Hydrophilic polymeric coatings for enhanced, serial-siphon based flow control on centrifugal lab-on-disc platforms

In this paper, we implement rotational flow control on a polymeric microfluidic “lab-on-a-disc” device by combining serial siphoning and capillary valving for sequential release of on-board stored liquid reagents. The functionality of this integrated, multi-step centrifugal assay platform is tightly linked by the capability to establish reproducible, capillary-driven priming of the innately hydrophobic siphon microchannels. We here demonstrate for the first time that spin-coated hydrophilic polymeric films of poly(vinyl alcohol) and (hydroxylpropyl)methylcellulose provide stable contact angles

Fibers for hearts: A critical review on electrospinning for cardiac tissue engineering

Cardiac cell therapy holds a real promise for improving heart function and especially of the chronically failing myocardium. Embedding cells into 3D biodegradable scaffolds may better preserve cell survival and enhance cell engraftment after transplantation, consequently improving cardiac cell therapy compared with direct intramyocardial injection of isolated cells. The primary objective of a scaffold used in tissue engineering is the recreation of the natural 3D environment most suitable for an adequate tissue growth. An important aspect of this commitment is to mimic the fibrillar structure of the extracellular matrix, which provides essential guidance for cell organization, survival, and function. Recent advances in nanotechnology have significantly improved our capacities to mimic the extracellular matrix. Among them, electrospinning is well known for being easy to process and cost effective. Consequently, it is becoming increasingly popular for biomedical applications and it is most definitely the cutting edge technique to make scaffolds that mimic the extracellular matrix for industrial applications. Here, the desirable physico-chemical properties of the electrospun scaffolds for cardiac therapy are described, and polymers are categorized to natural and synthetic.Moreover, the methods used for improving functionalities by providing cells with the necessary chemical cues and a more in vivo- like environment are reported

