Transport of silver nanoparticles from nanocomposite Ag/alginate hydrogels under conditions mimicking tissue implantation

The aim of this work was to assess phenomena occurring during AgNP transport from nanocomposite Ag/alginate hydrogels under conditions relevant for potential biomedical applications as antimicrobial soft tissue implants. First, we have studied AgNP migration from the nanocomposite to the adjacent alginate hydrogel mimicking soft tissue next to the implant. AgNP deposition was carried out by the initial burst release lasting for similar to 24 h yielding large aggregates on hydrogel surfaces and smaller clusters (similar to 400 nm in size) inside. However, the overall released content was low (0.67%) indicating high nanocomposite stability. In the next experimental series, release of AgNPs, 10-30 nm in size, from Ag/alginate microbeads in water was investigated under static conditions as well as under continuous perfusion mimicking vascularized tissues. Mathematical modeling has revealed AgNP release by diffusion under static conditions with the diffusion coefficient within the Ag/alginate hydrogel of 6.9x10(-19) m(2) s(-1). Conversely, continuous perfusion induced increased AgNP release by convection with the interstitial fluid velocity estimated as 4.6 nm s(-1). Overall, the obtained results indicated the influence of hydrodynamic conditions at the implantation site on silver release and potential implant functionality, which should be investigated at the experimentation beginning using appropriate in vitro systems

Production and characterization of non-mineralized and mineralized biomaterials based on seaweed polysaccharides and essential metal zinc

U ovoj tezi je ispitana mogućnost sinteze novih, poboljšanih biomaterijala na bazi alginata, agara i cinka, primenom biomimetičkog principa dizajna – biomineralizacije. Cilj istraživanja je bio dizajn i karakterizacija novih nanokompozitnih biomaterijala, sa potencijalnom primenom u biomedicini i pakovanju hrane...The aim of this study was to test the hypothesis whether biopolymer-based biomineralization, with essential metal salts, Zn-minerals, can be considered a good platform for designing nanocomposite biomaterials for potential biomedical and active food packaging applications..

Longitudinal functional connectivity patterns of the default mode network in healthy older adults

Cross-sectional studies have consistently identified age-associated alterations in default mode network (DMN) functional connectivity (FC). Yet, research on longitudinal trajectories of FC changes of the DMN in healthy aging is less conclusive. For the present study, we used a resting state functional MRI dataset drawn from the Longitudinal Healthy Aging Brain Database Project (LHAB) collected in 5 occasions over a course of 7 years (baseline N = 232, age range: 64-87 y, mean age = 70.85 y). FC strength changes within the DMN and its regions were investigated using a network-based statistical method suitable for the analysis of longitudinal data. The average DMN FC strength remained stable, however, various DMN components showed differential age- and time-related effects. Our results revealed a complex pattern of longitudinal change seen as decreases and increases of FC strength encompassing the majority of DMN regions, while age-related effects were negative and present in select brain areas. These findings testify to the growing importance of longitudinal studies using more sophisticated fine-grained tools needed to highlight the complexity of the functional reorganization of DMN with healthy aging

Object-Location Memory Training in Older Adults Leads to Greater Deactivation of the Dorsal Default Mode Network

Substantial evidence indicates that cognitive training can be efficacious for older adults, but findings regarding training-related brain plasticity have been mixed and vary depending on the imaging modality. Recent years have seen a growth in recognition of the importance of large-scale brain networks on cognition. In particular, task-induced deactivation within the default mode network (DMN) is thought to facilitate externally directed cognition, while aging-related decrements in this neural process are related to reduced cognitive performance. It is not yet clear whether task-induced deactivation within the DMN can be enhanced by cognitive training in the elderly. We previously reported durable cognitive improvements in a sample of healthy older adults (age range = 60-75) who completed 6 weeks of process-based object-location memory training (N = 36) compared to an active control training group (N = 31). The primary aim of the current study is to evaluate whether these cognitive gains are accompanied by training-related changes in task-related DMN deactivation. Given the evidence for heterogeneity of the DMN, we examine task-related activation/deactivation within two separate DMN branches, a ventral branch related to episodic memory and a dorsal branch more closely resembling the canonical DMN. Participants underwent functional magnetic resonance imaging (fMRI) while performing an untrained object-location memory task at four time points before, during, and after the training period. Task-induced (de)activation values were extracted for the ventral and dorsal DMN branches at each time point. Relative to visual fixation baseline: (i) the dorsal DMN was deactivated during the scanner task, while the ventral DMN was activated; (ii) the object-location memory training group exhibited an increase in dorsal DMN deactivation relative to the active control group over the course of training and follow-up; (iii) changes in dorsal DMN deactivation did not correlate with task improvement. These results indicate a training-related enhancement of task-induced deactivation of the dorsal DMN, although the specificity of this improvement to the cognitive task performed in the scanner is not clear

