M. El Fray

New injectable elastomeric biomaterials for hernia repair and their biocompatibility.

Complications associated with implantation of polymeric hernia meshes remain a difficult surgical challenge. We report here on our work, developing for the first time, an injectable viscous material that can be converted to a solid and elastic implant in vivo, thus successfully closing herniated tissue. In this study, long-chain fatty acids were used for the preparation of telechelic macromonomers end-capped with methacrylic functionalities to provide UV curable systems possessing high biocompatibility, good mechanical strength and flexibility. Two different systems, comprising urethane and ester bonds, were synthesized from non-toxic raw materials and then subjected to UV curing after injection of viscous material into the cavity at the abdominal wall during hernioplasty in a rabbit hernia model. No additional fixation or sutures were required. The control group of animals was treated with commercially available polypropylene hernia mesh. The observation period lasted for 28 days. We show here that artificially fabricated defect was healed and no reherniation was observed in the case of the fatty acid derived materials. Importantly, the number of inflammatory cells found in the surrounding tissue was comparable to these found around the standard polypropylene mesh. No inflammatory cells were detected in connective tissues and no sign of necrosis has been observed. Collectively, our results demonstrated that new injectable and photocurable systems can be used for minimally invasive surgical protocols in repair of small hernia defects.

Influence of PEG molecular masses on electrospinning of new multiblock terpoly(ester-ether-ester)s

With the growing progress in tissue engineering, the search for new scaffolding materials has recently intensified considerably. Focusing on this, we synthesized hydrophilic–hydrophobic terpolymers containing poly(ethylene glycol) (PEG) and two different polyester units: butylene terephthalate and butylene linoleate. The spinnability of the materials was verified by the electrospinning process. The influence of different molecular masses of PEG on thermal and mechanical properties as well as on electrospinning of new terpoly(ester-ether-ester) elastomeric materials was investigated. The thermal properties data revealed the crystallization of soft segments in materials containing PEG of high molecular mass (4600 g/mol). Increased crystallinity contributed to increased mechanical properties of terpolymers. We also investigated the effect of the temperature transitions and the degree of crystallinity on the electrospinning process for nanofiber preparation. It was found that polymers containing crystallizable soft segments of PEG4600 are more suitable for electrospinning compared to terpolymers (TEEE) containing PEG1000.

Accuracy Analysis of Measurements in Electrochemical Biosensing

In the paper the results of research on accuracy analysis of measurements in electrochemical biosensing are presented. The scope of performed tests includes EIS (Electrochemical Impedance Spectroscopy) and chronoamperometry, widely used for determination of glucose concentration. Measurement results obtained with two microcontroller systems, designed within a research project, and one reference platform (Autolab system, Metrohm, Netherlands) are compared and discussed. As a result, optimal design solutions may be chosen for microcontroller-based biomeasurement system. In glucosensing, promising results were obtained with the EIS technique in experiments performed using the Autolab system.

Electronic Circuits for Graphene-Based Biosensor

In the paper the results of research on electronic measurement and control systems designed for a multifunctional graphene-based biosensor are presented. Design of different types of biosensing electrodes based on graphene technology is discussed. Development of electronic circuits for read-out of the biosensor signals based on two microcontroller platforms (ATXmega128A1U and STM32F407) is described, including hardware and software design solutions. Comparison of measurement results using both prototype systems in electrochemical biosensing techniques (EIS - Electrochemical Impedance Spectroscopy) is also presented.

Influence of ceria nanoparticles on chemical structure and properties of segmented polyesters.

In this work, we present new nanocomposite materials derived from segmented copolyesters, comprising ethylene terephthalate (PET) segments and dimerized linoleic acid (DLA), and nanometric cerium oxide particles (CeO2). Nanoparticles were incorporated in situ during polycondensation in various concentrations, from 0.1 up to 0.6 wt.%. It was found that preparation of nanocomposites in situ, during polycondensation, had no significant influence on changes in segmental composition as determined from (1)H and (13)C, as well as 2D NMR. Thermal analysis and calculated degree of crystallinity showed that increasing concentration of ceria nanoparticles lead to an increase in mass content of PET crystallites in hard segments. The XRD investigations also showed an increased intensity of characteristic signals with increasing ceria concentration. Simultaneously, the incorporation of CeO2 led to an increase in tensile strength and elongation at break, indicating a reinforcing and plasticizing effect of ceria nanoparticles. However, the modulus at 10% strain decreased with increasing amount of nanoparticles. The in vitro culture of human cardiac progenitor cells (hCPCs) on the new materials indicated a homogenous cell displacement across the samples after 5 days with no signs of cytotoxicity, indicating good biocompatibility in vitro of CeO2-based nanocomposites and a potential for biomedical applications.

Antibiotic loaded microspheres as antimicrobial delivery systems for medical applications

In this paper, we present the preparation and antibiotic loading of polymeric microspheres, composed of copolymers derived from fatty acid/amino acid components, as new polymeric platforms for antibiotic delivery systems. New polymeric materials were used to prepare microspheres with and without immobilized model antibiotics (streptomycin, chloramphenicol and amphotericin B) by a W/O/W double-emulsion/solvent evaporation method, in which chloroform and poly(vinyl alcohol) are used as the solvent and emulsifier, respectively. The antimicrobial activity of the microspheres was tested against Gram-positive S. aureus, Gram-negative E. coli bacteria, and C. albicans, as a representative of a fungus. The new polymeric microspheres are particularly effective carriers for streptomycin, exhibiting antibacterial activity against all tested microorganisms.

Terahertz time-domain spectroscopy characterization of carbon nanostructures embedded in polymer

This work presents results of terahertz time-domain spectroscopy (THz-TDS) investigations of two types of polymer-based nanocomposites, consisting of bulk samples of graphene nanoflakes embedded in a polymer matrix and thin films where single-walled carbon nanotubes (SWCNTs) with a chiral index (7,5) were wrapped in single strains of a polymer. Our THz-TDS setup is a room-temperature system with a frequency range of 0.1 to 3.5 THz, based on photoconductive switches as both the emitter and detector, excited by 100-fs-wide optical pulses. We have studied THz spectra of both types of samples and compared them to the ones obtained for the pure polymer reference specimens and fitted the experimental complex conductivity data to the Drude–Smith model. The Drude–Smith model fits our data well, demonstrating that graphene nanoflakes and SWCNTs, exhibit highly localized intra grain/tube electron backscattering with a femtosecond relaxation time.