Silicon micromachined optical sensors for chemical/biological assays

The present doctorate thesis suggests an optoelectronic device, entirely based on silicon, which can incorporate monolithically Mach-Zehnder interferometers advantages, by employing silicon technology. The aim of the thesis is the design, fabrication and characterization of a new integrated optical sensing device for biochemical analysis. The final device consists of the planar Mach-Zehnder interferometer waveguide (MZI), the broad band light source, the detector and the appropriate microfluidic device for the samples supply. The designed and fabricated MZI structure is operational in a broad range of visible-near infrared spectrum and it is the first time that is presented the concept of broad band interferometry (broad-band MZΙ, BB-MZΙ). The broad band spectrum increases the sensitivity of detection. Every wavelength is affected in the sensing arm, due to a binding event or refractive index change generating a phase change. The measurement of interference signal was realized through a monolithically integrated detector (fully-integrated approach) and through an external spectrophotometer (semi-integrated approach). The fully integrated approach can provide the ultimate integration level, while semi-integrated approach can be more sensitive and has the potential to be used for substance fingerprinting. The first step of the thesis involves the theoretical study of the suggested device operation so as to examine the light propagation in the waveguide by using commercial simulation software. Τhe BB-MZI fabrication was realized through monolithic integration of light source and detector to the waveguide. The next step is the sensors development for biochemical specifications. The study and evaluation of successful immobilization of biomolecules onto sensors surface is essential for their detection. The used characterization techniques are white light reflectance spectroscopy and atomic force microscopy. The final step is the biochemical materials deposition onto optoelectronic device sensing arm and their detection. The photocurrent changes (fully-integrated device) as well as the spectral changes (semi-integrated device) observed after the injection of the biochemical materials proved the ability of the fabricated device for detection of ultra thin deposited layers (immobilization of low-concentration biomolecules).Στην παρούσα διδακτορική διατριβή προτείνεται μία οπτοηλεκτρονική διάταξη, βασισμένη εξ ολοκλήρου στο πυρίτιο που ενσωματώνει μονολιθικά τα πλεονεκτήματα των συμβολομέτρων Mach-Zehnder (ΜΖΙ) με τη χρήση της τεχνολογίας πυριτίου. Σκοπός της διατριβής είναι η σχεδίαση, η υλοποίηση και ο χαρακτηρισμός πρωτότυπης ολοκληρωμένης οπτικής αισθητήριας διάταξης για την ανάλυση βιοχημικών δειγμάτων. Η τελική διάταξη αποτελείται από τον επίπεδο κυματοδηγό ΜΖΙ, την πηγή φωτός ευρέως φάσματος, τον ανιχνευτή και την κατάλληλη μικρορρευστομηχανική διάταξη για την παροχέτευση του δείγματος. Η διάταξη ΜΖΙ που σχεδιάστηκε και υλοποιήθηκε είναι λειτουργική σε ευρεία περιοχή του ορατού-εγγύς υπερύθρου φάσματος και είναι η πρώτη φορά που παρουσιάζεται η ιδέα της συμβολομετρίας ευρέως φάσματος (broad-band MZI, BB-MZI). Η χρήση ενός ευρυζωνικού φάσματος αυξάνει την ευαισθησία στην ανίχνευση καθώς κάθε μήκος κύματος «επηρεάζεται» στον αισθητήριο κλάδο παράγοντας μια αλλαγή φάσης. Η καταγραφή του σήματος συμβολής πραγματοποιήθηκε μέσω ενός μονολιθικά κατασκευασμένου ανιχνευτή (πλήρως ολοκληρωμένη εκδοχή) και μέσω ενός εξωτερικού φασματοφωτομέτρου (ημι-ολοκληρωμένη εκδοχή). Η πλήρως ολοκληρωμένη εκδοχή παρέχει το μέγιστο βαθμό ολοκλήρωσης, ενώ με την ημι-ολοκληρωμένη εκδοχή υπάρχει η δυνατότητα ταυτοποίησης ουσιών και μεγαλύτερης ευαισθησίας. Το πρώτο στάδιο της διατριβής περιλαμβάνει τη θεωρητική μελέτη λειτουργίας της διάταξης για τη διερεύνηση της διάδοσης του φωτός μέσα στον κυματοδηγό με τη χρήση ενός εμπορικού λογισμικού προσομοίωσης. Η υλοποίηση του BB-MZI πραγματοποιήθηκε διαμέσου της μονολιθικής ολοκλήρωσης της πηγής φωτός και του ανιχνευτή με τον επίπεδο κυματοδηγό. Το επόμενο στάδιο είναι η ανάπτυξη αισθητήρων για βιοχημικούς προσδιορισμούς. Για την ανίχνευση βιομορίων με τις συγκεκριμένες διατάξεις, αξιολογήθηκε η ακινητοποίησή τους στην επιφάνεια των αισθητήριων διατάξεων. Οι τεχνικές χαρακτηρισμού των επιφανειών που έχουν χρησιμοποιηθεί είναι η συμβολομετρία ανάκλασης λευκού φωτός και η μικροσκοπία ατομικής δύναμης. Το τελευταίο στάδιο είναι η εναπόθεση των βιοχημικών υλικών στον αισθητήριο κλάδο της διάταξης. Οι μεταβολές στην τιμή του φωτορεύματος καθώς και οι φασματικές αλλαγές που καταγράφηκαν με την εισαγωγή των βιοχημικών υλικών απέδειξαν την ικανότητα της κατασκευασθείσας διάταξης για την ανίχνευση των υπέρλεπτων εναποτιθέμενων στοιβάδων (ακινητοποίηση βιομορίων πολύ μικρής συγκέντρωσης)

Modéliser la myopathie myofibrillaire pour élucider la pathogenèse cardiaque

International audienc

Design of functional electrospun scaffolds based on poly(glycerol sebacate) elastomer and poly(lactic acid) for cardiac tissue engineering

International audienceMany works focus on the use of polyesters like poly(lactic acid) (PLA) to produce nanofibrous scaffolds for cardiac tissue engineering. However, such scaffolds are hydrophobic and difficult to functionalize. Here, we show that adding 30% of poly(glycerol sebacate) (PGS) elastomer within PLA leads to PLA:PGS scaffolds with improved biological properties, depending on the processing parameters. Two categories of fibers were produced by blend electrospinning, with diameters of 600 and 1300 nm. The resulting fibers were cured at 90°C or 120°C in order to achieve two different crosslinking densities. The designed scaffolds were considered for cytocompatibility, biocompatibility, biodegradability, chemical and mechanical properties. Our results demonstrated that the presence of PGS increases the hydrophilicity of the material and thus improves surface functionalization by Matrigel and laminin coating, a commonly used cell culture matrix. PLA:PGS scaffolds associated with Matrigel and laminin allow an increased material-cell interaction. Moreover, the cardiomyocytes seeded on such scaffolds acquire a morphology similar to that observed in native tissue, this result being more remarkable on fibers having the smallest diameter and the highest PGS crosslinking density. In addition, these scaffolds induce neovascularization without inflammatory response and foreign body giant cell response after grafting on mice’s heart. Hence, the improved biocompatibility and the ability to support cardiomyocytes development suggest that thin PLA:PGS scaffolds could be promising biomaterials for cardiac application

Surfaces for heart cells:Establishing the optimum plasma surface engineering methodology on polystyrene for cardiac cell engineering

