Composite chitosan and calcium sulfate scaffold for dual delivery of vancomycin and recombinant human bone morphogenetic protein-2

A biodegradable, composite bone graft, composed of chitosan microspheres embedded in calcium sulfate, was evaluated in vitro for point-of-care loading and delivery of antibiotics and growth factors to prevent infection and stimulate healing in large bone injuries. Microspheres were loaded with rhBMP-2 or vancomycin prior to mixing into calcium sulfate loaded with vancomycin. Composites were evaluated for set time, drug release kinetics, and bacteriostatic/bactericidal activity of released vancomycin, induction of ALP expression by released rhBMP-2, and interaction of drugs on cells. Results showed the composite set in under 36 min and released vancomycin levels that were bactericidal to S. aureus (>MIC 8–16 μg/mL) for 18 days. Composites exhibited a 1 day-delayed release, followed by a continuous release of rhBMP-2 over 6 weeks; ranging from 0.06 to 1.49 ng/mL, and showed a dose dependent release based on initial loading. Released rhBMP-2 levels were, however, too low to induce detectable levels of ALP in W20-17 cells, due to the affinity of rhBMP-2 for calcium-based materials. With stimulating amounts of rhBMP-2 (>50 ng/mL), the ALP response from W-20-17 cells was inhibited when exposed to high vancomycin levels (1,800–3,600 μg/mL). This dual-delivery system is an attractive alternative to single delivery or preloaded systems for bone regeneration since it can simultaneously fight infection and deliver a potent growth factor. Additionally, this composite can accommodate a wide range of therapeutics and thus be customizable for specific patient needs, however, the potential interactive effects of multiple agents must be investigated to ensure that functional activity is not altered.     

Correlates of motorcycle helmet use among recent graduates of a motorcycle training course

Helmets significantly decrease morbidity and mortality from motorcycle crashes, but many areas of the world lack universal helmet laws. To educate motorcyclists in areas without helmet laws, more knowledge of motorcyclists’ helmet beliefs is needed.A web-based survey was therefore designed to assess motorcyclists’ attitudes, norms and behaviors towards helmets in a U.S. state with a limited helmet law. Of 445 survey respondents, 68.4% of respondents reported always wearing a helmet. The not-always-helmeted riders were more likely than the always-helmeted to be male; to bave less education; and to have a history of previous motorcycle crashes and injuries. Although both groups had taken rider training classes, fewer of the not-always-helmeted had learned how to ride in a class. The strongest correlates of being not-always-helmeted (vs. always-helmeted) were attitudes that helmets were not protective and impaired sight/hearing; and the normative belief that they would only wear helmets if forced by law. Because attitudes are often more easily changed than normative beliefs, education may increase helmet use. However, less than half of riders in this state with a mandatory education program learned how to ride from a rider education course, and 44% of non-helmeted said they would only wear a helmet if forced by law. Legislation may therefore be a more efficient and effective strategy than education to increase helmet use.     

Synthesis of hydroxyapatite nanoparticles with tailorable morphologies and carbonate substitutions using a wet precipitation method

Hydroxyapatite (HA) nanoparticles with different morphologies and variant levels of carbonate substitutions were synthesized using a wet precipitation method by adjusting the heating temperature and/or the initial ion concentration of the reaction system. Within the particles, crystalline domains with different lengths were aligned along each other and formed into nanoparticles with different sizes, shapes and topographies. Different from most reported studies, the nucleation, growth and morphology of the crystalline domains were found sensitive to heating temperature, but not significantly influenced by initial ion concentration within the studied range. The OH- and PO4(3-) ions within the HA particles were partially substituted by CO3(2-) ions. The substitution was dominated by the replacement of OH- instead of PO4(3-) in HA. The carbonate substitution was found to decrease with increasing heating temperature and/or initial ion concentration. Therefore, both the morphology and composition of the HA particles can be tailored by controlling the heating temperature and/or the initial ion concentration in the reaction system. Such synthesized HA nanoparticles can be used as biomaterials for bone tissue engineering.     

Dispersive optical solitons by the semi-inverse variational principle

In this paper an analytical expression for an optical soliton is obtained with the aid of He's semi-inverse variational principle in the presence of third- and fourth-order dispersion as well as inter-modal dispersion. Three laws of nonlinear media are considered in this paper: the Kerr law, the power law and the log law.     

Challenges in forming inferences from limited data: a case study of malaria parasite maturation

Inferring biological processes from population dynamics is a common challenge in ecology, particularly when faced with incomplete data. This challenge extends to inferring parasite traits from within-host infection dynamics. We focus on rodent malaria infections (Plasmodium berghei), a system for which previous work inferred an immune-mediated extension in the length of the parasite development cycle within red blood cells. By developing a system of delay-differential equations to describe within-host infection dynamics and simulating data, we demonstrate the potential to obtain biased estimates of parasite (and host) traits when key biological processes are not considered. Despite generating infection dynamics using a fixed parasite developmental cycle length, we find that known sources of measurement bias in parasite stage and abundance data can affect estimates of parasite developmental duration, with stage misclassification driving inferences about extended cycle length. We discuss alternative protocols and statistical methods that can mitigate such misestimation.     

