PLGA/Ag nanocomposites: in vitro degradation study and silver ion release.

New nanocomposite films based on a biodegradable poly (DL-Lactide-co-Glycolide) copolymer (PLGA) and different concentration of silver nanoparticles (Ag) were developed by solvent casting. In vitro degradation studies of PLGA/Ag nanocomposites were conducted under physiological conditions, over a 5 week period, and compared to the behaviour of the neat polymer. Furthermore the silver ions (Ag(+)) release upon degradation was monitored to obtain information on the properties of the nanocomposites during the incubation. The obtained results suggest that the PLGA film morphology can be modified introducing a small percentage of silver nanoparticles that do not affect the degradation mechanism of PLGA polymer in the nanocomposite. However results clearly evinced the stabilizing effect of the Ag nanoparticles in the PLGA polymer and the mineralization process induced by the combined effect of silver and nanocomposite surface topography. The Ag(+) release can be controlled by the polymer degradation processes, evidencing a prolonged antibacterial effect.

Micropatterned hydrogenated amorphous carbon guides mesenchymal stem cells towards neuronal differentiation.

This study investigated how the design of surface topography may stimulate stem cell differentiation towards a neural lineage. To this end, hydrogenated amorphous carbon (a-C:H) groove topographies with width/spacing ridges ranging from 80/40µm, 40/30µm and 30/20µm and depth of 24 nm were used as a single mechanotransducer stimulus to generate neural cells from human bone marrow mesenchymal stem cells (hBM-MSCs) in vitro. As comparative experiments, soluble brain-derived neurotrophic factor (BDNF) was used as additional biochemical inducer agent. Despite simultaneous presence of a-C:H micropatterned nanoridges and soluble BDNF resulted in the highest percentage of neuronal-like differentiated cells our findings demonstrate that the surface topography with micropatterned nanoridge width/spacing of 40/30µm (single stimulus) induced hBM-MSCs to acquire neuronal characteristics in the absence of differentiating agents. On the other hand, the alternative a-C:H ridge dimensions tested failed to induce stem cell differentiation towards neuronal properties, thereby suggesting the occurrence of a mechanotransducer effect exerted by optimal nano/microstructure dimensions on the hBM-MSCs responses.

Keratins extracted from Merino wool and Brown Alpaca fibres: thermal, mechanical and biological properties of PLLA based biocomposites.

Keratins extracted from Merino wool (KM) and Brown Alpaca fibres (KA) by sulphitolysis and commercial hydrolyzed keratins (KH) were used as fillers in poly(l-lactic) acid based biocomposites processed by solvent casting in chloroform. Different contents (1 wt.% and 5 wt.%) of keratins were considered and the morphological, thermal, mechanical, chemical and biological behaviours of the developed PLLA biocomposites were investigated. The results confirmed that surface morphologies of biocomposites revealed specific round-like surface topography function of different microsized keratin particles in different weight contents, such as the analysis of bulk morphologies which confirmed a phase adhesion strictly dependent by the keratin source. Transparency and thermal responses were deeply affected by the presence of the different keratins and their interaction with the PLLA matrix. Tensile test results underlined the possibility to modulate the mechanical behaviour of PLLA selecting the keratin type and content in order to influence positively the elastic and/or plastic response. It was demonstrated that surface characteristics of PLLA/KA systems also influenced the bovine serum albumin adsorption, moreover PLLA and PLLA biocomposites based on different kinds of keratins supported the culture of human bone-marrow mesenchymal stem cells, indicating that these biocomposites could be useful materials for medical applications.

Spin coated cellulose nanocrystal/silver nanoparticle films.

In this study, thin films of cellulose nanocrystals (CNC) and silver nanoparticles (Ag) were assembled on different substrates by spin coating. The effect of substrates, deposition parameters, and nanocrystal modification on the topographical and hydrophilic properties of the obtained layers was investigated. Dilute concentrations of pristine cellulose nanocrystals (CNC) and surfactant modified crystals (s-CNC) were used in order to evaluate the effect of modification and concentration on the uniformity of the spin coated cellulose/silver layers. Morphological investigations by field emission scanning electron microscopy and atomic force microscopy were performed in order to prove the uniformity of the obtained films, while the wettability of different surfaces were studied and correlated to the cellulose modification and content. The ability of s-CNC to form a stable dispersion in chloroform permits the formation of a uniform cellulose film on the substrate surfaces generating regular films during the spin coating process. Topographical investigations show, on the other hand, that the CNC/Ag suspension produces a non-uniform distribution. These effects can be mainly attributed to the surfactant action rather than to the chemical and electrical properties of the substrate surface. Finally, contact angle studies, underline the hydrophilic nature of s-CNC/Ag based films highlighting that the wettability properties are strongly influenced by the cellulose nanocrystal nature.

