Fluorescein isothiocyanate-labeled human plasma fibronectin in extracellular matrix remodeling

Effects of excipients on the interactions of self-emulsifying drug delivery systems with human blood plasma and plasma membranes

Due to its versatility in formulation and manufacturing, self-emulsifying drug delivery systems (SEDDS) can be used to design parenteral formulations. Therefore, it is necessary to understand the effects of excipients on the behavior of SEDDS formulations upon parenteral administration, particularly their interactions with blood plasma and cell membranes. In this study, we prepared three neutrally charged SEDDS formulations composed of medium-chain triglycerides as the oil phase, polyoxyl-35 castor oil (EL35) and polyethylene glycol (15)-hydroxystearate (HS15) as the nonionic surfactants, medium-chain mono- and diglycerides as the co-surfactant, and propylene glycol as the co-solvent. The cationic surfactant, didodecyldimethylammonium bromide (DDA), and the anionic surfactant, sodium deoxycholate (DEO), were added to the neutral SEDDS preconcentrates to obtain cationic and anionic SEDDS, respectively. SEDDS were incubated with human blood plasma and recovered by size exclusion chromatography. Data showed that SEDDS emulsion droplets can bind plasma protein to different extents depending on their surface charge and surfactant used. At pH 7.4, the least protein binding was observed with anionic SEDDS. Positive charges increased protein binding. SEDDS stabilized by HS15 can adsorb more plasma protein and induce more plasma membrane disruption activity than SEDDS stabilized by EL35. These effects were more pronounced with the HS15 + DDA combination. The addition of DDA and DEO to SEDDS increased plasma membrane disruption (PMD) activities, and DDA (1% w/w) was more active than DEO (2% w/w). PMD activities of SEDDS were concentration-dependent and vanished at appropriate dilution ratios.

Integrating Metabolic Oligosaccharide Engineering and SPAAC Click Chemistry for Constructing Fibrinolytic Cell Surfaces

To effectively solve the problem of significant loss of transplanted cells caused by thrombosis during cell transplantation, this study simulates the human fibrinolytic system and combines metabolic oligosaccharide engineering with strain-promoted azide-alkyne cycloaddition (SPAAC) click chemistry to construct a cell surface with fibrinolytic activity. First, a copolymer (POL) of oligoethylene glycol methacrylate (OEGMA) and 6-amino-2-(2-methylamido)hexanoic acid (Lys) was synthesized by reversible addition-fragmentation chain transfer (RAFT) copolymerization, and the dibenzocyclooctyne (DBCO) functional group was introduced into the side chain of the copolymer through an active ester reaction, resulting in a functionalized copolymer DBCO-PEG4-POL with ε-lysine ligands. Then, azide functional groups were introduced onto the surface of HeLa model cells through metabolic oligosaccharide engineering, and DBCO-PEG4-POL was further specifically modified onto the surface of HeLa cells via the SPAAC "click" reaction. In vitro investigations revealed that compared with unmodified HeLa cells, modified cells not only resist the adsorption of nonspecific proteins such as fibrinogen and human serum albumin but also selectively bind to plasminogen in plasma while maintaining good cell viability and proliferative activity. More importantly, upon the activation of adsorbed plasminogen into plasmin, the modified cells exhibited remarkable fibrinolytic activity and were capable of promptly dissolving the primary thrombus formed on their surfaces. This research not only provides a novel approach for constructing transplantable cells with fibrinolytic activity but also offers a new perspective for effectively addressing the significant loss of transplanted cells caused by thrombosis.

Electroactive 4D Porous Scaffold Based on Conducting Polymer as a Responsive and Dynamic In Vitro Cell Culture Platform