A longitudinal resting-state functional connectivity analysis on trauma exposure and post-traumatic stress symptoms in older individuals

BACKGROUND: Given the present demographic shift towards an aging society, there is an increased need to investigate the brain's functional connectivity in the context of aging. Trauma exposure and post-traumatic stress disorder (PTSD) symptoms are factors known to impact healthy aging and have been reported to be associated with functional connectivity differences. In the present study, we examined and compared differences in within-default mode network (DMN), within-salience network (SN) and between-DMN-SN functional connectivity, between trauma-exposed individuals with and without PTSD symptoms as well as non-traumatized individuals in a non-clininical older adult sample. METHODS: Resting state functional MRI and behavioral data is taken from the Longitudinal Healthy Aging Brain Database Project (LHAB). For the present analysis, participants who completed the questionnaires on trauma exposure and PTSD symptoms (N = 110 individuals of which n = 50 individuals reported previous trauma exposure and n = 25 individuals reported PTSD symptoms; mean age = 70.55 years, SD = 4.82) were included. RESULTS: The reporting of PTSD symptoms relative to no symptoms was associated with lower within-DMN connectivity, while on a trend level trauma-exposed individuals showed higher within-SN connectivity compared to non-trauma exposed individuals. Consistent with existing models of healthy aging, between-DMN-SN functional connectivity showed an increase across time in older age. CONCLUSION: Present results suggest that alterations in within-DMN and within-SN functional connectivity also occur in non-treatment seeking older adult populations with trauma exposure and in association with PTSD symptoms. These changes manifest, alongside altered between-DMN-SN functional connectivity, in older age supposedly independent of aging-related functional desegregation

Mineralized agar-based nanocomposite films: Potential food packaging materials with antimicrobial properties

New mineralized, agar-based nanocomposite films (Zn-carbonate and Zn-phosphate/agar) were produced by a combination of in situ precipitation and a casting method. The presence of minerals significantly influenced the morphology, properties and functionality of the obtained nanocomposites. Reinforcement with the Zn-mineral phase improved the mechanical properties of the carbonate-mineralized films, but had a negligible effect on the phosphate-mineralized samples. Both nanocomposites showed improved optical and thermal properties, better Zn(II) release potential in a slightly acidic environment and exhibited antimicrobial activity against S. aureus. These results suggest that Zn-mineralized agar nanocomposite films could be potentially used as affordable, eco-friendly and active food packaging materials.This is the peer reviewed version of the paper: Malagurski, I., Levic, S., Nesic, A., Mitric, M., Pavlovic, V., & Dimitrijevic-Brankovic, S. (2017). Mineralized agar-based nanocomposite films: Potential food packaging materials with antimicrobial properties. Carbohydrate Polymers, 175, 55–62. [https://doi.org/10.1016/j.carbpol.2017.07.064][https://www.sciencedirect.com/science/article/abs/pii/S0144861717308408?via%3Dihub

Synthesis and antimicrobial properties of Zn-mineralized alginate nanocomposites

New bioactive and antimicrobial biomaterials were produced by alginate-mediated biomineralization with Zn-mineral phase. The synthesis procedure is simple, cost-effective and resulted in. two different Zn-mineralized alginate nanocomposites, Zn-carbonate/Zn-alginate and Zn-phosphate/Zn-alginate. The presence of Zn-mineral phase and its type, have significantly affected nanocomposite morphology, stability, total metallic loading and potential to release Zn(II) in physiological environment. Antimicrobial experiments showed that both types of Zn-mineralized nanocomposites exhibit strong antimicrobial effect against Escherichia coli, Staphylococcus aureus and Candida albicans. These results suggest that alginate biomineralization, where minerals are salts of essential metallic ions like Zn(II), represents a'good strategy for designing multifunctional biomaterials for potential biomedical applications.This is the peer reviewed version of the paper: Malagurski, I., Levic, S., Pantic, M., Matijasevic, D., Mitric, M., Pavlovic, V., & Dimitrijevic-Brankovic, S. (2017). Synthesis and antimicrobial properties of Zn-mineralized alginate nanocomposites. Carbohydrate Polymers, 165, 313–321. [https://doi.org/10.1016/j.carbpol.2017.02.064

Influence of atlas-choice on age and time effects in large-scale brain networks in the context of healthy aging

