Characterization of a Delivery System Based on a Hyaluronic Acid 3D Scaffold and Gelatin Microparticles.

The objective of this study was to develop and characterize a novel hyaluronic acid (HA) 3D scaffold integrated with gelatin microparticles for sustained-delivery applications. To achieve this goal, the delivery microparticles were synthesized and thoroughly characterized, focusing on their crosslinking mechanisms (vanillin and genipin), degradation profiles, and release kinetics. Additionally, the cytotoxicity of the system was assessed, and its impact on the cell adhesion and distribution using mouse fibroblasts was examined. The combination of both biomaterials offers a novel platform for the gradual release of various factors encapsulated within the microparticles while simultaneously providing cell protection, support, and controlled factor dispersion due to the HA 3D scaffold matrix. Hence, this system offers a platform for addressing injure repair by continuously releasing specific encapsulated factors for optimal tissue regeneration. Additionally, by leveraging the properties of HA conjugates with small drug molecules, we can enhance the solubility, targeting capabilities, and cellular absorption, as well as prolong the system stability and half-life. As a result, this integrated approach presents a versatile strategy for therapeutic interventions aimed at promoting tissue repair and regeneration.

Polylactic Acid Nanofiber Membranes Grafted with Carbon Nanotubes with Enhanced Mechanical and Electrical Properties.

Electroconductive materials based on poly(lactic acid) (PLA) electrospinning membranes grafted with carbon nanotubes (CNTs) functionalized with the carboxylic group R-COOH have been obtained. PLA electrospun membranes were modified with sulfuric acid (H2SO4) to oxidize its surface to subsequently graft the CNTs, the treatment time and drying of the membranes before grafting with CNTs being critical, influencing the final properties of the materials. SEM images showed that CNTs presented a uniform distribution on the surface of the PLA nanofibers, while FTIR spectra of PLA-CNTs materials revealed characteristic hydroxyl groups, as evidenced by absorption peaks of CNTs. Thanks to the grafting with CNTs, the resulting PLA-CNTs membranes present an improvement of the mechanical and conductive properties when compared with PLA membranes. On the one hand, grafting with CNTs causes the nanofibers to have greater rigidity, so they are more manipulable and can more easily preserve their conformation when stress is exerted. On the other hand, grafting with CNTs allows elimination of the insulating barrier of the PLA, reducing the resistivity and providing high electrical conductivity to the PLA-CNTs membranes. The incorporation of CNTs into PLA electrospun membranes is expected to offer greater functionalities to electrospun composite nanofibers for medical and industrial applications.

A Strategy for Magnetic and Electric Stimulation to Enhance Proliferation and Differentiation of NPCs Seeded over PLA Electrospun Membranes.

Neural progenitor cells (NPCs) have been shown to serve as an efficient therapeutic strategy in different cell therapy approaches, including spinal cord injury treatment. Despite the reported beneficial effects of NPC transplantation, the low survival and differentiation rates constrain important limitations. Herein, a new methodology has been developed to overcome both limitations by applying a combination of wireless electrical and magnetic stimulation to NPCs seeded on aligned poly(lactic acid) nanofibrous scaffolds for in vitro cell conditioning prior transplantation. Two stimulation patterns were tested and compared, continuous (long stimulus applied once a day) and intermittent (short stimulus applied three times a day). The results show that applied continuous stimulation promotes NPC proliferation and preferential differentiation into oligodendrocytic and neuronal lineages. A neural-like phenotypic induction was observed when compared to unstimulated NPCs. In contrast, intermittent stimulation patterns did not affect NPC proliferation and differentiation to oligodendrocytes or astrocytes morphology with a detrimental effect on neuronal differentiation. This study provides a new approach of using a combination of electric and magnetic stimulation to induce proliferation and further neuronal differentiation, which would improve therapy outcomes in disorders such as spinal cord injury.

Electrical Stimulation Increases Axonal Growth from Dorsal Root Ganglia Co-Cultured with Schwann Cells in Highly Aligned PLA-PPy-Au Microfiber Substrates.

