Bacterial cellulose: a versatile biopolymer for wound dressing applications

Although several therapeutic approaches are available for wound and burn treatment and much progress has been made in this area, room for improvement still exists, driven by the urgent need of better strategies to accelerate wound healing and recovery, mostly for cases of severe burned patients. Bacterial cellulose (BC) is a biopolymer produced by bacteria with several advantages over vegetal cellulose, such as purity, high porosity, permeability to liquid and gases, elevated water uptake capacity and mechanical robustness. Besides its biocompatibility, BC can be modified in order to acquire antibacterial response and possible local drug delivery features. Due to its intrinsic versatility, BC is the perfect example of a biotechnological response to a clinical problem. In this review, we assess the BC main features and emphasis is given to a specific biomedical application: wound dressings. The production process and the physical–chemical properties that entitle this material to be used as wound dressing namely for burn healing are highlighted. An overview of the most common BC composites and their enhanced properties, in particular physical and biological, is provided, including the different production processes. A particular focus is given to the biochemistry and genetic manipulation of BC. A summary of the current marketed BC-based wound dressing products is presented, and finally, future perspectives for the usage of BC as wound dressing are foreseen.     

Use of morphometric parameters for tracking ovule and microspore evolution in grapevine (<Emphasis Type="Italic">Vitis vinifera</Emphasis> L., cv. “Aragonez”) and evaluation of their potential to improve <Emphasis Type="Italic">in vitro</Emphasis> somatic embryogenesis efficiency from gametophyte tissues

Somatic embryogenesis induction from in vitro cultured stamens and carpels is highly dependent on explants’ inoculation at specific developmental stages. To establish good correlations between measurable morphometric parameters of flowers or flower buds and developmental stages of micro- and macrosporogenesis, this procedure is the easiest way to simplify the in vitro culture procedures. These correlations were established here for the most important Iberian grapevine cultivar, the “Aragonez”, named “Tempranillo” in Spain and “Tinta Roriz” in the north of Portugal, and were based in floral buds and anther measurements. The anther length, with a correlation coefficient of 0.90, proved to be the best morphometric parameter to follow microsporogenesis evolution. A correlation between micro- and macrosporogenesis evolutionary stages was also positively established, allowing the use of morphometric parameters for tracking ovule evolution as well. Carpels in several evolutionary stages were in vitro cultured to evaluate the aging effect on the capacity for somatic embryogenesis induction. Explants inoculated in the earliest stages of macrosporogenesis presented the best results. Media culture formulations were also tested for ovary culture, with the best results being achieved with a 5:1 auxin/cytokinin ratio.     

Work ability of health care shift workers: What matters?

This paper aims at identifying variables associated with inadequate work ability among nursing personnel at a public hospital, considering factors related to socio-demographic, lifestyles, working conditions, and health outcomes. A cross-sectional study was conducted in a university hospital in S?o Paulo, Brazil, as part of a larger research study on tolerance to 12 h night work. Nursing staff included registered nurses, nurse technicians, and nurse aides; in total, there were 996 healthcare workers (878 female; 118 male) at the time of the study. Some 696 workers (69.9%) of the population agreed to participate. Data collection (October 2004-July 2005) was based on a comprehensive questionnaire about living and working conditions (including incivility at work, work demands, work control, and support), mental and physical health symptoms (fatigue and sleep problems), and work ability. This report presents analyses of the adapted Brazilian version of the Work Ability Index (WAI) and associated variables. The study population worked one of the following shift schedules at this hospital: 12 h nights followed by 36 h off or 9 h or 6 h day (morning or afternoon) shifts. The mean age of the respondents was 34.9 (S.D.+/-10.4) years of age; 31.5% of the participants held two jobs. Statistical analyses using a hierarchical multiple logistic regression model were performed to evaluate the factors associated with inadequate (moderate and low scores) of the WAI. The significantly associated factors were socio-demographic (income responsibility, sole breadwinner, raising kids, age group), working conditions (thermal discomfort, organization of the workplace, and verbal abuse), and health outcomes (high body mass index, obesity, sleep problems, and fatigue). In spite of limitations of the study design, results indicate that the nursing profession is associated with stressful working conditions, contributing to inadequate WAI. This is in addition to bad living conditions and precarious work. Intervention measures, either at the workplace or at individual levels, are necessary to prevent a decrease in work ability, even in this quite young working population.     

Mitochondrial respiratory chain complex activity and bioenergetic alterations in human platelets derived from pre-symptomatic and symptomatic Huntington's disease carriers

Mitochondrial dysfunction has been implicated in Huntington's disease (HD) pathogenesis. We analyzed the activity of mitochondrial complexes (Cx) I–IV, protein levels of selected Cx subunits and adenine nucleotides in platelet mitochondria from pre-symptomatic versus symptomatic HD human carriers and age-matched control individuals. Mitochondrial platelets exhibited reduced activity of citrate synthase in pre-symptomatic and Cx-I in pre-symptomatic and symptomatic HD carriers. Positive correlation between Cx activity and protein subunits was observed for Cx-I in symptomatic HD patient's mitochondria. Moreover, AMP increased in mitochondria from pre-symptomatic HD carriers. Results highlight mitochondrial changes occurring before the onset of HD clinical symptoms.     

