A nanostructured look of collagen apatite porosity into human mineralized collagen fibril

Bone tissue is a hierarchical material characterized at nanoscale by the mineralized collagen fibril,a recurring structure mainly composed of apatite minerals,collagen and water.Bone nanostructure has a fundamental role in determining the mechanical behavior of the tissue and its mass transport properties.Diffusion phenomenon allows to maintain an adequate supply of metabolites in the mechanisms of bone remodeling,adaptation and repair.Several analytical and computational models have been developed to analyze and predict bone tissue behavior.However,the fine replication of the natural tissue still represents a challenge.Insights on the structural organization at nanoscale and on the influence of apatite mineral crystals on the diffusion coefficient lead to outline the functional conditions for the development of biomimetic strategies for bone tissue engineering.Thorough understanding of bone nanostructure is essential to improve longevity of bioscaffolds and to decrease the risk of failure by controlling their mechanical and biological performance.

Fabrication of Self-cleaning Antireflective Polymer Surfaces by Mimicking Underside Leaf Hierarchical Surface Structures

In this work, we utilized underside of four different plant leaves with different scale of hierarchical surface roughness to fabricate large area self-cleaning antireflective polymer surfaces. A simple and precise two-step soft-lithography replica molding technique was deployed by using polydimethylsiloxane (PDMS) polymer as a replicating material. In the first step, a negative PDMS replica was fabricated by using the underside of an original leaf as a template material. In the second step, a positive PDMS replica was fabricated through a negative PDMS replica used as a template. In order to study the non-wetting and light trapping properties, as-replicated polymer surfaces were characterized using Scanning Electron Microscopy (SEM), contact angle goniometer, and UV-Vis spectroscopy. SEM images confirmed the successful replication of complex hierarchical structures while contact angle measurement studies established retaining high non-wetting properties in polymer replicas. Optical studies suggest near zero reflection in normal mode and less than 5% diffuse reflection when measured using integrated sphere mode. These results have been correlated and explained with the air-liquid fraction and roughness factor as measured using three-dimensional optical profilometer.

Dragonfly Inspired Nanocomposite Flapping Wing for Micro Air Vehicles

The current research is aimed towards the development of dragonfly inspired nanocomposite flapping wing for micro air vehicles(MAVs).The wing is designed by taking inspiration from the hind wing of dragonfly(Anax Parthenope Julius).Carbon nanotubes(CNTs)/polypropylene nanocomposite and low-density polyethylene are used as the wing materials.The nanocomposites are developed with varying CNTs'weight percentage(0%-1%)and characterized for dynamic mechanical properties,which revealed that the 0.1 weight percentage case produces highest storage modulus values throughout the frequency range(1 Hz一90 Hz).It is also observed that the storage modulus values are in the range ofYoung^modulus of veins and membrane of natural insect wings.This is useful to achieve true biomimicking.Advanced manufacturing technique such as photolithography is used for wing fabrication.The length,weight and average thickness of the fabricated wing are^44 mm,26.22 mg and 187 pm,respectively.The structural dynamic properties of the fa bricated wing are obtained experimentally and computationally using DIC and ANSYS,respectively.The developed dragonfly inspired wing showed a natural frequency of 29.4 Hz with a bending mode shape which is close to the characteristic frequency of its natural counterpart.

Self-stabilized chitosan and its complexes with carboxymethyl starch as excipients in drug delivery

This study focuses on the behavior of chitosan(CHI)and its polyelectrolyte complexes with carboxymethyl starch(CMS)used as monolithic matrices with acetaminophen as drug tracer.Two different chitosan grades were tested alone or associated in various ratios with CMS as excipients for tablets obtained by direct compression.The degree of deacetylation(DDA)of CHI,estimated from 1H NMR and FTIR data,was correlated with X-ray diffraction and scanning electron microscopy(SEM)to evaluate structural organization of the monolithic matrices.In vitro drug dissolution assays showed major differences in CHI kinetic profiles between tablets exposed to acidic medium for 2h(to mimick gastric passage)prior to dissolution in simulated intestinal fluid(SIF),and those administered directly to SIF.Prior exposure to acidic SGF conducted to longer dissolution profiles(release completed after 16 h)and preservation of tablet shape,whereas tablets directly incubated in SIF were rapidly disintegrated.The improved properties of chitosan matrices exposed to SGF may be related to an outer compact coating layer(visible in SEM).The effect of self-stabilization of chitosan in acidic medium was compared to that due to formation of polyelectrolyte complexes(PEC)in co-processed polymeric systems(CHI:CMS).The self-formed membrane following exposure to gastric acidity appears to help maintaining tablet integrity and allows higher drug loading,recommending CHI and its complexes with CMS as excipients for drug delivery.