Bioactive coatings

From traditional approaches of employing bulk materials to the new generation of bioactive coated implants, the design of such medical tools is being directed towards the implementation bioactive compounds to allow the direct bonding of living tissues and osteoconduction. However, the development of an optimal bioactive implant for tissue regeneration has not been achieved. The research for novel materials is hindered by the biocompatibility and bioactivity of the compound as well as their mechanical properties. To improve the bioactivity of the implants, the increase of surface area of the implant as well as the use of resorbable compounds is being studied with promising results. Among all different materials and composite employed, the common materials include calcium phosphates and resorbable bioglasses inspired in natural scaffold composition of bones and teeth. In some cases, this material is being used as a coating and combined with further treatments and functional coatings which may reinforce its bioresponsive properties, and in some cases, it can provide additional properties such as antimicrobial activity. In addition, a specific class of bioactive coatings based on biodegradable polymers has also been developed. These coatings temporally aim at accelerating wound healing and forming new tissue at the material-tissue interface around implanted devices or protecting those implants against biomaterial-associated infections. Bioactive, degradable coatings can be generated both from natural and synthetic polymers. Common strategies, reviewed here, are based on natural polymers like proteins, polysaccharides, or glycosaminoglycanes to improve their bioactivity either by chemical functionalization of the biopolymer itself (e.g. introduction of bioactive groups) or by immobilization of bioactive components (e.g. cell adhesion peptides). Degradable or at least water-soluble synthetic polymers as polylactones or polyethylene glycols have been used for long time to create carrier materials for bioactive agents. As exemplary illustrated, those polymers are also used creating either substrate-adhering nanofilms or hydrogel-based thick coatings with high bioactivity to stimulate cell adhesion or avoid microbial adhesion. This chapter aims to summarize all recent approaches in the development of various bioactive coating materials, as well as the coating techniques and further treatment, functionalization and surface modification

Modifications of Hyaluronan Influence the Interaction with Human Bone Morphogenetic Protein-4 (hBMP-4).

n this study, we have demonstrated that the modification of hyaluronan (hyaluronic acid; Hya) with sulfate groups led to different binding affinities for recombinant human bone morphogenetic protein-4 (rhBMP-4). The high-sulfated sHya2.8 (average degree of sulfation (D.S.) 2.8) exhibited the tightest interaction with rhBMP-4, followed by the low-sulfated sHya1.0, as determined with surface plasmon resonance (SPR), ELISA, and competition ELISA. Unmodified Hya, chondroitin-sulfate (CS), and heparan sulfate (HS) showed significantly less binding affinity. SPR data could be fitted to an A + B = AB Langmuir model and binding constants were evaluated ranging from 13 pM to 5.45 microM. The interaction characteristics of the differentially sulfated Hyas are promising for the incorporation of these modified polysaccharides in bioengineered coatings of biomaterials for medical applications

Tendon-like Electrospun PLGA Scaffolds with Optimized Physical Cues Induced Tenogenic Differentiation and Boosted Immunomodulatory Properties on Amniotic Epithelial Stem Cells.

Introduction: The advanced strategies in the field of Tissue Engineering might render possible overcoming the unsatisfactory results of conventional treatments to deal with tendinopathies. In this context, the design of tendon biomimetic electrospun scaffolds engineered with Amniotic Epithelial Stem Cells (AECs), which have shown a high teno-regenerative and immunomodulatory potential in tendon-defect models, can represent a promising solution for tendon regeneration. Methods: Poly(lactide-co-glycolic) acid (PLGA) scaffolds were fabricated using the electrospinning technique to mimic the native tendon biomechanics and extracellular matrix by optimizing: fiber alignment and diameter size (1.27 and 2.5 µm), and surface chemistry using the Cold Atmospheric Plasma (CAP) Technique. Moreover, the teno-inductive and immunomodulatory effects of these parameters on AECs have been also assessed. Results: The fabricated PLGA scaffolds with highly aligned fibers and small diameter size (1.27 µm) induced a stepwise tenogenic differentiation on AECs with an early epithelial-mesenchymal transition (EMT), followed by their tenogenic differentiation. Indeed, SCX, an early tendon marker, was significantly more efficiently translated into the downstream effector TNMD, a mature tendon marker. Moreover, 1.27 µm fiber diameter induced on AECs a higher expression of anti-inflammatory interleukin mRNAs (IL-4 and IL-10). The CAP treated PLGA scaffolds showed an improved cell adhesion and infiltration without altering their topological structure and teno-inductive properties. In fact, AECs engineered with CAP treated fibers, expressed in their cytoplasm TNMD. Moreover, CAP treatment did not alter the mechanical properties of PLGA scaffolds. Conclusions: The developed electrospun PLGA scaffolds with the optimized features represent an ideal tendon-like construct that could be applied in in-vivo models to evaluate their biosafety and teno-regenerative potential