In vivo, cells reside in a 3D porous and dynamic microenvironment. It provides biochemical and biophysical cues that regulate cell behavior in physiological and pathological processes. In the context of fundamental cell biology research, tissue engineering, and cell-based drug screening systems, a challenge is to develop relevant in vitro models that could integrate the dynamic properties of the cell microenvironment. Taking advantage of the promising high internal phase emulsion templating, we here designed a polyHIPE scaffold with a wide interconnected porosity and functionalized its internal 3D surface with a thin layer of electroactive conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) to turn it into a 4D electroresponsive scaffold. The resulting scaffold was cytocompatible with fibroblasts, supported cellular infiltration, and hosted cells, which display a 3D spreading morphology. It demonstrated robust actuation in ion- and protein-rich complex culture media, and its electroresponsiveness was not altered by fibroblast colonization. Thanks to customized electrochemical stimulation setups, the electromechanical response of the polyHIPE/PEDOT scaffolds was characterized in situ under a confocal microscope and showed 10% reversible volume variations. Finally, the setups were used to monitor in real time and in situ fibroblasts cultured into the polyHIPE/PEDOT scaffold during several cycles of electromechanical stimuli. Thus, we demonstrated the proof of concept of this tunable scaffold as a tool for future 4D cell culture and mechanobiology studies.

Modulation of Cell Response through the Covalent Binding of Fibronectin to Titanium Substrates

Titanium (Ti-6Al-4V) substrates were functionalized through the covalent binding of fibronectin, and the effect of the existence of this extracellular matrix protein on the surface of the material was assessed by employing mesenchymal stem cell (MSC) cultures. The functionalization process comprised the usage of the activation vapor silanization (AVS) technique to deposit a thin film with a high surface density of amine groups on the material, followed by the covalent binding of fibronectin to the amine groups using the N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride/N-hydroxysuccinimide (EDC/NHS) crosslinking chemistry. The biological effect of the fibronectin on murine MSCs was assessed in vitro. It was found that functionalized samples not only showed enhanced initial cell adhesion compared with bare titanium, but also a three-fold increase in the cell area, reaching values comparable to those found on the polystyrene controls. These results provide compelling evidence of the potential to modulate the response of the organism to an implant through the covalent binding of extracellular matrix proteins on the prosthesis.

Development and validation of a label-free method for measuring the collagen hydrolytic activity of protease

Collagen is the most abundant fibrous structural protein, and therefore, the quantitative evaluation of the effect of protease on collagen has a profound influence on enzyme application. In this research, unlabeled native bovine hide powder was utilized to detect collagen hydrolytic activity of the protease. The optimum conditions of the determination method were as follows: 30 mg/mL substrate concentration, 30 min reaction time, and 2-9 U/mL enzyme concentration. Then, several typical industrial protease preparations were chosen to measure collagenolytic activities at different temperatures and pH values, whose change trends were quite distinct from those of proteolytic activity assay method based on casein or dye-labeled hide powder substrate. Especially, in the pH 5-7, casein hydrolytic activities of these proteases showed sharper peaks with relative activity from 6% to 100%, whereas, their collagen hydrolytic activities based on native hide powder exhibited 30-100% with broader peaks. And collagen hydrolytic activities resulted from using dye-labeled substrate reached a lower optimum pH value than that of other methods. Besides, the results of these measurements displayed a moderate degree of reproducibility. This method is more reasonable than the protease assay method using casein or labeled hide powder as the substrate in many fields.

Synthesis and Photophysical Properties of Fluorescein Esters as Potential Organic Semiconductor Materials

Fluorescein (1), a known fluorescent tracer in microscopy with high photophysical properties, was esterified to have fluorescein ethyl ester (2) and O-ethyl-fluorescein ethyl ester (3) in excellent yields. All of them were investigated for the photophysical and electrochemical properties as potential organic semiconductor materials. Absorptions and emission spectra were taken in various solvents, compound 2 showed emission maxima at λ_max = 545 and compound 3 showed λ_max = 550 nm. Optical band gap energy (E_g) was calculated for 1-3 and the values were found in between 2.34 - 2.39 eV. Possibility of shifting emission maxima was studied in various pH (5-9) buffers, and finally the thermal stability was examined using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Increasing of conjugation system of 2 and 3 were studied by HOMO and LUMO distributions of 1-3. Experimental results showed that compounds 2 and 3 have excellent photophysical and electrochemical properties hence can be used as excellent organic semiconductor materials.