PVA bio-nanocomposites: a new take-off using cellulose nanocrystals and PLGA nanoparticles.

The formation of a new generation of hybrid bio-nanocomposites is reported: these are intended at modulating the mechanical, thermal and biocompatibility properties of the poly(vinyl alcohol) (PVA) by the combination of cellulose nanocrystals (CNC) and poly (D,L-lactide-co-glycolide) (PLGA) nanoparticles (NPs) loaded with bovine serum albumin fluorescein isothiocynate conjugate (FITC-BSA). CNC were synthesized from microcrystalline cellulose by hydrolysis, while PLGA nanoparticles were produced by a double emulsion with subsequent solvent evaporation. Firstly, binary bio-nanocomposites with different CNC amounts were developed in order to select the right content of CNC. Next, ternary PVA/CNC/NPs bio-nanocomposites were developed. The addition of CNC increased the elongation properties without compromising the other mechanical responses. Thermal analysis underlined the nucleation effect of the synergic presence of cellulose and nanoparticles. Remarkably, bio-nanocomposite films are suitable to vehiculate biopolymeric nanoparticles to adult bone marrow mesenchymal stem cells successfully, thus representing a new tool for drug delivery strategies.

Nano-biocomposite films with modified cellulose nanocrystals and synthesized silver nanoparticles.

Ternary nano-biocomposite films based on poly(lactic acid) (PLA) with modified cellulose nanocrystals (s-CNC) and synthesized silver nanoparticles (Ag) have been prepared and characterized. The functionalization of the CNC surface with an acid phosphate ester of ethoxylated nonylphenol favoured its dispersion in the PLA matrix. The positive effects of the addition of cellulose and silver on the PLA barrier properties were confirmed by reductions in the water permeability (WVP) and oxygen transmission rate (OTR) of the films tested. The migration level of all nano-biocomposites in contact with food simulants were below the permitted limits in both non-polar and polar simulants. PLA nano-biocomposites showed a significant antibacterial activity influenced by the Ag content, while composting tests showed that the materials were visibly disintegrated after 15 days with the ternary systems showing the highest rate of disintegration under composting conditions.

Effects of modified cellulose nanocrystals on the barrier and migration properties of PLA nano-biocomposites.

The aim of this paper is to report the impact of the addition of cellulose nanocrystals on the barrier properties and on the migration behaviour of poly(lactic acid), PLA, based nano-biocomposites prepared by the solvent casting method. Their microstructure, crystallinity, barrier and overall migration properties were investigated. Pristine (CNC) and surfactant-modified cellulose nanocrystals (s-CNC) were used, and the effect of the cellulose modification and content in the nano-biocomposites was investigated. The presence of surfactant on the nanocrystal surface favours the dispersion of CNC in the PLA matrix. Electron microscopy analysis shows the good dispersion of s-CNC in the nanoscale with well-defined single crystals indicating that the surfactant allowed a better interaction between the cellulose structures and the PLA matrix. Reductions of 34% in water permeability were obtained for the cast films containing 1 wt.% of s-CNC while good oxygen barrier properties were detected for nano-biocomposites with both 1 wt.% and 5 wt.% of modified and un-modified cellulose nanocrystals, underlining the improvement provided by cellulose on the PLA films. Moreover, the migration level of the studied nano-biocomposites was below the overall migration limits required by the current normative for food packaging materials in both non-polar and polar simulants.

Novel poly(L-lactide) PLLA/SWNTs nanocomposites for biomedical applications: material characterization and biocompatibility evaluation.

Poly(L-lactide) (PLLA)/single-walled carbon nanotubes (SWNTs) nanocomposite films were produced using the solvent casting method, and morphological, thermal and mechanical properties were investigated. Biocompatibility was evaluated by using human bone cells, performing adhesion and proliferation studies. The role of single-walled nanotube incorporation and functionalization on PLLA bio-polymers was investigated. Pristine (SWNTs) and carboxylated (SWNTs-COOH) carbon nanotubes were considered in order to control the interaction between PLLA and nanotubes. SWNTs and SWNTs-COOH showed a good dispersion in the polymer matrix and improved the PLLA crystallinity. Thermal, morphological and dynamic-mechanical analyses revealed that carboxylic groups on the tube sidewalls increased compatibility between PLLA and nanostructures. Mechanical properties demonstrated an enhancement related to introduction and functionalization of carbon nanotubes. Biological investigations showed osteoblasts cultured on PLLA/SWNTs-COOH nanocomposites has higher cell adhesion and proliferation than osteoblasts cultured on PLLA and PLLA/SWNTs nanocomposites. These studies suggest that combination of biodegradable polymers and SWNTs opens a new perspective in the self-assembly of nanomaterials and nanodevices for biomedical applications with tunable properties.