Preparation and characterization of polycaprolactone/chitosan-g-polycaprolactone/hydroxyapatite electrospun nanocomposite scaffolds for bone tissue engineering

Chitosan (CS) and poly (ε-caprolactone) (PCL) are two most usable polymers in biomedical applications. In this study, chitosan has been modified and incorporated with poly (ε-caprolactone) to fabricate bone tissue engineering scaffold. Moreover, hydroxyapatite nanoparticles were added to enhance bioactivity and mechanical properties of scaffold. Bulk and fibrous comparative results showed significant effect of fiber diameter and distribution on mechanical properties. Moreover, the incorporation of chitosan-g-poly (ε-caprolactone) (CS-g-PCL) significantly decreases fiber diameter of pure PCL scaffold. Furthermore, both CS-g-PCL and nHA enhance mineralization and degradation of the scaffold soaked in simulated body fluid (SBF) and phosphate buffered saline (PBS), respectively. In vitro cytocompatibility assays also confirmed high cell viability and proliferation on the samples. Taken together, the results suggest that the microfabricated nanocomposite scaffolds could be used in bone tissue engineering.

Crossing statistics of laser light scattered through a nanofluid

In this paper, we investigate the crossing statistics of speckle patterns formed in the Fresnel diffraction region by a laser beam scattering through a nanofluid. We extend zero-crossing statistics to assess the dynamical properties of the nanofluid. According to the joint probability density function of laser beam fluctuation and its time derivative, the theoretical frameworks for Gaussian and non-Gaussian regimes are revisited. We count the number of crossings not only at zero level but also for all available thresholds to determine the average speed of moving particles. Using a probabilistic framework in determining crossing statistics, a priori Gaussianity is not essentially considered; therefore, even in the presence of deviation from Gaussian fluctuation, this modified approach is capable of computing relevant quantities, such as mean value of speed, more precisely. Generalized total crossing, which represents the weighted summation of crossings for all thresholds to quantify small deviation from Gaussian statistics, is introduced. This criterion can also manipulate the contribution of noises and trends to infer reliable physical quantities. The characteristic time scale for having successive crossings at a given threshold is defined. In our experimental setup, we find that increasing sample temperature leads to more consistency between Gaussian and perturbative non-Gaussian predictions. The maximum number of crossings does not necessarily occur at mean level, indicating that we should take into account other levels in addition to zero level to achieve more accurate assessments.