Amniotic Epithelial Stem Cells Counteract Acidic Degradation By-Products of Electrospun PLGA Scaffold by Improving their Immunomodulatory Profile In Vitro

Electrospun poly(lactic-co-glycolic acid) (PLGA) scaffolds with highly aligned fibers (ha-PLGA) represent promising materials in the field of tendon tissue engineering (TE) due to their characteristics in mimicking fibrous extracellular matrix (ECM) of tendon native tissue. Among these properties, scaffold biodegradability must be controlled allowing its replacement by a neo-formed native tendon tissue in a controlled manner. In this study, ha-PLGA were subjected to hydrolytic degradation up to 20 weeks, under di-H2 O and PBS conditions according to ISO 10993-13:2010. These were then characterized for their physical, morphological, and mechanical features. In vitro cytotoxicity tests were conducted on ovine amniotic epithelial stem cells (oAECs), up to 7 days, to assess the effect of non-buffered and buffered PLGA by-products at different concentrations on cell viability and their stimuli on oAECs’ immunomodulatory properties. The ha-PLGA scaffolds degraded slowly as evidenced by a slight decrease in mass loss (14%) and average molecular weight (35%), with estimated degradation half-time of about 40 weeks under di-H2 O. The ultrastructure morphology of the scaffolds showed no significant fiber degradation even after 20 weeks, but alteration of fiber alignment was already evident at week 1. Moreover, mechanical properties decreased throughout the degradation times under wet as well as dry PBS conditions. The influence of acid degradation media on oAECs was dose-dependent, with a considerable effect at 7 days’ culture point. This effect was notably reduced by using buffered media. To a certain level, cells were able to compensate the generated inflammation-like microenvironment by upregulating IL-10 gene expression and favoring an anti-inflammatory rather than pro-inflammatory response. These in vitro results are essential to better understand the degradation behavior of ha-PLGA in vivo and the effect of their degradation by-products on affecting cell performance. Indeed, buffering the degradation milieu could represent a promising strategy to balance scaffold degradation. These findings give good hope with reference to the in vivo condition characterized by physiological buffering systems

Tendon biomimetic 3D scaffold enhance amniotic epithelial stem cells biological potential

Tendon tissue engineering represents an emerging field whose aim focuses on the design of 3D tendon biomimetic scaffolds that should ideally combine adequate physical, mechanical, biological and functional properties of the native tissue. In this research, it was designed a bundle tendon-like PLGA 3D scaffold with highly aligned fibers on which the structure and mechanical properties were evaluated. Moreover, it was assessed scaffold’s teno-differentiative and immuno-inductive ability on amniotic epithelial stem cells (AECs). The fabricated PLGA 3D scaffolds mimic macroscopically and microscopically the structure of native tendon tissue and its biomechanical properties. Biologically, AECs seeded on the fabricated 3D scaffolds acquired a spindle tenocyte-like morphology after just 24h compared to the AECs cultured on petri dishes (CTR) which maintained their cobblestone morphology. The phenotypic change of the engineered AECs was also confirmed by visualizing TNMD protein expression, a mature tendon marker, within their cytoplasm and supported by the analysis of tendon-related genes (SCX, COL1, and TNMD) that were significantly upregulated at 7-day culture, while no TNMD protein expression or significant increase in tendon-related genes was found in CTR cells. Moreover, the 3D construct induced on AECs an upregulation of IL-10, an anti-inflammatory cytokine, maintaining basal levels of IL-12, a pro-inflammatory cytokine, showing a favorable IL10/IL12 ratio. In conclusion, the fabricated PLGA 3D scaffolds are tendon biomimetic in terms of ultrastructure and biomechanics, making them also suitable for surgical purposes. Moreover, these constructs revealed a high teno- and immuno-inductive potential on AECs and thus represent potential candidates for tendon regeneration

Artificial Extracellular Matrices Containing Bioactive Glass Nanoparticles Promote Osteogenic Differentiation in Human Mesenchymal Stem Cells