Nerve regeneration is a slow process that needs to be guided for distances greater than 5 mm. For this reason, different strategies are being studied to guide axonal growth and accelerate the axonal growth rate. In this study, we employ an electroconductive fibrillar substrate that is able to topographically guide axonal growth while accelerating the axonal growth rate when subjected to an exogenous electric field. Dorsal root ganglia were seeded in co-culture with Schwann cells on a substrate of polylactic acid microfibers coated with the electroconductive polymer polypyrrole, adding gold microfibers to increase its electrical conductivity. The substrate is capable of guiding axonal growth in a highly aligned manner and, when subjected to an electrical stimulation, an improvement in axonal growth is observed. As a result, an increase in the maximum length of the axons of 19.2% and an increase in the area occupied by the axons of 40% were obtained. In addition, an upregulation of the genes related to axon guidance, axogenesis, Schwann cells, proliferation and neurotrophins was observed for the electrically stimulated group. Therefore, our device is a good candidate for nerve regeneration therapies.

Development and evaluation of hyaluronan nanocomposite conduits for neural tissue regeneration.

Hyaluronan-based hydrogels are among the most promising neural tissue engineering materials because of their biocompatibility and the immunomodulation capabilities of their degradation byproducts. Despite these features, the problems related to their handling and mechanical properties have not yet been solved. In the present work it is proposed to address these drawbacks through the development of nanohybrid materials in which different nanometric phases (carbon nanotubes, mesoporous silica nanoparticles) are embedded in a crosslinked hyaluronan matrix. These nanohybrid matrices were next processed in the shape of cylindrical conduits aimed at promoting and improving neural stem cell differentiation and regeneration in neural tracts. These constructs could be of use specifically for peripheral nerve regeneration. Results of the study show that the inclusion of the different phases improved physico-chemical features of the gel such as its relative electrical permittivity, water intake and elastic modulus, giving hints on how the nanometric phase interacts with hyaluronan in the composite as well as for their potential in combined therapeutic approaches. Regarding the in vitro biological behavior of the hybrid tubular scaffolds, an improved early cell adhesion and survival of Schwann cells in their lumen was found, as compared to conduits made of pure hyaluronan gels. Furthermore, the differentiation and survival of neural precursors was not compromised, despite alleged safety concerns.

BDNF-Gene Transfected Schwann Cell-Assisted Axonal Extension and Sprouting on New PLA-PPy Microfiber Substrates.

The work here reported analyzes the effect of increased efficiency of brain-derived neurotrophic factor (BDNF) production by electroporated Schwann cells (SCs) on the axonal extension in a coculture system on a biomaterial platform that can be of interest for the treatment of injuries of the nervous system, both central and peripheral. Rat SCs are electrotransfected with a plasmid coding for the BDNF protein in order to achieve an increased expression and release of this protein into the culture medium of the cells, performing the best balance between the level of transfection and the number of living cells. Gene-transfected SCs show an about 100-fold increase in the release of BDNF into the culture medium, compared to nonelectroporated SCs. Cocultivation of electroporated SCs with rat dorsal root ganglia (DRG) is performed on highly aligned substrates of polylactic acid (PLA) microfibers coated with the electroconductive polymer polypyrrol (PPy). The coculture of DRG with electrotransfected SCs increase both the axonal extension and the axonal sprouting from DRG neurons compared to the coculture of DRG with nonelectroporated SCs. Therefore, the use of PLA-PPy highly aligned microfiber substrates preseeded with electrotransfected SCs with an increased BDNF secretion is capable of both guiding and accelerating axonal growth.

Axonal extension from dorsal root ganglia on fibrillar and highly aligned poly(lactic acid)-polypyrrole substrates obtained by two different techniques: Electrospun nanofibres and extruded microfibres.

The biological behaviour of Schwann cells (SCs) and dorsal root ganglia (DRG) on fibrillar, highly aligned and electroconductive substrates obtained by two different techniques is studied. Mats formed by nanometer-sized fibres of poly(lactic acid) (PLA) are obtained by the electrospinning technique, while bundles formed by micrometer-sized extruded PLA fibres are obtained by grouping microfibres together. Both types of substrates are coated with the electrically conductive polymer polypyrrole (PPy) and their morphological, physical and electrical characterization is carried out. SCs on micrometer-sized substrates show a higher motility and cell-cell interaction, while a higher cell-material interaction with a lower cell motility is observed for nanometer-sized substrates. This higher motility and cell-cell interaction of SCs on the micrometer-sized substrates entails a higher axonal growth from DRG, since the migration of SCs from the DRG body is accelerated and, therefore, the SCs tapestry needed for the axonal growth is formed earlier on the substrate. A higher length and area of the axons is observed for these micrometer-sized substrates, as well as a higher level of axonal sprouting when compared with the nanometer-sized ones. These substrates offer the possibility of being electrically stimulated in different tissue engineering applications of the nervous system.