Pore size modulates in vitro osteogenesis of bone marrow mesenchymal stem cells in fibronectin/gelatin coated silk fibroin scaffolds

Porous scaffolds have been widely used for bone tissue engineering (BTE), and the pore structure of scaffolds plays an important role in osteogenesis. Silk fibroin (SF) is a favorable biomaterial for BTE due to its excellent mechanical property, biocompatibility, and biodegradation, but the lack of cell attachment sites in SF chemical structure resulted in poor cell-material interactions. In this study, SF scaffolds were coated with fibronectin/gelatin (Fn/G) to improve cell adhesion. Furthermore, the effect of pore size in Fn/G coated SF scaffolds on osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) were investigated in vitro. Scaffolds with average pore diameters of 384.52, 275.23, and 173.8 μm were prepared by salt leaching method, labelled as Large, Medium, and Small group. Porcine BMSCs were seeded on scaffolds and cultured in osteogenic medium for 21 days to evaluate cell proliferation, alkaline phosphatase (ALP) activity, calcium deposition, gene expression of osteogenic markers, and histological performance. The results showed Fn/G coating effectively improved cell adhesion on SF scaffolds. Cell metabolic rate in each group increased significantly with time, but there was no statistical difference at each time point among the three groups. On day 21, ALP/DNA and calcium/DNA in the Small group were significantly higher than those in the Large group. Among the three pore sizes, the Small group showed higher mRNA expression of COl I on day 7, OPN on day 14, and OCN on day 21. Immunohistochemical staining on day 21 showed that Col I and OCN in Small group were more highly expressed. In conclusion, the Fn/G coated SF scaffolds with a mean pore diameter of 173.8 μm was optimal for osteogenic differentiation of BMSC in vitro.

Fibronectin adsorption on oxygen plasma-treated polyurethane surfaces modulates endothelial cell response

Fibronectin coating increases implant biocompatibility by enhancing surface endothelialization via integrin-mediated binding.

Delivering Proangiogenic Factors from 3D-Printed Polycaprolactone Scaffolds for Vascularized Bone Regeneration

Natural bone is a highly vascularized tissue that relies on the vasculature for blood and nutrients supply to maintain skeletal integrity. Inadequacy of neovascularization may compromise the tissue ingrowth to the implanted scaffolds, and eventually results in failure for the repair. To tackle this issue and enhance self-vascularized bone regeneration, herein a 3D biomimetic selective lasersintering (SLS) derived scaffold, with an angiogenic growth factor immobilized on its surface, that can be released in a controlled manner is proposed. To this end, a porous polycaprolactone/hydroxyapatite (PCL/HA) scaffold is prepared via the SLS technique, which is further modified with vascular endothelial growth factor (VEGF) by coprecipitation with apatite. The resultant scaffold (PCL/HA/VEGF) has an excellent cytocompatibility, and subcutaneous implantation experiment shows that the VEGF-loaded scaffold significantly enhances the blood vessel formation compared with the VEGF-free control. It is further demonstrated that the PCL/HA/VEGF scaffold is able to enhance the in vivo bone regeneration in a rat cranial defect model. Taken together, the current study provides not only a feasible and promising scaffold candidate to enhance the vascularized bone regeneration, but also a general strategy to overcome the inadequate vascularization issue for the repair of other tissue and organs.

Human pancreatic tissue dissociation enzymes for islet isolation: Advances and clinical perspectives

BACKGROUND AND AIMS

Successful clinical human allo or auto-islet transplantation requires the recovery of a sufficient number of functional islets from either brain-dead or chronic pancreatitis pancreases respectively.

METHODS

In the last two decades (2000-2019), significant progress has been made in improving the human islet isolation procedures and in standardizing the use of different tissue dissociation enzyme (TDE; a mixture of collagenase and protease enzymes) blends to recover higher islet yields.

RESULTS AND CONCLUSIONS

This review presents information focusing on properties and role of TDE blends during the islet isolation process, particularly emphasizing on the current developments, associated challenges and future perspectives within the field.

