Engineering bio-adhesive functions in an antimicrobial polymer multilayer

Bioselectivity of silk protein-based materials and their bio-inspired applications

Adhesion to material surfaces is crucial for almost all organisms regarding subsequent biological responses. Mammalian cell attachment to a surrounding biological matrix is essential for maintaining their survival and function concerning tissue formation. Conversely, the adhesion and presence of microbes interferes with important multicellular processes of tissue development. Therefore, tailoring bioselective, biologically active, and multifunctional materials for biomedical applications is a modern focus of biomaterial research. Engineering biomaterials that stimulate and interact with cell receptors to support binding and subsequent physiological responses of multicellular systems attracted much interest in the last years. Further to this, the increasing threat of multidrug resistance of pathogens against antibiotics to human health urgently requires new material concepts for preventing microbial infestation and biofilm formation. Thus, materials exhibiting microbial repellence or antimicrobial behaviour to reduce inflammation, while selectively enhancing regeneration in host tissues are of utmost interest. In this context, protein-based materials are interesting candidates due to their natural origin, biological activity, and structural properties. Silk materials, in particular those made of spider silk proteins and their recombinant counterparts, are characterized by extraordinary properties including excellent biocompatibility, slow biodegradation, low immunogenicity, and non-toxicity, making them ideally suited for tissue engineering and biomedical applications. Furthermore, recombinant production technologies allow for application-specific modification to develop adjustable, bioactive materials. The present review focusses on biological processes and surface interactions involved in the bioselective adhesion of mammalian cells and repellence of microbes on protein-based material surfaces. In addition, it highlights the importance of materials made of recombinant spider silk proteins, focussing on the progress regarding bioselectivity.

3D silicon doped hydroxyapatite scaffolds decorated with Elastin-like Recombinamers for bone regenerative medicine

The current study reports on the manufacturing by rapid prototyping technique of three-dimensional (3D) scaffolds based on silicon substituted hydroxyapatite with Elastin-like Recombinamers (ELRs) functionalized surfaces. Silicon doped hydroxyapatite (Si-HA), with Ca₁₀(PO₄)_5.7(SiO₄)_0.3(OH)_1.7h_0.3 nominal formula, was surface functionalized with two different types of polymers designed by genetic engineering: ELR-RGD that contain cell attachment specific sequences and ELR-SN_A15/RGD with both hydroxyapatite and cells domains that interact with the inorganic phase and with the cells, respectively. These hybrid materials were subjected to in vitro assays in order to clarify if the ELRs coating improved the well-known biocompatible and bone regeneration properties of calcium phosphates materials. The in vitro tests showed that there was a total and homogeneous colonization of the 3D scaffolds by Bone marrow Mesenchymal Stromal Cells (BMSCs). In addition, the BMSCs were viable and able to proliferate and differentiate into osteoblasts.

STATEMENT OF SIGNIFICANCE

Bone tissue engineering is an area of increasing interest because its main applications are directly related to the rising life expectancy of the population, which promotes higher rates of several bone pathologies, so innovative strategies are needed for bone tissue regeneration therapies. Here we use the rapid prototyping technology to allow moulding ceramic 3D scaffolds and we use different bio-polymers for the functionalization of their surfaces in order to enhance the biological response. Combining the ceramic material (silicon doped hydroxyapatite, Si-HA) and the Elastin like Recombinamers (ELRs) polymers with the presence of the integrin-mediate adhesion domain alone or in combination with SNA15 peptide that possess high affinity for hydroxyapatite, provided an improved Bone marrow Mesenchymal Stromal Cells (BMSCs) differentiation into osteoblastic linkage.

Functionalized self-assembly polypeptide hydrogel scaffold applied in modulation of neural progenitor cell behavior

Three-dimensional cell culturing provides an appealing biomimetic platform to probe the biological effects of a designed extracellular matrix on the behavior of seeded neural stem or neural progenitor cells. This culturing model serves as an important tool to investigate functional regulators involved in proliferation and differentiation of neural progenitor cells. This study aims to reconstruct a polypeptide hydrogel matrix functionally integrated with cyclo-RGD motif [c(RGDfK)] for initial exploration of neural progenitor cell behavior in three-dimensional culture. Three types of hydrogel scaffolds including Type I collagen, RADA16 self-assembly peptide, and RADA16-c(RGDfK) self-assembly peptide hydrogel were employed to serve as the culturing extracellular matrix of neonatal rat spinal neural progenitor cells. The neural adhesion of functionalized self-assembly peptide hydrogel was acquired prior to its RADA16 counterpart with neural progenitor cell seeding tests. The biophysiological properties of self-assembly peptide hydrogel scaffolds were then detected by scanning electron microscopy and rheology measurements. The biological behavior of embedded neural progenitor cells including cell proliferation and differentiation in three-dimensional niche were analyzed by MTT [(3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide)] tests and immunocytochemistry fluorescence staining. The 1% (w/v) RADA16-c(RGDfK) hydrogel scaffold [R16-c(RGDfK)HS] demonstrated an elastic modulus(312 ± 5.7 Pa) compatible with central neural cells, which significantly facilitated the proliferation of embedded neural progenitor cells. Compared to collagen hydrogel, both RADA16 and RADA16-c(RGDfK) hydrogel scaffold improved the cellular proliferation and neuronal differentiation of neural progenitor cells in a three-dimensional culture model. In order to model neuronal regeneration, introduction of neurotrophin-3 in the differentiation environment significantly increased the neuronal differentiation in which the ratio of Tuj-1-positive cell number increased to 72.5% ± 4.7% in the c(RGDfK)-functionalized three-dimensional matrix environment at 7 days in culture. Collectively, the present R16-c(RGDfK)HS displays excellent central neural biocompatibility and emerges as a promising bioengineered extracellular matrix niche of neural stem or progenitor cells, building a solid foundation for the subsequent in vitro and in vivo studies including neural repair, regeneration, and development.

Quercitrin-nanocoated titanium surfaces favour gingival cells against oral bacteria

Many dental implants fail due to the infection and inflammation that walk hand in hand with poor healing and soft tissue integration. Titanium surfaces were nanocoated with quercitrin, a natural flavonoid, with the aim to improve soft tissue integration and increase dental implants success. Streptococcus mutans attachment and biofilm formation was analysed. Then, the anti-inflammatory properties and the potential of quercitrin-nanocoated surfaces to boost soft tissue regeneration were tested using human gingival fibroblasts. An inflammatory situation was mimicked using interleulin-1-beta. We found that quercitrin-nanocoated surfaces decreased initial bacterial adhesion while increasing human gingival fibroblasts attachment. Furthermore, quercitrin-nanocoated Ti increased collagen mRNA levels and decreased matrix metalloproteinase-1/tissue inhibitor of metalloproteinanse-1 mRNA ratio, which is related to a reduced metalloproteinase-mediated collagen degradation, while also decreasing the pro-inflammatory prostaglandin E₂ release under basal and inflammatory conditions. These results suggest that quercitrin-nanocoated surfaces could enhance the soft tissue integration and increase dental implants success.