International audiencePlasma surface modification is a popular method for improving cellculture on surfaces, and polystyrene (PS) is literature’s materialof choice. This study identifies the optimum plasma treatment forpromoting normal cardiac cell behaviour during culture. PS slideswere plasma-treated with O2, N2, O2 + N2 and Ar + N2 for 20 and 30min in a reactive ion etcher (RIE). SEM reveals that O2 and O2 + N2plasmas create dual scale roughness, N2 plasma creates oval-shapedstructures, while Ar + N2 exhibits no topography. Evaluation by XPSreveals an increase in the atomic percentage of oxygen for alltreatments. Contact angle measurements agree as all treatments leadto hydrophilisation, with N2 samples exhibiting long-term stability. Two sources of cells were used to identify the optimum plasma treatment for cardiac cell culture on PS. H9c2 cells exhibit optimal ehaviour with N2 and N2 + Ar regarding viability, morphology, and focal adhesion contact. The same was observed for primary cardiomyocytes on N2 samples. For purified cardiomyocytes, immunofluorescence revealed well-organised sarcomeric structure on N2 samples, exhibiting clear improvement compared to control. SEM validated these findings, as cardiomyocytes on N2-treated PS exhibited physiological, elongated shape. These findings provide solid evidence that the optimum treatment for PS is the use of N2 plasma

Spectroscopic and microscopic characterization of biosensor surfaces with protein/amino-organosilane/silicon structure

Composition and structure of biorecognition protein layers created on silicon substrates modified with amino-organosilanes determine the sensitivity and specificity of silicon based biosensing devices. In the present work, diverse spectroscopic and microscopic methods were applied to characterize model biosensor surfaces, formed on Si_{3}N_{4} or SiO_{2} by modification with (3-aminopropyl)triethoxysilane, coating with rabbit gamma-globulins (IgGs) through physical adsorption, blocking with bovine serum albumin (BSA) and specific binding of an anti-rabbit IgG antibody. In addition, silanized substrates with directly adsorbed BSA or anti-rabbit IgG antibody were examined as reference surfaces. The protein/amino-organosilane/silicon structure of all surfaces was confirmed by X-ray photoelectron spectroscopy. Homogeneity of protein coverage was verified with near-field scanning optical microscope, working in reflection and fluorescence mode. Surface coverage with proteins was determined with angle-resolved XPS using a previously established bilayer approach. Inner structure of protein layers was examined with atomic force microscopy. Vertical arrangement of carbon functional groups was revealed by high resolution ARXPS. Combined spectroscopic and microscopic data reveal the complex character of interactions with the immobilized IgG molecules during blocking with BSA and immunoreaction with anti-IgG antibody. Within experimental error, neither surface coverage nor lateral structural scales of protein layer (provided by Fourier and auto-correlation analysis of topographic and phase images) increase during blocking procedure. On the other hand, coverage and all structural measures rise considerably after immunoreaction. In addition, it was found that polar functional groups orient towards substrate for all protein layers, independently of coverage, prior to and after both blocking and specific binding

Cyto- and bio-compatibility assessment of plasma-treated polyvinylidene fluoride scaffolds for cardiac tissue engineering

International audienceAs part of applications dealing with cardiovascular tissue engineering, drop-cast polyvinylidene fluoride (PVDF) scaffolds have been treated by cold plasma to enhance their adherence to cardiac cells. The scaffolds were treated in a dielectric barrier device where cold plasma was generated in a gaseous environment combining a carrier gas (helium or argon) with/without a reactive gas (molecular nitrogen). We show that an Ar-N2 plasma treatment of 10 min results in significant hydrophilization of the scaffolds, with contact angles as low as 52.4° instead of 132.2° for native PVDF scaffolds. Correlation between optical emission spectroscopy and X-ray photoelectron spectroscopy shows that OH radicals from the plasma phase can functionalize the surface scaffolds, resulting in improved wettability. For all plasma-treated PVDF scaffolds, the adhesion and maturation of primary cardiomyocytes is increased, showing a well-organized sarcomeric structure (α-actinin immunostaining). The efficacy of plasma treatment was also supported by real-time PCR analysis to demonstrate an increased expression of the genes related to adhesion and cardiomyocyte function. Finally, the biocompatibility of the PVDF scaffolds was studied in a cardiac environment, after implantation of acellular scaffolds on the surface of the heart of healthy mice. Seven and 28 days after implantation, no exuberant fibrosis and no multinucleated giant cells were visible in the grafted area, hence demonstrating the absence of foreign body reaction and the biocompatibility of these scaffolds