Application of Biopolymer Doped Polypyrroles in Biomedical Implants and Electrical Stimulation Devices

Organic conductive polymers are emerging new materials for biomedical engineering. They offer surface properties which are attractive for many biomedical applications, such as surface coatings on metallic or biodegradable polymeric implants, tissue engineering scaffolds, implantable electronic tissue stimulation devices and microelectromechanical systems for the manipulation of single living cells in vitro, for example. Owing to the proven compatibility with tissues and cells, conductive polypyrrole (PPy) has been intensively investigated for bone and neural stimulation applications. A salient feature of PPy is its easy modification with bioactive molecules and macromolecules, such as the extracellular matrix (ECM) components of animal tissues. This work assessed the ECM components hyaluronic acid (HA) and chondrointin sulfate (CS) as dopants, which we incorporated into the PPy during the syntheses by electrochemical and oxidative chemical polymerization.Biopolymer doped PPys have been earlier reported to be good substrates for cell cultures. Furthermore, preceding implantation studies have shown promising results. However, considering clinical application and registration of PPy as a biomaterial in commercial cell culturing or tissue engineering products, there are still many practical aspects requiring more attention, such as the establishment of feasible synthetic routes, sterilizability, preservation of the electronic properties during storage and during the incubation in physiological conditions, possible biodegradation mechanisms, stability and biological elimination of the degradation products in vivo, for example. Mass spectroscopy of the hydrolysis products of polylactide (PLA) fibers coated with layer of PPy, suggested that the PPy was biostable in water at neutral pH. Electrical conductivity measurements and Raman spectroscopy showed that the PPy chain was prone to de-doping, and hence the lost its conductivity under biological conditions, but these effects were partly reversible by acid doping and positively biased electrochemical potential. The electrochemical redox activity and electromechanical actuation property of the biopolymer doped PPys was thoroughly studied. It was shown that the biopolymer doped PPy had significant and reversible redox activity, which could be potentially utilized in microelectromechanical stimulation of cells and implantable microscopic actuators.Practical and reproducible polymerization protocols were developed during this work. We took novel approaches and suggested a relatively simple “one-pot” chemical polymerization scheme, avoiding the complications of biological functionalization using potentially toxic click-chemistry. The developed methods were successfully applied in the deposition of electrically conductive, biopolymer doped PPy coatings on polylactide (PLA) nonwoven tissue engineering scaffolds and commercial poly(lactide-co-glycolide)-β-tricalcium phosphate (PLGA-β-TCP) bone fixation screws.The physical properties and cell response of HA and CS doped PPys (PPyHA and PPyCS) electrode coatings were investigated by atomic force microscopy (AFM) and electrochemical methods. Drastically different behaviour of adipose stem cells (hASC) was found on the different electrode coatings, highlighting the sensitity of the hASCs on the nanoscopic and microscopic surface properties of the PPy substrate, such as surface roughness, elasticity and surface potential distribution, factors which could be engineered during the synthesis and affected by external stimuli during incubation in cell culture medium.In conclusion, the resuls of this thesis supported the use of PPy coatings in bone tissue engineering. The electropolymerized films and also the chemically polymerized PPyHA and PPyCS coatings on bioabsorbable polymer were highly compatible with hASCs, supported cell adhesion and could be utilized in delivering direct electrical stimulation in vitro. There is also future potential in designing permanently implantable scaffolds and microstimulation devices, but still further insight into the biodegradation mechanism and biological elimination of PPy in vivo is needed

Pikornavirusten käyttö geenivektoreina ja syöpäterapiassa sekä Coxsackievirus A7 -isolaattien sekvenssianalyysi