Surface curvature-dependent adsorption and aggregation of fluorescein isothiocyanate on gold nanoparticles

The interaction between metallic nanoparticles and fluorescent molecules and its influence on the optical properties of the particles/molecules have been intensively investigated because of their biology and sensing applications. Here, we studied the adsorption and aggregation of a commonly used dye, fluorescein isothiocyanate (FITC), on gold nanoparticles of various diameters. It was observed that the adsorption of FITC on relatively large gold nanoparticles (≥15 nm in diameter) induced quenching in the two-photon fluorescence (TPF) emission from the FITC molecules, while smaller-sized gold nanoparticles (1.6 nm) had no such effect. This difference was interpreted by the fluorescence resonance energy transfer (FRET) between the FITC molecules and the larger gold nanoparticles. At the same time, it was observed that the ratio of TPF quenching was notably higher than the ratio of the FITC molecules chemically adsorbed on the large gold particles. This unexpected observation revealed that the aggregation-induced fluorescence quenching also contributed significantly to the attenuation of the TPF emission. Time-dependent TPF attenuation during the interaction of FITC and the larger gold nanoparticles was recorded and used to confirm this interpretation. With this experimental evidence, a clear picture of the interaction of the FITC molecules on the gold surface was presented: FITC molecules chemically adsorbed on the small gold nanoparticles. However, the relatively larger surface curvature hindered the aggregation of the FITC molecules on the small gold nanoparticles. On the surface of the larger gold nanoparticles, both adsorption and aggregation occured. The influence of the surface curvature on the interfacial structure of the adsorbed molecules on nanoparticles was discussed.

Fluorescent labeling of ursolic acid with FITC for investigation of its cytotoxic activity using confocal microscopy

Fluorescent labeling is a widely-used approach in the study of intracellular processes. This method is becoming increasingly popular for studying small bioactive molecules of natural origin; it allows us to estimate the vital intracellular changes which occur under their influence. We propose a new approach for visualization of the intracellular distribution of triterpene acids, based on fluorescent labeling by fluoresceine isothiocyanate. As a model compound we took the most widely-used and best-studied acid in the ursane series - ursolic acid, as this enabled us to compare the results obtained during our research with the available data, in order to evaluate the validity of the proposed method. Experimental tracing of the dynamics of penetration and distribution of the labeled ursolic acid has shown that when the acid enters the cell, it initially localizes on the inner membranes where the predicted target Akt1/protein kinase B - a protein that inhibits apoptosis - is located.

Basal filopodia and vascular mechanical stress organize fibronectin into pillars bridging the mesoderm-endoderm gap

Cells may exchange information with other cells and tissues by exerting forces on the extracellular matrix (ECM). Fibronectin (FN) is an important ECM component that forms fibrils through cell contacts and creates directionally biased geometry. Here, we demonstrate that FN is deposited as pillars between widely separated germ layers, namely the somitic mesoderm and the endoderm, in quail embryos. Alongside the FN pillars, long filopodia protrude from the basal surfaces of somite epithelial cells. Loss-of-function of Ena/VASP, α5β1-integrins or talin in the somitic cells abolished the FN pillars, indicating that FN pillar formation is dependent on the basal filopodia through these molecules. The basal filopodia and FN pillars are also necessary for proper somite morphogenesis. We identified a new mechanism contributing to FN pillar formation by focusing on cyclic expansion of adjacent dorsal aorta. Maintenance of the directional alignment of the FN pillars depends on pulsatile blood flow through the dorsal aortae. These results suggest that the FN pillars are specifically established through filopodia-mediated and pulsating force-related mechanisms.

Fluorescein hydrazones: A series of novel non-intercalative topoisomerase IIα catalytic inhibitors induce G1 arrest and apoptosis in breast and colon cancer cells

Fluorescein hydrazones (5 and 7) were synthesized in three/four steps with 82-92% yields. All synthesized compounds were evaluated by topoisomerase I (topo I) and topoisomerase IIα (topo IIα)-mediated relaxation and cell viability assays. Among them, most of the compounds showed topo I & IIα inhibitory activity and nineteen compounds showed strong anti-proliferative activity against various cell lines. In brief, 5e inhibited 53% topo IIα (etoposide 29%) at 20 μM and showed excellent antiproliferative activity against DU145 (1.43 ± 0.04 μM), HCT15 (2.4 ± 0.03 μM) and MCF7 (11.4 ± 0.5 μM) cell lines in comparison with adriamycin, etoposide, and camptothecin. Compounds 5e, 5g and 5h were further evaluated to determine their mode of action. Compounds 5e, 5g and 5h functioned as non-intercalative topo IIα catalytic inhibitor with induction of G1 arrest and activation of apoptotic proteins in dose-dependent manner.

How does fluorescent labeling affect the binding kinetics of proteins with intact cells?

