Antibacterial and Biodegradable Polysaccharide-Based Films for Food Packaging Applications: Comparative Study

One of the major objectives of food industry is to develop low-cost biodegradable food packaging films with optimal physicochemical properties, allowing for their large-scale production and providing a variety of applications. To meet the expectations of food industry, we have fabricated a series of solution-cast films based on common biodegradable polysaccharides (starch, chitosan and alginate) to be used in food packaging applications. Selected biopolymers were modified by the addition of glycerol and oxidized sucrose (starch), glycerol (chitosan), and glycerol and calcium chloride (alginate), as well as being used to form blends (starch/chitosan and starch/alginate, respectively). A chestnut extract was used to provide antibacterial properties to the preformed materials. The results of our studies showed that each modification reduced the hydrophilic nature of the polymers, making them more suitable for food packaging applications. In addition, all films exhibited much higher barrier properties to oxygen and carbon dioxide than commercially available films, such as polylactic acid, as well as exhibiting antimicrobial properties against model Gram-negative and Gram-positive bacteria (Escherichia coli and Staphylococcus epidermidis, respectively), as well as yeast (Candida albicans).     

What are the risk factors for complications after combined injury of the pelvic ring and acetabulum?

Purpose

Combined acetabular and pelvic ring injuries represent a unique subset of pelvic trauma and little is known regarding their complications and outcomes. We sought to further evaluate these injury patterns and quantify their outcomes.

Methods

A retrospective review at a single level 1 trauma center was performed on all patients with operatively treated combined ring and acetabulum injuries during a seven-year period. Main outcome measurements include all-cause complication including residual neurologic deficit, deep infection, conversion to total hip arthroplasty, deep venous thrombosis and mortality.

Results

Seventy operatively treated combined ring and acetabulum patients with one-year follow-up were reviewed. The overall complication rate was 44%. Hip dislocation occurred in 40% of the cohort and was significantly associated with residual neurologic deficit and all-cause complication. Angiography with embolization was not associated with an increased rate of deep infection. Open acetabular approaches had a significantly higher complication rate compared to percutaneous procedures. Delay to definitive fixation greater than 36 h trended toward but did not reach association with all complications.

Conclusion

Combined injuries to the acetabulum and pelvic ring have high rates of complications. No individual fracture patterns were identified as risk factors, but hip dislocation was associated with an increased rate of complications. When possible, percutaneous reduction and fixation of acetabular fractures and early definitive fracture fixation lead to lower rates of complications. Use of angiography with embolization appears to be safe and does not increase the risk of infection or other complications.

     

Sustainability of Civil Structures through the Application of Smart Materials: A Review

Every year, structural flaws or breakdowns cause thousands of people to be harmed and cost billions of dollars owing to the limitations of design methods and materials to withstand extreme earthquakes. Since earthquakes have a significant effect on sustainability factors, there is a contradiction between these constraints and the growing need for more sustainable structures. There has been a significant attempt to circumvent these constraints by developing various techniques and materials. One of these viable possibilities is the application of smart structures and materials such as shape memory and piezoelectric materials. Many scholars have examined the use of these materials and their structural characteristics up to this point, but the relationship between sustainability considerations and the deployment of smart materials has received little attention. Therefore, through a review of previous experimental, numerical, and conceptual studies, this paper attempts to draw a more significant relationship between smart materials and structural sustainability. First, the significant impact of seismic events on structural sustainability and its major aspects are described. It is then followed by an overview of the fundamentals of smart material’s behaviour and properties. Finally, after a comprehensive review of the most recent applications of smart materials in structures, the influence of their deployment on sustainability issues is discussed. The findings of this study are intended to assist researchers in properly addressing sustainability considerations in any research and implementation of smart materials by establishing a more explicit relationship between these two concepts.     