Kirjallisessa osassa tarkasteltiin pikornavirusten käyttöä geenivektoreina ja syöpäterapiassa. Pikornavirukset ovat positiivissäikeisiä RNA-viruksia, ja niiden genomi koostuu rakenteellisista kuoriproteiineista VP1-VP4 sekä ei-rakenteellisista proteiineista 2A-2C ja 3A-3D. Geenivektoritutkimukset ovat keskittyneet erilaisten inserttien kloonaamiseen virusten VP1-VP4-alueelle ja genomin 5'-päähän sekä näiden muutosten vaikutusten seuraamiseen virusten elinkierrossa solu- ja hiirimalleissa. Geenivektoreina on parhaiten toimineet coxsackievirukset B3, B4 ja A9 sekä mengo- ja poliovirus. Niitä on käytetty hiirissä mm. neuronien motorisen BDNF-reseptorin ilmentämiseen sekä hiiren interleukiini-10:n tuottamiseen selkäydinkanavan vaurioiden korjaamiseksi. Syöpäterapiatutkimuksissa on saatu lupaavia tuloksia coxsackieviruksilla A21, A13, A15 ja A18 sekä echo-, Seneca Valley 001- ja EMCV-viruksilla. Viruksilla on saatu mm. rintasyövän pääkasvain ja metastasoituneet etäpesäkkeet häviämään sekä eturauhassyövän kasvaimia pienenemään. Seneca Valley 001 -virus on osoittautunut tehokkaaksi syöpiä vastaan, joilla on neuroendokriinisiä ominaisuuksia. Viruksen käyttämistä faasi 2:n kliinisiin kokeisiin ollaan parhaillaan suunnittelemassa pienisoluisen keuhkosyövän ja lasten neuroendokriinisen syövän kohdalla. Kokeellisessa osassa optimoitiin RT-PCR-menetelmä coxsackievirus A7:n (CV-A7) genomin tuottamiseksi PCR-reaktiolla (FL-PCR). FL-PCR:n optimointi tehtiin vektoreilla, joihin oli kloonattu CV-A7-USSR- (USSR-pcDNA3) ja CV-A7-Parkerisolaattien (Parker-TA) genomit. Menetelmää käytettiin myöhemmin muiden CV-A7- virusisolaattien (275/58, ET1080 ja SVK) tutkimiseen. Näistä isolaateista eristettiin virus-RNA, joka käännettiin cDNA:ksi RT-entsyymillä. PCR:ssä käytetyt, CV-A7- spesifiset koettimet oli suunniteltu aiemmin sekvensoidun CV-A7-sekvenssin (GenBank AY421765) pohjalta. Infektiivisen kloonin tuottamiseksi USSR-pcDNA3- ja Parker-TA-vektoreista tuotettiin PCR:n avulla (T7-PCR) virusgenomin sisältävä DNAjakso, jonka 5'-päähän muodostui alukkeiden avulla T7RNA-polymeraasipromoottori ja 3'-päähän polyA-häntä. Työssä myös sekvensoitiin ja analysoitiin CV-A7-virusisolaatit Parker, USSR, 275/58, ET1080 ja SVK sekä kloonattiin täyspitkiä virusgenomeja cDNA-muodossa mutaatiokokeita varten. FL-PCR:n optimointi onnistui, ja neljä viidestä CV-A7-isolaatista sekvensoitiin. Virusgenomien pituus vaihteli 7403–7405 nt:n välillä. CV-A7-ET1080, -Parker ja - USSR osoittautuivat yli 99 % ja CV-A7-275/58 82,6 % nt samankaltaisiksi koko genomin pituudelta AY421765:en suhteen. Yksittäisten geenien ja proteiinien osalta CV-A7-275/58 oli 75,8–90,4 % nt ja 93,7–98,8 % aa samankaltainen muiden suhteen. Simplot-analyysissä 3B-geenialue oli heterogeenisin. CV-A7-SVK-isolaatti osoittautui echovirus kolmeksi. Infektiivistä kloonia ei saatu tuotettua T7-PCR-tuotteista.Siirretty Doriast

Iter Community: Prototyping an Environment for Social Knowledge Creation and Communication

This article focuses on the features and challenges of Iter Community (IC), a new collaborative research environment which aims to aid social knowledge creation for the communities that have formed around Iter’s discovery tools and publication platforms. The underlying vision of IC as a flexible environment for communication, exchange, and collaboration is explained via the history and conceptual framework of IC, preliminary details concerning its infrastructure and features, and a brief examination of the Social Edition of the Devonshire Manuscript as an IC pilot project

Micromechanical performance of high-density polyethylene:experimental and modeling approaches for HDPE and its alumina-nanocomposites

The scratch resistance of polymers is important for numerous applications, as scratching can lead to degradation of surface properties and also represents an elementary process in abrasive wear. However, scratching of polymers is a complex process involving several modes of deformation, and theoretical understanding of it is incomplete. Numerical modeling is a potentially useful means towards a clearer picture of the scratching process, but the central role of tip-substrate contact and highly localized large deformations makes finite element analysis (FEA) challenging. Here, we take further the numerical approach by investigating a highly ductile semi-crystalline polymer by FEA and taking the inherent rate dependency of polymers into account by using an elasto-viscoplastic material model. Two γ-Al2O3 and f-Al2O3 HDPE nanocomposites, which have shown themselves to be suitable for tribological applications, are studied. We discussed the effect of nanofillers on the scratch behavior and highlight the significance of recovery properties, which still pose a challenge to numerical modeling

Evaluation of the performance of self-healing concrete at small and large scale under laboratory conditions