Fluorescent labeling is a mainstream technology for detecting molecular binding. Despite the importance, few studies have been devoted to quantitatively examine the effect of labeling on the molecular binding processes. Here we present a quantitative study on the binding kinetics of fluorescent-labeled and un-labeled molecules (lectin proteins) with glycoproteins on the membrane of cells using surface plasmon resonance imaging (SPRi) technique. The study shows that fluorescent labeling has a significant influence on the binding behaviors of proteins, especially the association processes, and the influence depends sensitively on the charge of fluorescent labels. It further shows that the labels also affect the local distribution of probe proteins, due to the inhomogeneous surface charge distribution of the cell membrane. Our work indicates that fluorescent labeling in general affects the binding behaviors, but proper design of the label will help to minimize its effect.

Fluorescent, bioactive protein nanoparticles (prodots) for rapid, improved cellular uptake

A simple and effective method for synthesizing highly fluorescent, protein-based nanoparticles (Prodots) and their facile uptake into the cytoplasm of cells is described here. Prodots made from bovine serum albumin (nBSA), glucose oxidase (nGO), horseradish peroxidase (nHRP), catalase (nCatalase), and lipase (nLipase) were found to be 15-50 nm wide and have been characterized by gel electrophoresis, transmission electron microscopy (TEM), circular dichroism (CD), fluorescence spectroscopy, dynamic light scattering (DLS), and optical microscopic methods. Data showed that the secondary structure of the protein in Prodots is retained to a significant extent and specific activities of nGO, nHRP, nCatalase, and nLipase were 80%, 70%, 65%, and 50% of their respective unmodified enzyme activities. Calorimetric studies indicated that the denaturation temperatures of nGO and nBSA increased while those of other Prodots remained nearly unchanged, and accelerated storage half-lives of Prodots at 60 °C increased by 4- to 8-fold. Exposure of nGO and nBSA+ nGO to cells indicated rapid uptake within 1-3 h, accompanied by significant blebbing of the plasma membrane, but no uptake has been noted in the absence of nGO. The presence of nGO/glucose in the media facilitated the uptake, and hydrogen peroxide induced membrane permeability could be responsible for this rapid uptake of Prodots. In control studies, FITC alone did not enter the cell, BSA-FITC was not internalized even in the presence of nGO, and there has been no uptake of nBSA-FITC in the absence of nGO. These are the very first examples of very rapid cellular uptake of fluorescent nanoparticles into cells, particularly nanoparticles made from pure proteins. The current approach is a simple and efficient method for the preparation of bioactive, fluorescent protein nanoparticles of controllable size for cellular imaging, and cell uptake is under the control of two separate chemical triggers.

Fluorescein hydrazones as novel nonintercalative topoisomerase catalytic inhibitors with low DNA toxicity

Fluorescein hydrazones (3a-3l) were synthesized in three steps with 86-91% overall yields. Topo I- and IIα-mediated relaxation and cell viability assay were evaluated. 3d inhibited 47% Topo I (camptothecin, 34%) and 20% Topo II (etoposide 24%) at 20 μM. 3l inhibited 61% Topo II (etoposide 24%) at 20 μM. 3d and 3l were further evaluated to determine their mode of action with diverse methods of kDNA decatenation, DNA-Topo cleavage complex, comet, DNA intercalating/unwinding, and Topo IIα-mediated ATP hydrolysis assays. 3d functioned as a nonintercalative dual inhibitor against the catalytic activities of Topo I and Topo IIα. 3l acted as a Topo IIα specific nonintercalative catalytic inhibitor. 3d activated apoptotic proteins as it increased the level of cleaved capase-3 and cleaved PARP in a dose- and time-dependent manner. The dose- and time-dependent increase of G1 phase population was observed by treatment of 3d along with the increase of p27(kip1) and the decrease of cyclin D1 expression.