Conduits based on the combination of hyaluronic acid and silk fibroin: Characterization, in vitro studies and in vivo biocompatibility.

We address the production of structures intended as conduits made from natural biopolymers, capable of promoting the regeneration of axonal tracts. We combine hyaluronic acid (HA) and silk fibroin (SF) with the aim of improving mechanical and biological properties of HA. The results show that SF can be efficiently incorporated into the production process, obtaining conduits with tubular structure with a matrix of HA-SF blend. HA-SF has better mechanical properties than sole HA, which is a very soft hydrogel, facilitating manipulation. Culture of rat Schwann cells shows that cell adhesion and proliferation are higher than in pure HA, maybe due to the binding motifs contributed by the SF protein. This increased proliferation accelerates the formation of a tight cell layer, which covers the inner channel surface of the HA-SF tubes. Biocompatibility of the scaffolds was studied in immunocompetent mice. Both HA and HA-SF scaffolds were accepted by the host with no residual immune response at 8 weeks. New collagen extracellular matrix and new blood vessels were visible and they were present earlier when SF was present. The results show that incorporation of SF enhances the mechanical properties of the materials and results in promising biocompatible conduits for tubulization strategies.

Elastomeric cardiopatch scaffold for myocardial repair and ventricular support.

OBJECTIVES: Prevention of postischaemic ventricular dilatation progressing towards pathological remodelling is necessary to decrease ventricular wall deterioration. Myocardial tissue engineering may play a therapeutic role due to its capacity to replace the extracellular matrix, thereby creating niches for cell homing. In this experimental animal study, a biomimetic cardiopatch was created with elastomeric scaffolds and nanotechnologies. METHODS: In an experimental animal study in 18 sheep, a cardiopatch was created with adipose tissue-derived progenitor cells seeded into an engineered bioimplant consisting of 3-dimensional bioabsorbable polycaprolactone scaffolds filled with a peptide hydrogel (PuraMatrix™). This patch was then transplanted to cover infarcted myocardium. Non-absorbable poly(ethyl) acrylate polymer scaffolds were used as controls. RESULTS: Fifteen sheep were followed with ultrasound scans at 6 months, including echocardiography scans, tissue Doppler and spectral flow analysis and speckle-tracking imaging, which showed a reduction in longitudinal left ventricular deformation in the cardiopatch-treated group. Magnetic resonance imaging (late gadolinium enhancement) showed reduction of infarct size relative to left ventricular mass in the cardiopatch group versus the controls. Histopathological analysis at 6 months showed that the cardiopatch was fully anchored and integrated to the infarct area with minimal fibrosis interface, thereby promoting angiogenesis and migration of adipose tissue-derived progenitor cells to surrounding tissues. CONCLUSIONS: This study shows the feasibility and effectiveness of a cardiopatch grafted onto myocardial infarction scars in an experimental animal model. This treatment decreased fibrosis, limited infarct scar expansion and reduced postischaemic ventricular deformity. A capillary network developed between our scaffold and the heart. The elastomeric cardiopatch seems to have a positive impact on ventricular remodelling and performance in patients with heart failure.

Bridges of biomaterials promote nigrostriatal pathway regeneration.

Repair of central nervous system (CNS) lesions is difficulted by the lack of ability of central axons to regrow, and the blocking by the brain astrocytes to axonal entry. We hypothesized that by using bridges made of porous biomaterial and permissive olfactory ensheathing glia (OEG), we could provide a scaffold to permit restoration of white matter tracts. We implanted porous polycaprolactone (PCL) bridges between the substantia nigra and the striatum in rats, both with and without OEG. We compared the number of tyrosine-hydroxylase positive (TH+) fibers crossing the striatal-graft interface, and the astrocytic and microglial reaction around the grafts, between animals grafted with and without OEG. Although TH+ fibers were found inside the grafts made of PCL alone, there was a greater fiber density inside the graft and at the striatal-graft interface when OEG was cografted. Also, there was less astrocytic and microglial reaction in those animals. These results show that these PCL grafts are able to promote axonal growth along the nigrostriatal pathway, and that cografting of OEG markedly enhances axonal entry inside the grafts, growth within them, and re-entry of axons into the CNS. These results may have implications in the treatment of diseases such as Parkinson's and others associated with lesions of central white matter tracts. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 107B: 190-196, 2019.

