onto the polymeric coating in order to prevent titanium implants infections and at the same time to minimize cytotoxicity. The simulations results will be contrasted with experimental data.