Matrix composition and mechanics direct proangiogenic signaling from mesenchymal stem cells

The secretion of trophic factors that promote angiogenesis from mesenchymal stem cells (MSCs) is a promising cell-based therapeutic treatment. However, clinical efficacy has proved variable, likely on account of ill-defined cell delivery formulations and the inherent complexity of cellular secretion. Here we show how controlling the mechanical properties and protein composition of the extracellular matrix (ECM) surrounding MSCs can guide proangiogenic signaling. Conditioned media from MSCs adherent to polyacrylamide hydrogel functionalized with fibronectin, collagen I, or laminin was applied to 3D matrigel cultures containing human microvascular endothelial cells (HMVECs). The degree of tubulogenesis in HMVECs is shown to depend on both the substrate rigidity and matrix protein composition. MSCs cultured on fibronectin-modified hydrogels show a stiffness dependence in proangiogenic signaling with maximum influence on tubulogenesis observed from 40 kPa conditioned media, twofold higher than commercially available cocktails of growth factors. Quantitative real-time-polymerase chain reaction reveals stiffness-dependent expression of multiple factors involved in angiogenesis that corroborate the functional tubulogenesis assay. Restricting cell spreading with micropatterned surfaces attenuates the conditioned media effects; however, small-molecule inhibitors of actomyosin contractility do not significantly reduce the functional outcome. This work demonstrates how controlling matrix rigidity and protein composition can influence the secretory profile of MSCs. Model systems that deconstruct the physical and biochemical cues involved in MSC secretion may assist in the design of hydrogel biomaterials for cell-based therapies.

Characterization of the interface between adsorbed fibronectin and human embryonic stem cells

The cell-substrate interface plays a key role in the regulation of cell behaviour. Defining the properties of this interface is particularly important for human embryonic stem (hES) cell culture, because changes in this environment can regulate hES cell differentiation. It has been established that fibronectin-coated surfaces can promote the attachment, growth and maintenance of the undifferentiated phenotype of hES cells. We investigated the influence of the surface density of adsorbed fibronectin on hES cell behaviour in defined serum-free culture conditions and demonstrated that only 25 per cent surface saturation was required to maintain attachment, growth and maintenance of the undifferentiated phenotype. The influence of surface-adsorbed fibronectin fragments was compared with whole fibronectin, and it was demonstrated that the 120 kDa fragment central binding domain alone was able to sustain hES cells in an undifferentiated phenotype in a similar fashion to fibronectin. Furthermore, hES cell attachment to both fibronectin and the 120 kDa fragment was mediated by integrin α5β1. However, although a substrate-attached synthetic arginine-glycine-aspartic acid (RGD) peptide alone was able to promote the attachment and spreading of fibroblasts, it was inactive for hES cells, indicating that stem cells have different requirements in order to attach and spread on the central fibronectin RGD-cell-binding domain. This study provides further information on the characteristics of the cell-substrate interface required to control hES cell behaviour in clearly defined serum-free conditions, which are needed for the development of therapeutic applications of hES cells.

[Recombinant human alpha-fetoprotein as a regulator of adipose tissue stromal cell activity]

Recombinant human alpha-fetoprotein (rhAFP) expressed in yeast system as a glycoprotein, was isolated and purified to 98% by multistep method. The testing of the rhAFP in the culture of adipose tissue stromal cells (hASC) has revealed its ability to enhance hASC proliferation and migration as well as vascular endothelial growth factor production, with no significant influence on cell invasion and matrix metalloproteinase-2 and -9 secretion. It has been also estimated that rhAFP is internalized in hASC via clathrin-dependent mechanism. A study in the murine experimental model of hindlimb ischemia has shown the capability of rhAFP to enhance blood flow recovery. These data suggest that rhAFP is a promising agent for enhancement of the hASC regenerative ability.

Fibronectin layers by matrix-assisted pulsed laser evaporation from saline buffer-based cryogenic targets

The deposition of fibronectin (FN) from saline buffer-based cryogenic targets by matrix-assisted pulsed laser evaporation (MAPLE) onto silicon substrates is reported. A uniform distribution of FN was revealed by Ponceau staining after control experiments on nitrocellulose paper. Well-organized particulates with heights from hundreds of nanometers up to more than 1 μm packed in homogeneous layers were evidenced by optical microscopy and profilometry on Si substrates. Atomic force microscopy images showed regions composed of buffer and FN aggregates forming a compact film. Comparison of infrared spectra of drop-cast and MAPLE-deposited FN confirmed the preservation of composition and showed no degradation of the protein. The protein deposition on Si was confirmed by antibody staining. Small aggregates and fluorescent fibrils were visualized by fluorescence microscopy. Superior attachment of human osteoprogenitor cells cultivated for 3 h proved the presence of stable and intact FN molecules after transfer.