Electrospun polycaprolactone/chitosan scaffolds for nerve tissue engineering: physicochemical characterization and Schwann cell biocompatibility.

Electrospun polycaprolactone (PCL)/chitosan (CH) blend scaffolds with different CH weight ratios were prepared to study the effect of scaffold composition on its physicochemical and biological properties. Scanning electron microscopy showed bead-free homogeneous randomly arranged nanofibers whose average diameter decreased from 240 to 110 nm with increasing CH content. The infrared spectra of the PCL/CH blends were very similar to the neat PCL scaffold. Energy-dispersive x-ray spectroscopy analysis confirmed the presence of carbon, oxygen and nitrogen in the scaffolds, although fluorine-from chemicals used as solvent-was also detected. The water contact angle decreased from 113° (for PCL) to 52° with increasing chitosan content. The biocompatibility was evaluated using fibroblasts and Schwann cell (SC) cultures. Cytotoxicity assays using fibroblasts demonstrated that electrospun scaffolds could be considered as non-cytotoxic material. Biocompatibility tests also revealed that the SCs adhered to scaffolds with different CH content, although the formulation containing CH at 5 wt% exhibited the highest proliferation on days 1 and 3. A better cell distribution was observed in the CH/PCL blends than in the neat PCL or CH scaffolds, where the cells were clustered. Immunochemistry analysis confirmed that SCs expressed the specific p75 cell marker on the scaffolds, suggesting that PCL/CH scaffolds would be good candidates for peripheral nerve tissue engineering.

Neural tissue regeneration in experimental brain injury model with channeled scaffolds of acrylate copolymers.

The objective of the present study was to evaluate the biocompatibility and cell hosting ability of a copolymer scaffold based on ethyl acrylate (EA) and hydroxyl ethyl acrylate (HEA) in vivo after an experimental brain injury. Wistar rats were subjected to cryogenic traumatic brain injury. We evaluated the tissue response to the implanted materials after 8 weeks. The materials were implanted devoid of cells; they provoked a minimal scar response by the host tissue and permitted the invasion of neurons and glia inside them. We also found new blood vessels surrounding and inside the implant. Thus, the copolymer scaffold proves to offer a suitable environment producing a cellular network potentially useful in brain repair after brain injury.

in vitro development of bioimplants made up of elastomeric scaffolds with peptide gel filling seeded with human subcutaneous adipose tissue-derived progenitor cells.

Myocardial tissue lacks the ability to regenerate itself significantly following a myocardial infarction. Thus, new strategies that could compensate this lack are of high interest. Cardiac tissue engineering (CTE) strategies are a relatively new approach that aims to compensate the tissue loss using combination of biomaterials, cells and bioactive molecules. The goal of the present study was to evaluate cell survival and growth, seeding capacity and cellular phenotype maintenance of subcutaneous adipose tissue-derived progenitor cells in a new synthetic biomaterial scaffold platform. Specifically, here we tested the effect of the RAD16-I peptide gel in microporous poly(ethyl acrylate) polymers using two-dimensional PEA films as controls. Results showed optimal cell adhesion efficiency and growth in the polymers coated with the self-assembling peptide RAD16-I. Importantly, subATDPCs seeded into microporous PEA scaffolds coated with RAD16-I maintained its phenotype and were able to migrate outwards the bioactive patch, hopefully toward the infarcted area once implanted. These data suggest that this bioimplant (scaffold/RAD16-I/cells) can be suitable for further in vivo implantation with the aim to improve the function of affected tissue after myocardial infarction.

Bioactive organic-inorganic poly(CLMA-co-HEA)/silica nanocomposites.