The present study analyzes the capacity of collagen (coll)/sulfated glycosaminoglycan (sGAG)-based surface coatings containing bioactive glass nanoparticles (BGN) in promoting the osteogenic differentiation of human mesenchymal stroma cells (hMSC). Physicochemical charac teristics of these coatings and their effects on proliferation and osteogenic differentiation of hMSC were investigated. BGN were stably incorporated into the artificial extracellular matrices (aECM). Oscillatory rheology showed predominantly elastic, gel-like properties of the coatings. The complex viscosity increased depending on the GAG component and was further elevated by adding BGN. BGN-containing aECM showed a release of silicon ions as well as an uptake of calcium ions. hMSC were able to proliferate on coll and coll/sGAG coatings, while cellular growth was delayed on aECM containing BGN. However, a stimulating effect of BGN on ALP activity and calcium deposition was shown. Furthermore, a synergistic effect of sGAG and BGN was found for some donors. Our findings demonstrated the promising potential of aECM and BGN combinations in promoting bone regeneration. Still, future work is required to further optimize the BGN/aECM combination for increasing its combined osteogenic effect

Artificial Extracellular Matrices Containing Bioactive Glass Nanoparticles Promote Osteogenic Differentiation in Human Mesenchymal Stem Cells

The present study analyzes the capacity of collagen (coll)/sulfated glycosaminoglycan (sGAG)-based surface coatings containing bioactive glass nanoparticles (BGN) in promoting the osteogenic differentiation of human mesenchymal stroma cells (hMSC). Physicochemical characteristics of these coatings and their effects on proliferation and osteogenic differentiation of hMSC were investigated. BGN were stably incorporated into the artificial extracellular matrices (aECM). Oscillatory rheology showed predominantly elastic, gel-like properties of the coatings. The complex viscosity increased depending on the GAG component and was further elevated by adding BGN. BGN-containing aECM showed a release of silicon ions as well as an uptake of calcium ions. hMSC were able to proliferate on coll and coll/sGAG coatings, while cellular growth was delayed on aECM containing BGN. However, a stimulating effect of BGN on ALP activity and calcium deposition was shown. Furthermore, a synergistic effect of sGAG and BGN was found for some donors. Our findings demonstrated the promising potential of aECM and BGN combinations in promoting bone regeneration. Still, future work is required to further optimize the BGN/aECM combination for increasing its combined osteogenic effect

Electrospun poly(d/l-lactide-co-l-lactide) hybrid matrix: a novel scaffold material for soft tissue engineering

Electrospinning is a long-known polymer processing technique that has received more interest and attention in recent years due to its versatility and potential use in the field of biomedical research. The fabrication of three-dimensional (3D) electrospun matrices for drug delivery and tissue engineering is of particular interest. In the present study, we identified optimal conditions to generate novel electrospun polymeric scaffolds composed of poly-d/l-lactide and poly-l-lactide in the ratio 50:50. Scanning electron microscopic analyses revealed that the generated poly(d/l-lactide-co-l-lactide) electrospun hybrid microfibers possessed a unique porous high surface area mimicking native extracellular matrix (ECM). To assess cytocompatibility, we isolated dermal fibroblasts from human skin biopsies. After 5 days of in vitro culture, the fibroblasts adhered, migrated and proliferated on the newly created 3D scaffolds. Our data demonstrate the applicability of electrospun poly(d/l-lactide-co-l-lactide) scaffolds to serve as substrates for regenerative medicine applications with special focus on skin tissue engineering

Global Analysis of Proline-Rich Tandem Repeat Proteins Reveals Broad Phylogenetic Diversity in Plant Secretomes

Cell walls, constructed by precisely choreographed changes in the plant secretome, play critical roles in plant cell physiology and development. Along with structural polysaccharides, secreted proline-rich Tandem Repeat Proteins (TRPs) are important for cell wall function, yet the evolutionary diversity of these structural TRPs remains virtually unexplored. Using a systems-level computational approach to analyze taxonomically diverse plant sequence data, we identified 31 distinct Pro-rich TRP classes targeted for secretion. This analysis expands upon the known phylogenetic diversity of extensins, the most widely studied class of wall structural proteins, and demonstrates that extensins evolved before plant vascularization. Our results also show that most Pro-rich TRP classes have unexpectedly restricted evolutionary distributions, revealing considerable differences in plant secretome signatures that define unexplored diversity