Phosphates form spectroscopically dark state assemblies in common aqueous solutions

Phosphates and polyphosphates play ubiquitous roles in biology as integral structural components of cell membranes and bone, or as vehicles of energy storage via adenosine triphosphate and phosphocreatine. The solution phase space of phosphate species appears more complex than previously known. We present nuclear magnetic resonance (NMR) and cryogenic transmission electron microscopy (cryo-TEM) experiments that suggest phosphate species including orthophosphates, pyrophosphates, and adenosine phosphates associate into dynamic assemblies in dilute solutions that are spectroscopically “dark.” Cryo-TEM provides visual evidence of the formation of spherical assemblies tens of nanometers in size, while NMR indicates that a majority population of phosphates remain as unassociated ions in exchange with spectroscopically invisible assemblies. The formation of these assemblies is reversibly and entropically driven by the partial dehydration of phosphate groups, as verified by diffusion-ordered spectroscopy (DOSY), indicating a thermodynamic state of assembly held together by multivalent interactions between the phosphates. Molecular dynamics simulations further corroborate that orthophosphates readily cluster in aqueous solutions. This study presents the surprising discovery that phosphate-containing molecules, ubiquitously present in the biological milieu, can readily form dynamic assemblies under a wide range of commonly used solution conditions, highlighting a hitherto unreported property of phosphate’s native state in biological solutions.

Phosphate-containing species are in constant flux throughout the phosphorus cycle and accumulate within the cells of all living organisms. Cellular energy is primarily harvested through the dynamical formation and breakage of phosphoanhydride chemical bonds of adenosine phosphates (1, 2). Free phosphates and their subsequent assembly are also involved in bone formation and growth (3–5); however, the underlying assembly mechanisms of phosphate species and other ions that lead to bone formation processes are not well understood. An understanding of the equilibrium between free phosphates and higher-order phosphate assemblies in the form of polyphosphates and phosphate clusters would provide further insight into the mechanisms involving biological energy storage and/or the engineering of biological structures.³¹P nuclear magnetic resonance (NMR) offers useful information about the composition, dynamics, and structural properties of lipid membrane interfaces (6–8), phosphorylated biomolecules (9–11), polyphosphates (12, 13), and precursors of bone formation (14). We performed ³¹P NMR to investigate the native state of phosphate species as a function of temperature with the initial intent to subsequently study the formation processes of calcium phosphate clusters. In this process, we encountered peculiar ³¹P NMR line broadening with increasing temperature of aqueous solution of pure phosphates. Such characteristics cannot be explained by the usual temperature-dependent T₂ relaxation due to increasing molecular tumbling of small molecules with increasing temperature. ³¹P NMR line broadening as a function of pH, phosphate concentration, and counter-cation species has been described in the literature (15–17); however, line broadening with increasing temperature has not been reported before.Underscoring these unexpected observations, we present experimental results showing that phosphate-containing species, including orthophosphate, pyrophosphate, and adenosine diphosphate assemble into hitherto unreported spectroscopically “dark” species, whose fractional population increases with increasing temperature. This observation is shown to be consistent with the dehydration entropy-driven formation of dynamic phosphate assemblies. ³¹P NMR chemical exchange saturation transfer (CEST) reveals that phosphates assemble into species with broad spectroscopic signatures, whosepopulation is in exchange with NMR-detectable phosphate species. A subpopulation of these assemblies is also observed in cryogenic transmission electron microscopy (cryo-TEM) images to exhibit droplet-like spherical assemblies up to 50 nm in diameter. The discovery that common phosphate-containing molecules can readily assemble into higher-order species in water under physiological conditions in the absence of biologically activated processes should be relevant to a variety of biological and biochemical processes that use phosphate-containing species as building blocks, energy sources, or reactants in an aqueous environment.     