HEALCON is an EU-FP7 project which aims to develop self-healing concrete to create durable and sustainable concrete structures. While during the first years of the project the self-healing materials (including the healing agents and suitable encapsulation methodologies) and monitoring techniques were designed and tested at lab-scale, large scale elements have been tested near the end of the project to verify the feasibility and efficiency of the self-healing concrete under conditions closer to reality. For this paper, two types of healing agents were investigated for use in mortar and concrete. The first type of healing agent studied was a coated superabsorbent polymer (C-SAP). It is known that the autogenous healing capacity is increased by incorporation of superabsorbent polymers (SAPs) in mortar/concrete. The agents present in the crack can absorb intruding water, swell and block the crack, leading to immediate sealing, but can also exude moisture to the surrounding concrete environment stimulating healing of the concrete by hydration of unreacted cement particles or by CaCO3 precipitation. The disadvantage of these SAPs in the fresh mortar/concrete mix is however that they absorb large quantities of mixing water, leading to unwanted effects (e.g. loss of workability and macro-pore formation). By coating of the SAPs, we want to eliminate this disadvantage. The fluid bed spraying of the different layers was applied by VTT. A second healing agent studied, is a biogenic healing agent, namely a Mixed Ureolytic Culture (MUC). This type of healing agent was developed by Avecom in order to reduce the cost associated with the production of pure bacterial strains. This mixed ureolytic culture is moreover self-protecting and does not need any further encapsulation. At first, the performance of the healing agents itself was evaluated. For the coated SAPs, the swelling performance and swelling rate were determined, showing that the coating can limit the uptake of water during the first 10-15 minutes. For the MUC, the ureolytic and CaCO3 precipitating capacity was determined, immediately after production of the MUC and after 3 months of storage. The results show the potential of these mixed cultures to be used as self-healing agent in mortar/concrete, but also show a decrease of their effectiveness with time. Subsequently, the healing agents were incorporated in mortar mixes at UGent. A dosage of 1 wt% relative to the cement content caused a large reduction of the mechanical properties of the mortar (up to ~ 50%), except for the coated SAP. The sealing efficiency was evaluated with the water flow test, as designed by one of the project partners in HEALCON. The performance of reference mixes was compared to that of self-healing mixes with SAP, coated SAP or MUC (+ urea). Results showed that for cracks with a width less than 0.150 mm, all mortars were sealed (almost) completely after storage for 28 days in wet-dry environment (12 h wet – 12 h dry) after crack creation. For cracks with a larger width, differences were noticed between the different specimens. Moreover, also the immediate sealing effect induced by the presence of SAPs could be noticed. It has to be noted however that the crack width plays an important role but is varying along the crack length (within a specimen) and between specimens, making the analysis more difficult. In order to extend the application to concrete, self-healing and reference reinforced concrete beams (2500 x 400 x 200 mm) were produced at the Danish Technological Institute. The self-healing concretes contained coated SAPs or MUC. Moreover, the beams were equipped with corrosion sensors that are connected to a wireless monitoring system, developed by the Technology-Transfer- Initiative at the University of Stuttgart. The multi reference electrodes (MuRE) were installed alongside the reinforcements and measure the corrosion potential at certain positions. Data is collected in sufficiently dense intervals by battery powered nodes that transmit the data wirelessly to a base station and further on to a database where it can be accessed through a web based application for data analysis over the internet. At the age of 28 days, three-point bending cracks up to 0.6 mm were created in the beams. Subsequently, the beams were regularly sprayed with water (four times one hour per day) for 6 weeks and afterwards, the beams were, once a week, exposed to 3 wt% NaCl solution for 24 h. Evaluation of the self-healing performance by microscopic analysis (crack microscopy and analysis of thin sections) showed that for the reference beam and beam with MUC no significant healing could be noticed (probably because of insufficient supply of nutrients for the bacteria). For the beams with coated SAPs, the smaller cracks (0.1 and 0.2 mm) were partly closed. Continuous corrosion monitoring showed corrosion in the reference and MUC beams already after the first exposure to NaCl solution. Onset of corrosion was delayed in the case the beams contained coated SAPs

Association of Cumulative Paternal Early Life Stress With White Matter Maturation in Newborns