Introduction: There is accumulating cross-sectional evidence of decreased within-network resting-state functional connectivity (RSFC) and increased between-network RSFC when comparing older to younger samples, but results from longitudinal studies with healthy aging samples are sparse and less consistent. Some of the variability might occur due to differences in network definition and the fact that most atlases were trained on young adult samples. Applying these atlases to older cohorts implies the generalizability of network definitions to older individuals. However, because age is linked to a less segregated network architecture, this assumption might not be valid. To account for this, the Atlas55+ (A55) was recently published. The A55 was trained on a sample of people over the age of 55, making the network solutions suitable for studies on the aging process. Here, we want to compare the A55 to the popular Yeo-Krienen atlas to investigate whether and to what extent differences in network definition influence longitudinal changes of RSFC. For this purpose, the following networks were investigated: the occipital network (ON, “visual network”), the pericentral network (PN, “somatomotor network”), the medial frontoparietal network (M-FPN, “default network”), the lateral frontoparietal network (L-FPN, “control network”), and the midcingulo-insular network (M-CIN, “salience network”). Methods: Analyses were performed using longitudinal data from cognitively healthy older adults (N = 228, mean age at baseline = 70.8 years) with five measurement points over 7 years. To define the five networks, we used different variants of the two atlases. The spatial overlap of the networks was quantified using the dice similarity coefficient (DSC). RSFC trajectories within networks were estimated with latent growth curve models. Models of varying complexity were calculated, ranging from a linear model without interindividual variability in intercept and slope to a quadratic model with variability in intercept and slope. In addition, regressions were calculated in the models to explain the potential variance in the latent factors by baseline age, sex, and education. Finally, the regional homogeneity and the silhouette coefficient were computed, and the spin test and Wilcoxon-Mann-Whitney test were used to evaluate how well the atlases fit the data. Results: Median DSC across all comparisons was 0.67 (range: 0.20–0.93). The spatial overlap was higher for primary processing networks in comparison to higher-order networks and for intra-atlas comparisons versus inter-atlas comparisons. Three networks (ON, PN, M-FPN) showed convergent shapes of trajectories (linear vs. quadratic), whereas the other two networks (L-FPN, M-CIN) showed differences in change over time depending on the atlas used. The 95% confidence intervals of the estimated time and age effects overlapped in most cases, so that differences were mainly evident regarding the p-value. The evaluation of the fit of the atlases to the data indicates that the Yeo-Krienen atlas is more suitable for our dataset, although it was not trained on a sample of older individuals. Conclusions: The atlas choice affects the estimated average RSFC in some networks, which highlights the importance of this methodological decision for future studies and calls for careful interpretation of already published results. Ultimately, there is no standard about how to operationalize networks. However, future studies may use and compare multiple atlases to assess the impact of network definition on outcomes. Ideally, the fit of the atlases to the data should be assessed, and heuristics such as “similar age range” or “frequently used” should be avoided when selecting atlases. Further, the validity of the networks should be evaluated by computing their associations with behavioral measures

Medium chain length (mcl)-pha-based nanocomposites for biomedical applications: system evaluation through xrd

Medium-chain polyhydroxyalkanoates (mcl-PHA) are flexible, elastomeric polymers produced by wide range of bacteria as intercellular storage of carbon and energy. They represent attractive components in biomaterial design because they are biocompatible, biodegradable and can be obtained using variety of carbon sources including waste streams[1]. However, being semi-crystalline, all mcl-PHAs are characterized by low melting temperature and poor tensile strength which can interfere with processing methods and wider biomedical application. Simple way to improve mcl-PHAs properties is to incorporate a nanophase within biopolymer to obtain nanocomposites. Nano-sized constituents interact with biopolymer more intimately affecting in turn the obtained nanocomposite properties as well as functionality. Among inorganic nanofillers, TiO2 nanostructures with high aspect ratio (e.g. nanofibers) have unique properties that support osteogenic phenotype which makes them suitable for bone tissue engineering [2]

UV-blocking sustainable food packaging based on polyhydroxyalkanoate and bacterial pigment prodigiosin

New film materials based on bacterial biomolecules polyhydroxyalkanoate (poly(3- hydroxybutyrate-co-3-hydroxyvalerate) PHBV) and prodigiosin (PG) were produced by solvent casting as a potential food packaging material. Film precursors were obtained in a sustainable manner via microbial fermentation using waste stream-based substrates (cooking oil and second-grade canned meat, after the expiry date). The incorporation of PG into the PHBV has influenced the morphology and functionality of the obtained materials. PG acted as a nucleating agent, affecting in turn PHBV/PG film surface morphology. The films were intensively colored, transparent and blocked UV-light. An increase in PG content decreased film transparency but it did not affect UV-blocking ability. Migration experiments have shown that films possess the potential to release PG into lipophilic food simulant media where it has exhibited antioxidative action. The obtained results suggest that PHBV/PG films can be potentially used as sustainable and active food packaging materials.2nd International Conference on Chemo and BioInformatics, ICCBIKG 2023, September 28-29, 2023 Kragujeva