Freely Suspended Cellular “Backpacks” Lead to Cell Aggregate Self-Assembly

Cellular “backpacks” are a new type of anisotropic, nanoscale thickness microparticle that may be attached to the surface of living cells creating a “bio-hybrid” material. Previous work has shown that these backpacks do not impair cell viability or native functions such as migration in a B and T cell line, respectively. In the current work, we show that backpacks, when added to a cell suspension, assemble cells into aggregates of reproducible size. We investigate the efficiency of backpack−cell binding using flow cytometry and laser diffraction, examine the influence of backpack diameter on aggregate size, and show that even when cell−backpack complexes are forced through small pores, backpacks are not removed from the surfaces of cells.National Science Foundation (U.S.). Materials Research Science and Engineering Centers (Program) (Award DMR-08-19762)National Science Foundation (U.S.) (Graduate Research Fellowship)United States. Dept. of DefenseUnited States. Air Force Office of Scientific ResearchHoward Hughes Medical Institute (Investigator)United States. Dept. of Defense (National Defense Science and Engineering Graduate Fellowship 32 CFR 168a

Compact Polyelectrolyte Complexes: “Saloplastic” Candidates for Biomaterials

Precipitates of polyelectrolyte complexes were transformed into rugged shapes suitable for bioimplants by ultracentrifugation in the presence of high salt concentration. Salt ions dope the complex, creating a softer material with viscous fluid-like properties. Complexes that were compacted under the centrifugal field (CoPECs) were made from poly(diallyldimethyl ammonium), PDADMA, as polycation, and poly(styrene sulfonate), PSS, or poly(methacrylic acid), PMAA, as polyanion. Dynamic mechanical testing revealed a rubbery plateau at lower frequencies for PSS/PDADMA with moduli that decreased with increasing salt concentration, as internal ion pair cross-links were broken. CoPECs had significantly lower modulii compared to similar polyelectrolyte complexes prepared by the “multilayering ” method. The difference in mechanical properties was ascribed to higher water content (located in micropores) for the former and, more importantly, to their nonstoichiometric polymer composition. The modulus of PMAA/PDADMA CoPECs, under physiological conditions, demonstrated dynamic mechanical properties that were close to those of the nucleus pulposus in an intervertebral disk

A new MRI rating scale for progressive supranuclear palsy and multiple system atrophy: validity and reliability

AIM To evaluate a standardised MRI acquisition protocol and a new image rating scale for disease severity in patients with progressive supranuclear palsy (PSP) and multiple systems atrophy (MSA) in a large multicentre study. METHODS The MRI protocol consisted of two-dimensional sagittal and axial T1, axial PD, and axial and coronal T2 weighted acquisitions. The 32 item ordinal scale evaluated abnormalities within the basal ganglia and posterior fossa, blind to diagnosis. Among 760 patients in the study population (PSP = 362, MSA = 398), 627 had per protocol images (PSP = 297, MSA = 330). Intra-rater (n = 60) and inter-rater (n = 555) reliability were assessed through Cohen's statistic, and scale structure through principal component analysis (PCA) (n = 441). Internal consistency and reliability were checked. Discriminant and predictive validity of extracted factors and total scores were tested for disease severity as per clinical diagnosis. RESULTS Intra-rater and inter-rater reliability were acceptable for 25 (78%) of the items scored (≥ 0.41). PCA revealed four meaningful clusters of covarying parameters (factor (F) F1: brainstem and cerebellum; F2: midbrain; F3: putamen; F4: other basal ganglia) with good to excellent internal consistency (Cronbach α 0.75-0.93) and moderate to excellent reliability (intraclass coefficient: F1: 0.92; F2: 0.79; F3: 0.71; F4: 0.49). The total score significantly discriminated for disease severity or diagnosis; factorial scores differentially discriminated for disease severity according to diagnosis (PSP: F1-F2; MSA: F2-F3). The total score was significantly related to survival in PSP (p<0.0007) or MSA (p<0.0005), indicating good predictive validity. CONCLUSIONS The scale is suitable for use in the context of multicentre studies and can reliably and consistently measure MRI abnormalities in PSP and MSA. Clinical Trial Registration Number The study protocol was filed in the open clinical trial registry (http://www.clinicaltrials.gov) with ID No NCT00211224

MODELING OF REGIONS OF ASTEROID POSSIBLE MOTION

Peculiar properties of construction of initial regions of asteroids' possible motion from observational data in the form of probabilistic ellipsoids are investigated. For the objects which observed only in one appearance, this problem may be essentially nonlinear, and the usual method for their construction with the help of linear estimations of covariance matrices may became unacceptable. In order to make possible application of the linear estimation methods which has been developing in mathematical statistics the problem of decreasing nonlinearity is discussed. The solution of this problem with the help of appropriate system of initial parameters of asteroid orbits choice, as well as initial time and weighting matrices of observational errors is proposed. Efficiency of such technique had justified by numerical experiments with the usage of model and real observations

APPLICATION OF ATOMIC-FORCE MICROSCOPY FOR THE EXAMINATION OF THE TOOTH ENAMEL SURFACE

The article presents the results of the study of the tooth enamel surface using atomic force microscopy. The aim of the study – application of atomic force microscopy to study the topography of the surface of a normal tooth enamel. Materials and Methods. For conducting atomic force microscopy, samples of a mature tooth enamel of nine third molars were prepared without any disease of hard tissues. Teeth for making enamel samples were taken after their extraction. The extracted teeth were treated with a 13 % solution of hydrogen peroxide, washed thoroughly with distilled water, dried. The bruccal surface of the enamel was cut into samples using a diamond disc. Topological images of the surface of samples of the tooth enamel were obtained using the Solver P47-PRO (NT -MDT ) atomic force microscope in a semi-contact mode with a 1Hz sweep rate. The probe gages NSG 10-A with a radius of curvature of the tip of 10 nm were used. As a result, a number of images of the enamel surface of different scales and a resolution of 256 × 256 points were obtained. Results and Discussion. It is established that the surface relief of the enamel is particularly well seen in the images of 1 × 1 μm sections, which is explained by the multiplicity of magnification. The results of the profile studies indicate that the enamel prisms are not of the same size and that for a healthy enamel, the minimum height differences are typical. The average square surface roughness of the enamel in the samples was 25.6 nm on average, with an average height of 115 nm enamel on a segment 2.5 × 2.5 microns. Conclusions. The application of atomic force microscopy allows us to evaluate such characteristics of the surface of the enamel as: a three-dimensional image of the surface relief, the determination of the geometrical dimensions of enamel prisms, the calculation of the average height of enamel prisms and the average square surface roughness, that opens up new possibilities in research the state of surface of the tooth enamel, study of its structure, morphology and surface parameters calculation