Biomechanical analysis of a novel femoral neck locking plate for treatment of vertical shear Pauwel's type C femoral neck fractures

BackgroundThe purpose of this study is to determine the biomechanical stability of a novel prototype femoral neck locking plate (FNLP) for treatment of Pauwels type C femoral neck fractures compared with other current fixation methods.MethodsForty femur sawbones were divided into groups and a vertical femoral neck fracture was made. Each group was repaired with one of the following: (CS) three parallel cancellous screws; (XCS) two cancellous lag screws into the head and one transverse lag screw into the calcar; and (FNLP) a novel FNLP with two 5.7 mm locking, one lag screw into the calcar and two screws into the shaft; and (AMBI) a two-hole, 135° AMBI plate with a derotation screw. All groups were tested for change in axial stiffness over 20 000 cycles, and rotational stiffness was measured before and after cyclic testing. A maximum load to failure test was also conducted. Results were compared with one-way analysis of variance (ANOVA) and Fisher protected least significant difference (PLSD).ResultsResults for axial stiffness show that AMBI, CS, XCS and FNLP are 2779.0, 2207.2, 3029.9 and 3210.7 N-m mm^?1, respectively. Rotational rigidity results are 4.5, 4.1, 17.1 and 18.7 N-m mm^?1. The average cyclic displacements were 0.75, 0.88, 0.80 and 0.65 mm, respectively. Destructive failure loads for AMBI, CS, XCS and FNLP were 2.3, 1.7, 1.6 and 1.9 kN, respectively.ConclusionsThe results of this experiment show statistically significant increases in axial stiffness for the FNLP compared with three traditional fixation methods. The FNLP demonstrates increased mechanical stiffness and combines the desirable features of current fixation methods.     

Review: cytokines and malaria.

Malaria, which is caused by hemoprotozoan parasites of the genus Plasmodium, has once again reached epidemic proportions. The resurgence of malaria has occurred because the parasite has developed resistance to the anti-malarial drugs and the mosquito vector has developed resistance to the insecticides. Added to these impediments is the problem that, in spite of intense efforts by researchers world-wide, there is yet no effective anti-malarial vaccine. Our lack of knowledge concerning the exact mechanism of the host immune response to infection with Plasmodium parasites has contributed significantly to the lack of an effective and safe vaccine. The role of an antibody-independent, cell-mediated mechanism which can result in the generation of soluble mediators or cytokines by T lymphocytes and macrophages in host defense against blood stage malaria is being actively investigated in humans and in mice with malaria. With the availability of recombinant lymphokines and monokines and neutralizing antibodies against these reagents it is now possible to determine the role of cytokines in the development of protective anti-malarial immunity. In this review, we discuss recent evidence from human studies and experimental murine models concerning the possible roles of cytokines in malaria.     

Role of interferon-gamma and tumor necrosis factor in host resistance to Plasmodium chabaudi AS

The contribution of the T cell- and macrophage-derived cytokines, interferon-gamma (IFN-gamma) and tumor necrosis factor (TNF), respectively, in the cell-mediated mechanisms leading to acquired immunity to blood-stage Plasmodium chabaudi AS was investigated. To examine the contribution of IFN-gamma, resistant C57BL-derived mice were treated during infection with two different neutralizing, anti-murine IFN-gamma mAbs. Such treatment impaired the ability of the host to limit parasite multiplication just before and at the time of the peak parasitemia but did not abrogate the development of acquired immunity resulting in control and elimination of acute infection. The requirement of endogenous IFN-gamma around the time of the peak parasitemia was confirmed by quantification of IFN-gamma production in vitro by spleen cells from infected animals in response to malaria antigen. To investigate the role of TNF, resistant C57BL/6 and susceptible A/J mice were treated with rTNF during P. chabaudi AS infection. Treatment with 10(3) or 10(5) U rTNF resulted in increased resistance in A/J hosts (that is, increased survival and a less severe course of infection); there was no difference between control and treated C57BL/6 mice in the course of infection but there was increased mortality among the animals treated with rTNF. Splenic macrophages harvested from C57BL/6 mice during infection were found to produce high levels of TNF from day 3 to day 28 post-infection. In conclusion, both IFN-gamma and TNF appear to contribute to host resistance to blood-stage infection with P. chabaudi AS.