A series of novel poly(CLMA-co-HEA)/silica nanocomposites is synthesized from caprolactone 2-(methacryloyloxy)ethyl ester (CLMA) and 2-hydroxyethyl acrylate (HEA) as organic comonomers and the simultaneous sol-gel polymerization of tetraethyloxysilane (TEOS) as silica precursor, in different mass ratios up to a 30 wt% of silica. The nanocomposites are characterized as to their mechanical and thermal properties, water sorption, bioactivity and biocompatibility, reflecting the effect on the organic matrix provided by the silica network formation. The nanocomposites nucleate the growth of hydroxyapatite (HAp) on their surfaces when immersed in the simulated body fluid of the composition used in this work. Proliferation of the MC3T3 osteoblast-like cells on the materials was assessed with the MTS assay showing their biocompatibility. Immunocytochemistry reveals osteocalcin and type I collagen production, indicating that osteoblast differentiation was promoted by the materials, and calcium deposition was confirmed by von Kossa staining. The results indicate that these poly(CLMA-co-HEA)/silica nanocomposites could be a promising biomaterial for bone tissue engineering.

Design and assembly procedures for large-sized biohybrid scaffolds as patches for myocardial infarct.

OBJECTIVE: To assemble a biohybrid cardiac patch consisting of a large (5 × 5 cm) elastomer scaffold whose pores are filled with a self-assembling peptide (SAP) gel entrapping adipose stem cells, to be used as a novel implant in a big animal model (sheep) of myocardial infarction. The study focuses on the way to determine optimal procedures for incorporating the SAP solution and the cells in the patch to ensure cell colonization and a homogeneous cell distribution in the construct before implantation. The problems associated with the scale-up of the different procedures raised by the large size of the construct are discussed. MATERIALS AND METHODS: Experiments were performed to choose between different assembling alternatives: incorporation of the SAP gel before cell seeding or simultaneous SAP and cell loading of the scaffold; surface seeding of cells or cell injection into the scaffold pores; dissemination of the cells throughout the scaffold before incubation by gentle shaking or by centrifugation. Immunocytochemistry techniques and confocal and scanning electron microscopies were employed to assess and quantify cell colonization of the material and early cell distribution. Cell concentrations and the uniformity of cellular distribution throughout the scaffold were taken as the main criteria to decide between the different alternative procedures. RESULTS: The combination of peptide preloading, cell injection, and shaking before incubation yielded the best results in terms of greater cell density and the most uniform distribution after 24 h of culture compared with the other methods. These techniques could be scaled-up to obtain large biohybrid cardiac patches with success. CONCLUSIONS: The results obtained after the different seeding methods allowed us to establish an effective protocol for the assembly of large biohybrid patches for their subsequent implantation in the heart of a big animal model of myocardial infarct in the context of a preclinical study.

Culture of human bone marrow-derived mesenchymal stem cells on of poly(L-lactic acid) scaffolds: potential application for the tissue engineering of cartilage.

PURPOSE: Due to the attractive properties of poly(L-lactic acid) (PLLA) for tissue engineering, the aim was to determine the growth and differentiation capacity of mesenchymal stromal cells (MSCs) in PLLA scaffolds and their potential use in the treatment of cartilage diseases. METHODS: MSCs were cultured in PLLA films and thin porous membranes to study adherence and proliferation. Permeability and porosity were determined for the different scaffolds employed. The optimal conditions for cell seeding were first determined, as well as cell density and distribution inside the PLLA. Scaffolds were then maintained in expansion or chondrogenic differentiation media for 21 days. Apoptosis, proliferation and chondrogenic differentiation was assessed after 21 days in culture by immunohistochemistry. Mechanical characteristics of scaffolds were determined before and after cell seeding. RESULTS: MSCs uniformly adhered to PLLA films as well as to porous membranes. Proliferation was detected only in monolayers of pure PLLA, but was no longer detected after 10 days. Mechanical characterization of PLLA scaffolds showed differences in the apparent compression elastic modulus for the two sizes used. After determining high efficiencies of seeding, the production of extracellular matrix (ECM) was determined and contained aggrecan and collagens type I and X. ECM produced by the cells induced a twofold increase in the apparent elastic modulus of the composite. CONCLUSIONS: Biocompatible PLLA scaffolds have been developed that can be efficiently loaded with MSCs. The scaffold supports chondrogenic differentiation and ECM deposition that improves the mechanics of the scaffold. Although this improvement does not met the expectations of a hyaline-like cartilage ECM, in part due to the lack of a mechanical stimulation, their potential use in the treatment of cartilage pathologies encourages to improve the mechanical component.

One-dimensional migration of olfactory ensheathing cells on synthetic materials: experimental and numerical characterization.