Fibronectin-hyaluronic acid composite hydrogels for three-dimensional endothelial cell culture

Biomaterials that actively promote both wound healing and angiogenesis are of critical importance for many biomedical applications, including tissue engineering. In particular, hyaluronic acid (HA) is an important player that has multiple roles throughout the angiogenic process in the body. Previously, our laboratory has developed photocrosslinkable HA-based scaffolds that promote angiogenesis when implanted in vivo. This paper reports the incorporation of a photocrosslinkable fibronectin (FN) conjugate into three-dimensional (3-D) HA hydrogel networks to enhance endothelial cell adhesion and angiogenesis. The results demonstrate significantly better retention of FN that was photocrosslinked within HA hydrogels compared to FN that was physically adsorbed within HA hydrogels. Increased viability of endothelial cells cultured in 3-D HA hydrogels with photoimmobilized FN, compared to adsorbed FN, was also observed. Endothelial cells were cultured within hydrogels for up to 6 days, a period over which cell proliferation, migration and an angiogenic phenotype were influenced by varying the concentration of incorporated FN. The results demonstrate the potential of these composite hydrogels as biomaterial scaffolds capable of promoting wound healing and angiogenesis.

Labeling of fibronectin by fluorescent and paramagnetic nanoprobes for exploring the extracellular matrix: bioconjugate synthesis optimization and biochemical characterization

In this study, fibronectin-nanoparticles bioconjugates are developed and characterized. Multilabeled nanoparticles are composed of a core of the rare-earth oxide Gd(2)O(3):Tb(3+), capped with a set of Rhodamine B isothiocyanate encapsulated in a silica matrix and functionalized by a carboxylated polyethylene glycol shell. These nanoparticles are stabilized in aqueous solution and are found to contain about 400 carboxyl groups on their surface. Nanoparticle bioconjugation with highly purified human plasma fibronectin (Fn) is mediated by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and N-hydroxysuccinimide, resulting in an amide linkage between the carboxylic acid-terminated surface of the nanoparticle and the primary amine of Fn. The bioconjugation temperature and pH are optimized. The Local structure and global conformation of fibronectin-nanoparticle bioconjugates (FnNP*) are studied by fluorescence spectroscopy and enzymatic sites accessibility. Protein biochemical functionalities are globally conserved, and the protein is actually labeled. Elaboration of such complexes provides a promising bimodal contrasting agent for in vivo imaging.

Functionalization of luminescent aminated particles for facile bioconjugation

For labeling proteins (streptavidin and fibronectin) by luminescent aminated nanoparticles, an interesting strategy that requires neither activation nor chemical pre- or post-treatment was explored. Because biomolecules are easily rendered luminescent after reaction with organic dyes carrying isothiocyanate moiety, phenylene diisothiocyanate (DITC) was used for covalently binding proteins onto luminescent hybrid gadolinium oxide nanoparticles whose ability to combine imaging and therapy was recently demonstrated.

Probing fibronectin-surface interactions: a multitechnique approach

The development of adhesive as well as antiadhesive surfaces is essential in various biomaterial applications. In this study, we have used a multidisciplinary approach that combines biological and physicochemical methods to progress in our understanding of cell-surface interactions. Four model surfaces have been used to investigate fibronectin (Fn) adsorption and the subsequent morphology and adhesion of preosteoblasts. Such experimental conditions lead us to distinguish between anti- and proadhesive substrata. Our results indicate that Fn is not able to induce cell adhesion on antiadhesive materials. On adhesive substrata, Fn did not increase the number of adherent cells but favored their spreading. This work also examined Fn-surface interactions using ELISA immunoassays, fluorescent labeling of Fn, and force spectroscopy with Fn-modified tips. The results provided clear evidence of the advantages and limitations of each technique. All of the techniques confirmed the important adsorption of Fn on proadhesive surfaces for cells. By contrast, antiadhesive substrata for cells avoided Fn adsorption. Furthermore, ELISA experiments enabled us to verify the accessibility of cell binding sites to adsorbed Fn molecules.