Calibration of multiplexed fiber-optic spectroscopy

Large-scale commercial bioprocesses that manufacture biopharmaceutical products such as monoclonal antibodies generally involve multiple bioreactors operated in parallel. Spectra recorded during in situ monitoring of multiple bioreactors by multiplexed fiber-optic spectroscopies contain not only spectral information of the chemical constituents but also contributions resulting from differences in the optical properties of the probes. Spectra with variations induced by probe differences cannot be efficiently modeled by the commonly used multivariate linear calibration models or effectively removed by popular empirical preprocessing methods. In this study, for the first time, a calibration model is proposed for the analysis of complex spectral data sets arising from multiplexed probes. In the proposed calibration model, the spectral variations introduced by probe differences are explicitly modeled by introducing a multiplicative parameter for each optical probe, and then their detrimental effects are effectively mitigated through a "dual calibration" strategy. The performance of the proposed multiplex calibration model has been tested on two multiplexed spectral data sets (i.e., MIR data of ternary mixtures and NIR data of bioprocesses). Experimental results suggest that the proposed calibration model can effectively mitigate the detrimental effects of probe differences and hence provide much more accurate predictions than commonly used multivariate linear calibration models (such as PLS) with and without empirical data preprocessing methods such as orthogonal signal correction, standard normal variate, or multiplicative signal correction.     

Instrumentation for medium-throughput two-dimensional capillary electrophoresis with laser-induced fluorescence detection

In two-dimensional capillary electrophoresis, a sample undergoes separation in the first dimension capillary by sieving electrophoresis. Fractions are periodically transferred across an interface into a second dimension capillary, where components are further resolved by micellar electrokinetic capillary electrophoresis. Previous instruments employed one pair of capillaries to analyze a single sample. We now report a multiplexed system that allows separation of five samples in parallel. Samples are injected into five first-dimension capillaries, fractions are transferred across an interface to 5 second-dimension capillaries, and analyte is detected by laser-induced fluorescence in a five-capillary sheath-flow cuvette. The instrument produces detection limits of 940 +/- 350 yoctomoles for 3-(2-furoyl)quinoline-2-carboxaldehyde labeled trypsin inhibitor in one-dimensional separation; detection limits degrade by a factor of 3.8 for two-dimensional separations. Two-dimensional capillary electrophoresis expression fingerprints were obtained from homogenates prepared from a lung cancer (A549) cell line, on the basis of capillary sieving electrophoresis (CSE) and micellar electrophoresis capillary chromatography (MECC). An average of 131 spots is resolved with signal-to-noise greater than 10. A Gaussian surface was fit to a set of 20 spots in each electropherogram. The mean spot width, expressed as standard deviation of the Gaussian function, was 2.3 +/- 0.7 transfers in the CSE dimension and 0.46 +/- 0.25 s in the MECC dimension. The standard deviation in spot position was 1.8 +/- 1.2 transfers in the CSE dimension and 0.88 +/- 0.55 s in the MECC dimension. Spot capacity was 300.     

Detection of single bacterial pathogens with semiconductor quantum dots

Semiconductor quantum dots (QDs) have been used in a simple fluorometric assay to detect single cells of the pathogenic Escherichia coli O157:H7 serotype. Composed of CdSe/ZnS core/shell QDs conjugated to streptavidin, this system exhibits 2 orders of magnitude more sensitivity than a similar assay using a common organic dye. Selectivity for this pathogenic bacterial strain over a common lab strain (E. coli DH5alpha), which is gained from the use of specific biotinylated antibodies, is also demonstrated for QD labeling. Under continuous excitation, these QDs retain high fluorescence intensities for hours, whereas a typical organic dye bleaches within seconds, allowing for more rapid and accurate identification of E. coli O157:H7 in single-cell fluorescence-based assays. This indirect QD labeling method, based on antibody-antigen and streptavidin-biotin interactions, is flexible enough to expand to other systems and has great potential for use in simultaneous multicolor detection schemes.     

Comparison of parents with and without disabilities raising teens: Information from the nhis and two national surveys.

Objectives: To contrast families headed by parents with disabilities raising children ages 11-17 years with families headed by parents without disabilities. Study Design: There were 3 sources of data: (a) the National Health Institute Survey (National Center for Health Statistics, 2000), (b) a previous national survey (L. T. T. Barker & V. Maralani, 1997), (c) a new national survey of parents with disabilities (n = 273) and their teens (ages 11-17 years; n = 246) and a control group of parents without disabilities (n = 48) and their teens (n = 37). Main Measure: Participants completed a survey designed for this study. Results: Parents with disabilities were generally quite similar to parents without disabilities, with some notable differences, particularly in employment and income. Deaf parents exhibited certain differences from parents with other disabilities. Conclusion: Survey responses provided a snapshot of parents with disabilities and their families from community samples, including aspects in which disabled and nondisabled participants were similar. (PsycINFO Database Record (c) 2010 APA, all rights reserved)