This cohort study examines infants and parents in the FinnBrain Birth Cohort to assess the association between paternal cumulative early life stress and offspring brain development.Question Is there an association between paternal early life stress exposure and newborn offspring brain development? Findings In the FinnBrain Birth Cohort study, among 72 trios of infants and their parents, a statistically significant association was found between paternal cumulative early life stress and child brain development, which persisted after controlling for several maternal variables. Meaning These data suggest an intergenerational mode of inheritance of offspring brain development; this finding may have implications for pediatric neuropsychiatric disorders.Importance Early life stress (ELS) has been shown to affect brain development and health outcomes. Recent animal studies have linked paternal early stress exposures with next-generation outcomes. Epigenetic inheritance through the male germline has been suggested to be one of the mechanisms. Objectives To test whether paternal ELS, as measured using the Trauma and Distress Scale, is associated with neonate brain development. Design, Setting, and Participants This cohort study included data from participants from the prospective 2-generation FinnBrain Birth Cohort, which was collected from 2011 to 2015. Pregnant women and the fathers were consecutively recruited at gestational week 12 from maternity clinics in Finland. Magnetic resonance imaging data were analyzed in 2019. Participants in this study were 72 families (infant, father, mother). Exposure Paternal exposure to ELS. Main Outcomes and Measures Fractional anisotropy (FA) values in the major white-matter tracts of the newborn brain. Results A total of 72 trios (infant, mother, and father) were analyzed. At the time of delivery, the mean (SD) age was 31.0 (4.4) years for fathers and 30.3 (4.5) years for mothers. Forty-one infants (57%) were boys; mean (SD) child age at inclusion was 26.9 (7.2) days from birth and 205 (8) days from estimated conception. Increasing levels of paternal ELS were associated with higher FA values in the newborn brain in the body of the corpus callosum, right superior corona radiata, and retrolenticular parts of the internal capsule. This association persisted after controlling for maternal ELS, maternal socioeconomic status (SES), maternal body mass index, maternal depressive symptoms during pregnancy, child sex, and child age from birth and gestation corrected age when imaged. In additional region-of-interest analyses, the association between FA values and paternal Trauma and Distress Scale sum scores remained statistically significant in the earliest maturing regions of the brain, eg, the genu of the corpus callosum (in the regression models, beta = 0.00096; 95% CI, 0.00034-0.00158; P = .003) and the splenium (beta = 0.00090; 95% CI, 0.00000-0.00180; P = .049). Conclusions and Relevance This cohort study found a statistically significant association between paternal ELS and offspring brain development. This finding may have far-reaching implications in pediatrics, as it suggests the possibility of a novel route of intergenerational inheritance of ELS on next-generation brain development

Sex-specific associations between maternal pregnancy-specific anxiety and newborn amygdalar volumes-preliminary findings from the FinnBrain Birth Cohort Study

Previous literature links maternal pregnancy-specific anxiety (PSA) with later difficulties in child emotional and social cognition as well as memory, functions closely related to the amygdala and the hippocampus. Some evidence also suggests that PSA affects child amygdalar volumes in a sex-dependent way. However, no studies investigating the associations between PSA and newborn amygdalar and hippocampal volumes have been reported. We investigated the associations between PSA and newborn amygdalar and hippocampal volumes and whether associations are sex-specific in 122 healthy newborns (68 males/54 females) scanned at 2-5 weeks postpartum. PSA was measured at gestational week 24 with the Pregnancy-Related Anxiety Questionnaire Revised 2 (PRAQ-R2). The associations were analyzed with linear regression controlling for confounding variables. PSA was associated positively with left amygdalar volume in girls, but no significant main effect was found in the whole group or in boys. No significant main or sex-specific effect was found for hippocampal volumes. Although this was an exploratory study, the findings suggest a sexually dimorphic association of mid-pregnancy PSA with newborn amygdalar volumes

Newborn white matter microstructure moderates the association between maternal postpartum depressive symptoms and infant negative reactivity

Maternal postpartum depression is a prominent risk factor for aberrant child socioemotional development, but there is little understanding about the neural phenotypes that underlie infant sensitivity to maternal depression. We examined whether newborn white matter fractional anisotropy (FA), a measure of white matter maturity, moderates the association between maternal postpartum depressive symptoms and infant negative reactivity at 6 months. Participants were 80 mother–infant dyads participating in a prospective population-based cohort, and included families whose newborns underwent a magnetic resonance/diffusion tensor imaging scan at 2–5 weeks of age and whose mothers reported their own depressive symptoms at 3 and 6 months postpartum and infant negative emotional reactivity at 6 months. The whole-brain FA moderated the association between maternal depressive symptoms and mother-reported infant negative reactivity at 6 months after adjusting for the covariates. Maternal depressive symptoms were positively related to infant negative reactivity among infants with high or average FA in the whole brain and in corpus callosum and cingulum, but not among those with low FA. The link between maternal depressive symptoms and infant negative reactivity was moderated by newborn FA. The variation in white matter microstructure might play a role in child susceptibility to parental distress.</p