Developmental trends of theta–beta interelectrode power correlation during resting state in normal children

The possibility that power-to-power (theta–beta) frequency coupling increases during development was analyzed. Three minutes of spontaneous EEG in an open eyes condition were recorded in a sample of 160 subjects ranging from 6 to 26 years old. Theta (4–7 Hz) and beta band (15–20 Hz) power was calculated in a trial-by-trial basis. Inter-electrode power correlations (IPC) were computed in each subject as the correlation between the power of two frequency bands recorded in two electrodes. An increase in theta–beta IPC with age was obtained. IPCs were higher when theta was seeded in posterior regions than in anterior or central regions. Moreover, the significant correlations between each individual IPC and age were calculated, making it possible to draw IPC versus age correlation maps in order to capture the IPC development topography. An increase was found in significant correlations in the left hemisphere compared to the right hemisphere. There were no differences in the inter-hemispheric versus intra-hemispheric IPC maturation spatial patterns. An increase in power-to-power–frequency coupling in theta–beta occurs during development, suggesting an increase in functional connectivity with age. Frequency coupling between theta and beta rhythms would be one of the mechanisms facilitating integration of long distance functional networks during development.     

FLRT3 as a key player on chick limb development

Limb outgrowth is maintained by a specialized group of cells, the apical ectodermal ridge (AER), a thickening of the limb epithelium at its distal tip. It has been shown that fibroblast growth factor (FGF) activity and activation of the Erk pathway are crucial for AER function. Recently, FLRT3, a transmembrane protein able to interact with FGF receptors, has been implicated in the activation of ERK by FGFs. In this study, we show that flrt3 expression is restricted to the AER, co-localizing its expression with fgf8 and pERK activity. Loss-of-function studies have shown that silencing of flrt3 affects the integrity of the AER and, subsequently, its proper function during limb bud outgrowth. Our data also indicate that flrt3 expression is not regulated by FGF activity in the AER, whereas ectopic WNT3A is able to induce flrt3 expression. Overall, our findings show that flrt3 is a key player during chicken limb development, being necessary but not sufficient for proper AER formation and maintenance under the control of BMP and WNT signalling.     

Biocellulose membranes as supports for dermal release of lidocaine

Biocellulose (BC) is a highly pure form of cellulose, produced in the form of a swollen membrane, with several applications in the biomedical area. In this study, the behavior of BC membranes as systems for topical delivery of lidocaine was evaluated. The BC-lidocaine membranes were prepared and characterized in terms of structural and morphological properties. A uniform distribution of the drug inside the BC membranes was observed. In vitro diffusion studies with Franz cells were conducted using human epidermal membranes and showed that the permeation rate of the drug in BC membranes was slightly slower than that obtained with the conventional systems, which was attributed to the establishment of interactions between the lidocaine molecules and the BC membrane, as evidenced by FTIR and NMR analysis. These results indicate that this methodology can be successfully applied for the dermal administration of lidocaine regarding the release profile and ease of application.     

Antimicrobial peptides inhibit polyinosinic-polycytidylic acid-induced immune responses

Viral proteins and nucleic acids stimulate TLRs to elicit production of cytokines, chemokines, and IFNs. Because of their immunostimulatory activity, several TLR agonists are being developed as vaccine adjuvants and cancer immunotherapeutics. However, TLR signaling is modified by disease state, which could enhance or impair therapeutic efficacy. For example, in the skin of psoriasis patients, the human cationic antimicrobial peptide LL37 is highly expressed and binds to host DNA. Association with LL37 enhances DNA uptake into intracellular compartments, where it stimulates TLR9-dependent overproduction of IFNs. Polyinosinic-polycytidylic acid (poly(I:C)), an analog of viral dsRNA, is recognized by TLR3 and is currently in preclinical trials as an inducer of type I IFN. If LL37 similarly enhanced IFN production, use of poly(I:C) might be contraindicated in certain conditions where LL37 is elevated. In this study, we show that TLR3 signaling was not enhanced, but was dramatically inhibited, by LL37 or mouse cathelicidin-related antimicrobial peptide in macrophages, microglial cells, and dendritic cells. Inhibition correlated with formation of a strong complex between antimicrobial peptides and poly(I:C), which partially inhibited poly(I:C) binding to TLR3. Therefore, after injury or during existing acute or chronic inflammation, when LL37 levels are elevated, the therapeutic activity of poly(I:C) will be compromised. Our findings highlight the importance of using caution when therapeutically delivering nucleic acids as immunomodulators.