Olfactory ensheathing cells (OECs) are of great interest for regenerative purposes since they are believed to aid axonal growth. With the view set on the strategies to achieve reconnection between neuronal structures, it is of great importance to characterize the behaviour of these cells on long thread-like structures that may efficiently guide cell spread in a targeted way. Here, rat OECs were studied on polycaprolactone (PCL) long monofilaments, on long bars and on discs. PCL turns out to be an excellent substrate for OECs. The cells cover long distances along the monofilaments and colonize completely these structures. With the help of a one-dimensional (1D) analytical model, a migration coefficient, a net proliferation rate constant and the fraction of all cells which undergo migration were obtained. The separate effect of the three phenomena summarized by these parameters on the colonization patterns of the 1D path was qualitatively discussed. Other features of interest were also determined, such as the speed of the advance front of colonization and the order of the kinetics of net cell proliferation. Characterizing migration by means of these quantities may be useful for comparing and predicting features of the colonization process (such as times, patterns, advance fronts and proportion of motile cells) of different cell-substrate combinations.

Fibronectin activity on substrates with controlled --OH density.

Adhesion of human fibroblast to a family of fibronectin (FN) coated model substrates consisting of copolymers of ethyl acrylate and hydroxyl ethylacrylate in different ratios to obtain a controlled surface density of --OH groups was investigated. Cell adhesion and spreading surprisingly decreased as the fraction of --OH groups on the surface increased. AFM studies of FN conformation revealed formation of a protein network on the more hydrophobic surfaces. The density of this network diminished as the fraction of --OH groups in the sample increased, up to a maximal --OH concentration at which, instead of the network, only FN aggregates were observed. The kinetics of network development was followed at different adsorption times. Immunofluorescence for vinculin revealed the formation of well-developed focal adhesion complexes on the more hydrophobic surface (similar to the control glass), which became less defined as the fraction of --OH groups increased. Thus, the efficiency of cell adhesion is enhanced by the formation of FN networks on the substrate, directly revealing the importance of the adsorbed protein conformation for cell adhesion. However, cell-dependent reorganization of substrate-associated FN, which usually takes place on more hydrophilic substrates (as do at the control glass slides), was not observed in this system, suggesting the increased strength of protein-to-substrate interaction. Instead, the late FN matrix formation--after 3 days of culture--was again better pronounced on the more hydrophobic substrates and decreased as the fraction of --OH groups increase, which is in a good agreement with the results for overall cell morphology and focal adhesion formation.

Fibrinogen patterns and activity on substrates with tailored hydroxy density.

The influence of the surface fraction of OH groups on fibrinogen (FG) adsorption is investigated in copolymers of ethyl acrylate and hydroxy ethylacrylate. The amount of adsorbed FG, quantified by western-blotting combined with image analysis of the corresponding bands, decreases as the hydrophilicity of the substrate increases. The influence of substrate wettability on FG conformation and distribution is observed by atomic force microscopy (AFM). The most hydrophobic substrate promotes FG fibrillogenesis, which leads to a fibrin-like appearance in the absence of any thrombin. The degree of FG interconnection was quantified by calculating the fractal dimension of the adsorbed protein from image analysis of the AFM results. The biological activity of the adsorbed FG is correlated to cell adhesion on FG-coated substrates.

Substrate-induced assembly of fibronectin into networks: influence of surface chemistry and effect on osteoblast adhesion.

The influence of surface chemistry-substrates with controlled surface density of -OH groups-on fibronectin (FN) conformation and distribution is directly observed by atomic force microscopy (AFM). FN fibrillogenesis, which is known to be a process triggered by interaction with integrins, is shown in our case to be induced by the substrate (in absence of cells), which is able to enhance FN-FN interactions leading to the formation of a protein network on the material surface. This phenomenon depends both on surface chemistry and protein concentration. The level of the FN fibrillogenesis was quantified by calculating the fractal dimension of the adsorbed protein from image analysis of the AFM results. The total amount of adsorbed FN is obtained by making use of a methodology that employs Western blotting combined with image analysis of the corresponding protein bands, with the lowest sensitivity threshold equal to 15 ng of adsorbed protein. Further, FN adsorption is correlated to human osteoblast adhesion through morphology and actin cytoskeleton formation. Actin polymerization is in need of the formation of the protein network on the substrate's surface. Cell morphology is more rounded (as quantified by calculating the circularity of the cells by image analysis) when the degree of FN fibrillogenesis on the substrate is lower.